The dynamics of the summer-spawning population of the loliginid squid Sepioteuthis australis in Tasmania, Australia—a conveyor belt of recruits

Abstract

Abstract The population dynamics of the loliginid squid Sepioteuthis australis was examined on a fine temporal scale during a 2-month period of rising sea-surface temperatures on the summer inshore spawning grounds of Coles Bay, Tasmania, Australia. Samples were taken regularly (generally weekly) to discern any short-term population changes in age, growth or reproductive parameters. There was no change in the mean age, mantle length or weight of males or females through the study period (November and December 1996). This indicated that instead of following one or a few discrete cohorts of spawning individuals, there were continuous waves of new individuals moving onto the spawning beds, which may be best described by a conveyer belt of new recruits. There was an abrupt and significant difference in the mean oviduct egg size in females caught between November and December but the factors responsible for this remain unknown. Few squid showed evidence of recent feeding, suggesting that they move off the spawning grounds to feed.