Characteristics of the Biology and Distribution of the Spinner Shark (Carcharhinus brevipinna) in Queensland, Australia Based on Data Collected from the Shark Control Program

The spinner shark Carcharhinus brevipinna (Müller and Henle) is among the most common sharks caught by the Queensland Shark Control Program. All sizes of sharks (from neonates to adults) are taken by the fishing gear (gillnets and drumlines), although smaller individuals are more commonly taken on drum lines. There is a strong seasonality to the catch with most sharks taken during the spring and summer months when they migrate inshore to breed. During this time the average size of sharks taken is also significantly larger (P 0.05) than at other times of the year. Females outnumber males (P 0.05) in the catch with the overall sex ratio being 1.4:1. The species is caught predominantly in nets in the southern part of the state (Gold Coast and Sunshine Coast) and catch rates on baited drum lines are generally low ( 0.04 per drumline/year). In this southern region there was a relatively stable trend in the catch of spinner sharks over the last 11 years but catches sometimes varied by more than 100% between consecutive years. Eighty percent of the 566 spinner shark stomachs examined were empty but teleosts were the main prey, being the most common item in over 71% of those sharks that had identifiable remains in their stomachs. The smallest pregnant female caught was 2.0m in total length. Litter size varied between 4 and 16 (mean = 9.5) and the overall sex ratio of embryos was 1:1. Thirty-six percent of sharks were meshed on the inside of the net (the side facing the shore) indicating that sharks were not just being caught as they migrated into shore.