Coral reef fish assemblages of Baie Ternay National Marine Park and Baie Beau Vallon, Mahé, Seychelles
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The two most important foreign exchange earning activities in the Seychelles are tourism and fisheries and therefore, the coastal areas and their management are of the greatest importance to the Seychelles government (Khadun, 1991). In recent years government policy has encouraged marine conservation (Procter, 1970; 1984-1989 National Development Plan) and is part way to fulfilling the programme outlined in the Environmental Management Plan of the Seychelles (EMPS, 1990-2000). To date, five marine areas have been designated as national marine parks covering about 23 000 ha with several more proposed parks and protected areas. However, financial constraints, a deficit of qualified personnel, lack of boundary delimitation, inadequate legislation and increasing development has meant that the parks have never been managed or protected adequately. Increased tourism and poaching is leading to damage to reef integrity and decreasing aesthetic appeal due to anchor drops, illegal collecting and fishing, land based pollution and sedimentation as well as increased littering (EMPS, 1990-2000 and pers. obs.). Many natural communities worldwide are experiencing large and fundamental changes in structure, often as a result of anthropogenic activities and often manifesting themselves as a decrease in diversity (Sebens, 1994). The difficulties of monitoring reef ‘health’ through indicator species or species distributions is well documented. Problems usually arise due to a lack of baseline data, lack of fixed location monitoring sites, variation in methodology and often unsuitable comparative data. It is also particularly difficult to isolate some early stages or low level impacts, from normal variation. An important initial phase of any effective program of action is the collection and interpretation of baseline data on the distribution and richness of fish and invertebrate communities and assessments of the state of the reef habitat. A wealth of studies have examined distributions of reef-associated fish throughout the tropics yet remarkably few studies have sought to quantify the reef fish communities of the granitic Seychelles. It has become increasingly evident that assemblages of reef fish and their physical and biological environments vary greatly among habitat patches at all spatial scales (Bouchon-Navaro, 1980, 1981; Sale, 1980a; Harmelin-Vivien, 1981; Bouchon-Navaro and Harmelin-Vivien, 1981; Williams, 1982, 1983a, 1983b; Galzin et al, 1979, 1983, 1990, 1994; Bell and Galzin, 1984; Russ, 1984a,b; Williams et al., 1986a; Doherty and Williams, 1988a; Thresher, 1991; Roberts et al, 1992; TMRU, 1993, 1994, 1995; Caley, 1995a,b; and others). Generalisations concerning population dynamics and management strategies for fish communities must take into account spatial and temporal variation in diversity and abundance. Many factors have been attributed to variation in fish assemblages on coral reefs, including niche diversification, spatial and temporal variation in recruitment, food availability, live coral cover, substratum type, current flow, water quality, exposure to wave action, topographic complexity, availability of hiding places, and human extraction. Clearly, comparisons between reefs and within reefs must include information on a variety of influencing factors in any attempt to describe and explain species distributions. Analysis of data should provide meaningful baseline information from which to effectively manage, an increasingly important natural resource. Most published work on reef-associated fish in the Seychelles region has focused on taxonomy, with intensive collecting for museum curation. Smith and Smith (1969) and Randall and van Egmond (1994) give good historical accounts and bibliographies of this work to date. A brief account is given below. During French colonialism from 1743 until 1810, specimens were collected and sent to Paris, where they joined the collections to be later studied by Cuvier and Valenciennes and contributed to those species published in the volumes of Histoire Naturelle des Poissons in the early 19th century. The first species list of Seychelles fishes was compiled by Col. R.L. Playfair (1867) who recorded 211 species followed by Mobius (1880) and Mobius and Peters (1883) who listed fishes from Mauritius and Seychelles, Regan (1907) from Stanley Gardiner`s collecting in the Indian Ocean, and various resident collectors. Most notable is the work of Smith and Smith whose extensive collecting in 1954 culminated in the publication of Fishes of Seychelles in 1963 and a revised 2nd edition in 1969. 475 species were added to the known species list, with some 775 species described and illustrated from the Seychelles proper, (northern islands) including many pelagic and deep water species. However, many of these species have been regrouped since and some (particularly Labridae and Scaridae) are in fact juveniles or dichromatic variants of the same species. More recently expeditions to Seychelles (Seychelles Coral Reef Expedition, 1972, Catford, 1972 and RV Tyro Netherlands Indian Ocean Programme, 1992-3, van der Land, 1994) have added to the record of fishes. Polunin (1984) lists a further 79 records for the wider Seychelles and Randall and van Egmond (1994) a further 108 new records. Often overlooked and uncited in any of the recent literature and possibly the first paper on habitat and reef fish distributions in the Seychelles is by Landini and Sorbini (1988) on the ichthyofauna of back reef zones and sea grass environments of Mahe and Praslin. Artisanal fisheries and coral reef community structure in the Seychelles is currently an area of increasing interest and artisanal reef fisheries impact studies by Jennings et al. (1996a, 1996b) have compared fish community structure in areas exposed to varying fishing intensities.