LOCOMOTORY PATTERNS OF MICROZOOPLANKTON - POTENTIAL EFFECTS ON FOOD SELECTIVITY OF LARVAL FISH

Microzooplankton are a morphologically and ecologically diverse group of organisms that are an important food source for larval fish. The lo comotory behaviors of microzooplankton have probably evolved to allow the organism to feed efficiently or to allow non-feeding larval forms to remain in the water column and disperse. Swimming patterns also aff ect the ability of predators to recognize microzooplankton as potentia l prey, however, especially in estuaries where non-food, suspended par ticles are abundant. Using a video-computer system for motion analysis , the swimming behaviors of a wide variety of microzooplankton species have been quantified. Swimming patterns of microzooplankton include t he smooth helical patterns of some dinoflagellates, tintinnids and rot ifers, the jerky swimming of some copepod nauplii and the stop-and-go patterns of other copepod nauplii and some ciliates. Factors affecting the selective feeding of larval fish include prey size, prey visibili ty contrast, encounter rate of predator with prey, prey escape respons e and prey swimming pattern. By comparing prey of similar size and vis ibility contrast, and correcting for differential encounter rates betw een fish larvae and their prey, it may be possible to evaluate the imp ortance of prey motion patterns in determining the attack rate on diff erent microzooplankton species and the importance of escape behavior i n determining capture rates.