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Estimates of egg deposition and effects of lake trout (Salvelinus namaycush) egg predators in three regions of the Great Lakes

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Abstract:

Excessive mortality from spawning through the first year of life is likely responsible for recruitment failures in many lake trout (Salvelinus namaycush) populations. We evaluated relationships between interstitial predator species and lake trout egg deposition in three regions of the Great Lakes. The introduced crayfish Orconectes rusticus dominated the nearshore zone in northern Lake Michigan, whereas other sites in Lake Michigan and Parry Sound were dominated by native Orconectes propinquus. In Lake Champlain, sculpin (Cottus spp.) were the most common interstitial predator, yet densities were comparable with those in Lake Michigan. Predator densities in Lake Michigan (mean ± standard error = 15.5 ± 0.4 predators·m–2) were twice those in Lake Champlain or Parry Sound (6 ± 1 predators·m–2). Densities of eggs were higher in Lake Champlain (2994.1 ± 398.3 eggs·m–2) and Parry Sound (454.7 ± 36.3) than in Lake Michigan (7.5 ± 1.3; Kruskal-Wallis, P ≤ 0.05). Ratios of eggs to predator provide simple measures of the effectiveness of lake trout rehabilitation efforts. The average ratio calculated from 10 successful spawning locations is 190 eggs·predator–1·m–2. Ratios may help establish target egg densities for restoration efforts and the concentration of spawning adults required to allow survival to the fry stage.

L’insuccès du recrutement chez plusieurs populations de touladis (Salvelinus namaycush) s’explique par une mortalité excessive après la fraye et au cours de la première année de vie. Nous avons évalué les relations entre les espèces de prédateurs dans la zone interstitielle et la ponte d’oeufs de touladis dans trois régions des Grands Lacs. L’écrevisse introduite Orconectes rusticus domine la zone proche du rivage dans le nord du lac Michigan, alors que l’espèce indigène Orconectes propinquus prédomine dans les autres sites du lac Michigan et à Parry Sound. Au lac Champlain, les chabots (Cottus spp.) sont les prédateurs les plus communs dans la zone interstitielle, mais les densités sont comparables à celles du lac Michigan. Les densités de prédateurs au lac Michigan (moyenne ± écart type = 15,5 ± 0,4 prédateurs·m–2) sont deux fois plus élevées que celles au lac Champlain ou à Parry Sound (6 ± 1 prédateurs·m–2). Les densités d’oeufs sont plus élevées au lac Champlain (2994,1 ± 398,3 oeufs·m–2) et à Parry Sound (454,7 ± 36,3) qu’au lac Michigan (7,5 ± 1,3; test de Kruskal–Wallis, P ≤ 0,05). Le nombre d’oeufs par prédateur fournit une mesure simple de l’efficacité des efforts de réhabilitation du touladi. Le rapport moyen calculé dans 10 sites de fraye « réussie » est de 190 oeufs·prédateur–1·m–2. Ces rapports peuvent servir à fixer les densités d’oeufs à atteindre dans les efforts de restauration et à déterminer les concentrations d’adultes reproducteurs nécessaires pour permettre la survie jusqu’au stage alevin.

Document Type: Research Article

Publication date: October 1, 2005

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  • Published continuously since 1901 (under various titles), this monthly journal is the primary publishing vehicle for the multidisciplinary field of aquatic sciences. It publishes perspectives (syntheses, critiques, and re-evaluations), discussions (comments and replies), articles, and rapid communications, relating to current research on cells, organisms, populations, ecosystems, or processes that affect aquatic systems. The journal seeks to amplify, modify, question, or redirect accumulated knowledge in the field of fisheries and aquatic science. Occasional supplements are dedicated to single topics or to proceedings of international symposia.
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