Page 15 - The Life of the Atlantic Cod
ISSUE : Issue 13
Published by Ronald Caplan on 1976/6/1
uncover food* Brawn: "To dig, the small cod inclined its body steeply and made ra? pid side-to-side movements of the head driving the snout between stones....The pec? toral fins beat alternately with great rapidity accompanied by the fast beats of the tail forcing the head downwards." Pebbles were seized in the mouth and tossed aside. Large cod would suck up food and gravel, later rejecting the gravel. Cod do not work together, except in the sense that one cod eating will attract others; but "individual cod soon gave up the attempt to reach food but a succession of cod, all removing some of the gravel, cleared the way for the cod that eventually was suc? cessful." Brawn also noted: "A cod which had partly rejected a piece of food be? cause it was too large often swam slowly until another cod seized the food; it then increased speed and so pulled the food apart." The cod is also a bottom feeder. He depends on the special adaptation of the barbel (sort of a chin beard) and the fin rays on the pelvic fins • all of which are organs of taste. Brawn; "He spreads his pelvic fins widely, either side of him • and his barbel is touching ahead of him. All three points are touching the bottom • so he's like a little triangle going along. If he touches something with the barbel, then he stops, throws his head from side to side (passing the barbel over the morsel) tasting it. If it tastes good, then it is taken into the mouth and either swallowed or rejected. If he touches it instead first with the pelvic fin, he stops; he backs up and he casts his head from side to side until he touches it with his barbel. But he doesn't seem to have any apprecia? tion of right and left. If he touches it with his right fin he doesn't simply turn to the right with his head • it's a searching from right to left until he tastes the same thing he tasted with the fin with the barbel. Then he takes it into the mouth." Young cod tasting the bottom with barbel and fin rays; (right) cod in foreground directing Threat Display; (above) threatened cod in Resisting Posture. Brawn points out that cod gather together for two reasons:when there is a concentra? ted food supply such as herring, or as pre-spawning activity. Otherwise, they defend a zone around themselves in which they will not tolerate other fish. They maintain this zone by aggressive behaviour. "In small fish aggression was mainly in the form of a fast approach by one fish to another....The largest fish commonly swam at maxi? mum speed at the other fish in the tank;an action which intimidated them and caused them to flee before they were touched."Mature fish give a more detailed threat dis? play. "Ihe head is extended ventrally...the rays stand out sharply against the tightly stretched skin. The mouth is held slightly open and the (gill covers) are lifted outward...Ihe fish watches its opponent attentively...and instantly reacts to any change of position of the other fish....The first dorsal fin is pressed down a- gainst the body but th' other median fins are raised." A slight arch in the body gives a 'humped back' appearance. "The pelvic fins are completely extended....the aggressive cod edges closer to the other fish...(and) directs a number of vigorous ',. OCEAN GLASS LTD. WINDSHIELDS INSTM.LED ON THE SPOT Mobile Service 765 Grand Lake Road Sydnev 539-6140 Call Collect CAPS BRETON'S MAGAZIWB/15
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