Bottom-up forcing of growth and condition changes in Northwest Atlantic capelin (Mallotus villosus) during the 1990s : evidence from feeding indices

Obradovich, Shannon Grace (2008) Bottom-up forcing of growth and condition changes in Northwest Atlantic capelin (Mallotus villosus) during the 1990s : evidence from feeding indices. Masters thesis, Memorial University of Newfoundland.

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Abstract

I investigated the persistence of changes in the biology of capelin (Mallotus villosus) of the northern Grand Banks ecosystem, in relation to the food web and other species. Comparisons of condition, size, and diet for capelin from the northern Grand Banks, northeastern Scotian Shelf and northern Gulf of St. Lawrence demonstrated that a lack of large zooplankton (euphausiids) in the Grand Banks capelin diet, following the cold period of the early 1990s, resulted in reduced growth (i.e. stunting) and condition. Examination of diet and stable isotope signatures of capelin and northern shrimp (Pandalus borealis) revealed no evidence of significant overlap in prey consumption. Thus, the increase in the abundance and distribution of pandalid shrimps during the 1990s likely did not contribute to the changes in capelin biology and feeding. All evidence pointed to bottom-up, not top-down, forcing of changes in capelin biology.

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