This section describes physical, oceanographic, and climatic features in greater Puget Sound that may contribute to isolation between populations of the three rockfish species considered in this status review. This section further provides a basis for identifying climatic and biological factors that may contribute to extinction risk for these species. The following summary primarily considers the marine waters of greater Puget Sound that lie south of the boundary between Canada and the United States. However, because the three rockfish species are also found in the Strait of Georgia, a brief description of this system will also be presented. Greater Puget Sound is a fjord-like estuary located in northwest Washington State and covers an area of about 2,330 km2, including 3,700 km of coastline. It is subdivided into five basins or regions: 1) North Puget Sound, 2) Main Basin, 3) Whidbey Basin, 4) South Puget Sound, and 5) Hood Canal Numbers 2-5 in Puget Sound proper (Fig. 5). The average depth of greater Puget Sound is 62.5 m at mean low tide, and the average surface water temperature is 12.8oC in summer and 7.2oC in winter (Staubitz et al. 1997). Estuarine circulation in greater Puget Sound is driven by tides, gravitational forces, and freshwater inflows. For example, the average daily difference between high and low tide varies from 2.4 m at the northern end of greater Puget Sound to 4.6 m at its southern end. Tidal oscillations substantially reduce the flushing rate of nutrients and contaminants. Concentrations of nutrients (i.e., nitrates and phosphates) are consistently high throughout most of the greater Puget Sound, largely due to the flux of oceanic water into the basin (Harrison et al. 1994). The freshwater inflow into greater Puget Sound is about 900 million gallons/day (gpd) (3.4 trillion liters /day). The major sources of freshwater are the Skagit and Snohomish Rivers located in Whidbey Basin (Table 1). However, the annual amount of freshwater entering Puget Sound is only 10 to 20% of the amount entering the Strait of Georgia, primarily through the Fraser River. The Fraser River has a drainage area of 234,000 km2 (Bocking 1997). The rate of flow in the Fraser River ranges from an average of 750 m3/sec in the winter to an average of 11,500 m3/sec during the spring freshet, although, flows of 20,000 m3/sec are not uncommon during the spring floods (Bocking 1997).
Eight major habitats occur in greater Puget Sound (Levings and Thom 1994). Kelp beds and eelgrass meadows cover the largest area (Figs. 6 and 7), almost 1000 km2. Other major habitats include subaerial and intertidal wetlands (176 km2), and mudflats and sandflats (246 km2). The extent of some of these habitats have markedly declined over the last century. Hutchinson (1988) indicated that overall losses since European settlement, by area, of intertidal habitat were 58% for greater Puget Sound and 18% for the Strait of Georgia. Four river deltas (the Duwamish, Lummi, Puyallup, and Samish) have lost greater than 92% of their intertidal marshes (Simenstad et al. 1982, Schmitt et al. 1994). At least 76% of the wetlands around greater Puget Sound have been eliminated, especially in urbanized estuaries. Substantial declines of mudflats and sandflats have also occurred in the deltas of these estuaries (Levings and Thom 1994). The human population in the greater Puget Sound region is estimated to be about 3.6 million.
The greater Puget Sound Basin falls within the Puget Lowland, a portion of a low-lying area extending from the lower Fraser River Valley southward to the Willamette Lowland (Burns 1985). In the distant past, the Puget Lowland was drained by numerous small rivers that flowed northward from the Cascade and Olympic mountains and emptied into an earlier configuration of the Strait of Juan de Fuca. During the Pleistocene, massive Piedmont glaciers, as much as 1,100 m thick, moved southward from the Coast Mountains of British Columbia and carved out the Strait of Juan de Fuca and greater Puget Sound. The deepest basins were created in North Puget Sound in and around the San Juan Islands. About 15,000 years ago, the southern tongue of the last glacier receded rapidly leaving the lowland covered with glacial deposits and glacial lakes, and revealing the Puget Sound Basin (Burns 1985). The large glacially-formed troughs of Puget Sound were initially occupied by large proglacial lakes that drained southward (Thorson 1980). Almost two dozen deltas were developed in these lakes as the result of streams flowing from the melting ice margins.
Considerable evidence indicates that climate in the greater Puget Sound region is cyclical, with maxima (warm, dry periods) and minima (cold, wet periods) occurring at decadal intervals. For example, according to the Pacific Northwest Index (PNI), since 1893 there have been about five minima and four maxima (Ebbesmeyer and Strickland 1995). Three minima occurred between 1893 and 1920, one between the mid-1940s and 1960, and one between the mid-1960s and mid-1970s. Two maxima occurred between the early-1920s and the early-1940s, and two more occurred between the late-1970s and 1997.
Mantua et al. (1997) and Hare and Mantua (2000) evaluated relationships between interdecadal climate variability and fluctuations in the abundance and distribution of marine biota. These authors used statistical methods to identify the Pacific Decadal Oscillation (PDO). The PDO shows predominantly positive epochs between 1925 and 1946 and following 1977, and a negative epoch between 1947 and 1976 (Fig. 8). For Washington State, positive epochs are characterized by increased flow of relatively warm-humid air and less than normal precipitation, and the negative epochs correspond to a cool-wet climate. Mantua et al. (1997) reported connections between the PDO and indicators of populations of Alaskan sockeye and pink salmon and Washington-Oregon-California coho and chinook salmon, although the coho and chinook populations were highest during the negative epochs. Hare and Mantua (2000) found evidence for major ecological and climate changes for the decade following 1977 (a positive epoch) (Fig. 8). They also found less powerful evidence of a climate regime shift (a negative epoch) following 1989, demonstrated primarily by ecological changes. Examples of ecological parameters, that were correlated with these decadal changes, included annual catches of Alaskan coho and sockeye salmon, annual catches of Washington and Oregon coho and chinook salmon, biomass of zooplankton in the California Current, and the Oyster Condition Index for oysters in Willapa Bay, Washington (Hare and Mantua, in press).
Few climatological records are available prior to the 1890s. Proxy measures of climatic variation have been used to reconstruct temperature fluctuations in the Pacific Northwest. Graumlich and Brubaker (1986) reported correlations between annual growth records for larch and hemlock trees located near Mt. Rainier and temperature and snow depth. A regression model was used to reconstruct temperatures from 1590 to 1913. Their major findings were that temperatures prior to 1900 were approximately 1oC lower than those of the 1900s, and that only the temperature pattern in the late-1600s resembled that of the 1900s.
Bathymetry and geomorphology—The North Puget Sound region is demarcated to the north by the U.S.-Canadian border, to the west by a line due north of the Sekiu River, to the south by the Olympic Peninsula, and to the east by a line between Point Wilson (near Port Townsend) and Partridge Point on Whidbey Island and the mainland between Anacortes and Blaine, Washington (Fig. 5). The predominant feature of the North Sound is the Strait of Juan de Fuca, which is 160 km long, and 22 km wide at its western end to over 40 km at its eastern end (Thomson 1994).
One of the deepest sections of this region is near the western mouth (about 200 m) (Holbrook et al. 1980), whereas the deepest sections of eastern portions are located northwest of the San Juan Islands (340-380 m) (Puget Sound Water Quality Action [PSWQA] 1987). Subtidal depths range from 20 to 60 m in most of the northwest part of the region. Deeper areas near the entrance to the Main Basin north of Admiralty Inlet range from 120 to 180 m in depth (PSWQA 1987).
Most of the rocky-reef habitat in greater Puget Sound is located in this region. Pacunski and Palsson (1998) estimated that about 200 km² of rocky-reef habitat was present in these shallow habitats (38 m or less), whereas only about 14 km² was found in the remaining Puget Sound proper basins. Several rockfish species, including copper and quillback rockfish prefer rocky-reef habitats (Pacunski and Palsson 1998).
Sediment characteristics—The surface sediment of the Strait of Juan de Fuca is composed primarily of sand, which tends to be coarser, including some gravel, toward the eastern portion of North Sound and gradually becomes finer towards the mouth (Anderson 1968). Many of the bays and sounds in the eastern portion of the North Sound have subtidal surface sediments consisting of mud or mixtures of mud and sand (PSWQA 1987, WDOE 1998). The area just north of Admiralty Inlet is primarily gravel in its deeper portions, and a mixture of sand and gravel in its shallower portions, whereas the shallow areas north of the inlet on the western side of Whidbey Island and east of Protection Island consist of muddy-sand (Roberts 1979). The majority of the subtidal surface sediments among the San Juan Islands consist of mixtures of mud and sand. Within the intertidal zone, 61.2 ± 49.7% of the area also has mixed fine sediment and 22.6 ± 27.5% has sandy sediment (Bailey et al. 1998).
Currents and tidal activity—The Strait of Juan de Fuca is a weakly stratified, positive estuary with strong tidal currents (Thomson 1994). The western end of the Strait is strongly influenced by ocean processes, whereas the eastern end is influenced by intense tidal action occurring through and near the entrances to numerous narrow passages which results in vigorous vertical mixing (Ebbesmeyer et al. 1984) (Figs. 9a, 9b). Seasonal variability in temperature and salinity is small because the waters are vertically well-mixed (Thomson 1994). On average, freshwater runoff makes up about 7% of the water by volume in the Strait and is derived primarily from the Fraser River. Generally, the circulation in the Strait consists of seaward surface flow of diluted seawater (<30.0‰) in the upper layer and an inshore flow of saline oceanic water (>33.0‰) at depth (Thomson 1994, Collias et al. 1974). Exceptions include an easterly flow of surface waters near the shoreline between Port Angeles and Dungeness Spit (Fig. 10), landward flows of surface waters in many of the embayments and passages, and flows of surface water southward toward the Main Basin near Admiralty Inlet (PSWQA 1987).
Water quality—Temperatures generally range between 7o and 11oC, although occasionally surface temperatures reach as high as 14oC (WDOE 1999). In the eastern portion of North Sound, temperature and salinity vary from north to south, with the waters in the Strait of Georgia being slightly warmer than the waters near Admiralty Inlet. Waters near Admiralty Inlet also tended to have a higher salinities than waters to the north (WDOE 1999). Dissolved oxygen levels vary seasonally, with lowest levels of about 4 mg/L at depth during the summer months, and highest levels of about 8 mg/L near the surface during the winter. However, in a study conducted between 1996 and 1997, WDOE reported dissolved oxygen (DO) levels in the southern end of Discovery Bay below 3.0 mg/l (PSQAT 2000).
Macro vegetation—Eelgrass is the primary vegetation in the intertidal areas of the Strait of Juan de Fuca, covering 42.2 ± 27.2% of the intertidal area (Fig. 7), and green algae is the second most common covering 4.4 ± 3.7% of the intertidal area (Bailey et al. 1998). About 45% of the shoreline of this region consists of kelp habitat, compared to only 11% of the shoreline of the other four Puget Sound proper Basins (Shaffer 1998). Nevertheless, both areas each have approximately 50% of the total kelp resource. Most species of kelp are associated with shoreline exposed to wave action, whereas eelgrass is found in protected areas, such as Samish and Padilla Bays (Fig. 6). Some of the densest kelp beds in greater Puget Sound are found in the Strait of Juan de Fuca. Kelp beds at the north end of Protection Island declined drastically between 1989 and 1997, decreasing from about 181 acres to "nothing" (Sewell 1999). The cause of this decline is currently unknown.
Urban, industrial, and agricultural development—The North Puget Sound Basin is bordered primarily by rural areas with a few localized industrial developments (PSWQA 1988). About 71% of the area draining into North Puget Sound is forested, 6% is urbanized, and 15% is used for agriculture. Among the five greater Puget Sound basins, this basin is used most heavily for agriculture. The main human population in this area centers around Port Angeles (19,200), Port Townsend (7,000), Anacortes (11,500), and Bellingham (58,300) (Rand McNally 1998, 1996 population census ). About 10% of the total amount of wastes discharged from point-sources into greater Puget Sound comes from urban and industrial sources in this basin (PSWQA 1988). About 17% of the nutrients (in the form of inorganic nitrogen) entering greater Puget Sound originate from rivers carrying runoff from areas of agricultural and forest production (Embrey and Inkpen 1998). The Washington Department of Natural Resources (WDNR 1998) estimated that 21% of the shoreline in this area has been modified by human activities.
Bathymetry and geomorphology—The 75 km-long Main Basin is delimited to the north by a line between Point Wilson (near Port Townsend) and Partridge Point on Whidbey Island, to the south by Tacoma Narrows, and to the east by a line between Possession Point on Whidbey Island and Meadow Point (near Everett) (Fig. 5). The western portion of the Main Basin includes such water bodies as Sinclair and Dyes inlets, and Colvos and Dalco passages. Large embayments on the east side include Elliott and Commencement bays.
Among of the most important bathymetric features of the Main Basin are the sills at its northern and southern ends. The sill at the north end of Admiralty Inlet is 30 km wide and is 65 m deep at its shallowest point. The sill at Tacoma Narrows is 45 m deep (Burns 1985). South of Admiralty Inlet, depths generally range from 100 to 140 m in the central part of the basin, and 10 to 100 m in the waterways west of Bainbridge and Vashon islands. The central basin consists of five sub-basins: 1) one near the southern end of Admiralty Inlet, west of Marrowstone Island, with depths to 190 m, 2) one near the southern tip of Whidbey Island with depths to 250 m, 3) one west of Port Madison, north of Seattle with depths to 400 m, 4) one northeast of West Point in Seattle with depths to 350 m, 5) one south of Seattle, near Point Pulley, with depths to about 250 m (Burns 1985). Elliott and Commencement bays, associated with Seattle and Tacoma, respectively, are relatively deep, with depths in excess of 150 m. Freshwater flows into Elliott Bay through the Duwamish-Green River System, and into Commencement Bay through the Puyallup River.
Sediment characteristics—Subtidal surface sediments in Admiralty Inlet tend to consist largely of sand and gravel, whereas sediments just south of the inlet and southwest of Whidbey Island are primarily sand (PSWQA 1987). Sediments in the deeper areas of the central portion of the Main Basin generally consist of mud or sandy mud (PSWQA 1987, WDOE 1998). Sediments in the shallower and intertidal areas of the Main Basin are mixed mud, sand, and gravel. Bailey et al. (1998) reported that 92% of the intertidal area of the Main Basin consisted of mixed sand and gravel. A similar pattern is also found in the bays and inlets bordering this basin.
Currents and tidal activity—About 30% of the freshwater flow into the Main Basin is derived from the Skagit River. The Main Basin is generally stratified in the summer, due to river discharge and solar heating, and is often well mixed in the winter due to winter cooling and increased mixing by wind. Circulation in the central and northern sections of the Main Basin consists largely of outflow through Admiralty Inlet in the upper layer and inflow of marine waters at depth (below approximately 50 m) (Figs. 9a, 9b) (Strickland 1983, Thomson 1994). Oceanic waters from the Strait of Juan de Fuca flow over the northern sill at Admiralty Inlet into the Main Basin at about two-week intervals (Cannon 1983). In the southern section, currents generally flow northward along the west side of Vashon Island and southward on the east side through Colvos Passage (Fig. 11). The sill at Tacoma Narrows also causes an upwelling process that reduces the seawater/ freshwater stratification in this basin. With freshwater inflow, comes sediment deposits at an estimated rate of 0.18 to 1.2 grams/cm²/year (Staubitz et al. 1997).
Major circulation patterns in the Main Basin are greatly influenced by decadal climate regimes (Ebbesmeyer et al. 1998). During cool periods with strong oceanic upwellings and heavy precipitation, the strongest oceanic currents entering from the Strait of Juan de Fuca flow near mid-depth when the basin is cooler than 9.7oC. However, the strongest oceanic currents move toward the bottom of the basin, during warmer, dryer periods when waters are warmer than 9.7oC.
Water quality—Water temperature, salinity, and concentration of dissolved oxygen in waters of the Main Basin are routinely measured by the WDOE at six sites (WDOE 1999). Subsurface temperatures are usually between 8o and 12oC; however, surface temperatures can reach 15oC to 18oC in summer, and temperatures at depth can get as low as 7.5oC in winter. Salinities in the deeper portions of the Main Basin are generally about 30‰ in summer and fall, but decrease to about 29‰ during the rainier months. Surface waters are also usually about 29‰, but occasionally have salinities as low as 25-27‰ during the rainy season (WDOE 1999).
The mid-basin site had consistently higher temperatures and lower salinity values compared to the water quality parameters at the site near the northern entrance to Admiralty Inlet (WDOE 1999). To demonstrate this trend, values from near mid-basin at West Point in Seattle, considered to be representative of this basin, were compared to values from the northern end of Admiralty Inlet. Values measured on the same dates (a summer month and a winter month) and depths at each site for two different years (1993 and 1996) were compared. For the summer month, the mean temperature at mid-basin site was 12.25oC vs. 9.19oC for the entrance site. The mean salinities for this same month were 29.65‰ and 31.43‰, respectively. For the winter month, the mean temperature at mid-basin site was 9.71oC and 8.11oC for the entrance site. The mean salinity values for this same month were 30.24‰ and 30.84‰, respectively.
Dissolved oxygen varies seasonally, with lowest levels of about 5.5 mg/L occurring at depth in summer months, and highest levels of about 7.5 mg/L near the surface. Occasionally, summer-time highs reach 13-14 mg/L at the surface.
Macro vegetation—The Main Basin has a relatively small amount of intertidal vegetation, with 28.3 ± 10.4% of the intertidal area containing vegetation (Bailey et al. 1998). The predominant types are green algae (12.0 ± 4.4%) and eelgrass (11.4 ± 6.6%). Most eelgrass is located on the western shores of Whidbey Island and the eastern shores of the Kitsap Peninsula (Fig. 7) (PSWQA 1987). Although Figure 7 suggests a continuous distribution of eelgrass on the eastern shores of the Main Basin, a recent report by the Puget Sound Water Quality Action Team (PSWQAT 2000) indicates that only 8% of the shoreline has a continuous distribution of eelgrass beds and 40% of the shoreline has a patchy distribution.
Urban, industrial, and agricultural development—Areas bordering the Main Basin include the major urban and industrial areas of greater Puget Sound: Seattle, Tacoma, and Bremerton. Human population sizes for these cities are about 522,500, 182,900, and 44,000, respectively (1996 census) (Rand McNally 1998). Approximately 70% of the drainage area in this basin is forested, 23% is urbanized, and 4% is used for agriculture (Staubitz et al. 1997). About 80% of the total amount of waste discharged from point-sources into greater Puget Sound comes from urban and industrial sources in this region (PSWQA 1988). Moreover, about 16% of the waste entering greater Puget Sound, overall, enters this basin through its major river systems, in the form of inorganic nitrogen (Embrey and Inkpen 1998). The WDNR (1998) estimates that 52% of the shoreline in this area has been modified by human activities.
Bathymetry and geomorphology—The Whidbey Basin includes the marine waters east of Whidbey Island and is delimited to the south by a line between Possession Point on Whidbey Island and Meadowdale, west of Everett. The northern boundary is Deception Pass at the northern tip of Whidbey Island (Fig. 5). The Skagit River (the largest single source of freshwater in greater Puget Sound) enters the northeastern corner of the Basin, forming a delta and the shallow waters (<20 m) of Skagit Bay. Saratoga Passage, just south of Skagit Bay, separates Whidbey Island from Camano Island. This passage is 100 to 200 m deep, with the deepest section (200 m) located near Camano Head (Burns 1985). Port Susan is located east of Camano Island and receives freshwater from the Stillaguamish River at the northern end and from the Snohomish River (the second largest of greater Puget Sound’s rivers) at southeastern corner. Port Susan also contains a deep area (120 m) near Camano Head. The deepest section of the basin is located near its southern boundary in Possession Sound (220 m).
Sediment characteristics—The most common sediment type in the intertidal zone of the Whidbey Basin is sand, representing 61.4 ± 65.5% of the intertidal area. Mixed fine sediments is the next most common sediment type covering 25.6 ± 18.9% of the intertidal area (Bailey et al. 1998). Similarly, subtidal areas near the mouths of the three major river systems are largely sand. However, the deeper areas of Port Susan, Port Gardner, and Saratoga Passage have surface sediments composed of mixtures of mud and sand (PSWQA 1987, WDOE 1998). Deception Pass sediments consist largely of gravel.
Currents and tidal activity—Although only a few water circulation studies have been performed in the Whidbey Basin, some general observations are possible. Current profiles in the northern portion of this basin are typical of a close-ended fjord. The surface waters from the Skagit River diverge, with the surface water flowing south and the deep water flowing northward toward Deception Pass. Approximately 60% of the water from the Skagit River flows through Deception Pass, and this water flows directly into the Strait of Juan de Fuca (Ebbesmeyer et al. 1984). Current speeds through Deception Pass are among the highest in greater Puget Sound; a westward surface current speed of 37.37 cm/sec, and an eastward bottom current of 5.92 cm/sec were reported by PSWQA (1987). Currents through Saratoga Passage tend to move at moderate rates in a southerly direction (Fig. 12). Due to the influences of the Stillaguamish and Snohomish River systems, surface currents in Port Susan and Port Gardner tend to flow toward the Main Basin, although there is some evidence of a recirculating pattern in Port Susan (PSWQA 1987).
Water quality—The waters in this basin are generally stratified, with surface waters being warmer in summer (generally 10-13oC) and cooler in winter (generally 7-10oC) (Collias et al. 1974, WDOE 1999). Salinities in the southern section of the Whidbey Basin in Possession Sound are similar to those of the Main Basin. In Port Susan and Saratoga Passage, salinities of surface waters (27.0-29.5‰) are generally lower than in the Main Basin, due to runoff from the two major rivers; moreover, after heavy rain these salinities range from 10-15‰. However, salinities in deeper areas often parallel those of the Main Basin (WDOE 1999).
Concentrations of dissolved oxygen in the waters of the Whidbey Basin are routinely measured by the WDOE in Saratoga Passage and in Port Gardner (WDOE 1999). Concentrations were highest in surface waters (up to 15 mg/L) and tended to be inversely proportional to salinity. Samples collected during spring run-off had the highest concentrations of dissolved oxygen. The lowest values (3.5 to 4.0 mg/L) were generally found at the greatest depths in fall. However, in a study conducted between 1996 and 1997, WDOE reported DO levels in the west end of Penn Cove below 3.0 mg/L (PSWQAT 2000).
Macro vegetation—Vegetation covers 23.6 ± 8.8% of the intertidal area of the Whidbey Basin (Bailey et al. 1998). The three predominant types of cover include green algae (6.8 ± 6.2%), eelgrass (6.5 ± 5.8%), and salt marsh (9.0 ± 9.4%). Eelgrass beds are most abundant in Skagit Bay and in the northern portion of Port Susan (Fig. 7) (PSWQA 1987).
Urban, industrial, agricultural, and development—Most of the Whidbey Basin is surrounded by rural areas with low human population densities. About 85% of the drainage area of this Basin is forested, 3% is urbanized, and 4% is in agricultural production. The primary urban and industrial center is Everett, with a population of 78,000. Most waste includes discharges from municipal and agricultural activities and from a paper mill. About 60% of the nutrients (as inorganic nitrogen) entering greater Puget Sound, enter through the Whidbey Basin by way of its three major river systems (Embrey and Inkpen 1998). The WDNR (1998) estimated that 36% of the shoreline in this area has been modified by human activities.
Bathymetry and geomorphology—The Southern Basin includes all waterways south of Tacoma Narrows (Fig. 5). This basin is characterized by numerous islands and shallow (generally <20 m) inlets with extensive shoreline areas. The mean depth of this basin is 37 m, and the deepest area (190 m) is located east of McNeil Island, just south of the sill (45 m) at Tacoma Narrows (Burns 1985). The largest river entering the basin is the Nisqually River which enters just south of Anderson Island.
Sediment characteristics—A wide assortment of sediments are found in the intertidal areas of this basin (Bailey et al. 1998). The most common sediments and the percent of the intertidal area they cover are as follows: mud, 38.3 ± 29.3%; sand, 21.7 ± 23.9%; mixed fine, 22.9 ± 16.1%; and gravel, 11.1 ± 4.9%. Subtidal areas have a similar diversity of surface sediments, with shallower areas consisting of mixtures of mud and sand, and deeper areas consisting of mud (PSWQA 1987). Sediments in Tacoma Narrows and Dana Passage consists primarily of gravel and sand.
Currents and tidal activity—Currents in the Southern Basin are strongly influenced by tides, due largely to the shallowness of this area. Currents tend to be strongest in narrow channels (Burns 1985). In general, surface waters flow north and deeper waters flow south. Among the five most western inlets, Case, Budd, Eld, Totten, and Hammersley, the circulation patterns of Budd and Eld inlets are largely independent of those in Totten and Hammersley inlets due largely to the shallowness of Squaxin Passage (Ebbesmeyer et al. 1998). These current patterns are characterized by flows of high salinity waters from Budd and Eld inlets into the south end of Case Inlet, and from Totten and Hammersley inlets into the north end of Case Inlet. Flows of freshwater into the north and sound ends of Case Inlet originate from surface water runoff and the Nisqually River, respectively.
Water quality—The major channels of the Southern Basin are moderately stratified compared to most other greater Puget Sound basins, because no major river systems flow into this basin. Salinities generally range from 27-29‰, and, although surface temperatures reach 14-15oC in summer, the temperatures of subsurface waters generally range from 10-13oC in summer and 8-10oC in winter (WDOE 1999). Dissolved oxygen levels generally range from 6.5 to 9.5 mg/L. Whereas salinities in the inlets tend to be similar to those of the major channels, temperatures and dissolved oxygen levels in the inlets are frequently much higher in summer. Two of the principal inlets, Carr and Case inlets, have surface salinities ranging from 28-30‰ in the inlet mouths and main bodies, but lower salinities ranging from 27-28‰ at the heads of the inlets (Collias et al. 1974). Summertime surface waters in Budd, Carr and Case Inlets commonly have temperatures that range from 15-19oC and dissolved oxygen values of 10-15 mg/L. Temperature of subsurface water tends to be elevated in the summer (14-15oC); however, temperatures are similar to those of the main channels in other seasons of the year (WDOE 1999).
Macro vegetation—Among the five basins of greater Puget Sound, the Southern Basin has the least amount of vegetation in its intertidal area (12.7 ± 15.5% coverage), with salt marsh (9.7 ± 14.7% coverage) and green algae (2.1 ± 1.9% coverage) being the most common types (Bailey et al. 1998).
Urban, industrial, and agricultural development—About 85% of the area draining into this basin is forested, 4% is urbanized, and 7% is in agricultural production. The major urban areas around the South Sound Basin are found in the western portions of Pierce County. These communities include west Tacoma, University Place, Steilacoom, and Fircrest, with a combined population of about 100,000. Other urban centers in the South Sound Basin include Olympia with a population of 41,000 and Shelton with a population of 7,200 (Puget Sound Regional Council [PSRC] 1998). Important point sources of wastes include sewage treatment facilities in these cities and a paper mill in Steilacoom. Furthermore, about 5% of the nutrients (as inorganic nitrogen) entering greater Puget Sound, enter into this basin through non-point sources (Embrey and Inkpen 1998). The WDNR (1998) estimated that 34% of the shoreline in this area has been modified by human activities.
Bathymetry and geomorphology—Hood Canal branches off the northwest part of the Main Basin near Admiralty Inlet and is the smallest of the greater Puget Sound basins, being 90 km long and 1-2 km wide (Fig. 5). Like many of the other basins, it is partially isolated by a sill (50 m deep) near its entrance that limits the transport of deep marine waters in and out of Hood Canal (Burns 1985). The major components of this basin consist of the Hood Canal entrance, Dabob Bay, the central region, and The Great Bend at the southern end. Dabob Bay and the central region are the deepest sub-basins (200 and 180 m, respectively), whereas other areas are relatively shallow, <40 m for The Great Bend and 50-100 m at the Hood Canal entrance (Collias et al. 1974).
Sediment characteristics—Sediment in the intertidal zone consists mostly of mud (53.4 ± 89.3% of the intertidal area), with similar amounts of mixed fine sediment and sand (18.0 ± 18.5% and 16.7 ± 13.7%, respectively) (Bailey et al. 1998). Surface sediments in the subtidal areas also consist primarily of mud, with the exception of the Hood Canal entrance, which consists of mixed sand and mud, and The Great Bend and Lynch Cove, which have patchy distributions of sand, gravelly sand, and mud (PSWQA 1987, WDOE 1998).
Currents and tidal activity—Aside from tidal currents, currents in Hood Canal are slow, perhaps because the basin is a closed-ended fjord without large-volume rivers. The strongest currents tend to occur near the Hood Canal entrance and generally involve a northerly flow of surface waters into Admiralty Inlet (Ebbesmeyer 1984).
Water quality—Water temperature, salinity, and concentration of dissolved oxygen in Hood Canal are routinely measured by the WDOE at two sites, near The Great Bend and near the Hood Canal entrance (WDOE 1999). Salinities generally range from 29-31‰ and tend to be similar at both sites. In contrast, temperature and dissolved oxygen values are often markedly different between the two sites. Values measured on the same dates (a summer month and a winter month) and at the same depths at each site for 1993 and 1996 demonstrate these differences. Mean temperature in the summer month at The Great Bend site was 9.9oC, but 12.1oC at the Hood Canal entrance site. Mean dissolved oxygen values for this same month were 3.24 mg/L and 6.67 mg/L at The Great Bend and Hood Canal entrance sites, respectively. For the winter month, the mean temperature at The Great Bend site was 10.6oC, but 9.1oC for the Hood Canal entrance site. Mean dissolved oxygen for this same month were 4.22 mg/L and 6.78 mg/L at The Great Bend and Hood Canal entrance sites, respectively.
Macro vegetation—Vegetation covers 27.8 ± 22.3% of the intertidal areas of the Hood Canal Basin. Salt marsh (18.0 ± 8.8%) and eelgrass (5.4 ± 6.3%) are the two most abundant plants (Bailey et al. 1998). Eelgrass is found in most of Hood Canal, especially in The Great Bend and Dabob Bay (Fig. 7).
Urban, industrial, and agricultural development—The Hood Canal Basin is one of the least developed areas in greater Puget Sound and lacks large centers of urban and industrial development. About 90% of the drainage area in this basin is forested (the highest percentage of forested areas of the five greater Puget Sound basins), 2% is urbanized, and 1% is in agricultural production (Staubitz et al. 1997). However, the shoreline is well developed with summer homes and year-around residences (PSWQA 1988). A small amount of waste is generated by forestry practices and agriculture. Nutrients (as inorganic nitrogen) from non-point sources in this basin represent only 3% of the total flowing into greater Puget Sound annually (Embrey and Inkpen 1998). The WDNR (1998) estimated that 34% of the shoreline in this area has been modified by human activities.
Algal productivity in the open waters of the central basin of Puget Sound proper is dominated by intense blooms of microalgae beginning in late April or May and recurring through the summer. Annual primary productivity in the central basin of the Sound is about 465 g C/m2. This high productivity is due to intensive upward transport of nitrate by the estuarine mechanism and tidal mixing. Chlorophyll concentrations rarely exceed 15 ug/L. Frequently, there is more chlorophyll below the photic zone than within it. Winter et al. (1975) concluded that phytoplankton growth was limited by a combination of factors, including vertical advection and turbulence, light, sinking and occasional rapid horizontal advection of the phytoplankton from the area by sustained winds. Summer winds from the northwest would be expected to transport phytoplankton to the south end of the Sound which could exacerbate the anthropogenic effects that are already evident in some of these inlets and bays (Harrison et al. 1994).
The abundance and distribution of zooplankton in greater Puget Sound is not well understood. A few field surveys have been conducted in selected inlets and waterways, but reports on Sound-wide surveys are lacking. In general, the most numerically abundant zooplankton throughout the greater Puget Sound region are the calanoid copepods, especially Pseudocalanus spp. (Giles and Cordell 1998, Dumbauld 1985, Chester et al. 1980, Ohman 1990). Giles and Cordell (1998) reported that crustaceans (primarily calanoid copepods) were most abundant in Budd Inlet in South Puget Sound, although larvae of larvaceans, cnidarians, and polychaetes in varying numbers were also abundant during the year. In a similar study, conducted by Dumbauld (1985) at two locations in the Main Basin (a site near downtown Seattle and a cluster of sites in the East Passage near Seattle covering a variety of depths from 12 to 220 m), Dumbauld found that calanoid copepods and cyclopoid copepods, and two species of larvaceans were dominant numerically. Dominant copepods at deeper sites were Pseudocalanus spp. and Corycaeus anglicus. The larvacean, Oikopleura dioica, was also relatively common at the shallow sites. Similarly, the most abundant zooplankton in the Strait of Juan de Fuca were reported by Chester et al. (1980) to be calanoid copepods, including Pseudocalanus spp. and Acartia longiremis, and the cyclopoid copepod, Oithona similis.
It is likely that zooplankton assemblages vary both seasonally and annually. Evidence of depth-specific differences was reported by Ohman (1990). In studies conducted in Dabob Bay near Hood Canal, Ohman (1999) compared the abundance of certain zooplankton species at a shallow and deep site. Ohman (1999) found one species of copepod (Pseudocalanus newmani) that was common at both sites, whereas species (e.g., Euchaeta elongata and Euphausia pacifica) that prey upon P. newmani were abundant at the deep site, but virtually absent from the shallow site. An example of seasonal variability was reported by Bollens et al. (1992b). In Dabob Bay, E. pacifica larvae were abundant in the spring and absent in the winter, and juveniles and adults were most abundant in the summer and early fall, with their numbers declining in the winter (Bollens et al. 1992b).
A few Sound-wide surveys of abundance and distribution of benthic invertebrates have been performed (Lie 1974, Llansó et al. 1998). A common finding among these surveys is that certain species prefer specific sediment types. For example, in areas with predominantly sandy sediments, among the most common species are Axinopsida serricata (a bivalve) and Prionospio jubata (a polychaete). In muddy, clayey areas of mean to average depth, Amphiodia urtica-periercta (a echinoderm) and Eudorella pacifica (a cumacean) are among the most common species. In areas with mixed mud and sand, Axinopsida serricata and Aphelochaeta sp. (a polychaete) are commonly found. And lastly, in deep muddy, clayey areas, predominant species tend to be Macoma carlottensis (a bivalve) and Pectinaria californiensis (a polychaete). In general, areas with sandy sediments tend to have the most species (Llansó et al. 1998), but the lowest biomass (Lie 1974). Areas with mixed sediments tend to have the highest biomass (Lie 1974).
As with zooplankton, assemblages of benthic invertebrates vary both seasonally and annually. Lie (1968) reported seasonal variations in the abundance of species, with the maxima taking place during July-August, and the minima occurring in January to February. However, there were no significant variations in the number of species during different seasons. Annual variation was examined by Nichols (1988) at three Puget Sound proper sites in the Main Basin: two deep sites (200-250 m) and one shallow site (35 m). For one of the deep sites, he reported that M. carlottensis generally dominated the benthic community from 1963 through the mid-1970s. Subsequently, these species were largely replaced by A. serricata, E. pacifica, P. californensis, Ampharete acutifrons (a polychaete), and Euphiomedes producta (an ostracod). A similar dominance by P. californensis and A. acutifrons was reported for the other deep site over approximately the same time period.
Several macroinvertebrate species are widely distributed in greater Puget Sound. Among the crustacean species, Dungeness crab (Cancer magister) and several species of shrimp (e.g., sidestripe [Pandalopsis dispar] and pink [Pandalus borealis]) are the most commonly harvested species (Bourne and Chew 1994). The non-indigenous Pacific oyster (Crassostrea gigas) accounts for approximately 90% of the landings of bivalves. Other abundant bivalves are the Pacific littleneck clam (Protothaca staminea), Pacific geoduck (Panopea abrupta), Pacific gaper (Tresus nuttalii), and the non-indigenous Japanese littleneck clam (Tapes philippinarum) and softshell clam (Mya arenaria) (Kozloff 1987, Turgeon et al. 1988).
The most common Pacific salmon species utilizing greater Puget Sound during some portion of their life cycle include chinook (Oncorhynchus tshawytscha), coho (O. kisutch), chum (O. keta), pink (O. gorbuscha), and sockeye salmon (O. nerka). Anadromous steelhead (O. mykiss) and cutthroat trout (O. clarki clarki) also utilize greater Puget Sound habitats.
Palsson et al. (1997) identified about 221 species of fish in greater Puget Sound. The marine species are generally categorized as bottomfish, forage fish, non-game fishes, and other groundfish species. In addition to Pacific hake, Pacific cod, and walleye pollock, other important commercial marine fish species in greater Puget Sound are Pacific herring, spiny dogfish (Squalus acanthias), lingcod (Ophiodon elongatus), various rockfish species (Sebastes spp.), and English sole (Pleuronectes vetulus). English sole are thought to be relatively healthy in the central portions of Puget Sound proper; however, significant declines have been recorded in localized embayments, such as Bellingham Bay and Discovery Bay. Other species of bottomfish species found throughout greater Puget Sound include skates (Raja rhina and R. binoculata), spotted ratfish (Hydrolagus cooliei), sablefish (Anoplopoma fimbria), greenlings (Hexagrammos decagrammus and H. stelleri), sculpins (e.g., cabezon [Scorpaenichthys marmoratus], Pacific staghorn sculpin [Leptocottus armatus], and roughback sculpin [Chitonotus pugetensis]), surfperches (e.g., pile perch [Rhacochilus vacca] and striped seaperch [Embiotoca lateralis]), wolf-eel (Anarrhichthys ocellatus), Pacific sanddab (Citharichthys sordidus), butter sole (Pleuronectes isolepis), rock sole (Pleuronectes bilineatus), Dover sole (Microstomus pacificus), starry flounder (Platichthys stellatus), sand sole (Psettichthys melanostictus), and over one dozen rockfish species (e.g., brown rockfish [Sebastes auriculatus], copper rockfish [S. caurinus], greenstriped rockfish [S. elongatus], yellowtail rockfish [S. flavidus], quillback rockfish [S. maliger], black rockfish, [S. melanops] and yelloweye rockfish [S. ruberrimus]) (DeLacy et al. 1972, Robins et al. 1991). Additional fish species that are less known, but widely distributed in greater Puget Sound, include surf smelt (Hypomesus pretiosus), plainfin midshipman (Porichthys notatus), eelpouts (e.g., blackbelly eelpout [Lycodopsis pacifica]), pricklebacks (e.g., snake prickleback, [Lumpenus sagitta]), gunnels (e.g., penpoint gunnel [Apodichthys flavidus]), Pacific sand lance (Ammodytes hexapterus), bay goby (Lepidogobius lepidus), and poachers (e.g., sturgeon poacher [Podothecus acipenserinus]) (DeLacy et al. 1972, Robins et al. 1991).
About 66,000 marine birds breed in or near greater Puget Sound. About 70% of them breed on Protection Island, located just outside of the northern entrance to the Sound. The most abundant species are rhinoceros auklet (Cerorhinca monocerata), glaucous_winged gull (Larus glaucescens), pigeon guillemot (Cepphus columba), cormorants (Phalacrocorax spp.), marbled murrelet (Brachyramphus marmoratus), and the Canada goose (Branta canadensis). Examples of less abundant species include common murre (Uria aalge) and tufted puffins (Fratercula cirrhata). A number of additional bird species use greater Puget Sound during the winter months. Dabbling ducks, including American wigeon (Anas americana), mallard ducks (A. platyrhynchos) and northern pintail (A. acuta), are the most common, followed by geese and swans, such as trumpeter swans (Cygnus columbianus), tundra swans (C. columbianus), and Canada geese (Branta canadensis) (Mahaffy et al. 1994).
Populations of rhinoceros auklet and pigeon guillemot appear to be stable, whereas populations of glaucous_winged gull have increased slightly in recent years, especially in urban areas (Mahaffy et al. 1994). Accurate estimates of current populations of marbled murrelet and the Canada goose are not available, but the population of marbled murrelet has been greatly reduced and this species has been listed as threatened. Thirty years ago, year_around resident Canada geese were rare, but current anecdotal evidence from observations in waterfront parks suggests that their population is growing rapidly. The common murre and tufted puffin populations have declined drastically during the last two decades.
Nine primary marine mammal species occur in greater Puget Sound including (listed in order of abundance): harbor seal (Phoca vitulina), California sea lion (Zalophus californianus), Steller sea lion (Eumetopias jubatus), Northern elephant seal (Mirounga angustirostris), harbor porpoise (Phocoena phocoena), Dall's porpoise (Phocoenoides dalli), killer whale (Orcinus orca), gray whale (Eschrichtius robustus), and minke whale (Balaenoptera acutorostrata). Harbor seals are year_round residents, and their abundance has been increasing in greater Puget Sound by 5 to 15% annually at most sites (Calambokidis and Baird 1994).
California sea lions, primarily males, reside in greater Puget Sound between late summer and late spring, and spend the remainder of the year at their breeding grounds in southern California and Baja California. Sea lion populations are growing at approximately 5% annually. Populations of the remaining species are quite low in greater Puget Sound. Steller sea lions and elephant seals are transitory residents, whereas the Steller sea lion is currently listed as threatened in the U.S., the elephant seal is abundant in the eastern North Pacific but has few haul_out areas in greater Puget Sound. Although harbor porpoises are also abundant in the eastern North Pacific and were common in greater Puget Sound 50 or more years ago, they are now rarely seen in the Sound (Calambokidis and Baird 1994). Low numbers of Dall's porpoise are observed in greater Puget Sound throughout the year, but little is known about their population size—they are also abundant in the North Pacific.
A pod of resident fish_feeding killer whales resides just north of the entrance to greater Puget Sound. The size of this group had reached about 100 by the mid-1990s and was increasing about 2.0% each year. However, by 1999, the size had decreased to about 83 whales, a decline of more than 15% (M. Dahlheim2). The causes of this decline are not known, but could include exposure to chemical contaminants, reduced availability of prey resources, and increased human activities.
Minke whales are also primarily observed in this same northern area, but their population size is unknown. Gray whales migrate past the Georgia Basin en route to or from their feeding or breeding grounds; a few of them enter greater Puget Sound during the spring through fall to feed.
The Georgia Basin is an international waterbody that encompasses the marine waters of greater Puget Sound, and the Strait of Georgia. (Fig. 13). The coastal drainage of the Georgia Basin is bounded to the west and south by the Olympic and Vancouver Island mountains and to the north and east by the Cascade and Coast mountains. At sea level, the Basin has a mild maritime climate and is dryer than other parts of the coast due to the rain shadow of the Olympic and Vancouver Island mountains. At sea level, air temperatures range from 0oC to 5oC in January and 12oC to 22oC in July, and winds are typically channeled by the local topography and blow along longitudinal axes of the straits and sounds. Winds are predominantly from the southeast in winter and the northwest in summer.
The Strait of Georgia (Fig. 13) has a mean depth of 156 m (420 m maximum) and is bounded by narrow passages (Johnstone Strait and Cordero Channel to the north and Haro and Rosario straits to the south) and shallow submerged sills (minimum depth of 68 m to the north and 90 m to the south). The Strait of Georgia covers an area of approximately 6,800 km2 (Thomson 1994) and is approximately 220 km long and varies from 18.5 to 55 km in width (Tully and Dodimead 1957, Waldichuck 1957). Both southern and northern approaches to the Strait of Georgia are through a maze of islands and channels, the San Juan and Gulf islands to the south and a series of islands to the north that extend for 240 km to Queen Charlotte Strait (Tully and Dodimead 1957). Both northern channels (Johnstone Strait and Cordero Channel) are from 1.5 to 3 km wide and are effectively two-way tidal falls, in which currents of 12-15 knots occur at peak flood (Tully and Dodimead 1957). However, both lateral and vertical constriction of water flow at the narrowest points in these northern channels are even more severe. Constrictions occur at Arran Rapids, Yuculta Rapids, Okisollo Channel, and to a lesser degree at Seymour Narrows (0.74 km wide, minimum depth of 90 m) in Discovery Passage (Waldichuck 1957). Overall, these narrow northern channels have only about 7% of the cross-sectional area as do the combined southern entrances into the Strait of Georgia (Waldichuck 1957).
Freshwater inflows are dominated by the Fraser River, which accounts for roughly 80% of the freshwater entering the Strait of Georgia. Fraser River run-off and that of other large rivers on the mainland side of the Strait are driven by snow and glacier melt and their peak discharge period is generally in June and July. Rivers that drain into the Strait of Georgia off Vancouver Island (such as the Chemainus, Cowichan, Campbell, and Puntledge rivers) peak during periods of intense precipitation, generally in November (Waldichuck 1957).
Circulation in the Strait of Georgia occurs in a general counter-clockwise direction (Waldichuck 1957). Tides, winds, and freshwater run-off are the primary forces for mixing, water exchange, and circulation. Tidal flow enters the Strait of Georgia predominantly from the south creating vigorous mixing in the narrow, shallow straits and passes of the Strait of Georgia. The upper, brackish water layer in the Strait of Georgia is influenced by large freshwater run-off and salinity in this layer varies from 5 to 25‰. Deep, high-salinity (33.5 to 34‰), oceanic water enters the Strait of Georgia from the Strait of Juan de Fuca. The surface outflowing and deep inflowing water layers mix in the vicinity of the sills, creating the deep bottom layer in the Strait of Georgia, where salinity is maintained at about 31‰ (Waldichuck 1957). The basic circulation pattern in the southern Strait of Georgia is a is a southerly outflow of low-salinity surface water through the Rosario and Haro Straits (Crean et al. 1988) (Fig. 14) with the northerly inflow of high salinity oceanic water from the Strait of Juan de Fuca at the lowest depths. In the winter, cool, low salinity near surface water mixes with the intermediate depth high-salinity waters; however, oceanic inflow is generally confined to the intermediate depths. Crean et al. (1988) reported that "the freshwater discharge finds primary egress through the southern boundary openings into the Strait of Juan de Fuca" and that subsurface waters (5 to 20 m below the region of the Fraser River discharge) also have "a predominantly southerly flow." Since surface water run-off peaks near the time of peak salinity of inflowing source water, the salinity of the deepwater in the Strait of Georgia undergoes only a small seasonal change in salinity (Waldichuck 1957).
Although most marine fishes are external fertilizers, all rockfishes have internal fertilization. Females may or may not mate with multiple males but generally produce one brood of young per year. The mating process can include an elaborate behavioral ritual which increases the criteria of mate choice and can lead to assortative mating and sexual selection (Shinomiya and Ezaki 1991). If a larva successfully disperses and recruits to a distant population it can still be prevented from successfully mating with the local population due to subtle differences in color, courtship behavior, or seasonality of reproduction.
Most marine fishes are oviparous. They release multiple batches of eggs that are fertilized externally, often from multiple males. Eggs drift passively until hatching and the development of directed swimming movements and buoyancy regulation. In contrast, rockfishes are ovoviviparous. As noted above, they have internal fertilization of eggs. Eggs hatch in the ovary where development continues until release. At release larvae are often well developed with functional organs and the capacity to swim and regulate buoyancy. Release of live young means that the mother can potentially regulate the timing and location of release of larvae. The release of larvae capable of swimming and controlling their buoyancy can alter the period of passive dispersal and shorten the overall planktonic dispersal phase.
Sebastes is the most species-rich genus in the northeast Pacific with over 70 species occurring along the coasts of the continental U.S., Alaska, Canada, and Baja Mexico. Most species are relatively young in an evolutionary sense and speciation is ongoing. As a result, there appears to be incomplete lineage sorting (Avise 1994). This means that closely related species or subspecies may share similar or identical mitochondrial haplotypes (Rocha-Olivares and Vetter 1999, Rocha-Olivares et al. 1999a, Narum 2000). This incomplete sorting may give the appearance of introgression in mitochondrial DNA (mtDNA) when it is not apparent in microsatellite data (Narum 2000).
Copper, quillback, and brown rockfishes belong to a common genetic lineage, the Pteropodus subgenus, within the genus Sebastes (Seeb 1986, Rocha-Olivares et al. 1999b, Taylor 1998). They share life-history characteristics that may further influence population structure. They are all sedentary, non-schooling species. In general, the Pteropodus rockfishes are the shallowest dwelling group and are most likely to release larvae that are subject to local retention mechanisms. They release larvae after the spring upwelling season and their survival is favored by a different set of oceanographic conditions than other rockfish species (Lenarz et al. 1995). Their larvae tend to be larger and more developed than other Sebastes larvae (G. Moser3), yet they tend to settle out and recruit to their adult habitat at a smaller size (Anderson 1983, Carr 1991). All of these characteristics may tend to limit the dispersal phase of their life history.
Pteropodus rockfishes living in sympatry are capable of assortative mating. Black-and-yellow rockfish (S. chrysomelas), and gopher rockfish (S. carnatus), are not distinguishable on the basis of morphology, meristics, and some genetic measures (Chen 1986, Alesandrini and Bernardi 1999), but differ in color, behavior and depth preference (Larson 1980a, b). Analyses of microsatellite nuclear DNA (nDNA) clearly showed that populations living in the same location were assortatively mating despite sharing many common mtDNA haplotypes (Narum 2000). Assortative mating can maintain or promote differentiation in zones of secondary contact after periods of isolation.
Copper rockfish are found from the Gulf of Alaska southward to central Baja California (Eschmeyer et al. 1983, Love 1996, Mathews 1990c, Stein and Hassler 1989). Adult copper rockfish occur in nearshore waters, reportedly from the surface to 183 m (Eschmeyer et al. 1983, Stein and Hassler 1989), and are somewhat shallower during upwelling (Stein and Hassler 1989). They are common in greater Puget Sound (Buckley and Hueckel 1985, Quinnell and Schmitt 1991).
Larval and small juvenile copper rockfish are pelagic for several months, and are frequently associated with surface waters and in shallow habitats, up to about 6 m (Stein and Hassler 1989, Love et al. 1991). They may use bays as nursery areas (Stein and Hassler 1989). With time, these stages recruit to nearshore substrates in surface waters, such as bull kelp fronds, benthic macrophytes, and eelgrass. In central California juveniles are closely associated initially with the surface and mid_depth Macrocyctis kelp beds (Stein and Hassler 1989). Off British Columbia, juveniles have been found riding in gooseneck barnacles on floatsam (Stein and Hassler 1989).
Juvenile copper rockfish that migrate from surface habitats to benthic habitats are considered habitat generalists (Matthews 1990b). Young_of_the_year (YOY) copper rockfish initially occupy a greater diversity of habitats off British Columbia than California. Kelp forests and eelgrass beds are an especially important habitat during this phase (Haldorson and Richards 1986). In the Georgia Basin, small YOY copper rockfish are first observed in August through October in cobble, near the base of rockpiles, or under pieces of bark or fronds of kelp lying on the bottom (Patten 1973, Love 1996, Love et al. 1991). Benthic macrophytes and crevices in rocky areas are also important habitats (Buckley 1997).
Adult copper rockfish are also common in rocky areas and on rock_sand bottoms in shallow water (Eschmeyer et al. 1983, Haldorson and Richards 1986, Stein and Hassler 1989). Although copper rockfish are rarely observed on an exclusively sand bottom (Patten 1973, Stein and Hassler 1989), they are captured during trawl surveys in greater Puget Sound, suggesting that some copper rockfish may occasionally reside on uncompacted bottom types. These bottom types include low-relief reefs composed of cobble, terrestrial debris such as submerged logs, or the high volume of drift algae that are carried to the non-photic zone. They are found on natural rocky reefs, artificial reefs, and rock piles; typically found directly on the bottom, closely associated with reefs or vegetation (Matthews 1990c). In a study off British Columbia (Murie et al. 1994), copper rockfish were observed within 3 m of quillback rockfish 92% of the time. They have even been sighted sharing caves with giant Pacific octopus (Love 1996). Copper rockfish hide in rock interstices in the winter but not in the summer (Patten 1973). Fish within rockpiles are inactive and maintain contact, even curving their bodies around rocks (Patten 1973). From July to October, when bull kelp is the most dense, few copper rockfish are seen in the rock interstices, but they are always within 1 m of the rocks’ perimeter (Patten 1973). On natural high-relief rocky reefs, they maintained small home ranges (most within a 30_m2 area), yet returned to their home sites when experimentally displaced up to 6.4 km in an underwater tag_resighting study (Matthews 1990a).
On low-relief reefs, they have larger home ranges (Mathews 1990c). These low-relief reefs are only inhabited by copper rockfish during the summer, coincident with the densest kelp cover; in fall and winter when algal cover is reduced, low-relief reefs appear quite barren (Matthews 1990a). Copper rockfish do not seem to defend their territories. They assess habitat quality on the presence of structure, protective cover, mates, and food -- not on the presence of predators (Matthews 1990a). When copper rockfish and quillback rockfish are located on the same reef, quillback rockfish generally occupy the deeper depths (Matthews 1987).
Copper rockfish also avoid warm water by living in deeper depths off southern California (usually below 55 m) than farther north. Conversely, off British Columbia, they are found in quite shallow water, mostly less than 18 m (Love 1996).
Copper rockfish are moderately important in the recreational catch from southern California northward to at least southeastern Alaska. Adults are commonly taken by party and private vessels and the young are occasionally taken from piers, jetties and rocky shores (Love 1996). Copper rockfish are part of the commercial catch off California, taken primarily by hook and line and gill nets (Love 1996). Gowan (1983) conducted a creel survey in Puget Sound proper (around the periphery of Bainbridge Island) in the mid-1970s, and reported that rockfish were one of the most commonly caught groups of fish, and approximately 50% of the rockfish were copper rockfish.
Copper rockfish may move inshore to release their young (Matthews 1990a). In greater Puget Sound, juvenile copper rockfish are widely distributed among a variety of habitat types (Matthews 1990b). In the summer, they are found in such varied habitats as sand/eelgrass, sand/kelp, and low-relief reefs. In the winter, they generally remain in the same section of the shoreline, except they may move to slightly deeper water (Love et al. 1991). The young-of-the-year are thought to move to high-relief and artificial reefs in the late summer and fall. Once adults find a suitable reef, they tend to have very strong reef fidelity (Love 1996, Stein and Hassler 1989, Matthews 1990a). In northern waters, copper rockfish probably withdraw in winter deep within crevices to avoid storms (Love 1996).
Off central California, male copper rockfish may be sexually mature at age-3 (30 cm); all are mature by age-7 (40 cm). All females are mature off central California by age-8 (41 cm). In greater Puget Sound, sexual maturity occurs at age-4 in both males and females, but occasionally some mature at age-3 (Stein and Hassler 1989). Fertilization occurs from March to May off Washington. In greater Puget Sound, eggs mature by February-April (DeLacy et al. 1964). Egg production ranges from 15,000 eggs in a 24_cm female to 640,000 in one 47 cm long (DeLacy et al. 1964). The gonadosomatic index for copper rockfish from central Puget Sound proper has been reported to be 0.11 (Gowan 1983). Embryos are mature by April, and parturition occurs from April to June in greater Puget Sound (DeLacy et al. 1964, Matthews 1990b), from February to April south of British Columbia, and from March to July in southeastern Alaska (Love 1996). Copper rockfish spawn once per year.
Larvae measure 5_6 mm in length at birth, and they remain pelagic until 40_50 mm standard length (SL) (Stein and Hassler 1989). Copper rockfish are slow growing, with grow rates ranging from 0.15-0.20 mm/day for juveniles (Love et al. 1991). Growth rates are highest during the summer, coinciding with high feeding rates and upwelling (Stein and Hassler 1989). They live up to 55 years (Matthews 1990b), and can grow to 57 cm in length (Eschmeyer et al. 1983, Stein and Hassler 1989). In Humboldt Bay, California, fish are 110_155 mm long as age-0, 138_196 mm at age-1, 172_231 mm at age-2, and 220_300 mm at age-3 (Stein and Hassler 1989). The mortality rate for copper rockfish from central Puget Sound proper has been reported to be 0.233 (Gowan 1983).
Copper rockfish are opportunistic carnivores. Pelagic fish, demersal crustaceans (e.g. shrimp, prawns, and Cancer crabs) and pelagic crustaceans are the most important food groups of the copper rockfish in terms of mass, number, and frequency of occurrence (Murie 1995). In the southern part of the Strait of Georgia, they are reported to feed on herring, kelp perch, pile perch, squat lobsters, coonstriped shrimp, and to a lesser extent, mysids and euphausiids (Murie 1995). Demersal crustaceans were important prey throughout all seasons, increasing in occurrence from winter to fall (Murie 1995). Copper rockfish feed most intensively during sunrise and sunset (Murie 1995). In Humboldt Bay, juvenile Dungeness crabs were the most important individual food item in terms of volume and frequency of occurrence in the copper rockfish diet, with northern anchovy and shiner perch comprising the largest portion of fish (Prince and Gotshall 1976).
Quillback rockfish are found from the northern Channel Islands in southern California, to the Gulf of Alaska (Miller and Lea 1972). They are common in the Strait of Georgia, San Juan Islands (North Puget Sound), and Puget Sound proper (Clemons and Wilby 1961, Hart 1973, Love 1996, Matthews 1990a).
Quillback rockfish are a common, shallow_water benthic species (Matthews 1990a). They are taken from subtidal depths to 275 m (Hart 1973, Love 1996), but they occur mainly from 41_60 m (Love 1996, Murie et al. 1994). Buckley (1997) hypothesized that prior to settlement the pelagic larval and juvenile stages are located in mid-water habitats. Eventually they are thought to settle out on sandy/muddy habitats at "moderate depths" (Buckley 1997). These benthic juveniles (18_25 mm total length [TL]) gradually settle in shallow waters along the shores, and are associated with a variety of habitats, including drifting aggregates of benthic macrophytes, established bull kelp (Nereocysis luetkeana) beds, natural rock configurations, and artificial reefs (West et al. 1994). Young_of_the_year tend to be on the most complex areas of low_relief reefs (West et al. 1994) and use eelgrass/sand habitat as temporary habitat (Matthews 1990b). Densities on low_relief reefs and sand/eelgrass increase during the summer coincident with peak plant cover (Matthews 1990a). Adult quillback rockfish are solitary reef_dwellers, living close to, or on the bottom (Love 1996, Matthews 1988, Miller and Lea 1972, Rosenthal et al. 1988). Occasionally, they will rise up 9_12 m in the water column (Love 1996). When quillback rockfish and copper rockfish are located on the same reef, quillback rockfish generally occupy the deeper depths (Matthews 1987). In greater Puget Sound, they occupy a wide variety of habitats, having the highest densities on shallow (<30 m) reefs (Matthews 1990a). Quillback rockfish live among rocks or sometimes on coarse sand or pebbles next to reefs, particularly in areas with a high abundance of flat_bladed kelp (Love 1996). They are either found perched on rock or kelp or wedged into crevices and holes, and are rarely seen out in the open or unstructured areas of reefs (Matthews 1988).
Donnelly and Burr (1995) reported the results of trawls conducted in all the basins in greater Puget Sound, except Hood Canal, as well as a site in the Georgia Basin. Over 100 fish species were collected between 1983 and 1988. During the winter, spring, and summer months, quillback rockfish were among the 10 most common species collected at depths greater than 100 m. During these months, they were either not collected or were among the top 20 or higher most common species at depths between 5 and 50 m.
Quillback rockfish are important in the sport and commercial fisheries (Hart 1973, Murie et al. 1994). From Oregon to southeastern Alaska, quillback rockfish are an important part of the inshore sport fishery and are taken by party and private vessels and divers (Love 1996). Gowan (1983) conducted a creel survey in Puget Sound proper (around the periphery of Bainbridge Island) in the mid-1970s, and reported that rockfish were one of the most commonly caught groups of fish, and approximately 13% of the rockfish were quillback rockfish.
On high_relief rocky reefs in greater Puget Sound, adult quillback rockfish maintain small home ranges (within 30 m2) (Matthews 1990a). Off_reef movement occurs during the summer. During the fall and winter, they remain on artificial reefs. On low_relief rocky reefs, they maintain considerably larger home ranges (400_1,500 m2). Adult quillback rockfish only inhabit low-relief reefs during the summer and only return from displacements in the summer coincident with peak algal cover. They move from artificial reefs to low-relief reefs during the summer and return to artificial reefs in the fall when kelp disappears on low-relief reefs. Returns to original reefs when artificially displaced indicates site fidelity. Adult quillback rockfish can return to their home sites when experimentally displaced up to 6.4 km (Matthews 1990a). Quillback rockfish are not territorial of their home range. They may use navigation or olfactory cues to relocate home sites. They maintain small home ranges during the day, night, and high currents (Matthews 1988, 1990a and 1990c). Female quillback rockfish probably move to other habitat to release larvae because no pregnant individuals were observed in these studies (Matthews 1988).
Young-of-the-year quillback rockfish are more widely distributed among a variety of habitat types (Matthews 1990b). In the summer, they are found in such varied habitats as sand/eelgrass, sand/kelp, and low-relief reefs, and they are thought to move to high-relief and artificial reefs in the late summer and fall.
Quillback rockfish are ovoviviparous. In greater Puget Sound, most females are sexually mature by age-4 to age-5, although a few are sexually mature by age-2 to age-3 (Gowan 1983). Off southeastern Alaska 50% of quillback rockfish mature at 31 cm, and off California 50% mature at 23 cm (Love 1996). Mating probably occurs in March in greater Puget Sound and parturition in May (Matthews 1990b). Over their geographic range, they spawn from April_July, with a peak early in the season (Love 1996, Matthews 1988).
Quillback rockfish can grow to 61 cm (Clemons and Wilby 1961, Hart 1973, Love 1996). They can live to be 50 years old, but a few almost certainly live longer (Gowan 1983, Love 1996). Growth rates differ along its range; off southeastern Alaska a 12_year_old is approximately 31 cm, whereas off California a 12_year_old would only be 18 cm (Love 1996). The mortality rate for quillback rockfish from central Puget Sound proper (Fig. 5) has been reported to be 0.227 (Gowan 1983).
Growth rates of quillback rockfish from three sites in greater Puget Sound were compared by West and O’Neill (1995). The locations of the three sites were San Juan Islands, Double Bluff (on the south end of Whidbey Island), and Blake Island (near the south end of Bainbridge Island). Fish from the San Juan Island site were significantly larger than fish from the Blake Island site, even though their ages were not significantly different. Furthermore, when the length/age was plotted with a von Bertalanffy growth curve, the growth rate constant (k) increased from south to north. The authors (West and O’Neill 1995) were uncertain about the causes of these between-site differences, but suggested that they could be accounted for by environmental conditions (temperature), diet, habitat quality, levels of fishing pressure, or interspecific resource competition.
Quillback rockfish consume a wide range of prey taxa, but are more dietary generalists than other rockfish species (Rosenthal et al. 1988). Off British Columbia, quillback rockfish feed on herring and demersal and pelagic crustaceans. They feed primarily during mid_day and are inactive, sheltering in holes and crevices during the night (Murie 1995). In greater Puget Sound, quillback rockfish principally prey upon brachyuran crabs, gammarid amphipods, euphausiids, and calanoid copepods (Hueckel and Slayton 1982, Matthews 1990a, Rosenthal et al. 1988).
Brown rockfish are found from central Baja California to southeastern Alaska (Eschmeyer et al. 1983, Hart 1973, Love 1996, Matthews 1990b, Miller and Lea 1972, Stein and Hassler 1989). Brown rockfish are common in shallow water (Matthews 1990a, b) and occur from the surface to 128 m (Eschmeyer et al. 1983). However, they are most common from 6 m down and are widely distributed in shallow-water bays (Love 1996). Juveniles usually live in shallower water than adults (Love 1996). Brown rockfish use estuaries as nursery grounds (Stein and Hassler 1989) and they are common in Puget Sound proper (Hart 1973). There, brown rockfish initially settle at 18_25 mm TL, to shallow, vegetated habitats such as beds of kelp or eelgrass (West et al. 1994). Off California, young brown rockfish recruit to hard substrate and low (<1 m) relief reefs (Love et al. 1991). Brown rockfish are bottom dwellers, living on hard bottom such as low profile siltstone (Lea 1992) or sand. They aggregate near rocks, oil platforms, sewer pipes, and even old tires (Love 1996, Matthews 1990b).
In Puget Sound proper, highest densities are reported on natural reefs and rock piles in water less than 30 m (Matthews 1990b). However, Miller and Borton (1980) reported that brown rockfish were found almost exclusively in the Main Basin. In California, they are primarily found on sandy, low_relief areas (Matthews 1990b). Adults occupy higher_relief portions and young_of_the_year occupy lower_relief portions (West et al. 1994).
Brown rockfish maintain small home ranges on high-relief rocky reefs and display strong reef fidelity that is not affected by season. On artificial reefs in Puget Sound proper, they maintain small home ranges (most within 30 m2) (Matthews 1990b). In the summer, artificial reefs become less suitable and considerable off_reef movement occurs. On low-relief reefs, they maintain considerably larger home ranges (most within 400 m2 and some up to 1,500 m2). The low-relief reefs are only inhabited during the summer coincident with peak algal cover (Matthews 1990a).
Because brown rockfish inhabit shallow water, they are exposed to a relatively broad range of seasonal temperature variations, of at least 10o_17o C (Stein and Hassler 1989). Their capacity for acclimation is higher than that of rockfishes living below the thermocline and they can tolerate higher temperatures to at least 22oC (Stein and Hassler 1989). Occurrence in estuaries and oceanic waters suggests a relatively broad-salinity tolerance (Stein and Hassler 1989).
Brown rockfish are commonly taken from party boats off California (Mason 1995). They are also caught from private boats, piers and shore, and divers also take a few. Most of these fish, taken in shallow water, are juveniles. Brown rockfish are a valuable hook and line species for the commercial live_fish fishery in San Francisco Bay (Love 1996, Stein and Hassler 1989). They are a minor component of the recreational fishery in Puget Sound proper, representing only 2.4% of the total recreational bottomfish catch in the early-1980s (Matthews 1987). Also in Puget Sound proper, Gowan (1983) conducted a creel survey around the periphery of Bainbridge Island in the mid-1970s, and reported that rockfish were one of the most commonly caught groups of fish, and approximately 30% of the rockfish were brown rockfish.
Movements of greater than 3 km are rare for brown rockfish (Matthews 1990a) and they are said to have a strong homing tendency (Love 1996). Juveniles gradually move into deeper water as they mature (Love 1996).
Off Oregon, 50% of brown rockfish mature at 31 cm (age-5) and all are mature at 38 cm (10 years) (Love 1996). In Puget Sound proper, 50% of male and female brown rockfish are reported to be mature at age-4 (23-25 cm TL), and all are mature by age-7 (Matthews 1987). The smallest mature female found in Puget Sound proper was reported by Delacy et al. (1964) to be 22.5 cm. Little difference was observed in the length or age at first maturity between the sexes of brown rockfish from southern California — males matured between 19 (age-3) and 29 cm (age-6), and females matured at 21 (age-3) to 32 cm (age-6) (Love and Johnson 1998). Brown rockfish mate in March and April in Puget Sound proper (Stein and Hassler 1989). In Puget Sound proper, ova are thought to develop during winter (Delacy et al. 1964), they are carrying young in May, and probably give birth in June (Hart 1973). Off Oregon, spawning occurs in May and June (Love 1996).
The spawning season off central California is at least from December to July (Love 1996), whereas Love and Johnson (1998) report the spawning season off Southern California to be from January to August. Moreover, off-California females spawn more than once per season (Love 1996). In Puget Sound proper, they spawn once per year (Stein and Hassler 1989). A 31 cm female brown rockfish produces approximately 52,000 young and a 48_cm female produces 339,000 (Hart 1973).
Brown rockfish are 5_6 mm in length at birth (Stein and Hassler 1989) and can grow to a length of 55 cm (Hart 1973, Love 1996). Brown rockfish measuring 52 cm have been aged at 18 years (Love 1996). Males and females probably grow at the same rate and mature at similar ages and lengths (Love 1996). The mortality rate for brown rockfish from central Puget Sound proper has been reported to be 0.274 (Gowan 1983).
Juvenile brown rockfish consume amphipods, copepods and polychaetes (Matthews 1987). Larger juveniles and adults eat small fishes, crabs, shrimps, isopods, and polychaetes (Love 1996, Stein and Hassler 1989).
2 M. Dahlheim, NOAA Fisheries, 7600 Sand Point Way, N.E., Seattle WA 98115. Pers. commun., November 13, 2000.
3 G. Moser, NOAA, Southwest Fisheries
Science Center, 8604 La Jolla Shores Dr. 92037. Pers. commun., August,
2000.