CHANGES IN THE SIZE STRUCTURE OF FISH POPULATIONS OF THE WESTERN ENGLISH CHANNEL OFF THE COAST OF PLYMOUTH BETWEEN 1919 AND 2005

• Main Author: Rogers, Samantha
• Format: Thesis
• Language: unknown
• Published: University of Plymouth 2005
• Subjects: Gadus morhua
• Online Access: http://hdl.handle.net/10026.2/625

To analyse the effects of anthropogenic stress and rapid global warming on fish populations off the coast of Plymouth, 100 years of data which details both the abundance and length of different species has been explored. The size structure of five different species populations were studied {Gadus morhua, Microstomus kitt, Merlangius merlangus, Solea solea and Trisopterus minutes) in order to determine any changes within the size structure over time, and in order to identify any relationships between the size structure of the species with fishing pressure and with temperature change. The size structure of the species populations was seen to decrease over time (apart from M. kitt). There was a trend between the size structures of species and fishing effort, where as fishing effort increased the size structure of species populations decreased. T. minutes populations showed a negative trend between size structure and average annual catch per unit effort, indicating that density dependent competition is influencing the size structure of this trash fish species. The average annual sea surface temperature (SST) at the time if recruitment was shown to be responsible for the majority of variance in both G. mohua and T. minutes populations, where as SST increases the size structure of these populations' decreases. Faculty of Science