Mc. Healey et al., Computer simulations of the effects of the Sitka eddy on the migration of sockeye salmon returning to British Columbia, FISH OCEANO, 9(3), 2000, pp. 271-281
The Sitka eddy is a mesoscale eddy, 300 km in diameter, that develops off S
E Alaska in about one year in two. The eddy has surface currents exceeding
50 km day(-1) and it has been suggested that the eddy could deflect migrati
ng salmon to the south, thereby reducing the proportion of British Columbia
(BC) sockeye salmon accessible to Alaskan fishers. We modelled its effects
on the migration of sockeye salmon (Oncorhynchus nerka) returning to north
ern BC, using an individual-based model to simulate migration paths, migrat
ion timing and metabolic costs of salmon with different migration behaviour
s. Except when their migration behaviour included positive rheotaxis, salmo
n that encountered the eddy had faster migration times and lower metabolic
costs than those that did not. The least complex migration behaviour, compa
ss orientation with no rheotaxis, was only slightly less efficient in metab
olic terms than the optimal migration paths determined by dynamic programmi
ng. Our simulations show that the Sitka eddy itself does not deflect migrat
ing salmon to the south or south-east regardless of migration behaviour, bu
t that by interrupting the normal northward flow of the Alaskan Current, th
e eddy could influence latitude of landfall of migrating salmon.