Weise and Harvey: Impact of Zalophus ca/iformanus on salmon fisheries 



689 



numbers of observed takes (based on dockside samples) 

 and proportions of the total catch sampled. 



Estimates of lost and damaged gear were calculated 

 by using average costs for each type of gear used in 

 commercial and recreational salmon fishing operations. 

 A survey of the seven local retail fishing tackle stores in 

 Santa Cruz, Moss Landing, and Monterey was used to 

 estimate mean value of each type of fishing gear used 

 in the recreational (CPFV and skiff combined) salmon 

 fishery. All charter-fishing companies in the three ports 

 in Monterey Bay were surveyed to estimate mean cost 

 of a "setup" sold by charter boat companies to custom- 

 ers. A "setup" was defined as a hook and leader, or a 

 hook, leader, and a 4 oz. or 8 oz. lead sinker. Costs of 

 commercial fishing gear were estimated by surveying 19 

 local fishermen from the three ports in Monterey Bay. 

 Commercial fishermen buy the majority of their gear in 

 bulk, and often by mail order to reduce costs. 



Results 



From 1997 to 1999. 1745 hours of onboard surveys and 

 dockside interviews were conducted in the commercial 

 and recreational salmon fisheries. In 1997, 337 hours 

 of onboard and dockside surveys were conducted, 144 

 hours in the commercial fishery, 103 hours in the CPFV 

 fishery, and 90 hours in the skiff fishery. In 1998, 704 

 hours of onboard and dockside surveys were conducted: 

 370 hours in the commercial fishery, 270 hours in the 

 CPFV fishery, and 64 hours in the skiff fishery. During 

 1999, 704 hours of onboard and dockside surveys were 

 conducted, 410 hours in the commercial fishery, 258 

 hours in the CPFV fishery, and 36 hours in the skiff 

 fishery. Increased sampling effort in 1998 and 1999 

 were the result of increased onboard survey effort in 

 the commercial and CPFV fisheries. 



During this study 101 onboard surveys and 2780 

 dockside interviews (number of boats sampled) were 

 conducted in the commercial and recreational salmon 

 fisheries. There were no significant differences in mean 

 percentages of fish taken by sea lions between onboard 

 and dockside surveys in the commercial (1997, P=0.329; 

 1998, P=0.623; 1999, P=0.653), CPFV (1997, P=0.276; 

 1998, P=0.660; 1999, P=0.327) and skiff fisheries (1997, 

 P=0.052; Fig. 2). We assumed, therefore, that dockside 

 surveys provided a representative measure of pinniped 

 takes in the salmon fisheries and onboard survey data 

 were pooled with dockside interview data for subsequent 

 analysis. 



A total of 967 interviews with commercial fishermen 

 and 1813 interviews with recreational fishermen were 

 were conducted at dockside in Monterey Bay, account- 

 ing for 41,895 and 15,115 hooked salmon, respectively 

 (Table 2). In the commercial fishery a similar number 

 of interviews were conducted in 1997 and 1998, whereas 

 in 1999 approximately 21.2% greater numbers of inter- 

 views were conducted with the same effort. However, 

 the number of fish landed in 1999 was significantly less 

 than in 1997 and 1998. In the CPFV fishery, the trend 



was similar to the commercial fishery, but the number 

 of fish landed and the number of boats surveyed was 

 significantly fewer overall. In the skiff fishery, there was 

 a steady decline in the number of fishermen surveyed 

 and the number of fish landed from 1997 to 1999. 



Onboard observations combined with dockside inter- 

 views revealed that California sea lions were almost 

 exclusively responsible for the depredation of hooked 

 salmon in the commercial and recreational fisheries 

 in Monterey Bay, taking 98.4% of the 1199 observed 

 hooked salmon from 1997 to 1999. Of the estimated 

 2420 takes in 1997, 1072 were directly observed surface 

 takes and sea lions were identified in 98.6% of the takes 

 (Table 2). In 1998, approximately 501 of 5542 takes 



