Few people are aware of the hundreds of thousands, perhaps even millions of small whales, known as dolphins and porpoises, that are killed every year in frightening numbers as a direct result of entanglement in fishing gear. In fact considerably more dolphins are killed today than all the great whales that were killed at the height of the mechanized commercial hunts that brought many species to the brink of extinction.
The other night while listening for whales off the southern coast of Sri Lanka, the Odyssey became entangled in the invisible mesh of a gillnet.
Gillnets are passive fishing devices made of monofilament plastic. They are designed to catch fish by their gills when they attempt to swim through the mesh. They are practically invisible beneath the surface and are virtually undetectable to target and non-target species. Gillnets vary in size from small 22 meter long nets used in artisenal fisheries, to large-scale commercial driftnets that may extend for many miles. Most have a buoyancy float line at the top and a weighted lead line at the bottom - so in effect, the net begins just beneath the surface and hangs down as a giant inpenetratable wall to an average depth of 12 meters.
With engine off and sails lowered, the crew tried for over three hours to disentangle Odyssey. However, as is the intention of these marine spider webs, the more one struggles to escape, the more twisted and entangled one becomes. Fortunately for us, we have several pairs of hands, powerful lights on deck and underwater, and sharp knives. Eventually we cut the Odyssey free. Tragically, millions of marine mammals, turtles and pelagic fish such as sharks, are taken accidentally as bycatch in gillnets every day of the year.
Estimates of dolphin bycatch range from 12,000-45,000 animals in Sri Lankan waters.
Photo courtesy of Anouk Ilangakoon
Marine creatures have evolved over millions of years to deal with threats from predators. Man-made fishing gear is a comparatively recent introduction, therefore animals that find themselves trapped are not equipped to free themselves. The moment they touch the net, their fate is sealed. Such an end must surely be horrific. Air breathing animals such as turtles, birds and cetaceans die a slow death from drowning.
This is of particular concern in many countries, including Sri Lanka, where we have seen so many cetaceans close to shore and in the vicinity of the gillnet fishery. Sadly, extensive bycatch of several dolphin species in gillnets already exists here.
In 1987, Abigail Alling estimated that 38,000 small cetaceans (dolphins) were entangled annually in gillnets deployed within 30 miles of the shoreline. Estimations made ten years ago suggested that 25,000 - 45,000 small cetaceans die in gillnets every year as a direct result of a 'fisheries modernization' programme initiated by the United Nations Food and Agricultiral Organization (UNFAO). Leatherwood and Reeves (1989) reviewed these figures, estimating the number of bycaught animals at more than 11,500, although they admitted that this number was almost certainly an underestimate as practically all catches go unreported.
The National Aquatic Resources Agency of Sri Lanka (NARA) estimates the annual figure to be over 12,950 animals caught in gillnets annually. The sheer number and variety of species involved is shocking, and includes spinner, Risso's, spotted, striped, bottlenose, rough-toothed, Fraser's and common dolphins, dwarf and pygmy sperm whales, pygmy killer whales, false killer whales, killer whales, short finned pilot whales, melon-headed whales and various beaked whale species.
Local Sri Lankan cetacean researcher, Anouk Ilangakoon explains:
"It is difficult to say because, for one thing, we have no population estimates of the dolphins so some of them may be locally threatened. For instance, a large percentage of the bycatch is Spinner dolphins. Yes, they seem to be more common than other species, but we don't really know what the population is. So, it's very difficult to say if it is sustainable or not, but looking at the numbers that are being taken [as bycatch] I should think that in the long-term that it will not be sustainable."
Small cetaceans have long been caught accidentally in gillnets along the coast of Sri Lanka. However, traditionally the nets were made from natural fibers that echolocating odontocetes (toothed whales) could detect with their sonar, or break free from if they became entangled. Unfortunately, the synthetic nets supplied under the UNFAO programme are made of such fine strands of nylon that the nets are very hard for dolphins to detect, even with their remarkably sensitive sonar, nor can they break free from the strong web of netting once entangled.
In earlier days, bycaught dolphins were probably discarded by most fisherman who preferred to keep space in their boats for fish. However, as uses for dolphins are increasingly apparent, gillnets are increasingly set with the explicit intent of entangling dolphins, both for human consumption and as bait. (IWC 1991). It is likely that the number of dolphins killed is increasing, (although no study is being undertaken to determine this), in line with the growing market for dolphin meat which is a cheap and readily available source of protein. The demand for dolphin meat to be used as bait is probably also increasing as commercial fisheries in Sri Lanka continue to expand and fish stocks decline.
Interestingly, all cetaceans are protected in Sri Lankan waters and it is illegal to kill them intentionally or sell the meat. The problem lies in enforcement, which is practically non-existent for a combination of reasons.
The switch from biodegradable fibers to fine monofilament plastic gillnets means that
cetaceans are unable to detect the nets or break free once entangled.
Photo courtesy of Toshiya Kudo
Entrapment in fishing gear is certainly the greatest current threat to small cetaceans. Nobody knows exactly how many dolphins are being killed but the total number worldwide may be in the millions.
It is important to realize and accept that we cannot only blame the fishermen for destructive practices that incur a large bycatch of marine mammals, when we as consumers continue to purchase seafood that has been caught using such gear. Bycatch will never be eliminated, but we can all contribute to its reduction by making an effort to be selective when buying seafood. There is always the argument that fishers need to make a living and of course this is true. However, there is no question that they are capable of doing an equally effective job operating gear that is less destructive and more selective. In the Maldives, the pole fishery is the primary method of capture within 75 miles of shore. This method is extremely selective and targets tuna almost exclusively. It is interesting to note that we are seeing and hearing considerably fewer dolphins in Sri Lanka, compared to the Maldives where dolphins are not taken as bycatch.
Perhaps the UNFAO could fund a program that offers gillnets with pingers - acoustic deterent devices, that have been trailed in other countries and are a proven deterrent to marine mammals. The initial outlay may be expensive, but fewer entanglements means less damage to a gillnet.
This would obviously require change and change is always difficult, but the ultimate benefits are long-term and ensure that there will be plenty of fish for future generations, as well as a stable population of marine mammals.
"Well, basically we need a lot of public awareness in Sri Lanka. I think we need to tell people about our dolphins because people who actually eat the flesh do not know that we even have dolphins, let alone that they are eating dolphins. Very often fishermen are poor people and anything that is a source of income they do not think beyond that so it's important that they too realize that there is a potential here, rather than killing them - that they are important animals and also that they are mammals, because although they see them all the time and they kill them, they know that they [dolphins] are different than fish, but they do not know how they are different. They don't actually know that they are mammals, so I think that it is important that they know that."
Education must be used as a tool in raising awareness about the desperate plight of the world's increasingly threatened dolphin species. It is only when people are outraged enough to want to make a change, that change will come.
Anouk Ilankgakoon is an environment scientist and cetacean specialist working for the
conservation of whales and dolphins in Sri Lanka.
Photo: Chris Johnson
Stay tuned for the next Odyssey log as we continue to explore the plight of the world's dolphins and their increasing struggle for survival against an expanding array of man made threats, including directed hunts.
This is Genevieve Johnson speaking to you from the Odyssey in Sri Lanka.
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John Wiley & Sons Ltd, 1996.
- Jay Barlow and Grant A. Cameron. "Field Experiments Show that Acoustic Pingers
reduce Marine Mammal Bycatch in the California Drift Gillnet Fishery."
Marine Mammal Science - Vol. 19, NO. 2, April, 2003.
- Abigail Alling. "A Preliminary Report of the Incidental Entrapment of Odontocetes by Sri Lanka's
Coastal Drift Net Fishery."
Center for Long Term Research, 1987.
- Carl Safina. Song for the Blue Ocean
Henry Holt and Company, 1997.
- Mark Carwardine. The Book of Dolphins
Dragon's World Ltd., 1996.
Written by Genevieve Johnson