Vertical distribution and diel migration of Crangon septemspinosa Say, 1818 (Decapoda, Caridea) on Georges Bank, northwest Atlantic

Abstract

We sampled for vertical distribution and possible diel vertical migration (DVM) of Crangon septemspinosa Say, 1818 on and around Georges Bank, Northwest Atlantic, between 1995 and 1999. Both juveniles and adults were found to undergo DVM, being distributed within the lower water column (and perhaps on or in the bottom) during the day, and distributed throughout the water column at night, with higher abundances seen in all depth strata at night. Differences in vertical distribution were also found based on location and chlorophyll concentration for juveniles, but no effects were seen of season, salinity, temperature, lunar periodicity, year, or copepod prey for either juveniles or adults. Variation in vertical distribution and DVM were only moderately well explained (50% of the total variance) by the above factors, suggesting that some other factor(s) not measured by us (e.g., predation) were potentially also controlling the vertical distribution and diel migration of C. septemspinosa on Georges Bank. RÉSUMÉ Nous avons échantillonné Crangon septemspinosa Say, 1818 sur et autour de Georges Bank, Atlantique nord-ouest, entre 1995 et 1999 pour sa distribution verticale et ses possibles migrations verticales journalières (DVM). Juvéniles et adultes ont présenté des DVM, étant distribués dans la colonne d'eau basse (et peut être sur ou dans le fond) durant la journée, et distribués à travers toute la colonne la nuit, avec de plus fortes abondances trouvées dans toutes les strates verticales pendant la nuit. Chez les juvéniles des différences de distribution verticale ont aussi été trouvées en relation avec la localisation et la concentration en chlorophylle, mais aucun effet n'a été trouvé pour la saison, la salinité, la température, le cycle lunaire ou les proies de copépodes aussi bien pour les juvéniles que pour les adultes. Les variations de distribution verticale et de DVM ont été seulement modérément expliquées (50% de la variance totale) par les facteurs précités, suggérant que d'autre(s) facteur(s) non mesurés (e.g., prédation) pourraient aussi contrôler la distribution verticale et la migration diurne de C.

Feeding Interactions between Fishes in a Coastal Ecosystem in the Southern Gulf of St. Lawrence, Atlantic Canada

“…Three pelagic species (American Shad, Atlantic Herring, and Atlantic Mackerel) only consumed small amounts of seven-spine bay shrimp, consistent with the shrimp remaining close to the bottom during daylight hours (Heck et al 1989;Joseph et al 2006;Brown et al 2014). In contrast, Rainbow Smelt ate large amounts and Alewives consumed moderate amounts of seven-spine bay shrimp (Stone and Daborn 1987;Lecomte and Dodson 2005; this study), which is consistent with the near-bottom distribution of these two fishes during daylight hours.…”

“…; Brown et al. ). In contrast, Rainbow Smelt ate large amounts and Alewives consumed moderate amounts of seven‐spine bay shrimp (Stone and Daborn ; Lecomte and Dodson ; this study), which is consistent with the near‐bottom distribution of these two fishes during daylight hours.…”