Salmon turn up the heat on trout!
Ann Arbor, MI — Landlocked Atlantic salmon, once abundant in Lake Ontario and the Finger Lakes of New York, were extirpated more than a century ago. Since that time, exotic salmonines such as rainbow trout (steelhead) have become established in former Atlantic salmon waters and elsewhere. Competition with these exotic salmonines, especially during early life stages in nursery streams, is one of several factors that may hinder restoring Atlantic salmon to their native habitat.
Ecologists at the State University of New York, College of Environmental Science and Forestry (SUNY-ESF) in Syracuse, NY, studied the effects of temperature on growth, survival, and interactions of co-existing Atlantic salmon and rainbow trout in the laboratory and in natural streams.
"Juvenile Atlantic salmon have a higher temperature tolerance than do rainbow trout, and seem to survive and grow better at high temperatures," explains Steve Coghlan, a former graduate student at SUNY-ESF. "Therefore, we wanted to see if water temperature had any effect on the outcomes of competitive interaction between the two species."
Laboratory results revealed that in the presence of rainbow trout, Atlantic salmon lost weight at 15°C, maintained weight at 20°C, and gained weight at 25°C, whereas the opposite effect occurred for rainbow trout. For Atlantic salmon maintained alone, no temperature effects on growth were found.
Coghlan and Ringler also stocked Atlantic salmon fry into twenty tributaries to Lake Ontario and Owasco Lake (one of the Finger Lakes) accessible to migratory rainbow trout. At the end of the summer, they estimated biomass of both species at each site. In streams with mean summer temperatures above 21°C, rainbow trout were absent, but Atlantic salmon were able to survive and grow. In the remaining streams, as temperatures decreased from 21°C to 15°C, the proportion of Atlantic salmon to rainbow trout decreased, but the combined biomass of both species increased.
According to Coghlan, if the management objective is to maximize total biomass of salmonines produced in each stream, cold streams obviously are more productive than warm streams, but stream temperatures may dictate which mixture of salmonine species results in the greatest production.
"Streams too warm for much rainbow trout production may be excellent candidates for Atlantic salmon restoration," he says, "especially if competition with rainbow trout is limiting elsewhere."
Original Publication Information
Results of this study "Temperature-dependent Effects of Rainbow Trout on Growth of Atlantic Salmon Parr," are reported by Stephen M. Coghlan Jr. and Neil H. Ringler in the latest issue (Volume 31, No. 4, pp. 386-396) of the Journal of Great Lakes Research, published by the International Association for Great Lakes Research, 2005.
Contacts
For more information about the study, contact Steve Coghlan, Arkansas State University Department of Chemistry and Physics, P.O. Box 419, State University, AR, 72567-0419; scoghlan@astate.edu; (870) 972-3103.
For information about the Journal of Great Lakes Research, contact Marlene Evans, Editor, National Water Research Institute, 11 Innovation Boulevard, Saskatoon, SK, S7N 3H5, Canada; editor@iaglr.org; (608) 692-1076.
Links
Since 1967, IAGLR has served as the focal point for compiling and disseminating multidisciplinary knowledge on North America's Laurentian Great Lakes and other large lakes of the world and their watersheds. In part, IAGLR communicates this knowledge through publication of the Journal of Great Lakes Research, available to members in print and electronic form. A searchable archive of the journal is available online and includes the abstracts of articles from the journal's inception in 1975 through the most recent issue. In addition, complete articles are available to members who have signed up for an electronic subscription.
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