An investigation of genetic and reproductive differences between Faroe Plateau and Faroe Bank cod (Gadus morhua L.)

• Published in: BMC Genetics
• Main Author: Petersen, Petra Elisabeth
• Other Authors: Taggart, John, Penman, David, Dahle, Geir, Patursson, Oystein, Fiskaaling, the Aquaculture Station of the Faroes (http://www.fiskaaling.fo/), and the Faroese Research Council (http://www.gransking.fo/).
• Format: Doctoral or Postdoctoral Thesis
• Language: English
• Published: University of Stirling 2014
• Subjects: Ascertainment bias; Atlantic cod; Early life history; Egg size; Egg size - egg number trade-off; Faroe Bank cod; Faroe Plateau cod; Genetic differentiation; Genetic diversity; Hemoglobin; Microsatellite; Next generation sequencing; Outlier locus; Parentage analysis; Population assignment testing; Population genetics; Population structure; RAD-seq; SNP; SNP validation; Spawning period; Transferrin; Faroe Islands Aquaculture; Fishes Genetics; Faroe Islands; Faroe Bank; atlantic cod; Gadus morhua
• Online Access: http://hdl.handle.net/1893/21613; http://dspace.stir.ac.uk/bitstream/1893/21613/1/THESIS_FINAL.pdf

The Atlantic cod (Gadus morhua L.) fishery is of great economic importance to the Faroese economy. There are two separately managed cod stocks around the Faroe Islands, the Faroe Plateau and the Faroe Bank cod. Both have experienced dramatic decreases in size and informed management decisions are vital for both stock viability and exploitation. The stocks are geographically isolated by an 800 m deep channel and water temperatures are on average 1 – 2 ºC higher on the Faroe Bank than on the Faroe Plateau. There are clear phenotypic differences between the stocks; in particular, the markedly higher growth rate for the Faroe Bank cod has caught public and scientific attention. There is continuing debate regarding the relative importance of genetics and environmental contributions to the contrasting phenotypes. Analyses of reproductive parameters (field data and experimental captive spawnings) as well as analyses of microsatellite and single nucleotide polymorphism (SNP) markers were undertaken to better resolve the issue. Field data as well as data from experimental captive spawnings provided evidence of reproductive differences between Faroe Plateau and Faroe Bank cod. Peak spawning occurred earlier on the Faroe Plateau than on the Faroe Bank and this difference in timing of spawning was maintained in captivity. In particular, differences in sizes of eggs (average diameters of 1.40 and 1.30 mm for Faroe Plateau and Faroe Bank cod eggs, respectively) and indirect evidence of greater volumes spawned by the Faroe Bank females suggested stock differences with respect to egg size – egg number trade-off. It was hypothesised that the strategy adopted by cod on the Faroe Bank, with a higher number of smaller eggs, evolved in response to a more hostile environment (bare seabed and higher exposure to predators) experienced by early life stages in this area. Experimental captive spawnings with Faroe Bank cod showed a large interfamily skew in survival rates of cod eggs and fry. Egg size was identified as a useful indicator ...