Tamanho da primeira maturação em espécies de interesse comercial na Bacia do Alto Paraguai – Mato Grosso : novos subsídios para o estabelecimento do tamanho mínimo de captura

Abstract

Fishing is an important economic activity, efficient management is fundamental for maintaining fish stocks, so identifying the size at which individuals start the reproductive process is fundamental for the management of these resources. Estimates for identifying first maturity size were made based on a database constructed from 2004 to 2019. To estimate L50 first maturity lengths, where at least 50% of individuals in the population have been through at least a reproductive cycle, and L100 where 100% of the individuals of the species are capable of reproduction, two methods were used: logistic regression, for those species in which the catches contemplated several length classes and, through the empirical model proposed by Froese and Binholan (2000), used for species where even with high N, there was no distribution of individuals in the adopted growth classes. Individuals of each species were grouped by class intervals of total length (5 cm). A total of 2826 specimens were sampled: 1374 specimens of Piaractus mesopotamicus; 652 individuals of Pseudoplatystoma corruscans; 221 specimens of Pseudoplatystoma reticulatum; 162 individuals of Pinirampus pirinampu; 156 of Prochilodus lineatus; 109 individuals of Salminus brasiliensis; 61 individuals of Hemisorubim plathyrynchus; 52 individuals from Zungaro jahu; 30 individuals of Brycon hilarii; 09 catches of Sorubim lime. The logistic model estimated L50 for Piaractus mesopotamicus at 34.4 cm while L100 was 43 cm, L50 for Pseudoplatystoma corruscans was 65.85, L100 80 cm, Pseudoplatystoma reticulatum was 62.2 cm while the L100 was 74 cm. The empirical model of Froese and Binohlan (2000) estimated the L50 and L100 of Pinirampus pirinampu; Prochilodus lineatus, Salminus brasiliensis, Hemisorubim platyhynchos, Brycon hilarii, Zungaro jahu, Sorubim lima, based on the largest specimen observed for the database species. According to the results found there is a tendency to reduce the size of individuals in the exploited populations, directly affecting the size of first maturation. Thus, in order to maintain the viable fishing stock, consideration should be given to revising the minimum catch size established for Piaractus mesopotamicus (Pacu), with a view to favoring effective reproduction as well as providing the gene flow of those individuals who reach longer body length.