A modified migration model for Atlantic cod, Gadus morhua, off the northeast coast of Newfoundland

• Main Author: Howse, Kristine Anne
• Format: Thesis
• Language: English
• Published: Memorial University of Newfoundland 1993
• Subjects: atlantic cod; Gadus morhua; Newfoundland
• Online Access: https://research.library.mun.ca/10693/; https://research.library.mun.ca/10693/1/Howse_KristineA.pdf

Based on observations of cod overwintering inshore and offshore, a modified migration behavior model for northern cod is presented. The existing paradigm of cod migration behavior considers movement between winter spawning locations offshore and summer feeding locations inshore. These migrations were generally thought to remain relatively consistent from year to year. – Sonic tagging and tracking techniques revealed that some adult cod overwinter inshore, enduring water temperatures previously thought to be inhabited only by juvenile cod. The presence of antifreeze proteins in the blood of wild, adult Atlantic cod during winter indicates that some of the cod overwintering inshore had been exposed to temperatures below 0°C for at least 30 days. Cod overwintering offshore did not have antifreeze proteins in their blood. Analysis of mitochondrial DNA sequences showed no significant differentiation of genotype proportions between inshore and offshore samples of cod in NAFO division 3L. – The existing migration behavior model must be revised taking these new discoveries into consideration. The presence of adult cod throughout the year in the Random island area of Trinity Bay indicates the year round suitability of this habitat for cod. Cod physiology permits individuals to adapt to the winter ocean temperatures and occupy this habitat during the winter months. The new model predicts that not all cod will migrate offshore in the fall. The migration behavior of an individual cod may not be rigid and an individual may overwinter inshore one year and offshore the next.