Paulo de Tarso Chaves

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.

Study on feeding habits in estuarine fish (Teleostei) comparatively between salt marshes and mangroves in southern Brazil (Guaratuba Bay)

Estudou-se a composicao da dieta de peixes em dois tipos de ambiente de areas rasas estuarinas - marisma e manguezal, objetivando avaliar se essas formacoes vegetais desencadeiam na ictiofauna respostas diferentes quanto a alimentacao. As seis especies avaliadas, as mais abundantes nessas areas, mostraram-se predominantemente planctivoras, porem com particularidades quanto ao tipo de vegetacao ocupada. Na marisma, Atherinella brasiliensis (Quoy & Gaimard, 1825) apresentou a dieta com maior numero de itens e menor similaridade em relacao as demais especies. No manguezal tal isolamento coube a Anchoa januaria (Steindachner, 1879), especie com maior participacao de Decapoda Brachyura e Decapoda nao-Brachyura, e unica que nesse ambiente incluiu Gammaridae na dieta. Anchoviella lepidentostole (Fowler, 1911) identificou-se com Anchoa lyolepis (Evermann & Marsh, 1900) na marisma e com Opisthonema oglinum (Le Sueur, 1818) e Harengula clupeola (Cuvier, 1829) no manguezal. Uma situacao comum a marisma e manguezal registrou-se entre O. oglinum e H. clupeola, especies com dietas praticamente restritas a Diatomacea e Copepoda. Evidenciou-se o quanto as especies sao capazes de variar sua dieta com o ambiente, provavelmente em resposta a disponibilidade local. Mais que isso, porem, constatou-se que, seja na marisma, seja no manguezal, mesmo havendo mudanca nos habitos troficos das especies, cada uma delas mantem um padrao de diferencas em relacao as demais que compoem a assembleia, fato que possivelmente assegura a abundância e coexistencia entre elas nas areas estuarinas rasas.

Use of an estuarine environment (Barra do Saí lagoon, Brazil) as nursery by fish

Studies were carried out at the Barra do Sai lagoon, on the northern coast of Santa Catarina State, Brazil, to evaluate the function played by this estuary in the life cycle of fish found at the coastal zone. Samplings were performed using beach seine net from December 2000 to November 2001. The continental influence is strong, as showed by the occurrence of freshwater fishes, although most of the 43 species recorded are marine ones. It was verified that around summer, when the temperature of the water is high, the values of salinity decrease and those of turbidity increase. At this time there is also an increase in the abundance of juvenile fish in the lagoon. Because of its average depth of less than 0.7 m, the lagoon is inhabited primarily by juveniles, which may enter either by active movement or passive displacement, originating from the sea or the river to which the lagoon is connected. The lagoon is not used for sheltering spawning individuals. It is showed that a shallow, small estuary with a blind bottom can conceal an importance for the coastal ichthyofauna that is greater than it could be expected from the occurrence - in this case, modest - of large individuals.

Biologia de Paralonchurus brasiliensis (Steindachner) (Teleostei, Sciaenidae) no litoral sul do Estado do Paraná, Brasil

The populational structure, reproduction and feeding features of banded croaker in southern coast of Parana State are presented. Samplings were performed through bottom trawl from March 1999 to January 2000 at depths 10 and 15 m. Paralonchurus brasiliensis is more abundant during spring, when the youngest individuals, smaller than 93 mm, are recruited. The relation weight/length for grouped sexes is TW(g) = 2.74E -6 TL(mm) 3.22 (n = 659; R 2 = 0.99). Gonadal maturation is recorded since the length class 130-165 mm and the average length of the first maturation (grouped sexes) is estimated in 175 mm. Sand worms (Polychaeta) are the feeding item more usual for the all size classes and seasons, followed by crustacean and fishes. Species reproductive period extends from autumn (start maturation) to summer (end the spawning). After spring, youngs probably leave the area 10 m of depth. The prohibition of the shrimp bottom trawl in this depth during the spring and the summer must be efficient to reduce P. brasiliensis by-catch, today composed by recruits or spawning proximity individuals.

Biology of Chirocentrodon bleekerianus (Poey, 1867) (Clupeiformes: Pristigasteridae) in a continental shelf region of southern Brazil

This study provides information on the biology of C. bleekerianus from Parana State coast, Brazil, assembling data about its abundance, size structure, diet and reproduction. Monthly collections were accomplished in 1999 and 2000 in the internal continental shelf, with trawl net. The catch-per-unit-effort did not vary significantly among the seasons. In the summer, the individuals were larger, followed by autumn, spring and winter. C. bleekerianus was predominantly planktivorous and the most frequent items in its diet were copepods followed by diatomaceous algae. Seasonal variation in the frequency values of the gonad maturation stages, gonadossomatic index and gonadal condition factor indicated that the reproductive period encompassed spring and summer. The mean total length at first maturity of females was estimated to be 76 mm.

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.

Artisanal fishing net float loss and a proposal for a float design solution

Plastic floats from fishing nets are commonly found washed up on beaches in southern Brazil. They are usually broken and show signs of having been repaired. Characteristics of floats and interviews with fishermen suggest two main causes of float loss. First, collisions between active gear, bottom trawl nets for shrimp, and passive gear, drift nets for fish, destroy nets and release fragments of them, including floats. Second, the difficulty with which floats are inserted on the float rope of the nets when they are used near the surface. Floats are inserted to replace damaged or lost floats, or they may be removed if it is desired that the nets be used in deeper waters. Floats may thus be poorly fixed to the cables and lost. Here a new float design that offers greater safety in use and for the replacement of floats is described and tested.