Connectivity mechanisms in a population complex of coastal cod
Appears in the following Collection
- Biologisk institutt 
AbstractIn this thesis I have studied connectivity processes affecting the population structure of coastal cod on the Norwegian Skagerrak coast. I have focused on three aspects of the processes. Firstly the dynamics and the integrity of the spawning grounds. This included potential retention mechanisms. There is a clear tendency for spawning site selection where adult cod chose to spawn in inshore areas where the current is likely to retain eggs and larvae close to the spawning site. The spawning sites are local and closely situated and the cod stay on the spawning ground throughout the spawning. Secondly I have studied the scale of the spatial extent of the sub-population structure. Samples of mature cod from spawning areas along the coast demonstrated genetic differences between samples taken as close a 30 km apart. Dispersal of tagged cod suggested that the cross section of the 95 % recapture probability distribution to be 18 km. This suggests that Skagerrak coastal cod populations are structured at a fjord scale. Finally I have studied movement and area utilization of adult cod. These studies suggested that the cod in some years may utilize a somewhat larger area for feeding and that there are some indications for a seasonal migration. However most cod in the fjord populations are stationary and only perform diel vertical migration and small scale horizontal movement as primary means for relocation. Overall these findings suggest that the coastal cod populations along the Skagerrak coast has, for a mobile marine species, low connectivity and that population structure may be on a finer scale than previous reported.
PAPER I. Sigurd Heiberg Espeland, Ailin Fernløf Gundersen, Esben Moland Olsen, Halvor Knutsen, Jakob Gjøsæter and Nils C. Stenseth (2007) Home range and elevated egg densities within an inshore spawning ground of coastal cod. ICES Journal of Marine Science, 64(5): 920-928, 2007.
PAPER II. Halvor Knutsen, Esben Moland Olsen, Lorenzo Ciannelli, Sigurd Heiberg Espeland, Jan Atle Knutsen, Jan Henrik Simonsen, Stig Skreslet, Nils Chr. Stenseth (2007) Egg distribution, bottom topography and small-scale cod population structure in a coastal marine system. Marine Ecology Progress Series, 333: 249-255, 2007.
PAPER III. Per Erik Jorde1, Halvor Knutsen, Sigurd Heiberg Espeland, Nils Chr. Stenseth (2007) Spatial scale of genetic structuring in coastal cod Gadus morhua and geographic extent of local populations Marine Ecology Progress Series, 343: 229-237, 2007.
PAPER IV. Sigurd Heiberg Espeland, Esben Moland Olsen, Halvor Knutsen, Jakob Gjøsæter, Didrik Danielssen, Nils Christian Stenseth (2008) New perspectives on fish movement: kernel and GAM smoothers applied to a century of tagging data on coastal Atlantic cod Marine Ecology Progress Series, 372: 231-241, 2008.
PAPER V. Lorenzo Ciannelli, Halvor Knutsen, Esben M. Olsen, Sigurd H. Espeland, Lars Asplin, Anders Jelmert, Jan Atle Knutsen, Nils Christian Stenseth (2010) Maintenance of small-scale population structure in a marine population in relation to water circulation and egg characteristics.
PAPER VI. Sigurd Heiberg Espeland, Adine Guldborg Thoresen, Esben Moland Olsen, Leif Christian Stige, Halvor Knutsen, Jakob Gjøsæter and Nils Chr Stenseth (2010) Diel vertical migration patterns in young Skagerak coastal cod. Marine Ecology Progress Series, vol 405: 29-37, 2010