FISHERMEN'S AID

Evening Post, Volume CXV, Issue 130, 5 June 1933, Page 3

FISHERMEN'S AID

A TELL-TALE INSTRUMENT

DEEP SEA TRAWLING

(From "The Post's" Representative.) LONDON, March 31. A Marconi iuvention known as the cchomoter has made deep-sea fishing a less uncertain enterprise. The instrument is fitted to over 300 British trawlers, and records tho depth of water in which fishing is taking place. In addition to knowing the depth of the waterj experienced operators claim that they are able by this invention, to tell when they are actually passing over a shoal of fish, and roughly the type of fish. The depth is indicated by a peak in a line of light which runs across a scale marked in fathoms on a dark background in tho chart room. The character of 1 his peak, whether it has a sharply-pointed top or a flat serrated top, shows whether it is being reflected from rocks or from sand on the ocean bed. Sometimes between these main peaks, smaller peaks have been observed, and it is these that are held to correspond with the passing of compact shoals of fish. Mr. E. G. Boulenger, director of the Zoological Society's aquarium, said in an interview with a representative of tho "Observer," that shoals of fish: would certainly be likely to impede the progress of rays of light on such an instrument as that described. No doubt, he remarked, it is possible to learn quite definitely of some impediment between the ship and tho sea floor, and the only thing this impediment could l)e, if not weed, would bo fish. There is no question that fish swim in such mass formation that the shoal is often like a solid block. Moreover, there is every stage between fish that swim in isolated form, fish that swim in small shoals, and fish that swim in dense shoals. "And then again there are certain fish only to be found in the neighbourhood of rocks, others only in the neighbour- | hood of sand. To all, therefore, who know the habits of fish the instrument seems to have the possibilities that are claimed. Mr. Boulenger remarked, too, that he has often thought that if all fishermen knew more of the habits of fish they would know with greater exactness at what depth to trawl. Observations made at the aquarium and re'eorded in the proceedings of the Zoological Society, showed, he recalled, that certain fish are more or loss nocturnal, and consequently inactive during the day. Plat fish, for instance, lie during the day half-buried in panel. At night they nre nil extremely active, shuffling about on the floor of their tanks or swimming close to the bottom. It is not, therefore, surprising, he remarked, that the trawler makes its biggest haul of marketable fish at night.