Jean-Luc Bouchereau

Biodiversité et dynamique des peuplements ichtyiques de la mangrove de Guaratuba, Brésil

Abstract The Bay of Guaratuba, whose area is approximately 45 km 2 , is a basin, situated to the south of Brazil (25° 52′ S; 48° 39′ W) and connected to the Atlantic ocean. In its northern part, a region of mangrove is found, under the influence of seasonal fluvial contributions, dominated by Laguncularia racemosa . The depth exceeds 6 m in some places. According to the period of the year, salinity varies between 3 and 37, and temperature between 15 and 28 °C. Several of the present fish species are exploited by commercial and recreational fisheries. This work describes characteristics of the fish populations occupying this mangrove, and temporal and spatial evolution of populations of the main species from available data on their biology. Between September 1993 and August 1996, fish samplings have been undertaken monthly by trawl, according to the same fishing effort (20 min), in channels of this ecosystem. Size, numerical abundance and weight of each individual of species were measured, as well as surface and bottom temperatures and bottom salinity. Species richness, Shannon-Weavers diversity index were calculated and abundances were processed by the multivaried analysis. The global species richness is 61 species, distributed in 28 families; the better represented species are Sciaenidae (10), Gerreidae (5), Carangidae (5), Ariidae (4), Haemulidae (3), Serranidae (3), Bothidae (3). Each year, the number of species varies between 41 and 44, and a group of eight species represents between 80 to 90 % of the density and 75 % of the biomass. The constancy of this dominance is the main characteristic of this fish assemblage. The most represented species in abundance is Pomadasys corvinaeformis is the first two years, then Stellifer rastrifer . The group of eight main species is shared by 15 species in total, of which 13 for the density and 14 for the biomass. The most important monthly catches take place in winter season, during which one observes a decrease of water temperature and an increase of salinity. These species, however, being likely to be replaced by others according to the year or the season; one never finds the same composition in the assemblage which preserves always the same structures. Seasonal differences between seasons under marine (winter) and continental (summer) influences play a major role on the dynamics of fish in the Guaratuba mangrove. This ecosystem plays a functional role in the achievement of the life cycle of many permanent or temporary species. Those having succeeded to reach high levels of abundance are not represented in a uniform way in the course of the year, even when they reside permanently in the ecosystem. Periodic displacement strategies for self regulation of stocks abundance, are necessary mechanisms for these populations, which thus success to coexist in occupying the mangrove.

Factors Structuring the Ichthyofauna Assemblage in a Mangrove Lagoon (Guadeloupe, French West Indies)

Abstract The ichthyofauna of the Manche-à-Eau mangrove lagoon was regularly sampled in 2002 with a fixed net at seven stations during 4 months corresponding to two hydrological seasons. Physicochemical variables (depth, temperature, salinity, dissolved oxygen, pH) and population descriptors (species and family richness, density and biomass) were measured. The Whitefield and the well-being indexes were calculated to appreciate species equilibrium. Canonical correspondence analysis and generalized linear models were used to link species assemblages to physicochemical variables and to search for a special link with salinity. A total of 30,733 individuals belonging to 34 species and 23 families were collected. The Gerreidae, Clupeidae, Engraulidae, Scianidae, and Sparidae represented almost 98% of the total number of individuals. Our results show that organization of the fish assemblages in the lagoon is poorly dependent on salinity, whereas dissolved oxygen, temperature, and pH could have a stronger role. Looking at response curves to salinity change, most fishes species appeared to be visitors, either temporarily present or regular migrators. Only a few species compose the year-round resident population. They have a high patrimonial value and could be considered bioindicator species for long-term studies (e.g., of global change and natural or anthropogenic disturbances). The Euclidean distance and biomass variables were not useful descriptors of confinement and biological zonation in the lagoon, whereas the negative gradient of specific richness, number of individuals, Whitefield index, and index of well-being better described confinement. On the basis of these last parameters, biological zonation in the Manche-à-Eau lagoon was established and is provided.

Environmental and subtidal fish assemblage relationships in two different brazilian coastal estuaries

The general structure and organization of the shallow water (<1.5 m) fish assemblages were studied in two southern Brazilian ecosystems, a bay and a lagoon, under different marine or continental influences. The abiotic factors were measured to define the hydrology of the sites and the biotic descriptors were evaluated to characterize the assemblage structures. Transparency, salinity and organic matter were the abiotic factors which best distinguished the sites. A total richness of 69 species was observed. Ecological guilds, density, diversity and evenness indices values were different in each site. Hydrodynamism and geomorphology determined the structure and the organization of the fish assemblages in these shallow waters. It was observed that variations in the hydrological attributes generated by the marine or continental water movements are able to alter the conditions in the lagoon more quickly and at more regular frequencies than those in the bay.

Selection of candidate fish species for farming in the bay of Guaratuba, Brazil

An inventory of the maximum length (ML) reached by 57 species of fishes living in the mangrove of Guaratuba, Brazil, was undertaken with an aim to evaluate the relationship between the ecosystem and the size of individuals. For each of these species, the maximum length found in the region were compared with those available in existing literature. The majority of populations presented individuals whose length reached at least 40% than the known maximum length for the species, although only 19.3% were longer than 300mm in absolute value. Population of the other species were represented only by individuals either in their initial development phases, or reduced length as compared to the maximum length known elsewhere for the same species. In this mangrove, species having the largest relative size are generally those that had the smallest absolute length. Proposed is use of an index LR (maximum observed lengths/maximum available lengths) as a tool for description and comparison of fish assemblages. Observations of the maximum size make possible the pre-selection of 12 species for breeding tests. In combining the biological, technical and commercial parameters, the pre-selection retains as primordial the following species: Centropomus parallelus, Centropomus undecimalis, Menticirrhus americanus and Micropogonias furnieri.