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The consistency and environmental correlates of habitat- and season-related differences among shallow-water fish assemblages inhabiting estuarine beaches (EB) and tidal flats (TF) were examined in the subtropical Paranaguá estuary, which borders a World Heritage listed area. Assemblages were diurnally sampled each month (May 2003–March 2004) using small-meshed beach seines. Forty-six and 49 species were captured at EB (24 families) and TF (23 families), with most individuals at the latter (66 and 54% by number and biomass). Resident fishes accounted for 74% of individuals, but only 31% of all species. Most species were juvenile marine transients, but occurred sporadically and in low numbers. Three residents ( Sphoeroides testudineus , Atherinella brasiliensis and Sphoeroides greeleyi ) dominated assemblages and contributed the most to the index of relative importance of each habitat. Habitat-related differences in assemblages and key population parameters were complex and generally depended on the month sampled rather than water salinity or temperature (owing to comparable temporal variability). Ocean proximity was probably the cause of some differences, with more recruits of marine species early in the wet season at EB, but later at TF. Nevertheless, some resident gobiids and paralichthyids displayed habitat partitioning, possibly related to sediment preferences. There were strong seasonal differences in assemblages, primarily due to more juveniles of resident and transient species during the wet and possibly reflecting more optimal conditions for the young-of-the-year survival due to increased primary and secondary productivity. Environmental correlates of salinity and temperature with assemblage parameters were generally weak, but increasing water temperature prior to the wet season may be a key driver for reproduction, so that larvae are delivered during the wet season. The shallow, low-energy sandy beaches and tidal flats are used by a large diversity of fish, and consequently need to be considered in conservation and biodiversity estuary management plans. [ABSTRACT FROM AUTHOR]

While the number of species is a key indicator of ecological assemblages, spatial conservation priorities solely identified from species richness are not necessarily efficient to protect other important biological assets. Hence, the results of spatial prioritization analysis would be greatly enhanced if richness were used in association to complementary biodiversity measures. In this study, geographic patterns in estuarine fish species rarity (i.e. the average range size in the study area), endemism and richness, were mapped and integrated to identify regions important for biodiversity conservation along the Brazilian coast. Furthermore, we analyzed the effectiveness of the national system of protected areas to represent these regions. Analyses were performed on presence/absence data of 412 fish species in 0.25° latitudinal bands covering the entire Brazilian biogeographical province. Species richness, rarity and endemism patterns differed and strongly reflected biogeographical limits and regions. However, among the existing 154 latitudinal bands, 48 were recognized as conservation priorities by concomitantly harboring high estuarine fish species richness and assemblages of geographically rare species. Priority areas identified for all estuarine fish species largely differed from those identified for Brazilian endemics. Moreover, there was no significant correlation between the different aspects of the fish assemblages considered (i.e. species richness, endemism or rarity), suggesting that designating reserves based on a single variable may lead to large gaps in the overall protection of biodiversity. Our results further revealed that the existing system of protected areas is insufficient for representing the priority bands we identified. This highlights the urgent need for expanding the national network of protected areas to maintain estuarine ecosystems with high conservation value. [ABSTRACT FROM AUTHOR]

An important objective of fish ecology is to understand pure and shared effects of abiotic, biotic, and spatial predictors of fish assemblages' structure on continental shelves. This study aims to assess the structure of the bottom-associated fish assemblage on the shallow inner continental shelf of Paraná, southern Brazil, in response to physicochemical, biological, and spatial factors. We hypothesize that this structure is associated with the benthic megafauna, particularly with the distribution of the Brazilian seabob shrimp Xiphopenaeus kroyeri , an abundant fishing resource on the shallow coast of Paraná. We used uni and multivariate analyses to examine the distribution of abundance, richness, and composition of ichthyofauna in the region. Using variance partitioning analysis, we determined the pure and shared effect of spatial (latitude and longitude), physicochemical, and spatiotemporal distribution patterns of crustaceans, echinoderms, and mollusks as potential predictors of the structure of the fish assemblage. The data were obtained monthly from a one-year bottom trawl survey, comprising five transects and four depths (six, nine, 12 and 15 m) in a 60 km long section of the inner continental shelf, under the influence of estuaries. We captured 57578 demersal fish, comprising 37 families and 88 species. The average abundance of fish per haul was 387 individuals at a depth of 6 m, decreasing to 114 individuals per haul at 15 m. Average richness also decreased along the bathymetric profile, from 15 to 10 species per haul. Fish abundance and richness responded positively to a seasonal estuarine discharge pattern that was stronger in summer and autumn. High biomass of juvenile seabob shrimp in shallower regions also explained the higher abundances and richness. The results also suggest the existence of two fish assemblages in the region, associated with the distribution of the megafauna and segregated by depth, water surface transparency, and sediment particle size composition. Despite significant seasonal variations, controlled by precipitation and bottom water temperature, the structure of fish assemblages responded to the pure and shared effects of the three predictive components in all seasons. In particular, local coastal hydrography and the prey-predator relationship between fish and seabob shrimp were ecologically relevant processes for structuring fish assemblages at the inner continental shelf of Paraná. This study highlights the complexity of ecological interactions within demersal fish assemblages and the importance of considering biotic and abiotic factors in understanding fish distribution patterns at the spatial scale of inner continental shelves that are influenced by estuaries. [Display omitted] • Variance partitioning shows pure and shared effects of spatial, biotic, and abiotic predictors on fish assemblage structure. • Two fish assemblages segregated by depth, transparency, sediment size, and megabenthos at the inner continental shelf scale. • Coastal hydrography and prey-predator relationship are ecologically relevant for structuring fish assemblages. [ABSTRACT FROM AUTHOR]