Salmon movements in Alaska

Here I made a few models for a fisher (Andrew Scudder). At the time NOAA were producing two week forecasts of the currents in Prince William Sound in Alaska. Andrew had the idea that we might be able to model salmon returning to their natal rivers by using the current fields that were forecast to be happening when the fishery was in progress. The fishery is a competitive one, and it is tightly controlled so that only a certain number of salmon are caught in a very short period while they are returning to their home rivers, and enough are left to populate their home rivers for following years. Many smolt (juvenile salmon) are reared in hatcheries to augment the population going to sea.

Anyhow, we had a few goes at it, and Andrew was the most successful fisher that year (his love of all things technical may have been a correlate also!)

Here is a video which shows the model salmon returning in a realistic current field and also shows smolt leaving, they don’t usually leave and return at the same time – but it is useful to consider how the smolt leave the river systems and how the returning adults may use a scent trail to return. I was thinking of augmenting these models by having the adult salmon produce a urine based scent trail which others follow – but really the net result will likely not be much different – because in the end the adults have to push up against the prevailing currents and tides in the same way. For instance, Andrew described how the salmon ‘hit the beach’ in certain current and weather situations – the model salmon do exactly that. The model therefore suggests that this behaviour is an involuntary result of the water movement and the directed movement of the salmon combined. As usual with these models, they can only be used in the scientific process as a way to suggest new hypotheses which are tested in nature.