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Sunday, March 8, 2015

Otter ~ Otter board ...... and chasing fish in to nets !!

Otter is a common name for a carnivorous mammal in subfamily Lutrinae.  Otter  species are all semiaquatic or aquatic, with diets based on fish and invertebrates.  In Southern Bangladesh, fishermen are busy at work and receive a helping hand from an unlikely group of companions.  We see them only in Zoos and here is one at Guindy Park..

In Kerala, more specifically in Port of Cochin, have seen ‘Chinese fishing nets’ (Cheena vala) -  fixed land installations of shore  operated lift nets.  Huge mechanical contrivances hold out horizontal nets of 20 m or more across. Each structure is at least 10 m high and comprises a cantilever with an outstretched net suspended over the sea and large stones suspended from ropes as counterweights at the other end.  

The Indian common name arises because they are unusual in India and different from usual fishing nets in India.  The system works on the principle that the weight of a man walking along the main beam is sufficient to cause the net to descend into the sea. The net is left for a short time,  before it is raised by pulling on ropes. The catch is usually modest: a few fish and crustaceans  !

In Marine parlance, with specific reference to fishing by boats – “Otter board” – are a pair of large, heavy, square or rectangular plates or boards of metal or weighted wood attached to the trawl lines on each side of the mouth of a trawl net to maintain lateral spread during trawling. Bottom trawling it trawling fish along the seabed.   With the assistance of mechanized fishing boats, fishing nets through otter boards are thrown open to the seabed and dragged for catching fish.  The otter boards keep the mouth of the trawl nets open.  Otter boards are made of timber or steel and are positioned in such a way that the hydrodynamic forces, acting on them when the net is towed along the seabed, pushes them outwards and prevents the mouth of the net from closing. They are quite heavy and require some skill to be spread. 

While the aid of ‘otter board’ is understandable, read about an interesting article of the Bangladeshi tradition involving harnessing mammals up like reindeer as they chase fish into nets.  Fishermen in Narail, 130 miles from capital Dhaka, use the otters to lure fish into their nets though in 25 years the number of families otter fishing has dropped from 500 to 150.  The fishermen spend around half of their £150 earnings each month buying feed for the otters.  Rivers in the area are now short of fish because of water pollution and overcatching.  Here is the report in MailOnline partially reproduced :

Swimming in circles alongside the fishing boat, two short-haired otters shriek excitedly as they navigate their way through the river which feeds into the Sundarbans, the world's largest mangrove forest. The setting is Narail, some 130 miles from the Bangladeshi capital Dhaka, where  fishermen drop their net close to the riverbank and one by one, tails up, the animals dive into the water. Fishermen in Bangladash rely on otters to help them with their daily work. The otters diver under water and chase fish into the nets  !!   The technique has been used for centuries in the area but the tradition is now dying out in parts of Asia.

 The otters spot fish within the plants and chase them towards the nets; The otters do not catch the fish themselves, instead they chase them towards the fishing net placed next to the boat. …….. In recent years, once abundant fish are increasingly scarce and when fishermen drag up their nets they are often empty. The scarcity of fish within the river has been put down to pollution, over-fishing and pesticides.     This is a rare technique that has been handed down for centuries in the country but a partnership which has already long died out in other parts of Asia.

Fishing is usually done during the night when the fishermen can expect to catch between four and 12 kilogrammes (8.8 and 26 pounds) of fish, shrimp and crabs.Over 25 years the number of families involved in otter fishing in the area has dropped from 500 to just 150. In 50 years the practice has declined by around 90 per cent. There is pessimism around the fishmen who believe that if the trend continues, otter fishing will be 'completely wiped out' within the next two decades. Wildlife experts fear it is not only the livelihoods of the fishing families that are under threat. Short-haired otters are an endangered species in Bangladesh and otter fishing plays a key role in their conservation.  It is believed that the captive population is quite healthy because of the fishing.

With regards – S. Sampathkumar
4th Mar 2015.

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