Standard Operating Procedures of Collapsible Fish Trap

In early times, flowing water caused by tidal movement and changes in river and lake levels were probably used to trap fish behind rudimentary barriers, often made from sticks and stones. It is likely that early humans found that fish catches could be improves by driving fish in to these barriers. They would have found that catches from these barriers decreased over time, as fish became accustomed to them, and would have had to move the traps to fresh areas where more fish could be caught. It would have been hard work to construct new traps, either by moving stones from the old trap or finding new ones. Primitive fishers probably tried making barriers from lighter, more readily available material such as tree branches, brunch and vines. This led to the fishers inventing lighter, movable traps made from brush and nets made from vines which they could carry with them when they moved to new areas. They may even tried bigger, more complicated corral-type fish traps in lake, rivers and coastal waters

Standard Operating Procedures of Deep Sea Beamtrawl

Beam Trawl net is a type of bottom trawl net. The target catches of beam trawl is coastal shrimp. The beam trawl fishing has been recorded of the operation in Thailand since 1957. It is the prototype of the other bottom trawls in the Thailand. Thai fisherman always spread operated the small beam trawl along the coastal fishing ground of Thailand. The fishing boat is 6-8 m. length equipped with 7-8 horse power outboard engines in the few decades. Now a day, fisherman in the inner and central part of the gulf of Thailand, Samutsakorn and Chumporn provinces, have enlarged their fishing boat to be 14-18 m. with 200-300 horse power inboard engines. Only fisherman in the Southern part of the Gulf of Thailand still have operated the conventional small scale of beam trawl. Beam trawls are one type of fishing gear designed on use on the sea bed. A beam trawl consists of a cone-shaped body ending in a bag or cod end, which retains the catch. In these trawls the horizontal opening of the net is provided by a beam, made of wood or metal. The vertically opening is provided by two hoop-like trawl heads/shoes mostly made from steel. No hydrodynamic forces are needed to keep a beam trawl open. While fishing for flatfish the beam trawl is often equipped with tickler chains to disturb the fish from the sea bed. For operations on very rough fishing grounds they can be equipped with chain matrices are rigged between the beam and the ground rope and prevent boulders/stones from being caught by the trawl. Shrimp beam trawls are not so heavy and have smaller mesh sizes. A bobbin of ground rope with rubber bobbins keeps the shrimp beam trawl in contact with the bottom and gives flatfish the opportunity to escape

Standard Operating Procedures of Isaacs-Kidd Mid-water Trawl

Isaacs-Kidd mid-water trawl (IKMT) is oceanography tool used to collect bathypelagic biological specimens larger than those taken by standard plankton nets. The trawl consists of the specifically designed net attached to a wide, v-shaped, rigid diving vane sometime called a depressor. The vane keeps the mouth of the net open and exerts a depressing force, maintaining the trawl at depth for extended periods at towing speeds up to 5 knots, but the optimum towing speeds should be 2-3 knots because of the high level of drag exerted by the net in the water. The inlet opening is unobstructed by the towing cable. The IKMT is a long, round net approximately 6.50 m long, with a series of hoops decreasing in size extending from the mouth of the net to the rear (cod) end, which measures an additional 2 m in length. The hoops maintain the shape of the net during towing. The mouth of the net is 1.75 m wide by 1.30 m high, and is attached to a depressor. The IKMT's largemouth opening and capacity for fast towing speeds enables capture a wider range of relatively large and more active organisms than smaller nets. In addition, its fine mesh allows it to snag animals that are not retained in the large trawl nets that are used for commercial fishing. Thus, it is well suited for capturing an array of fishes, squids and shrimp that inhabit the mid-water zone. To make sample collection easier, the IKMT is always used in conjunction with echo-sounders which provide a target area for the researchers to sample