July 2005

ARE WHALES EATING ALL OUR FISH?

Increasingly, some politicians and national delegations at fisheries organizations meetings argue that whale populations should be reduced because whales compete with human beings for ever-scarcer commercial fish resources.

Clearly, some whale species do eat some fish species - they always have. But the question is, would reducing whale populations result in bigger catches for commercial fishermen?

FACTS

• Whales do eat some fish species that are commercially fished - they also eat species that aren’t commercially fished, as well as some that are predators of commercially fished species. For example, the baleen whales of the Southern Hemisphere (accounting for some 80% of all the world's large whales) feed almost exclusively on krill for which to date there has been very little commercial demand. The diet of the baleen whales of the Northern Hemisphere also includes krill and other crustaceans for which there is little commercial demand, as well as a wide range of prey, including small fish and some commercially fished species. For example, minke whales feed opportunistically, and it is difficult to estimate the total amount of commercial fish stocks that they eat.

• There is reason to believe that reducing the number of predators such as whales may actually reduce catches of commercially valuable species, since whales also eat predators of commercially fished species.i.

• If reduced whale populations resulted in higher fish catches, fish stocks would now be likely to be far larger than they are believed to have been 100 years ago. In fact, the opposite is true – almost all commercial fish stocks are much lower now than they were a century ago, with the biomass of the large predator fish estimated to be at about only 10% of pre-industrial levelsii. At the same time, almost all cetacean populations were drastically depleted during the last century and many species are still at just a fraction of their original numbers.

• Many commercial fisheries catch and then discard a high proportion of the amount of marine resources that are landed for sale worldwide. It is conservatively estimatediv that over one quarter (27%) of catch is discarded, dead or dying annually. This is often unwanted fish species, but also can be made up of a full range of marine species including seabirds, marine mammals such as dolphins, pilot whales and seals and species groups such as invertebrates, crustaceans and sponges.

• Strengthening fisheries management is the solution to the problems of degraded marine ecosystems and declining commercial fish species within them, not attempting to selectively fish particular trophic levels to try to 'restore' marine ecosystems. In strengthening fisheries management and implementation, Ecosystem-Based Management (EBM) has been identified as a management approach that is likely to succeed where many other initiatives have failedv. EBM makes use of the tools available in modern fisheries management such as catch and gear controls and closed areas integrating them within a framework that is designed to understand the limits of marine ecosystems and conserve their long term function as well as their productive potential.

• EBM is intrinsically a precautionary approach, being built upon the open recognition that ecosystems are complex systems with their understanding inherently uncertain. For example, a minimum 28 million pathways are estimated to exist through the Benguela ecosystem food web1, which illustrates the practical impossibility to artificially re-design natural ecosystems catering to human needs. Although Japan and other whaling nations have referred to the need for “ecosystem-based management” in the context of whales and whaling, in truth ecosystem engineering approaches, such as the culling of predators, goes against the rationale of Ecosystem-

1 Yodzis, P. (1998) Local trophodynamics and the interaction of marine mammals and fisheries in the Benguela ecosystems. Journal of Animal Ecology 67: 635-658

For further information contact: WWF-International, Avenue du Mont-Blanc, 1196 Gland, Switzerland Email: [email protected] Website: www.panda.org

Page 1 of 2

Based Management and are not scientifically supported2. In this sense, when dealing with culling, the FAO Guidelines on the Ecosystem Approach to Fisheries recommend that in case of overfishing:

“consideration should first be given to the rebuilding of target species populations through other, more conventional, fisheries management measures”.

• Many commentators have drawn attention to the need for the international fisheries management community to recognise that there is no scientific validity to the removal or suppression of populations of top predators such as cetaceans. This is too simplistic an approach and a clear threat to ecosystem integrity and health. Pauly et al., (2002)iii provide useful comments on the arguments used to promote the culling of whales to help fish resources:

“…predators operate within finely meshed food webs whose structure (which they help to maintain) tends to support the production of their prey. Hence the concept of ‘beneficial predation’, where a predator may have a direct negative impact on its prey, but also an indirect positive effect, by consuming other predators and competitors of the prey. Thus, removing predators does not necessarily lead to more of their prey becoming available for humans. Instead, it leads to increases or outbursts of previously suppressed species, often invertebrates, some of which may be exploited (for example, squid or jellyfish, the latter a relatively new resource, exported to East Asia), and some outright noxious.”

CONCLUSION

There is no scientific basis supporting an ecosystem engineering approach to fisheries management. On the contrary, a precautionary ecosystem-based approach is urgently required. The only solution to the problem of declining fisheries is to rebuild overexploited stocks and ecosystems through relieving fishing pressure, improving gear selectivity and fishing exploitation patterns, protecting habitat and making a wise and generous use of protected areas and no-take zones.

There are already frameworks in place to help achieve this, including the United Nations Fish Stocks Agreement, Ecosystem-Based Managementv, The FAO Code of Conduct for Responsible Fisheries, and if credibly developed and applied, the FAO Guidelines on The Ecosystem Approach to Fisheries.

i UNEP: Marine Mammal Action Plan Protocol for assessing proposals for culling marine mammals, 1999 ii Myers, R.A., and Worm, B.(2003) "Rapid worldwide depletion of predatory fish communities". Nature Vol 423 Pgs 280-283 iii FAO State of Fisheries Report 2001 v Ward, T., Tarte, D., Hegerl, E., and Short, K. (2002) “Policy Proposals and Operational Guidance for Ecosystem-Based Management of Marine Capture Fisheries”. WWF International. vi Pauly, D., Christensen, V., Guenette, S., Pitcher, T., Sumaila, R.U., Walters, C.J., Watson, R., and Zeller, D. (2002) Towards Sustainability in World Fisheries. Nature. Vol 418. Pgs 689-695.

2 Yodzis, P. (2001) Must top predators be culled for the sake of fisheries? Trends in Ecology and Evolution 16: 78-84

For further information contact: WWF-International, Avenue du Mont-Blanc, 1196 Gland, Switzerland Email: [email protected] Website: www.panda.org

Page 2 of 2