Factors affecting purse seine catches: An observer-based analysis

Abstract

A total of 72 fishing trips were carried out by fishery scientists onboard a purse seiner in the Pagasitikos Gulf (Greece) in an attempt to identify factors affecting total and individual species' catches. As trawling is completely banned in the study area, purse seining is the main fishing method. It was found that month, water depth and fishing area affected total and Trachurus spp. catches of the purse seine fishery, with month and water depth alone explaining 77.8% and 6.4% respectively of the total variation of the data. Significant interactions observed indicate that the fluctuations in total catches differed by month and fishing area as well as fishing area and water depth. Fishing area and water depth interaction were found to affect Trachurus spp. catches significantly. Results also suggested that generalized linear modelling of the purse seine catches can be used to obtain representative abundance indices by reducing the observed variability. Fishery scientists' onboard observations alongside fish market recordings during the same period confirmed that each fisher has developed an individual decision-making fishing process. Fisher's trip choice behaviour was found to be modulated by several factors, such as distance of fishing grounds from the port, market demands (both in terms of species and market prices), weather conditions, alternative fishing strategies, previously gathered information, economic pressure and personal skills. These findings are discussed in the light of the need to incorporate additional quantitative information to stock abundance estimates if improved fisheries management scenarios are to be advanced.