Forecast of Adult Returns for Coho in 2009 and Chinook Salmon in 2010
From the colorized table below, one can see that the recent period of poor ocean conditions (2003–2006) has come to a close. Conditions began improving through 2007 and greatly improved during 2008. Highlights of 2008 ocean conditions include:
Positive signs
•
Most negative winter PDO since 2000 and most negative summer PDO since 1955
•
Most negative index of El Niño activity since 1999 (This indicates La Niña, or cold equatorial ocean conditions in the eastern Pacific.)
•
Coldest winter sea surface temperatures of the past 12 years
•
Early and strong coastal upwelling, with average upwelling strength during April–May (when juvenile salmon first enter the ocean) the 4th highest of 11 years
•
Coldest deep–water temperatures in the continental shelf of the past 12 years
•
Earliest biological spring transition of the past 13 years
•
Highest northern copepod biomass levels of the past 13 years
Somewhat negative signs
•
Sea surface temperatures were warm from 22 July until 27 August, possibly a negative sign for juvenile coho
•
Only a moderate number of juvenile coho were caught in our September survey (6th highest of 11 years)
Ocean ecosystem indicators of the Northern California Current. Colored squares indicate positive (green), neutral (yellow), or negative (red) conditions for salmon entering the ocean each year. In the two columns to the far right, colored dots indicate the forecast of adult returns based on ocean conditions in 2008.
We expect spring Chinook runs in 2010 and 2011 to rival the high returns of this species seen in 2001 and 2002; however, expectations for returns of coho in 2009 are somewhat lower due to warm sea–surface conditions throughout August and low catches of coho salmon in our September 2008 survey.
Table 1a below shows rank scores for the color–coding shown in Table 1. Scores were assigned based on their affect on juvenile salmonids. We show only variables that are correlated with salmon returns one year later (for coho) and two years later (for Chinook). For example, positive PDO values indicate poor ocean conditions in coastal waters off the northern California Current. Similarly, higher sea–surface temperatures in summer are a negative indicator for salmon. Note also that some indicators have 2 years with the same score. For example, among all years for which we have data, the best in terms of deep–water temperature was a tie between 2001 and 2002. Thus there are two ranks of 1 and no rank of 2 for this indicator.
Rank scores upon which color–coding of ocean ecosystem indicators is based. Lower numbers indicate better ocean ecoystem conditions, or "green lights" for salmon growth and survival, with ranks 1–4 green, 5–7 yellow, and 8–11 red. To arrive at these rank scores, 11 years of sampling data were compared across years (within each row), and each year received a rank between 1 and 11.
Year of Samples
1998
1999
2000
2001
2002
2003
2004
2005
2006
2007
2008
Pacific Decadal Oscillation
December–March
10
4
1
7
3
11
6
9
8
5
2
May–September
5
2
4
3
6
10
9
11
7
8
1
Multivariate El Niño Southern Oscillation Index
MEI Annual
11
1
3
5
10
9
7
8
6
4
2
MEI Jan–Jun
11
2
3
5
7
9
6
10
4
8
1
Sea surface temperature
Buoy 46050 (May–Sep mean)
9
2
4
5
1
7
11
8
6
10
2
NH 05 (May–Sep mean)
8
2
1
4
7
6
11
10
5
9
3
Winter prior to ocean entry
11
6
4
5
3
7
10
9
8
2
1
Physical spring transition (Logerwell)
7
6
2
1
4
9
8
11
9
3
5
Coastal upwelling April–May
6
1
10
3
5
9
8
11
6
2
4
Deep water at NH 05 (May–Sep)
Temperature
11
4
6
2
2
7
8
10
9
5
1
Salinity
11
3
3
5
8
9
10
7
6
1
1
Upwelling season length (d)
7
4
3
9
1
10
8
11
6
5
2
Copepod biodiversity
11
2
1
5
3
8
7
10
9
6
4
N Copepod anomalies
11
8
3
5
2
9
6
10
7
4
1
Biol. spring transition
11
6
3
5
4
9
7
10
8
2
1
Spring Chinook (Jun)
10
2
3
8
5
7
9
11
6
4
1
Coho (Sep)
9
2
1
4
3
5
10
11
7
8
6
Overall Ranking
Mean of ranks
9.5
3.5
3.2
4.6
4.3
8.6
8.0
9.7
6.9
5.1
2.4
Rank of mean ranks
10
3
2
5
4
9
8
11
7
6
1
To generalize conditions for each year, the sum of all the rank scores for that year is divided by the number of indicators observed in that year. Mean ranks are then compared among years to give a generalized concept of "good" vs. "bad" ocean conditions for salmon in a given year. Data used in the rank scores above are shown in the chart below.
