Impact of Costa Rican longline fishery on its bycatch of sharks, stingrays, bony fish and olive ridley turtles (Lepidochelys olivacea)

• Published in: Journal of experimental marine biology and ecology 2013-10, Vol.448, p.228-239
• Main Authors: Dapp, Derek, Arauz, Randall, Spotila, James R., O'Connor, Michael P.
• Format: Article
• Language: English
• Subjects: Agnatha. Pisces; Alopias pelagicus; Amphibia. Reptilia; Animal and plant ecology; Animal, plant and microbial ecology; Applied ecology; Biological and medical sciences; Carcharhinus falciformis; Carcharhinus limbatus; Coryphaena; Dasyatidae; Exploitation and management of natural biological resources (hunting, fishing and exploited populations survey, etc.); Fundamental and applied biological sciences. Psychology; Geospatial analysis; Istiophorus platypterus; Lepidochelys olivacea; Longline fishery; Makaira mazara; Marine; Marine conservation; Marine protected areas; Observer program; Populations; Pteroplatytrygon violacea; Sea water ecosystems; Synecology; Thunnus albacares; Vertebrates: general zoology, morphology, phylogeny, systematics, cytogenetics, geographical distribution
• ISSN: 0022-0981; 1879-1697
• DOI: 10.1016/j.jembe.2013.07.014

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 97.3cm, which was far below observed fork length at maturity, 144cm. 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. •We assessed effect of Costa Rica longline fishery on fish and sea turtles.•It caught many mahi-mahi, silky sharks, pelagic stingrays and blacktip sharks.•Longlines caught 699,600 olive ridleys, including 92,300 adult females.•Turtle nesting populations declined at nearby arribada beaches during this time.•Marine protected areas and time area closures will protect sea turtles and sharks.