Examination of early life history stages and their contribution toward establishing year-class strength can be useful in the fisheries management process. The SWFSC Fisheries Ecology Division's Groundfish Analysis Team has been conducting annual surveys off California in order to provide an index of recruitment strength for pelagic juvenile rockfish (Sebastes spp.). Other important species collected by the survey include juvenile and adult Pacific whiting (Merluccius productus), juvenile lingcod (Ophiodon elongatus), northern anchovy (Engraulis mordax), Pacific sardine (Sardinops sagax), market squid (Loligo opalescens), and krill (Euphausiacea) as well as mesopelagic species such as myctophids (Myctophidae). In addition to abundance data, size information is also collected on species of interest. Genetic tissue samples and otoliths (used for daily aging) are also collected from the pelagic juvenile rockfish.
The survey began in 1983 sampling along the central California coast from Monterey Bay to Point Reyes. In 2004 the survey area was expanded to encompass nearly the entire coast of California from San Diego to Point Delgada. Sampling period is in late spring (May-June), a time when the juveniles of many species of rockfish are still pelagic and have not yet settled to nearshore and benthic habitats. The first 16 years of the survey were conducted aboard the NOAA Ship DAVID STARR JORDAN. However, in 2008 this vessel was retired and since then a combination of NOAA Ships and contract vessels has been used for the survey while the SWFSC awaits the arrival of their new NOAA research vessel (replacement for the NOAA Ship DAVID STARR JORDAN). A modified Cobb midwater trawl with a 26 m headrope and 9.5 mm codend mesh is towed at night (2100 to 0600 hr) for 15 minutes at a target headrope depth of 30 m. Beginning in 1987 conductivity, temperature, and depth (CTD) casts were added to the survey to obtain oceanographic data. Over the years additional sensors have been added to the CTD including a fluorometer to measure chlorophyll, a PAR sensor and transmissometer to measure light levels and turbidity, and a dissolved oxygen sensor.
Additional data sources from the survey include marine mammal and seabird counts (starting in 1985), multi-beam acoustic sensor data used to map the distribution and abundance of krill (starting in 2000), and rod and reel collection of Humboldt squid (Dosidicus gigas) (starting in 2007). Marine mammal and seabird counts are recorded by biologists from Point Blue Conservation Science and the Farallon Institute for Advanced Ecosystem Research. Integration of multi-beam acoustic data with the krill catch data from the midwater trawls and the CTD data yields an informative overview of one of the key species that drives the ecosystem off the west coast. Data collected on Humboldt squid include feeding habits, age and growth, and population genetics.
The variety of data collected aboard the survey (e.g., catch data, acoustic data, and hydrographic data) can be used not only to examine recruitment strength of various economically and ecologically important species, but also to study the general state of the ecosystem and its variability from year to year.
Point Blue Conservation Science
(formerly Point Reyes Bird Observatory / PRBO Conservation Science)
Farallon Institute for Advanced Ecosystem Research
Contact: SWFSC Fisheries Ecology Division, Groundfish Analysis Team