Selective fishing gear : A review on the effects of selective fishing gear on cod in the Baltic Sea

• Main Author: Modig, Karl Johan
• Format: Bachelor Thesis
• Language: English
• Published: Linnéuniversitetet, Institutionen för biologi och miljö (BOM) 2013
• Subjects: Baltic Sea; Atlantic cod (Gadus morhua); fishing mortality; fisheries induced evolution; Biological Sciences; Biologiska vetenskaper; atlantic cod; Gadus morhua
• Online Access: http://urn.kb.se/resolve?urn=urn:nbn:se:lnu:diva-31302

The populations of Atlantic cod (Gadus morhua) in the Baltic Sea has been heavily exploited for decades, with fishing mortalities close to, and for several occasions, even above one. The larger part of the spawning stock biomass is consequently being removed each year. The issue of fisheries induced evolution (FIE) has been gaining attention from researchers lately. The selection pressure driving this evolution is powered by a connection between high mortality rates and heritable traits. The fishing in the Baltic Sea is mainly performed with size selective gear that can impose selection on traits like size-at-age or size-at-maturity. In this review I show how FIE may affect the Baltic cod towards decreased size-at-age/maturity and how size selective fishing on stocks at low levels can increase the inherent instability of the population as well as deprave the Baltic Sea of ecosystemic services from cod.