Estimating size at first maturity (L50) from Gonadossomatic Index (GSI) data

• Autor(a) principal: Fontoura,Nelson F.
• Data de Publicação: 2009
• Outros Autores: Braun,Aloísio S., Milani,Paulo Cesar C.
• Tipo de documento: Artigo
• Idioma: eng
• Título da fonte: Neotropical ichthyology (Online)
• Texto Completo: http://old.scielo.br/scielo.php?script=sci_arttext&pid=S1679-62252009000200013
• topic: Fish; Reproduction; Patos lagoon; Logistic function

Correct estimates of size at first maturity (L50) are useful for fish stock management and different methods have been proposed. In this study we propose the use of a modified logistic to estimate L50, including a variable asymptote (A). We also test the use of the Gonadossomatic Index (GSI) as a flag to establish the reproductive status of each female fish. The method is demonstrated using GSI data for four Neotropical fish species: Characiformes: Astyanax fasciatus (n = 473) and Oligosarcus robustus (n = 297); Siluriformes: Loricariichthys anus (n = 427) and Trachelyopterus lucenai (n = 195). The results were stable enough to propose this method be used for other fish species with different life histories and with a relatively unconstrained sampling programs. Nevertheless, a wide scale test program is desirable to identify any possible bias in this approach.