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Shallow Water Reef-Associated Finfish

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Shallow Water Reef-Associated Finfish CHAPTER 8 Shallow Water Reef-associated Finfish Andrew Wright I. INTRODUCTION Throughout the western and South Pacific, reef-associated finfish form the basis of most subsistence fisheries. In many areas, this resource is also fished on a commercial scale. Although user conflicts resulting from the sharing of this resource are well known, studies detailing social and resource interaction issues that develop with increased fishing are limited. Compounded by a poor understanding of social factors affecting fishing in coastal communities throughout the Pacific is a generally poor but increasing knowledge of the population biology and fishery dynamics of target finfish resources. At least this is the case from the perspective of western science. Current knowledge of the biology and population dynamics of many fish species targeted by small-scale fisheries in the South Pacific region is poor relative to that available for the site-attached component of the reef fish community found in shallow water. This component, which is relatively easy to study, comprises mainly small species that are generally planktivorous or herbivorous and school, is currently only lightly exploited throughout the South Pacific region for the aquarium trade (see Pyle, this volume). Documented knowledge of the biology and population dynamics of food fish such as the scarids, lethrinids, lutjanids, carangids and the serranids, has improved significantly during the last decade. Contributing to the rapid in­ crease in knowledge of these fish is the fact that these families are generally circum-tropical in distribution. Thus information recorded throughout their range assists in providing a fundamental understanding of the biology of the same species in the South Pacific. In the short- to medium-term, fisheries managers in the South Pacific islands countries will continue to rely on such sources of information. At present, local research is generally not well pre­ pared, in terms of financial and manpower resources, to undertake comprehen­ sive studies of fish biology which could support fisheries development and management throughout the region. 204 Andrew Wright However, among many South Pacific coastal communities, there exists a depth of understanding of marine resources and their environment that has been accumulated over centuries of observation and which is passed orally among generations. In few instances has this reservoir of knowledge and associated traditional practice been applied to contemporary fisheries development and management issues. Documentation of this information which commenced in the late 1970s in Palau (Johannes, 1977,1978a, 1981 a) has since been expanded throughout the region (e.g. Johannes, 1982a and b; Hviding, 1990; Sims, 1990, Zann, 1990, Polunin, 1990; Baines, 1990; Wright, 1990). The South Pacific presents some unique opportunities for innovative man­ agement of fisheries development. It is a region where western concepts and aspirations increasingly impinge upon traditional values and practices. It is a region not only where politics are playing an increasing role in resource use decisions but also where rural communities utilise the traditional knowledge base to extract maximum, but not necessarily sustainable, benefit from resource exploitation. This chapter reviews information that is available on the biology of tropical reef-associated finfish that are taken by fisheries operating in the islands of the western and South Pacific. In many instances it is complemented by chapters elsewhere in this volume on small schooling pelagic fishes, deepwater reef slope finfish resources and aquarium fishes. It commences with an overview of the zoogeography and taxonomy of the major family groups considered, outlining difficulties experienced by biologists in islands countries with identification of species. This is followed by discussion of habitats associated with reef systems in the western and central Pacific and factors affecting finfish diversity. The following section is concerned with the study of diets and trophic relationships of finfish in reef-associated environments. Methods for the study of reproduc­ tive biology, mortality and growth and the conclusions of research on these topics are then discussed. A brief description of fisheries operating in the South Pacific, including gears and catch composition, precedes a final section which introduces issues associated with attempts to manage multispecies fisheries for finfish among islands communities in the South Pacific. In most instances the information has been retrieved from published sources and in these situations, full citations are given. A comprehensive bibliography accompanies this review to facilitate the work of fisheries researchers in the region. Not all these references have been cited in the text; they are provided as a guide for further reading and a starting point for research. In addition, citations have largely been limited to those in the English literature. There is also a significant amount of information, albeit largely inaccessible to many researchers in Pacific islands countries, in the Chinese, French, Soviet and Japanese literature. Shallow Water Reef-associated Finfish 205 II. LIFE HISTORY AND POPULATION BIOLOGY It is probable that there are between 6,000 and 7,000 species of fishes distributed through two classes, Osteichthyes and Chondrichthyes, throughout the Indo-Pacific faunal region. The 20 to 30 species of cartilagineous fishes, some of which are of interest to fisheries, are discussed elsewhere (Nichols, this volume). This chapter generalises across 2,000 species of ray-finned fishes (Actinopterygii) found in association with coral reefs, or approximately half the total shore fish fauna recorded from the Indo-Pacific region and one-sixth the total known to science. It is the 300 or more species representing 30 to 50 families taken by subsistence or commercial fisheries that are of primary interest here. Dalzell (this volume) discusses the biology and fisheries for small schooling pelagics associated with coral reefs, Moffit (this volume) discusses those species found in deeper water on reef slopes and Pyle (this volume) discusses the smaller species generally not targeted by food fisheries but which are commercially valuable in the international aquarium trade. ZOOGEOGRAPHY Although this review is primarily concerned with the island groups of Melanesia, Micronesia and Polynesia, the geographical distribution of many of the species of finfish considered in this chapter extends throughout the tropical Indo-Pacific. The largest diversity of tropical marine fishes is found in the southern Philippines and eastern Indonesia where 90 per cent of all shore fishes recorded from the Indo-Pacific are found (Myers, 1989). Within the western Pacific region, 165familiescomprisingmorethan2,500specieshavebeenrecorded. The diversity of the nearshore fish fauna decreases east and west of this region (Sale, 1980; Springer, 1982; Woodland, 1986). As noted by Myers (1989), although field material facilitating a comparison of fish diversity across the tropical Pacific is generally lacking, available data illustrates how dramatic the change in species diversity is (Fig. 1). There are a large number of fish species found in Indonesia and the Philippines which do not occur to the east; 151 reef species do not occur beyond Yap or Palau and 231 reef species do not occur east of the eastern Carolines (Myers, 1989). This is related to a number of biotic and abiotic factors including the apparent frequency of environmental disturbance (Sale, 1980; Springer, 1982; Rosenblatt and Waples, 1986), geological history, the diversity of habitats available in the mid-South Pacific with a decrease in the occurrence of high islands and an increasing prevalence of atoll-type environments eastwards. On the basis of life history strategies, Kulbicki (1992) analysed community struc- / Ryukyus 1 Hawaiian Islands >1,209 /.' 460 <Z J) Philippines Marianas 872 \ Johnston Is. fc5? Belau-Yap 271 , "': Marshalls . 827 j y Papua New Gu e. Carolines ".. Marqu I Society IIs . /' ca- 35 / " , ; -. ' P Rapa 220 Figure 1. The southern and western Pacific region illustrating recent estimates for the num region and likely routes of colonisation (after Myers, 1989). Shallow Water Reef-associated Finfish 207 ture for a range of reef systems across the Pacific. Based on a division of life history characteristics ranging from small, short-lived, relatively highly fecund species that attain maturity early in their life cycle to large, late maturing, long- lived species, he described two major groups of reef fishes in the region: 1) a western and central Pacific group which comprised three sub-groups, the West Pacific, central Pacific and the Great Barrier Reef-New Caledonian regions and 2) an eastern and southern Pacific group sub-divided into Hawaiian, Polynesian and Southern regions. These groupings mirror well the limits of tectonic plates in the Pacific region. The number of species of scarids and siganids, for example, decreases across the central Pacific to the east. Whereas the greatest number of scarid species, approximately 30, is recorded in the Philippine and Indonesian Archipelagoes, and the adjacent western Pacific, the tropical eastern Pacific supports only six species, three of which are endemic (Choat and Randall, 1986). Similarly for siganids, thirteen species are reported from the Philippines, 10-12 from Mela­ nesia, 6 from Micronesia and only 2 from Western Samoa in the east (Woodland,
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