Diet of characin,Brycon falcatus (Muller and Troschel, 1844) in the Amazon Basin: a case study on an attractant for fish in the Teles Pires River

The use of fresh soybeans as an attractant in fishing has been altering the diet of the characiform Brycon falcatus, which are thriving at fishing spots. This has subsequently affected the amount of abdominal fat in the species from the Tapajós River basin, Southern Amazon. In the Teles Pires River basin region, one of the most common capture techniques employed by fishermen is the use of attractant feeds (soybeans, corn, cassava) at certain locations to attract mostly omnivorous fish. Tourists also feed fish chips and breadcrumbs. In the experimental design, rivers were mapped according to attractant availability to develop an attractant‐density classification system comprising four rivers with different attractant densities (low, medium, and high), plus a river serving as control (no attractants). Monthly collections were carried out during the 2012 and 2013 dry seasons. For diet analyses, methods of frequency of occurrence and relative volume were used to calculate the feeding index (IAi) of 97 specimens. For analyses of abdominal fat, an index was calculated by dividing the wet weight of the abdominal fat by the total wet weight of each individual. Standard length ranged from 15.0 to 48.5 cm, and weight between 0.18 and 4.40 kg. Composition and diversity of diet items changed with the increasing density of attractants. In the river with a high attractant density, fresh soybeans and corn were dominant diet items; in the control river, the diet was natural (e.g. seeds, fruits, leaves, and insects) and therefore similar to those described for B. falcatus in undisturbed environments. Fish collected from rivers with high attractant densities were in better condition than those from the river with no attractants. Although use of attractants is prohibited by State legislation, there are no inspections. This study clearly shows an alteration in the natural diet and abdominal fat of B. falcatus resulting from an imbalanced, high‐calorie feed via an attractant. It is recommended that these areas be monitored for the preservation of B. falcatus.     

Knodus dorsomaculatus (Characiformes: Characidae), a new species from Teles Pires River,Tapajós River basin,Brazil

Knodus dorsomaculatus, a new species, is described from Teles Pires River, a tributary of the Tapajós River, Brazil. It can be distinguished from its congeners by the presence of a conspicuous dark blotch on the base of the first five branched dorsal fin rays and the presence of ii,9 dorsal fin rays. Additional comparisons between K. dorsomaculatus and its congeners are presented.     

Length–weight relationship of Rhinobatos horkelii Müller & Henle, 1841 and Zapteryx brevirostris (Müller & Henle, 1841) off Brazil,southwestern Atlantic Ocean

This study reports the length–weight relationships (LWRs) for two elasmobranch species, Rhinobatos horkelii Müller & Henle, 1841 and Zapteryx brevirostris (Müller & Henle, 1841) collected from the southwestern Atlantic, off Brazil. Both are considered endangered species. The LWR data can be taken into consideration for further management and conservation plans.     

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.     

Length–weight relationships for seven fish species of the Napo River,Upper Amazon,Peru

Length–weight relationships (LWR) were estimated for seven fish species from the Napo River and its main tributaries, Arabela and Curaray rivers, Amazon basin, Peru. A total of 652 specimens were sampled between 2012 and 2014 using seines and gillnets. This study reports new maximum total length for four species and new LWR and maximum total weight records for three and five species, respectively.     

Length–weight relationship and seasonal condition in Capoeta sieboldii in the upper Çoruh River,Turkey

Seasonal variations in Fulton’s condition factor (K) and the length–weight relationship (LWR) were investigated for Capoeta sieboldii in the upper Çoruh River (Turkey) from March 2000 to February 2001. There was a slight seasonal variation in condition, with generally lower values in summer and winter, and higher values in autumn. LWR was calculated as W = 0.016 × L^2.933, W = 0.014 ×L^3.001, and W = 0.009 × L^3.118 for males, females, and juveniles, respectively.     

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 relationship and condition factor of Lepidocephalichthys goalparensis Pillai and Yazdani, 1976 in Assam,India

The present study describes the length–weight relationship (LWR), condition factor (K) and size at first maturity of a cobitid loach, Lepidocephalichthys goalparensis Pillai and Yazdani, 1976 of the family Cobitidae in Assam, India. A total of 716 specimens (males = 324, females = 392) ranging from 3.06 to 7.01 cm total length (TL) and 0.17–2.27 g body weight (BW) were analyzed. The overall value of the allometric coefficient b for the LWR indicated negative allometric growth (<3.00) for both males (2.774) and females (2.993). The size at first maturity (TL₅₀) for female L. goalparensis was estimated to be 5.6 cm TL. The condition factor values ranged from 0.56 to 1.35 in mature females. This is the first time that the biological parameters have been studied in this species.     

Length–weight relationship of three fish species from the Qiantang River,China

Length–weight relationships (LWRs) of the three fish species, Pseudobagrus albomarginatus(Rendahl, 1928), Pseudobagrus crassilabris (Günther, 1864), and Rhinogobius davidi(Sauvage & Dabry de Thiersant, 1874), were determined respectively. Samples were collected from Qiantang River, China during March 2016–December 2017. The bvalues ranged from 2.525 to 2.917, the coefficient of determination (r²) ranged from 0.96 to 0.97. Prior to this study, the length–weight relationship for P. albomarginatus and R. davidi were unknown to FishBase and the new maximum total lengths for three species were not recorded in FishBase. These results are useful for the fishery research and management in Qiantang River.     

Length–weight relationships of fish from Madeira River,Brazilian Amazon,before the construction of hydropower plants

Length–weight relationships (LWRs) are presented for 112 freshwater fish species representing 23 families and five orders captured in the Madeira River, the largest white‐water river tributary of the Amazon River. The allometry coefficient (b) of the LWR (Wt = aSL^b) ranged from 2.446 to 3.856 with a median value of 3.102. Eight new LWR records are presented for Amazonian species as information for FishBase. LWRs in the present study provide historical data on a and b coefficients prior to the damming of the Madeira River in November 2011, allowing comparison estimates of predicted future population parameters as influenced by human intervention.     

Length‐weight relationship and relative condition factor of five indigenous fish species from Torsa River,West Bengal,India

Length‐weight relationships (LWRs) for five indigenous fish species under five genera and two families, namely Cyprinion semiplotum (McClelland, 1839), Barilius barna (Hamilton, 1822), Barilius barila (Hamilton, 1822), Gagata sexualis Tilak, 1970 and Pseudolaguvia shawi (Hora, 1921) were studied from Torsa River in West Bengal, India. Sampling was done at quarterly intervals from November, 2015 to December, 2016 and a total of 701 fish specimens were collected using cast nets (mesh size of 15–20 mm), gill nets (mesh size 20–35 mm) and bamboo traps. In the present study, b value ranges from 2.686 to 3.268. LWRs for these fish species (except P. shawi) have not been reported in FishBase. A new maximum length has been recorded for P. Shawi and G. sexualis. The relative condition factor (Kn) values was found to range from 1.004 to 1.028.     

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 relationships for 14 fish species of the Suer River estuary in southern Korea

Length–weight relationships were estimated for 14 species belonging to 13 fish families from the Suer River estuary, Korea. These 14 species are: Callionymus valenciennei, Konosirus punctatus, Conger myriaster, Cynoglossus joyneri, Tribolodon hakonensis, Thryssa hamiltonii, Acanthogobius flavimanus, Paratrypauchen microcephalus, Hexagrammos agrammus, Nuchequula nuchalis, Pseudopleuronectes yokohamae, Pennahia argentata, Sillago japonica and Takifugu niphobles. Between April 2009 and January 2010, samples were caught by commercial trawl net at depths of <20 m. Estimates for parameter b of the length–weight relationship (W = aL^b) ranged between 2.510 and 3.149.     

Length–weight relationships for 19 headwater fish species from streams in the Sinos River basin,southern Brazil

This study reports the length–weight relationship estimates (LWRs) for 19 fish species inhabiting low order headwater streams in the Sinos River basin of southern Brazil. Between 2010 and 2014, 19 species at 47 sites were sampled in 10 sub‐basins by electrofishing in winter and summer. For two species, Bryconamericus iheringii and Phalloceros caudimaculatus, the estimates in this study offer new maximum size ranges compared to previous studies.     

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 relationship of 37 fish species from the Taquari River (Paranapanema Basin,Brazil)

This work describes the length–weight relationship (LWR) of 37 fish species from the Taquari River, one of the tributaries of the Jurumirim Reservoir in the high Paranapanema Basin, São Paulo, Brazil. Information was not yet available in FishBase on LWRs of 22 of the fish species and maximum weights (Wt) of 24 of the fish species. New maximum standard lengths are presented for nine species as well as weights for two fish species.     

Length–weight relationships of 21 fishes from the Xiangjiang River,China

This paper provides the length–weight relationships for 21 fish species belonging to four families and 19 genera from the Xiangjiang River, a tributary of the middle Yangtze River in China. Among them, the length–weight relationships for 14 fishes are first‐time reports for FishBase, and new maximum total lengths of 13 fishes are also reported.     

Length–weight relationships of some fish from the Ganga River,India

Length–weight relationships (LWRs) were determined for seven riverine fish species from the river Ganga, India. Specimens were collected on a bi‐monthly basis from April 2017 to December 2018 using gill nets (mesh size 22–34 mm), cast nets (mesh size 16 mm) and bag nets (mesh size 14–22 mm). Total length was measured to the nearest 0.1 cm using a digital caliper and weight was recorded to the nearest 0.01 g on an electronic balance. From estimated length–weight relationships, the values for parameter “a” ranged from 0.004 (Bregmaceros mcclellandi and Setipinna tenuifilis) to 0.014 (Brachirus pan). Likewise, the values for the parameter “b” of the equation ranged from 2.958 (Bagarius bagarius) to 3.124 (Bregmaceros mcclellandi) and r² from 0.978 (Gonialosa manmina) to 0.996 (Brachirus pan).