This study aimed to evaluate the human induced impact of a channel opening in a choked lagoon and attempted to establish the cause-effect links for the observed changes. The same lagoon system was sampled before and after the channel opening event, and the differences in fish and crustacean assemblages and environmental variables between these periods analysed. The opening of the artificial channel resulted in salinity increases, leading to a shift in species composition, favouring marine species and reducing abundance and diversity of previously dominant freshwater species. Furthermore, saltwater entrance into the choked lagoon caused an unexpected decrease in species richness and biomass, plus deterioration of ecosystem processes, reducing fishing capacity. The effects of salinity on the ecosystem vary depending on the ecosystem's composition and capacity to overcome salinity changes, thus specific monitoring projects are important strategies for developing coastal lagoon conservation management.
Beach seining is used for capturing surf-zone fishes for scientific or fishery purposes. Sampling gear and different sampling approaches pose difficulties for comparative analyses. We compared parallel tows (PT) and beach hauls (BH) using the same beach seine, observing differences in species number (SPUA = number of species m–2), total and relative abundance (CPUA = number of individuals m–2) and average size. ANOVA and PERMANOVA showed that both the number of species and abundance were significantly different between sampling approaches and seasons, with higher values for BH. Most abundant Umbrina coroides showed significant interactions with higher CPUA for PT in summer and Diplodus argenteus for BH from winter to summer. Harengula clupeola and Trachinotus carolinus showed significant differences between sampling strategy with BH capturing more individuals. Trachinotus carolinus and Sardinella brasiliensis both showed differences between seasons with higher CPUA in the summer and autumn respectively. Results suggest that catch structure and composition differ between sampling strategies, but a seasonal component associated with recruitment of one or more species also influenced the catch. The PT appears to be more effective but time consuming. The BH may be an alternative method, but results may not be comparable.
This paper aims to study the ontogenetic sexual dimorphism of Genidens genidens in Guanabara Bay, southeastern coast of Brazil. Altogether 378 specimens were anayzed (233 females and 145 males) with total length ranging from 13.3 to 43.5 cm. Specimens were measured for 12 body measurements, sex was identified and maturity stages were recorded and classified. Pearson’s linear correlation reveled a significant positive correlation between total length and all other body measures, except for base adipose fin, mouth depth and eye depth for immature females. Analyses nested PERMANOVA desing showed significant differences between maturity stages for each sex, between sexes considering or not maturity stages, indicating a variation in morphometric characteristics driven by sexual dimorphism. Differences among all maturity stages were also found, indicating an ontogenetic morphological difference. But immature individuals didn’t differ between sexes indicating that differentiation patterns starts with sexual development. The most important measures differing males and females were related to head characteristics, which appears to be key parameters to evaluate sexual differences. Due to male incubation of fertilized eggs and juvenile individuals <59 mm in their oral cavity, head measures are proposed to be sex dimorphism not related to reproduction, but with post reproductive fase due to ecological and biological needs. [L1]Modificated as suggested by Reviewer E.
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