Kenai Sockeye Salmon
The sockeye salmon (Oncorhynchus nerka)
run on the Kenai River in Alaska is perhaps one the largest conglomerations of commercial and recreational fishermen in modern times. Scores of boats net the silvery sockeye at the mouth of the river and thousands flock to the banks to hook these fish which may number over 100,000 a day. At the peaks of the runs, camps set-up 24-hour stations where people rotate from hooking, to cleaning, to smoking, and then packaging these prized-eating fish. Vacationing families may process hundreds of pounds each day. That is, if they hit the peaks. A few days off, when just a few thousand fish are passing through, might result in just one fish for the pot.
There are generally two peaks in the runs each year, which range in a one month solar window of time. Each peak is about 10 days apart. Most anglers revisit the river based on a multiyear average. Some plan on a two week trip just to make sure they hit one of the peaks. The anglers say that the fish were "early" or "late" when they are off.
In Biological Time
, author Bernie Taylor considered that there must be a better method to figure this out. The fish seem to arrive in synchrony with their kin, so the movements must be timed in some manner. The question was how? The results of a 12-year conversion of Alaskan Department of Fish and Game data (based on sonar counts) to the lunar cycle demonstrated that the two peaks are never early or late, only on a different calendar than commercial and recreational anglers are timing them against. Each of the two peaks can be timed to the Neap Tides (or away from the Spring Tides). This is pictured below in the graph which looks at the first peak of sockeye salmon counts relative to the high tides. These moderate lunar tides (Neap Tides) make passage through the inlet easier for these fish and help to synchronize their movements.
For the sockeye salmon to have been present in the inlet for passage at the Neap Tides, they must have been positioned further out in the marine environment during the Spring Tides. The Neap Tide migration through the lower Kenai River also synchronizes their upriver migrations and ultimately their spawning. Biological Time
demonstrates that many events in the life of the salmon and steelhead trout, from when these fish out-migrate as juveniles to their spawning period, are precisely timed to both the solar and lunar cycles of light and darkness.