Saison d'éclosion et survie des stades larvaires et juvéniles chez la morue arctique (Boreogadus saida) du sud-est de la mer de Beaufort
|Abstract:||Arctic cod (Boreogadus saida) is widely distributed in circumpolar Arctic seawaters and plays an important role in transferring energy from lower trophic levels to higher predators in the Arctic marine food web. To limit vulnerability of young Arctic cod to predation and/or cannibalism at the end of short Arctic summers, reproductive strategy of this key species has evolved to reach the largest pre-winter size of cod juveniles. Two adaptative mechanisms strongly influence variability in survival of juvenile Arctic cod in relation to environmental conditions: the hatching season and early growth. In a changing Arctic climate that exhibits interannual variations and strong seasonality, hatching and growth dynamics of Arctic cod urgently need to be address. In this study, we first determined the individual hatch dates of juvenile Arctic cod sampled in southeastern Beaufort Sea during fall expeditions over a five-year period (2002-2006) and from April to August in 2004. The results suggest the existence of two distinct populations of larval Arctic cod in the study area. First, an inshore population that hatches early in winter (January to March) in the thermal refuge (T ≥ -0.47) provided by the estuarine waters of Mackenzie Lake extending under landfast ice. Second, an offshore population of delayed hatching (April to June) that coincide with the ice break-up and the vernal onset of biological productivity on the Mackenzie Shelf and in the Amundsen Gulf. The interannual variability (2002-2006) documented in hatching patterns of juvenile cod results from the relative importance of early-winter hatchers surviving each year and is partly related to variations in dominant environmental factor in the habitat. Overall, this study documents the reproductive strategy of Arctic cod in southeastern Beaufort Sea that aim to maximize size of juvenile at the onset of their first winter under the ice.|
|Document Type:||Thèse de doctorat|
|Open Access Date:||16 April 2018|
|Collection:||Thèses et mémoires|
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