After a boom phase in the 1990s, the recreational fishery for elephantfish in Western Port Bay is now heading into a consolidation phase as concern rises for the stock in southeastern Australian waters.
The Victorian Government’s ban on targeted commercial shark mesh-netting in State waters in 1988 was intended to relieve fishing pressure on school sharks and gummy sharks. While this move contributed to the recovery of gummy sharks it appeared to have the unexpected additional benefit of protecting elephantfish – a by-catch in the shark fishery.
As commercial landings of elephantfish increased through the 1990s, so did anglers’ catches in Western Port. In fact, anglers became so concerned about the large numbers being caught that they initiated the introduction of the three per day bag limit in 1998.
In June 2009, DPI fisheries managers, researchers and regional fisheries officers met with recreational and commercial fishers and charter operators to assess the current state of the elephant fish stock as part of an overall assessment of the Western Port Bay fisheries.
At the previous Western Port fishery assessment in 1998, the only data on elephantfish were based on the commercial fishery and the stock was not assessed. The 2009 assessment featured several improvements made including detailed data on recreational fishing, more detailed analysis of commercial fishing data, information on the size and age composition of catches and a stock assessment of elephantfish in southeastern Australia.
A 2006/07 phone-diary survey involved tracking anglers’ fishing details through regular phone calls to individuals who agreed to keep written records of their fishing catches and effort. This enabled estimates to be made of individual angler’s catches from Western Port, including an estimate of 27 tonnes of elephantfish.
Between 1998 and 2008, boat ramp surveys conducted between November and April provided data on catch rates and size and age composition of elephantfish taken by anglers. The 10-year data set showed that, while recreational catch rates for elephantfish may vary from year to year, overall they had remained stable.
Combining catch estimate from targeted and non-targeted angling with catches by charter fishing, the total recreational catch from Westernport Bay for 2008 was estimated to be 45 tonnes.
The survey results showed that, while some elephantfish are taken during summer, targeting this species peaks in autumn when large numbers of mature females enter the bay.
At the workshop, anglers indicated that their main concern was for the numbers of breeding female elephantfish being taken. This was evidently a common concern as the survey showed that anglers released 28% of the elephantfish they caught. However, they showed a preference for retaining the larger fish.
While the commercial capture method for elephantfish in Western Port Bay – mesh-netting – decreased from the late 1970s, commercial catches increased from zero to around 10 tonnes through the 1990s.
This was the result of increased catch rates, suggesting increased abundance of elephantfish over the same period; increased targeting may also have been a factor.
After 1999, commercial catches and catch rates decreased, partly influenced by commercial licence buy-outs. The commercial catch in 2006/07 was 4 tonnes.
Although most elephantfish taken in Western Port Bay are 7-14 years old, they may live to at least 23 years. Females grow to larger sizes (more than 80 cm) than males and the average size taken is 3.25kg. The combination of their longevity, low reproductive rate and ease of capture while in breeding aggregations makes elephantfish highly vulnerable to over-fishing.
The recreational take in Western Port Bay has become a key element among concerns about the Bass Strait elephantfish stock. It is estimated that fishing down the pre-1970 total stock of 700 tonnes to 400 tonnes could have resulted in a sustainable overall catch of 90-115 tonnes annually.
At that level the stock could sustain the current total annual catch from the Bass Strait region, 114 tonnes. In fact, the stock may have been reduced well below 400 tonnes. Quota and effort reductions have been applied to the Commonwealth shark and trawl fisheries, which, along with state commercial fisheries, have averaged 69 tonnes annually in recent years.
Western Port is an important breeding area for elephantfish with each female placing an average of around 20 encased eggs on soft bottom where they become covered with a protective layer of sediment. While mature females are caught elsewhere during their autumn egg-depositing period, no other site shows the concentrations of mature females seen in Western Port, hence the need for a conservative catch limit and the careful release of unwanted fish.
The overall workshop conclusions were:
1: combined with fishing elsewhere, recreational fishing for elephantfish in Western Port at recent levels is unsustainable, and
2: the effectiveness of the removal of commercial netting in 2007 and the reduction of the recreational catch limit to one per day in 2008 are yet to be demonstrated.
In theory, the successive commercial licence buy-backs and the final removal of commercial netting from Western Port made a small additional catch of elephantfish available to anglers.
In practice, by the time of DPI’s 2006/07 survey of the recreational fishery, angling pressure may have already increased beyond that point, based on perceptions of reduced competition from commercial operators.
One vital question to be addressed is whether the reduction in the elephantfish bag limit, together with other conservation measures, will be effective in contributing to a stock recovery.
Another important and unanswered question is the extent to which elephantfish released by anglers survive. Protection of soft substrates for their importance to elephantfish egg-laying is important and may become a major issue if significant port and channel developments become a reality.
Another issue that will be clarified by future monitoring of recreational fishing is whether anglers will continue to target elephantfish as keenly as in the past. Charter operators reported that, after elephantfish first appeared as a resource during the 1990s they, along with some anglers, had pushed for bag limits to contain excessive catches.
After years of imposing catch limits on their clients they now face a threat to their businesses as potential clients find the current bag limit of one per day is insufficient to justify the cost of a charter trip. They estimated that the clients of some charter operators are now taking in a season the numbers they once took in a matter of hours.
Based on recreational fishing survey data, DPI researchers estimate that the 2008 bag limit reduction for elephantfish, from three to one, would have reduced the annual retained catch consistently by an average of 41% if applied over the previous 10 years.
Projected into the future, this could be significant in terms of both the elephantfish stock and the fishery. If the unintended impact of the reduction of the bag limit for elephantfish on fishing charter clients during autumn flows on to other anglers, the important outcome – recovery of the elephantfish stock – is more likely to be achieved.Reads: 1359