Just how depleted are leatherback populations? And will the injunction imposed on the Hawai’i longline fleet by U.S. District Judge David A. Ezra help leatherbacks at all?
The first question is easier to answer.
Pamela Plotkin is generally regarded as an expert on leatherback populations. In 1994, as a National Marine Fisheries Service scientist, she co-authored the biological opinion on the impact of the longline fishery on sea turtles and has since then been co-author of other scientific articles on the worldwide decline of leatherback populations.
Since publication of an article she coauthored in 1996 on the worldwide decline of leatherbacks, the status of Pacific leatherback populations is “much worse now, … The nesting population in Malaysia is ‘biologically extinct’ with only two leatherbacks nesting there today,” she stated in an affidavit presented to Judge Ezra, who heard the lawsuit brought by conservation groups against NMFS over the ongoing take of sea turtles by the Hawai’i-based longline fleet.
“In the last four years we have witnessed population declines on east Pacific beaches similar to the population collapse experienced in Malaysia The Mexican nesting population is now down to only 250 leatherbacks. The nesting population at Playa Crande, Costa Rica, declined from an estimated 800-1,000 turtles in the early 1990s to only 122 turtles during the 1998-1999 nesting season. The continued existence of Pacific leatherbacks is in jeopardy and if action is not taken immediately to reduce the incidental mortality of leatherbacks in fisheries, they will disappear from the Pacific Ocean in the next few years.”
Plotkin said NMFS “made a serious error when they estimated the number of Pacific leatherbacks for their 1998 biological opinion.” The NMFS estimate of 85,000 subadult and adult Pacific leatherbacks was incorrect, bur formed the basis of population modeling NMFS developed to describe the impact of fishing on the turtles. “The actual number of pacific leatherbacks was much lower at that time, and is now even lower. If the actual population size of leatherbacks had been used in the… model NMFS would have issued a jeopardy opinion.
‘Grave Concern’
Other global experts on turtles weighed in on the subject, with a letter to Judge David A. Ezra that expressed their own concerns over continuing declines in leatherback populations. The letter, dated October 27,1999, was signed by Scott Eckert, Karen Eckert, Richard Byles, Frank Paladino, and James Spotila -all scientists whose expertise has been relied upon by NMFS in preparation of past biological opinions on the effect of the longline fleet on turtle populations.
They wrote “to express our grave concern about the status and continued existence of Pacific Ocean populations of the leatherbacks sea turtle… Pacific leatherback populations in particular have declined precipitously in the last decade and we believe the situation today is critical. Published estimates of more than 75,000 leatherbacks nesting on the Pacific coast of Mexico in the early 1980s stand in stark contrast to recent surveys demonstrating that by 1996 there were approximately 6,476 leatherbacks nesting along the entire Pacific coast of the Americas (Mexico to Colombia). Last year there were approximately 3,719 nesting leatherbacks.
“Many previously large Pacific leather-back nesting colonies already have been lost or have declined dramatically. For example, the nesting population in Malaysia declined from approximately 3,000 turtles in the late 1960s to only 2 turtles in 1994. In Costa Rica the nesting population has declined from 800 – 1,000 turtles in the early to mid 1990s to only 166 turtles per season averaged over the past 2 years. In Mexico the nesting population has declined from 897 turtles in 1995 to only 250 turtles in 1998.”
Declines in the Mexican and Costa Rican nesting colonies (22 percent and 34 percent, respectively) “represent the fastest ever recorded for any sea turtle species.”
“We believe the incidental mortality of leatherbacks caused by commercial fishing pressure is primarily to blame for this precipitous drop in the number of reproductively active adults,” they wrote. The National Marine Fisheries Service has, they went on to say, “recognized the incidental take of leatherbacks in the Hawaiian longline fishery as a ‘major problem”‘ in its recovery plan for U.S. Pacific Populations of the Leatherback Turtle (1998).
“It is now almost year 2000 and significant action to reduce incidental take of leather-backs by the Hawaiian longline fishery, one of the most severe threats to the population that NMFS has recognized in their own reports, has not occurred. In fact, take levels of leatherbacks allowed by NMFS for the fishery have increased.”
Charles Karnella, administrator of NMFS Pacific Islands Area Office in Honolulu, does not necessarily disagree with the scientists’ assessment of the leatherback’s plight. Yet be does not hold out great hope that the Injunction will provide much relief for the leatherbacks. The observed interactions of fishing vessels with turtles, displayed on the accompanying map, seem to bear out Karnellas view.
“Fortunately or unfortunately,” Karnella told Environment Hawaii, “the loggerhead turtles are the ones that are most concentrated in those northern waters” closed by Judge Ezra to Hawai’i longliners. “The take of leatherbacks has a wider geographic distribution by far than that of loggerheads.”
“It maybe true to say that the leatherback population is undergoing some kind of crash,” he added, “but I’m having a difficult time relating it to this fishery. If the numbers are anywhere near what scientists are saying they are, they’re not pinpointing the cause. Let’s say we prohibit our fishermen from fishing, for the sake of argument. One of the things our scientists have come up with is that for the leatherback populations, we’ll never know the difference.”
What is, then, causing the leatherback populations to decline so precipitously?
In the 1998 NMFS biological opinion, egg poaching is identified as one of the main causes of population declines. The collapse of nesting populations in Mexiquillo, Mexico from mid-1980s on “was precipitated by a tremendous over-harvest of eggs coupled with incidental mortality from fishing.”
And similarly with respect to the Malaysian population of leatherbacks, where current nestings [represent] 1 percent of the levels recorded in the 1950s. Years of excessive egg harvest, egg poaching, the direct harvest of adults in this area as well as incidental capture in various fisheries in territorial and international waters has impacted the Malaysia population of leatherbacks,” the biological opinion says.
Until the drift net fishery was banned in 1992, it took leatherbacks by the hundreds. “The Japanese high seas squid driftnet fishery in the North Pacific is estimated to have taken 222 leatherbacks in 1989 and 300 leatherbacks in 1990,” the biological opinion states.
Other U.S.-based fishing fleets besides that in Hawai’i take leatherbacks, but, according to the biological opinion, the numbers taken ate lower than those taken by the Hawai’i fleet. The California swordfish and drill gillnet fishery was estimated to have killed 26 leatherbacks in 1995, for example, while the California set gillnet fishery for halibut is thought to have resulted in eight leatherback deaths in 1994.
“Hawai’i Longline Fleet Takes Toll on Endangered, Threatened Sea Turtles,” Environment Hawai`i, April 1994, cover article.
“Fishermen Object to Paying Cost of Program to Monitor Turtle Harm,” Environment Hawai’i, October 1995, cover article.
“NMFS Increases Turtle Takings Allowed for Hawai’i Longline Fleet,” Environment Hawai’i, December 1998, cover article.
— Patricia Tummons
Volume 10, Number 7 January 2000
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