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Fishery Bulletin 103(4) 



al. 3 ), and an additional 45,000-54,000 animals along 

 Baja, Mexico (Aurioles-Gamboa and Zavala-Gonzalez, 

 1994). In the Monterey Bay region, sea lions do not 

 breed but several important resting sites exist with a 

 range of 3000 to 7500 animals during the nonbreed- 

 ing season (Weise, 2000). In contrast to increases in 

 numbers of sea lions, serious declines in salmonid popu- 

 lations have occurred in recent years as a result of 

 changes and degradation in riverine habitat, declines 

 in water quality, overharvesting, changes in oceanic 

 conditions, and the development of hydroelectric power 

 systems that obstruct major riverine migration routes. 



Chinook salmon (Oncorhynchus tshawytscha) stocks 

 in the Central Valley of California probably represent 

 85% to 95% of the chinook salmon catches south of Pt. 

 Arena and in Monterey Bay (PFMC 4 ). Central Valley 

 chinook originate in the Sacramento River and San 

 Joaquin River and have four distinct runs (portion of 

 a salmon stock that returns to their native streams 

 to spawn during a specific season): fall, late-fall, win- 

 ter, and spring. Fall and late-fall runs are relatively 

 healthy, but winter and spring runs are listed as en- 

 dangered under the Endangered Species Act (ESA). 

 Salmon landed in Monterey Bay during the summer 

 fishing season are predominantly fall and late-fall run 

 Central Valley chinook salmon. Size limits and seasonal 

 restrictions are set to reduce retention of listed winter 

 run Central Valley chinook and Klamath River stocks 

 (PFMC 4 ). By taking hooked fish, sea lions can affect 

 salmon stocks because commercial and recreational 

 fishermen continue to fish for salmon to replace those 

 taken by sea lion and this activity of predation and 

 compensatory fishing leads to greater numbers of fish 

 being removed from the population. In the ocean com- 

 mercial troll and recreational salmon fishery, sea lions 

 will swim near or follow fishing boats and will depre- 

 date fish once hooked. 



Consumption of hooked salmon by sea lions may not 

 only impact salmonid stocks but impact the economic vi- 

 ability of fisheries. Recreational and commercial salmon 

 fishing is an important social and economic asset in 

 California, representing $28,856,000 in revenues in 

 1995 (PFMC 5 ). Concern over declining salmonid stocks 

 has resulted in adjustments of fishing regulations, such 

 as allocation of harvest between ocean and inland user 

 groups, harvest quotas, and time and area closures 

 (Beeson and Hanan 1 ). Increasing losses offish to Cali- 

 fornia sea lions may produce further restrictions for the 

 recreational and commercial salmon fisheries. 



4 PFMC (Pacific Fisheries Management Council). 1999. Re- 

 view of 1998 ocean salmon fisheries. NOAA Award No. 

 NA97FC0031, sections A1-A50 and Bl-43. Pacific Fisher- 

 ies Management Council, 7700 NE Ambassador Place, Suite 

 200, Portland, OR 97220-1384. 



5 PFMC (Pacific Fisheries Management Council). 1995. Re- 

 view of 1994 ocean salmon fisheries. NOAA No. NA57FC0007, 

 sections A1-A50 and B1-B43. Pacific Fisheries Management 

 Council, 7700 NE Ambassador Place, Suite 200, Portland, 

 OR 97220-1384. 



During the last several decades only a few research- 

 ers have attempted to quantify the impact of sea lions 

 on fisheries in California waters and, more specifical- 

 ly, the Monterey Bay region. According to Beeson and 

 Hanan, 1 the recreational ocean salmon landings in 1995 

 were greatest in Monterey Bay and San Francisco areas 

 and experienced the greatest amount of sea lion preda- 

 tion (charter passenger fishing vessels and private skiff 

 combined). In our study, we surveyed salmon fisheries 

 in Monterey Bay because of the particularly high rates 

 of interactions with sea lions (Beeson and Hanan 1 ) in 

 an effort to better understand the nature and extent of 

 these interactions in the commercial and recreational 

 fisheries. 



The purpose of this study was to estimate the per- 

 centage of salmon taken by California sea lions from 

 commercial and recreational salmon fisheries in Mon- 

 terey Bay from 1997 to 1999. We hypothesized that 

 the percentages of fish taken by California sea lions 

 in salmon fisheries would be greater than those taken 

 in previous years and would be part of an increasing 

 trend in sea lion and fisheries interactions paralleling 

 the growth of the sea lion population. Further, we esti- 

 mated the number of fish removed from the California 

 Central Valley chinook stock from observed percent- 

 ages of fish taken by sea lions in fisheries. Lastly, we 

 estimated the monetary losses associated with sea lions 

 interacting with commercial and recreational salmon 

 fisheries in Monterey Bay from 1997 to 1999 by quan- 

 tifying the value of fish lost and the type and amount 

 of gear lost or damaged. 



Methods 



From 1997 to 1999, observations of interactions between 

 pinnipeds and salmon fisheries were conducted onboard 

 boats, and interviews with fishermen were performed 

 at dockside at the three major ports in the Monterey 

 Bay region: Santa Cruz, Moss Landing, and Monterey 

 (Fig. 1). Salmon fishing operations included commercial 

 troll fishery and recreational fisheries consisting of com- 

 mercial passenger fishing vessels (CPFVs) and private 

 skiffs. The timing of the commercial and recreational 

 salmon fishery seasons varied each year of the study, 

 and sampling was conducted from the beginning to the 

 end of each season (Table 1). The commercial troll fish- 

 ery included day boats (i.e., a one-day fishing trip) and 

 multiple-day boats. Fishing areas included in our study 

 ranged from Pt. Sur north to Ano Nuevo Island. Data 

 regarding fisheries interactions collected at the three 

 different ports were pooled because fishermen from all 

 three ports often fish as a fleet. 



Dockside surveys were conducted to achieve a greater 

 sampling effort than could be obtained from onboard 

 observations alone. Onboard surveys were conducted 

 to test reliability of dockside surveys and to ensure 

 that investigators fully understood the nature of the 

 interaction. Small biases have occurred when combining 

 onboard and dockside surveys but were attributed to 



