| Summary: | Research involving the processes governing early life of fishes is important for understanding recruitment to the adult population. The forcing factors, like oceanographic processes and the associated plankton communities, impact the distribution and transport of fish larvae and determine their growth conditions, survival and recruitment to the adult stock. The temporal and spatial overlap of fish larvae and their prey is essential for their feeding, growth and survival. Investigations of the prey size spectra in fish larvae made possible to observe inter-specific prey competition and gain knowledge on the role in the food web. The changes in environmental factors between subarctic and Arctic areas along the west coast of Greenland provide a unique study frame. Here, the period of high primary productivity is short and limited by seasonal changes in light, consequently prey availability for the fish larvae during the summer. The duration of the productive season is of great importance for the early life of fish. The present thesis investigates the diets of capelin and cod in the subarctic Kapisigdlit, as well as the feeding of non-commercial larval fish in the entire Godthåbsfjord system. Furthermore, growth and feeding of capelin were compared between the two distant localities, Kapisigdlit Fjord and Disko Bay. In Kapisigdlit Fjord, the zooplankton community structure was dominated by rotifers and harpacticoid copepod. These organisms appeared too small as prey for cod larvae, where they were feeding on prey sizes of about 5% of their own size (Paper I) and consequently the prey preference spectra covered calanoid nauplii, cladocerans and calanoid copepodites with increasing larval size. In the Godthåbsfjord system and Fyllas Bank area, 4 hydrographic zones were defined; in each zone distinct zooplankton and ichthyoplankton assemblages were observed (Paper II). Calanus spp are mainly found off Godthåbsfjord, while the smaller copepods are found in the inner fjord. Cladocerans and rotifers were mainly found in ...
|
|---|