Dolphins “trawling” behind fishermen’s trawling nets are getting snared at sea.
If you love fish, there is nothing like catch from the Mediterranean Sea. But extensive commercial fishing, a new study finds, is endanging the sea’ dolphin populations. This has been shown in a new study carried out at the University of Haifa’s Department of Maritime Civilizations. “Unfortunately, we turn our backs to the sea and do not give much consideration to our marine neighbors,” states researcher Dr. Aviad Scheinin.
The study, supervised by Prof. Ehud Spanier and Dr. Dan Kerem, examined the the two top predators along the Mediterranean coast of Israel: the Common Bottlenose Dolphin (Tursiops truncatus) and bottom trawlers.
Commercial trawling in the Mediterranean off the coast of Israel targets codfish, red mullet and sole, three commercial and sought-after types of fish. The Department of Fisheries in Israel’s Ministry of Agriculture has data showing that over the years the amount of fish from the sea floor looted by Israel’s commercial trawling is larger than the amount of fish that nature provides, indicating that the sea floor fish population dropped between the years 1949 and 2006.
Would this decline in fish supply necessarily cause direct harm to the dolphins, seeing as their diet might also include other types of fish? In order to verify this, the researcher examined the contents of the stomachs of 26 dolphins that died and landed on the beach, or that had been caught by mistake. He also examined the behavior of living dolphins by carrying out 232 marine surveys over more than 3,000 km. along the central coast of Israel. The dolphins’ stomachs contained mainly non-commercialized fish, suggesting that they perhaps do not compete directly with the commercial trawlers, and that the commercial fishing does not directly affect the dolphins’ nutrition.
The living dolphins’ behavior, on the other hand, draws an entirely different picture. According to Dr. Scheinin, most of the dolphins were observed around the trawling boats: the chances of observing a school of dolphins near a trawler is ten times higher than in the open sea. This is because the trawler serves as a “feeding station” for the dolphins: there they are not able to feed from the more expensive loot caught in the nets, but they are able to enjoy schools of other types of fish that swim around the trawler.
“The problem is that this type of fishing endangers the dolphins. Eight dolphins die each year off the coast of Israel on average, and of those, four die after having been mistakenly caught in trawling nets. Seeing as many studies have proven the high intelligence of the dolphin, it is clear that these sea mammals are aware of this danger, but are left with little choice due to their need to search for food around the trawlers due to the scarcity of other food sources,” Dr. Scheinin explains.
“There is a stable dolphin population off the shores of Israel, and any resolution concerning the sea must also consider the dolphins. So as to preserve this population we must declare extensive marine nature reserves, so as to regulate fishing and bring an end to sea pollution. Regrettably, we are not considerate enough of the dolphins,” he concludes.