Fisheries Impact on Sea Turtle Population Sustainability

"Rehabilitation of habitats and management of resources"

Illustration by Stephen D. Nash/ Conservation International

Turtle stocks have been and still are, in some areas, heavily exploited. Concentrating on the Mediterranean, which to some degree reflects the global picture. About 4000 Loggerhead turtles are fished every year in Tunisia. The catch in the Mediterranean is estimated to be at least 6000-8000 animals per year.

Given the slow growth rate of these animals, which may take anything from 10-20 years to mature, the picture is very disturbing indeed. Current information on the loggerhead sea turtles shows these animals breeding in only a few areas in the Mediterranean. The loggerheads largest single nesting site known in the Mediterranean is in Zakynthos, where at best estimates, about 600-800 turtles breed every year. Even if we assume that they breed every 3 years this would make a total of about 1800-2400 turtles.
Of course there are other nesting areas in Greece, Turkey, and Cyprus perhaps tripling this number. Recent information has the Loggerhead turtles also breeding in small numbers in Tunisia and in unknown, (presumably not large) numbers in Libya and Egypt. A catch of 6000-8000 turtles per year, however, implies a much larger population than what is now breeding in the Mediterranean. There is some evidence that some may be breeding outside the Mediterranean on the West African Coast, carrying out migrations into the Mediterranean as indeed they do within the Mediterranean. Several turtles tagged in Zakynthos were caught in Tunisia.

There is clear evidence that as recently as 20 to 30 years ago, turtles used to nest on many more beaches in the Mediterranean. Beaches which are no longer available to them, due to other activities such as tourism, or sand extraction which renders them unsuitable for nesting.

There are many questions unanswered. What is clear however, is that the current recruitment into the population from breeding in the Mediterranean is practically negligible compared to the number of turtles killed in the sea each year, and deaths caused by fishing nets. It is very likely that the present turtle catches depend on a sizeable stock of older turtles that once bred in large numbers on the Mediterranean shores. If this is the case then we can expect a virtual collapse of the stocks in the very near future. This may well be the case with the Green Turtle, a tiny population which now lives in the East Mediterranean nesting only in a handful of beaches in Cyprus and Turkey.
Extract from an article by Andreas Demetropoulos, Department of fisheries, Cyprus.