Are bigger calamary Sepioteuthis australis hatchlings more likely to survive? A study based on statolith dimensions

Abstract

To determine whether any size-selective processes were operating throughout the life history of squid, this study set out to ascertain whether bigger hatchlings are more likely to survive to adulthood. This was achieved by comparing natal statolith dimensions between recently hatched (<13 h old) and successfully recruited adult Sepioteuthis australis. The squid statolith (analogous to the teleost otolith) retains a check associated with hatching, and the natal radius (NR) at hatching had a strong linear relationship to dorsal mantle length (ML). Hatchlings were collected using emergent traps from October 2001 to February 2002 on natural spawning grounds located on the east coast of Tasmania. Hatchling size was extremely variable ranging from 4.3 to 7.3 mm (ML), with significantly larger squids hatching out in November and the smallest in February. From February to August, adults were collected from the same bay and aged using validated daily rings in the statolith and those adults estimated to have been born between October and February were included in the analysis. In all but 1 mo, a significant difference between the NR size distributions of the hatchlings and adults was detected due to low numbers of adults with small NRs. This indicated that smaller hatchlings were less likely to recruit, suggesting that there is an element of size-mediated mortality operating on populations of S. australis.