Marine Living Resources

Whilst the Antarctic terrestrial ecosystem has an extremely low productivity with a total production of plant material measured in the hundreds of tonnes per year, the Southern Ocean south of the Antarctic Convergence has a very much higher productivity with a total plant (phytoplankton) production measured in thousands of millions of tonnes per year. However, the overall productivity of the Southern Ocean is not as high as previously believed (El-Sayed and Turner, 1977; Holm-Hansen et al., 1977; Knox, 1983; Clarke, 1985; Hempel, 1985; Laws, 1985b; Nelson and Smith, 1986; Wilson et al., 1986) which has implications to the exploitation of living resources from the region (El-Sayed, 1978). It is thought that the large seasonal variations in light and sea-ice cover, and especially the near-freezing temperatures of the surface waters, may be more significant in controlling the productivity of the Southern Ocean waters than upwelling and the regeneration of nutrients (Knox, 1983). Nonetheless, Knox (1983) has pointed out that, although the Southern Ocean constitutes only 10% of the world's oceans, it has potential resources, principally krill, that could rival the production of the other 90% (cf. Walton, 1987). This makes krill potentially the world's largest fishery stock (Auburn, 1982).

The principal characteristic of the Southern Ocean is the shortness of the food web. The principal herbivore is krill (Euphausia superba) which has a biomass of the order of 109 tonnes. The consumers of krill include squid, fish, seabirds, crabeater seals and baleen whales. At the top of the food web are the higher predatory species including toothed whales, fish, penguins and Weddell and leopard seals. The shortness of the food web enables a greater proportion of the overall productivity to reach the higher trophic levels and this accounts for the unusually dense populations of birds and mammals. Fish are not as important as elsewhere, in part because the continental shelves are much deeper and narrower (Laws, 1983). Attempts to calculate the consumption of the major food components by whales, seals and birds have been made by Everson (1977) (cf. Laws, 1985b). However, simple food webs such as found in the Southern Ocean are thought to be ecologically unstable. They exhibit large population oscillations and are vulnerable to significant perturbations.

Because of exploitation, the biomass of whales in the Southern Ocean has declined from about 43 million tonnes originally to about 7 million tonnes today (i.e., a 6-fold decrease). The original whale stocks are estimated to have consumed about 190 million tonnes of krill annually compared to about 43 million tonnes annually today. About 150 million tonnes of krill are therefore thought to be available to other producers (Everson, 1977; Laws, 1977,1983,1985a, b; Lovering and Prescott, 1979; Knox, 1983, 1984; Nagata, 1983; Chittleborough, 1984; Walton, 1987). However, the dynamics of the system are still not well understood and it is not possible to say what effect harvesting the "krill surplus" would have, although populations of seals, seabirds, squid, and those populations of baleen whales that have not been exploited may have increased as a result (Knox, 1984).

The early years of Antarctic exploration were characterized by uncontrolled exploitation of marine life, particularly seals and whales. The Antarctic Treaty nations have adopted a number of conservation measures. The Agreed Measures for the Conservation of Antarctic Flora and Fauna (1964) restrict human activities near bird and seal colonies and set aside "sites of special scientific interest". The Convention for the Conservation of Antarctic Seals (1978) established regulations in advance of renewed exploitation. It applies south of 60°S. Ross, elephant, and fur seals are totally protected whilst quotas are set for crabeater, leopard and Weddell seals. At present, there is no commercial exploitation of seals in the Southern Ocean. Whaling is regulated by the International Whaling Commission (1946). The Commission has tended to set catch limits well above natural replacement levels. As the larger whales were hunted to the point of extinction, attention turned to the smaller whales. At present, the U.S.S.R. and Japan are the only IWC countries still hunting whales in the Southern Ocean and the minke whale is the only species abundant enough to catch.

To give some idea of the extent of exploitation of biological resources from the Antarctic Sector of the Pacific, for the statistical area south of 60°S the total krill catch for the 10-year period (1977-86) was 38,707 tonnes of which 49% was taken by the U.S.S.R. and 51 % by Japan. This total represents only 1.3% of the total catch from the entire Southern Ocean, a reflection of the lower commercial krill catch rates in this region compared to those in the South Atlantic (Everson, 1977). Total fish catch for this period was reported to be 2,357 tonnes of which the U.S.S.R. took over 99%. This represents a negligible proportion of the total fish catch for the Southern Ocean, reflecting in part the absence of any shallow areas in the region comparable to the Kerguelen Plateau or around South Georgia. These data are taken from SC-CAMLR-V (1985) (cf. Everson, 1977,1984a; Brewster, 1982; Knox, 1983; Kaczynski, 1984; Clarke, 1985; Kock, 1985,1987; Anonymous, 1986c; Bardach, 1986; Walton, 1987). The fish catch data do not, of course, include catches from the New Zealand Plateau where southern blue whiting is caught (Brewster, 1982). From 1891 to 1919, approximately 150,000 king and royal penguins were boiled down annually for oil on Macquarie Island (Falla, 1962; Brewster, 1982; Sage, 1985). Seal and whale catch data are given by Baker (this volume).

Much attention has focused on krill as a source of protein in recent years (Mitchell and Sandbrook, 1980; Kaylor and Lear son, 1983). Since krill is the basis for marine life in the Southern Ocean (Everson, 1977; Clarke, 1985; Laws, 1985a, b), harvesting krill has enormous implications for all other species.

The Convention for the Conservation of Antarctic Marine Living Resources (CCAMLR) (1982) applied to the area south of the Antarctic Convergence and adopts the "ecosystem approach" in which harvesting of target species is related to the impact on other species (Edwards and Heap, 1981; Nagata, 1983; Powell, 1983; Knox, 1984; Gulland, 1986). The Convention is particularly concerned with the conservation of fish and krill. Nonetheless, to manage living resources by the "ecosystem approach" requires knowledge of the resources, their distribution and behaviour in space and time, their role in the total ecosystem, and their response to fishery and proposed management options.

The BIOMASS (Biological Investigations of Marine Antarctic Systems and Stocks) programme has as its objective the deeper understanding of the structure and dynamic functioning of the Antarctic marine ecosystem as a basis for the management of actual and potential living resources (Knox, 1984; Hempel, 1987; Sahrhage, 1988). The original intention was that the BIOMASS programme would be a 10-year programme commencing in 1977 in which two major data gathering exercises (FIBEX, 1980-81, and SIBEX, 1983-84 and 1984-85) were undertaken; these represent one of the largest international programmes in marine biology. The BIOMASS programme involves building an information base which includes (Knox, 1984) :

1. the numerical and functional relationships among key species, particularly the relationships between krill and its predators and competitors;

2. the nature, dynamics and functioning of krill swarms and how they might be affected by harvesting and related activities;

3. the number and distribution limits of independent populations comprising the key species, especially krill;

4. the area and habitats critical for the spawning, survival and productivity of krill and other species; and

5. the major physical/chemical features (e.g., currents, fronts, gyres, upwell-ings, nutrients) that directly or indirectly determine the distribution, movements, abundance, life history, and productivity of the key species and populations, especially krill.

In spite of its ambitious nature, environmentalists have criticized CCAMLR on the grounds that progress in attaining the objectives of the Convention has been extremely slow and that almost all the major fish stocks have been seriously depleted during the last few years. Barnes (1982) considered that the Convention contains serious flaws from the standpoint of sound decision making. In particular, CCAMLR is thought to be hampered by :

1. the refusal of some fishing nations, particularly the Soviet Union, to provide adequate catch and effort statistics;

2. the objective of using the ecosystem approach to the management of krill and fish has enormous data requirements that are impossible to meet given the current level of funding; and

3. the requirement that decisions of the Commission on matters of substance are taken by consensus.

These circumstances have led to the situation where fishing is not regulated unless there is irrefutable evidence that the fish stocks are being depleted.

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