As Senior Science Advisor to the Governor of Alaska, one of my responsibilities is to acquire from the various state agencies a list of research needs, and to identify who within the universities and industries can resolve those needs. Another task is to interact with the recently established federal Arctic Commission, which is the vehicle for national and international scientific cooperation. The Arctic Research Policy Act, passed by President Reagan in 1984, has made the National Science Foundation the lead agency for coordinating arctic studies within Alaska—the only arctic state in the Union.

The newly appointed Commissioners and I had the opportunity to discuss with many citizens their concerns and hopes for the state, beyond just resource development and defense. Specifically, because of the accelerating pace and scale of developmental activities in the Arctic, concern has been expressed by Alaskans, especially native groups, about the impact these activities will have on the health of all residents in the Arctic. The current status of conducting and supporting arctic health research is inadequate. There are no medical or health research units in existence which can adequately assess problems related to occupation safety and health, or long-term environmental health consequences of life in the Arctic.

As indicated by the funding of this conference, the Alaska state government had concerns with air pollution which does not originate in the Arctic. As a result of data presented at this symposium, we see there is minimal danger to the Arctic from air pollution.

ABSTRACT. Movements of air masses over several thousand kilometres affect the quality of arctic air in both summer and winter. This paper summarizes the results of a programme by the Norwegian Institute for Air Research (NILU) to identify and characterize sources of pollutants measured in the Norwegian Arctic, and to model the movement of pollutants within the air masses. Aircraft-based data on scattering coefficient, particle size distribution and chemical composition of aerosols were used to trace the origins of polluted layers of arctic air. Polluted air masses were observed at altitudes above 2,000 m in summer and 2,500 m in winter. Polluted layers below 1,500 m were related to episodic movements of air masses from areas where temperatures were similar to those of the Arctic, for example the northern Soviet Union: these layers also gave chemical indications of their origins. Profiles derived from airborne data were extended downward by measurements from the ground. From information on (1) total and size-differentiated chemical composition of surface aerosol, (2) enrichment factors of chemical constituents, (3) emission inventories for potential sources of air pollution in the Norwegian Arctic, and (4) wind trajectories at 850 mb, we conclude that emissions from anthropogenic sources mainly in Eurasia, and occasionally in North America, contribute to the pollution of arctic air over the whole year. Good agreement between these measurements and estimates from Lagrangian transport model estimates supports this conclusion.

ABSTRACT. There is clear evidence that an atmospheric transport of pollutants to the Arctic takes place from the industrialized areas of surrounding continents, particularly in late winter when the anthropogenic component may rise to levels ten times higher than in summer and SO4 concentrations are between 1.5 and 4.0 μg/m3. In Alaska pH in snow has changed from 5.5 to 4.9 in the last 20 years. The basic meteorological cause for high levels of local and long-range pollutants in the Arctic in late winter is the lack of solar radiation, which contributes to high stability of air. Emission inventories, statistical analyses of trace elements and trajectory model calculations indicate that most winter aerosol at levels below 2 km originates in Europe and western and central Asia. The origin of pollution at higher levels is still unknown. Proposals for further monitoring and research are presented.

Studies of ice cores have indicated a marked increase in air pollution levels in this century, particularly since the mid–1950s.

The radiation balance over the Arctic could be significantly modified by aerosols like graphitic carbon particles which are common in arctic air pollution. Aerosols increase absorption of solar energy in the atmosphere and decrease absorption on the ground. In March they cause a mean atmospheric heating rate of the order of 0.20 K day−1 at latitudes 70° to 75°N. Proposals are presented for monitoring and research to determine more precisely the impact of changes in the radiation balance on regional climate in the Arctic.

The Alaskan native people have gone through a great deal of change within the last two generations. Their remote location in the Arctic no longer isolates them from the modern world. Natural resources of the Bush—fish and other forms of wildlife, locatable and leasable minerals, and tourists attracted to the Bush way of life (called ‘subsistence’)—have all brought change to the way that people live, and the air, lands and waters they live with and depend on.

The majority of Alaskan native people still live a hunting-gathering way of life. They do not sit in office buildings. They do not wear coats and ties. They do not work eight hours a day. However, the modern world of the Alaskan native does include labour for cash. Our villages are no longer self-sufficient. Framed houses have replaced the sod houses built with drift wood. Our villages now require imported energy for space heating and electricity production. We watch television from New York, and see new movies from Hollywood right in our homes.

Zimbabwe in south central Africa is now very important to us. Why would Bush Alaskan natives care about that place? Zimbabwe produces cobalt. We need cobalt to produce hard alloys for our snow machines and outboard engines, to get us to remote locations to harvest the food we eat.

Even with all these modern luxuries, we still need wildlife resources. The harvest of wildlife is the key to our culture and to the maintenance of our health.

Tropical communities of both plants and animals are characteristically diverse, with large numbers of species and very complex interrelationships compared with those in temperate zone communities. Fish faunas obey this general ecological rule, within both families and environments.

Fishes are the most ancient and numerous of vertebrates. Over 20 000 species are known, the majority of which live in the warm waters of the world. About 8000 species (40%) live on the continental shelves of warm seas in water less than 200 m deep, compared with only about 1130 species (5%) in similar habitats in cold seas. Freshwaters carry a surprisingly high total, about 8500 species (over 40%), the majority in the vast river systems and lakes of the tropics (Cohen, 1970). The Amazon system has over 1300 species, the Zaire (Congo) in Africa nearly 700, compared with but 250 species in the Mississippi system in North America and 192 in the whole of Europe. Each of the Great Lakes Victoria, Tanganyika and Malawi in eastern Africa has over 200 species, most of them endemic, i.e. found only in the particular lake. Of the 445 families offish, the seven largest (which include ca 30% of the total) – Cyprinidae, Gobiidae, Characidae, Cichlidae, Labridae, Loricariidae and Serranidae – are all well represented in tropical waters (Nelson, 1984).

Coral reef environments

Coral reefs harbour the most colourful and diverse of any fish communities, with the most complex relationships between species. The clear shallow warm waters provide natural aquaria, ideal conditions for direct observations of fish behaviour. The most important families of reef fishes are indicated in Table 8.1. Some species are not obligate reef fishes, but have a much wider distribution in association with hard substrates, and some reef fishes are particularly associated with marginal habitats, such as sand patches, lagoons, mangroves, or eel–grass beds (studied by Weinstein & Heck, 1979).

Coral reefs are of three main types: (1) barrier reefs along continents, most extensive along their eastern coasts; (2) fringing reefs, around islands; and (3) atolls, broken rings of reefs and islands around a central lagoon. The Indo–Pacific is particularly rich in corals and reefs, especially in the Indo–Australian archipelago, Malaysia, Sri Lanka, Madagascar, and around Indian Ocean and western Pacific islands. The Australian Great Barrier Reef is an intermittent series of reefs and cays stretching over 1900 km along the coast of Queensland north to New Guinea. Other major coastal reefs lie off the coast of East Africa and in the Red Sea. In the western Atlantic, reefs and cays extend 200 km southward from Yucatan in Central America, and many Caribbean islands are fringed with coral reefs.

This book, like its predecessor Fish Communities in Tropical Freshwaters (Lowe–McConnell, 1975), is based on field studies over a long series of years in many parts of the tropics, born of the delight of watching fishes in their natural environments. In such a book it is not possible to describe all the warmth and the colour, the sounds and the smells, the bird calls along the rivers, the glancing light – the many facets that make up the environmental whole. Yet often it is just the glancing light that gives a fish away, a ripple on the water surface, a shadow on the stream floor, leading predator to prey, woven into the complex pattern.

Why study tropical fish communities? Apart from the sheer pleasure of watching the behaviour of colourful fishes in clear warm waters of coral seas and freshwaters which provide natural aquaria, fishes are very important sources of protein in the diets of indigenous peoples throughout the tropics. Human populations are increasing at such an alarming rate that there is great pressure to develop fishery resources. It is vitally important that fish stocks should not be damaged by overexploitation and to avoid this we need to understand the biology of the fishes and factors governing fish production.

Far Eastern freshwaters considered here include those of tropical Asia (Oriental Region) and of Australia/New Guinea. The Asian tropics comprise the subcontinent of India, mainland Southeast Asia, and the islands lying on the continental (Sunda) shelf, Borneo, Sumatra, Java and certain others, which were connected with the mainland at intervals when the sea level was lowered during the Pleistocene glaciations. An extinct river system flowed into the sea between the present coastlines of Borneo and the Asian mainland. The rivers of eastern Sumatra and western Borneo, and even some from India, Thailand and Indochina, were tributaries of this vast system, which accounts for many similarities in fish fauna between the islands and mainland. North Borneo rivers did not join this system, and the fauna here is somewhat impoverished. Islands lying off the Sunda shelf have completely different freshwater faunas.

Wallace's Line down the Makassa Straits between Borneo and Sulawesi (Celebes) is the world's most spectacular zoogeographical boundary affecting freshwater faunas. To the west, Borneo teems with 300+ species of primary freshwater fishes (17 families); only 140 km to the east, Sulawesi has but two primary freshwater fish species, Anabas testudineus and Channa striatus, both probably introduced by man. Sulawesi, like Borneo, does have a few secondary freshwater fishes (cyprinodonts, a synbranchid and vicarious atherinids).

Factors affecting demersal fishes

Information on the ecology of demersal fishes comes mainly from two sources: (1) line fishing over hard substrates, old dead coral, rock or other rough ground; and (2) trawl fishing on the continental shelves where the shelf is wide and there are suitable deposits of sand or firm mud. Some Neritic pelagic fishes may also be taken in the trawls, particularly fish which have the habit of forming demersal schools, as do carangid jacks and scads (Caranx, Trachurus), and some clupeids such as Sardinella which congregate near bottom depressions by day moving up to feed by night. Many of the rough–ground fishes caught by lines may also rest some way above the bottom but feed on the bottom, often by night.

Shelf faunas are greatly affected by the width of the shelf and nature of bottom deposits, by oceanographical conditions (salinity, clarity of water, temperature, water movements and so on), and by the history of the oceans and possibilities of colonization from neighbouring areas. The continental shelf may be over 100 km wide, sloping gradually to about 100 m deep before it falls away steeply into deep water (as off Guyana). The type of bottom is of prime importance in controlling the distribution of demersal fishes. Soft mud, sand, hard rock and coral, each has a characteristic community of fishes and of invertebrates so important as fish food.

Trophic interrelationships and community structure

Although food webs in tropical waters are often very complex, they may be based on relatively few sources, for example the aufwuchs which supports numerous species on the rocky shores of Lake Malawi (Fig. 4.2), or the benthic algal flora that supports herbivorous fishes on marine reefs. In any food chain there are rarely more than four or five links; long chains are energetically expensive as a large proportion of the potential energy is lost at each successive stage. In freshwaters alternate chains run: (1) from bottom detritus, through microorganisms, to detritus–feeding invertebrates or fish, to several levels of piscivore; or (2) in the pelagic zone from phytoplankton to zooplankton, to zooplanktonfeeders, then to one or more levels of piscivore. In river systems the detrital chain is more important, based largely on allochthonous materials in the headwater streams while in lower reaches detritus comes mainly from decomposition of aquatic macrophytes (see the ‘river continuum concept’ of Vannote et al., 1980; but see also Rzoska, 1978). As a lake forms, the pelagic plankton chain becomes increasingly important, as seen after the filling of man–made lakes, and also in lakes such as Chad, populated with riverine fishes such as Alestes baremose which changed its riverine diet of insects and seeds to exploit zooplankton in the lake.