Length–weight relationships for estuarine fishes in subtropical estuary

The present study describes the length/weight ratio (LWR) of 20 fish species caught in an intertidal area of the Paranaguá Estuarine Complex, southern Brazil. Fish were caught with three beach seine nets, with 2m high, 70m long and distance between knots of 2.5; 4 and 5cm. A total of 880 individuals of 21 species belonging to 11 families were captured, ranging from 5 to 75.5cm in total length. All species analyzed are widely distributed throughout the Southwestern Atlantic. Positive allometric growth (b > 3) was predominant, occurring in 60% species, 35% presented negative allometry (b < 3) and only 5% had isometric growth (b = 3). Many factors could be influencing the distinct growth patterns observed between the literature and the present study, such as the environmental influences, the reduced number of specimens, the sampling methods, the sampling periods and the estimation of the LWR with grouped sexes.

Length–weight relationships comparison between juveniles and adults of fish species from the mangroves of south Brazil

This study reports the length‐weight relationships (LWRs) for 8 fish species that inhabit mangroves. Many fisheries depend on mangroves, which serve as nursery and feeding areas for the juvenile stage of fishes, shrimp, and other fishery resources. In this sense, mangroves provide many ecosystem services, therefore increasing the basic biological knowledge of these ecosystems can help to understand their functioning and create conservation strategies. The majority of LWR studies do not consider juveniles, and it is important to consider these differences as juveniles can grow differently from adults. The fishes were collected from Perequê mangrove, Paraná, Brazil between 2008 and 2010. A variety of fishery gears were employed, including trammel nets, fyke nets, and traps made with plastic bottles combined with four baits. The specimens were measured (weight and length), sexed and evaluated for maturational stage. For the adults, the LWRs were calculated separately by the sex, while juvenile LWRs were estimated together. In general, there were differences in growth type between sexes and life stages. Some species showed differences compared to FishBase estimations, but this could be due to the lengths (and life stage) of the individuals used in the present study compared to FishBase. The discrepancies between adult, juvenile and FishBase estimations showed the importance of considering these aspects in studies using LWR.

Short-term variability of bacterioplankton in the maximum turbidity zone in the Paranaguá Bay, Southern Brazil, and its relationship with environmental variables

In this work, the density of bacterioplankton, bacterial biomass and environmental variables were monitored in two seasons (summer and winter), two times each month (spring tide and neap tide sampling), over a 12 h period, comprising a tidal cycle (semidiurnal), from subsurface and bottom waters, in a fixed station in the Estuarine Turbidity Maximum Zone (ETMZ) of Paranaguá Bay, Brazil. The data were treated with multivariate analyses methods in order to indentify the key controlling factors of the bacterial community dynamics. The microbial community seemed to be structured by a close relationship with the nutrients concentration, mainly by total phosphorous and nitrate. Regardless of variations throughout the tidal cycles, free-living bacteria had a dominant role on the Paranaguá's Bay ETMZ.

Introduced and cryptogenic species and their management in Paranaguá Bay, Brazil

The aim of this work was to identify the introduced and cryptogenic species in encrusting and associated communities of hard substrates in Paranaguá Bay, Brazil, and to attempt to determine which of these species could negatively affect the local community to suggest management strategies for these species. At least four introduced species were found - a large number in comparison with other port surveys. These were the hydrozoan Garveia franciscana Torrey, 1902, the polychaete Polydora cornuta Bosc, 1902, the barnacles Amphibalanus reticulatus (Utinoni, 1967) and Striatobalanus amaryllis Darwin, 1854, all with potentially harmful impacts. Of the 33 cryptogenic species, four were also listed in the literature as causing negative effects. We propose the following management practices: periodic cleaning of all underwater structures, population monitoring of invasive species and potential substrates, an information database of potential sources of introduction.

Espécies marinhas exóticas (= não-nativas) podem afetar drasticamente as comunidades das regiões em que são introduzidas. Prever quais espécies possuem maiores chances de causar impactos negativos é extremamente importante. Neste estudo, identificamos espécies introduzidas e criptogênicas entre as espécies incrustantes e associadas das comunidades que ocorrem nos substratos consolidados da marina do Iate Clube de Paranaguá. Com base em literatura, verificamos quais destas espécies são capazes de afetar negativamente a comunidade local e sugerimos recomendações para seu manejo adequado. Quatro espécies introduzidas foram identificadas, o que é uma cifra elevada quando comparada a outros levantamentos de biotas portuárias: o hidrozoário Garveia franciscana Torrey, 1902, o poliqueta Polydora cornuta Bosc, 1902, e as cracas Amphibalanus reticulatus (Utinoni, 1967) e Striatobalanus amaryllis Darwin, 1854, todas com efeitos negativos já registrados em outros locais. Entre as 33 espécies criptogênicas, quatro também são relatadas na literatura pertinente como causadoras de impactos negativos. Ações de manejo propostas incluem limpeza periódica dos cascos das embarcações e estruturas da marina, monitoramento das populações de espécies com potencial invasor, monitoramento dos substratos naturais para detecção de espécies introduzidas, criação de um banco de dados com informações sobre as viagens dos barcos de recreio e possíveis rotas de dispersão das espécies.