INTRODUCTION TO FISH TOXICANTS: DEVELOPMENT OF SELECTIVE PISCICIDES

Fish toxicants are widely used to eradicate some or all of the fish in a body of water in order that desirable fish may be stocked, free from predation, from competition or from other interference from undesirable fish. Fish poisons have a long history of use in many countries but it is only in the last 40 years that the subject has really been scientifically investigated, and only within the last 20 that the full environmental or ecological effect of such toxic chemicals has been examined critically, particularly in the US and in Canada. Fish toxicants have been used in all types of water body, both static and running. Earlier progress in their study has been exhaustively reviewed (Lennon et al., 1971), and information available at that time regarding the reactions of freshwater fauna in general, including fish, to those fish toxicants was also the subject of a separate review at that time (Muirhead-Thomson, 1971). In the present review, space limitations would now make it extremely difficult to do justice to the mass of new information covering all freshwater fauna and all types of water body. Accordingly, in keeping with the scope of the coverage, progress since that time will deal only with the use of fish toxicants in running water, and only with the macroinvertebrate fauna at risk.

INTRODUCTION

For many years, control of tsetse fly in Africa was carried out by a variety of methods based on environmental manipulation, such as bush clearing, game exclusion, habitat destruction by burning etc. The choice of methods was mainly determined by the nature of the habitats characteristic of different species of tsetse, and also by whether the objective of these operations was tsetse control or tsetse eradication.

With the advent of the synthetic insecticide DDT and its allies, increasing emphasis has been on the application of insecticide to the tsetse environment either by means of heavy residual dosages to tsetse-resting sites, or by repeated non-residual applications at lower dosage rates (Jordan, 1974). Initially the insecticides of choice were DDT and dieldrin, the latter being favoured because of its higher toxicity to tsetse. However, it was recognised early that such tsetse control measures had a serious immediate effect on wildlife, mammals, birds, reptiles and fish (Graham, 1964). Over the last 20 years therefore, the preferred insecticide for tsetse control has been the allied organochlorine chemical, endosulphan (Thiodan) (Goebel et al., 1982) selected because of its high lethal effect on tsetse combined with less inimical effect on wildlife (Hocking et al., 1966; Park et al., 1972). That period has also been marked by operational changes; insecticides originally applied by means of ground spraying or fogging equipment, are now applied almost entirely from the air, both by fixed-wing planes and by helicopter.

From the very wide range of activities dealt with in this review, dealing with a great variety of problems in many countries, it is clear that the period under review has been one marked by a great upsurge of interest, and by remarkable progress in a hitherto much-neglected aspect of running water contamination. In fact this period of intense interest in the special problems of the macroinvertebrate fauna (as distinct from those of freshwater fish) of streams and rivers, may indeed encompass a peak period of study which is perhaps already on the decline. This is perhaps inevitable. Problems of particular interest or importance, or ones for which unusually ample funds are available for research, attract and encourage the most competent researchers, whose interest and scientific dedication in turn engenders further enthusiasm (Brown, 1973). This leads to the build up of multidisciplinary teams capable of making massive contributions to knowledge during their tenure.

This has certainly been the case with some of the major projects examined in detail in this review. For example, the OCP (Onchocerciasis Control Programme) inaugurated in 1974 on a 20-year basis has produced team work of the highest productivity during its first 10 years. Key research workers tend to move to other fields, or to retire; the teams become disbanded and funds for research tend to dwindle. It is difficult to visualise that the same intense research effort on the impact of Simulium control measures on non-target macroinvertebrates, and on stream ecosystems, will continue at the same high pitch for the next 10 years of the programme.

TOLERANCE LEVELS UNDER STANDARD CONDITIONS

REACTIONS IN STATIC TESTS

With the widespread use of DDT and allied chlorinated hydrocarbon insecticides for pest control in the 1950s and 1960s it became increasingly clear that stream invertebrates were highly vulnerable to these chemicals. This destructive effect was particularly evident when stream and river habitats were unavoidably contaminated by repeated aerial applications of insecticides against forest pests such as the American spruce budworm. Experiences with mass destruction of river fauna in one of these campaigns in the Yellowstone National Park in the US, stimulated the need for more precise information about the susceptibility of stream invertebrates to the different insecticides then in use. This resulted in perhaps the first serious development of a laboratory evaluation programme for stream invertebrates in general as distinct from such target fauna as Simulium larvae (Gaufin, Jensen & Nelson, 1961; Jensen & Gaufin, 1964, 1966; Gaufin et al., 1965). That and the other contemporary work has already been reviewed in depth (Muirhead-Thomson, 1971), but there are still aspects of those studies which are of particular significance in the light of developments in the 20–25 years since that period. First of all, two aquatic invertebrates which played a prominent part in those laboratory tests, namely the stonefly (Plecoptera) nymphs of Pteronarcys californica and Acroneuria pacifica, were typical of clean unpolluted running water and were also important food organisms of trout. Second, both species were robust creatures, easy to obtain and to maintain in a healthy condition in the laboratory.

INTRODUCTION

In Chapter 1 it was pointed out that many of the striking advances in knowledge over the last 10–15 years regarding pesticide impact have been the outcome of field studies in practical pest control programmes. In all these projects, the environmental studies relate to the known chemical and formulation which is either applied directly to the stream at a predetermined application rate calculated to produce the desired concentration of the chemical in the water, or which contaminates the stream indirectly as a result of aerial application of pesticide to control terrestrial pests in the environs of the stream or river, and where the dosage rate in terms of kilograms per hectare has again been predetermined. In both instances the actual time of application is also known precisely.

The object of these environmental studies is to find out the extent to which the pesticide treatment produces significant changes in the composition of stream fauna produced by mortality or downstream movement, with particular reference to the macroinvertebrates which are the subject of this review. In order to measure these effects and to ascertain significant population changes among the different organisms of running water community – both in the short term and the long term – pesticide ecologists have to rely on a variety of sampling methods. It is these various capture or trapping techniques which provide the essential data for measuring changes in population density or in population composition attributable to pesticide impact.

ARTIFICIAL STREAM COMMUNITIES

The laboratory streams described so far have been designed mainly for single species at a time, or for limited select groups of macroinvertebrates. The logical progress from this point is to design simulated streams in which impact of toxic chemical on a whole community can be studied under conditions akin to those in the natural habitat, but allowing certain factors to be controlled and studied separately in a way that is not feasible in the stream complex. Noteworthy developments along these lines have indeed been made, though not necessarily with the same objective. For example, in studies on the community effect of the lamprey larvicide TFM (see page 214) in Michigan, six fish hatchery channels 8 m long and 0.6 m wide were used, allowing three complete systems, each comprising one control and one adjacent experimental channel (Maki & Johnson, 1977). Each channel was divided into a 4 m upper pool section and a 4 m lower riffle section. The upper pool section was allowed to become colonised by introduction of organic matter and by drift of fauna in the gravity-fed water supply from an adjacent creek. The riffle section was also colonised from natural stream substrates, with associated fauna and flora introduced from a natural source. These communities were allowed to grow and become stabilised for a period of 2 months before experiments started, by which time a very good representation of stream organisms was established, including five species of stonefly (Plecoptera), three of mayflies (Ephemeroptera) and no fewer than nine species of caddis (Trichoptera), as well as the crustaceans Gammarus and Asellus.

The preparation of this review, and the final writing up, was only made possible by generous support from two organisations, namely the Water Research Centre, Medmenham, Marlow, Buckinghamshire, UK, and Jealotts Hill Research Station (ICI Plant Protection), Bracknell, Berkshire. I am greatly indebted to the sponsors concerned, Mr J. F. Solbe of the WRC and Dr B. G. Johnen of ICI for authorising donations without which this project would not have seen the light of day. Their assistance was particularly vital, coming as it did at a period when research funding in general, and in this field in particular, was being severely restricted in this country.

I am also grateful for the cooperation of many colleagues through correspondence from overseas, who have not only been kind enough to send reports and material not easily available here, but who have also – by correspondence – provided up-to-date progress information and comments. I am particularly indebted to the following: Dr Peter Kingsbury of the Canadian Forest Service; Dr D. C. Eidt of the Maritime Forest Research Centre, New Brunswick; Dr P. E. K. Symons of the Fisheries Research Board, Canada; Dr W. 0. Haufe of the Animal Parasitology Research Station, Lethbridge, Alberta; Dr Joan Trial of the Department of Zoology, University of Maine, US; Prof. John Giesy of the Pesticide Research Centre, Michigan State University, US; Dr. Aarne Lamsa, of the Great Lakes Fishery Commission, Ann Arbor, Michigan; Dr L. A. Norris of the USDA Forest Service, Oregon State University, US;

‘Realities’ in dealing with Antarctica

Central to all considerations of Antarctica is the fact that there is no agreement on the issue of sovereignty. But it could also be said that except inter se the seven claimant states (and leaving aside the matter of overlapping claims), all other states do not recognize these claims. There is also a large unclaimed sector. In addition, two states assert they have a ‘basis of claim’. Thus, in relation to the sovereignty issue, there is the reality of the claims, on which the claimant states are insistent; there is also the reality that these claims are not recognised by an overwhelming majority of states.

There are other realities which include the following:

1. i) the Antarctic Treaty has existed since 1959 and today has 32 signatory states; a number of conventions and agreements have evolved within the framework of the Treaty dealing with various activities in Antarctica; the parties to the Antarctic Treaty System (ATS) are anxious that its achievements which are based on the fragile agreement of Article IV of the Treaty, should not be prejudiced;

2. ii) Antarctica is not a minute atoll of no significance but it occupies some l/10th of the surface of the globe with a strategic location, fragile ecosystem, rich marine and, possibly, mineral resources; it therefore has great significance for international peace and security, economy, environment, scientific research, meteorology, telecommunications and so on; it also has no permanent human habitation;

3. […]

Introduction

Public interest in Antarctica is probably greater now than for many years, and seems likely to grow. Much of this interest is due, directly or indirectly, to the intergovernmental negotiations in which participating states are seeking to reach agreement upon a regime to govern the possible future search for and development of Antarctic minerals – negotiations which began formally in 1982, but for which the groundwork had been laid over the previous decade. These negotiations are still continuing. Add to this the potential economic significance of the subject-matter of the negotiations, the appeal of Antarctica and its capacity to stir the imagination, and speculation about untold wealth lying below the ice, and it is not hard to see why public interest is aroused.

The Antarctic minerals negotiations must, however, be set in a slightly different, and less glamorous, perspective. The realities can, perhaps, best be appreciated by posing, and then trying to answer, some basic questions:

1. i) What minerals?

2. ii) Why try to negotiate a regime now?

3. iii) Why does a regime have to be negotiated?

4. iv) Why should the Antarctic Treaty Consultative Parties be conducting negotiations?

5. v) What are the real problems?

6. vi) What are the answers?

What minerals?

In the present state of knowledge, speculation about untold mineral wealth in Antarctica, of an ‘El Dorado of the ice’, is no more than that – speculation. That cannot be emphasised too strongly, or repeated too often. The geology of Antarctica is something best left to others, but very much in laymen's terms, and in summary, such geological evidence as there is suggests that mineral deposits could well exist in Antarctica.

In 1984 the Secretary-General reported that ‘exploration for mineral deposits has barely started in Antarctica’. The reasons are clear; there is little incentive to search for economic deposits because of the hostile environment, lack of infrastructure, significant transportation problems, and high costs of exploration and mining operations and of developing the necessary technology. It is notable, for example, that the Antarctic continent is submerged thousands of feet below sea level by an ice-cap and only approximately 2% of the entire continent is exposed.

Despite these apparently insuperable difficulties, international attention has been attracted by discoveries of natural gas by the Glomar Challenger on the continental shelf off the Ross Ice Shelf in 1973, interests which became more acute after the oil crisis of 1970. Indeed, spectacular claims were made for a ‘Middle East’ in the Antarctic, including an assertion by the Wall Street Journal that oil reserves reported by the United States Geological Survey almost matched ‘the proven reserves of the entire United States’. Geological surveys which have been undertaken suggest a more conservative estimation of resources. Two mineral accumulations have been identified which are sufficiently large to term ‘deposits’; iron in the Prince Charles Mountains and coal in the Transantarctic Mountains. Occurrences of a wide range of minerals have been recorded including: copper, molybdenum, gold, silver, chromium, nickel, cobalt, tin, uranium, titanium, manganese, lead and zinc. Predictions are based in part upon the similarity between the Antarctic continent and other southern continents of comparable structure and age.