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 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 relationship of 13 middle Uruguay River basin species,Southern Brazil

Length-weight relationship (LWRs) were determined for 13 fish species from the Uruguay River. The fish were caught in six locations and sampled at each location during each season, totaling 72 samplings, starting in May 2016 and ending in February 2018. Various materials were used such as gillnets (15; 20; 25 30; 40 and 80 mm, triple mesh 150.30.150 150.40.150 and 150.50.150 mm, 8 mm trawl). We also used two longlines, 100 m long, 30 hooks each (hooks 5/0 and 12/0), baited with small fish, corn and snail. Length-weight relationship were adjusted appropriately for all species (r² > .95). The b values of the LRW equations ranged from 2.38 in Steindachnerina brevipinna to 3.62 in Pimelodus atrobrunneus.     

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 four freshwater ornamental fish species from the Brazilian Negro River basin

The present work reports the length–weight relationships (LWR) for four ornamental fish species from the middle Negro River basin, Amazonas, Brazil. The r² value ranged from 0.810 to 0.941 and values of b varied from 2.346 to 3.442. These results represent the first reference on LWR for all four species, based on FishBase.     

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 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 relationship of 74 fish species caught in the continental coast of Ecuador

This work analysis the length-weight relationships for fish species captured by artisanal fishery along the continental coast of Ecuador. Fishermen used the following fishing gear: beach seine nets (5.1–31.8 mm), shrimp trawl nets (21.8–31.8 mm) and bottom gill nets (54.1–203.2 mm). Sampling took place during the years 2012 and 2014. Frequency of sampling was monthly, and it was completed systematically from Southern toward Northern Provinces. Length-weight relationship (LWR) was realized by the power model (y = a × x^b), for species with a bivariate dataset >70. A total of 59 commercial and 15 non-commercial species were registered. For 74 species, our analysis including a higher total length not reported in LWR estimates previously. The determination coefficient (r²) value was always above 0.95.     

Length-weight relationships of five fish species from Brazilian Amazon coast hotspot estuaries

The length-weight relationships (LWR) were estimated for five fish species from the Golfão Maranhense, Brazilian Amazon littoral region. Samplings were performed in August 2016, during the dry season, using trawl net with 6.0 m length by 3.0 m width (trawl mouth opening of 6.0 m²) and 1.0 cm mesh size between opposite knots. This study registers LWR for Anchoviella elongata and Gobioides broussonnetii and the estimated LWR for Aspredo aspredo and Aspredinichthys filamentosus covers a wider size range. Moreover, it is presented maximum length values for A. elongata and Sphoeroides greeleyi.     

Length-weight and length-length relationships of three fish species from the lower Yalong River,China

Length-weight relationships (LWRs) and length-length relationships (LLRs) were evaluated for three endemic fish species sampled from the lower Yalong River and its biggest tributary (the Anning River), in China. Specimens were captured using set gillnet (mesh size 4 cm) and backpack electro-fishing (power output 400 W, depth fished 1 m, area covered 3 m²) from June to July 2018. LWRs and LLRs are presented for the following species (Sinogastromyzon sichangensis, Micropercops swinhonis and Percocypris pingi).     

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 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 seven bycatch fish species caught along the Chennai coast,Bay of Bengal,Eastern Indian Ocean

Length-weight relationships (LWRs) were estimated for seven fish species captured as bycatch along the Chennai coast, Bay of Bengal, Eastern Indian Ocean. Fish samples were collected fortnightly between June-2018 to February-2019 from the commercial boats operating bottom trawl nets with a cod-end mesh size of 35mm. The total length (L) and the wet weight (W) to the nearest 0.1 cm and 0.01 g, respectively which is followed by regression analysis. The values of exponent (b) for LWRs varied from 2.5803 (Parachaeturichthys polynema) to 3.4432 (Ostorhinchus oxina). Similarly, a value varied between 0.0037 (Bleekeria kallolepis) and 0.0258 (Archamia bleekeri). As per FishBase, a new TLmax has been recorded for four species such as Ostorhinchus oxina, Jaydia striata, Bleekeria kallolepis and Cocotropus roseus.     

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 in seven ornamental freshwater species of Characiformes from the Unini River basin (Brazilian Amazon)

The aim of the current study was to address length‐weight relationships (LWRs) in seven ornamental fish species from the Unini River basin—the main tributary of lower Negro River (Brazilian Amazon). Specimens were seasonally sampled by using hand nets and beach seines (mesh size < 1 mm) in five different occasions (August 2009—December 2010). Preserved specimens (initially kept in 10% formalin and transferred to 70% ethanol 10 days later) were measured and weighted in laboratory. The LWR was calculated based on a log‐transformed linear regression. The maximum standard length of each species was different from the ones previously reported at Fishbase. In addition, b values were different from the ones reported for the four species whose data were available 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 for freshwater fish species from the Pantanal of the Negro River,Brazil

The present study describes the length‐weight relationships (LWRs) of 28 species captured in Santa Virgínia Bay, in the Pantanal of the Negro River, Mato Grosso do Sul State, Brazil, over 3 years (1999 to 2001). The study provides the first references on LWRs for thirteen of these 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 lower reaches of the Nujiang River and its tributaries in China

As one of the largest Southeast Asian rivers, flowing through China, Myanmar, and Thailand, the Nujiang (Salween) River contains a unique and rich diversity of fish species. In the present study, we investigated the length–weight relationships (LWRs) of four fish species (Pteronemacheilus meridionalis, Devario shanensis, Exostoma gaoligongense, and Glyptothorax granosus) collected from the lower reaches of the Nujiang River and its tributaries (24.175N~25.842N, 98.861E~98.903E), including the Mengboluo, Kungong, Luomingba and Laowo rivers in southwest China. Specimens were collected by using drift gill nets (100 m length × 1.5 m depth or 3 m depth, mesh-size: 1 cm-5 cm), cast nets (6.5 m, mouth opening: 35 × 45 cm², mesh-size: 4 mm) , and an electric shocker apparatus (12 V, 200 Hz) from different regions in the Nujiang River basin in September and October 2019 and June and September 2020. Before the collected fishes were placed in formalin, standard length (SL) and net weight (W) were measured respectively to the nearest 0.1 cm and 0.1g, respectively. Based on searches of the FishBase database and other relevant scientific literature, this study provides a new record of maximum size for P. meridionalis and LWRs for the four fish species.     

Length-weight relationships of 6 fish species caught in a Mediterranean lake (Trichonis-NW Greece)

In the present study the length–weight relationships (LWRs) of 6 fish species which are endemic to Western Greece, caught in the natural Lake Trichonis by experimental gillnets and electrofishing were estimated. Benthic (mesh size 5–55 mm; height 1.5 m; length 30 m) and pelagic (mesh size 6.25–55 mm; height 6 m; length 27.5 m) Nordic type multimesh gillnets were used seasonally, between February 2019 and November 2019, at different depth zones (0-57m). Electrofishing (80 Hz) conducted in the littoral zone of the lake during four samplings (2018, 2019). All the estimated LWRs were highly significant (p < .05) with high correlation coefficient (r² ≥ 0.962). The estimated b values ranged from 3.058 to 3.344. For five of the studied species (Trichonis spined loach (Cobitis trichonica Stephanidis 1974), Trichonis blenny (Salaria economidisi Kottelat 2004), Trichonis rudd (Scardinius acarnanicus Economidis 1991), Acheloos roach (Leucos panosi (Bogutskaya & Iliadou 2006)) , Hellenic minnowroach (Tropidophoxinellus hellenicus (Stephanidis 1971)) new maximum total body lengths (TL) were recorded, while for two species (T. hellenicus and L. panosi) LWRs are presented for the first time.