POPULATION BIOLOGY AND PRODUCTION OF THE RED SWAMP CRAYFISH PROCAMBARUS-CLARKII (GIRARD) IN THE LOWER MONDEGO RIVER VALLEY, PORTUGAL

The population of Procambarus clarkii from the lower Mondego River val ley, Portugal, was studied for 13 months. Population structure was ana lyzed and 7 cohorts were identified. The main recruitment period occur red from the second half of October to the end of November, but juveni les were found throughout the year. Tracking recognizable cohorts alon g size-frequency distributions from successive sampling dates allowed an estimation of growth parameters in order to calibrate a growth mode l incorporating seasonal adjustments. Average growth rate was estimate d at 1.16 mm of total length per week. Production was estimated at 27. 22 g m-2 per year, the average biomass at 5.4 g m-2, and the P/B ratio at 5.03. Females outnumbered males throughout the year and the averag e sex ratio was 0.24.