Modeling interactions between top predators and fishing vessels: implications for fisheries management in a wider ecosystem

At the 2002 World Summit on Sustainable Development (WSSD) in Johannesburg, signatory nations agreed to develop and implement an ecosystem approach to fisheries (EAF) by 2012. A central tenet of EAF is that management priorities should start with the ecosystem rather than the target species, and that humans must be considered as an integral part of the ecosystems that are being managed. However, implementing an EAF poses a range of so-called wicked problems, because it is difficult to find a solution that is equitable for all components of the ecosystem. A solution may, however, be possible if a common framework can be developed within which the risks to all components of the system can be evaluated and compared. This project will contribute to that framework by developing a spatially-explicit mathematical and statistical model of the interactions between the 'predators' (grey and harbour seals, and different fishing fleets) that exploit commercially-important fish stocks in the North Sea. This model will be used to investigate the impacts of different management options on the individual predators and on the ecosystem. In particular, we will focus on the implications of changes in the management of the marine environment that are outlined in the White Paper on the proposed Marine Bill. We will use an operating model approach that describes three different sets of processes: the way in which the underlying biological system operates; the way in which this system is managed; and the way in which data from the system are collected and analysed. We will extend this approach to provide additional insight into the underlying biological and economic processes by applying computer-intensive statistical methods to fit the to data on fisheries landings and seal condition and numbers. Because operating models can take explicit account of the major sources of uncertainty in our knowledge of the system, they are therefore particularly useful for evaluating the risks associated with different management scenarios. The operating model will be developed in two phases. A set of functional responses will be used to predict the relationship between the consumption/catch of cod, haddock, whiting and herring and their abundance at a particular spatial location. A set of aggregative responses will be used to predict the distribution of fishing effort and seal foraging over space. The modelling process will be facilitated by similarities between the foraging strategies of the predators and the ways in which information on their behaviour is collected. They all derive relatively well-defined net benefits from their prey that are determined by the balance between the value of what they catch and the cost of obtaining it. We will focus on a subset of the predators whose foraging is constrained by the need to return at regular intervals to a relatively small number of well-defined locations to haul out and breed, in the case of seals, or to land their catch and refuel, in the case of the fisheries. We will evaluate their benefits and costs in a common economic framework that uses the fishing/foraging trip as the basic time unit. We will base these models on the large body of data on seal movements collected by the Sea Mammal Research Unit, and the extensive database on fishing effort in the North Sea collected under the European Commission's MAFCONS project. We will fit these combined models to data on fisheries landings and data on the body condition of seals at the major breeding colony in the North Sea. Finally, we will model the way in which new management regimes for marine resources, such as a range of protected areas and a greater emphasis on regional management, proposed by Defra are likely to be implemented. We will then use scenario analysis to predict the likely impacts of these regimes on the spatial distribution of fishing fleets and predators, on their landings and body condition, and on their prey resources.