NSRAC DWG 12/11/2013

Paper 7.1 For Information

Multispecies fisheries management

An alternative approach


There is nothing new about the notion of multispecies fisheries management, and various ideas have come and gone over recent decades. Two factors make renewed discussion appropriate:

CFP reform, which has highlighted the catastrophic failure of existing fisheries management systems in the North Sea and other waters; and

Scientific research within ICES on multispecies models.

In this paper we suggest another approach to multispecies management. We have not attempted to describe a perfect system or even to answer all the questions this approach would raise. We are simply looking at the issue from a ‘blank sheet of paper’ viewpoint as a means of stimulating long-term thinking. The North Sea RAC has a very forward-looking bias, and these ideas may have some place in that perspective.

As was pointed out at the DWG meeting on 9 July, we currently have single-species management modified by multispecies effects. At that same meeting it was noted that multispecies approaches could have serious drawbacks if introduced to the way in which quotas are currently set. We would wholeheartedly agree with both points.

The underlying problem remains intact, however. Any management system that fails to take account of the fact that different species of fish intermingle and interact with each other (and with other marine organisms) will be at best inefficient, and at worst

– as with a discard ban – counterproductive.

Unscrambling the words

In a fisheries context, it is important to recognise that the term ‘multispecies’ encompasses several different issues.

As there are ecological links between different species of fish (and other animals), a change in the abundance of one species can, directly or indirectly, influence the abundances of others.

In some fisheries, several different species are caught simultaneously (in the same place, at the same time, with the same fishing gear).

Changes in fisheries management measures may shift fishing effort from one species (or group of species) to another.

Furthermore, the term ‘multispecies’ is understood in different ways. ICES is thinking primarily about ecological links between species, while fisheries managers will be more concerned about species that happen to be caught together and that may or may not be ecologically linked.

Any discussion of multispecies fisheries issues needs to recognise and accommodate all these different aspects. A system that focuses solely on species that are ecologically linked will not address all of the multispecies issues faced by the fishing industry.

Ecologically linked species

Most fish are both predators and prey, eating other marine organisms and at risk of being eaten themselves. Ecological connections extend beyond commercial fish stocks, of course, and include the full range of marine organisms from plankton to invertebrates, mammals, seabirds and non-commercial fish species. These links mean that changes in the abundance of one species can affect the abundances of others, potentially causing effects that ripple through the food web.

By way of illustration, ICES research on the North Sea food web suggests that the yields of many fish species are strongly affected by the abundances of cod and saithe. Because cod eat haddock and whiting, an increase in the abundance of cod is likely to result in a decrease in the abundances of haddock and whiting.

Furthermore, if haddock and whiting become less abundant, the species that they prey on (such as herring, sandeels and pout) are likely to become more abundant.

It follows that any management measures that change the abundance of one species are likely to have knock-on effects that change the abundances of other species. Yet current management focuses on each stock in isolation.

Different species caught together

Some species of fish tend to congregate into large single-species shoals, meaning that fishers are often able to catch only that species. Examples of such fisheries include those for herring and mackerel, although even here some intermixing of species can occur.

Other species of fish intermingle much more promiscuously, with several - perhaps many - different species being present in the same area at the same time. This is especially true of demersal species. A further complication is that the degree of intermingling can vary in both space and time.

These different species may be of similar size and have similar behaviours, which severely limits the ability to separate or select them through modifications to fishing gear or fishing behaviour. Instead of catching only the species they want, fishers are likely to catch a more or less random selection of the fish that are present in the area they are fishing.

As an example, records from a Shetland whitefish vessel show that when fishing around Shetland over the last decade it caught an average of five different commercial species of fish in each tow, with a maximum of 12 species. In contrast, when fishing on grounds off NE Scotland, the same vessel caught an average of only two species per tow, with a maximum of five.

Particular problems arise when quotas for particular species are out of line with their relative abundances on particular fishing grounds. Those problems will only worsen under the discard ban.

The fact that species caught together may not be linked, or may only be distantly linked, ecologically means that this aspect of a multispecies fishery may not be captured by the

‘ecological’ approach discussed above. Multispecies fisheries management cannot be limited to species that are ecologically linked.

Displacement of fishing effort

Under the current regime, management measures can result in fishermen changing their fishing practices - such as the areas fished or species targeted - with unintended and potentially negative consequences.

An example of this is the change in fishing patterns by some Scottish whitefish fishing vessels as a result of the Cod Recovery Plan. These vessels previously targeted monks (anglerfish), a high-value species but one that is relatively sparsely distributed, meaning a low catch rate. Under the effort restrictions implemented

under the CRP, these vessels found that the time they were allowed to spend at sea was not sufficient for them catch all of their monk quota. As a result they had to switch to targeting higher catch rate (but lower value) species such as haddock and cod.

This illustrates how a single-species management measure can have unintended consequences. It can reduce fisheries diversity and may actually increase pressure on the species it was supposed to conserve.

An alternative approach

Existing multispecies approaches consist mainly of attempts to bolt together existing single species management systems. As some DWG members have already pointed out, such attempts are likely to result in management systems that are complex and potentially counterproductive.

We would urge thinking on new management systems developed from first principles. They would have to be more pragmatic, more flexible and less prescriptive than the existing regime, with a reasonable balance between complexity and practicality. They should also be more fisheries-oriented and take a longer-term view of the state of stocks.

We accept the ‘pie in the sky’ aspect to our arguments. But all we are doing is suggesting avenues for long-term thinking, and we do not minimise the problems alternative approaches could create. And the discard ban was pie in the sky at one time…

We therefore suggest three underlying principles

The abandonment of attempts to manage individual species

A focus on managing groups of species (‘meta-stocks’) that are caught together.

An acceptance that the abundances of individual species will fluctuate over time.

How it might work

The focus of multispecies fisheries management should be on groups of species that are caught together as single entities (management units), rather than individual stocks. These groups of species could be referred to as ‘meta-stocks’. Each metastock would comprise the principal species that are caught together in a fishery, and not just those that are closely linked ecologically.

Management targets - such as spawning stock biomass (SSB) and fishing mortality rate (F) - would be set for each meta-stock rather than for individual species. Within each meta-stock, individual species would be allowed to fluctuate within relatively

wide limits. Consideration would need to be given to any ecological links between meta-stocks.

Similarly, fishing opportunities would be set in relation to the meta-stock rather than to individual species. Fishers would then receive allocations of quota for the metastock: the system would limit the total quantity that could be caught of all the species in the meta-stock, but would not attempt to dictate how much could be caught of each individual species within it.

In practice, the quantity that is caught of each species would be dictated largely by the relative abundance of that species within the meta-stock. This would avoid a major drawback of the present regime, where the relative size of quotas does not match the relative abundances of individual species.

A variant would be to assign different values to different species. Even with single overall meta-stock quotas, some species could count for more or less than others.

For example, a unit of cod might count more than a unit of haddock, which in turn might count more than a unit of monks, and so on.

Stock assessments

Within each meta-stock, only the principal species would be subject to annual stock assessments. These results would inform the assessment of the state of the metastock itself. Minor or ‘other’ species would be monitored on a less frequent and less detailed basis. This would allow scientific resources to be targeted on the most important species, and would avoid the problems created at present by efforts to manage ‘data deficient’ stocks.

The discard ban: a game-changer?

Previous discussions on multispecies management have often focused on setting some form of aggregate quota (by adding together individual single-species quotas, for example) and allowing fishermen some flexibility in how much of each species they can catch. One of the arguments against this approach has been that fishers could then expend their full multispecies quota on a single species, discarding all other species caught.

Under a discard ban any such targeting will not be possible. Instead fishermen will have to accept the package of fish that they catch in any case.

Associated regulations

With limits on catches and a ban on discards there would be no need for general limits on fishing effort. This would allow fishers greater flexibility about how, when and for what they can fish; it would also remove the impediment to fishing for low catch-rate species, such as monks.

Most technical measures would probably be retained, such as mesh size regulations to minimise catches of small or undersized fish.

To avoid excessive catches of particular species, especially of small individuals or spawning aggregations, there may be a need for some form of spatial management; probably in the form of temporary or permanent closures of specific areas.

Temporary closures could be based on the Norwegian model, with reporting arrangements to trigger closures and incentives for fishing vessels to move elsewhere.


This paper is not aimed at wishful thinking for the sake of it. It is an early (and doubtless flawed) response to two factors: the continuing shambles of single-species fisheries management, which can only worsen under a discard ban; and fears that a science-based multispecies approach could prove a blind alley, as it focuses on ecological links rather than species that happen to be caught together.

It is our view that it would be worthwhile developing a fisheries-based model that could be used to evaluate and test a multispecies fisheries management system of the type described above. At the very least, it could help shift the present thrust of work at ICES and elsewhere towards models that could improve fisheries management as well as our understanding of the ecosystem. Management requirements should be driving ICES; it should not be for ICES to determine its own direction of travel.