Length-weight relationships of fish from sandy beaches

Abstract

This study estimated the length–weight relationships of 16 fish species occurring close to the shores of sandy beaches along the lower Negro River basin, Brazilian Amazon. The specimens were captured for one day each month, in October to November 2016, early in the morning and early evening, using trawl net (20 m 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 WT = a.LTb were estimated. The a values ranged from 0.0018 to 0.0226 and b values ranged from 2.5271 to 3.3244. This study also provides new data on of maximum lengths for six species, Amazonsprattus scintilla, Brycon pesu, Moenkhausia megalops, Pachyurus paucirastrus, Reganella depressa and Trachydoras microstomus, and new reports of the LWRs parameters of 15 fish species.

Length-weight relationship for Potamotrygon wallacei (Carvalho, Rosa and Araújo, 2016) caught in the middle Negro River, Barcelos, Brazilian Amazon

“…This difference can be explained, since the estimate available in FishBase is performed using the total length and based on all LWR estimates for species of similar body shape (Froese and Pauly, 2021;Froese et al, 2014). These differences were also indicated for teleost fish of the Negro River Basin (Olentino et al, 2023;Lubich et al, 2020Lubich et al, , 2021Olentino et al, 2021;Barros et al, 2018;Corrêa et al, 2016;Quara de Carvalho Santos et al, 2012). The studies by Duncan et al (2016) and Freire (2015), which provide information on the a and b parameters for P. wallacei, do not show the confidence intervals, and comparison is not possible, however the integer values were close.…”

“…The 95% confidence intervals (CI) were determined for parameters a and b (Froese, The Negro River Basin is the second largest sub-basin of the Amazon basin (Goulding et al, 2003) and possesses 1165 described fish species (Beltrão et al, 2019). Despite this high diversity, most of the work on length-weight ratios (LWR) focuses on Osteichthyes (Lubich et al, 2020(Lubich et al, , 2021Olentino et al, 2021Olentino et al, , 2023, though for freshwater stingrays this type of study is practically non-existent. Only one publication is known, which is for Potamotrygon falkneri Castex and Maciel (1963) that were caught in the Miranda River basin, in the state of Mato Grosso do Sul, Brazil (Vicentin et al, 2012).…”