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Marine Turtle Newsletter 76:12-14, © 1997

PACIFIC LEATHERBACK POSTSCRIPT

Sarti et al., after documenting the severity and rate of decline in the population of leatherback turtles nesting on the Pacific coast of México, attributed the decline to uncontrolled domestic harvest and the high-seas driftnet fisheries of the 1980's. While this is undoubtedly true, it is also true that the Government of México, local and national conservation groups, and hundreds of volunteers have been working to reduce the domestic harvest, especially since 1990 when marine turtles were granted the full protection of law in México. Moreover, the United Nations ban on high-seas driftnets became effective in December 1992. Many readers are aware of these national and international management changes, and therefore may conclude that, as bad as things look from the Sarti et al. report, the major threats have been effectively addressed and, thus, the long term outlook for the population's recovery is good.

Unfortunately, nothing could be farther from the truth. In recent years there has been a proliferation of longline fisheries in the Pacific (and elsewhere), probably due to the ready availability of monofilament lines, coupled with the need to find an alternative to driftnetting for species such as tuna, swordfish and various species of sharks. The highest turtle takes reported in longline fisheries appear to be loggerheads, Caretta caretta (Aguilar et al., 1992; Nishemura and Nakahigashi, 1990), but observer data from the Hawaii (U.S. Pacific) longline fishery confirm that leatherbacks are also taken, and killed, in longline fisheries. For example, estimated captures, and mortality, of leatherbacks in this fishery for the 1994-1995 fishing season were 178 and 21 respectively; these included both juvenile and adult turtles (Bolten et al., 1996).

A recent attempt at estimating the mortality the combined Costa Rican (also declining) and Mexican leatherback populations could withstand without further harm concluded that perhaps 12 adults could be killed in total, by all human-caused mortality factors to the combined populations, without further significant harm to the nesting populations (Gerrodette, 1996). These calculations are extremely preliminary (using a technique derived for marine mammals, not turtles), and only address adults, while many of the turtles taken are immature. Moreover, there are many human-caused mortality factors in addition to the Hawaiian longline fishery, including several much larger Pacific longline fisheries, and longline fisheries are growing rapidly. As Gerrodette says, "If loggerhead and leatherback populations are in fact declining at 20% per year, this is prima facie evidence that mortality is already too high, whether it is from bycatch or other sources." Clearly, there is no room for complacency regarding the future of Pacific leatherbacks. ... We all know the fate of the once major nesting colony in Malaysia.

The U. S. National Marine Fisheries Service (NMFS) recently decided to reopen consultation under the Endangered Species Act (ESA) on the Hawaii longline fishery with regard to both loggerheads and leatherbacks. The observer data suggest that changes in time of day, use of light sticks, length of leaders, target species, and other factors may affect turtle catch rates in longline fisheries. MTN readers resident in the U. S. should remind NMFS that federal agencies have affirmative duties under Section 7 of the ESA to conserve endangered and threatened species under the ESA, and the Hawaii longline fishery is clearly a place where such conservation is necessary and appropriate. [ To comment to NMFS, write: Hilda Diaz-Soltero, Director, NMFS Southwest Regional Office, 501 W. Ocean Blvd., Suite 4200, Long Beach, California 90802 USA. ] Likewise, readers from other countries with Pacific longline fisheries should encourage data collection on incidental catch, research into gear modifications with an aim to reduce bycatch, and other conservation measures within their longline fisheries.

Aguilar, R., J. Mas and X. Pastor. 1992. Impact of Spanish swordfish longline fisheries on the loggerhead sea turtle, Caretta caretta, population in the western Mediterranean, p.1-6. In: J. I. Richardson and T. H. Richardson (Editors), Proc. Twelfth Annual Workshop on Sea Turtle Biology and Conservation. NOAA Tech. Memo. NMFS-SEFSC-361. U. S. Dept. Commerce.

Bolten, A. B., J. A. Weatherall, G. H. Balazs and S. G. Pooley (Editors). 1996. Status of Marine Turtle in the Pacific Ocean Relevant to Incidental Take in the Hawaii-based Pelagic Longline Fishery. NOAA Tech. Memo. NMFS-SWFSC-230. U. S. Dept. Commerce.

Gerrodette, T. 1996. Estimation of allowable loggerhead and leatherback turtle mortality in the North Pacific Ocean by Potential Biological Removal (PBR) Calculation, p.99-104. In: A. B. Bolten, J. A. Weatherall, G. H. Balazs and S. G. Pooley (Editors), Status of Marine Turtles in the Pacific Ocean Relevant to Incidental Take in the Hawaii-based Pelagic Longline Fishery. NOAA Tech. Memo. NMFS-SWFSC-230. U. S. Dept. Commerce.

Nishemura, W. and S. Nakahigashi. 1990. Incidental capture of sea turtles by Japanese research and training vessels: results of a questionnaire. Marine Turtle Newsletter 51:1-4. Sarti M., L., S. A. Eckert, N. Garcia T. and A. R. Barragan. 1996. Decline of the world's largest nesting assemblage of leatherback turtles. Marine Turtle Newsletter 74:2-4.

DEBORAH CROUSE, Center for Marine Conservation, 1725 DeSales Street N.W., Suite 600, Washington, D. C. 20036 USA.