Fishers' ecological knowledge of smalleye hammerhead, Sphyrna tudes, in a tropical estuary

Coastal hammerheads have suffered from overexploitation and environmental degradation. We interviewed 79 artisanal fishers to verify fishery aspects, temporal changes in catches and biological aspects of the smalleye hammerhead, Sphyrna tudes , in a marine protected area on Abrolhos Bank, Brazil. Data were compared between three generations of fishers: young, middle-aged and old. Fishers' age varied between 17 and 88 years. We verified significant reductions in the weight of individuals caught by younger fishers. The main types of fishing gear used to catch S. tudes were gill nets and longlines. Overfishing through gill nets and trawl fisheries were mentioned as the cause of S. tudes population collapse in the region. The shark's diet as reported by fishers consisted of fish, crab and shrimp; austral summer was the reproductive season. A strong similarity was verified between fishers' knowledge and biological data. We suggest as plausible strategies to conserve the local population of S. tudes the reduction of net fisheries impact through zoning and establishment of no take areas. These steps can help to initiate the recovery of this depleted species.

Tubarões martelo costeiros têm sofrido com a sobrepesca e degradação ambiental. Foram entrevistados 79 pescadores artesanais para verificar aspectos da pesca, mudanças temporais nas capturas e aspectos biológicos de Sphyrna tudes em uma área marinha protegida no Banco dos Abrolhos, Brasil. Os dados foram comparados entre três gerações de pescadores: novos, meia idade e mais velhos. A idade dos pescadores variou entre 17 e 88 anos. Verificaram-se reduções significativas no peso dos indivíduos capturados pelos pescadores mais jovens. Os principais petrechos usados para captura de S. tudes foram redes de emalhe e espinhel. Pescadores mencionaram que o colapso da população local de S. tudes foi decorrente do excessivo uso de redes de emalhe e pelas pescarias de arrasto. A dieta reportada foi peixes, caranguejos e camarões e a época de reprodução foi o verão. Uma forte similaridade foi verificada entre o conhecimento dos pescadores e dados biológicos. São sugeridas como estratégias plausíveis para conservar a população local de S. tudes a redução do esforço das pescas com rede através de zoneamento e estabelecimento de áreas de exclusão de pesca. Esses passos podem ajudar a iniciar a recuperação de espécies depletadas.

Ecomorphology and resource use by dominant species of tropical estuarine juvenile fishes

Eleven ecomorphological attributes and diet of seventeen juvenile fish species were examined to test the hypothesis that morphological patterns determine resource uses in estuarine habitats. Species were separated according to the apparatus to food capture and habitat use (benthic or pelagic) in three different groups: (1) a group with depressed fish body, strong caudal peduncle and enlarged pectoral fins; (2) a second group laterally flattened with a wide protruding mouth, and (3) a third group strongly flattened with small pectorals fins. The following six trophic groups were organized based on prey categories: Zooplanktivores, Benthivores, Omnivores, Detritivores, Macrocarnivores and Insectivores. Significant results (PERMANOVA) between ecomorphological indices and habitat and between ecomorphological indices and trophic groups were found. These data indicate that similarity of ecomorphological forms, which minimize the influence of environment and partitioning of food, would help facilitate the co-existence of these fish when they are abundant in this tropical estuary.

Onze atributos ecomorfológicos e a dieta de dezessete espécies de peixes juvenis foram examinados para testar a hipótese de que os padrões morfológicos determinam a utilização dos recursos em habitats estuarinos. As espécies foram separadas de acordo com o modo de captura do alimento e uso do habitat (bentônicos ou pelágicos) em três grupos distintos: (1) um grupo de peixes depressiformes, com forte pedúnculo caudal e nadadeiras peitorais alargadas; (2) um segundo grupo, compressiforme, com ampla boca protrusível, e (3) um terceiro grupo, fortemente achatado e com pequenas nadadeiras peitorais. Seis grupos tróficos foram organizados com base nas categorias de presas: Zooplanctívoros, Bentívoros, Omnívoros, Detritívoros, Macrocarnívoros e Insetívoros. Foram encontrados resultados significativos (PERMANOVA) entre os índices ecomorfológicos e o habitat e entre os índices ecomorfológicos e os grupos tróficos. Estes dados indicam que a similaridade ecomorfológica, que reflete o ambiente e o tipo de alimento consumido, facilitaria a coexistência desses peixes quando estes são abundantes neste estuário tropical.

Hidrografía y plumas estuarinas en Golfo Dulce, Pacífico Sur de Costa Rica / Hidrography and river plumes in Golfo Dulce, south pacific of Costa Rica

Resumen Variables oceanográficas en 33 estaciones en el Golfo Dulce, Costa Rica, entre 2009 y 2010 fueron analizadas a través de perfiles con CTD, donde la salinidad, la temperatura, sigma-T y las corrientes se estudiaron en la columna de agua. Disco Secchi y clorofila-a, fueron medidos a nivel superficial.. El objetivo fue estimar el área de dispersión de las plumas estuarinas a través del seguimiento de las variables físicas temperatura, salinidad y sigma-T. En agosto 2009, entre los ríos Coto Colorado y Esquinas disminuyeron la salinidad (<30) en un área de 250km2 aproximadamente, un 37% de la superficie total, creándose frentes termohalinos a lo largo de casi todo el golfo. Se documentó el efecto de El Niño Oscilación del Sur en enero 2010 durante su fase de acentuada intensidad. Las concentraciones de clorofila-a se correlacionaron en un 33.7% (P=0.05) con la transparencia del agua según el disco Secchi en la estación lluviosa. Se caracterizó el agua superficial del Golfo Dulce por tener salinidad <31.5 temperatura >27ºC y ocupar los cinco primeros metros de la columna de agua.

Abstract Oceanographic variables at 33 stations distributed in Golfo Dulce, Costa Rica, during the dry and rainy seasons between 2009 and 2010, were analyzed with CTD profiles, where salinity, temperature, sigma-T and currents were studied in the water column. Secchi depth and chlorophyll_a were measured in surface. The main objective was to estimate the catchment area and estuarine plume dispersion formed with river discharge. Between the rivers Esquinas and Coto Colorado, decreased salinity (<30) in an area of approximately 250km2, creating thermohaline fronts along most of the gulf. The El Niño South Oscillation, which was in the phase of heightened was documented. The chlorophyll concentrations correlated 33.7% with Secchi disc water transparency. The Golfo Dulce surface water was identified with salinity <31.5 and temperature >27°C (April to December). This research contributes to the knowledge of the oceanography of the Golfo Dulce and the feedback we receive from fluvial origin, claiming form providing inputs for the potential creation of a major new marine protected area system covering entire Golfo Dulce area and, ideally, the surrounding river systems that feed it. Rev. Biol. Trop. 63 (2): 161-181. Epub 2015 June 01.

Distribución espacial de las especies de mangle y su asociación con los tipos de sedimentos del sustrato, en el sector estuarino del Humedal Nacional Térraba-Sierpe, Costa Rica / Spatial distribution of mangrove species and their association with the substrate sediment types, estuarine sector Térraba-Sierpe National Wetlands, Costa Rica

Resumen Se describe la composición florística del manglar y la distribución espacial de las principales especies de mangle y otras especies vegetales asociadas, presentes en el sector estuarino del Humedal Nacional Térraba-Sierpe, mediante el levantamiento de campo de 1 127 puntos y 77 parcelas de muestreo de 60x10m. Por otra parte, se explora la relación entre el tipo de sedimento subyacente y las especies de mangle establecidas sobre éste. Los resultados de composición, estructura y distribución de la vegetación del HNTS, muestran que el manglar exhibe un modelo o zonación, consistente en la variación desde la costa al continente y de las márgenes de los canales o esteros al interior de las llanuras de marea, de las distintas especies. Rhizophora racemosa y Pelliciera rhizophorae son las especies que muestran una mayor distribución espacial o distribución continua, con los mayores valores de abundancia (45.44% y el 39.92%, respectivamente), frecuencia (88.31% y 74.03%) y área de manglar (7 670.73ha y 5 824.94ha). Se confirmó la dependencia entre la presencia de especies de mangle y el tipo de sedimento del sustrato, de modo que las especies Avicennia spp. y L. racemosa tienden a distribuirse en los sustratos arenosos con mayor facilidad que las otras especies cuya distribución es más homogénea sobre los sustratos lodosos.

Abstract This research describes the floristic composition and spatial distribution of the main mangroves species and other associated flora present in the estuarine sector of Térraba-Sierpe National Wetland, Costa Rican Pacific. Field survey consists of 1 127 points and 77 sampling points of 60x10m. Results of composition, structure and distribution of mangrove in HNTS exhibits a pattern or species zonation. We found variation from the coast to mainland and from the fringe or estuaries to the interior tidal flats. The species Rhizophora racemosa and Pelliciera rhizophorae showed greater spatial and continuous distribution, with the highest values of abundance (45.44% and 39.92% respectively), frequency (88.31% and 74.03%) and mangrove area (7 670.73ha and 5 824.94ha). The mangrove fern, Acrostichum aureum, was the third most important species, meanwhile, Avicennia spp., Rhizophora mangle y Laguncularia racemosa showed a segregated distribution or a tendency to local conglomeration, Talipariti tiliaceum var. pernambucense, Mora oleifera y Conocarpus erectus were found in very localized areas and other species were considered companions with low contribution to the total coverage. The dependence was confirmed between the presence of mangrove species and sediment type substrate. The species Avicennia spp. and L. racemosa tend to be distributed in sandy substrates more easily than the other species whose distribution is more homogeneous on muddy substrates. Rev. Biol. Trop. 63 (Suppl. 1): 47-60. Epub 2015 April 01.

Productividad primaria en el Humedal Nacional Térraba-Sierpe, Costa Rica / Primary productivity in the National Térraba-Sierpe Wetland, Costa Rica

Resumen Se determinó la productividad primaria (PP) del fitoplancton en un amplio sector del Humedal Nacional Térraba Sierpe (HNTS) de Costa Rica, durante la estación lluviosa del año 2008 y en la estación seca del año 2009. Seis sitios se ubicaron en las áreas norte y central del humedal, donde por lo general ocurre la mayor influencia del aporte de caudal del Río Grande de Térraba. Se realizaron adicionalmente determinaciones de otros parámetros ambientales, asociados con la productividad primaria, como profundidad de penetración del disco de Secchi, la concentración de sólidos en suspensión, la concentración de clorofila a, la salinidad, la temperatura, la concentración del oxígeno disuelto en el agua, la concentración de nutrimentos inorgánicos disueltos (amonio, nitrito, fósforo disuelto, silicato), la conductividad eléctrica específica y se llevó a cabo un estudio basado en el análisis de componentes principales. La PP en el HNTS fue en general baja, con un valor máximo de 8.16gC/m2·d de PPN, el cual se registró en la estación seca, en marzo del 2009, en Isla Loros. Los sitios de mayor influencia del río (Samu y El Caite en la estación lluviosa), fueron los que tuvieron valores más bajos, mientras que los sitios con mayor influencia marina fueron los que presentaron los valores más altos de este estudio, cuyo promedio y desviación estándar fue de 0.79±0.50gC/m2.d (n=12), y la mediana fue 0.80gC/m2.d. Esta diferencia se debe principalmente al elevado aporte de agua dulce y de sólidos en suspensión del Río Grande de Térraba que limita el desarrollo del fitoplancton marino en el humedal. Es importante que se establezca y mantenga un programa de monitoreo de los parámetros medidos en este estudio, con al menos dos muestreos por año, uno en la época seca y otro en la época lluviosa, siguiendo el gradiente de salinidad desde el río hasta el mar al menos en dos direcciones.

Abstract Phytoplankton primary production (PP) was determined in a broad sector of the Térraba-Sierpe National Wetland, Costa Rica, from September to November 2008 in the rainy season and from January to March 2009 in the dry season. Six sampling stations were located at the Northern and Central zone of the wetland, according to the main expected flux of Río Grande de Térraba. Additionally other environmental parameters such as Secchi disk depth, suspended solid matter concentration, chlorophyll-a concentration, salinity, temperature, dissolved oxygen concentration, dissolved inorganic nutrients concentrations (phosphate, nitrate, ammonium and silicate), specific conductivity were also measured and a principal components analysis was performed. The PP in the Terraba-Sierpe National Wetland (HNTS by its Spanish name) was generally low, with a maximum value of 8.16gC/m2·d of Net Primary Productivity (NPP), which was recorded in the dry season, in March 2009, at Loros island. Sites that had a greater riverine influence showed lower PP values, while sites with greater marine influence presented higher PP values. These latter had an average and standard deviation of 0.79±0.50gC/m2·d (n=12). This difference is the result of the high input of freshwater and suspended solids from the Río Grande de Térraba which limits the development of marine phytoplankton in the wetland. Rev. Biol. Trop. 63 (Suppl. 1): 9-28. Epub 2015 April 01.