We departed for leg 4 of the groundfish survey late on the evening of June 26, sailing underneath the Golden Gate Bridge. Though too dark to see the bridge this year, the iconic brick-red suspension bridge is a familiar sight for Groundfish Survey biologists.
The Golden Gate Bridge as seen from below while embarking on leg 4 of the first pass of the 2016 Groundfish Survey. Photo credit: John Harms
This portion of the survey extended from San Francisco to Santa Barbara California. The scientific crew included Chief Scientist John Buchanan and back deck biologists John Harms and Aaron Chappell, and the vessel crew consisted of Capt. Mike Retherford Sr., deckhands Joey Jacques and Nate Smith, and night driver Kelsea Retherford. We encountered heavy seas (10 to 12 ft) and high winds (up to 30 kt) for the first 5 days.
During the 10 day leg, 42 station tows were completed successfully by the F/V Excalibur. Per the survey’s stratified random design, tows are allocated among three depth strata: 30 – 100 fathoms (55 – 183 m); 100 – 300 fathoms (183 – 549 m); and 300 – 700 fathoms (549 – 1281 m). That fathoms – a unit of depth commonly used by commercial fishermen – define the survey’s depth stratification is a legacy of the collaboration between NOAA and the West Coast groundfish industry that designed and developed this survey.
The F/V Excalibur’s 42 successful tows on Leg 4 were divided as follows:
Depth (fathoms) # tows
shallow 30-100 15
mid-depth 100-300 17
deep 300-700 10
The catch associated with the various depth strata are very different. The photographs below show typical catch from tows within each depth zone (shallow, mid-depth and deep). (Photo credits: John Buchanan)
During the second half of leg 4, the heavy seas and high winds (greater than 25 kts) subsided as we rounded Pt. Conception into the anoxic Santa Barbara basin on July 4th (see survey blog: Postcards from the Field: July 10). After an enjoyable anchorage off Goleta and UCSB, including a celebratory fireworks show, the F/V Excalibur moved offshore, outside of San Miguel Island picking up catches of sea urchins (Brisaster sp.) along with blackgill rockfish at stations in about 250 fathoms. Later, on the south side of Santa Rosa Island, Capt. Mike Retherford Sr. announced the sighting of a large shark at the surface, on the vessel’s starboard side. Further inspection revealed a ~10 ft swordfish sunning itself, likely thermoregulating after an energy-intensive vertical excursion for prey.