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Marine Ecology Progress Series

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MEPS 556:237-250 (2016)  -  DOI:

Complex post-larval dispersal processes in Atlantic cod revealed by age-based genetics and relatedness analysis

John B. Horne1,*, Ian R. Bradbury2, Ian G. Paterson1, David Hardie3, Jeffrey Hutchings1,4, Benjamin J. Laurel5, Paul V. R. Snelgrove6, Corey J. Morris2, Robert S. Gregory2, Paul Bentzen1

1Marine Gene Probe Laboratory, Department of Biology, Dalhousie University, 1355 Oxford Street, Halifax, NS B3H 4R2, Canada
2Department of Fisheries and Oceans Canada, 80 E. White Hills Road, St. John’s, NL A1C 5X1, Canada
3Department of Fisheries and Oceans Canada, Dartmouth, NS B2Y 4T3, Canada
4Centre for Ecological and Evolutionary Synthesis, Department of Biosciences, University of Oslo, Oslo 0316, Norway
5Fisheries Behavioral Ecology Program, Alaska Fisheries Science Center, National Marine Fisheries Service, NOAA, Hatfield Marine Science Center, Newport, OR 97365, USA
6Department of Ocean Sciences and Biology Department, Memorial University of Newfoundland, St. John’s, NL A1C 5S7, Canada
*Corresponding author:

ABSTRACT: Population connectivity among adult marine organisms is often attributed to dispersal during the egg/larval stage. However, post-larval dispersal may also influence connectivity, particularly when juvenile nursery habitats are separated from adult spawning habitats. Here we used age-based population genetics and kinship analysis to explore changes in population connectivity across life-history stages in Atlantic cod Gadus morhua. We genotyped 364 adult cod from the northwest Atlantic and 671 age-0 juveniles from 18 sites around eastern Newfoundland, with 72 and 15 microsatellite loci, respectively. Adult cod genotypes exhibited more population structure than was detected in juveniles across similar spatial scales. Both age classes had similar allelic diversities, but juveniles exhibited less genetic linkage and fewer departures from Hardy-Weinberg expectations than adults at the same loci. We detected significant kinship relationships in adult cod only within sampling locations, but 1 putative pair of juvenile kin was separated by >500 km. Collections of adults also displayed higher group relatedness compared to juveniles. Genetic differences between age classes are likely due to a combination of non-random mortality and non-random sorting of admixed juveniles into different adult habitats. Many studies overlook post-larval dispersal as a factor of marine population connectivity, but pre-adult relocation may be demographically and adaptively significant, in cod and other species.

KEY WORDS: Gadidae · Kinship · Newfoundland · Marine dispersal · Fisheries · Northwest Atlantic

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Cite this article as: Horne JB, Bradbury IR, Paterson IG, Hardie D and others (2016) Complex post-larval dispersal processes in Atlantic cod revealed by age-based genetics and relatedness analysis. Mar Ecol Prog Ser 556:237-250.

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