Length–weight relationships for seven fish species from Marajó Bay,Amazon estuary,northern Brazil

Length–weight relationships (LWR) were estimated for seven fish species inhabiting the intertidal mudflats in the Marajó Bay, northern Brazil. A total of 514 specimens were collected quarterly between November 1994 and December 1995 using a beach seine (5 mm mesh size between opposite knots). Slope b of the LWR varied between 2.93 and 3.11, with a mean of 3.02. This study represents the first reference on LWRs for seven species and a new maximum length record for one of these species.     

Length‐weight relationship of 11 fish species from a tributary of the Amazon River system in northern Brazil

The length–weight relationships (LWRs) of 11 freshwater fish for eight families (Leporinus friderici, Pterophyllum scalare, Geophagus camopiensis, Curimata incompta, Astyanax bimaculatus, Tetragonopterus chalceus, Moenkhausia lepidura, Metynnis lippincottianus, Plagioscion squamosissimus, Hemiodus unimaculatus and Colomesus asellus) captured in tributary of the Amazon River system (Brazil) were investigated. These results represent the first reference on the LWRs for all 11 species in the eastern Amazon.     

Length‐weight and length‐length relationships of three tidepool fish species in the Amazon Coastal Zone of Brazil

Length‐weight relationships (LWR) and length‐length relationships (LLR) were analyzed for three species inhabiting tidepools in the Amazon Coastal Zone, two of them non‐native. Tidepools were sampled in five beaches along the Amazon Coastal Zone in 2011, and samplings were carried out using hand nets. The coefficients of allometry and proportionality were within the ranges estimated for fishes. All three species exhibited coefficients of allometry (b) higher than 3 in the LWR.     

Diel variation in fish assemblages in tidal creeks in southern Brazil.

Tidal creeks are strongly influenced by tides and are therefore exposed to large differences in salinity and depth daily. Here we compare fish assemblages in tidal creeks between day and night in two tidal creeks in southern Brazil. Monthly day and night, simultaneous collections were carried out in both creeks using fyke nets. Clupeiformes tended to be caught more during the day. Cathorops spixii, Genidens genidens and Rypticus randalli tended to be caught at night. Sciaenidae also tended to be caught more during the night. In general, pelagic species were diurnal, while deep water species were nocturnal. These trends are probably due to a variety of causes, such as phylogeny, predation and net avoidance.     

Length‐weight relationship of three cichlid species in a stream in southwestern Amazon,Brazil

The paper investigates the length‐weight relationship of three cichlids species for the southwestern Amazon, Acre state. The individuals were collected at five sites during one year among august/2016 and june/2017 in Quinoá stream (10°06′03.33″S/67°40′11.50″W). The individuals were collected using: seine net, 6 m length, 2.25 high, and mesh size 5 mm, two dip nets, 5 mm mesh, 30 cm width, and 50 cm in length and two sieve with 5 mm mesh, 50 cm width, and 80 cm in length. The results show that one species presented positive allometric growth (Aequidens tetramerus) and the others negative allometric growth (Apistogramma acrensis and Crenicichla semicincta).     

Weight‐length relationships of 12 fish species from the Pando tidal creek estuary (subsystem of the Río de la Plata,Uruguay)

Weight–length relationships are presented for 12 fish species from a subsystem of the Río de la Plata estuary in Uruguay. This study provides new maximum lengths for three species and a new reference for the weight–length relationship of one species.     

Length‐weight relationships of dominant fish species from Caxiuanã National Forest,Eastern Amazon,Brazil

The present work presents parameters of the length–weight relationships (LWR) for 12 species of freshwater fish from rivers within the Caxiuanã National Forest, Eastern Amazon. Data coverage include the main taxonomic groups in the sampling area: Characiformes: Acestrorhynchidae, Anostomidae, Curimaridae, Erythrinidae, Hemiodontidae; Siluriformes: Auchenipteridae; Perciformes: Sciaenidae. LWR parameters are estimated for the first time for five species: Leporinus affinis, Bryconops melanurus, Pygopristis denticulata, Serrasalmus gouldingi and Triportheus albus. Relative growth patterns were evenly distributed among species, one‐third showing negative allometry (b < 3; n = 4), isometry (b = 3; n = 4) or positive allometry (b > 3; n = 4).     

Length–weight relationships and length at first maturity for nine fish species of floodplain lakes in Central Amazon (Amazon Basin,Brazil)

Length–weight relationships are presented for nine fish species from the floodplain lakes in the Central Amazon (Amazon Basin, Brazil). The parameter slope b values in the length–weight relationships ranged from 2.33 to 3.28 for grouped sexes, and from 2.7 to 3.61 for separated sexes. Differences between sexes were verified in three species. Sizes at first sexual maturation ranged from 9.14 to 23.97. This study provides a new reference for the length–weight relationships of six species.     

Length‐weight relationships for five freshwater fish species from the Utinga State Park,Northeast Amazon,Brazil

Length–weight relationships (LWR) were estimated for five most abundant fish species occurring in the Utinga State Park within the metropolitan area of Belém, State of Pará, Northern Brazil. Data were obtained from specimens of Curimata knerii (n = 75), Gasteropelecus levis (n = 54), Hemigrammus rodwayi (n = 82), Hyphessobrycon bentosi (n = 69), and Pristobrycon calmoni (n = 76) collected in July 2013 with seines (1.5 mm mesh), sieves (1 mm mesh), and gill nets (40–120 mm mesh) in the main waterbodies. All LWRs are novel for science, increasing knowledge on biological information of the Neotropical freshwater fish.     

Length‐weight relationship and condition factor of 11 fish species of the Igarapé Fortaleza basin,a tributary from the Amazon River system in eastern Amazon (Brazil)

The present study investigated the length‐weight relationship (LWR) and allometric condition factor for 11 freshwater fish species of the Igarapé Fortaleza basin (00°02037.5″N; 51°06019.2″W), a tributary from the Amazon River system in the State of Amapá, northern Brazil. The fish were collected in the period from 2012 to 2014 using gillnets with different mesh sizes (10–40 mm between opposite knots). LWR parameters were estimated had angular coefficient (b) varying from 2.055 to 3.158. The allometric condition factor presented interspecific variation. These data complement the efforts to understand the biology of these Amazonian fish species.     

Length–weight and length–length relationships for 135 fish species from the Xingu River (Amazon Basin,Brazil)

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.     

Length‐weight relationship (LWR) of fish species in the Morato River,Paraná, Brazil

The length‐weight relationship (LWR) was evaluated in six fish species occurring in the Rio Morato, which is located in the east state of Paraná, Brazil, in well‐preserved areas of Atlantic Forest. The fishes were collected every 2 months from November/2016 to October/2017 and the fishing equipment used was consisted of dragnets, mesh sieves and gillnets. The specimens were weighed and measured in the laboratory. The mean growth coefficients obtained ranged from 2.5 to 3.2, confirming the range describe in the literature.     

Length-weight relationship of fish species from Central Amazon floodplain

Length-weight relationship (LWR) for 39 freshwater fish species captured in the Catalão Lake, a floodplain area at the confluence of the Amazonas and Negro rivers is presented. LWRs were calculated based on fish sampled over 18 years (1999–2017) using a set of ten gill nets with different mesh sizes, monthly immersed in water for 24-hr with 6-hr interval catches. Measurements were done for standard length (SL – 0.1 cm precision) and total weight (TW – 0.01 g precision). The LWRs were calculated by the linear regression of natural log-transformed SL and TW data: TW = a × SL^b. All statistical analyses were performed with R software. From all species considered, 32 are new LWR records for the international literature as well as for the Amazonian ichythyofauna; additional records expand the known size range for seven species.     

Selenium and mercury concentrations in some fish species of the Madeira River, Amazon Basin, Brazil

Samples of 7 species of piscivorous, omnivorous, and herbivorous fish caught at 12 different sites on the Madeira River, Amazon Basin, were analyzed for selenium and mercury. Selenium was determined by anodic stripping voltammetry and mercury by cold vapor atomic absorption spectrophotometry. The means for selenium concentrations ranged from 0.49 to 3.11 nmol/g and for mercury from 0.41 to 6.66 nmol/g depending on the fish species. The molar ratios of Hg:Se increased according to the fish trophic level. Piscivorous species had the highest mean ratio (4.0) and herbivorous species the lowest (0.9). There was a positive and statistically significant correlation between selenium and mercury concentrations for the herbivorous species (r = 0.716;p = 0.0088) not seen for omnivororus and piscivorous species (r = -0.2032;p = 0.3407). These findings are significant for the fish-eating population of the Madeira River because the ingestion of mercury would always be in excess of selenium.     

Length‐weight relationship of 21 fish species from Rio Doce River basin,Minas Gerais,Brazil

The present study provides the length‐weight relationship (LWR) for 21 fish species from eight rivers from Rio Doce River basin, Minas Gerais States, Brazil. Fishes were collected between August 1991 and September 2017, with gillnets, hand nets, cast nets and trawl nets. Standard length and total weight were measured for the LWR, which allometric coefficients b varied from 2.621 to 3.146.     

Length–weight relationships of six fish species from Tapajós River,Eastern Amazon,Brazil

The present study reports the length–weight relationships of six fish species from the Tapajós River: Curimata inornata, Geophagus altifrons, G. neambi, Pachyurus junki, Pseudoloricaria laeviuscula and Pristobrycon striolatus. No previous LWR information was available for these species in the FishBase database. Coefficients for the parameter b varied from 2.83 to 3.56.     

Two new species of Pseudancistrus (Siluriformes,Loricariidae) from the Amazon basin,northern Brazil

Two new species of Pseudancistrus, a genus diagnosed by non-evertible cheek plates and hypertrophied odontodes along the snout margin, are described from two drainages of the Brazilian Shield: Pseudancistrus kayabi from the rio Teles Pires (rio Tapajós basin) and Pseudancistrus asurini from the rio Xingu. The new species are distinguished from congeners (Pseudancistrus barbatus, Pseudancistrus corantijniensis, Pseudancistrus depressus, Pseudancistrus nigrescens, Pseudancistrus reus, and Pseudancistrus zawadzkii) by the coloration pattern. Pseudancistrus kayabi has dark bars on the dorsal and caudal fins which are similar to that of Pseudancistrus reus from the Caroní River, Venezuela. Pseudancistrus asurini is unique among Pseudancistrus in having whitish tips of the dorsal and caudal fins in juveniles to medium-sized adults.     

Influence of moon phase on fish assemblages in estuarine mangrove tidal creeks

Significant differences in the composition of fish assemblages during different moon phases were detected in mangrove tidal creeks of the Goiana Estuary. The numbers of Zabaleta anchovy Anchovia clupeoides, Tarpon snook Centropomus pectinatus and Guavina Guavina guavina as well as at least 15 other species showed significant changes according to moon phase and were higher in terms of individuals (32%) and mass (34%) during the new moon.     

Length–weight relationship for seven freshwater fish species from Brazil

The present study reports length‐weight relationships for seven native freshwater fish species (Triportheus angulatus, Psectrogaster rhomboides, Prochilodus brevis, Leporinus piau, Cichlasoma orientale, Crenicichla menezesi, and Pimelodella gracilis) captured in a semiarid Brazilian reservoir located in the state of Rio Grande do Norte.     

Length–weight and length–length relationships of 16 fish species from Amapá, Brazilian Amazon

The present study provides length‐weight (LWR) and total length‐standard length (LLR) relationships for 16 freshwater fish species collected in coastal rivers of the northern Brazilian, state of Amapá in 2015. Fishes were caught in heterogenic environments like ponds, stream and river channel with sieve and trawl. As result, we present novel information of LWR and LLR for 11 and 15 species, respectively. Maximum values (first values or new maximum values) of TL, SL and WT are presented for 14, 12 and 15 species, respectively.