The ecology of Sepia australis (Cephalopoda: Sepiidae) along the south coast of South Africa

The influence of abiotic factors (depth, region, temperature, salinity, and oxygen) on the abundance of the cuttlefish Sepia australis was investigated using data from bottom-trawl stations occupied in April/May (austral winter) 1988 and August/ September (austral spring) 2001 off South Africa' south coast. April/May survey data for 1999, 2003, and 2004, and August/September data for 2003 and 2004 were used to assess regional or depth-related patterns in abundance. Temperature differences in the two years mainly analysed influenced distribution and abundance significantly. Abundance increased eastwards in 2001 presumably because of a high-temperature anomaly stretching westwards (i.e. limiting the species abundance to the west), whereas abundance increased westwards in the more typical winters of 1988, 1999, 2003, and 2004. Abundance increased with depth in spring 2001, 2003, and 2004. Smaller sizes of mature males may indicate that they mature earlier than females. The main prey of all size groups and maturity stages was crustaceans, and there were no size- or maturity-related changes in diet. it appears that S. australis is an opportunistic feeder dependent on whatever prey of appropriate size is abundant at any time. However, the data show an array of patterns, some likely to be the result of biological flexibility in response to a changing environment. Other patterns are part of more stable, well-balanced ecological characteristics of the species.