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." ,.,J , j., p "C-' ',r-~ ~..) .t..:; r.o ',' t:. ..', " ". Methods Nan-native fishes were collected from main channel and larger secondary channel habitats during adult monitoring surveys. Raft-mounted electrofishing gear (pulsed direct current) was used to sample downstream in I-river-mile (RM) increments. Attempts were made to net all fish stunned near the front of the raft (anode). Additional fish were occasionally netted by a 'chase' raft and are included in the data compilations. Electrofishing surveys were conducted primarily during daylight hours, but did include some crepuscular collections. For each RM sampled, the location, seconds shocked, and number by species were recorded. At every fifth RM (i.e" a designated mile-DM) the total length (1L), standard length (SL), and weight of each specimen collected was also recorded. Catch per W1it effort (CPUE) was calculated as the number of fish collected per minute of electro fishing for all fish species sampled. Catch rates were determined for channel catfIsh and common carp and compared to the overall catch. Catch data were swnmarized by reach for the entire river sampled (Farmington, New Mexico to Mexican Hat, Utah), and evaluated for longitudinal trends and anomalies. Distribution, Abundance, and Movement - Movement of channel catfish and common carp collected by electrofishing was evaluated using Floy anchor tags and recapture of tagged fish. Channel catfish and common carp (>200mm TL) were tagged with sequentially numbered anchor tags 1992-1997 during spring, summer, and fall electrofishing trips. In J 992 and spring 1993 most channel catfish and common carp collected were tagged. During summer J 993 through fall 1995 most channel catfish and common carp collected from OM's were tagged, Additional channel catfish and common carp were tagged in 1995 during a pilot mechanical removal study, In 1996 channel catfish and common carp were tagged upstream of the Hogback diversion as part of a study to evaluate fish passage upstream and downstream of the five identified diversions on the San Juan River. Most non-native fish not tagged were enumerated and released alive 1992 through fall 1995. In 1996, most non-native fish collected downstream of the Hogback diversion were removed from the river and in 1997 most non-native fish collected were removed river- wide (see further discussion in Chapter V, Mechanical Removal). For each fish recaptured the capture location (RM), species, TL, SL, weight, and tag number were recorded. Movement direction and distance and growth data were determined from initial or last capture data. Because anchor tag loss for channel cattish has been reported as high (up to 90%) (Greenland and Bryan, 1974), Brooks et at. (\ 994) began evaluating tag retention in 1993. All channel catfish and common carp collected and tagged during April and May 1993 electro fishing surveys received two tags and retention was based upon the nwnber oftags remaining at the time of recapture. Fish recaptured through 1997 were used to determine the percent retention for tags implanted during April and May 1993, Schnabel population estimates (Overton, 1971) were calculated for collections made during 1992-1995 using mark and recapture data collected during main channel electrofishing sampling. Confidence intervals of 95% were calculated for each river reach estimate, Radio telemetry- To supplement Floy tag data and to refine seasonal movement patterns 18 channel catfish were implanted with radio transmitters in September 1996. Two size classes of channel catfish were surgically implanted (350-465 mm and >550 mm TL) using Advanced San Juan River Non-native Species Interactions, Final Report, I February 2000 13