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Thursday, 31 October 2013

Black Bream Research - Survival Rates in Catch and Release


You may recall Quys first guest blog into his research into survival rates of black bream in catch and release situations - here is part one

well the results are in and here they are from Quys perspective please take a look if your interested in catch and release fishing;

Guest Blog 2 - by Quy Van


Quy hard at it

The increasing popularity and promotion by fisheries regulators of catch and release style fishing, particularly during tournament events, on a variety of Australian species makes it imperative that the welfare of the target species be assessed to ensure high post-release survival.
The cumulative stress placed on fish during capture and confinement and their recovery post release is largely unknown, particularly for Australian species. Recreational anglers are becoming increasingly aware of sustainability issues in recreational fisheries and the importance of good animal welfare practices, but many don't understand the impacts of their handling practices on fish. Many anglers envision that their released fish survive, however if fish don’t survive after catch and release events well intended efforts of recreational anglers are in vain, defeating the purpose of catch and release. Thus, for me being an avid recreational angler with a passion for creating a better sustainable fishery for fellow anglers, it was important to study the impacts of capture and confinement on fish. 

In the name of fisheries health - Quy is passionate about maintaining stocks
As there is a major knowledge deficit in this area on Australian fish, it is important to obtain key data to maximise welfare outcomes from recreational fishing. Most of the limited research has predominantly been conducted on overseas freshwater species, such as smallmouth and largemouth bass, pike and salmonids, none of which are related to estuarine and saltwater species. Before we progress further, it is quite important to note here that a stress response in fish is a healthy and natural response, and shouldn’t be seen as a negative perception. 

Testing - the tedious part of the study
With the “fun” part over, that is – going fishing as part of my study, the important lab work had to begin, so we, as recreational fisherman, can get an idea of the capture and confinement practices on an important recreational species, black bream. Without boring you all with the little nitty-gritties, there are 4 key indicators of stress that are found in all fishes, being cortisol, glucose, lactate and total protein.
Using special chemical kits known as ‘endpoint assay kits” these specifically tell us how much cortisol, glucose, lactate and total protein is present. My study analysed the collective capture and confinement stress over a 24 hour period, which will give us a true indication of their stress levels. Once samples were loaded with special binding chemicals, they were put through a microplate reader, which gave me a lot of fun numbers to play with!  After sifting through what seemed to be a never ending file of numbers, results were collated, and my curiosity was fulfilled, with the 16-18 hour days staring at my screens, I got the results I was hoping for, all my Christmases and birthdays coming at once – fish recovered well within the 24 hour period from capture and confinement, indicating black bream are a very hardy and tolerant species, making them an ideal candidate species for tournaments, as well as recreational fishing – sounds nerdy and dorky, I know, but it’s what hard core fisho’s with a science degree live for! To further strengthen my data, to make sure the results of my study are truly indicative, data was further painstakingly statistically analysed, which showed that there was no statically significant differences between our unstressed fish and stressed fish at 24 hours.
The outcomes of this study showed that:

1.      Bream do elicit a stress response (which is a naturally occurring response from a stressor, i.e. capture)
2.       Fish recover quicker than we had thought
3.       Post release survival for this species after the rigors of capture and confinement are high (in a previous study specifically looking at post release survival rates, Grixti et al., 2008 reported shallow hooked fish was 95% and deep hooked, i.e. past the gills was 74% if the line was cut) and this positively reflects a previous study.
4.       They are a robust and tolerant species
Furthermore, the best outcome from this study is that the techniques we developed can be used to assess stress responses in other key species, and shows that current recreational practices are working well.  I would like to give a special shout of to my “research assistant” Jesse Olle for helping me with this study, because without his help, obtaining 144 bream and sampling by myself would have been impossible. 


Healthy bream left to grow bigger - that's the goal for this slow growing species