Comparisons are made of channel catfish in channeled and unchanneled sections of the Little Sioux River with regard to abundance, movement, and age and growth. Mean catches per unit effort of channel catfish were higher during May to October bi-weekly periods in the unchanneled section. Movement was predominantly downstream in both areas. In the unchanneled section 23.7% moved upstream, 69.6% moved downstream, and 6.7% were recaptured at their release site. In the channeled area 25.8% moved upstream, 39.8% moved downstream and 34.4% were recaptured at their release site. Due to the free exchange of catfish between both areas, growth rates were similar in both areas. The largest mean annual increment in both areas (4.42 inches) occurred in the second year

Welker, Bill D.

University of Northern Iowa

Proceedings of the Iowa Academy of Science Volume 74 Annual Issue Article 19 1967 Comparison of Channel Catfish Populations in Channeled and Unchanneled Sections of the Little Sioux River, Iowa Bill D. Welker Iowa State Conservation Commission Let us know how access to this document benefits you Copyright ©1967 Iowa Academy of Science, Inc. Follow this and additional works at: https://scholarworks.uni.edu/pias Recommended Citation Welker, Bill D. (1967) "Comparison of Channel Catfish Populations in Channeled and Unchanneled Sections of the Little Sioux River, Iowa," Proceedings of the Iowa Academy of Science, 74(1), 99-104. Available at: https://scholarworks.uni.edu/pias/vol74/iss1/19 This Research is brought to you for free and open access by the Iowa Academy of Science at UNI ScholarWorks. It has been accepted for inclusion in Proceedings of the Iowa Academy of Science by an authorized editor of UNI ScholarWorks. For more information, please contact scholarworks@uni.edu. Comparison of Channel Catfish· Populations tn Channeled and 'Unchanneled Sections of the Little Sioux River, Iowa BILL D. WELKER 1 Abstract. Comparisons are made of channel catfish in channeled and unchanneled sections of the Little Sioux River with regard to abundance, movement, and age and growth. Mean catches per unit effort of channel catfish were higher during May to October bi-weekly periods in the unchanneled section. Movement was predominantly downstream in both areas. In the unchanneled section 23.7% moved upstream, 69.6% moved downstream, and 6.7% were recaptured at their release site. In the channeled area 25.8% moved upstream, 39.8% moved downstream and 34.4% were recaptured at their rel~ase site. Due to the free exchange of catfish between both areas, growth rates were similar in both areas. The largest mean annual increment in both areas ( 4.42 inches) occurred in the second year. In recent years an increasing number of streams have been channeled to obtain better drainage or to prevent flooding of sur-rounding farmland. This channelization work causes radical changes in the environmen of existing fish populations and, in general, reduces the quality and quantity of fish habitat. Between 1962 and 1966 considerable data were collected from adjoining channeled and unchanneled sections of the Little Sioux River in western Iowa. Most of the data reported in this paper were collected during intensive field work in 1964. The Little Sioux arises in Jackson, Minnesota and flows south-westerly through Iowa for 221 miles before entering the Missouri River at River Sioux, Iowa. The United States Army Corps of En-gineers completed rechanneling the lower 35 miles in 1957 and built a low-head darn approximately 6 miles from the mouth in 1963. The unchanneled river is characterized by sharp bends, steep banks, deep-water areas around brush piles, and a mud bot-tom with scattered areas of sand or gravel. In contrast, the chan-neled section is generally straight, with a few wide sweeping bands and water depths uniform between banks. The study area included 35 miles of channelized and 30 miles of unchannelized river bed. Channel catfish are the most important game fish in both areas. METHODS AND MATERIALS Most channel catfish were taken in baited hoop nets; however, fish were collected with electro-fishing gear. During 1965 and 1966, 200-yard sections of channeled and unchanneled stream were enclosed with one-quarter-inch mesh block nets and treated 1 Biologist, Iowa State Conservation Comm.ission, Sioux City, Iowa. 99 1Welker: Comparison of Channel Catfish Populations in Channeled and UnchanPublished by UNI ScholarWorks, 1967Table 1. Total trap net days and mean catch of channel catfish per day for bi-weekly fishing periods in channeled and unchan-neled sections of Little Sioux River, 1964. May June July August September October Location 1-15 16-31 1-15 1-15 16-31 1-15 16-31 1-15 16-30 1-15 16-31 U nchanneled Trap days 12 42 9 13 12 19 30 16 24 35 17 Mean catch per d~ 22 26 15 33 22 15 19 17 26 63 8 Trap ays 38 61 4 35 51 42 35 18 19 10 9 Channeled Mean catch per dd; 3 8 7 18 10 10 18 11 49 6 2 Trap ays 7 12 16 8 15 14 23 Pool area Mean catch per day 11 25 76 308 72 95 32 ,_. o· O· >-! 0 ~ > > 0 > ti ti:! ~ ><: 0 l'rj [/'.) 0 ..... t'i' z Q ~ -t """ 2Proceedings of the Iowa Academy of Science, Vol. 74 [1967], No. 1, Art. 19https://scholarworks.uni.edu/pias/vol74/iss1/191967] CHANNELIZATION EFFECTS 101 with rotenone for removal of fish. The same areas were sampled with rotenone each year. Total lengths, weights and pectoral spines were collected from samples of all catfish. In 1964 channel catfish were tagged with internal body-cavity tags (Harrison, 1948) at four locations in channeled and unchanneled stream. ABUNDANCE Although several factors affect catch per unit effort (Ricker, 1958), these data can be used to measure the relative abundance of a fish population (Table 1). During 10 of the 11 bi-weekly fishing periods between May and October, 1964, more channel catfish were caught per trap net day in the unchanneled area than in the channeled section. Although fishing effort was much less intense during 1962, 1963 and 1965, catch per trap-net day was generally larger in the unchanneled area than in the channeled section. These data, collected between 1962 and 1966 indicate channel catfish are more abundant in the unchanneled section than in the channeled area between May and October. The most significant difference between the channel catfish populations in the two areas during late summer is the lack of catfish over 9 inches in the channeled area as indicated by roten-one sampling (Table 2). An important factor is the low water level during this period. Maximum depths in the unchanneled area during August and September are generally over 5 feet. It is difficult to find water over 2lf feet deep in most of the chan-neled area during this same period. Mean depth is often between H~ and 2 feet and uniform throughout the channeled section; therefore, the opportunity for larger catfish to move into deeper water during declining water levels in late summer is not present in the channeled area. Table 2. Number of different-sized channel catfish collected with roten-one from 200-yard sections of channeled and unchanneled river. 1965 1966 Location Date Young-of 5-9 Over 9 Date Young-of 5-9 Over 9 year inches inches year inches inches Unchanneled 8-31 2,813 10 21 Channeled 9-2 5 9-7 2,981 765 14 9-16 2,653 92 Few young-of-the-year catfish were collected by rotenone in the channeled area in 1965 (Table 2). Although field observa-tions indicated more spawning in the channeled area than these data indicate, there is no explanation for the few young-of-the-year caught since a "good kill" was indicated after renovation. 3Welker: Comparison of Channel Catfish Populations in Channeled and UnchanPublished by UNI ScholarWorks, 1967102 IOWA ACADEMY OF SCIENCE [Vol: 74 The large number of young-of-the-year catfish collected in th~ channeled area in 1966 is also not necessarily an indication of abundance. Movement of catfish over 6 inches (discussed later) in both the channeled and unchanneled sections was predominant-ly downstream and,often for a considerable distance. It is possible, therefore, that a significant portion of the young-of-the-year caught in the channeled area in 1966 moved downstream from the unchanneled section. Renovation in the channeled area in 1966 was conducted 2 weeks later than the 1965 renovation. This 2-week period may have allowed enough additional time in 1966 for .an influx of young-of-the-year catfish from upstream. The numbers of botlryoung-of-the year catfish and those over 9 inch-es caught in the unchanneled area did not vary greatly between 1965 and 1966. Bayless and Smith ( 1964) found a great reduction in both the total number and total weight of game fish after channelization of a North Carolina stream. The mean total number was re-duced from 1,231.3 fish per surface acre to 58.8 fish per surface acre; the mean total weight was reduced from 83.l pounds per surface acre to 2.3 pounds per surface acre. MOVEMENT During 1964, 10,025 tagged channel catfish were released in the lower 65 miles of the Little Sioux. The maj01ity of catfish re-captured over 2 miles from their release site moved downstream in both the channeled and unchanneled sections (Table 3). A considerably larger number moved downstream .over 2 miles in the unchanneled area than in the channeled area. This could be expected, however, since the unchanneled section is upstream· from the channeled area, thus allowing more catfish moving downstream in the unchanneled area to be caught. Recaptures downstream from the channeled area (Missouri River) were lim-ited to spnrtfishing. Disregarding local movement, 23.7% of re-caphires in the unchanneled section moved upstream, 69.6% moved downstream, and 6.7% were recaptured .at their release site. In the channeled area 25.8% moved upstream, 39.8% moved downstream, and 34.4% were recaptured at their release site. Table 3. Number of marked channel catfish recaptured in channeled and unchanneled sections and direction and mean distance travelled in miles. Location Unchanneled Channeled Total Upstream1 Downstreaml Local2 Number Mean distance Number Mean distance Number 49 12.0 206 27.8 100 52 15.4 70 19.2 142 101 13.7 276 , 25.6 242 1. Movement over 2 miles from release site. 2. Movement within 2 miles from release site. 4Proceedings of the Iowa Academy of Science, Vol. 74 [1967], No. 1, Art. 19https://scholarworks.uni.edu/pias/vol74/iss1/191967] CHANNELIZATION EFFECTS 103 Other evidence of downstream movement in the channeled area is the catch per unit effort data recorded at the pool area (Table 1). These data were collected from a location approx-imately 500 yards above the low-head dam. Although this loca-tion was in the channeled section, it was also in a pool area which extended upstream from the dam for approximately 1 mile. Mean water depth in this pool was generally 2 or 3 feet deeper than in the remainder of the channeled section during any part of the summer. Values for the number of channel catfish caught per trap net day were very similar in the pool and the remainder of the channeled section during July 16 to 31. However, during the next three bi~weekly fishing periods until 16 September, values in the pool rose dramatically from 25 to 308 fish per day while values for the remainder of the channeled area during these same periods only varied between 10 and 18 fish per day. From 16 September through 31 October, bi-weekly catch per effort values were larger in the pool area than in either the remainder of the channeled section or the unchanneled area. Since channel cat-fish could not move upstream over the dam after water levels declined in April, the apparent increase in relative abundance of channel catfish in the pool area during late summer was carnied by downstream movement. There appears to be no distinct, indi-vidual catfish population in either the channeled or unchanneled area, but rather, due to :extensive movement between areas, a single population inhabiting both areas. AGE AND GROWTH Since the body-spine relationship is subject to many variables, no growth correction factor was calculated to represent the body length at time of spine formation; therefore the calcul~ted lengths in Tables 4 and 5 should only be considered approximations. Several 6- 7- and 8-year-old catfish were caught in both the chan-Table 4. Avera~e calculated total lengths in inches at the end of each year o life from pectoral spine cross-section of channel catfish taken in 1964 from unchanneled sections of the Little Sioux River, Iowa. Age Year of life group Number 1 2 3 4 5 6 I 89 2.6 II 62 1.9 6.2 III 72 1.7 6.0 8.7 IV 77 1.9 6.3 9.0 10.7 v 76 2.0 6.1 9.0 10.8 12.4 VI 37 2.2 6.1 8.9 10.9 12.4 14.2 Average calculated 6.1 8.9 10.8 12.4 14.2 length 2.0 Average annual 2.0 4.2 2.7 1.7 1.5 1.8 increment 5Welker: Comparison of Channel Catfish Populations in Channeled and UnchanPublished by UNI ScholarWorks, 1967104 IOWA ACADEMY OF SCIENCE [VoL 74 Table 5. Average calculated total lengths in ~ches at the end of i:ach year of life from pectoral spine cross-sections of channel catfish taken in 1964 from channeled sections of the Little Sioux River, Iowa. Age group Number 1 I 51 2.3 II 23 1.9 III 26 1.9 IV 46 1.9 v 48 2.1 Average calculated length Avei:age annual 2.0 increment 2.0 2 6.1 6.3 6.2 6.2 6.2 4.2 Year of Life 3 4 8.6 9.0 10.8 9.1 11.l 8.9 10.9 2.7 1.9 5 12.4 12.4 1.4 neled and. unchanneled sections, however, due to difficulties in aging,.some of these fish were not included in these tables. Average calbulated lengths and average annual increments for each year . of life were very similar in both the channeled and unchanneled areas. This could be expected, however, considering the evidence indicating a single population inhabiting both areas. The largest annual increment in both sections ( 4.2 inches) oc-curred in the second year. ACKNOWLEDGEMENTS Tl;ie author wishes to thank Larry Geptner and the many other personnel of the Iowa State Conservation Commission who helped with the field work. Literature Cited Bayless and Smith. 1964. Effects of channelization upon the fish popula-tions of lotic waters in eastern North Carolina. Sport Fish. Bnlt No. 146. Harrison, Harry M. 1948. Returns from tagged channel catfish .in the Des Moines River, Iowa. Iowa Acad. of Sci. 60:636-644. ' Ricker, W. E. 1958. Handbook of computations for biological statistics of fish populations. Queen's Printer and Controller of Stationery. Ottawa, Canada. · 6Proceedings of the Iowa Academy of Science, Vol. 74 [1967], No. 1, Art. 19https://scholarworks.uni.edu/pias/vol74/iss1/19

Comparison of Channel Catfish Populations in Channeled and Unchanneled Sections of the Little Sioux River, Iowa

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Comparison of Channel Catfish Populations in Channeled and Unchanneled Sections of the Little Sioux River, Iowa

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