Population dynamics of Pseudoplatystoma metaense Buitrago-Suárez & Burr, 2007 (Pisces, Siluriformes: Pimelodidae) from the northwestern Orinoco River Basin

The Matafraile catfish (Pseudoplatystoma metaense Buitrago-Suárez& Burr, 2007) is the second most important com­mercial species in the Apure River region. This species, besides being one of the most abundant, is under strong fishing pressure, and despite its commercial importance, there is no information on its population dynamics and exploitation patterns, which is crucial to guide its sustainable management. The objective of the present study was to generate essential biological parameters to determine the status of the P. metaense stock in the Apure River basin, based on size frequency data, collected monthly from commercial landings during the period 1996 - 2003. Some of the population parameters of the species were estimated through empirical relationships and analyzed using fishery stock assessment models (Beverton & Holt 1957). The Yield per Recruit (Y/R) and Biomass per Recruit (B/R) model analyses showed that P. metaense is over-exploited, as shown by these growth and recruitment descriptors. The current fishing exploitation rate of 0.86 exceeds the Biological Reference Points estimated in 1996 (Emax = 0.58), confirming that the stock of P. metaense in the Apure River is being over-exploited above sustainable levels. The mean size of fish landed in 2003 (Lmean= 64.90 cm TL) shows that fish are being caught below the mean length of sexual maturity (Lm= 62.88 cm TL). Likewise, the fishing mortality rate (F2003= 0.95) was higher than the optimal reference point (Fmsy= 0.95). Actions must be taken to monitor the resource to allow its recovery and the size of the fish at first capture to reach acceptable levels (Lc= 54 cm TL).