9444

• UCREFRP Catalog Number: 9444
• Author: Hawkins, J. A.
• Title: X-ray Assessment of Electrofishing Injury of Colorado Pikeminnow.
• USFW Year: 2002.
• USFW - Doc Type: Recovery Program Project 64,
• Copyright Material: NO

probably suffocated, "a common result of excess exposure to high, tetanizing power
densities near the electrodes" (Snyder 1995).
Colorado pikeminnow have died during electrofishing in other studies and
examination and x-rays of the carcasses have not revealed injuries or spinal
abnormalities in those fish. For example, a Colorado pikeminnow died after being
electrofished from a flooded tributary during ISMP sampling on the Yampa River in
1995 (W. Elmblad, personal communication). The electrofishing unit was operating
unusually and the operator noticed a Colorado pikeminnow swimming at the surface
about 5 m from the cathode. The fish turned belly-up and died. It had no external
injuries and x-ray and necropsy at the Colorado Division of Wildlife, Fish Health Facility,
in Fort Morgan did not reveal internal injuries. The boat's cathode was later found to be
corroded and not fully functional and was suspected to have caused an unusual
electrical event.
Only one fish was observed bleeding at the gills during this study, but other
researchers and I have observed gill-bleeding in Colorado pikeminnow following
electrofishing (W. Elmblad, personal communication). In this study, there was no link
between gill-bleeding and spinal injury. Snyder (1995) suggested that bleeding was not
associated with spinal injuries or tetany and the long-term effects of gill-bleeding on
survival were unknown. Interestingly, the bleeding fish captured in this study was in
apparent electrotaxis toward a cathode which is an unusual response and indicates
potential equipment malfunction. This reinforces the need to check equipment regularly
for polarity and proper functioning.
It was unknown if other internal organs or tissues were damaged as a result of

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