Super-trawler will deplete fisheries

Localised Depletion Still a Problem for Super-trawler Proponents

One of the main concerns of  opponents of the proposed introduction of the super-trawler into Australia’s small pelagic fishery was the failure to properly manage the risk of localised depletion. Recent developments have not reduced this concern. There is currently not even an agreed definition for localised depletion in Australia’s small pelagic fishery.

Most people with an interest in fishing or the marine environment could probably come up with some kind of definition of localised depletion. It is much harder to create a definition that is useful in managing the associated risks.

In Australia’s small pelagic fishery (SPF) this is relevant because, if local stocks of fish are reduced too far, there is an increased risk of ecological impacts (not enough food for seals or dolphins, for example) or damage to recreational fishers (removal of too many small pelagic fish from Tasmanian waters could mean that tuna and similar fish won’t come close enough to shore for the recreational fishery).

The lack of information about fish movements within stocks of all four species (redbait, blue mackerel, jack mackerel and Australian sardine) targeted by super-trawler proponents makes it very difficult even to assess, let alone manage this risk.

It is currently impossible to know how long it will take for an area to recover from fishing as we do not have any information on where or how fast these species move within their range.

Without this information or more knowledge about the way they respond to fishing pressure, it becomes very difficult, perhaps impossible, to develop a strategy to deal with localised depletion. The introduction of a super-trawler or other large vessel into this fishery would simply exacerbate the problem, as vessels that can take a higher catch over a shorter period of time are likely to result in greater localised depletion. The fact that any super-trawler (or other large commercial fishing vessel) is likely to be attracted to the same aggregations of fish that attract marine mammals, seabirds and tuna obviously increases the chances of impacts on the ecosystem and recreational fishers.

Below is a recent draft definition for localised depletion.

For the purposes of the management of the Small Pelagic Fishery, localised depletion is a persistent reduction in fish abundance in a limited area, caused by fishing activity, over spatial and temporal scales that negatively impact on predatory species and/or other fisheries.

Explanatory notes: Risk of localised depletion is highest for target species with low mobility (e.g. abalone) and lowest for highly mobile species (e.g. pelagic fish). Predatory species with limited foraging areas, especially central place foragers, are most likely to be impacted by localised depletion. Localised depletion is less relevant to highly migratory species or species with large foraging areas. 

Geographical barriers (headlands, straits) can increase the likelihood of localised depletion by limiting movement rates. Localised depletion is not a reduction in the overall range of a target species due to fishing down or over-fishing the stock.

Localised depletion is not a reduction in abundance due to natural movement or population size of target species. User conflict issues that do not arise from localised depletion should be considered and resolved separately from any issues involving localised depletion alone.

In the context of the Small Pelagic Fishery, this definition identifies what we are managing for (i.e. potential impacts on predators and catches of SPF species in other fisheries). NB: Broader ecological implications of the Small Pelagic Fishery can be managed by applying low exploitation rates.

(From Small Pelagic Fishery Resource Assessment Group (SPFRAG) Minutes for Meeting #17, 11 to 12 March 2014.

To be fair, this is a draft, but there are still fundamental problems that completely undermine its usefulness. In particular, it is worth noting that this lacks anything that can be quantified. Therefore, there can be no performance measures, no way to measure whether localised depletion has occurred or the success or failure of management measures that might be used to avoid the problem of localised depletion. If something can’t be measured, it is impossible to manage.

The Australian Fisheries Management Authority (AFMA) has been aware of this issue for years. As a member of the AFMA’s SPF Resource Assessment Group (SPF RAG) and SPF Management Advisory Committee (SPF MAC) before it was dissolved, I have repeatedly raised this as a concern over many years, together with my colleague from the recreational fishing sector, pointing out that there is not enough information on fish movements to develop scientifically based management.

The super-trawler debate came to a head in 2012, culminating in the federal government’s super trawler ban. Much of the community concern was related to the local impacts of a super-trawler operating in this fishery. Localised depletion was clearly at the forefront of concerns raised by recreational fishers and conservation groups.

Despite this, there has been no new research or other information on the movement of target fish species within stocks. There is still no way to predict how long it will take for local fish populations to recover from fishing. There is also no way to assess whether Bass Strait or other geographic/oceanographic features are a barrier to fish movements to the point where recovery of local fish populations, in Tasmania for example, is hindered.

Instead we are left, almost two years after the super-trawler ban, with a draft definition for localised depletion that provides no guide as to how it might be measured or managed, and no expectation that this issue will be adequately dealt with in the foreseeable future. It must be stressed again that there are no meaningful management measures in place to reduce the risk of localised depletion to acceptable levels. There is no way to predict how soon local populations will recover from fishing activities. AFMA currently does not even have an agreed or useful definition for localised depletion.

It appears that, rather than having any criteria that can be measured, localised depletion is to be managed by spatial and/or temporal closures, or move-on requirements, under which vessels are supposed to move after a certain amount of fish have been caught. Currently there are no actual details about any of these measures so it is impossible to make any proper assessment of their effectiveness. And, of course, it must be remembered that, without actual data on fish movements and some indication of likely recovery times after fishing, it is currently impossible to justify these forms of management on the basis of scientific evidence.

Localised depletion is just one of the major problems associated with this fishery; these are some of the others:

- The lack of any commitment by AFMA to undertake regular and ongoing (Daily Egg Production Method (DEPM) stock assessments even if industrial scale exploitation of fish stocks were to be permitted. DEPM based stock assessments are the best way to estimate the numbers of these fish.

- The reliance on stock assessments that are based on old DEPM surveys. The rate of climate change in the marine environment, in particular in south-eastern Australia, increases the need for stock assessments to be based on recent data.

- The lack of information on fish movements within stocks of target fish species. Local research that can inform the management of localised depletion is lacking. There is no way to predict how soon local populations will recover from fishing activities.

- No satisfactory commitment from AFMA to ongoing observer coverage or other monitoring that is acceptable to many stakeholders.

- AFMA’s continued refusal to allow public scrutiny of fishing activity.

 - Failure to ensure that seals and dolphins are adequately protected from drowning in trawl nets and that animal welfare is given the consideration it deserves.

I expect that, in the near future, various super-trawler supporters will suggest that localised depletion has been considered and dealt with to their satisfaction. Given the current absence of scientific information on fish movements and lack of any mechanism that would identify or measure localised depletion, I believe that claim would be incorrect. And the other problems associated with the fishery remain and are reason enough to stop the entry of any super-trawler into Australia’s small pelagic fishery.

Finally, I would not be surprised if there is a move to bring in a marginally smaller vessel, or a number of large freezer boats that don’t quite meet the federal government’s definition of ‘super-trawler’ and are therefore not subject to the ban, but which will likely pose a similar risk to fish stocks and the marine environment. I think that there are many reasons why that would be a bad idea.

Jon Bryan
Tasmanian Conservation Trus