Seasonal variation in the trawl codend selectivity of common pandora (Pagellus erythrinus)

Seasonal changes in the selectivity of a 40 mm polyethylene trawl codend for common pandora (Pagellus erythrinus) were tested under similar fishing conditions in spring, summer and autumn 2002, and winter 2003. Data were obtained using the covered codend technique and analyzed using a logistic model fitted with the maximum likelihood method. Parameters of mean curves for each trip were estimated by using Fryer’s between‐haul variation model. To determine seasonal changes in the condition of the fish, samples were taken to cover the entire length range of the catch along with length measurements to the nearest mm and weights to the nearest 0.1 g. Results showed a tendency for decrease in selectivity from summer (L₅₀ = 11.3 cm, SR = 2.2 cm) and autumn (L₅₀ = 11.2 cm, SR = 1.7 cm) to winter (L₅₀ = 10.7 cm, SR = 2.4 cm) and spring (L₅₀ = 10.2 cm, SR = 2.9 cm). Potential effects of water temperature, fish condition, population size structure, and gonad developments on selectivity are discussed to explain the seasonal variation in trawl codend selectivity.