9449

• UCREFRP Catalog Number: 9449
• Author: Hawkins, J. A.
• Title: Recapture and growth rates of three Colorado River endangered fish species
• USFW Year: 2003.
• USFW - Doc Type: a comparison between electrofishing and non-electrofishing.
• Copyright Material: NO

Generally, these results agree with those of Schneider (1992) who found that
after 1-2 years, survival of largemouth bass (Micropterus salmoides) and walleye
(Stizostedion vitreum) was similar among gear types (electrofishing, trapping, and
angling). These results also agree with results of Dalbey et al. (1996) who found that
neither electrofishing gear type nor injury severity affected long-term (335 day) survival
of rainbow trout (Oncorhynchus mykiss).
If electrofishing had nonlethal negative effects on individual fish that were greater
than non-electrofishing gears, the expectation would be lower growth rates for fish
initially captured by electrofishing. This study showed that growth of Colorado
pikeminnow, humpback chub, and razorback sucker captured by electrofishing was
similar to growth of the same species caught by non-electrofishing gears during both
the first and second growing seasons after initial capture. Also, none of the treatments
were statistically different. These results agree with those of Schneider (1992) who
found no growth differences in largemouth bass and walleye 1--2 years after capture
with 230-V AC currents compared to fish captured by trap nets or angling. In other
studies, growth rates were lower for fish severely injured by electrofishing compared to
those with no or minor injuries (Dalbey et a1.1996; Gatz, et al. 1986), but in this study it
was unknown whether any fish had severe injuries caused by sampling gear.
Overall, there was no compelling data to suggest differences in recapture or
growth rates due to the sampling gear, suggesting that electrofishing and
9