Manuscript

• Main Authors: Overexploited Flatfish, Hoarau G, Boon E, Rijnsdorp A. D, Stam W. T, Olsen J. L
• Other Authors: The Pennsylvania State University CiteSeerX Archives
• Format: Text
• Language: English
• Subjects: Iceland
• Online Access: http://citeseerx.ist.psu.edu/viewdoc/summary?doi=10.1.1.514.8769; http://dissertations.ub.rug.nl/FILES/faculties/science/2004/g.g.hoarau/c6.pdf

We used DNA from archived otoliths to estimate effective population size (Ne) in plaice (Pleuronectes platessa) based temporal fluctuations in allele frequencies from samples collected between 1924 and 2002. Our results show that plaice Ne is five orders of magnitude smaller than the estimated census sizes, i.e., at 20,000 in the North Sea and 2,000 in Iceland. Populations examined between 1924 and ca 1950 were in Hardy Weinberg Equilibrium. The emergence of heterozygote deficiencies from ca. 1970 (that are not attributable to sampling or technical artefacts, but attributable to inbreeding) coincide with the beginning of post-WWII, industrial-scale beam-trawling on the spawning grounds of the North Sea and around Iceland. We hypothesise that fishing-mediated reduction in both census and effective population sizes of plaice, in combination with disruption of mating behaviour at the spawning grounds has further reduced the effective population size thus tipping the balance and allowing inbreeding to emerge. Although the mechanism remains speculative, this is the first demonstration of probable fisheries-induced inbreeding and signals the need for understanding the social and mating behaviour in these fish.