Washington Hunter
Well-known member
Posted on Friday, April 21, 2006 (PST)
With time slipping by and upriver spring chinook salmon counts at the Columbia River's Bonneville Dam at historic lows, salmon managers this week pressed for a test removal of structures new on the scene that they speculate could be delaying passage.
As soon as Monday two of the "sea lion exclusion devices" newly installed at fish ladder entrances could be lifted from the water to see if it triggers a surge in salmon passage.
The managers theorize that there are goodly numbers of upriver chinook in the lower river, but for whatever reason they are not proceeding upstream past the dam with historic timing. The SLEDs, huge grates with 16-inch-wide openings between the bars that allow fish through but not sea lions, could somehow be daunting the fish as they search for a lane upstream, managers say.
Corps officials this week balked at pulling any of the SLEDs, five-ton metal grids that were designed to prevent California sea lions and other pinnipeds from entering the ladders in pursuit of their favorite prey, salmon.
They expressed doubt that a big pool of fish are waiting just below the dam -- and even if there are large number of upriver spring chinook in-river, they are dawdling elsewhere for other reasons.
Officials this week discussed the issue at both the Technical Management Team, which mulls dam operations to balance fish passage and power needs, and a technical advisory group for Fish Passage Operations and Maintenance.
FPOM studied the issue Thursday at the request of TMT and opted to advise that two of the SLEDs, one nearest the north shore at powerhouse two and one nearest the south shore at the first powerhouse, be lifted from in front of the fish ladder entrances Monday for a two-day trial.
The grates vary from 10 feet to 15 feet in width and 30 feet to 36 feet in height with two each slid vertically down in front of the dam's 12 ladder entrances. Corps officials say cranes on-site have the capability, just barely, to pull the heavy SLEDS located closest to the shore on either side of the river. Lifting any of the other grates would require heavier equipment be brought in, which would escalate costs.
Corps officials at the FPOM said management officials at their Portland District office have said they would not pull the sleds without a formal written request. Such a request was to be drafted following the FPOM meeting. Corps officials were to meet this afternoon to decide whether or not the SLEDs would be pulled out.
The Washington Department of Fish and Wildlife's Cindy LeFleur posed the idea of removing SLEDs at both TMT and FPOM.
"We want to see if that is part of the reason for the delay," LeFleur said Wednesday. "If you look at what we see in the fishery, they should be passing the dam by now."
Sport fishers from the Interstate 5 bridge at Portland down to the river mouth caught and kept an estimated 3,156 upriver chinook before the fishery was closed April 13. They also released 962 unclipped fish. Sport catch rates normally seem to rise or fall depending on the size of the run and were relatively strong this year.
"There should be significant… some tens of thousands of upriver spring chinook. Where are they?" LeFleur asked.
Counts have been extremely low at the dam, totaling only 280 through Wednesday as compared to a 10-year average of 54,448 through April 19. Tuesday's and Wednesday's counts, 33 and 32 upriver spring chinook, were the highest this year. The 10-year average count on April 19 is 4,358 upriver chinook as the runs built toward what is normally a late April or early May peak.
According to John North of the Oregon Department of Fish and Wildlife, the count is the lowest through April 19 on a record that dates back to 1939.
Last year's run was late-timed. Counts in 2005 totaled 121 chinook through April 10, compared to 120 this year. But soon thereafter, the 2005 run began to stir with the daily count passing 100 for the first time April 10 and building toward a May 5 peak count of 6,065. Officials estimate that last year's return to the mouth of the river totaled 106,900 upriver spring chinook.
The 2005 count at Bonneville totaled 2,039 by April 19, nearly 9 times this year's count of 280 through that date. Runs, like last year's, can start late but finish strong. One of the lowest counts on record was in 1952 when only 1,653 chinook had passed the dam through April 19, North said. The final count was 129,700 with one of the latest peak daily counts on record -- May 27.
Corps officials say that there is little evidence that large numbers of fish are bunched up in Bonneville's tailrace. The Corps has observers positioned along the dam throughout the daylight hours. Their goal is to keep track of the number and species of fish that are being taken below the dam by pinnipeds. The goal of the study is to evaluate sea lion impacts on the spring salmon run.
Sea lions have in recent years flocked to the base of the dam to gorge on the salmon run. For the past three years an average of about 100 individual sea lions have been observed at the dam during the March through May period.
There has been a like number of pinnipeds this year with a peak daily count of about 50 to 60 marine mammals, according to the Corps' Robert Stansell. The number averaged from 35 to 40 per day through early April but in recent days the count has slipped to 25 to 30, Stansell said. Normally the marine mammals don't start drifting back out to the ocean, and their southern California breeding grounds, until late May.
And the sea lions are being observed taking fewer salmon, from 20 or so daily through early April to only four or five in recent days.
"If the fish are out there we're not seeing them," Stansell said.
A University of Idaho research effort is in place to evaluate the salmon behavior as they approach the base of the dam, and the ladder entrances. The research is part of a $1.5 million package to haze and otherwise try chase the sea lions away from the base of the dam, and bar them from the ladders (the SLEDs cost about $1 million to build and install). Included is monitoring to evaluate the effect of the efforts, on sea lions and fish.
Researchers began to trap chinook below the dam late last week but only 12 have been captured through midweek.
Christopher Peery, who is leading the fish passage research, told FPOM members Thursday that only a couple of the radio-tagged fish had been sensed by antenna's back at the base of the dam, and they arrived early this week. The radio receivers at the base of the dam have a range of up to 30 feet. They detect the tagged fish as they approach an entrance and enter, or not.
"None of them have made it inside (the fish ladders) yet," Peery said. The tagged fish are released eight miles downriver from the dam. In past years' research, tagged fish usually make it back to the dam in 8 to 9 hours, and pass within 20 to 30 hours. So something appears to be making them dally.
Slightly cooler than normal water temperatures, a spawning cue for the fish, could be having an effect, as could a sudden upswing in river flows. But NOAA Fisheries' Gary Fredricks pointed out that this year's deviations from the norm are not unusual, not as unusual as the meager numbers of fish crossing Bonneville.
Peery said Wednesday that he doubted the SLEDs were causing the delay. Hastily constructed SLEDs were installed at a few of the ladder entrances late last year when the lagging run raised fears that sea lions inside the ladders might be plugging the fishes' upstream surge.
Monitoring of radio-tagged fish last year for the few weeks that the SLEDS where in place showed only a slight hesitation at the ladder entrances before the fish plunged in.
"It didn't seem to have a big effect," Peery said. The tests were conducted late in the season, when the water is warmer and fish are more hellbent on reaching their spawning destination. Still, Peery said he did not feel the grates were posing a blockage.
"The only value I see (of pulling out any of the grates) is that it may alleviate the fears" of the fish managers, Peery said.
Fredricks said that NOAA favored the test. Last year a court-ordered summer spill regime at Little Goose Dam on the Snake River created a strong eddy below the dam that appeared to be stalling chinook passage.
A spill adjustment was made, and "within hours we saw a huge response" with 10 times the number of fish passing the dam the day following the change, Fredricks said. He said that he doubted that the SLEDs were causing a problem, but that fish managers wanted to find out for sure.
LeFleur argued that "the only difference between last year and this year is that the SLEDs are in."
"I can't think of anything else to try, or to explain this," she said. "I'm feeling like it's a fish emergency. We need to do something."
With time slipping by and upriver spring chinook salmon counts at the Columbia River's Bonneville Dam at historic lows, salmon managers this week pressed for a test removal of structures new on the scene that they speculate could be delaying passage.
As soon as Monday two of the "sea lion exclusion devices" newly installed at fish ladder entrances could be lifted from the water to see if it triggers a surge in salmon passage.
The managers theorize that there are goodly numbers of upriver chinook in the lower river, but for whatever reason they are not proceeding upstream past the dam with historic timing. The SLEDs, huge grates with 16-inch-wide openings between the bars that allow fish through but not sea lions, could somehow be daunting the fish as they search for a lane upstream, managers say.
Corps officials this week balked at pulling any of the SLEDs, five-ton metal grids that were designed to prevent California sea lions and other pinnipeds from entering the ladders in pursuit of their favorite prey, salmon.
They expressed doubt that a big pool of fish are waiting just below the dam -- and even if there are large number of upriver spring chinook in-river, they are dawdling elsewhere for other reasons.
Officials this week discussed the issue at both the Technical Management Team, which mulls dam operations to balance fish passage and power needs, and a technical advisory group for Fish Passage Operations and Maintenance.
FPOM studied the issue Thursday at the request of TMT and opted to advise that two of the SLEDs, one nearest the north shore at powerhouse two and one nearest the south shore at the first powerhouse, be lifted from in front of the fish ladder entrances Monday for a two-day trial.
The grates vary from 10 feet to 15 feet in width and 30 feet to 36 feet in height with two each slid vertically down in front of the dam's 12 ladder entrances. Corps officials say cranes on-site have the capability, just barely, to pull the heavy SLEDS located closest to the shore on either side of the river. Lifting any of the other grates would require heavier equipment be brought in, which would escalate costs.
Corps officials at the FPOM said management officials at their Portland District office have said they would not pull the sleds without a formal written request. Such a request was to be drafted following the FPOM meeting. Corps officials were to meet this afternoon to decide whether or not the SLEDs would be pulled out.
The Washington Department of Fish and Wildlife's Cindy LeFleur posed the idea of removing SLEDs at both TMT and FPOM.
"We want to see if that is part of the reason for the delay," LeFleur said Wednesday. "If you look at what we see in the fishery, they should be passing the dam by now."
Sport fishers from the Interstate 5 bridge at Portland down to the river mouth caught and kept an estimated 3,156 upriver chinook before the fishery was closed April 13. They also released 962 unclipped fish. Sport catch rates normally seem to rise or fall depending on the size of the run and were relatively strong this year.
"There should be significant… some tens of thousands of upriver spring chinook. Where are they?" LeFleur asked.
Counts have been extremely low at the dam, totaling only 280 through Wednesday as compared to a 10-year average of 54,448 through April 19. Tuesday's and Wednesday's counts, 33 and 32 upriver spring chinook, were the highest this year. The 10-year average count on April 19 is 4,358 upriver chinook as the runs built toward what is normally a late April or early May peak.
According to John North of the Oregon Department of Fish and Wildlife, the count is the lowest through April 19 on a record that dates back to 1939.
Last year's run was late-timed. Counts in 2005 totaled 121 chinook through April 10, compared to 120 this year. But soon thereafter, the 2005 run began to stir with the daily count passing 100 for the first time April 10 and building toward a May 5 peak count of 6,065. Officials estimate that last year's return to the mouth of the river totaled 106,900 upriver spring chinook.
The 2005 count at Bonneville totaled 2,039 by April 19, nearly 9 times this year's count of 280 through that date. Runs, like last year's, can start late but finish strong. One of the lowest counts on record was in 1952 when only 1,653 chinook had passed the dam through April 19, North said. The final count was 129,700 with one of the latest peak daily counts on record -- May 27.
Corps officials say that there is little evidence that large numbers of fish are bunched up in Bonneville's tailrace. The Corps has observers positioned along the dam throughout the daylight hours. Their goal is to keep track of the number and species of fish that are being taken below the dam by pinnipeds. The goal of the study is to evaluate sea lion impacts on the spring salmon run.
Sea lions have in recent years flocked to the base of the dam to gorge on the salmon run. For the past three years an average of about 100 individual sea lions have been observed at the dam during the March through May period.
There has been a like number of pinnipeds this year with a peak daily count of about 50 to 60 marine mammals, according to the Corps' Robert Stansell. The number averaged from 35 to 40 per day through early April but in recent days the count has slipped to 25 to 30, Stansell said. Normally the marine mammals don't start drifting back out to the ocean, and their southern California breeding grounds, until late May.
And the sea lions are being observed taking fewer salmon, from 20 or so daily through early April to only four or five in recent days.
"If the fish are out there we're not seeing them," Stansell said.
A University of Idaho research effort is in place to evaluate the salmon behavior as they approach the base of the dam, and the ladder entrances. The research is part of a $1.5 million package to haze and otherwise try chase the sea lions away from the base of the dam, and bar them from the ladders (the SLEDs cost about $1 million to build and install). Included is monitoring to evaluate the effect of the efforts, on sea lions and fish.
Researchers began to trap chinook below the dam late last week but only 12 have been captured through midweek.
Christopher Peery, who is leading the fish passage research, told FPOM members Thursday that only a couple of the radio-tagged fish had been sensed by antenna's back at the base of the dam, and they arrived early this week. The radio receivers at the base of the dam have a range of up to 30 feet. They detect the tagged fish as they approach an entrance and enter, or not.
"None of them have made it inside (the fish ladders) yet," Peery said. The tagged fish are released eight miles downriver from the dam. In past years' research, tagged fish usually make it back to the dam in 8 to 9 hours, and pass within 20 to 30 hours. So something appears to be making them dally.
Slightly cooler than normal water temperatures, a spawning cue for the fish, could be having an effect, as could a sudden upswing in river flows. But NOAA Fisheries' Gary Fredricks pointed out that this year's deviations from the norm are not unusual, not as unusual as the meager numbers of fish crossing Bonneville.
Peery said Wednesday that he doubted the SLEDs were causing the delay. Hastily constructed SLEDs were installed at a few of the ladder entrances late last year when the lagging run raised fears that sea lions inside the ladders might be plugging the fishes' upstream surge.
Monitoring of radio-tagged fish last year for the few weeks that the SLEDS where in place showed only a slight hesitation at the ladder entrances before the fish plunged in.
"It didn't seem to have a big effect," Peery said. The tests were conducted late in the season, when the water is warmer and fish are more hellbent on reaching their spawning destination. Still, Peery said he did not feel the grates were posing a blockage.
"The only value I see (of pulling out any of the grates) is that it may alleviate the fears" of the fish managers, Peery said.
Fredricks said that NOAA favored the test. Last year a court-ordered summer spill regime at Little Goose Dam on the Snake River created a strong eddy below the dam that appeared to be stalling chinook passage.
A spill adjustment was made, and "within hours we saw a huge response" with 10 times the number of fish passing the dam the day following the change, Fredricks said. He said that he doubted that the SLEDs were causing a problem, but that fish managers wanted to find out for sure.
LeFleur argued that "the only difference between last year and this year is that the SLEDs are in."
"I can't think of anything else to try, or to explain this," she said. "I'm feeling like it's a fish emergency. We need to do something."
