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Page 5 - A Life History of the Swordfish

Published by Ronald Caplan on 1973/5/1 (1651 reads)
 

A Life History of the Swordfish No ripe swordfish has ever been seen in North Atlantic waters. Fishermen, who have dressed hundreds of them, report having never seen spawn • and this despite all of the swordfish taken by harpoon were female. (The reason for this separation of the sexes is not yet known; possibly the males are more wary, faster or remain beneath the surface during the day • but in any case males were never harpooned. When long- lining began in 1962, they took males and females, all sizes • while the harpooners continued to get only females.) We know this of the breeding behaviour in the Medi? terranean: "The height of the reproduction season in those waters (Straits of Mes? sina) is June and July when the adults approach the coast in pairs, a male and a fe? male. The female spawns in several different deposits. Although the maximum extru? sion is in July, eggs are found until September. It is generally believed that sword- fish spawn only about twice during its life. The swordfish egg is round, dimly translucent and bouyant. The mature egg, from 1.82 to 1.87 mm (about 0.07 inch) in diameter hatches in about 2 1/2 days." The young fry are very different from the ad? ults: they have 1 dorsal fin, 1 anal fin and a rounded tail. Both jaws are equally pronged and toothed, and the skin is covered with rough spiney plates and scales. By the time they weigh 1/2 pound, they resemble the adult swordfish, which has no teeth, 2 dorsal fins (the 2nd is very small), and 2 separate anal fins. The fry will retain the scales till they are a little larger, but these will also go. The adults are a dark metalic-puplish above, dusky colored below. The sword is almost black above, light below. The fins are dark with a silvery sheen. The colors fade quickly after death. Neither the exact growth rate (although thought to be very fast) nor the life span is known with any precision. The largest swordfish ever taken dressed to 915 pounds, which would have given it a live weight weight over 1100. He was caught by Capt. Garrison of Sambro, N.S., off the northern tip of Cape Breton. The sword is 1/3 of the swordfish length and unmistakably sets him apart from his tropical relatives, the spearfish and the sailfish, whose sword is shorter and more round and spearlike. The swordfish deliberately uses his flat, sharp-edged and pointed sword as a tool and a weapon. A great many fish slashed in two immediately behind the head have been taken from swordfish stomachs, indicating that the sword- fish often seeks out and strikes individuals. Sometimes he slashes his way through a school of fish, either coraii' up through the school from below or first leaping from the water and coming down in the midst of the school, setting up a panic through which he flails his sword. Then he turns and swims calmly about eating the maimed victims. X-rays have shown that even when the victim has not been severely slashed, the blow from the sword was sufficient to snap his spine. The swordfish will eat any smaller species of fish, but he seems to prefer (in Canadian waters, which have about 1/3 the species of fish found in southern waters) Atlantic mackerel, barricu- YAZER BRDS: LTD. Two Friendly Clothing Stores Sydney and Sydney Mines JOHN ASAPH T V Sales and Service Baddeck CARA RESTAURANT located at the SYDNEY AIRPORT Cafeteria Hours 6 AM to 12 PM Dining Room Hours 11 AM to 11:30 PM Better Health Centre 436 Charlotte St. Sydney 2 Stores Down from Canadian Tire We have a Large Range of Health, Vegetarian, Special Diet & Diabetic Foods Natural Vitamins Food Supplements Natural Cosmetics Postal Orders Accepteo Bulk Rates Available Cape Breton*s Magazine/5
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