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FIGURE 10.9 The parabola represents the logistic model of population growth [Eq. (9.1), Fig. 9.5] with the maximum sustainable yield (MSY) at 50% of a population's carrying capacity. In fisheries, the MSY is estimated to occur when net recruitment and fishing mortality rates are in equilibrium [Eq. (10.1)]. If the fishing impacts exceed the MSY and approach the population's carrying capacity, the population will be overharvested. Differences between the value and cost of the fishery, which reflect the return on investment (i.e., profit), are greatest at fishing effort levels (segment AB) that generate less than the maximum yield (segment CD).

Fishing Effort

FIGURE 10.9 The parabola represents the logistic model of population growth [Eq. (9.1), Fig. 9.5] with the maximum sustainable yield (MSY) at 50% of a population's carrying capacity. In fisheries, the MSY is estimated to occur when net recruitment and fishing mortality rates are in equilibrium [Eq. (10.1)]. If the fishing impacts exceed the MSY and approach the population's carrying capacity, the population will be overharvested. Differences between the value and cost of the fishery, which reflect the return on investment (i.e., profit), are greatest at fishing effort levels (segment AB) that generate less than the maximum yield (segment CD).

just the blubber oil. These licenses, along with various leases, laws, regulations, conventions, and decrees, had the additional advantage of providing legal justifications for nations to assert their sovereignty over Antarctica (Fig. 3.5).

Even when resource management strategies reached international levels, as represented by the 1946 International Convention on the Regulation of Whaling, they still were structured with a view toward economic gain. This economic focus is classically reflected by the ''blue whale unit'' that was subsequently established: one blue whale was equated with two fin, two-and-a-half humpback, and six sei whales. As a result, with whalers free to pursue all whale species, capturing blue whales was encouraged because less cost-per-unit-of-effort was involved in achieving one ''blue whale unit''—ultimately resulting in the greatest decimation among the blue whales (Fig. 10.3). Moreover, the very language of the convention is built on regulation (which highlights commercial dynamics) rather than conservation (which highlights species or ecosystem dynamics).

What is conservation, and how is it related to ecosystem management?

When the Antarctic Treaty came into force in 1961, the marriage of policy with scientific and technical advice progressively expanded the focus on ecosystem conservation (Table 5.2; Antarctic Treaty Searchable Database: 1959-1999 CD-ROM). The first substantive conservation steps came with the Agreed Measures for the Conservation of Antarctic Fauna and Flora (Agreed Measures), which was annexed to Recommendation III-VIII from the Third Antarctic Treaty Consultative Meeting in 1964.

Beyond recognizing that ''unique nature'' of Antarctica fauna and flora, the Agreed Measures began integrating ''protection, scientific study and rational use'' within species' circumpolar ranges. The Agreed Measures, which only applied to the Antarctic Treaty area south of 60° South latitude, prohibited the introduction of ''species of animal or plant not indigenous to that Area.'' The Agreed Measures also began a permit system for Specially Protected Species (such as the fur and Ross seals) and Specially Protected Areas because of their extreme ''defenseless-ness and susceptibility'' to human impacts. Importantly, the concept of ''flora and fauna'' went beyond individual species to the heart of the general trophic interactions that affect the dynamics of ecosystems (Chapter 9: Living Planet).

After adopting the Agreed Measures, the Antarctic Treaty nations implemented several recommendations regarding the vulnerability of Antarctic seals to commercial exploitation and the need for international conservation measures. These recommendations included a strategy for determining the maximum yields that could be sustainably harvested from various seal populations.

Following previous seal management efforts, with advice from the Scientific Committee on Antarctic Research (SCAR), the Antarctic Treaty nations signed the Convention on the Conservation of Antarctic Seals (CCAS) in 1972. CCAS expanded the permit system of the Agreed Measures and adopted a broad suite of conservation measures (Box 10.1). These conservation measures were designed to provide basic information on the density, size and gender distributions of seal populations over space and time with much more detail than had been involved in the earlier management of the elephant seals (as noted above). In addition, CCAS designed management strategies based on applied information about the gear, effort, and catch statistics of the fisheries. In general, these basic and applied data are essential for interpreting both natural variations and human impacts among harvested species (Fig. IV).

Concurrently, because of the potential value of krill as a global food source for humankind, SCAR established a subcommittee of its Biology Working Group in 1972 to broadly consider the marine living resources of the Southern Ocean. Four years later, SCAR started a 15-year coordinated international research program for the Biological Investigations of Marine Antarctic Systems and Stocks (BIOMASS). The primary objective of BIOMASS was to:

. .. gain a deeper understanding of the structure and dynamic functioning of the Antarctic marine ecosystem as a basis for the future management of potential living resources.

In the 1980-81 austral summer, the First BIOMASS Experiment (FIBEX) was carried out to investigate the physical, chemical, and biological characteristics of box 10.1 1972 convention on the conservation of antarctic seals a

ARTICLE 3.1: ANNEXED MEASURES

. . . Measures with respect to the conservation, scientific study and rational and humane use of seal resources, prescribing inter alia:

a. permissible catch;

b. protected and unprotected species;

c. open and closed seasons;

d. open and closed areas, including the designation of reserves;

e. the designation of species areas where there shall be no disturbance of seals;

f. limits relating to sex, size, or age for each species;

g. restriction relation to time of day and duration, limitations of effort and methods of sealing;

h. types and specification of gear and apparatus and appliances which may be used;

i. catch return and other statistical and biological records;

j. procedures for facilitating the review and assessment of scientific information;

k. other regulatory measures including an effective system of inspection.

aFrom the Antarctic Treaty Searchable Database: 1959-1999 CD-ROM.

the Antarctic marine ecosystem (Fig. 10.10). These investigations were followed by two phases of the Second BIOMASS Experiment (SIBEX I and II) in 198384 and 1984-85.

Given the potential impacts of krill harvesting on the dependent species in the pelagic food web (Fig. 9.2) and the need for coordinated international management of Antarctic marine resources, the Antarctic Treaty System signed the Convention on the Conservation of Antarctic Marine Living Resources (CCAMLR) in 1980. CCAMLR followed from the scientific accomplishments of the BIOMASS program in the same way that the Antarctic Treaty succeeded the International Geophysical Year. In addition, the parallel structure of the Antarctic Treaty and SCAR was extended to CCAMLR in the ''legal personality'' of a Commission and a Scientific Committee.

Unlike the CCAS, which was associated with seal conservation only, CCAMLR was designed to protect ''fin fish, molluscs, crustaceans, and all other species of living organisms, including birds'' in the Antarctic marine ecosystem. CCAMLR focused on the ''complex of relationships of Antarctic marine living resources

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