Length-weight relationship of 16 fish species from the Negro River basin (Amazonas state,Brazil)

This study aimed to estimate the parameters of length-weight relationship for 16 freshwater fish species that inhabit the Aracá and Demeni Rivers, which are two tributaries of the Negro River (Amazonas state, Brazil). The fishes were sampled using gillnets (15 × 2 m, mesh size 30–120 mm between opposite knots), during 6 days each year, in April 2016, November 2018 and April 2019. The gillnets were placed in the river twice each day; in the morning (5–9 a.m.) and in the evening (5–9 p.m.), with a standardized time of 4 hr. Measurements were taken for standard length (SL – 0.1 cm precision) and total weight (TW – 0.01 g precision). The parameters a and b of the equation W_T = a.L_T^b were estimated. This study also provides new data on of maximum lengths for six species, namely, Argonectes longiceps, Hemiodus atranalis, Chalceus erythrurus, Astrodoras asterifrons, Trachydoras steindachneri and Acarichthys heckelii.     

Length-weight relationships of eleven fish species captured in 18 streams of the Capim River basin,Brazil

The length-weight relationship is important for the study of populational dynamics. This study aimed to describe the length-weight relationships (LWR) of 11 fish species sampled on 18 streams of the Capim river basin on eastern Amazon. Specimens were captured in 2014, 2015 and 2017, using sieve nets with 2 mm of mesh size. Fixed specimens were fixed in 10% formalin and conserved in alcohol 70%, measured for standard length (SL, 0.1 cm) and total weight (W, 0.01 g). The 11 species analysed were: Hemigrammus bellottii, Hemigrammus ocellifer, Hyphessobrycon heterorhabdus, Iguanodectes rachovii, Copella arnoldi, Nannostomus trifasciatus, Apistogramma regani, Apistogramma agassizii, Gymnorhamphichthys rondoni, Hypopygus lepturus, Anablepsoides urophthalmus.     

Length-weight relationship of 12 species of freshwater fish caught in the middle and lower stretches of the Negro River basin,Brazilian Amazon

This study aimed to estimate the parameters of the length-weight relationship for 12 freshwater fish species that inhabit lakes in the Negro River basin (Amazonas state, Brazil). The fishes were sampled using gillnets (15 × 2 m, mesh size 30–100 mm between knots), during the hydrologic cycle: low water (dry), flooding, high water (flood), and receding water, from 2008 to 2010, 2012 and 2013. The gillnets were placed in the lakes with a standardized period of 24 hr, with fish removal occurring every 12 hr (2010 to 2010) and 6 hr (2012 and 2013). Measurements were taken for standard length (SL – 0.1 cm precision) and total weight (TW – 0.1 g precision). The parameters a and b of the equation WT = a.LT^b were estimated. This study also provides new data on of maximum lengths for three species.     

Two new species of Heptapterus (Siluriformes: Heptapteridae) from the Uruguay River basin,Brazil

As part of an ongoing taxonomic revision of the genus Heptapterus from the Laguna dos Patos and Uruguay River drainages and Atlantic coastal streams of southern Brazil and Uruguay, two new species closely related to Heptapterus mustelinus were identified. Both species are endemic to small tributaries of the Uruguay River. The two new species are distinguished from each other and from other species of Heptapterus by arrangement of cephalic and trunk laterosensory systems, number of vertebrae and number of dorsal, pectoral and anal-fin rays. Phylogenetic analyses of mitochondrial DNA (coI and cytb) sequence data further supports distinctiveness of the two new species.     

Length-weight relationships of seven fish species from the laguna del cisne basin (Canelones,Uruguay)

This work provides new length-weight information for seven species of freshwater fishes. The analyzed specimens were collected monthly during a year (April 2018–March 2019) in a coastal lagoon system and its associated streams in southern Uruguay. During each sampling campaign, fishes were captured using gillnets in the lagoon and electrofishing in the streams. This study reports a new maximum size for four species and the first length-weight relationship report for Gymnogeophagus terrapurpura. Length-weight estimates and their confidence intervals are provided for all species.     

Length-weight relationship of six small fish species from the Negro River basin in the Brazilian Amazon

The main objective of the study was to estimate the parameters of the length-weight relationship for six small fish species of lower Negro River basin. The fish were sampled using monofilament gillnets (20 × 2 m, mesh size 5 mm between knots), and landing net for 2 days of each month in September and December 2017 and February, March and April 2018. The gillnets were placed in the river twice a day, in the morning (9–11 a.m.) and the afternoon (3–5 p.m.). Total length and total weight were measured to a precision of 0.1 cm and 0.01 g, respectively. The parameters a and b of the equation WT = a.LT^b were estimated.     

Length-weight relationships of 37 freshwater fish species from the Lefini river,middle Congo River basin (Republic of the Congo)

The present study reports on length-weight relationships (LWRs) for 37 of the most abundant fish species in the Lefini River basin, one of the largest right bank tributaries of the Congo River in the Republic of the Congo. The study area comprised 12 stations along 103 km of the river. Each station was sampled during March 2007 to August 2008 following standardized methods utilizing five monofilament gill nets of 10, 12, 15, 20 and 30 mm mesh size. Sample size, lengths, weights, LWRs, 95% confidence intervals of a and b, coefficient of correlation r² and growth type are provided for each species. Values of allometric coefficient b of the LWRs (W = aSL^b) ranged from 2.556 for Synodontis nigriventris to 3.363 for Brycinus poptae. These results represent the first study of length-weight relationships for fish species in a large affluent of the Congo basin as a whole.     

Length-weight relationships of fish species from the Stung Russei Chrum River basin,Kingdom of Cambodia

This study evaluated the length-weight relationships (LWRs) for three teleost fish species sampled from the Stung Russei Chrum River basin, Kingdom of Cambodia. The fish were collected during two dry seasons (April 2019 and November 2019) and one rainy season (October 2018) using monofilament trammel nets (2–12 cm mesh size), cast net (mesh size 2 cm) and scoop-nets (mesh size with 0.3 cm). Results showed that all fitted regressions were highly significant and the coefficients of determination (r²) were high. This study expanded the value of maximum total length for Cyclocheilichthys apogon and Poropuntius laoensis while reported the wider ranges of total mass for Poropuntius laoensis. Moreover, our present study also provided the novel LWRs records for Hemibagrus filamemtus.     

Length–weight relationship of six freshwater fish species in upper‐middle Tocantins River basin (Brazil)

Length–weight relationships (LWRs) were analyzed for six abundant fish species in the upper‐middle Tocantins River, northeastern Brazil. Analyses included data from 486 specimens sampled in five expeditions between August 2013 and May 2015 by gillnets. New maximum values of total lengths for the literature and FishBase were presented for six species, as well as first time estimates of LWR for Galeocharax gulo, Curimata acutirostris and Aphanotorulus emarginatus.     

Length–weight relationships of fish species caught in the Upper Uruguay River, Brazil

Length–weight relationships were estimated for 56 species, representing seven orders and 17 families of fishes from the Upper Uruguay River, Brazil. For most of these species, no length–weight relationships were previously available.     

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 relationship of fish species captured around an artificial offshore reef (northern Rio de Janeiro,Brazil)

The present work provides length-weight relationships (LWRs) for fish species captured around artificial offshore reef deployed 5 km from Guaxindiba Port, northern Rio de Janeiro, Brazil. The fish were captured during two sampling periods each year between 1996 and 2017 using bottom gill nets (25 m_length × 3 m_depth; 30 mm mesh). The fish were kept on ice and the biometric data, including total length (cm) and total wet weight (g) were determined in the laboratory. A total of 16 species belonging to 10 families were analyzed with Sciaenidae being the species richest family (5 spp) in the samples. The new value of LWRs for Sphyraena guachancho and new maximum sizes recorded for seven species highlight the scarcity of information on biological aspects of South America coastal fishes. These LWRs should assist fisheries scientist and managers to complement their further studies of population parameters to improve management decisions.     

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.     

Length–weight relationship of 10 freshwater fish species in Amazonian streams,Trombetas River basin (Brazil)

Length–weight relationships (LWR) were analyzed for 10 fish species from 26 Amazonian streams located in four micro‐basins in the Trombetas River basin, Pará State, Brazil. LWRs were calculated based on 1831 individuals sampled between 2010 and 2012 using a manual trawl. The coefficients of proportionality and allometry were within the ranges estimated for most fishes. No previous LWR information was available for these species in the literature.     

Length-weight relationships of four fish species from the Yalong River,China

Parameters of the length-weight relationship (LWR) were estimated for four fish species [Beaufortia szechuanensis (Fang, 1930), Claea dabryi (Sauvage, 1874), Percocypris pingi (Tchang, 1930), and Yunnanilus sichuanensis Ding, 1995] from the Yalong River. Samples were collected seasonally from June 2018 to July 2019, using various fishing gears [set nets (mesh: 1.5 × 2.0 cm), hook, drift gill nets (three mesh sizes: 1.0; 2.0; 3.0 cm) and electro fishing]. Two new maximum standard length were recorded for C. dabryi and P. pingi.     

Length‐weight relationships of seven fish species from Jequitinhonha River basin,southeastern Brazil

The present study established the length‐weight relationships (LWR) for seven fish species from Jequitinhonha River basin, a Brazilian coastal drainage, collected with gillnets (3 to 16 cm) between 2011 and 2016. For the LWR, standard length and total weight were used. The allometric coefficient b varied from 2.66 to 3.26. These results provide biological data for a region of extreme biogeographical importance that is suffering serious environmental disturbances.     

A new species of Centromochlus (Siluriformes,Auchenipteridae, Centromochlinae) from the middle Rio Tocantins basin,Brazil

A new species of the catfish genus Centromochlus (Auchenipteridae, Centromochlinae) is described. The new species is diagnosed by having numerous dark rounded blotches over the body and fins, dorsal‐fin spine with serrations anteriorly and smooth posteriorly, anal fin of mature males with three unbranched and seven branched rays, anterior nuchal plate absent and posterior nuchal plate not extended ventrally. The new species is described from a small stream in the Estação Ecológica Serra Geral de Tocantins, a natural reserve in the centre of the Brazilian Cerrado, close to the watershed between the Rio Tocantins and the Rio São Francisco basins. The new species is possibly the sister taxon to the recently described Centromochlus meridionalis from the upper Rio Tapajós. Those two species share with Centromochlus perugiae, from the upper Amazon and upper Paraguay, derived features associated with the modified anal fin in sexually mature males.     

Length-weight relationships of fish species from oxbow lakes on the floodplain of the middle Purus River in western Brazilian Amazon

The length-weight relationship (LWRs) was estimated for eight fish species collected from oxbow lakes on the floodplain of the middle Purus River in western Brazilian Amazonia in January, May, and September 2012. The specimens were collected using 12 gillnets (80 m in length × 4 m in height, meshes of between 1.5 cm and 12.0 cm), which were set during both diurnal and nocturnal periods. The species had allometric coefficients (b) of between 2.92 and 3.37, and correlation coefficients (r²) ranging from 0.954 to 0.993 and we highlight that the work presents new data for literature.     

Length-weight relationships of six fish species from the Xiangjiang River in Guangxi region,China

This study aimed to estimate the parameters of length-weight relationships (LWRs) for six freshwater fish species that inhabit in the Xiangjiang River of Guangxi region, China. The specimens were sampled in April, July, and October 2014 and in January 2015 using electrofishing (CWB-2000P, China; 12 V import, 250 V export) and traps (mesh size 8.5 mm; length 200 m) at five sampling sites. For each sampling site, a trap was settled on one nearshore zone of the river for 24 hr, and the electrofishing was applied within 30 min from downstream to upstream with 200 m long. Standard length was measured (be accurate to 0.1 cm) and total weight determined (be accurate to 0.1 g) after preservation in formaldehyde (10%). The values for the parameter b of the length-weight relationships were estimated together with the coefficient of determination scores. In addition, this study provides a new tentative LWRs for the six species.     

Length-weight relationship of six coastal fish species from Gulf of Mannar,South-east coast of India

The parameters ‘a’ and ‘b’ of length weight relationship of 6 species (Scolopsis vosmeri (Bloch, 1792), Engyprosopon macrolepis (Regan, 1908), Bleekeria murtii Joshi, Zacharia&Kanthan, 2012), Centriscus scutatus Linnaeus, 1758, Samaris cristatus Gray, 1831 and Iniistius bimaculatus Ruppell, 1829) are reported from the Gulf of Mannar, South east coast of India. The fish samples were collected from experimental trawling conducted twice a month during the period August to December 2012 and September to December 2013 at a depth ranging from 8.5 to 20.5 m. Three hauls were made in a day with each haul of one hour duration. The total length of the gear was 32 m with a cod end mesh size of 30 mm. The total length of the fish was measured to the nearest 0.1 cm and weight to the nearest 0.1 g.