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Summary This study provides separate length–weight relationships (LWRs) for males, females and pooled individuals for four stingray species (Dasyatis guttata, Dasyatis marianae, Gymnura micrura, and Rhinoptera bonasus) found in the tropical Atlantic. The specimens were sampled monthly between April 2009 and February 2011 along the coast of Alagoas, northeastern Brazil, using different fishing gear. For three species, the LWR parameters are reported for the first time, including D. marianae, an endemic species.

Background. Assessing patterns in habitat utilization and changes in the composition of biont assemblages is a key tool for efficient ecosystem conservation planning and management. Nevertheless, habitat use patterns by juvenile fish still need more comprehension. Therefore, the presently reported study investigated relations between the type of nursery ground and the structure of juvenile fish assemblages in a tropical coastal area of the south-western Atlantic. Materials and methods. From December 2009 to November 2010, we conducted monthly sampling of ichthyofauna in two habitat types (mangrove and sandy beach) used as nursery grounds by juvenile fish of the south-western Atlantic. Species richness and abundance were used to identify spatial and temporal patterns in the distribution of fish assemblages throughout habitats' dynamics. Results. A total of 845 fishes representing 16 families and 34 species were found during the presently reported study: Albula vulpes (Linnaeus, 1758); Atherinella brasiliensis (Quoy et Gaimard, 1825) Ginsburg, 1933; Sphyraena barracuda (Edwards, 1771); Sphoeroides testudineus (Linnaeus, 1758). No significant differences in species richness and total abundance were found between habitats and seasons. Nevertheless, our analyses showed that distinct sets of species use these areas. Moreover, we identified a strong relation between the rainfall and the species turnover in both habitats studied. Conclusion. Diversity of nursery grounds in coastal areas not only increases fish diversity but also plays an important role in the sustaining fish stocks.

Summary Length‐weight relationships were estimated for two mugilid species from estuarine systems in Alagoas, northeastern Brazil. Fish were sampled monthly using nylon monofilament gillnets with different mesh sizes during two fishery surveys. The first LWR reference for Mugil curvidens and new maximum lengths for both M. rubioculus and M. curvidens are provided.

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