On September 13-15, the Fisheries Ecology Division (FED) hosted the NMFS/Pacific Fishery Management Council Groundfish Pre-Recruit Survey Workshop. The workshop addressed two major themes: 1) Developing a coast-wide survey of groundfish pre-recruit abundance, and 2) Incorporating pre-recruit indices in stock assessments.
The midwater trawl surveys for juvenile rockfish and juvenile whiting conducted by the SWFSC/FED (Southern California to Cape Mendocino) and the Pacific Whiting Conservation Cooperative with NWFSC funding (Central California to Washington State) now cover the entire US West Coast, and provide the necessary geographic coverage to detect and understand recruitment events. Protocols and performance of the two surveys is sufficiently similar that they can be combined; minor changes were suggested to improve their comparability.
At present, we have only three years of full West Coast coverage, so it is too early to determine the precision of the recruitment indices -- the year-classes have not yet appeared as recruits to the fisheries. However, we have already obtained several useful insights into stock structure and patterns of environmental influence on recruitment. In the case of rockfish, the pre-settlement pelagic juvenile surveys are conducted at a life stage when relative year-class strength has already been determined through density independent processes, but density dependent compensation (which occurs post-settlement) has not yet occurred. This poses unusual problems for their use in stock assessments, necessitating an explicit separation of early life stage processes in the assessment models. (September 19, 2006)