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FEASIBILITY OF DEVELOPING AND MAINTAINING A SPORT FISHERY IN '1T1E SALT RIVER PROJECT CANALS
<br />METHODS
<br />Fish Surveys
<br />We used electrofishing to determine the
<br />number of resident fish species (species richness)
<br />in the canal. Resident fish were defined as those
<br />fish found in the canal either from natural
<br />reproduction or immigration. We used catch-per-
<br />unit-effort (CPUE; fish/hr) as an index of relative
<br />species abundance.
<br />We electrofished the Arizona Canal monthly
<br />from October 1992 through July 1994 using a 4.3-
<br />m Alumacraft John-boat. This electrofishing
<br />platform was equipped with a Honda EMS-4000
<br />generator, a variable voltage pulsator (VVP-15),
<br />and a spherical electrode. Typically, the
<br />electrofishing crew consisted of a netter and a
<br />boat/VVP-15 operator. Electrofishing was
<br />conducted at night using floodlights for better
<br />visibility and to attract some fish species
<br />(Minckley 1973). Typically, the range of VVP-15
<br />settings used were: 100-150 V, 10-15 A, 30-40%
<br />DC pulse width, and 60-80 Hz frequency. The
<br />netter used an activating footpad to control
<br />electrical output. Effort was recorded in seconds
<br />using a chronometer activated by the footpad.
<br />The electrofishing boat was driven downstream
<br />within each site, covering both sides and the
<br />middle of the canal. Stunned fish were netted and
<br />placed in 121-L containers with fresh canal water.
<br />No anesthetics were used to sedate the fish.
<br />We categorized fish into 4 general groups:
<br />natives, game fish, forage fish, and others. Native
<br />fish were: Sonora suckers (Catostomus insignis),
<br />desert suckers (C. clarki), and roundtail chubs
<br />(Gila robusta). Game fish were defined as:
<br />largemouth bass (Micropterus salmoides), yellow
<br />bass (Morone mississippiensis), channel catfish, and
<br />rainbow trout. Threadfin shad (Dorosoma
<br />petenense) and red shiners (Cyprinella lutrensis)
<br />were designated as forage fish or prey. We
<br />defined "other" species to be: white amurs, yellow
<br />bullheads (Ameiurus natalis), bluegill (Lepomis
<br />macrochirus), green sunfish (L. cyanellus),
<br />smallmouth bass (Micropterus dolomieu), common
<br />carp (Cyprinus carpio), goldfish (Carassius auratus),
<br />flathead catfish (Pylodictis olivaris), oscar
<br />(Astronotus ocellatus), and walleye (Stizostedion
<br />vitreum). Species, total length (TL in mm),
<br />weight (g), and disposition (i.e., released alive,
<br />dead, preserved) were recorded. Each fish was
<br />examined for fin clips, tag scars, deformities,
<br />external parasites, and spinal injuries. White
<br />amurs and game fish with a TL ? 250 mm were
<br />tagged with a Floyo tag near the terminus of the
<br />dorsal fin. FloyO tags were used to identify
<br />individual fish, with known length, weight, and
<br />location, in subsequent sampling efforts. All fish
<br />were released back into the canal after processing,
<br />except selected individuals for contaminant
<br />analysis or reference collections.
<br />Catch-per-unit-effort indices were also used to
<br />indicate changes in fish abundance across sites and
<br />over time. To determine differences in CPUE by
<br />site over time, each electrofishing effort was
<br />assigned to a specific season for each year. Each
<br />season covered a period of 3 months: September
<br />through November (Fall), December through
<br />February (Winter), March through May (Spring),
<br />and June through August (Summer). Two
<br />exceptions were Fall 1992 when sampling started
<br />in October, and Summer 1994 when sampling
<br />concluded in July.
<br />To assess the canal's ability to sustain fish
<br />health and nutritional needs, estimates of fish
<br />physiological conditions were calculated from
<br />length-weight relationships. We calculated
<br />condition factors (K) using Fulton's equation
<br />(Anderson and Gutreuter 1983) for each species
<br />by site. Comparisons of K between different
<br />species cannot be calculated because of differences
<br />between body shapes and sizes; i.e., the size and
<br />shape characteristics of trout are different than
<br />those of sunfish. Additionally, K values tend to
<br />increase as fish length increases (Anderson and
<br />Gutreuter 1983). Our comparisons were limited
<br />to individuals of the same age group. Mean K
<br />factors were not calculated for fish weighing < 10
<br />g. The precision of our field scale (1-g units) was
<br />not effective in providing reliable weight
<br />measurements of fish < 10 g. We considered K
<br />values of >_ 1.00 to represent fish that were in
<br />good physiological condition, with the
<br />understanding that the range of optimum K varies
<br />with different species and age groups (Anderson
<br />and Gutreuter 1983). Our estimates of K were
<br />intended to provide a rough estimate of fish well-
<br />being in the Arizona Canal.
<br />Seasonal length frequency distributions for the
<br />6 most abundant species were plotted to estimate
<br />age classes and growth over time. Across-season
<br />length frequencies were plotted for yellow bass
<br />and roundtail chub. Age classes, or cohorts, were
<br />determined using the Peterson method (Jearld
<br />1983), which identifies distinct peaks and ranges of
<br />length into separate age groups.
<br />R R. WRIGHT AND J. A. SORENSEN 1995 ARIZONA GAME & FISH DEPARTMENT, TECH. REP. 18 11
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