Calculating growth parameters of Genidens barbus (Siluriformes, Ariidae) using length composition and age data

Abstract

The marine catfish Genidens barbus was once one of the most important estuarine fishery resources in the Patos Lagoon (southern Brazil), which had the largest population known for the species. However, clear signs of overfishing have been observed since the 1980s. Growth parameters for this population were estimated by combining length frequency data for juveniles and selected published data on annuli reading from adult otoliths. This methodology yielded a more realistic set of parameters using both the specialized and generalized von Bertalanffy growth model. The species growth can be described as:The growth performance index u¢ was estimated as 2.78 for the special (classical) model. Stock rebuilding is expected to be slow, as the species is slow-growing, has a low natural mortality rate, and mouthbreeds a small amount of large eggs. ResumoO bagre marinho Genidens barbus foi um dos recursos pesqueiros mais importantes no estua´rio da Lagoa dos Patos (RS, Brasil), sendo esta a maior populac¸a˜o conhecida da espe´cie. A partir dos anos oitenta, no entanto, comec¸ou a mostrar claros sinais de sobrexplorac¸a˜o. Os paraˆmetros de crescimento desta populac¸a˜o foram calculados utilizando dados de frequ¨eˆncia de comprimento dos juvenis e leitura de ane´is de crescimento em oto´litos dos adultos. A metodologia utilizada para determinar os paraˆmetros de crescimento neste trabalho mostrou resultados mais realistas que os previamente calculados, tanto quanto utilizados o modelo especial quanto o generalizado de von Bertalanffy. O crescimento desta espe´cie pode ser descrito por L t ¼ 118.6[1 ) e )0.043(t+1.505) ] ou L t ¼ 104.6[1 ) e )0.137D(t+4.013) ] 1/D com um fator de superfı´cie D ¼ 0.542. O paraˆmetro u¢ foi calculado em 2.78 para o modelo especial (cla´ssico). Presume-se que a recuperac¸a˜o deste estoque pesqueiro seja demorada ja´que a espe´cie apresenta crescimento lento, mortalidade natural baixa e tem baixa fecundidade.

Isotopic niche of the catfishes Bagre bagre and Genidens barbus in a coastal area of south-eastern Brazil

“…The catfishes B. bagre and G. barbus are targets of commercial gillnet fisheries practised between 21º35'S and 22º00'S, from less than one to 10 nautical miles from shore, in depths varying from 10 to 30 m. The specimens captured in these fisheries are classified as adults according to its total length: the asymptotic or maximum length recorded for B. bagre is 55.0 cm (Marceniuk et al 2015), while for G. barbus it is 120 cm, with the first maturity reached around 40.0 cm (Velasco et al 2007, Froese & Pauly 2018.…”

Mixed-Effects Modelling of Scale Growth Profiles Predicts the Occurrence of Early and Late Fish Migrants

“…More commonly, researchers are limited to inferring growth from changes in the average size at successive ages or time events [29]–[31], often based on different individuals. Growth is then analyzed using models based in the Von Bertalanffy [32] approximation [33]–[35], but this ignores individual variation in growth trajectories [36] and assumes that age is accurately measured [37], something that is not always possible.…”

Taxocenose de bagres marinhos (Siluriformes, Ariidae) da região estuarina de São Vicente, SP, Brasil

“…barbus) (Reis 1986). O cuidado com a prole, aliado às baixas fecundidades, podem levar a uma reposição lenta dos estoques (Velasco et al 2007).…”