New research on low trophic level fisheries to help certifiers

July 26, 2011 14:57

Science, the international weekly science journal, has published online Impacts of fishing low trophic level species on marine ecosystems, a ground breaking scientific analysis. The study was initiated and substantially funded by the Marine Stewardship Council with the aim of ensuring its guidance to certifiers on assessing low trophic level fisheries meets global best practice, reports with reference to MSC.

Over 30 per cent of global fishery production is of small pelagic forage fish such as anchovy, sardine and sand eels. These low trophic level species play a significant role in food security, particularly in developing world countries, and are harvested by some of the world's largest fisheries, such as the Peruvian anchovy fishery. Low trophic level species also play a critical role in their wider ecosystem, and responsible fishery management regimes recognise the necessity for harvest strategies that will maintain dependent species at sustainable levels.

MSC consultation engages global expertise

In September 2009, the MSC initiated a twelve-month consultative process to examine best global practice in the management of low trophic level fisheries, and to review the assessment of such fisheries within the MSC Fisheries Assessment Methodology (FAM).

Alongside the consultative process, engaging the broad international community of marine experts, the MSC also commissioned a group of international scientists to carry out modelling work to evaluate the impact of different harvest strategies on low trophic level fisheries and dependent predators.

The research, led by Dr Tony Smith from the Australian Commonwealth Scientific and Industrial Research Organisation (CSIRO), used three types of ecosystem models in assessments of five different regions where understanding of ecosystem dynamics is well developed. These models were used to evaluate how different harvest strategies for low trophic level fisheries would impact on target stocks and dependent predators.

Higher stock levels minimise ecosystem impacts

The results, published yesterday, show that fishing these key species at 40 per cent of unexploited biomass can have significant impacts on ecosystems, particularly if those species are well connected in the food web or compose a large part of the ecosystem's biomass. In certain situations, the results indicate that a more precautionary target stock size of 75 per cent of unexploited biomass is needed to minimise the impacts on the ecosystem. Maintaining higher stock levels protects the needs of other species in the ecosystem without requiring fisheries to reduce their catches by more than 20 per cent.

The studies found that the relative abundance in the ecosystem and the connectivity in the food web of low trophic level species are important factors in the effects that their harvest may generate. Depleting low trophic level species that are highly connected in the food web, accounting for four per cent or greater of all trophic connections, always results in large impacts.

New guidance to enhance sustainable outcomes

The MSC's current Fisheries Assessment Methodology already recognises the critical role that low trophic level species play in the ecosystem. Currently such LTL fisheries are required to have in place conservative harvest strategies that leave higher levels of biomass in the ocean than would be expected in other kinds of fisheries. The results of this breakthrough research will allow the MSC to clarify the specific expectations for these types of fisheries. This LTL guidance is currently being finalised and is expected to be introduced next month.

Dr David Agnew, MSC Standards Director, said: "Effective fishery management systems are fundamental to securing and maintaining the health of fish stocks and marine ecosystems. The MSC is committed to ensuring that our technical policy is founded on robust science, and I would like to thank Dr Smith and his team, and the wider community of experts and engaged stakeholders who contributed to this study, which will have significant practical impact on the future management and assessment of low trophic level fisheries.

"The MSC programme is a dynamic one. When new policy is introduced we ensure that it reflects widespread scientific agreement, and is already incorporated by the most responsible fishery management regimes. Future changes to policy, such as those generated by work on benthic impacts and spatial management, will be introduced following the same transparent and rigorous processes as have been applied to the development of new low trophic level guidance."

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