Monster Seminar JAM - Demersal Fishes of the Southern California Shelf and Upper Slope: Populations, Communities, and Responses to Environmental Changes
Dr. James M. Allen, Southern California Coastal Water Research Project.
Although southern California demersal (soft-bottom) fish populations have not been a focus of large commercial fisheries, they have been studied extensively during the past three decades to assess the effects of anthropogenic pollution. In contrast to fisheries surveys on much of the West Coast which usually use large commercial trawl nets (e.g., 27-m wide) towed for about 30 min, surveys in southern California have used small (7.6-m wide nets) towed for 10 min (using standardized protocol developed in the early 1970s). These studies have been focused on assessment of effects of local deepwater wastewater discharge, with a number of regional surveys of the Southern California Bight (SCB) The SCB is defined by sharp indentation of the coast, which results in an oceanographic region that is distinct from the Central California coast. It has warmer waters in the main part of the SCB and has a relatively narrow (~2.2 km wide) coastal shelf. The fish fauna (consisting of about 150 soft-bottom species) lies at the interface between cold- and warm-temperate faunas, with the former being more important in deeper offshore waters and cold regimes and the latter being important in the main part of the SCB and in warm regimes. Populations vary spatially more by depth than by region, with relatively distinct faunas on the inner shelf (5-30 m), middle shelf (31-100 m), outer shelf (101-200 m), and upper slope (201-500 m). Communities consist of representatives of about 18 different feeding guilds, with different species representing a guild at different depths. Populations and communities have changed during the past three decades, largely in response to natural changes in oceanic conditions and in particular to the Pacific decadal oscillation (the cycle of cold and warm regimes). More species show a negative relationship (more abundant in the cold regime) than a positive relationship (more abundant in the warm regime). The occurrence upwellin
Date and Time:
October 23, 2003,
11:00 am - 12:30 pm