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- Impact of the California sea lion (Zalophus californianus) on salmon fisheries in Monterey Bay, California,
- To assess the impact of California sea lions (Zalophus californianus) on salmon fisheries in the Monterey Bay region of California, the percentages of hooked fish taken by sea lions in commercial and recreational salmon fisheries were estimated from 1997 to 1999. Onboard surveys of sea lion interactions with the commercial and recreational fisheries and dockside interviews with fishermen after their return to port were conducted in the ports of Santa Cruz, Moss Landing, and Monterey. Approximately 1745 hours of onboard and dockside surveys were conducted - 924 hours in the commercial fishery and 821 hours in the recreational fishery (commercial passenger fishing vessels [CPFVs] and personal skiffs combined). Adult male California sea lions were responsible for 98.4% of the observed depredations of hooked salmon in the commercial and recreational fisheries in Monterey Bay. Mean annual percentages of hooked salmon taken by sea lions ranged from 8.5% to 28.6% in the commercial fishery, 2.2% to 18.36% in the CPFVs, and 4.0% to 17.5% in the personal skiff fishery. Depredation levels in the commercial and recreational salmon fisheries were greatest in 1998 - likely a result of the large El Niño Southern Oscillation (ENSO) event that occurred from 1997 to 1998 that reduced natural prey resources. Commercial fishermen lost an estimated $18,031-$60,570 of gear and $225,833-$498,076 worth of salmon as a result of interactions with sea lions. Approximately 1.4-6.2% of the available salmon population was removed from the system as a result of sea lion interactions with the fishery. Assessing the impact of a growing sea lion population on fisheries stocks is difficult, but may be necessary for effective fisheries management., Cited By (since 1996):9, CODEN: FSYBA, ,
- Weise, Harvey
- Temporal variability in ocean climate and California sea lion diet and biomass consumption: Implications for fisheries management,
- Key to understanding ecosystem structure and function in the California Current System is quantitative modeling of trophic interactions of California sea lions Zalophus californianus, one of the largest and most abundant predators in this system, and how these interactions are affected by climate variability. Because sea lions consume almost exclusively commercially important prey species, we hypothesized that the potential for competition for specific prey resources would vary with environmental conditions. We evaluated seasonal and annual variation in sea lion diet in Monterey Bay during the strong 1997-98 El Niño and subsequent 1999 La Niña through the examination and identification of prey hard parts found in fecal samples. Annual consumption was modeled using population size, dietary data, sea lion energetics, and prey energy content. Sea lions were plastic specialists, feeding on seasonally abundant aggregating prey, exploiting several species at a time. Short-term seasonal changes in diet corresponded with prey movement and life history patterns, whereas long-term annual changes corresponded with large-scale ocean climate shifts, namely the large 1997-98 El Niño and 1999 La Niña. Annual sea lion consumption of specific prey varied as a function of ocean climate, with an estimated 17 154 t prey consumed in 1998 and 20 229 t in 1999. Sea lion consumption was similar in magnitude to fisheries landings for several prey species and has the potential to adversely impact specific prey resources and directly compete with these fisheries; however, the degree of competition depends on spatial and temporal overlap of fisheries and sea lion foraging efforts. © Inter-Research 2008., Cited By (since 1996):8, Marine Mammals, Birds & Turtles, CODEN: MESED, , , Downloaded from: http://www.int-res.com/abstracts/meps/v373/p157-172/ (16 June 2014).
- Weise, Harvey