FOOD OF CHANNEL CATFISH IN THE COACHELLA CANAL, CALIFORNIA

PAUL C. MARSH Center for Environmental Studies, Arizona State University, Tempe, AZ 85287

ABSTRACT Channel catfish, Ictalurus punctatus (75-414 mm total length), in the Coachella Canal, California, fed primarily upon Trichoptera (Smicridea utico, Nectopsyche sp.), Odonata, filamentous algae, chironomids, and aquatic Lepidoptera (Parargyractis confusalis). The high use of Lepidoptera larvae is heretofore unreported. Threadfin shad (Dorosoma petenense) and Asiatic clam (Corbicula fluminea), although locally abundant, were not primary food items. These results emphasize the omnivorous, opportunistic nature of channel catfish feeding habits.

INTRODUCTION. — Channel catfish, Ictalurus punctatus, Imperial County, California. Station A was a pool-like area were introduced into the lower Colorado River in 1892-3 (U.S. and straight reach immediately below a concrete check-drop Fish and Wildlife Service 1981), were common by the early structure, Station B was a linear reach with no structures, and 1940's (Dill 1944) and now flourish throughout the system, Station C was a double-barreled, concrete box siphon. including hundreds of kilometers of artificial waterways. Detailed descriptions of the study area and sampling stations There, as throughout its North American range, channel were provided by Minckley (1981b). catfish provide an important sport fishery. One hundred fifty-three specimens from the three stations Food habit studies on this species have been conducted at were preserved in 10% formalin, measured (total length ITN many localities representative of a wide variety of habitats to the nearest mm) and weighed (nearest 0.01 gm) in the (see Miller 1966 and Carlander 1969 for reviews). Channel laboratory. The digestive tract (esophageal septum to anus) catfish are generally omnivorous and opportunistic; young was removed and esophagus plus stomach were separated feed primarily upon aquatic insects and other benthic from the intestine at the sphincter. Wet weights (nearest 0.01 arthropods while larger individuals are increasingly gm) after blotting were obtained from stomach plus esophagus piscivorous. Dill (1944) reported that channel catfish (mean before and after removal of contents; weights of total contents length 155 mm) from the West Main Ditch, Imperial County, were determined by subtraction. Food items from each California, fed primarily upon chironomid larvae, caddisfly stomach were examined at a magnification of 10X, identified larvae, odonates, terrestrial insects and spiders, and "ooze." and enumerated, and percentage volume of each constituent Catfish from the lower Colorado River fed variously upon sago was visually estimated. Foods were analyzed independently pondweed (Potamogeton pectinatus), centrarchid fishes, for 2 to 5 major size groups of catfish (<100, 100-149, 150- crayfish, filamentous algae and small quantities of aquatic 199, 200-299, and >299 mm TL) from each station. Intestinal insects (Kimsey et al. 1957). Minckley (1981a) reported contents of 20 fish representing all size groups were macrophytes, detritus, molluscs (Corbicula fluminea), qualitatively examined for comparison with stomach crayfish, and fishes as predominant stomach contents from contents. the same region. Channel catfish comprised about 51% of more than 9,000 RESULTS. — Channel catfish ranged in length from fish taken in rotenone samples from the Coachella Canal, 75-4r5 mm TL = 161) and in weight from 4.12-533.24 gm California, in November 1980, and provided an opportunity to = 46.66). The fish were largest at Station A (I TL =168 mm, obtain additional information on feeding relationships of wt = 52.79 gm), smallest at Station B TL = 105 mm, channel catfish in the desert Southwest. I wt = 13.20 gm) and intermediate at Station C TL = 129 The Bureau of Reclamation, Boulder City, Nevada, mm, i wt =18.16 gm). All but two stomachs contained at least supported fish collection with funding, equipment, and man- some food, most were full. Aquatic insects were the com- power. William Rinne of that organization deserves special monest food; crayfish, fish, filamentous algae, and other items thanks. California Department of Fish and Game cooperated were relatively rare although in some individuals they con- with permits and assistance. tributed the major biomass. Foods eaten were generally similar at all sites (Table 1). MATERIALS AND METHODS. — Channel catfish were A hydropsychid caddisfiy larva, Smicridea utico, was the obtained at three locations in the earth-lined Coachella Canal, overwhelmingly dominant food. It occurred at greater than

Marsh, P.C. 1981. Food of channel catfish in the Coachella Canal, California. Journal of the Arizona-Nevada Academy of Science 16:91-95.

91 92 JOURNAL OF THE ARIZONA-NEVADA ACADEMY OF SCIENCE VOL. 16

Table 1. Mean number (N) and biomass (B) of food items in channel catfish from the Coachella Canal, California.

STATION A B C A ± B C Food Item Insects Baetis sp. 0.15 <0.01 0.40 <0.01 0.43 <0.01 0.18 <0.01 Odonata 5.26 0.16 0.00 0.00 0.48 <0.01 4.42 0.13 Smicridea utico 135.20 0.54 1.58 0.05 135.90 0.45 135.30 0.51 Nectopsyche sp. 4.28 <0.01 0.20 <0.01 0.14 <0.01 3.56 <0.01 Parargyractis confusalis 2.81 0.01 0.20 <0.01 0.62 <0.01 2.42 0.01 Chironomidae 9.77 <0.01 0.20 <0.01 0.38 <0.01 8.14 <0.01 Crayfish 0.06 0.008 0.00 0.00 0.00 0.00 0.05 0.007 Fish 0.02 0.03 0.00 0.00 0.00 0.00 0.00 0.00 Filamentous algae 0.15 0.00 0.00 0.00 0.00 0.13 Miscellaneous 0.04 0.01 0.00 0.00 0.38 <0.01 0.09 0.01 Unidentified 0.008 0.01 0.00 0.00 0.00 0.00 0.006 <0.01 Number of fish 125 5 21 151 Mean TL (mm) 168 105 129 161 Mean weight (gm) 52.79 13.20 18.16 46.66 Biomass per stomach (gm) 1.16 0.06 0.46 0.82

99% frequency (Fig. 1), averaged 131 individuals per stomach (Table 1), and contributed 62.2% of overall biomass (Fig. 2). One catfish (323 mm TL) contained 646 individuals. Frequency of occurrence of the caddisfly was similar for all size classes of fish (Fig. 3); however, at Station A their percentage contribution to biomass dropped from 80-92% in fish of 150-199 mm TL to 55-28% in fish of 200-299 mm TL. Mean individual weight of caddisflies was constant at 3-5 mg. The total of approximately 20,000 caddisflies observed in stomachs included only 13 pupae and no adults. Chironomid midges (including larvae and a few pupae and adults) were in more than 70% of all stomachs, but due to their small size and low numbers contributed only a fraction of a percentage of biomass. Occurrence was nearly 80% at Station A but only 33 and 20% at Stations B and C, respectively. Based on the sample from Station A, utilization was greatest by smaller catfish; 75-98% by fish of 150-199 mm TL compared to about 50% by fish of 200-299 mm TL. Mean individual weights of chironomids were 1-3 mg. Nearly all odonate larvae were damselflies of the genus Hetaerina, although a very few gomphidae (dragonflies) were encountered. Overall occurrence was about 64% but differed among sites: 75%, 0%, and 33% at Stations A, B, and C, Cl) uj LLJ respectively. Odonate contribution to total biomass was

< UJ nearly 16%, due largely to their importance at Station A. CC 2 LL < LU = Utilization of these relatively large insects (mean individual cn COD CI) < c) CC u LIJ cc E weights of 10-46 mg) was 100% by fish of 200-299 mm TL but < LI CC < only 13% by fish of <100 mm TL; the relation between fish size and occurrence was approximately linear between these 0:1 Cl) 0 CL C.) LL < extremes (Fig. 3). Larger fish ate the largest odonates; mean Figure 1. Mean percentage frequency and wet weight individual weights of 10, 12, 38, and 46 mg were consumed by biomass of food items in channel catfish fish of mean lengths of 121, 169, 269, and 338 mm, stomachs (N = 151) from the Coachella respectively. These were the only insects which clearly Canal, California. showed this relationship. •

ISSUE 3, 1981 FOOD OF CHANNEL CATFISH 93

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Figure 2. Mean percentage of wet weight biomass of Figure 3. Mean percentage frequency of occurrence of food items in channel catfish stomachs, by food items in channel catfish stomachs, by size group, from three stations in the size group, from 3 stations in the Coachella Coachella Canal, California. (+ indicates Canal, California. (+ indicates less than less than 0.5%.) 0.5%.)

Aquatic Lepidoptera larvae, Parargyractis confusalls, were numbers = 3.56), one catfish (256 mm TL) contained 167 in almost 62% of stomachs and accounted for 1.2% of total Nectopsyche sp. individuals. Their contribution to total biomass. Utilization was highest at Station A and lowest at biomass was small except among larger fish (>200 mm TL) at Station B. Frequency of occurrence was about 50% in smaller Station A. Mean individual weight of Nectopsyche sp. fishes (<150 mm TL) but 80-89% among fish of >150 mm (including case) was 6 mg. TL. Mean individual weights (3-6 mg) were similar to S. utico. Crayfish, Procambarus clarki, were in only a few stomachs Ephemeroptera nymphs, Baetis sp., were in about 18% of (3% of total) and in small numbers (1-3 per stomach). all stomachs and had a frequency of occurrence ranging from Utilization was greatest (up to 20%) by larger catfish, but their 13% at Station A to 60% at Station B; however, mean numbers contribution to total biomass was small. were low (0.15-0.43 per stomach). The contribution of Baetis sp. to total biomass was small, 10 mg overall. Utilization of Fish accounted for only 3% of the overall diet. Threadfin Baetis sp. was greatest by fish of 200-299 mm TL. shad, Dorosoma petenense, remains were found in two catfish Nectopsyche sp., a cased leptocerid caddisfly, occurred in at Station A, one (TL = 252 mm) contained scales and bone more than 26% of stomachs. Although generally in small fragments, the other (TL = 394 mm) contained two entire 94 JOURNAL OF THE ARIZONA-NEVADA ACADEMY OF SCIENCE VOL. 16

shad (TL = 95 and 138 mm) which comprised 77% of the gut of no other studies which have found this insect in catfish contents of that individual. diets, nor as an important component in the diet of any North A filamentous alga, Cladophora glornerata, was only in American fish (see Carlander 1969, 1977). Threadfin shad catfish from Station A where it had about a 10% frequency of were abundant in the canal (Minckley 1981b) especially at occurrence and accounted for nearly 17% of the total biomass. Station A; however, channel catfish made little use of that Algae were important only the in larger fish (TL>300 mm), resource. Kimsey et al. (1957) reported a similar relationship where algae occurred in 88% of guts and contributed 54% to at Palo Verde Lagoon on the lower Colorado River. Asiatic biomass. clams were a relatively important food of channel catfish from The intestinal contents of 20 catfish (TL = 101-322 mm) the Sacramento-San Joaquin Delta, California (Turner 1966) contained food items of the same nature and proportion as and from the lower Colorado River (Minckley 1981a), yet stomachs. One catfish (TL = 256 mm) intestine contained rare in fish from the Coachella Canal where they were the most shell fragments of Asiatic clam, Corbicula fluminea. abundant benthic invertebrate on natural substrates (Marsh DISCUSSION. -The results of this study compare favorably and Steinmetz 1981). with others (Table 2, see also Carlander 1969) indicating that As increasing kilometers of earthen canals are lined with channel catfish are both omnivorous and opportunistic. It is concrete in the interest of water transport efficiency, it has notable that my results are most similar to those of Dill (1944) been hypothesized that populations of invertebrates such as for another California canal. The abundance of Lepidoptera net-spinning caddisflies and aquatic Lepidoptera may increase and Trichoptera larvae on concrete surfaces in the Coachella substantially (Marsh and Steinmetz 1981). These increases Canal (Marsh and Steinmetz 1981) probably accounts for may be accompanied by population increases of those canal their predominance as food. Although Lepidoptera larvae fishes, including channel catfish, which use these insects as a appeared to provide a relatively small biomass for channel primary food resource. Such modifications may thus enhance catfish, their high frequency of occurrence is unusual; I know recreational fisheries supported by artificial waterways.

Table 2. Comparative data on percentage frequency occurrence of foods in channel catfish stomachs.

Authority and Locality Present Turner (1966) Jearld and study Dill (1944) Sacramento- Brown (1971) Minckley Coachella Irrigation San Joaquin Delta, CA L. Carl (1981b) Lower Food item Canal, CA Canal, CA <20 cm FL >20 cm FL Blackwell, OK Colorado River Oligochaeta 1.5 Mysidacea 13.8 13.3 Isopoda 2.6 1.1 0.1 Amphipoda 93.9 80.0 Decapoda 3.3 20.0 2.9 24.9 Ephemeroptera 17.9 2.6 9.1 Odonata 64.2 39.5 0.1 Trichoptera 99.3 47.4 Lepidoptera 61.6 Coleoptera 1.2 Diptera 70.9 89.5 26.5 6.7 67.2 5.1 Other insects 14.0 4.4 6.7 1.2 Mollusca 0.6 20.0 0.1 29.2 Fish 1.3 2.6 13.3 12.1 18.9 Fish eggs 0.6 Terrestrials 36.8 0.6 Filamentous algae 7.9 2.6 Benthic algae 8.0 Plant material 21.1 1.0 40.9 Detritus 31.6 4.6 32.9 Other 2.6 0.6 6.7 1.4

Percentage empty 1.3 5.0 10.8 34.7 34.7 16.1 Number of stomachs 153 40 203 23 196 137 Mean fish length (mm) 158 155 121 331 - Range in length 75-415 79-269 40-530 170-840 236-737 ISSUE 3, 1981 FOOD OF CHANNEL CATFISH 95

LITERATURE CITED MILLER, E.E. 1966. Channel catfish. In A. Calhoun, Editor. Inland Fisheries Management, pp. 440-463. California CARLANDER, K.D. 1969. Handbook of Freshwater Fishery Department of Fish and Game, Sacramento, California. Biology. Volume I. Iowa State University Press, Ames, MINCKLEY, W.L. 1981a. Trophic interrelationships among Iowa. 752 pp. introduced fishes of the lower Colorado River, southwestern 1977. Handbook of Freshwater Fishery Biology. United States. California Fish and Game. 68(2):78-79. Volume II. Iowa State University Press, Ames, Iowa. 1981b. Fishery inventory of the Coachella Canal, 431 pp. southeastern California. Final report, U.S. Bureau of DILL, W.A. 1944. The fishery of the lower Colorado River. Reclamation, Boulder City, Nevada. Purchase Order California Fish and Game 30(3):109-211. Number 1-01-30-04780. Arizona State University, Tempe, Arizona. ii + 25 pp. JEARLD, A., JR. and B.E. BROWN. 1971. Food of the TURNER, J.L. 1966. Distribution and food habits of ictalurid channel catfish (Ictalurus punctatus) in a southern Great fishes in the Sacramento-San Joaquin Delta. In J.L. Turner Plains reservoir. American Midland Naturalist 86 (1):110- and D.W. Kelley, Editors. Ecological Studies of the 115. Sacramento-San Joaquin Delta, Part II, Fishes of the Delta, KIMSEY, J.B., R.H. HAGY, and G.W. McCAMMON. 1957. pp. 130-143. Fish Bulletin 136, California Department of Progress report on the Mississippi threadfin shad, Fish and Game, Sacramento, California. Dorosoma petenense atchafaylae, in the Colorado River for U.S. FISH AND WILDLIFE SERVICE. 1981. Special report 1956. California Department of Fish and Game, Inland on distribution and abundance of fishes of the lower Fishery Administrative Report Number 57-23. 48 pp. Colorado River. U.S. Fish and Wildlife Service, Ecol. Serv., MARSH, P.C. and C.R. STEINMETZ . 1981. Benthic inver- Phoenix, Arizona. Final Report. Contract Number tebrates of the earthen Coachella Canal, California. 9-07-03-X0066, to U.S. Bureau of Reclamation, Ecol. California Fish and Game. In press. Serv. Phoenix, Arizona. iv + 157 pp.