STATUS REPORT PINNIPED PREDATION AND HAZING AT BONNEVILLE DAM IN 27 Robert Stansell, Sean Tackley, and Karrie Gibbons 4/27/7 This report is the eighth of regular status reports on the pinniped predation and hazing activities being conducted at Bonneville Dam in 27. PRELIMINARY RESULTS The first Steller sea lion (Eumetopias jubatus) was seen at Bonneville on December 1, 26, the first California sea lion (Zalophus californianus) on January 8, 27, and the first harbor seal (Phoca vitulina) on January 18, 27. This is about one month earlier for the California sea lions to arrive than last year. We have seen as many as 9 Steller sea lions and 37 California sea lions at the dam so far on any given day (see Figure 1). The most number of sea lions total for one day so far was 39 on April 4 and 26. PREDATION FIGURES Unexpanded numbers for fish observed taken between January 8 and April 26 are: 2,14 salmon/steelhead (see Figure 2) 36 sturgeon (55 larger than 5 feet)(see Figures 2) 14 Lamprey, 2 smolt, unidentified (see Figure 2) Total catch (Chinook in particular) has increased over the past few weeks, especially last week, as can be seen in Figure 2. At least 133 salmonids were observed taken on April 23. The Chinook run this year (Figure 3) is running good now and topped 3,5 on April 25. It looks like another later than average run, earlier than in 26, and similar to 25 (Figure 4). Steller sea lions are the primary predators of white sturgeon (Acipenser transmontanus) in the Bonneville Dam tailrace (only six taken by California sea lions). As Steller sea lion numbers declined, so did sturgeon catches. Observers recorded only 19 of the 36 sturgeon takes after hazing began. Most salmonid species have been caught at PH 1 tailrace so far this year (793), now followed by the spillway (62) and PH 2 (578). An additional 432 unidentified fish species have been caught at the project so far. At least 24 salmonids and 9 unidentified fish have been seen caught elsewhere below the project, and more likely (data not fully entered). Steller sea lions account for 354 of the 36 sturgeon seen taken. California sea lions account for 2,5 of the 2,14 salmonids observed taken. California sea lions took approximately 258 additional unidentified fish (likely salmonids) while Stellers were seen to take approximately 172 additional unidentified fish (likely sturgeon). Harbor seals were observed to take 2 unidentified fish and have not been seen since hazing began.
HAZING IMPACTS Hazing began on February 28. The hazing was effective in reducing the number of Steller sea lions present and drastically reduced the number of sturgeon taken after this began (Figure 2). Hazing also altered the behavior of the California sea lions in that they stayed farther away from the dam and did not surface as much. However, now that the Chinook run has begun, fewer animals seem impacted by the hazing activities and remain in the tailrace. As the number of Chinook passing Bonneville Dam exceeded 1, per day on April 17, the boat hazing is no longer using seal bombs in the boat restricted zone to reduce the chance of harming or impacting salmon. In addition, with spill occurring, the boats are not allowed into that area for safety reasons, and many sea lions use this area as a sanctuary. Land based hazing at this location is mostly ineffective due to the distances involved. The spillway has become the area where most fish are taken over the past couple of weeks. OTHER ITEMS OF INTEREST C44 was observed on March 28, 29, 31, April 2, 4, 5, 7, 13, and 16 in the Washington shore fish count window and in the tailrace area on most days. We now have multiple observers with sightings of C44 climbing over one of the floating orifice gates at Powerhouse 2 to the fishway. The past few weeks he has not been spotted inside the fishway. He has been seen to haul out on the corner collector concrete apron, but not on the trap yet. He also appears to be in the fishways before 5:h and after 2:h, so he is likely active at night. Trapping occurred again on April 25 with two California sea lion and two Steller sea lions caught. The animals transported to Astoria last week on the 19 th were released as follows: one three miles north of Seaside released on the 19 th (back in Astoria by 8am the next morning and at Bonneville this morning, April 27), and the other released on the 2 th at Newport (back at Bonneville on April 26). This individual, already branded and a regular since 22, weighed in at 115 lbs, possibly a record! Yet he is not the biggest animals we have seen! The sea lions prefer to haul out on the concrete apron of the corner collector in large numbers, sometimes well over 3-4 have been seen. SUMMARY California sea lion numbers and salmonid take have increased dramatically over the past few weeks. Chinook counts are finally starting to climb now. Steller sea lion presence had been reduced after hazing began, however the past week or so about four have been seen around the trap and project (although two were trapped and hauled to Astoria). Hazing has been less effective at reducing California sea lion numbers and predation, but observers and hazing personnel have reported changes in sea lion behaviors. These changes include increased travel between tailraces in response to hazing, less time spent at the surface during foraging, and less time spent close to dam structures. Chinook salmon are the primary prey item for California sea lions at Bonneville Dam, and the cumulative number of salmonids taken this year (Figure 5) shows they are on pace to top 3, taken. We will have to see if the trend persists and what the fish run does in the next month to determine overall effectiveness of the harassment program.
Figure 1. Daily minimum pinniped abundance. Pinniped Abundance 27 45 4 35 Number of Pinnipeds 3 25 2 15 1 5 1-Jan 8-Jan 15-Jan 22-Jan 29-Jan 5-Feb 12-Feb 19-Feb 26-Feb 5-Mar 12-Mar 19-Mar 26-Mar 2-Apr 9-Apr 16-Apr 23-Apr 3-Apr 7-May 14-May 21-May 28-May Date Figure 2. Daily salmonid, sturgeon, and unknown fish predation by pinnipeds 14 Daily Salmonids, Sturgeon, and Unknown Fish Caught by Pinnipeds Bonneville Dam, 27 12 1 UNKNOWN SALMONIDS STURGEON Number 8 6 4 2 1/1/27 1/8/27 1/15/27 1/22/27 1/29/27 2/5/27 2/12/27 2/19/27 2/26/27 3/5/27 3/12/27 3/19/27 Date 3/26/27 4/2/27 4/9/27 4/16/27 4/23/27 4/3/27 5/7/27 5/14/27 5/21/27 5/28/27
Figure 3. Total daily salmonid passage (steelhead and Chinook) at Bonneville Dam, 27. TOTAL SALMONIDS PASSING BONNEVILLE DAM, 27 4 35 3 NUMBER OF SALMONIDS 25 2 15 1 5 1-Jan 8-Jan 15-Jan 22-Jan 29-Jan 5-Feb 12-Feb 19-Feb 26-Feb 4-Mar 11-Mar 18-Mar 25-Mar 1-Apr 8-Apr 15-Apr 22-Apr 29-Apr 6-May 13-May 2-May 27-May Figure 4. Daily Chinook passage at Bonneville Dam in 25, 26, and the 1 year average. DAILY CHINOOK PASSAGE AT BONNEVILLE, 26, 25, 1 YEAR AVERAGE 1 9 8 7 25 26 1 YR AVG 6 COUNT 5 4 3 2 1 6-Feb 13-Feb 2-Feb 27-Feb 6-Mar 13-Mar 2-Mar 27-Mar 3-Apr 1-Apr 17-Apr 24-Apr 1-May 8-May 15-May 22-May 29-May
Figure 5. Cumulative estimated daily salmonid catch by pinnipeds at Bonneville Dam, 22-27. 27 data not expanded yet and preliminary. CUMULATIVE ESTIMATED DAILY SALMONID CATCH BY PINNIPEDS AT BONNEVILLE DAM 4. 35. 3. SALMONID CATCH 25. 2. 15. 22 23 24 25 26 27 1. 5.. 1/1 1/8 1/15 1/22 1/29 2/5 2/12 2/19 2/26 3/4 3/11 3/18 3/25 4/1 4/8 4/15 4/22 4/29 5/6 5/13 5/2 5/27