In Australia, though sharks and rays (elasmobranchs) are vital components of Queensland’s East Coast Inshore Finfish Fishery, they are under increasing threat from both local and global pressures. The status of shark stocks in northern Australia has been investigated over recent years, and identified 25 species, for example the blacktip reef shark, Carcharhinus melanopterus, and the handlebar hammerhead, Eusphyra blochii, as being at a high risk of over-exploitation.

A lot of this pressure comes from the fact that the majority of the world’s elasmobranchs are caught as bycatch i.e. they are fished even though they are not the intended targets. Though many are thrown back into the water, the effect of being caught and released on the animal's chance of survival is little understood. As a result, an understanding of the survival of species that have been caught and released and the consequent effects this then has on their sustainability, is crucial in terms of both their management and conservation.

Due to depleting stocks of elasmobranchs (sharks, rays & skates), Queensland has now introduced protection and management measures within its waters. Such initiatives are thought to have increased the release rates of sharks and rays from commercial and recreational fisheries, while the area’s recreational fisherman already operate a high release rate. Yet, despite such positive signs, essentially nothing is known about the effect of being captured on an animal’s survival rate once released back into the water.

If being caught and released was found to have a significantly detrimental effect on sharks and rays, then regulated fisheries would be negatively impacting upon populations despite protection measures being in place; a result which would suggest a need to dramatically improve  handling and release techniques if such newly implemented management and conservation efforts are to go on to have any success in the future.

In this SOSF supported research, project leader Cynthia Awruch, is aiming to develop a range of methods to assess stress and post-release survival in sharks by developing the world’s first assay to measure a stress hormone in elasmobranchs. Using information gleaned from this groundbreaking research it is hoped new techniques on how to minimise post-release mortality through improved handling practices will be made available to fisheries managers and associated groups.

As this is the first time a sampling package has been developed for sharks where a blood sample can be taken quickly and with minimum intrusion, the results will also have implications in understanding not only elasmobranchs’ stress and post release survival, but an entire range of ecological and population responses to stress: be it physiological adaptations to pollution, climate change or the possible links between stress and reproduction development.

During August-September 2008 we started and finished preparing all the necessary material for the field work component of the project, while also getting the animal ethics approval from the University. Gathering all the material needed to work in the laboratory and the material needed for taking and processing the blood, we then completed two field trips as a trial to uncover any possible problem swe might encounter when we started the final trial (e.g handling the sharks, keeping the sharks on board, where to take the blood samples from; some sharks is easy to do it through the caudal vein, some from a dorsal sinus). We also came up with the new idea of measuring lactate levels parallel to stress hormone.

We started to take lactate levels from the sharks using a very simple technique: a lactate kit that gives values as soon as the shark is caught. We will correlate lactate levels and the stress hormone levels. If we found a good correlation between lactate levels and the stress levels, in the future we will be able to provide fishermen with a simple and in situ technique to understand the stress level of the shark before the shark is released back into the water.

            
A black tip shark is just caught.                             Colin Simpfendorfer is keeping the shark in
                                                                          the water to be sure the shark is in good
                                                                          condition before releasing it.

Between October-November we will have most of the blood taken and we will star working in the laboratory developing the assay to measure the stress hormone.