Annual West Coast Midwater Trawl Survey Completed

Fisheries Ecology Division,

The SWFSC Fisheries Ecology Division in Santa Cruz has conducted a midwater trawl survey during May-June every year since 1983. Originally the survey was designed to estimate the distribution and abundance of young-of-the-year (YOY) rockfishes (Sebastes spp.) and to develop indices of pre-recruit CPUE (catch per unit effort) that could be incorporated into groundfish stock assessments conducted for the Pacific Fishery Management Council. The survey has expanded its focus to include characterization of the epipelagic micronekton community inhabiting continental shelf and slope waters along the central California coast. In addition, the survey greatly expanded its geographical coverage in 2004 to include the region between the Mexican border and Cape Mendocino and, when coupled with a similar survey executed by the NWFSC, forms the backbone of a complete west coast fishery-independent survey of YOY groundfish reproductive success.

This year the midwater trawl survey was completed when the NOAA R/V Miller Freeman arrived in San Francisco, CA on June 25, 2009. Use of the Miller Freeman this year, as opposed to the R/V David Starr Jordan, resulted in very good success in trawling under adverse weather conditions. In addition to trawl sampling, hydroacoustic and Tucker trawl data were collected to map the distribution of krill species (Euphausia pacifica and Thysanoessa spinifera), hydrographic data were gathered using a CTD equipped with a variety of instruments (fluorometer, O2 sensor, transmissometer, etc.), and sea bird and marine mammal sightings were recorded using strip transect methods. By the end of the cruise well over 4,000 YOY rockfish were collected, representing a very good catch. Rockfish juveniles have also been observed settling in nearshore habitats, which bodes well for the 2009 year class.

(July 6, 2009)

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