“Over fishing throws a whole eco system into chaos”: Professor Senarathne
Friday, 3 January 2014 00:01
Text and pix by P.D. de Silva
“Notwithstanding the general concern over environmental degradation in recent years, fishery stocks and other marine resources have been heavily over-exploited. From the 2-micrometre phytoplankton to the 13-metre long squid, every species living in the oceans is inextricably linked. Each plays a crucial role in the balance of its environment and supports other life forms. Every change affecting one species is therefore likely to have repercussions for a larger number of interrelated organisms. Over-fishing does not only affect the hunted species, it throws a whole ecosystem to chaos,” lamented Ocean University Chairman Professor Ranjith Senarathne.
“In many of the capture fisheries in the Pacific and Indian Oceans, the rate of harvesting has exceeded the natural rate of regeneration leading to biological over-fishing. The FAO estimates that nearly 70% of the world’s marine stocks are in need of urgent remedial conservation and management measures: 44% are heavily exploited, 16% are over-exploited, 6% depleted and 3% very slowly recovering from over-fishing.
More than 69% of the stocks of demersal (living near or on the sea bottom) and pelagic (living near the open sea) fish, crustaceans, and mollusks in various areas of the oceans need rehabilitation. A Strategy for International Fisheries Research study estimates that, worldwide, about 20% of all freshwater species are extinct, endangered, or vulnerable. In Europe, the fishing pressure for cod is so intense that less than 1% of one-year old cod remain in the ocean long enough to spawn and is a serious concern.
Another major source of destruction is the incidental catch (by-catch) and discard of non-target or low-value species and under-sized fish of target species. The global fisheries by-catch and discards are estimated in the range of 20 – 40 million tons per year with an average of about 30 million tons. The percentage of discards in Sri Lanka is high due to illegal methods of fishing. The major culprits in Sri Lanka are multiday craft which use ‘purse seines’ also known as ‘ring nets’ to harvest shoals of fish beneath drift wood in the deep sea. This wanton method which has even put the livelihood of the coastal fisherman in jeopardy has to be stopped. The use of dynamite and bottom trawling are two other destructive methods employed by our local fishermen.
Improvement in the selectivity of fishing gear and fishing methods and educating the fishermen and women as to the repercussions of by-catch and strict enforcement of existing laws could reduce the level of discards by avoiding the capture of juvenile fish and non-target species.
Biological over-exploitation of fishery resources can lead to stock collapse or severe depletion. The large fishing fleets, sophisticated fishing technology and increasing demographic pressures have further compounded the commercial exploitation of fisheries stocks in the world as well as Sri Lanka.”