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> Issue 13 > Page 17 - The Life of the Atlantic Cod

Page 17 - The Life of the Atlantic Cod

Published by Ronald Caplan on 1976/6/1 (283 reads)

<" INACTIVE GROUP 1. Female enters ter? ritory of Male 2. M raises median fins/ S.M fast approach 4. M gives flauntii' / display before F 5. F follows M 6. M leads up 7. F follows then swims down 8. Long period while M flaunts, grunts • (this not shown here) 9. M prods F 10. F swims rapidly upwards followed by TERRITORY OF MALE 11. F stationary at surface, M mounts 12. Dorsal mount 13. Ventral mount, fish spawn the female, raised his dorsal fins momentarily, or paused, and then approached the female slowly. Positioning himself in front of the female and about a foot away, the male cod began the courtship flaunting display...all the median fins were fully erected and the male made many exaggerated lateral bends of the body. The fins, al? though erected, were held lax at their base so that they waved from side to side at each undulation of the body." Brawn in conversation; "It's something that you never otherwise see and it's really the most beautiful sight, because here's the fish with his fins up • and they wave in the water just like the most marvelous banners you can imagine. He's there and he thinks he's the most beautiful thing in the world • that he's waving back and forth • he's almost like a snake in the water, al? most like a ballet • there's a dancing movement to it. This goes on for ten minutes or so. She's moving. She doesn't follow his big, sinuous curves at all • she just keeps in the same general direction but she isn't going through any of these curv? ing motions. She's just very slowly moving always in his general direction. And then if she stops moving, then he of course can get a prod underneath • and that's where the grunt is heard • and at that point usually if she's ready, she swims up and then spawning takes place immediately. (She came to rest at the top of the tank with her back just breaking the surface.) He pushes her down and the two pelvic fins go either side of the female's body while he's still mounted on top. And then he slips down one side. And the spawning takes place with the male upside dovm below the female. They are still grasped together and swimming together. It was normal swimming movements. It V'' '"'W' "''' • • 'Tll''' wasn't a sudden thrashing. The pushing down of vS' /' ' .Cll- the head is really the first stage of mounting. The pelvic fins are so far forward in a cod • they're really right underneath the head, al? most underneath the gill covers • so that at the point he's pressing down with the head, effec? tively the pelvic fin is beginning to slip over the back. Ihe two vents are not pressed together in any way at all." From the report: "On being mounted the female stiffened her body and swimming with awkward sideways sweeps of the tail, contracted the body ventrally and almost immediately spawned. The male also swam and spawned during the ventral mount. The combined movements of the tails drove the pair round in a horizontal circle at the surface and doubtless served to mix eggs and sperm. These are cod spawning in captivity. In wild waters the eggs would disperse from the parents in all directions, suspended. Then those that were fertilized would soon take on a single drop of seawater, become buoyant and begin their journey • they would begin to rise. Our thanks to Vivien M. Brawn for permission to draw from her work on cod behaviour originally published in BEHAVIOUR and JOURNAL FISHERIES RESEARCH BOARD, including the photo and drawings of spawning. The diagram of cod life cycle is from Dr. W. Templeman. permission Fisheries Research Board: Marine Resources of Newfoundland. Bulletin No. 154. Other main source; A.C.Jensen's book. The Cod, published 1972.
Cape Breton's Magazine
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