Mortality, Age structure, Paralichthys patagonicus, Southem Brazil
Abstract
The age composition and mortality coefficients of the white flounder, Paralichthys patagonicus (Jordan, 1889), from southem Bra;zil were studied based on totallength and age at length data from the trawl fishery landings in Rio Grande from 1989 to 1993. Males were more frequent in the 30 to 40 em length classes IDId females in the classes over 40 em. Recruitment occurs mainly at ages 2 and 3, and age groups 2 to 7 accounted for more than 90% of the weight of the catches. The instantaneous natural mortality coefficients (M) were estimated from maximum observed ages as 0.35 and 0.42 for females and males, respectively. Averllge instantaneous total mortality coefficients (2) (1990-1993), estimated using catch curves, were 1.14 for males and 0.99 for females. Estimateq instantaneous fishing mortality coefflcients (F=-'Z-M) were 0.72 for males and 0.64 for female~ and exploitation coefficients (E=F/Z) were 0.63 and 0.65, respectively. Exploitation rates over 0.5 indicate that the catches inthe second half of the 1980' s were higher than those sustainable.
