Effects of carbon dioxide on rainbow trout larvae:
application for invasive fish eradication
Jason Baldes, Montana State University, 102 A Paisley Ct., Bozeman, Montana 59715 jason.
J. A. Gross and R. E. Gresswell, U.S. Geological Survey, Northern Rocky Mountain Science
Molly A. Webb, USDI Fish and Wildlife Service, Bozeman Fish Technology Center, 4050 Bridger
Canyon Road, Bozeman, Montana 59715
Currently, efforts are underway to eradicate invasive fish species that threaten the
ecological integrity of aquatic ecosystems. Several studies have examined the effects
of anesthetizing fish for easier handling, surgical procedures, tagging and management.
Carbon Dioxide (CO ) is an approved and efficient anesthetic for adult fish in medicine and
aquaculture and is favorable due to lack of residues, zero withdrawal period and does not need
to be registered as its classification is generally regarded as safe (GRAS). Carbon dioxide
has also shown to have lethal effects on other life history stages of fish. In this study, various
early life stages of Rainbow trout (Oncorhynchus mykiss) larvae were exposed to CO in the
form of dry ice pellets to determine the critical period of sensitivity for mortality in a model
salmonid species. Studies were conducted in aluminum tanks (n = 3 tanks per treatment,
with three chambers in each tank with 40 larvae per chamber) with 68 liters of filtered creek
water (dissolved CO = 4 mg/l, dissolved O = 8.125 mg/l, pH = 7.78, temperature = 12.9
°C, conductivity = -55 mV, Total alkalinity as CaCO = 160 mg/l). Larvae exposed at post
hatch day 10 had increased susceptibility to CO , when compared with earlier embryonic
stages. The results of the experiment indicate that early rainbow trout life history stages
are susceptible to CO but only at late embryonic stages and may have implications for
systematically eradicating invasive salmonids.