FIS013: Ecosystems: predator / prey interactions

Start Date: Apr 2016

End Date: Feb 2017

Main Contractor(s): University of Strathclyde

Other Sponsor(s): European Maritime and Fisheries Fund

Extended Title: Scoping the background information for an ecosystem approach to fisheries in Scottish waters: Review of predator-prey interactions with fisheries, and balanced harvesting

Main Research Category: Environment / Ecosystem

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Project Objectives

Marine ecosystems are inevitably affected by fishing because this involves the removal of a portion of the natural production to meet the human need for food. Through most of the 20th century, fisheries management has focused on regulating harvesting to secure the long-term sustainability of targeted fish stocks, but has assumed that these exist in isolation from the rest of the ecosystem. In reality, fishing practices have, through a variety of processes, affected the functioning of the ecosystem as a whole by impacting on a wide range of non-target species. In many cases this has undermined the productivity of targeted fish stocks and compromised other qualities and services provided by the ecosystem that human societies also value. Recognition of these impacts has led to calls for urgent corrective action (Anon 2010, Dickey-Colas 2014, FAO 2003, 2005, 2006, Garcia et al. 2003, Garcia and Cochrane 2005, ICES 2005, Pikitch et al. 2004).

Several key international agreements adopted since the 1990’s, such as the 1995 FAO Code of Conduct for Responsible Fisheries, and the Convention on Biological Diversity (CBD), stress the need for the adoption of ecosystem approaches to fisheries (EAF). In 2001, 57 countries issued the Reykjavik Declaration on Responsible Fisheries in the Marine Ecosystem, which included a declaration of their intention to work on incorporating ecosystem considerations into fisheries management. The 2002 Plan of Implementation of the World Summit on Sustainable Development called for, amongst other things, the application of the Reykjavik Declaration by 2010 as one of the steps essential for ensuring the sustainable development of the oceans. Despite these good intentions and some progress in implementation in many parts of the world, in most if not all countries more progress in ecosystem research and institutional development is still needed before the implications of the approach are fully understood and credible management strategies are adopted and effectively implemented. In addition to governmental initiatives, environmental NGOs have been particularly active in raising awareness of governments and society and have proposed a number of basic principles for ecosystem conservation.

The overarching principles of an ecosystem approach for fisheries are an extension of the conventional principles for sustainable fisheries development, designed to encompass the processes and integrity of the ecosystem as a whole. They aim to ensure that, despite variability, uncertainty and likely natural changes in the ecosystem, the capacity of the aquatic ecosystems to produce food for human consumption, revenues, employment and, more generally, other essential services and livelihood, is maintained indefinitely for the benefit of the present and future generations. The FAO Technical Guidelines on the ecosystem approach to fisheries (FAO 2003) define EAF as follows:

"An ecosystem approach to fisheries strives to balance diverse societal objectives, by taking into account the knowledge and uncertainties about biotic, abiotic and human components of ecosystems and their interactions and applying an integrated approach to fisheries within ecologically meaningful boundaries."

A primary implication is the need to cater both for human as well as ecosystem wellbeing. This implies conservation of the wide range of non-target species, which make up the food web and ecosystem structures, through adaptation of fisheries to ensure sustainable use. Inevitably this will require the consideration of a range of frequently conflicting objectives where the needed consensus may not be readily attained without equitable distribution of benefits. In general, the tools and techniques of EAF will remain the same as those used in traditional fisheries management, but they will need to be applied in a manner that addresses the wider interactions between fisheries and the whole ecosystem. For example, catch and effort quotas, or gear design and restrictions, will be based not just on sustainable use of the target resources, but on their impacts on other predator and prey species and implications for the whole ecosystem.

The generic process of putting into practice an Ecosystem Approach has been set out in varying degrees of detail by a series of FAO, EU, IUCN and ICES Working Group reports (Anon 2010, Dickey-Colas 2014, FAO 2003, 2005, 2006, Garcia et al. 2003, Garcia and Cochrane 2005, ICES 2005, Pikitch et al. 2004), and is currently being summarised again by the EU-MAREFRAME project (MAREFRAME 2016). However, progress in implementing an EAF in Scotland, and in the UK in general, has been relatively limited. The process has become entwined with conservation legislation and marine spatial planning. Hence, the principal mechanism for regulating fisheries so as to ostensibly meet ecosystem objectives has been the establishment of Marine Protected Areas (MPAs). However, this falls well short of the wider goals of EAF as defined by FAO and international agreements, which demand a more fundamental review of the wider strategy for harvesting living resources from each marine ecosystem. It is not axiomatically the case that by protecting a proportion of representative seabed habitats and sensitive species from the physically damaging impacts of certain fishing gears, that the ecosystem will be harvested in a more balanced way and that the underlying productivity and functions will be protected.

The concept of balanced harvesting (BH) has been widely discussed in the scientific literature (Froese  et al. 2015, Garcia et al. 2012, 2015, Jacopsen et al. 2014, Kolding and van Zwieten 2014, Kolding et al. 2015a,b, Law et al. 2012, 2015) as a vehicle for implementing an Ecosystem Approach. The strategy aims to “distribute a moderate mortality from fishing across the widest possible range of species, stocks, and sizes in an ecosystem, in proportion to their natural production, so that the relative size and species composition is maintained” [12]. However, there is speculation as to whether the concept has any practical applicability beyond African lakes where it has been empirically demonstrated (Kolding and van Zwieten 2014, Kolding et al. 2015b, Misund et al. 2002, Jul-Larsen et al. 2003.

FAO documentation lists a range of likely impediments to implementation of an EAF in any given region (FAO 2003, 2005, 2006). Among these, insufficient knowledge of fishing and ecosystem interactions and of the response of different ecosystem components to specific management actions are listed as key concerns. Among key research areas are listed the collection of better information on ecosystem function and assessment of the impact of fishing on non-target species through by-catch and discarding, and improved knowledge of how ecological support systems (food webs, physicalbiological coupling, etc.) are linked to the provision of goods and services that benefit, and are utilised by humans. In relation to balanced harvesting, Reid et al. (2015) examined what implementation would be required in practical terms for developed and managed fisheries with price-structured markets. Their conclusion was that “BH would be possible to implement in intensively managed fisheries such as in the EU and North America, but would likely require such a degree of micromanagement as to make it operationally impractical.”

The purposes of this project were to add detail to the FAO guidance for Scottish fisheries with respect to a) background information on predator-prey interactions that are affected by fisheries and, b) the practicalities of implementing a balanced harvesting scheme in Scottish fisheries as a more ecofriendly alternative to current harvesting patterns.