Collaborative tagging program and research for increasing the survival of released line-caught reef fish.

By Department of Fisheries W.A., Australian National Sportfishing Association WA (ANSA WA) and Recfishwest, FRDC Project 2000/194.

A tagged pink snapper showing distended intestines caused by over inflated swim bladder.

The following information was prepared in August 2004. See the link Preliminary Recapture Results Summary up to early 2006 for later information.

The release of marine fish has become increasingly important to recreational anglers. Fisheries regulations and management tools such as size limits, bag limits and closed seasons as well as a stronger conservation ethic has resulted in more fish being released. Many anglers are keen to know the fate of released fish and how to best enhance their chances of survival.

A collaborative research program, funded by the Fisheries Research and Development Corporation (FRDC) has been implemented to improve our understanding of what happens to released line-caught reef fish on the west coast. This research project is lead by the Department of Fisheries in conjunction with the Western Australian branch of the Australian National Sportfishing Association (ANSA W.A.) and Recfishwest. Its results will link with the FRDC-funded national strategy, Released Fish Survival, to provide a comprehensive assessment of the survival of line-caught fish around Australia.

The primary focus of this research project is the catch and release of recreationally caught demersal fish. The effects of capture depth, release treatment, and hook types on the survival of West Australian dhufish, pink snapper, breaksea cod and baldchin groper will be investigated.

Reef fish caught in deep water may require special handling to improve survival. As many fishers know, various reef species, such as dhufish and breaksea cod, are susceptible to barotrauma when raised to the surface from depths of around 20 metres or more.

Barotrauma results from the expansion of gases in the swim bladder and gas bubbles forming in other organs when fish do not have time to adjust to the rapid changes in water pressure as they are pulled to the surface. The physical effects of barotraumas can be seen in the form of inflated abdomen, stomach pushed into the mouth, bulging eyes, and distended intestines. Undersize or unwanted fish that are returned to the water showing signs of barotraumas may often have difficulty swimming and returning to the bottom.

Westag and the Research

Westag is a well established tagging program run by the West Australian branch of the Australian National Sportfishing Association (ANSA WA). The Westag program makes the most of incidental or accidental catch of undersize fish, fish caught when a bag limit has already been reached or when fishing remote areas.

Tag and release also agrees with the sport fishing philosophy of some anglers who do not want to keep every fish that they catch. Over the next few years Fisheries WA will use the Westag Program as a means to determine the mortality rates and survivorship of released west coast reef fish. During this study tagged individuals of these species will be released by one of three methods:

• Shotline - a release weight is used to return the fish to the bottom. See Release Weight to Improve the Survival of Released Reef Fish for a description of the Release Weight and method of using it.
  
  
• Vented - excess gas is released from the swim bladder using a hollow spike.
  
  
• Simple - the fish is released at the surface level with no other treatment.

Techniques for releasing fish showing signs of barotrauma have not been tested in these species. Although they are currently thought to enhance the released fish survival it is not known to what extent they work and which method is most effective for each species. Information collected during this project will provide a better understanding of the post-release mortality of these species and reveal which method of release is best to mitigate the effects of barotrauma and enhance the survival of the released fish.

The recapture of tagged fish can also provide data about fish movement and growth of each species. This information will be extremely valuable to researchers at the Department of Fisheries to further their understanding these fish species and will be used in fisheries assessments that are the basis of their management.

Thus, Westag gives participating anglers the opportunity to provide important tag and release information about west coast demersal fish.

Overall Research Outcomes

Cooperation between researchers at the Department of Fisheries and recreational fishing groups seeks the following outcomes:

• Improving the survival of released line-caught fish through a better understanding of the effects of different release methods.
  
  
• Improving sustainability of different species by reducing total mortality of released line caught fish.
  
  
• Inclusion of recreational catch and fish survival data in fisheries stock assessments.
  
  
• Educating fishers about best practices in handling fish to increased the adoption of best practices in handling fish throughout the fishing community.
  
  
• Increase the enjoyment of fishing for recreational fishers through the satisfaction of knowing that their released fish will survive.
  

A West Australian Dhufish heading for
the bottom on a release weight.

For further information on the project, and how you can become involved, please contact: Andrew Rowland at Recfishwest

Phone: (08) 9246 3366 E-mail: andrew@recfishwest.org.au

The above information was prepared in August 2004. See below for preliminary results up to early 2006.

Preliminary Recapture Results Summary (up to early 2006)

Interesting Facts

• Survival rates differ between released reef fish that inhabit the West Coast region.

• Water depth and the choice of release method affect the post-release survival of these species.

• The deepest recapture for a pink snapper is 118 metres using simple release.

• The deepest recapture of a dhufish to date is 90 metres released using a release weight (shotline).

• Not one of the recaptured dhufish has shown any significant movement.

Best Handling Practice

• The release weight is recommended for dhufish that show signs of barotrauma.

• Venting is not recommended for dhufish.

• Undersize pink snapper respond well to simple release at depths up to 100 metres.

• Careful handling of fish also increases survival.

The survival of dhufish is affected by the depth at which they are caught. Dhufish caught in deepwater may require special handling to improve survival. When suffering from barotrauma many individual dhufish appear unable to reach a depth where the swim bladder can revert to normal size.

The release weight dramatically increases the chances of survival of dhufish caught from any depths that show signs of barotrauma.

Dhufish released in waters deeper than 40 metres should be returned to the bottom with a release weight to maximise survival chances.

Pink snapper are a more robust species and are better adapted to tolerate capture and release in deeper water. The majority of pink snapper released in depths greater than 80 metres were done so by the simple method. Generally pink snapper are difficult to attach to a release weight because they are very active in the boat and will swim down strongly when released at the surface.

Dhufish recapture rates (to early 2006).

		Release Method	Total Tagged	Total Recaptured	Percentage Recaptured
		Simple	366	23	6.3%
		Vented	199	5	2.5%
		Shotline	318	32	10.1%
		Total	883	60	6.8%

The recapture rates of dhufish fall dramatically from a high of up to 18% in shallow waters less than 30m to below 2% at 60 to 69m.

Release by shotline is the best release method for the survival of Dhufish (10.1%), whereas venting has the lowest rate recapture rate (2.5%).


Pink Snapper recapture rates (to early 2006).

		Release Method	Total Tagged	Total Recaptured	Percentage Recaptured
		Simple	694	65	9.4%
		Vented	89	9	10.1%
		Shotline	37	4	10.8%
		Total	820	78	9.5%

The recapture rates of pink snapper are similar for all three release methods (close to 10%). This rate is similar to pink snapper tagged in the shallower Shark Bay region (10.3%) and higher than recapture rates for this species tagged in Victoria (2.1%). Furthermore, the decreasing trend in recapture rates with depth is not evident in this species.

Notable Recaptures

Tag 33759 - West Australian Dhufish

Originally released hy Shotline in 86 metres, recaptured in the same area in 90 metres after 350 days at liberty.

This is one of the deepest dhufish recaptures to date. The fish originally showed little effects of being caught from deepwater and demonstrates that dhufish can survive deepwater capture and release when treated correctly.

Tag 18148 - West Australian Dhufish Originally released by Shotline in 50 metres, recaptured by the same fisherman in the same place 29 days later.

On capture this small dhufish had its stomach pushed into its mouth due to pressure injury but was otherwise in good condition and released with a release weight. This recapture demonstrates that small dhufish can survive barotrauma with the correct release treatment.

Tag 17525 - Pink Snapper (Nicknamed Yo-Yo) Originally released by the Simple method in March 2003 in 80 metres. Since being tagged this fish has been recaptured 5 times in the same area and each time it has been released by the simple method, with depth recordings of between 80 and 86 metres.

This information is provided by Recfishwest, Westag and the Western Australian Department of Fisheries as part of the National Strategy on the Survival of Released Fish. This research project is funded by the Fisheries Research and Development Corporation.

See the full brochure Preliminary Results of FRDC Project 2000/194:- Maximising The Survival Of Released Undersize West Coast Reef Fish (937 kilobyte PDF file)

See more on TaggingProgram.htm

For more information on tagging and research, see Austag Research Reports (link opens in a new window)



This page last updated 26 May 2007.