Protections for the critically endangered leatherback turtle (Dermochelys coriacea) don’t go far enough. Whereas the focus has been on protecting migrating sea turtles from longline fisheries in the open ocean, new research shows that many North Atlantic leatherbacks spend their summers feeding in coastal and shelf waters off Canada and New England, where they are also vulnerable to fisheries.
“Unless conservation efforts expand to coastal and shelf areas, present efforts alone will not be sufficient to save the species,” say Michael James, Andrea Ottensmeyer, and Ransom Myers of Dalhousie University in Halifax, Nova Scotia, in the February 2005 issue of Ecology Letters.
The largest turtles, with a length of nearly 2 m, leatherbacks live in every ocean, and their numbers have declined sharply worldwide over the last 20 years. This decline has been blamed largely on fishing gear, particularly the longlines that can entangle and drown sea turtles in the open ocean. However, longline fisheries are comparatively well-monitored and, until now, little was known about threats from other fisheries in the leatherbacks’ Northern Atlantic range.
James and his colleagues satellite-tagged 38 leatherbacks off Nova Scotia over five summers (1999-2003) and found that turtles typically left in October, migrated south to tropical waters, and then returned to Nova Scotia in June, where they spent the summer feeding on jellyfish in continental shelf and slope waters. “The extended time periods during which leatherbacks use these northern areas place special emphasis on the need to protect turtles there,” say the researchers.
To see what threats leatherbacks might face in their summer feeding grounds, James and his colleagues assessed 83 reports of the turtles’ interactions with fishing gear in shelf waters off eastern Canada. Nearly all of these turtles were tangled in buoy lines, and nearly 20 percent of them were dead. Moreover, these reports probably under-represent leatherback interactions with fishing gear in their summer feeding grounds because shelf fisheries are rarely monitored. This study “is breaking new ground,” says Sebastian Troëng, Scientific Director of the Caribbean Conservation Corporation in San Pedro, Costa Rica. “By-catch in coastal and shelf fisheries may represent an even greater threat to leatherback survival than the more well-known threat of bycatch in oceanic fisheries.”
James, M.C., C.A. Ottensmeyer, and R.A. Myers. 2005. Identification of high-use habitat and threats to leatherback sea turtles in northern waters: new directions for conservation. Ecology Letters 8:195-201.
Photo by Laurie Gordon