Silky Sharks caught by Japanese Longliners in Eastern Pacific Ocean
Publication year 2011
Estimate of catch for silky shark (Carcharhinus falciformis) caught by Japanese longline vessel in the EPO from 2000 and 2010.
Yasuko Semba
SUMMARY:
This is the first report of catch estimated for silky shark (Carcharhinus falciformis) caught by Japanese longline fishery operating in the EPO. Silky shark is distributed in the tropical waters and abundant in offshore, pelagic and littoral areas (Compagno 1984). This species has been treated as bycatch in Japanese longline vessel operating in the EPO and the catch number (or weight) of this species has been combined with other sharks and recorded as “sharks” until 1993. Japan developed a new log-book reporting system in the longline fishery to record the catch of sharks in 6 categories (blue shark, shortfin mako, porbeagle/salmon shark, oceanic whitetip shark, thresher sharks, and other sharks) in 1997. In logbook system, this species is included in the “other sharks”, which combines the species with some commercial value. Silky shark is utilized for human consumption in various areas (Compagno 1984) and the record of fishery training vessels in Japan indicates that silky shark has been utilized to some extent, which suggests that this species has some value to commercial longline vessels, too. To estimate the catch of silky shark from aggregated catch of “other sharks”, we checked the species composition of sharks reported by training vessels conducting tuna longline operation in the EPO. By applying the ratio of silky shark in the catch of “other shark with some commercial value” (i.e. other than 5 categories indicated above), the catch number of silky sharks by Japanese commercial longline vessels operating in the EPO was estimated from 2000 and 2010.
IATTC – 3rd Technical meeting on sharks – December, 2011 – La Jolla, California, USA