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How fish may survive and even increase their populations

By JW Dowey - 09 Mar 2016 9:5:0 GMT
How fish may survive and even increase their populations

This is one of the large Indo-Pacific fish that migrate moderate distances near LMMAs in order to spawn, the brown-marbled grouper, Epinephrus fuscoguttatus. Grouper image; Credit: © Shutterstock

Peter A Waldie of James Cook University in Australia and colleagues from CNRS-EPHE-UPVD in Perpignan, MarAlliance in Belize King Abdullah University in KSA, The Australian and Papuan Nature Conservancies, the Australian Research Council and the University of Queensland have released a paper that could have great impact on management of marine reserves.Restricted grouper reproductive migrations support community-based management is published in the Proc.Roy.Soc.B today.

Marine areas such as the LMMA are no-take areas for fishermen, giving populations of fish a chance to recover from past depredations and current stresses. While the Pacific locally managed marine areas are only 1 square km in area on average, this paper indicates that large fish species living on reefs migrate over large distances for spawning. The grouper, Epinephelus fuscoguttatus, was used as a guinea pig to see how tagging 29 of them, combined with acoustic telemetry, could show up their reproductive migrations and catchment areas.

Results indicate that a total protected area of only 16 km2 cannot maintain the population even though migration paths were quite short. Expanding from a current 0.2km2 to a mere 1-2 km2 can be calculated to protect from 30-50% of the spawning population while they are in transit (non-spawning.)

It is obviously not only groupers that form these transient spawning aggregations. Otherwise solitary animals migrate along regular paths that can be protected if we want to conserve the species. These large groups obviously attract not only local fishermen, but factory ships and other large industrial fishers. Hence the worldwide and systematic collapse of these FSAs (fish spawning aggregations.) Local extinctions have occurred for many of the well-known species we all eat. The fish larvae that would be produced from these FSAs could prove to be the saviours of almost every major fished species, if we were to organise fishing on a scientific basis. The relevant but untenable interests of commercial fisherman simply have to be ignored. If profit is our only motive, then long term planning goes down the marine plughole.

The need is for social surveys to assess conservation effectiveness and detailed information on migratory movement. Tok pisin is the local patois of the Papuan population on the island where surveys were carried out. Half of the villagers were surveyed orally in 6 settlements, involving male or female head of households. Suggestions were asked for as well as basic questions, including their knowledge of poaching (one of the tagged fish was poached in the LMMA.) Only 45% of the respondents had supported the LMMA at first, but most said that it had become beneficial to their livelihoods and now support it. 72% thought the system could be improved in various ways, although 9% admitted to poaching inside the LMMA. It did emerge that only locals actually poached fish.

The indications are that this particular LMMA is very effective in its protective function, despite the lack of any policing. Modest expansion just outside the current LMMAs would however provide huge increases in conservation capability, alongside more fish for the local fishermen. Fish migrating moderate distances could all be helped by increasing the smallest LMMAs in the Pacific islands to just the average size. People can relatively quickly find success from the increased fishing availability while conservationists can examine even the rarer fish species to discover how they are affected by any rules or local habits. The whole ecosystem benefits, including predators, reefs and all those undiscovered links which we still struggle to understand, deep in the coral.

While subsistence fishing is closer to conservation-minded people, the tragic loss of whole species still haunts the global fishing industry. The efforts being made are truly enormous, especially as cod and the many tuna species struggle to survive, as in this article.