Fish assemblage structure in an intermittent Texas stream.
Intermittent streams are unique habitats essential to the ecosystems of the southern Great Plains, a region of the United States where perennial streams are uncommon. Despite this, few studies have been conducted on the fish assemblage structure of intermittent streams, particularly in Texas (Zale et al., 1989). Differences in ecological conditions among intermittent prairie streams may be as great as those between prairie and upland streams. Accordingly, basic descriptions and comparisons of biotas are recommended as necessary for future investigations of these habitats (Matthews, 1988).
This study was conducted to examine the fish assemblage structure of Sister Grove Creek, an intermittent stream in north-central Texas. Specific objectives were: 1) to describe the fish species composition of Sister Grove Creek, and 2) to examine spatial variation in fish assemblage structure. Fish assemblages were defined as all species collected at a site.
Sister Grove Creek has a drainage area of 215.3 square kilometers in Grayson and Collin counties, Texas. Approximately 60 kilometers long, Sister Grove Creek empties into Lake Lavon, a 9000-hectare impoundment near McKinney, Texas. The study area included the entire length of the stream from the headwaters to the mouth. Stream width at normal flow ranged from 3.5 meters in the headwaters to 7.5 meters in the middle reaches. Although the mouth of Sister Grove Creek maintained a defined channel, particularly during low flow, its extended floodplain (about 50 meters wide) graded into Lake Lavon, forming the Sister Grove Creek arm of the lake. Primary substrate was clay throughout much of the stream from the mid-reaches to the mouth. In headwaters, substrates were dominated by sand, pebbles, and limestone bedrock. Data on stream discharge were obtained from a U. S. Geological Survey gauging station (no. 08059400) located about mid-reach on Sister Grove Creek and indicated that average annual discharge from 1975 to 1985 was 1.26 cubic meters per second.
MATERIALS AND METHODS
Collections were made monthly from August 1988 to July 1989 by seining in daylight at eight locations (Fig. 1) along the stream, using a 0.5-centimeter mesh seine (4.25 meters by 1.55 meters). The 0.5-centimeter mesh allowed capture of fish as small as 15 millimeters standard length, but permitted postlarvae and small young-of-year to escape. A longitudinal reach of about 100 meters was seined at each site for approximately 45 minutes. Every effort was made to sample all possible habitats.
Spatial variation in the fish fauna of Sister Grove Creek was examined using principal components analysis. Catch data for each taxon were compiled by site. Only the 14 numerically dominant taxa were included to prevent uncommon taxa from having a disproportionate effect. Shannon-Wiener diversity (H') was calculated at each site using the formula
H' = [s.summation over (i=1)] ([p.sub.i]) ([log.sub.e] [p.sub.i]),
where s = number of different taxa and p = proportion of the total number of taxa in the ith taxon. Principal components analysis was conducted using SAS (SAS Institute Incorporated, 1985). Diversity was conducted using Ecological Analysis Software (Ekblad, 1989).
A total of 34 fish taxa (including 7099 individuals) was collected from August 1988 to July 1989 (Table 1). No collections were made in May 1989 as discharges greater than 55 cubic meters per second made field work impossible. Cyprinella lutrensis, Gambusia affinis, Pimephales vigilax, Menidia beryllina, and Fundulus notatus were the five most abundant taxa collected, respectively, comprising 79 percent of all individuals obtained. Species diversity for Sister Grove Creek was 2.28.
Number of taxa ranged from 10 at site 4 to 26 at site 2 (Table 2). Diversity also was lowest at site 4 and greatest at site 2. Fundulus notatus was the most abundant species in the headwaters, comprising at least 41 percent of the total number of individuals collected per site at sites 6, 7, and 8. Gambusia affinis was the dominant taxon in the midreaches, representing 34 to 56 percent of the total number of fish caught per site at sites 3, 4, and 5. Cyprinella lutrensis and M. beryllina were the most abundant species collected at sites 1 and 2, respectively.
Principal component analysis of the fish fauna of Sister Grove Creek revealed differences in fish assemblage structure among sites. The first two components accounted for 61 percent of the total variation. In an ordination of these components, there was no overlap among two groups, with separation of these groups primarily along the first principal component (Fig. 2). Fish assemblage structure at sites 4, 5, 6, 7, and 8 were similar and differed from that of sites 1, 2, and 3. Correlations of the first component and abundance of each taxon indicated that differences between these groups were largely the result of greater catches of L. humilis, P. annularis, and L. macrochirus at sites 1, 2, and 3 (r > 0.60, P < 0.05). Correlations of the second component and catch of F. notatus and hybrid sunfish (Lepomis sp.) indicated greater catches of these taxa at site 3 than site 1 (r > 0.60, P < 0.05). Catch of M. beryllina was negatively correlated with this component and corresponded to high catches of this species at site 1 (r < - 0.60, P < 0.05).
[FIGURE 1 OMITTED]
The fish fauna of Sister Grove Creek was similar to fish communities in other intermittent prairie streams. Zale et al. (1989) in a review of studies of fishes in intermittent prairie streams, indicated that the most common fishes included C. lutrensis and F. notatus, with numbers of fish taxa for intermittent streams in Texas ranging from six to 46. Matthews et al. (1988) reported the occurrence of 30 fish taxa for Brier Creek, a prairie-margin stream in south-central Oklahoma. The fish fauna of Sister Grove Creek was dominated by high abundances of relatively few species, characteristic of intermittent streams (Zale et al., 1989). Data collected in this study suggested that Sister Grove Creek supported a viable fish fauna typical of prairie intermittent streams.
Fish species diversity and richness were greatest for lower reaches of Sister Grove Creek. Whiteside and McNatt (1972) observed low species richness in the headwaters of the Plum Creek drainage of south-central Texas relative to lower reaches. In a study of Brier Creek, it also was reported that species diversity and richness increased downstream (Smith and Powell, 1971). These authors reported that P. vigilax, C. lutrensis, L. cyanellus, L. humilis, L. megalotis, L. macrochirus, L. microlophus, and F. notatus were among abundant fishes collected in the intermittent reaches of Brier Creek. In lower perennial reaches emptying into Lake Texoma, the preceding species were collected as well as G. affinis, M. beryllina, D. cepedianum, D. petenense, Aplodinotus grunniens, M. chrysops, and P. annularis. These additional species were considered temporary inhabitants of the stream that entered it from the reservoir. Spatial patterns in fish assemblage structure reported by Smith and Powell (1971) for Brier Creek seemed to apply in general to Sister Grove Creek. Menidia beryllina, D. cepedianum, D. petenense, M. chrysops, and P. annularis were collected in the lower reaches of Sister Grove Creek and likely were itinerant inhabitants, migrating from Lake Lavon. The influence of species from Lake Lavon on the Sister Grove Creek fish fauna appeared to be extend no further upstream than site 3, a distance of 5.6 kilometers from the reservoir. However, in Sister Grove Creek, as in Brier Creek, the presence of a man-made reservoir exerted a definite influence on the fish fauna of a tributary stream.
[FIGURE 2 OMITTED]
Spatial patterns in fish assemblage structure corresponded to the geomorphology of the stream channel. Porous gravel substrate in the headwaters of Sister Grove Creek provided little refuge for fishes during periods of summer low flows and drought. However, clay and sand substrates in the lower reaches, particularly at sites 2 and 3, held water and allowed formation of large stable pools conducive to the survival of fishes during summer drought conditions. Studies have revealed that pools in intermittent streams can be important refuges for fish and a source of potential colonists (Evans and Noble, 1979; Matthews, 1987; Schlosser, 1987). Although 22 of the 46 species collected in Big Sandy Creek were taken in the headwaters, the authors suggested that this was due to the geomorphology of the stream channel that resulted in permanent pools upstream, rather than downstream. Geomorphology of the lower reaches of Sister Grove Creek conducive to the formation of pools during low water may have been an important factor influencing fish assemblage structure in this part of the stream.
Intermittent streams generally are regarded as poor habitat for fish owing to the instability of the flow regime and, therefore, have received little consideration in land-use planning. Unfortunately, many intermittent streams have been modified by such activities as channelization, grazing, construction of headwater impoundments, and effluents (Zale et al., 1989). Knowledge of fish species composition, spatial patterns of fish assemblage structure, and extent of available pool habitat are critical to an understanding of the ecological functioning of these important ecosystems and should not be neglected from future land-use planning efforts.
Table 1. Species composition and percent abundance of 7099 fishes collected in Sister Grove Creek, Texas, from August 1988 to July 1989. Species N Percent Cyprinella lutrensis 1583 22 Gambusia affinis 1068 20 Pimephales vigilax 1041 15 Menidia beryllina 934 13 Fundulus notatus 595 9 Lepomis sp. 187 3 Lepomis macrochirus 173 3 Lepomis megalotis 169 2 Dorosoma cepedianum 160 2 Lepomis humilis 151 2 Dorosoma petenense 149 2 Pomoxis annularis 127 2 Lepomis cyanellus 65 1 Micropterus punctulatus 59 1 Morone chrysops 31 <1 Percina macrolepida 31 <1 Ictalurus punctatus 29 <1 Etheostoma gracile 11 <1 Notemigonus crysoleucas 10 <1 Cyprinus carpio 10 <1 Percina caprodes 10 <1 Minytrema melanops 9 <1 Lepomis gulosus 7 <1 Ictalurus natalis 7 <1 Noturus gyrinus 6 <1 Aplodinotus grunniens 5 <1 Pimephales promelas 5 <1 Etheostoma chlorosomum 5 <1 Lepomis microlophus 4 <1 Ictalurus melas 3 <1 Pomoxis nigromaculatus 2 <1 Pylodictus olivarus 1 <1 Etheostoma spectabile 1 <1 Carpiodes carpio 1 <1 Table 2. Number of fish taxa collected, species diversity (H'), most abundant species, and percent abundance at each of eight sampling locations along Sister Grove Creek. Collections were made from August 1988 to July 1989. Number Diversity Most abundant Site of taxa (H') species Percent 1 22 1.54 Cyprinella lutrensis 41 2 26 2.35 Menidia beryllina 26 3 24 2.19 Gambusia affinis 34 4 10 1.17 Gambusia affinis 56 5 11 1.49 Gambusia affinis 54 6 12 1.37 Fundulus notatus 41 7 15 2.11 Fundulus notatus 41 8 16 1.79 Fundulus notatus 46
P. Sollberger, D. Partridge, and G. Phillips, III, provided assistance in the field. W. Matthews provided valuable comments in the development of the manuscript as well as help in the field. Funding for this study was provided through a grant from the North Texas Municipal Water District.
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MICHAEL R. MEADOR, BRUCE E. ARAMBULA, AND LOREN G. HILL
University of Oklahoma Biological Station, Kingston, Oklahoma 73439
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|Author:||Meador, Michael R.; Arambula, Bruce E.; Hill, Loren G.|
|Publication:||The Texas Journal of Science|
|Date:||May 1, 1990|
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