WSP12063

• File Number: 8240.300.31.J
• Description: San Juan River - Environmental Studies
• Basin: San Juan/Dolores
• Water Division: 7
• Date: 2/1/2000
• Title: Non-Native Species Interactions: Management Implications to Aid in Recovery of the Colorado Pikeminnow and Razorback Sucker in the San Juan River
• Water Supply Pro - Doc Type: Report/Study

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summer rainstorm events that result in repeated scouring of the substrate and heavy sediment
load carried by short-duration flood events.

Mechanical removal of channel catfish, as a potential control measure, was implemented and
evaluated during 1995. Passive (hoop and trammel netting) and active (electro fishing) methods
were employed, with the latter more effective in capturing channel catfish. Removal efforts
employing passive and active methods in discrete reaches (3 river miles) separated by control
reaches were unsuccessful due to failure of passive methods to collect adequate numbers offish
and was discontinued after one sampling season. During 1,967 hours of hoop netting only 25
channel catfish and 11 common carp were removed. River-wide removal of all non-native
species during spring and fall main channel monitoring surveys, 1995-1997, yielded 22,985 fish,
Channel catfish (n=12,660; 5,139 kg) and common carp (n=10,016; 12,433 kg) comprised the
majority offish removed. Analyses of the electrofishing catch per unit effort, mean total length,
and biomass of channel catfish in a sub-reach of Reach 6 (PNM Weir to the Hogback Diversion)
yielded lower abundance estimates from 1996 to 1997 and may be a response to removal efforts,
Transplantation of channel catfish from the San Juan River to isolated recreational angling
impoundments is proposed as a means of disposing of non-native channel catfish to minimize
interactions with native fishes and increase the quality (size offish stocked) of current hatchery-
supported sport fisheries.

It was hypothesized at the beginning of the SJRIP that mimicry of the natural hydro graph through
Navajo Dam releases would benefit native fishes and act to minimize non-native species
interactions. Data collected during this study did not identify negative responses of the non-
native fish community (channel catfish and common carp) to mimicry of the natural hydro graph
(high spring flows timed to coincide with peak Animas River flows), Long-term removal
measures to control large-bodied non-native fishes such as channel catfish, however, may
successfully reduce abundance and distribution and allow for improved conditions and survival
of the native fishes in the San Juan River,

San Juan River Non-native Species Interactions, Final Report, ] February 2000

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