SALMON FOOD CHAINS

      Every July, in recent years, through live cameras and our computer screen, I watch several brown bears catch many mature sockeye salmon swimming up Brooks River in Katmai National Park in Alaska to spawn.  That park is in southern Alaska, at the base of the Aleutian Island chain that juts into the northern Pacific Ocean.   

     After a few years feeding on small creatures in the Pacific Ocean, hordes of sockeyes swim along the Alaskan Coast until they smell the river they hatched in.  Then they tirelessly push up the river {Brooks River}, day after day, by the hundreds of thousands to the gravelly shallows where they hatched.  They wiggle over rocky shallows, leap ten foot waterfalls and slip swiftly through deeper waters to reach their destination.  But many salmon don't make it to their spawning spots because of the unceasing predations of brown bears.     

     Brown bears compete with each other for the better places along Brooks River to catch sockeye salmon.  The best spots are just above the falls where the bears grab the salmon in their mouths as the salmon leap up the falling water.  The other, better places are the rocky shallows where the bears can more easily see the fish and trap them against rocks or the bottom of the river.  But some bears enter deeper water and peer about underwater for salmon.  Big males usually get the better fishing spots.  

     Eager to put on much fat for the coming winter's sleep, some bears catch up to 30 salmon a day, every day of the salmon run upstream.  Sometimes, some bears only ingest the fat-filled skin and discard the fish body in the river or on its banks.  But other times they eat almost the whole fish, only leaving a few bits and pieces behind for ravenously scavenging creatures to consume.  And they do, big time, creating several salmon food chains.

     The small critters the salmon ate in the ocean are near the base of those food chains.  Brown bears eat much of each salmon, but leave orange-red parts behind that are noticeable on the river shores.  Flocks of graceful glaucous-winged gulls scavenge a good bit of sockeye carcasses in the shallows and on river banks.  Around a half-dozen, majestic bald eagles, both adult and immature, also feed heavily on salmon bodies.  Occasionally, one or two impressive wolves and a party of raucous northern ravens also help themselves to half-eaten salmon carrion along the river, and its shores.   

     Katmai National Park is a wilderness with tall grasses along Brooks River and forests of spruces clothing mountain slopes.  Sockeye salmon ascend Brooks River to spawn, but many are stopped short by brown bears, who leave behind many scraps for several kinds of scavenging creatures to consume.      

     

       

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