Tag-ReleaseTag-Release

Tag-Release

Conventional fisheries tag and release programs are normally applied to species that are harvested commercially. The application of this technique to species that are naturally rare or uncommon has limited value as a consequence of the few returns or the difficulty in identifying an individual. Some experiments using tags with colour coding have been trialed. Using simple identification tags can provide information on:

• movement patterns;

• site fidelity;

• growth;

• population estimates; and

• mortality estimates.

Depending on the objectives, a number of factors can influence the results of a tagging program including:

• the number of sharks tagged;
• rate of recapture;
• capture stress or mortality;
• tag shedding;
• non reporting of tags; and
• quality of the data recorded (Bruce 1999).

Game fishing groups have expressed a keen interest in accessing White Sharks for tag-release since the species was protected. Other groups have raised concerns that capture induced mortality or sublethal stress may be unacceptably high for this practice to resume. The impacts of hooking, playing, capture and then release of White Sharks in game fishing activities has not been explored. The effects are likely to vary between size classes of sharks (small sharks are likely to suffer less effects) and on how the shark was hooked and played. Sublethal effects may include reduced growth, reduced capacity to feed, interrupting reproductive effort or greater chance of attack from other White Sharks (Bruce 1999). There is currently no quantifiable information on survival after such tag-release. Given that a tagged animal must be ‘in-hand’ to be re-identified there can be little merit in stressing a population through a tagging program that involves a protracted capture process and it would be imprudent to support any targeted tag-release programs unless directed at resolving those issues.

Within the life of this plan it may be possible to critically assess the impact of game fishing tag and release on individual sharks that are caught and played. Given that the White Shark is protected the timing of such work would only be promoted as a priority when the species has recovered sufficiently to be considered for down listing from the threatened species schedules. Re-instating tag release is only possible under current legislation if the regulatory authorities grant an exemption permit. For such permits to be granted there would need to be scientific benefits in doing so. The relative costs and benefits of the work should be considered. Currently the indications are that the population is not sufficiently robust to place at risk through carrying out such studies. However, if such action is undertaken in the future, evaluation on the effect of capture-release by game fishers on White Sharks would include: