. Commercial fisheries review. Fisheries; Fish trade. December 1957 COMMERCIAL FISHERIES REVIEW 27 ience, many people only measure the dry strength. At one time all gill nets used to catch salmon on the British Colum- bia coast were made of premium-grade linen, which is about 50 percent stronger when wet than when dry. In contrast to linen, nylon decreases about 15 percent in strength when wet- ted; therefore, if the size of twine for a nylon gill net is cho- sen to give the same dry strength as has the linen gill net which it is to replace, then the nylon gill net will be little more than hal
. Commercial fisheries review. Fisheries; Fish trade. December 1957 COMMERCIAL FISHERIES REVIEW 27 ience, many people only measure the dry strength. At one time all gill nets used to catch salmon on the British Colum- bia coast were made of premium-grade linen, which is about 50 percent stronger when wet than when dry. In contrast to linen, nylon decreases about 15 percent in strength when wet- ted; therefore, if the size of twine for a nylon gill net is cho- sen to give the same dry strength as has the linen gill net which it is to replace, then the nylon gill net will be little more than half as strong as the linen net when both nets are in the water.'* While manufacturers of nylon gill nets are aware of this and have selected twine sizes of sufficient wet strength to carry normal fishing loads, some net men and fishermen still select nylon gill nets on the basis of hand tests applied to dry netting. The nets so chosen are too light for the loads they must carry, and are easily torn. Another example of multifilament nylon gill nets is quoted in the paper. The knot strength is more important in fishing gear than the strength of the straight twine. Soon after nylon 66 multifilament gill nets were introduced into the British Columbia salmon fishery, nylon 6 multifilament gill nets be- gan to appear although, when tested, it was found that nylon 6 twine was about 40 percent weaker than nylon 66 twine of the same weight. Nylon 6 was rejected as being unsatisfac- tory for gill nets. However, because these two nylons react differently to knotting, the mesh of a nylon 6 net is only about 20 percent weaker than the mesh of a nylon 66 net of the same weight, states the author. The paper stresses that where materials, either new or conventional, are to be used in new applications, their physi- cal properties should be described in an absolute manner, {Trade News of August 1957, Canadian Department of Fish- eries.) North Atlantic Fisheries Investigations SEA SCALLOP TAGGING A
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