A group of international scientists is currently looking into whether the fisheries in Northern European waters are now seriously under-fished. Dr Henrik Sparholt, who for many years held a senior position within ICES, recently presented an outline of a research project to understand this development with more precision, to a meeting of the Executive Committee of the North Sea Advisory Council.
A growing understanding of how ecosystems work and the gradual integration of this new knowledge into management advice lies behind this new approach. None of this was particularly relevant when our stocks were overfished but the situation has radically changed in the last decade.
According to Dr Sparholt, ICES science confirms that overfishing has ended in the N-E Atlantic fisheries, major fish stocks have been rebuilt and that exploitation is considered to be around one-third of what it was 5-8 years ago.
In his presentation he set out that under these circumstances, multi-species and ecosystem interactions – essentially who eats who in the marine ecosystem – becomes much more important and it is therefore correspondingly important that this shift is taken into account when setting harvest rates. Current single species assessment models are unrealistic because they do not take into account predation effects. The project’s aim is to bring more realism into the science and into the management advice – it is then up to fisheries managers what they do with that advice.
He explained that a shift to an ecosystem Fmsy is already underway with these type of considerations already being taken into account in the massive and successfully managed Barents Sea and Icelandic cod fisheries. In the former, interactions between cod, capelin and herring are already taken into account, and in the latter, interactions between cod, shrimp and capelin are factored in. Ecosystem considerations are not yet taken into account in EU fisheries management decisions when setting TACs.
Increasing fishing mortality on cod to 50% above single species Fmsy, in order to limit predation on herring or reduce the scope for cannibalism, which can be quite prevalent with cod, is the type of management action that might follow integration of ecosystem factors into management advice.
Dr Sparholt highlighted the costs of under-fishing but also pointed to the drawbacks of harvesting on the basis of ecosystem Fmsy – more year-on-year variability. As major predators, cod and hake are likely to be two stocks that would see the biggest change in such a shift, with mackerel, herring and plaice seeing much less change.
‘We have known for some time that species interactions are important and that these are not yet being taken into account in most management decisions in our fisheries,’ said NFFO Chief Executive Barrie Deas.
‘When fishing pressure was too high, this did not matter so much but this project suggests that consideration of how to use the new knowledge is now becoming a matter of urgency. It is vital to avoid overfishing but equally there is an ethical imperative not to waste fish that could be generating income and feeding people.’
‘Scientists and the fishing industry have already begun to consider the implications of rebuilding of the cod stocks in our waters for the populations of high-value crab, lobster and nephrops (prawn) fisheries, which in general have been doing very well during the period when demersal stocks were depleted. The shift from single stock to multi-species /ecosystem, scientific advice is unlikely to be like flicking a switch.’
‘It is more likely to involve a progressive inclusion of ecosystem factors into management decisions. For example, the level cannibalism in cod is likely to depend on the extent to which adults and young fish occupy the same marine space. Following the best available scientific advice is hard-wired into our fisheries legislation and our political decision-making processes. It looks like in the future we will have to be as concerned as much with controlling under-fishing as we have in the past been about dealing with over-fishing.’
