Abundance and condition of larval cod (Gadus morhua) at a convergent front on
Abstract: In November and December 1992, Atlantic cod (Gadus morhua) larvae were most abundant at a convergent front located at the periphery of a well-mixed gyrelike water mass rotating near the crest of Western Bank (outer Scotian Shelf). Zooplankton wet biomass and plankton abundance (272 and 529...
| Main Authors: | , , , , |
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| Other Authors: | |
| Format: | Text |
| Language: | English |
| Published: |
1997
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| Subjects: | |
| Online Access: | http://citeseerx.ist.psu.edu/viewdoc/summary?doi=10.1.1.513.4097 http://www.phys.ocean.dal.ca/~taggart/Publications/Lochmann_etal_CJFAS-54_1997.pdf |
| Summary: | Abstract: In November and December 1992, Atlantic cod (Gadus morhua) larvae were most abundant at a convergent front located at the periphery of a well-mixed gyrelike water mass rotating near the crest of Western Bank (outer Scotian Shelf). Zooplankton wet biomass and plankton abundance (272 and 529 µm size-classes) were also higher in the frontal region relative to the adjacent water masses. We used the frontal feature to test the hypothesis that larvae in frontal regions are in better condition than larvae elsewhere. No significant differences in triacylglycerol content (an index of nutritional condition), Fulton’s K condition index, nor in the daylight feeding ratio were found between larvae in the frontal region and those in the adjacent waters. The convergent front acted as a larval collector, but exchange with other water masses eliminated measurable differences in larval condition. Our observations indicate that physically driven retention, not differential mortality (approximated by condition), was responsible for high abundances of cod larvae at this front. Résumé: En novembre et décembre 1992, les larves de morue (Gadus morhua) étaient les plus abondantes dans un front convergent situé à la périphérie d’une masse d’eau bien brassée en rotation, semblable à un tourbillon, près de la crête du banc Western (plate-forme Scotian extérieure). La biomasse humide de zooplancton et l’abondance du plancton (classes de taille de 272 et 529 µm) étaient également plus élevées dans la région frontale par rapport aux masses d’eau adjacentes. Nous avons utilisé la caractéristique frontale pour vérifier l’hypothèse que les larves dans les régions frontales sont en meilleur état physique que les larves vivant ailleurs. Aucune différence statistiquement significative dans la teneur en triacylglycérol (un indice de l’état nutritionnel) dans l’indice K de l’état physique de Fulton ni dans le rapport d’alimentation à la lumière |
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