Summary Length–weight (LWR) and length–length relationships (LLR) are presented for 135 freshwater fish species sampled by several types of fishing gear between April 2012 and July 2014 in the middle and lower Xingu River Basin, northern Brazil. The report represents the first references on LWRs and LLRs for 114 and 119 species, respectively, and also provides a new maximum size for 96 species.

The aim of this study of tidepool fishes was analyse variation in their use of intertidal habitats (rocky shore, mangrove and salt marsh). Specimens were collected during wet and dry periods from 18 tidepools in the three habitats. A total of 7690 specimens, belonging to 19 families and 30 species, was captured. The fish assemblage in rocky shore pools was clearly distinct from that of vegetated habitats (mangrove and salt marshes). The rocky shore fauna was dominated by permanent resident species, whereas pools in mangrove and salt marsh habitats were inhabited primarily by opportunistic and transient species. Habitat segregation by ontogenetic stage (e.g. smaller individuals in mangroves, intermediate size classes in salt marsh and sub-adults/adults on rocky shores) indicates age-related migration in response to the physical structure of these habitats and to the natural history of each fish species. These findings are important for the development of effective conservation and management plans for intertidal fishes.

Length-length (LLR) and length-weight (LWR) relationships are presented for 19 fish species collected between 2009 and 2011 in small tributaries and headwaters areas of the Tocantins-Araguaia basin, Itacaiúnas drainage, Southwestern Pará, Amazonian, Brazil. This study describes the first reference of LLR for 13 species and LWR for 16 fish species.

The relationships between fish size and sagitta otolith measurements were calculated for the first time for 15 species belonging to six families from the northern Brazilian coast. A total of 220 fish were sampled from the bycatch landed by the bottom-trawl industrial shrimp-fishing fleet between August and September 2016. All species had strong relationships between otolith measurements and fish total length with the coefficient of determination (r 2) ranging between 0.71 and 0.99. The variable most strongly related to fish total length was found to be the sagittal otolith length (OL) with 98% of the variability. These relationships are a useful tool to estimate length and mass of preyed fish from otoliths found in stomach contents of marine predators.

Relações comprimento-peso e comprimento-comprimento para os peixes de poças de maré na costa brasileiraResumo: Cinquenta e nove relações peso-comprimento (RRC) e comprimento-comprimento (RCC) foram estimadas para 18 espécies de peixes, distribuídos em 10 famílias. Os espécimes de peixes foram capturados em poças de maré de 21 locais amostrados, ao longo de um trecho de 4.900 km da costa brasileira, entre as latitudes 00° e 22°S, durante o ano de 2012. Este estudo apresenta a primeira referência disponível para 5