(Read for yourself about bird predation on juvenile salmon here)
I'll sum it up for you. Caspian terns first nested on East Sand Island near Chinook, Wash., in 1984. They started nesting there because the island was beginning to be augmented by dredge materials on the east side in 1983. In 1985, vegetation began to sprout up and the Caspian terns moved on to another island in the Columbia River farther east. These terns nested on Rice Island in 1986, which was another dredge disposal site. Rice Island is about 16 miles east of East Sand Island. The Caspian tern population exploded and it was decided these terns had to be moved back to East Sand Island after some rehabilitation work was done to make the island attractive to the birds. This move was done because we believed the terns would not eat as many juvenile salmon in estuary at the East Sand Island location. We were wrong about their diet. By 2001, the entire Caspian tern colony was moved to East Sand Island. In 2008, the Army Corps of Engineers began the process to move at least half of the Caspian tern colony from East Sand Island to other sites in Oregon and California by 2015.
In 2010, there were about 8,300 breeding pairs of Caspian terns on East Sand Island. Double-breasted cormorants started nesting there in 1989 and today, these fish eating birds number 13,600 breeding pairs. For purposes of this article, we now have some 43,800 birds living on this 62-acre island near the mouth of the Columbia River. Then add to that 1,000 breeding pairs of Brandt's cormorants, 5,000 breeding pairs of western gulls, 17,000 brown pelicans and you get some 72,800 adult birds enjoying the all they can eat juvenile salmon buffet.
Since 2000, the Caspian terns have averaged eating more than 5 million salmon smolts per year. In 2008, they ate about 6.5 million salmon smolts. In 2010, the double-breasted cormorants ate about 19 million salmon smolts. Since 2000, the double-breasted cormorants have averaged eating about 7.5 million smolts per year. Why is this important to know? For Snake River salmon, especially our summer Chinook it is very important to know because the biggest feeding period of these birds coincides almost exactly with the arrival of our wild and hatchery Chinook smolts.
Cormorants are eating the lionshare of the salmon they eat in a year during May, they peak around May 8-19. The Caspian terns peak salmon eating frenzy is about May 15-29.
The McCall Fish Hatchery releases its 1,000,000 smolts each year around March 19. Those fish are about to embark on a 716.5 mile journey to the Pacific Ocean, but they don't take off immediately. If they did take off immediately upon release, they would likely reach Lower Granite Dam in 7-10 days, then depending on if they are passed through the hydrosystem or barged they would arrive in the estuary at varying early dates. If barged they would be there about four to seven days after they were picked up at Lower Granite Dam because it takes two days to barge them below Bonneville Dam and another two to five days for them to get to the estuary. So, if they left immediately on March 19 they could be in the estuary as early as March 30 if barged. If they pass through the hydrosystem they would be below Bonneville 6-10 days after they arrived at Lower Granite Dam and another 2-5 days to swim to the estuary. The smolts that pass through the hydrosystem, if they left immediately, would arrive in the estuary as early as April 3.
However, they don't typically leave immediately upon release at Knox Bridge. The average travel time for McCall Fish Hatchery smolts to Lower Granite Dam, and I assume they leave about the same time as the naturally produced smolts in the South Fork of the Salmon River, is 48 days. They hang around in the river a while before they take off for the ocean. We lose 404,000 hatchery smolts during these 48 days. Now if we assume the average these fish are arriving at Lower Granite Dam on May 6. Those that get picked up by barges, about 240,000, are dropped below Bonneville Dam on May 8. Those that pass through the hydrosystem arrive below Bonneville Dam May 12-16. Those that are barged arrive in the estuary about May 10-13 and those that pass through the eight dams arrive in the estuary about May 14-21. It's no wonder these Caspian terns and cormorants turn their attention to a glut of salmon for their dietary needs during the month of May.
Here is another prime example of how we have failed to manage nature. We created a place for Caspian terns and cormorants and various other birds, then we inadvertently moved them, then we purposely moved them and now we are going to move them again. We're doing our best impression of God or nature and God and nature are not amused.
Once upon a time, we did nothing and God and nature enriched us, today we do just about everything under the sun and God and nature have seen fit to impoverish us with a lesson in humility.
When will we get back to allowing the natural course of things, only then can we expect to see rivers choked with salmon again. Only then will we have saved the salmon, when we stop micromanaging everything and allow our rivers to be rivers again.