Through the early 1980s, the Gippsland Lakes produced around 80% of Australia’s commercial catch of black bream. Annual catches ranged between 100 and 240 tonnes. Since then, the catch has declined, gradually for many years, then abruptly to around 30 tonnes in the past three years. In 2000/01, when the commercial catch was 159 tonnes, the recreational catch was estimated at 100 tonnes. By 2004/05, when the commercial catch was down to 27 tonnes, local anglers believe that the recreational catch was down by a similar proportion – to less than 20 tonnes.
In July this year, PIRVic researchers, Fisheries Victoria managers and regional fisheries officers met with representatives of angler, commercial fishing, co-management, academic and tourism interest groups at Bairnsdale to discuss the latest assessments of the bream stock and the fishery management implications. While the results indicate a depleted bream stock, it is encouraging to see that the information base for managing the fishery is sound and improving, and that all parties are committed to doing what is necessary to see that fishing is contained to sustainable levels.
Since 2001/02, annual catch rates by commercial haul seines and mesh nets have been at the lowest levels since detailed reporting began in 1978. In addition, creel surveys confirmed anglers’ views that it now takes on average 20 hours or more of fishing to catch a legal-sized bream in the Lakes system, including the Mitchell, Nicholson and Tambo rivers. Annual surveys of juvenile bream in the lakes show signs of reasonable spawning success in 2001, 2003 and 2004. While this offers some encouragement, the levels are low compared to the last really substantial spawning success back in 1989. Along with reduced numbers of bream being recruited to the stock each year, there is also evidence that the growth rate has increased over the past 8 years. While on average it took bream from the last strong year-class 8 to 9 years to reach 20cm, it now takes only 2 to 3 years.
The main management response to this situation has been to use temporary measures, from December 2003, to increase the legal minimum length from 26 to 28cm for all bream fishing in the Gippsland Lakes and inflowing rivers. Previous experience has shown that this is the most effective and fairest means of reducing the catch retained by both anglers and commercial fishermen.
The immediate effects on anglers have been to increase the time taken to catch each legal-sized bream and increase to over 90% the proportion of the shore-based bream catch that are under-sized. The ongoing creel survey has enabled researchers to estimate that the 2cm size increase has resulted in a reduction in mortality (fish deaths) caused by recreational fishing in the rivers by 30%.
Results of hooking trials show that the overall survival rate of released bream is around 85% but depends on where the fish are hooked. Over 90% of bream released after being hooked in the lip or mouth survive but less than 70% survive after being hooked in the throat or gut. The incidence of deep hooking increases with bream length, averaging 28%.
When combined, these creel and hooking trial results have enabled researchers to estimate that, in the rivers, more bream are now dying after release than are being retained as legal-sized catch. So, while the size increase has met the objective of reducing overall mortality, it has come at some cost.
The effects of the size increase on commercial catches are not so readily estimated. Most of the catch is taken in mesh nets where fishermen report that – predictably – the percentage of fish being released as undersize has increased. While the survival rate of bream released from haul seines has been shown to be high, the survival rate of those released from mesh nets is unknown. This is a key gap in the information available to managers.
Commercial mesh net fishermen are caught in a bit of a bind. If they increase the mesh sizes the percentage of undersized bream will be reduced, but so will their catches of some other species that have become more important as bream catches have declined. On top of this, the temporary nature of the bream size increase is a disincentive to undertake costly net replacements. Further, the recent announcement of another round of voluntary commercial licence buy-outs is unsettling as the Government has not spelt out its goal in terms of the future of the commercial fishery in the Lakes. Added to this, commercial fishermen have been reluctant to be part of joint discussions after information they presented at previous stock assessments was later misrepresented publicly by some anglers.
A number of alternatives to the increased size limit were considered at the Bairnsdale management forum. This presented a real challenge in terms of the severity of alternatives that could meet the aim of reducing fishing mortality by 30% in the recreational fishery. A lack of adequate information was also a problem.
In theory, closure of the recreational fishery for four months, from March till June, could meet the objective but would have a major impact on anglers and the local economy. In practice, fishing for other species in the multi-species Lakes fishery would inevitably result in the catch, release and mortality of significant numbers of bream. There was insufficient information to consider area closures, recognising the likelihood that fishing pressure could be simply displaced to areas remaining open to fishing. There was also insufficient information to consider a closed season linked to the bream spawning season, bearing in mind the high level of variability in environmental conditions.
Reduction of the bag limit to 1 per day could reduce fishing mortality by 25%. However, although 80% of anglers currently fail to catch a legal-sized bream in a day’s fishing, a 1/day limit was seen as a major disincentive for tourists to visit and fish in the Lakes system. The tourism and business interests are concerned that the introduction of a more severe bag limit or significant seasonal or area closures would increase the trend of anglers bypassing the Lakes region and heading to other parts of the coast.
There is some support for the introduction of a legal maximum length for bream to protect the larger mature fish. As the lack of spawning and recruitment success is the main factor limiting recovery of the bream stock, this seems to be one the few practical measures immediately available to fishery managers. It has the advantage of having a similar effect on both sectors as well as being readily supported through education and enforcement. However, as large bream make up only a small part of bream catches, on its own this would not achieve a sufficient reduction in fishing mortality.
Although it was not discussed in detail at the management forum, stocking is another possible “solution” to the bream stock decline. Unfortunately, like all the other fishery management responses, this would address the symptoms but not the underlying causes of the decline that seem to be clearly driven by deterioration in environmental conditions in the Lakes system, particularly as they affect bream recruitment. Nevertheless, a large-scale stocking trial with releases of marked bream could help to identify the weak point in the bream life cycle in terms of the suitability of the Lakes environment.
All the indications are that the strength of each year-class is determined at an early stage while conditions are generally favourable for later juvenile and adult stages. The complex interactions between spawning adults and early life stages and environmental conditions – natural and human-induced – have been studied intermittently in the Lakes system for at least 30 years without providing definitive answers.
A well-designed stocking trial may provide a far more direct and less expensive approach to identifying the weak point as well as providing a practicable solution to what may be an otherwise intractable environmental problem. This approach may well be considered when the questions are eventually asked: how much more of Victoria’s limited fisheries research capacity should be channelled into this ailing fishery and what approaches will yield the best returns?
Whatever strategies are adopted in the future must meet a number of challenges. First, they must be seen to apply equitably to both the recreational and commercial sectors.
Secondly, commercial fishermen must be re-engaged in open information-sharing and management forums in which they can have full confidence. The impact of management strategies on bream stocks, including the survival of bream they release from mesh nets, cannot be measured without their willing participation.
Thirdly, the tonnages of bream eaten each year by cormorants, dolphins and other protected wildlife must not divert attention away the main tasks of managing the impacts of fishing and looking for ways of addressing or circumventing the environmental factors that determine recruitment success.
Current management strategies are underpinned by a number of monitoring and research programs. A creel survey of recreational fishing is continuing in parallel with the mandatory commercial fishery catch and effort monitoring program. Research on the survival of hooked fish released by anglers has been completed and results are being applied in two ways – incorporation in bream stock assessments and angler information programs.
Individual tracking of acoustically tagged bream within the Lakes system began in late 2004 and will assist the development of improved stock assessment models in the future. Tracking is already shedding light on the success of a re-snagging program in the Tambo and Mitchell rivers.
A key ongoing angler information and education program is supported by regional Fisheries Officers, Fishcare volunteers, creel survey officers and other government and industry media.
The Bairnsdale workshop identified areas where further work is needed to change angling practices and angler attitudes in order to make the most of the bream stock we have right now. Promoting the use of hooks larger than #4 and hard baits (in preference to sandworms) will help reduce the mortality of under-sized bream.
Amazingly, some local angling clubs still hold catch-and-keep competitions targeting trophy-sized bream in the Lakes system. The fact that specialist bream anglers are still prepared to selectively remove these large adult fish illustrates how much remains to be done in the area of raising awareness of the collective impact of individual actions – and changing angler attitudes and behaviour.
The bottom line is this: if the condition of the bream stock is largely driven by intractable environmental conditions, it may be that no management action can restore it to the more productive levels of the past.
Everything possible must be done to ensure that the impacts of catches and releases of bream continue to be sustainable and to ensure that the stock remains capable of responding to favourable spawning conditions when they occur.
A 30% reduction in mortality caused by recreational fishing may not be enough.Reads: 1616