UNIT 24 SEA TURTLES INTRODUCTION Sea turtles are highly migratory and ply the world's oceans. Under the Endangered Species Act, all marine turtles are listed either as endangered or threatened (Table 24-1). The NMFS has authority to protect and conserve marine turtles in the seas, and the U.S. Fish and Wildlife Service maintains authority while turtles are on land. The Kemp's ridley, hawksbill, and leatherback turtles are listed as endangered throughout their ranges. The loggerhead and olive ridley turtles are listed as threatened throughout their U.S. ranges, as is the green turtle, except the Florida nesting population which is listed as endangered. SPECIES AND STATUS The Pacific species are loggerhead, green, leatherback, hawksbill, and olive ridley turtles. All are also found in the Atlantic Ocean, but the olive ridley does not commonly enter U.S. waters. In Hawaiian waters, the green and hawksbill are most abundant. Off the U.S. west coast, the loggerhead, leatherback, and olive ridley turtles are most commonly reported. Historical data on sea turtle numbers are limited. In addition, the length of time that data have been collected has been short when compared with the long life and low reproductive rate of all turtle species. It is difficult to assess the long-term status of sea turtles due to the limited data. The estimated number of female loggerheads nesting annually in the southeastern United States is about 20,000-28,000 (Table 24-1). Most nest along Florida's east coast where nest numbers have been stable for 5 years. Only about 700-800 female Kemp's ridley turtles nest annually along a limited portion of Mexico's Gulf coast. In 1947, on a single day, 40,000 females were seen nesting on one beach alone. The documented decline in the Kemp's ridley is probably indicative of similar population trends for other sea turtles, though the periods of their various declines may have differed (Fig. 24-1). Historically, the green sea turtle has supported large fisheries along the Florida and Texas coasts, although its nesting on U.S. beaches has probably always been limited. Currently, perhaps 400-500 green turtles nest annually along the Florida coast. There are no historical estimates for the numbers of hawksbill or leatherback turtles nesting on U.S. Caribbean beaches. The hawksbill has been heavily exploited, and continued trade of products from this species suggests that further declines are possible. The trend over time of the leatherback turtle in U.S. waters is unknown. Since 1973, Hawaiian surveys of green turtles indicate that the estimated number of turtles nesting annually is about 450-475, and that it is gradually increasing. No accurate historical record of this green turtle population exists. The Hawaiian hawksbill turtle population is very small; only 12-15 nests are recorded each year. In Hawaii, little is known of the species' reproductive biology or population trends. ISSUES Bycatch and Multispecies Interactions In the North Pacific there were concerns about sea turtle deaths in the recently concluded high-seas driftnet fisheries. Turtle bycatch rates were monitored on driftnet vessels by U.S., Canadian, Japanese, Korean, and Taiwanese scientific observers. The effect of these driftnet fisheries on U.S. sea turtle populations is unknown, but a moratorium on high-seas driftnet fisheries is now in place under a United Nations resolution. Turtles are also killed incidentally in various commercial fisheries. Turtles are caught and killed in pelagic longline fisheries targeting tunas and billfishes. Conservatively, as many as 11,000 sea turtles may have been killed annually in offshore shrimp trawls. Turtle mortality from inshore shrimp trawling was not estimated. Fortunately, turtle excluder devices (TED's) have been developed for shrimp and fish trawls. TED's enable turtles to escape the trawl net and prevent them from drowning. These devices reduce the turtle kill by shrimp trawls by 97% and studies indicate that the use of TED's minimally reduces shrimp catches. TED use is presently mandated for most of the Atlantic and Gulf of Mexico shrimp and summer flounder trawl fisheries. Habitat Concerns Coastal development is reducing nesting, egg incubation, and foraging habitats. Floating tar balls and plastics, if eaten, can harm or kill sea turtles. The magnitude of these problems is not fully known, but they occur worldwide, and international cooperation for marine turtle protection and recovery is required. Progress Pacific: The recovery of endangered and threatened marine turtle populations in the North Pacific will be enhanced by the United Nations-sponsored moratorium on large-scale driftnet fishing that went into effect on 1 January 1993. During 1990 and 1991, when the high-seas driftnet fisheries were carefully monitored by NMFS and cooperating foreign fishery agencies, data were collected that have led to a better understanding of the pelagic distribution and ecology of sea turtles in the North Pacific. In the Hawaii pelagic longline fishery for tuna and swordfish, the incidental catch of turtles is being closely monitored through a compulsory logbook program. A scientific observer program is being considered as a means to collect the more detailed data required to verify logbook reports and assess turtle impacts. During late 1993, a workshop was held to formulate research techniques to determine hooking and entanglement mortality of turtles incidentally caught by longline. Significant progress is being made in the monitoring of Hawaiian green turtles. In 1992, a 5-year series of saturation surveys was completed at East Island, French Frigate Shoals, the principal location of Hawaiian green turtle nesting, by NMFS and the U.S. Fish and Wildlife Service. Based on these surveys, rigorous quantitative methods have been developed for annual nesting surveys at East Island. Progress is also being made in monitoring juvenile and subadult Hawaiian green turtles in their nearshore habitat. A vigorous research program is underway to study the origins and effects of fibropapilloma tumor disease in the Hawaiian green turtle population; progress has been made in developing information relevant to potential etiologies involving cardiovascular parasites, viruses, and environmental pollutants. A similar disease situation exists among green turtles in Florida and the Caribbean. Atlantic: The joint NMFS/USFWS Atlantic Sea Turtle Recovery Plans have been developed, finalized, and approved. These plans prioritize turtle research requirements and delineate reasonable actions which are believed to be required to recover and/or protect the species. A major factor affecting the recovery of turtle populations is the mitigation of commercial fishing/sea turtle interactions. The incidental capture of sea turtles in various commercial fisheries has been studied and summarized and was the focal point of a meeting at the recent 13th Annual Sea Turtle Symposium. Recent legislation has allowed NMFS to use observers in selected fisheries to document the occurrence of incidental turtle captures. Also, several new TED models have been recently tested and approved for commercial use, and research continues on the development of a new TED design which would accommodate small inshore turtles. Considerable progress has been made concerning inshore juvenile developmental habitat research and remote sensing. NMFS research projects have been started on juvenile ridleys and greens in the Cedar Keys and Biscayne Bay, Florida, and in the northwestern Gulf of Mexico. Additionally, a comprehensive research project concerning the incidence, etiology, and epidemiology of fibropapilloma tumor disease in Atlantic green turtles has been started. Concern is growing that this disease may seriously affect the recovery of world-wide green turtle populations.