The most spectacular action that I ever seen in wildlife is salmon runs on Kuril Lake, that is located in located at the southern tip of Kamchatka Peninsula, within the Southern Kamchatka Wildlife Refuge. This Refuge is a part of Kronotsky nature reserve, so in the past years I was lucky to work there. Now, in the middle of August, the most action is going on there. So let's virtually transport ourselves 250 miles south of my ranger station in kronotskaya tundra.
Kuril Lake is the largest spawning ground for sockeye salmon in Eurasia (if not in the world) and is of great importance to the world fishing industry. The fish is spawning in shallow waters of the lake and in the small rivers that flows into it.
The salmon that enters the lake does not rush to spawn right away. First it forms large groups of tens of thousands fish and "hangs out". Individuals in those groups stay so close to each other that these clusters look like solid red patches on lake surface from a helicopter. It was noticed a long time ago that fish does not fill the lake chaotically, salmon always moves along the shores in clockwise direction.
I was lucky to observe the fish entering a small river from the lake several past summers on a river Gavryushka, that flows into Kuril lake. The width of the river mouth is only about five feet and the depth at the shallow sand bar at the entrance to the river - couple of inches - it is easy to cross it without getting your shoes wet! Upstream from the entrance, which is part of the sand beach that surrounds the lake, the river gets deeper, and there are places near the banks with snags and boulders - the places where fish can hide from bears.
For several days thousands and thousands of salmon individuals gather at the outfall of Gavryushka River. The fish goes back and forward along the lake shore, teasing hungry bears who dive after it in deep water, but with rare success.
Suddenly, as if following unknown signal, large number of fish throws itself into that narrow and shallow place of the river mouth. They form a wave. A wave of seemingly boiling mixture of fish and water that is so strong that can overthrow a human. The energy of this movement is so great that in several minutes the place, that was previously to shallow for large fish to cross, becomes deeper and wider!
First dozens of fish are inevitably caught by bears, but while the animals are busy eating their first catch, hundreds of others have time to cross this shallow bar and reach relatively save deep places up the river. This process repeats many times.
At least two million of salmon entered the Kuril Lake this year. It is more than enough for effective reproduction of this important biological resource - salmon, that is being hunted by both bears and humans.