The influence of small-scale turbulence and upwelling on the ecology of larval fishes /

• Main Author: MacKenzie, Brian R. (Brian Royce)
• Format: Thesis
• Language: English
• Published: McGill University 1991
• Subjects: Capelin > Larvae; Fishes > Larvae; Fisheries > Climatic factors; North Atlantic
• Online Access: http://digitool.Library.McGill.CA:80/R/?func=dbin-jump-full&object_id=70340

Environmental control of interactions between larval fish and their prey, and the potential influence of this relationship on fish feeding and recruitment, were assessed using empirical models developed using data drawn from the literature and developed in field studies. Ingestion rates of larval fish in laboratory and natural environments were found to differ in relation to food density. In laboratory studies, larvae show a strong functional response to prey density. Larvae situated in situ consume food at much higher races than would be predicted from laboratory studies and these rates are independent of prey density at known in situ densities. This discrepancy between laboratory and field feeding rate-food density relationships can be partly explained by the in situ contribution of small-scale turbulence to predator-prey encounter rates. Field studies of the influence of wind on nearshore hydrography showed that wind-induced upwelling generated favorable combinations of nutrients, light, and small-scale turbulence for production by phyto- and zooplankton. The distribution of microplankton $(<$80 $ mu$m) that resulted from these upwelling episodes was quantitatively described by the cumulative longshore wind velocity during the summer months. Microplankton abundance was greatest within 4 km of a major spawning site for capelin, Mallotus villosus, an economically and ecologically important forage species in the north Atlantic Ocean. Interannual variability in the intensity and frequency of upwelling-favorable winds was positively and significantly correlated with recruitment levels in the NAFO 2J3K capelin population. A new recruitment forecasting model, using an upwelling-related wind index as an input, explained more of the variance in capelin recruitment than did a previously published model. These results suggest that larval capelin are more likely to be food-limited in years when wind conditions are unfavorable for upwelling, and that recruitment in this fi