Balanced Harvesting – an alternative interpretation of selectivity

Published on November 19, 2012

At a workshop in the European Parliament organised by Struan Stevenson (ECR, UK), the theory of balanced harvesting was discussed. Its proponents argue that fishing across a range of species, stocks and sizes could increase yields, address food security better than selectively avoiding juvenile fish and bycatch. However, they warn that the state of fish stocks and scientific research would need to be greatly improved before such a management system could be implemented.

In the articles “reconsidering the consequences of selective fishing” and “on balanced exploitation of marine ecosystems: results from dynamic size spectra”, published earlier this year, academics suggests that fisheries management should focus more on the productivity of stocks.

They argue that as less energy is required to produce smaller fish, avoiding these through selectivity is wasteful and reduces yields. Instead the old, large, and fecund fish should be selectively left in the ecosystem as breeders, and all bycatch be caught and utilised.

The authors of the studies note there are several factors that need to be in place before it could be implemented. Most importantly, to negate the risk of fishery collapse, no stocks can be overexploited and improved scientific data would be required for potential catches.

Given that of assessed EU stocks, 63% in the Atlantic are overfished, 82% in the Mediterranean and 4 out of the 6 stocks for which scientific advice is available in the Baltic, considerable work is required to meet this criterion. In addition, Commission figures show that “scientific advice about overfishing is missing for about two-thirds of the total allowable catches” and this figure excludes data for bycatch of non-commercial species. Thus, the EU is a long way from managing stocks at the Bmsy (biomass that enables a fish stock to deliver the maximum sustainable yield).

As we have seen with the North Sea cod stock, where during the 1990s 93% of fish were caught before they had the opportunity to spawn, a combination of too high fishing pressure and poor selectivity causes stock collapse. This underlines the importance of achieving the MSY target as a prerequisite to increasing yields.

Stevenson argues that balanced harvesting “may be the answer to achieving the ‘Holy Grail’ of fishing above Maximum Sustainable Yield, so that fish stocks are able readily to replenish themselves and catches and profits rise accordingly”. However, producer organisation representatives have dismissed the concept because “targeting more small fish will reduce their revenues and promote a market for small fish”. They argue that minimum landing sizes allow fish to spawn at least once before they are caught, acting as an insurance against stock collapse.

Consumer demands for larger, high quality fish also encourage selectivity measures to protect juveniles. Although yields could increase under balanced harvesting, fishermen and consumers would be short-changed unless market demand for younger fish increased and prices rose accordingly.

The balanced harvesting theory may be counterintuitive and goes against much of current EU policy, which seeks to encourage selectivity and protect juveniles; however, it is correct that measures to protect the largest, most fecund females would be beneficial for the resilience of stocks.

There is also logic to the theory of increasing yields by focusing efforts on juveniles. In much the same way, farming could increase yields by producing more veal from calves rather than beef from cows. Yet, if these increased juvenile landings were used as fodder for the aquaculture industry it would be an even more inefficient use of resources than allowing fish to mature before being caught.

In the future there may be potential for balanced harvesting to be used in EU fisheries, although as the theory encourages landing a wider range of species, further research is necessary.  We would need to know the Fmsy for all stocks as well as their current biomass, while fishing would need to be highly selective so as to fish each stock, and each age class within each stock, at the correct rate. This would in theory lead to a more balanced age distribution within fish stocks, a commitment for the EU to follow under the Marine Strategy Framework Directive.

For now though, the EU needs to continue to focus on rebuilding stocks under the MSY principle.

Attached documents: