When people in Hawai’i think of sea turtles, the green turtle usually comes to mind. That is the type of turtle most frequently seen in Hawaiian waters. The hawksbill is the other species of turtle found off Hawaiian coasts, although it is far rarer than the green turtle.
But these species represent just two of the five species of seaturtles are affected by longline fishing in the Pacific Ocean. Among the reported interactions between longliners and turtles in 1992, half involved leatherbacks. Most of the remainder are thought to be loggerheads. Here are brief descriptions of the turtle species affected by the longline boats.
Green turtle (Chelonia mydas). These turtles, listed as threatened under the federal Endangered Species Act, are the ones most frequently seen around the Main Hawaiian Islands. At least 90 percent of all female green turtles in Hawai’i nest at French Frigate Shoals in the northwestern Hawaiian Islands. The remaining 10 percent nest at Laysan and Lisianski islands, and at Pearl and Hermes Reef, to the northwest of French Frigate Shoals. Until the early 1970s, green turtles were captured and marketed for food and other products in Honolulu. Today, they are threatened not only by longline fishing vessels, but by a plague of tumors whose cause remains unknown.
Hawksbill turtle (Eretmochelys imbricata). These turtles, federally listed as endangered, were captured in the past for their shells, which were used for jewelry, eyeglass frames, and knick knacks. (Japan continued up to 1992 to import hawksbill shells from international sources.) In Hawai’i, what few hawksbills there are are found around the southernmost islands (Hawai’i, Maui, Moloka’i). Unlike the green turtle, hawksbills were not much used for food. Their diet of sponges can make their flesh poisonous to people who eat it.
Loggerhead turtle (Caretta caretta). These turtles are listed as threatened. The North Pacific population nests on remote beaches of Japan. The greatest threat to their survival in the past came from people gathering their eggs. Today, they are threatened not just by egg collectors, but also by fishing vessels and the ingestion of plastic marine debris – particularly plastic bags, which the turtles can mistake for food.
Leatherback turtle (Dermochelys coriacea). Leatherbacks, federally listed as endangered, can weigh up to 2,000 pounds and are the largest of the turtles and possibly the largest of all reptiles. They are also the most pelagic of turtles, with a range extending far into the northerly latitudes. They are often seen by fishermen beyond the 100-fathom isobath, although still within sight of land. Unlike other sea turtles, they have characteristics of warm-blooded animals and have bony elements more like those of mammals than other turtles. They have no hard shell, but instead have a carapace of leathery, ridged cartilage. The offshore waters of Hawai’i are regularly used foraging grounds in the migration of these turtles. Although the nesting grounds for the leatherbacks found here are not known, the shores of Malaysia and Mexico are the most probable nesting areas for some Pacific stocks of leatherbacks. Their eggs are highly desired for food by the local populations, which has been a factor in the leatherbacks’ declining population. Also, leatherbacks feed almost exclusively on jellyfish. When plastic bags are mistaken for food, they, too – like the loggerheads – can die.
Olive ridley turtle (Lepidochelys olivacea). These federally endangered turtles nest on remote beaches of Mexico’s west coast. They were hunted in the past for their leather, which was highly prized by Japanese. (In 1968, Mexico exported the hides of more than a million olive ridley turtles to Japan.) Young olive ridleys are thought to occasionally use Hawaiian offshore waters for foraging.
— Patricia Tummons
Volume 4, Number 10 April 1994