Recreational SCUBA diver interactions with the critically endangered Grey Nurse Shark Carcharias taurus

Abstract

Grey Nurse Sharks Carcharias taurus are listed as ?Critically Endangered? along the east coast of Australia. Magic Point (off Maroubra) in Sydney is favoured by recreational SCUBA divers wishing to observe these sharks. This study was conducted to answer the question: do current recreational SCUBA diving practices at Magic Point have a significant impact on the aggregation behaviour of C. taurus? The study found that diver activity does temporarily affect the behaviour of C. taurus at this site, with a significant difference in the number of sharks and their distribution within the preferred area of occupation inside the cave between diver and non-diver treatments. Small dive groups (= 4 divers) approached the cave closer than large groups, resulting in a greater impact on sharks than large groups positioned further back from the cave. Shark behaviour rapidly returned to pre-diver exposure levels once divers left the area. This study is the first to (a) monitor recreational SCUBA diver activities at a critical habitat site and (b) use a non-invasive behavioural technique to study the behavioural responses of C. taurus towards SCUBA divers in southern NSW. It contributes to improving C. taurus conservation measures along the east coast of Australia by highlighting current diver behaviour and its impact on Grey Nurse Sharks at this site. Results suggest that changes in the current code of practice regarding SCUBA diving at recognized and protected Grey Nurse Shark critical habitat sites should be considered by relevant management agencies.