Post-release survival of captured mako sharks
Post-release survival of captured mako sharks: developing best-practice for sustainable catch and release game fishing.
Dr Jayson Semmens (IMAS)
Dr Jeremy Lyle (IMAS)
Mr Barry Bruce (CSIRO)
Mr Paul Rogers (SARDI)
Short-fin mako sharks (Isurus oxyrinchus) are top predators in marine ecosystems and have widespread distributions in temperate and tropical waters of all the world’s oceans. Makos have low productivity, typical of sharks that do not mature until reaching a large size, producing few young and individuals are unlikely to reproduce annually. Makos are bycatch and by-product species of pelagic longline and gillnet fisheries where they are taken for their meat and high-value fins. They are also a highly-prized recreational species in many regions. Risk assessments in Australian waters and internationally have concluded that mako sharks are at the highest risk of all pelagic sharks. Short-fin mako sharks are listed by the IUCN as Vulnerable globally and Critically Endangered in the Mediterranean. Significant population declines in the Mediterranean Sea and the North Atlantic resulted in this species being listed under Appendix II of the Convention on Migratory Species (CMS) in 2008 and this was followed by a concomitant listing under Australia’s EPBC Act in January 2010. This effectively meant that targeted commercial or recreational fishing for these species was prohibited in Australian waters. In July 2010, after considerable debate, a legislative amendment was made to allow recreational fishing of mako sharks to continue despite the offence provisions under the EPBC Act. These legislative changes and the ensuing debate highlighted an urgent requirement for better scientific data on mako sharks in Australian waters to enable these legislative amendments to be scientifically based.
The popularity of recreational fishing for mako sharks in Australian waters sees a considerable number tagged and released each year. However, there are currently no data available to estimate the survival rate of released sharks. This project aims to determine the level of mortality of mako sharks captured and released by game fishers throughout Australia in order to ensure the long-term survival of this top-level predator. In addition, best-practice techniques for catch and release game fishing will be developed, so that any impacts are minimised. This would be the first study in Australian waters to provide such data and assist game fishers to refine their practices, such that the survivorship of these sharks is maximised.
To determine the post-release survival rates of mako sharks and identify what environmental factors, gear and fishing behaviours produces the least stress and post-release mortality.
1. Determine post-release survival rates of mako sharks.
2. Correlate mortality rates with stress levels, gear type and fishing behaviour.
3. Develop best practice fishing techniques to reduce stress levels and maximise post-release survival and advertise these widely to raise public awareness.
4. Provide the scientific support required for management decisions pertaining to capture-release fisheries for mako sharks that maximises their survival and minimises impact on the species’ population in Australian waters.
This project will provide a UTAS scholarship for a qualified applicant, operational funding from Fishwise Tasmania and in-kind support through a Victorian Recreational Fishing Trust Grant.
Sampling will begin this Austral summer (2011/12), so we wish to fill this position ASAP. The student will be located at IMAS in Hobart.