Diel vertical migration in the Lake Superior pelagic community. I. Changes in vertical migration of coregonids in response to varying predation risk

Abstract

The distribution of fishes is influenced by a host of physico-chemical and biological variables, including temperature and oxygen, prey abundance, feeding or assimilation rates, and predation risk. We used hydroacoustics and midwater trawls to measure the vertical distribution of pelagic fishes during a series of research cruises on Lake Superior's western arm in 2001 and 2004. Our objective was to assess vertical structuring in the fish assemblage over varying light levels. We observed variability in vertical structuring of both ciscoes (Coregonus spp.) and their primary predator, the siscowet (Salvelinus namaycush siscowet). Our results indicate that deepwater predators and prey migrate extensively over a diel cycle. This migration pattern is most consistent with changes in the distribution of prey resources for siscowet and diel variability in predation risk controlled by changing light levels for ciscoes. The magnitude of vertical migration in ciscoes increased with higher abundance of siscowets, supporting predation risk as a driver of cisco distribution. This study describes the extent of vertical migration in each group of fish, provides a statistical description of the pattern, and discusses the implications for trophic interactions in the Lake Superior food web.Résumé : La répartition des poissons est affectée par une quantité de variables physico-chimiques et biologiques, dont la température et l'oxygène, l'abondance des proies, les taux d'alimentation et d'assimilation et le risque de prédation. Nous avons utilisé des méthodes hydroacoustiques et des chaluts de mi-profondeur pour mesurer la répartition verticale des poissons pélagiques durant une série de croisières de recherche dans le bras occidental du lac Supérieur en 2001 et en 2004. Notre objectif était de déterminer la structuration verticale du peuplement de poissons en fonction de la variation des intensités lumineuses. Nous avons observé de la variabilité dans la structuration verticale tant chez les ciscos (Coregonus spp.) que chez leur prédateur principal, le touladi siscowet (Salvelinus namaycush siscowet). Nos résultats indiquent que les prédateurs et les proies d'eau profonde font d'importantes migrations sur un cycle journalier. Ce patron de migration s'accorde le mieux avec les changements dans la répartition des ressources des proies chez le siscowet et avec la variabilité journalière du risque de prédation contrôlée par les changements de l'intensité lumineuse chez les ciscos. L'étendue de la migration verticale des corégones augmente en fonction de l'abondance des siscowets, ce qui vient appuyer le risque de prédation comme facteur explicatif de la répartition des ciscos. Notre étude décrit l'étendue de la migration verticale chez chaque groupe de poissons et fournit une description statistique du patron de migration; les conséquences sur les interactions trophiques dans le réseau alimentaire du lac Supérieur font l'objet d'une discussion.[Traduit par la Rédaction] Hrabik et al. 22951991Eshenroder and Burnham-Curtis 1999;Knudsen and...

Differentiation of deep-water lake charr Salvelinus namaycush in North American lakes

“…2c), like that of Lake Superior, inhabited deeper water than the lean, and was fatter than the lean as evidenced by its lower percentage buoyancy. The high fat levels in Lake Superior siscowets are hypothesized to be an adaptation for reducing the energetic cost of extensive vertical migration (Henderson and Anderson 2002;Hrabik et al 2006;Jensen et al 2006). A siscowet-like, fat (low percent buoyancy) lake charr was not observed by the author during field surveys of the McTavish (northeast) arm of Great Bear Lake during 2004.…”

There and back again: migration in freshwater fishes

“…This has been suggested as a strategy to increase bioenergetic efficiency, where fish capitalize on the differences in temperature between deep and shallow waters and choose depths so as to maximize their growth rate (e.g., Neverman and Wurtsbaugh 1994). However, it has also been suggested that DVM is driven by a habitat specific trade-off between predation risk and feeding opportunities (e.g., Scheuerell and Schindler 2003;Hrabik et al 2006), similar to the argument for seasonal migration discussed above. Prey fish should thus migrate to the dark, deeper layers during daytime to avoid predation by visually oriented piscivores and then return to the shallow depths during night to feed on zooplankton.…”

Diel vertical interactions between Atlantic cod Gadus morhua and sprat Sprattus sprattus in a stratified water column

“…Hrabik et al 2006. Sprat in the area sampled in the present study also performed DVMs in the feeding season and were distributed in the upper part of the water column at night, where a secondary thermocline at this time of year provided high temperatures above the halocline (Cardinale et al 2003).…”