Management refers to those regulations, laws, treaties,and policies that govern human interactions with marine mammals. Marine mammal management may promote a wide variety of human objectives: conservation of marine mammal populations for their intrinsic value, maintenance of marine mammal populations for human exploitation, protection of human health interests, humane treatment of captive animals, reduction of direct or competitive interference with commercial fisheries, and so on. This article concentrates on the general approaches used for marine mammal management.
I. Management Units
“Management unit” refers to the group of animals that is the target of some management action. It may refer to a colony, sub-population, population, or species. The term “stock” has traditionally been used instead of “management unit,” but this term has evolved to be synonymous with both “population” and “management unit,” so, to avoid confusion, “management unit” is preferred. The appropriate definition of a management unit depends on the management objective. Laws to prevent the extinction of a species might have a species or subspecies as a management unit; however, the likelihood of achieving this management objective may be increased by managing on the basis of populations. Laws may not always explicitly define management units, but the stated goals of that law may give some clues as to how the term should be interpreted. For example, if the goal is to maintain marine mammal populations as functional elements of their ecosystems (one of the goals of the U.S. Marine Mammal Protection Act, MMPA), management units might necessarily be smaller than the entire population to ensure than range contractions would not prevent the attainment of this goal (Taylor, 1997). Knowledge of population structure is critical to defining management units. Population structure has been studied using tagging, radio and satellite tracking, allozymes, DNA fingerprinting, DNA sequencing, photo-identification, morphometries, and chemical markers. Most of these methods are limited: they can only show that two samples differ and thus that population structure is present, but they cannot be used to demonstrate that population structure is absent. There is almost always some uncertainty in deciding how finely to divide management units, and one of the current challenges in marine mammal management is dealing with this uncertainty.
II. Methods of Marine Mammal Management
A. Traditions, Taboos, and Practices
Prior to modern times, management took the form of culturally enforced practices. Ancient Greeks, natives in the Amazon Basin, and many sea-going cultures held dolphins in especially high regard and had proscriptions against killing or eating dolphins. Monk seals (Monachus monachus) were considered by the early Greeks to have prophetic powers and to be protected by Po-seiden; however, the popular views toward this species included antipathy and hostility. The societies that did harvest whales and seals (including Inuit and Aleut cultures) often had elaborate rules that determined who could hunt these animals and when they could be hunted. It is not known whether traditions and taboos were important in conserving marine mammals, but there is no evidence of marine mammal extinctions caused by humans prior to that of the Steller’s sea cow (Hydrodamalis gigas) in the 1700s. Traditions based on superstitions have been increasingly ignored as human populations have increased (Johnson and Levigne, 1999).
B. Harvest Bans
The most common method of protecting marine mammals from overexploitation has been a complete ban on harvesting. Most often, this has been practiced after a catastrophic decline has already occurred. Gray whales (Eschrichtius robustus), northern elephant seals (Mirounga angustirostris), and Guadalupe fur seals (Arctocephalus townsendi) were protected by Mexico after their near extinction. A complete ban on whaling for gray whales and right whales (Eubalaena spp.) was instituted early in the history of international whale management. Australia, Mexico, New Zealand, South Africa, and the United States have banned the commercial harvest of all marine mammal species in their waters. The European Union members of ASCOBANS (Agreement on the Conservation of Small Cetaceans of the Baltic and North Seas) have agreed to ban the intentional harvest of all small cetaceans. Exceptions to harvest bans are commonly made for aboriginal or subsistence harvests and for incidental mortality pursuant to other commercial enterprises.
C. Age/Sex Limitations on Harvests
Age and/or sex limitations on harvest are commonly employed in the management of terrestrial species. The U.S. North Pacific Fur Seal Act of 1910 outlawed the harvest of northern fur seal (Callorhinus ursinus) females and pups. This, together with the provisions of the North Pacific Fur Seal Treaty of 1911. effectively reversed the marked declines of die populations that breed on islands in the Bering Sea. Because many marine mammals do not exhibit marked sexual dimorphism (as do fur seals), similar regulations are not practical for all species. The 1931 Convention for Regulation of Whaling and later regulations of the International Whaling Commission (IWC) prohibited the commercial harvest of dependent calves and their mothers. Because most whales have a 2- or 3-year reproductive cycle and are nursing for only 6-12 months, females were not protected for the majority oi time. Minimum size limits were also established for various whale species. These and other regulations were not effective in preventing the depletion of most of the world’s whale populations.
D. Seasonal Area Closures
The seasonal closure of certain areas or all areas is another common practice in wildlife management. The 1931 Convention for the Regulation of Whaling established a closed season for factory ships in Antarctic waters from April 7 to December 8. Seasonal area closures have also been used to reduce the number of gill net entanglements of Hector’s dolphins (Cephalorhynchus hcctori) in New Zealand and harbor porpoises (Phocoena phocoena) in the U.S. Gulf of Maine.
E. Restrictions on Methods and Fishing Gear
Regulations may limit the methods by which marine mammals are killed. The Fur Seal Treaty of 1911 eliminated the at-sea pelagic harvest of northern fur seals (Callorhinus ursinsus). which were commonly considered to be wasteful (many carcasses could not be recovered) and which were more difficult to monitor. Methodological restrictions are not limited to direct, intentional harvests. Many gear restrictions have been applied to reduce marine mammal bycatch in commercial fishing operations. Finer mesh panels (Medina panels) were added to tuna purse seine nets in the eastern tropical Pacific to reduce dolphin entanglement. The use of acoustic warning devices (pingers) is mandated to reduce cetacean bvcatch in several U.S. fisheries, and additional experiments with pingers are currently being conducted worldwide. Regulations may also address how a particular gear is used; the adoption of a “backdown” procedure greatly reduced the mortality of dolphins in tuna purse seines. In addressing marine mammal bycatch problems, restrictions sometimes take the form of a complete ban on a particular gear type. In 1989 the states and territories of the South Pacific-banned the use of large-scale (> 2.5 km), drift gill nets in their exclusive economic zones, and in 1992 the United Nations General Assembly extended this ban to all international waters. There have been several attempts to ban drift gill nets in the Mediterranean. In the United States, Florida, Louisiana, Texas, and California have banned gill nets in all or part of their waters in response to marine mammal and other bycatch issues.
F. Quota-Based Restrictions
The most direct method to manage removals from a wild population is to set a limit on the number of animals that can be taken in a given time period (usually 1 year). Quota-based management was first applied to the directed harvest of marine mammals and was later adapted to regulation of bycatch. This method requires some method for estimating annual mortality.
Such as from a mandatory program placing observers on whaling or fishing vessels. Whaling on the high seas has been regulated with quotas since 1931. but early quotas were designed only to limit oil production and were based on a “blue whale unit” [the oil equivalent of one blue whale (Balaenoptera musculus) being two fin whales (B. physalus), six sei whales (B. borealis). etc.]. The lack of species- or population-specific whale quotas lasted until 1972 and is widely blamed for the near extinction of most large whale populations. The failure of IWC to effectively manage whaling resulted in an international moratorium on commercial whaling that started in 1986 and continues today. Since 1986, the IWC has devised and adopted a revised management procedure that incorporates a new, well-tested catch limit algorithm (CLA) for setting population-specific quotas. Aboriginal subsistence whaling continues under population-specific quotas that are based on biological considerations and on “cultural and nutritional needs.” Quotas were first used in 1976 to limit bycatch in the U.S. tuna purse seine fishery to 78.000 dolphins per year. The U.S. quotas gradually decreased to 20.500 by 1981. but. like the blue whale unit, still had not adequately addressed species- and population-specific conservation concerns. The gradual conversion of the tuna purse seine fishery from a U.S. industry in 1970 to a largely international fleet by 1990 further complicated conservation efforts. The Inter-American Tropical Tuna Commission (and several nongovernmental organizations) have negotiated with its signatory nations to impose vessel-specific quotas on total dolphin bycatch (1993) and stock-specific quotas (2000). Although management of dolphin mortality in the tuna fishery has remained a special case, the United States has adopted a more general approach to setting stock-specific quotas on the maximum allowable levels (potential biological removal, PBR) of human-caused mortality for marine mammal populations in its exclusive economic zone. The PBR approach is like the IWC’s CLA in that it sets allowable removal rates that are conservative in the face of uncertainty but which can increase as uncertainties are resolved. New Zealand uses a similar approach to setting annual bycatch limits for Hooker’s sea lions (Phocarctos hookeri) and has closed its squid trawl fishery when this limit was exceeded. Several countries, including the United Kingdom, are investigating similar approaches to setting limits on fishery bycatch.
G. Market Monitoring and Trade Restrictions
Enforcement of laws on the high seas is often difficult or impossible; therefore, market monitoring and international trade restrictions may be necessary to prevent the illegal harvest and marketing of protected marine mammal. The Convention on International Trade in Endangered Species (CITES) is the primary implement for international trade restrictions and currently bans all trade in whale products, including some species that are not considered “endangered” but whose meat might be confused with that from endangered species. Genetic methods now can distinguish between all species, and CITES is under pressure from pro-whaling countries to lift the “look-alike” ban on nonendangered whales. Surreptitious market surveys by nongovernmental organizations and subsequent genetic analyses have shown that Japanese and Korean markets contain a wide variety of cetacean products, many of which are mislabeled and some of which may have been illegally imported (some cetaceans taken within EEZ waters of those countries and minke whales taken under “scientific whaling” can be legally marketed). Because marine mammal products can be extremely valuable, there will be a strong incentive to cheat. Some IWC member countries are insisting that a system of market monitoring precedes the resumption of commercial whaling, possibly by genetically “fingerprinting” every legally taken whale.
H. Treatment of Wild and Captive Animals
Marine mammals, especially cetaceans, are regarded by many cultures as deserving special treatment by humans. These attitudes may stem from their similarities to humans (large brain, play behavior, etc.), from their representation in popular media, or from the endangered status of some species. Whatever the reason, the special treatment is often evident in national laws that afford more protection for marine mammals than for similar terrestrial mammals. For example, the U.S. MMPA prohibits “harassment” of marine mammals (defined as any pursuit, torment, or annoyance that has the potential to disrupt the natural behavioral patterns of the animal) unless a specific permit is obtained. Virtually any research on marine mammals (except passive observation) has a potential for harassing the subject and therefore requires an MMPA permit. National laws are also frequently implemented to regulate the public display of marine mammals to ensure that adequate space and care are provided to those animals. Some laws and regulations are expressions of public concern for individual animals (rather than concern about species or populations) and are derived more from the animal rights movement than from a conservation ethic, but this distinction is not clear in many cases. Stranding programs that rehabilitate beached animals may aid individuals and, for endangered species, the survival of the species.
I. Marine Sanctuaries
There is a long-standing and growing interest in the use of protected areas or sanctuaries as a management tool for marine species. The first marine mammal refuge [for pinnipeds and sea otters (Enhydra lutris) on Afognak Island. Alaska] was established in 1892, but most have been established since 1975. Protected areas are a useful management tool because the concept is so simple (easy to understand and to enforce). For marine mammals, established sanctuaries and protected areas are taxonomically limited: the Indian Ocean and Southern Ocean whale sanctuaries (established by the IWC) protect only large whales, the Irish whale and dolphin sanctuary (established by Ireland) protects only cetaceans, and the Banks Peninsula sanctuary (established by New Zealand) was designed to protect only Hector’s dolphins. The level of protection varies between sanctuaries; the Irish whale and dolphin sanctuary does not prevent porpoise and dolphin bycatch in commercial fisheries (although the existence of the sanctuary has focused efforts on reducing bycatch). The utility of protected areas as a management tool depends critically on characteristics of the animals they are designed to protect (residency patterns, home ranges, mating strategies) and on the size of the protected area. The enormous Southern Ocean whale sanctuary (generally, all waters south of 40° S but excluding the Indian Ocean sanctuary) is currently recognized as being too small to effectively protect its whales (which migrate out of this area during the southern winter). In contrast, small protected areas are quite effective in sheltering breeding colonies of pinnipeds or essential warm spring habitats of manatees. To conservation biologists, a “marine protected area” refers to an area of complete protection at all ecosystem levels. Existing marine protected areas are too small to afford much protection for marine mammal species, although they may protect some critical habitat.
J. Pinniped Control Programs
The recovery of many pinniped populations from a legacy of hunting and near extermination is one of the success stories in marine mammal management, but this recovery is hardly viewed as a success by fishermen and aquaculturists who share their waters. Even conservationists are faced with a dilemma in some situations, such as when California sea lions (Zalophus californianus) (protected, but now numbering approximately 200,000) are threatening the survival of a depleted stealhead run in Washington State. Laws protecting marine mammals can and have been modified to deal with such small-scale problems by authorizing the lethal or captive removal of specific problem animals. In some areas, the use of acoustic harassment devices (AHDs) has been authorized to deal with the economic loss to seals by aquaculture facilities or commercial fishermen. Although some of these “fixes” appear to be successful in the short term, their long-term utility is questionable and there is concern about the impact of AHDs on other elements of the ecosystem. Even more controversial are programs designed to reduce entire pinniped populations by culling. Government-sanctioned culling programs to improve fisheries have been practiced in many countries, including Norway and the United States. In Canada, the high annual quota on harp seals (Pagophilus groenlandicus) and hooded seals (Cystophora cristata) is justified, in part, as a means to reduce seal predation on depleted cod stocks. This approach has been criticized on theoretical grounds because it oversimplifies ecosystem interactions; pinnipeds may feed on a commercially important fish species, but may also feed on predators of that species. Management of culling programs would typically fall under national regulations, but the IUCN Marine Mammal Action Plan has established a protocol to evaluate culling proposals.
K. Ecosystem Management
Ecosystem management refers to approaches ranging from simply considering the impact of a management decision on other elements of the ecosystem to the simultaneous optimization of management strategies to meet management goals of all elements of an ecosystem. There are no examples of the latter approach, although Norway and the signatory nations of the Convention for the Conservation of Antarctic Marine Living Resources are pursuing this goal by promoting multispecies considerations in the management of marine mammal, fish, and seabird resources. Although it is unarguably true that improvements can be made in resource management by considering ecosystem interactions, it is also true that predicting the implications of even a simple ecosystem perturbation is far beyond our current capabilities. Significant progress in implementing ecosystem management may be left to future generations.
III. Trends in Marine Mammal Management
In recent years, there has been a movement toward management procedures that detennine quotas for allowable harvests or incidental mortality based on rigid formulae. Both the IWC’s CLA and the U.S. PBR approaches are based on formulae that estimate the allowable removals from a management unit based on measurable attributes (such as estimated population size, population growth rates, catch histories, and the precision of the various estimates that are used). The advantage is that all parties can reach a priori agreement on the management objectives and on the rules that will be used to reach those objectives without divisive arguments about the effect on anyone’s quota. Biological data are inherently imprecise and full of other uncertainties. For both CLA and PBR approaches, computer simulation studies were used to “tune” the quota formulae to achieve their goals even in the presence of imprecision and bias in available data (Wade, 1998). With the increasing emphasis on rigid quota-based management, debates about management practices are changing. Instead of concentrating on which values of biological parameters and which analytical models should be used, managers are now more concerned with how management units should be defined.
Coincident with the movement toward rigid formula-based quota schemes is an increasing reliance on direct approaches to measuring population parameters and a decreasing reliance on industry statistics, such as catch per unit effort. Advances in survey methodology (line-transect and mark-recapture) have greatly improved our ability to estimate the size of cetacean populations. Photo-identification studies, combined with mark-recapture analysis, have refined our understanding of marine mammal life history. Observer programs have increased the reliability of bycatch and harvest estimates. Satellite tagging and the recent revolution in molecular biology have contributed to an explosion of new information on the structure of marine mammal populations. Although all these recent trends promote the potential for effective marine mammal management, the real impediment to effective management is now the lack of collective willpower to implement regulations and to enforce existing regulations.
There has been increasing interests in applying the “precautionary principle” in marine mammal management. In the face of uncertainty, management decisions should be made to minimize the damage caused by being wrong. In most resource protection issues, there are two types of damage: the damage caused to a regulated industry by providing more marine mammal protection than is needed and the damage done to the populations and the industry by providing too little protection. A look at the catastrophic history of marine mammal management illustrates the disastrous economic and ecological results of management approaches that are not precautionary. One way to add precaution is to reverse the legal burden of proof to ensure that any action will not adversely affect the population before that action is permitted. Clearly, the future challenge is how to make marine mammal management appropriately precautionary.
