Surface schooling behaviour of the coastal krill Nyctiphanes australis (Crustacea: Euphausiacea) off Tasmania, Australia

DP O'Brien
1988 Marine Ecology Progress Series  
Surface schoohng by the euphausiid Nyctiphanes australis Sars occurs throughout the year off the east, south-east and north coasts of Tasmania. Direct observations of the schools using SCUBA showed them to be highly integrated with CO-ordnation comparable to that described for fish schools. Overall school morphology as viewed from the air and underwater was found to be variable between 3 basic forms. The integration within schools and absence of strong passive mechanisms for school formation
more » ... gest that it is an active process The size range of individuals within a school was restricted, although schools are formed at least from the post-larval stage onwards. The sex ratio of N. australis schools approximated 1:l. Schooling/swarming in adults is probably related to reproduction, but the causes for swarm formation in sub-adults are unknown, being most likely related to feeding or maturation. N. australis is shown to be capable of feeding whilst schooling, and it is suggested that other species of schooling euphausud may also be capable of this given the right conditions. School density ranged from 3000 to >450 000 indwiduals m-3, with the biornass for an individual school being as high as > 100 kg wet weight.
doi:10.3354/meps042219 fatcat:frutu7245rgfba74ch27ympgcy