LOCATING SEA FISH

Evening Post, Volume CXXIII, Issue 18, 22 January 1937, Page 16

LOCATING SEA FISH

USE OF ECHOMETER

The possibilities of that ingenious scientific instrument the echometer | or echo-sounding device are likely to ; become far reaching with regard to many seagoing vessels and to herring craft in particular (says a writer in the "Weekly Scotsman"). By its use [commercial fishing, it is claimed, may be immensely assisted, and the safety |of vessels sailing waters where there jtire treacherous * reefs greatly inI creased. The echo-sounder is an electrical, | device that records the depth of water over which a boat sails, and also any intermediate obstruction, such as a submerged rock or a shoal of fish, that may be located in the intermediate water layers. Its chief operation consists in making recordings or echograms on a chart as the steamer or ship moves along. Connected with the instrument is a meter which is fixed in the wheelhouse of the boat. It is graduated in fathoms. A sound wave is sent from the bottom of the boat; it goes to the sea bottom, and is echoed back. The time taken to complete the journey is translated into fathoms, and is shown: on the meter, and is also recorded. The resulting echogram shows the depth of the water, the nature of the sea bottom (whether it is hard or soft) and the presence of a shoal of herring is indicated by a wavy line. An outstanding instance of the practical value of the echometer was witnessed a number of years ago when by its means the hulk of the Lusitania, sunk by the Germans off the Irish coast during the war, was discovered. The location of shoals of fish with the aid of the echo-sounder is still in the experimental stage; and Norwegian experts have so far attained the greater measure of success in its application. The Norwegians are more interested in the movement of fish, notably herring and cod, than British fishermen. One of their fishery research vessels a short time ago made use of an echosounder with a view to tracing herring shoals, and did so very successfully. In a-certain area, dense shoals were directly traced; the Norwegian herring fleet was informed of the presence of the fish; and proceeding to the spot on the following day, the fishermen secured heavy catches at a depth of 45 to 80 metres. Shoals of spawning cod were also located on the Lofoten grounds. Some research work with the echometer was attempted on the Argyllshire coast early in 1933. ' A demonstration set was installed in a Campbelltown herring skiff. The presence of shoals of herring was clearly indicated on the various echograms made, enabling the fishermen to obtain catches of fish of which they would otherwise have been unaware.