E. Conservation and Management

Transcription

1 E. Conservation and Management The genesis and extinction of species is a natural process throughout the history of life on Earth. Indeed, our planet has witnessed several mass extinctions that have resulted in the collapse of a substantial portion of the ancient biotas. Human activities, however, have added a new facet to the extinction process. In particular, the irrational use of technology and resources during the twentieth century, especially associated with rapid industrial development, has generated an enormous impact upon the environment. As a result, many species, including marine mammals, have become endangered. In the case of marine mammals, conservation problems first arose through direct exploitation. In their hunger for meat, blubber or skin, humans wiped out the Steller's sea cow (Hydrodamalis gigans), from the North Pacific and Bering Sea, as early as 1768, and, more recently, the West Indian monk seal (Monachus tropicalis), from the Caribbean around Subsequently, the lucrative benefits derived from large-scale whaling also led many cetacean species to the verge of extinction. Fortunately, several factors have worked to improve the situation. First, whale-derived products progressively lost their value in favour of industrial substitutes. Second, the International Whaling Commission (IWC) was created in 1946 following the International Convention for the Regulation of Whaling. Formerly devoted to regulate whale captures, this institution has increasingly become involved in the preservation and recovery of cetacean populations, an aspect that eventually resulted in a moratorium for commercial whaling in 1982 that has been largely in effect ever since (although not entirely observed, as evidenced graphically by the recent disclosures that the former Soviet Union continued hunting the protected blue and right whales during the 1950s- 1960s, deliberately misreporting zero catches - Yablokov, 1994; Zemsky et al., 1995; Tormosov et al., 1998). Throughout its history, the IWC has dealt with several proposals for stock management in commercial whaling, eventually adopting the revised management procedure (RMP) that its Scientific Committee proposed in 1991 (IWC, 1994; Cooke, 1994; Gambell, 1999). In many ways this was a model of how to incorporate the precautionary principle into the science of managing exploited populations. Catch limits were established usually at less than 2% of estimated abundance (occasionally up to 5%), and target levels of exploited stocks were set at 72% of initial abundance. A major goal of the RMP was to allow depleted whale stocks to recover and ensure that no additional stocks would fall below 54% of their initial abundance. Of course, one inevitable weakness in any management plan is our poor knowledge of initial abundance for any whale stock, and the continued 457

2 458 Marine Mammals: Biology and Conservation difficulty of obtaining precise estimates of current abundance and catch rates. Even if these problems could be solved, there is always the economic drive towards over-exploitation of resources which lack ownership (and therefore lack direct management responsibility), particularly in situations where it may be more beneficial financially to exploit to extinction, and reinvest the profits elsewhere, than to harvest on a sustainable basis (Clark, 1976). In Chapter 13, Enrique Crespo and Martin Hall discuss several aspects of such management problems with particular emphasis on ecological and economic interactions. They highlight the ecological problems faced by poorer countries around the world, emphasising how so many resources are exploited in those countries for export to the developed world, threatening net losses of regional biological production. The upwelling ecosystem of western South America, for example, transfers annually million metric tonnes of biomass to other ocean basins. At the same time, they point out that the seas adjacent to Japan receive 3.25 million metric tonnes annually. Fishing activities may also have important repercussions upon cetacean and pinniped populations due to direct competition for resources. Although the effects are often difficult to demonstrate, Steller's sea lion populations of the North Pacific, for example, have been dramatically affected by this problem (see Chapter 13). Today, although the fishing industry targets mostly fish and marine invertebrates, there is still a substantial indirect mortality of cetaceans and other vertebrates because of incidental capture by different fishing gears - particularly driftnets, widely used in all oceans, and purse seines, typically employed by the tuna fishery in the eastern tropical Pacific Ocean. In particular, gillnet fisheries have led the vaquita (Phocoena sinus) to become the most threatened cetacean species (it is included as "critically endangered" in the World Conservation Union list). Martin Hall and Greg Donovan address issues of fisheries bycatch and their management in Chapter 14. They introduce the concept of potential biological removal (PBR), which was developed in the United States during the 1990s under the Marine Mammal Protection Act. Its aim was to estimate the number of individuals that could be 'safely' removed annually from a marine mammal population whilst maintaining an optimum sustainable population level (Wade, 1998). In practice, the goal has been to maintain populations above their Maximum Net Productivity Level, assumed to lie between 50-70% of carrying capacity. It has been applied particularly to the bycatch question, using information on abundance, bycatch and population growth rates. Over recent decades, other human-related factors have been causing a great impact upon some cetacean species. Habitat degradation has led the

3 Conservation and Management 459 Asian river dolphins - the baiji (Lipotes vexillifer), the Ganges river dolphin (Platanista g. gangetica) and the Indus river dolphin (P. g. minor), to the verge of extinction (Reeves and Leatherwood, 1994). On the other hand, pollution, caused by a number of elements, such as heavy metals, organohalogenated compounds, oil spills, and acoustic pollution, has reached alarming levels in some geographic areas, and may be having detrimental effects upon marine mammal population growth. Various aspects of the problem of pollution are dealt with in detail in a book by Geraci and S1. Aubin (1980), in the special issue of the IWC devoted to cetaceans (Reijnders et al., 1999), and in a review chapter on environmental contaminants and marine mammals by Thomas O'Shea (1999). Here in Chapter 15 of this book, Ailsa Hall considers the special case of organohalogenated contaminants in marine mammals, and highlights the difficulties of obtaining direct experimental evidence of detrimental biological effects of pollutants. A special form of pollution is that of sound disturbance. For around ten million years, marine mammals have evolved in a relatively quiet world accompanied only by the sounds of other animals, the occasional earthquake or some other natural perturbation. Only in the last hundred years have our oceans and rivers been disturbed in any substantial way with additional sounds created by mankind. In particular, man's use of the marine environment for commercial, industrial and recreational purposes has led to a considerable increase in the level of background sound (Urick, 1986), and created potential problems for many marine mammal species (Richardson et at., 1995). Following the more recent philosophy that human development must be sustainable, whale watching, an economically profitable business that contrasts with the old whaling tradition, has proliferated. This type of ecotourism industry has experienced a recent boom in many areas of the world often without clear regulations. However, the current large-scale nature of this activity begs sound control and the creation of a universal ethical code for people approaching the animals (IF A W et al., 1996; Evans, 1996). In Chapter 16, Bernd Wursig and Peter Evans address the topic of sound disturbance and its effects upon cetaceans, the most vulnerable of marine mammal taxa, putting this in the context of other conservation threats which in many cases may be more serious. They point out that the effects of industrial, military, ocean science and directed human tourism can each be quite different, and so require separate examination. Sometimes those effects may cause physical damage to hearing, and of course the vessels generating some of the sounds can pose the additional threat of direct harm through ship strikes (a problem facing particularly the slower moving species like sperm whale and pilot whales, and which is a major threat to the

4 460 Marine Mammals: Biology and Conservation survival of northern right whales and Florida manatees). Disturbance can have obvious short-term effects - avoidance of the sound source and other changes in behaviour may often be noted; but it is much more difficult to identify whether they have long-term implications upon life history parameters like survival and fecundity. The final chapter by Bernd Wiirsig, Randall Reeves and J.G. Ortega Ortiz examines a new conservation problem recognised recently - the possible effect of Global Climatic Change upon marine mammal populations (see also Tynan and Demaster, 1997; IWC, 1997; Wiirsig and Ortega-Ortiz, 1999). As a result of various human activities (emissions of ozone-depleting substances, increasing use of hydrocarbons for energy and fuel, and large-scale deforestation and desertification), the world is experiencing climate change to the extent that by the end of this century, temperatures are estimated to rise by C, and overall sea level to rise by anywhere between 9-88 cm (Intergovernmental Panel on Climate Change, 2001). Obvious consequences will be the melting of polar ice, drowning of coastal plains and low lying islands, and changes to shallow seas. This will affect breeding sites for various pinniped species, and polar bears, coastal cetaceans and sirenians may find it difficult to adjust to loss of important feeding and breeding habitat. Shifts in areas of primary productivity may lead to distribution changes for many marine mammal species, whilst an increase in the frequency and velocity of storms, and more extreme seasonal fluctuations in local climate (e.g. El Nino Southern Oscillation events) may have further more indirect impacts. In conclusion, a variety of human activities negatively influence marine mammal populations, to the extent that we can be certain that some species will not survive much longer. Although the introduction of international legislation protecting aspects of the marine environments (e.g. in the eastern North Atlantic and Europe: OSP AR Convention, HELCOM, ASCOBANS, and ACCOBAMS) is a welcome new trend, the lack of scientific information or the fundamentally different perspective that some governments take with regard to environmental policies still hamper the implementation of workable management and recovery plans for marine mammal populations. This applies particularly in the case of species that undergo long migrations or have extensive geographical ranges. To further compound the problem, there are jurisdictional and administrative obstacles at international and even national scales that, in practice, waste many conservation plans that otherwise appeared to be theoretically sound. But there are a few examples that illustrate the success of a strategy of protection and recovery. One such is the case of the North Pacific elephant seal (Mirounga angustirostris). Only a tiny rookery of around 100 individuals of this species remained on an island off the Californian coast at

5 Conservation and Management 461 the end of the nineteenth century; after a considerable conservation effort, its population size is now above 100,000 individuals, distributed along the Pacific coast of USA and Mexico. There is still room for hope. REFERENCES Clark, C.W. (1976) Mathematical Bioeconomics: The Optimal Management of Renewable Resources. Wiley Interscience, New York, NY. Cooke, 1.G. (1994) The management of whaling. Aquatic Mammals, 20, Evans, P.G.H. (1996) Human disturbance of cetaceans. In: The Exploitation of Mammals - principles and problems underlying their sustainable use. (Ed. by N. Dunstone & V. Taylor), pp Cambridge University Press. 415pp. Gambell, R. (1999). The International Whaling Commission and the contemporary whaling debate. In: Conservation and Management of Marine Mammals (Ed. by 1.R. Twiss Jr and R.R Reeves), pp Smithsonian Institution Press, Washington DC. 471 pp. Geraci, J.R. and St. Aubin, OJ. (Eds.) (1980) Sea Mammals and Oil: Confronting the Risks. Academic Press, San Diego, CA. IF A W, Tethys Research Institute, and Europe Conservation. (1996) Report of the Workshop on the Scientific Aspects of Managing Whale Watching. Montecastello de Vibio, Italy, Mar 30-Apr4, pp. Intergovernmental Panel on Climate Change. (200 I) Climate Change 2001: The Scientific Basis. Third Assessment Report of the IPCC Working Group I. Available from IPCC Secretariat, c/o World Meteorological Organization, 7bis Avenue de la Paix, c.p. 2300, CH-I211 Geneva. International Whaling Commission. (1994) Report of the Scientific Committee. Annex H: The Revised Management Procedure (RMP) for Baleen Whales. Report of the International Whaling Commission, 44, International Whaling Commission. (1997) Report of theiwc workshop on climate change and cetaceans. Report of the International Whaling Commission, 47, Reijnders, P.J.H., Aguilar, A. and Donovan, G.P. (Eds.) (1999) Chemical Pollutants and Cetaceans. The Journal afcetacean Research and Management (Special Issue 1), Richardson, W.J., Greene, C.R. Jr., Malme, C.1. and Thomson, D.H. (1995) Marine Mammals and Noise. Academic Press, San Diego. 576pp. O'Shea, TJ. (1999) Environmental contaminants and marine mammals. In: Biology of Marine Mammals (Ed. by le. Reynolds III and S.A. Rommel), pp Smithsonian Institution Press, Washington DC. 578pp. Reeves, RR. and Leatherwood, S. (1994) Dolphins, porpoises and whales. An Action plan for conservation of biological diversity: IUCN, Gland, Switzerland. 91 pp. Tormosov, D.D., Mikhaliev, Y.A., Best, P.B., Zemsky, V.A., Sekiguchi, K., and Brownell, R.L. Jr (1998) Soviet catches of southern right whales Eubalaena australis, Biological data and conservation implications. Biological Conservation, 86, Tynan, c.t. and Demaster, D.P. (1997) Observations and predictions of Arctic climatic change: potential effects on marine mammals. Arctic, 50, Urick, R.J. (1986) Ambient Noise in the Sea. Peninsula Publishing, Los Altos, CA. Wade, P.R (1998) Calculating limits to the allowable human-caused mortality of cetaceans and pinnipeds. Marine Mammal Science, 14,1-37.

6 462 Marine Mammals: Biology and Conservation Wiirsig, B. and Ortega-Ortiz, J. (1999) Global climate change and marine mammals. European Research on Cetaceans, 13, Yablokov, A.V. (1994) Validity of whaling data. Nature (London), 367, 108. Zemsky, V.A., Berzin, A.A., Mikhaliev, Y.A., and Tonnosov, D.O. (1995) Soviet Antarctic pelagic whaling after WWII: review of actual catch data. Report of the international Whaling Commission, 45,