title: Egg buoyancy variability in local populations of Atlantic cod (Gadus morhua).
abstract: Previous studies have found strong evidences for Atlantic cod (Gadus morhua) egg retention in fjords, which are caused by the combination of vertical salinity structure, estuarine circulation, and egg specific gravity, supporting small-scaled geographical differentiations of local populations. Here, we assess the variability in egg specific gravity for selected local populations of this species, that is, two fjord-spawning populations and one coastal-spawning population from Northern Norway (66-71°N/10-25°E). Eggs were naturally spawned by raised broodstocks (March to April 2009), and egg specific gravity was measured by a density-gradient column. The phenotype of egg specific gravity was similar among the three local populations. However, the associated variability was greater at the individual level than at the population level. The noted gradual decrease in specific gravity from gastrulation to hatching with an increase just before hatching could be a generic pattern in pelagic marine fish eggs. This study provides needed input to adequately understand and model fish egg dispersal.
authors.affiliation: Institute of Marine Research, P.O. Box 1870, Nordnes, 5817 Bergen, Norway ; Department of Biology, University of Bergen, P.O. Box 7800, 5020 Bergen, Norway.
authors.forename: Kyung-Mi
authors.initials: KM
authors.lastname: Jung
authors.affiliation: Department of Biology, University of Bergen, P.O. Box 7800, 5020 Bergen, Norway.
authors.forename: Arild
authors.initials: A
authors.lastname: Folkvord
authors.affiliation: Institute of Marine Research, P.O. Box 1870, Nordnes, 5817 Bergen, Norway.
authors.forename: Olav Sigurd
authors.initials: OS
authors.lastname: Kjesbu
authors.affiliation: Institute of Marine Research, P.O. Box 1870, Nordnes, 5817 Bergen, Norway.
authors.forename: Ann Lisbeth
authors.initials: AL
authors.lastname: Agnalt
authors.affiliation: Institute of Marine Research, P.O. Box 1870, Nordnes, 5817 Bergen, Norway.
authors.forename: Anders
authors.initials: A
authors.lastname: Thorsen
authors.affiliation: Institute of Marine Research, P.O. Box 1870, Nordnes, 5817 Bergen, Norway.
authors.forename: Svein
authors.initials: S
authors.lastname: Sundby