Swimmer Y.,National Oceanic and Atmospheric Administration |
Arauz R.,Programa Restauracion de Tortugas Marinas PRETOMA |
Wang J.,University of Hawaii at Manoa |
Suter J.,3162 Stevely Avenue |
And 3 more authors.
Aquatic Conservation: Marine and Freshwater Ecosystems | Year: 2010
1. This study compared the catch rates of targeted dolphinfish or mahimahi (Coryphaena hippurus), and sea turtles and other fish bycatch in a shallow-set Costa Rican longline fishery using 14/0 circle hooks with and without a 101 offset. The effect of hook offset on hooking location and injury in captured sea turtles, specifically if the hooking was external, in the mouth, or in the esophagus was also evaluated. 2. Results were compared from six trips totalling 33 876 hooks with squid (Dosidicus gigas) used as bait. In total, mahimahi catch-per-unit-effort (CPUE, expressed as number caught per 1000 hooks) was similar between hook types (CPUE~52). 3. Olive ridley sea turtles (Lepidochelys olivacea) were caught on all 42 sets. In total, 640 olive ridley turtles were caught and released alive. There were no significant differences in the number of sea turtles caught between hooks with and without an offset (CPUE ~ 19) nor between hook type and anatomical hooking location, suggesting similar levels of injury for turtles caught on each hook type. 4. These data suggest that a 101 offset on 14/0 circle hooks does not confer any selective advantages over hooks with no offset with respect to capture rates of mahimahi, sea turtles, sharks, or pelagic stingrays in a shallow set pelagic longline fishery. Copyright © 2010 John Wiley & Sons, Ltd.
Dapp D.,Drexel University |
Arauz R.,Programa Restauracion de Tortugas Marinas Pretoma |
Spotila J.R.,Drexel University |
O'Connor M.P.,Drexel University
Journal of Experimental Marine Biology and Ecology | Year: 2013
We used data collected by an observer program to assess the impact of the Costa Rican longline fishery on numbers, capture locations, seasonality and body sizes of silky sharks (Carcharhinus falciformis), pelagic thresher sharks (Alopias pelagicus), olive ridley turtles (Lepidochelys olivacea) and other bycatch species in the Central American Pacific. The longline fishery caught a large number of mahi-mahi (Coryphaena sp.) and silky sharks, but also caught a large number of olive ridley turtles and pelagic stingrays (Pteroplatytrygon violacea). We estimated that longline fisheries caught 699,600 olive ridleys, including 92,300 adult females, from 1999 to 2010. These captures were associated with a decline of nesting populations at nearby arribada beaches. There were statistically significant size decreases from 1999 to 2010 in mature olive ridley turtles and from 2003 to 2010 in silky sharks. Average fork length of silky sharks in 2010 was 97.3. cm, which was far below observed fork length at maturity, 144. cm. Pelagic thresher sharks were small and fluctuated in size over the study period. Capture of large numbers of juvenile blacktip sharks (Carcharhinus limbatus) indicated a nursery area near the Osa Peninsula. Geospatial analysis indicated shifts in mahi-mahi abundance on a temporal scale but fishing efforts did not shift with the shift in mahi-mahi abundance. Yellowfin tuna (Thunnus albacares), Indo-Pacific blue marlin (Makaira mazara) and Indo-Pacific sailfish (Istiophorus platypterus) catches varied seasonally and were most abundant out to sea and south of Panama. Marine protected areas and/or time area closures are needed to reduce the impact of the Costa Rican longline fishery on sea turtles and sharks. © 2013 Elsevier B.V.