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The Problem Numerous agencies are developing national protocols for adequate passage of aquatic organisms through culverts and other structures. Currently, the U. S. Forest Service and the U. S. Army Corps of Engineers are seeking information on the swimming ability of bull trout to help assess passage issues. Swimming performance of bull trout has not been examined previously. Bull trout in the western United States are now listed as threatened under the Endangered Species Act. One cause of bull trout population declines is fish passage issues caused by dams and diversion structures. In order to best design or modify culverts and other fish passage structures in watersheds where bull trout are present, baseline swimming performance information is needed. In 2002, we completed a preliminary study of bull trout swimming performance and will expand on this work in 2003.
Objectives
Methodology For objective 1, wild juvenile and adult bull trout will be collected as needed from the Metolius River and Lake Billy Chinook, Oregon. Fish will be subjected to "fatigue velocity tests", briefly described as follows. A single fish will be netted from a holding tank, rapidly weighed and measured, and placed into a swim chamber, where it will be allowed to adjust for 1 h at a water velocity of about 0.5 body lengths per second (BL/s). Following this adjustment period, water velocity will be gradually increased over about 5 min to a selected test velocity that will range from about 1 to 5 or 6 BL/s. Fish will be tested at the chosen velocity for 120 min or until fatigued. At each velocity, we will attempt to swim up to 10 fish. All swimming tests will be conducted at 10 -11ºC in an open, flume-like swimming chamber. The data will be used to construct curves describing the relation between percentage of fish fatigued and water velocity. For objective 2, we will build a swim chamber equipped with a laser beam detection system for highly accurate and precise estimates of burst swimming performance. For these tests, a single bull trout will be placed in the swim chamber and startled by touching its tail area, causing it to sprint upstream in a long, linear flume. The resulting data will be used to describe the acceleration and maximum swimming speed of bull trout. For objective 3, we will surgically implant a piece of narrow plastic tubing (a cannula) into the dorsal aorta of a fish. After surgery, the fish will be placed in a swimming chamber and swum at 5 or 6 BL/s until they fatigue. Before, during, and after swimming, we will collect blood samples via the cannula to assess the physiological responses of bull trout to swimming and exhaustion. We will measure pH, hematocrit, lactic acid, glucose, cortisol, potassium, sodium, and perhaps other blood constituents. Highlights and Key Findings
In 2002 we attempted to estimate the swimming performance of 71 bull trout at 11 and 15ºC. For these tests, we used a closed Blazka-style swim chamber. Valid estimates of their swimming performance were difficult to obtain because of the behavior of bull trout in these enclosed swim tunnels. Typically, bull trout in these tunnels flare out their pectoral fins and maintain position on the bottom, rest against the back screen, and seem to "give up" at low velocities. Thus, in 2003 we hope that using a different method with an open swimming flume will allow us to interact more with the fish and help us overcome some of the difficulties we had with our earlier tests.
Where Are We Headed In 2003 We will continue laboratory experiments on bull trout collected from the wild to measure various aspects of their swimming and physiological performance. These experiments have been briefly described in the methodology above. Collectively, data from our studies will provide a solid foundation of basic biological information for bull trout that can be used in future studies assessing their passage performance through fishways or other facilities. Project Contact Matthew G. Mesa Email: matt_mesa@usgs.gov Publications |
