Short Papers and Notes 143

Influence of Gradient on the Distribution of Fishes in Conowingo Creek, and

ABSTRACT: Twenty-sevenfish specieswere collected Methodsand Materials from Creek at eleven stations the Conowingo during Eleven stations were established along the course of summer,1970. most abundantwere Species Rhinichthys the creek and sampled during the Summer, 1970 (Fig. 1): atratulus, cornutus, Notropis Exoglossum maxillingua, Route 372 Buck, Pa.; Deaver Road Semotilus atromaculatus and commersoni. (1) bridge, (2) bridge, Catostomus Old Buck Scotland Road A rank correlationcoefficient matrix was School, Pa.; (3) bridge, Hop- Spearman's kins Mill Dam, Pa.; (4) Cardinal Road bridge, Old calculatedfor biologicaland physicalparameters. Distri- Black Bear Road butionof fishes relatedto widthand of the Conowingo School, Pa.; (5) bridge, appeared depth Bethel Church, Pa.; (6) Route 222 bridge, Goshen, Pa.; stream,but was most influenced by gradient. (7) Black Baron Road bridge, New Texas, Pa.; (8) Old Mill Road bridge, Pleasant Grove, Pa.; (9) Old Cono- Introduction wingo Road bridge, Oakwood, Md.; (10) 0.5 km up- stream of mouth of Pilot Ichthyological Associates since 1966 has conducted Conowingo Creek, Station, 90 m above first riffles from mouth of an intensive ecological investigation of Conowingo Res- Md.; and, (11) Pilot Md. ervoir, the lower , in relation to the Conowingo Creek, Station, Peach Bottom nuclear generating facility and Muddy Stations were sampled once with seine and once using Run pumped storage unit. The study of Conowingo an electrofishing unit powered by a Honda Model 300 Creek was initiated during the summer of 1970 to provide portable generator, except for Station 1 which was information on fish populations representative of Cono- sampled only once by electrofishing. Collections were wingo Reservoir tributaries. Water quality in Conowingo preserved in 10% formalin and stored in 40% iso- Creek was similar to that of other streams in southern Lancaster County. The area was intensively farmed, thus N contributed through runoff and erosion to eutrophication of the stream; however, water quality was not considered to be a significant factor limiting fish distribution. Industry was absent. Numerous studies (Shelford 1911; Thompson and 2 Hunt 1930; Luce 1933; Trautman 1942; Burton and Odum 1945; Huet 1959; Kuehne 1962; Larimore and Smith 1963; Ross 1969; and Lotrich 1973) have shown that the longitudinal succession of stream fishes may be correlated to a number of physical, chemical and biologi- cal factors. More recently, Moyle and Nichols (1973) applied multivariate analysis to determine which of 20 variables most influenced the distribution of fish associa- tions in streams of the Sierra Nevada foothills. The latter study re-emphasized the fact that individual environmen- Stal variables do not necessarily act independently. StudyArea Creek from the Conowingo originates springs along o south slope of Mine Ridge, east of Buck, Pennsylvania, 0o0 and flows approximately 24.9 km in Pennsylvania and 5.6 km in Maryland before its confluence with the Susquehanna River, Conowingo Reservoir, at Pilot Sta- tion, Maryland (Figure 1). Mine Ridge varies in eleva- tion from 213-244 m above sea level while the confluence Pennsylvanian is at 33.5 m. An outstanding feature of the stream is the steep gradient, 6.25 meters per kilometer (m/km) aver- Maryland age for the 30.5 km length, which dramatically increases 9 to over 26.5 m/km for the last 1.0 km. Conowingo Creek ,10 winds through the rolling Piedmont Upland Province of the Conowingo Appalachian Highlands, characterized by crystalline Dam (metamorphosed) rocks of Precambrian or Paleozoic origin; schist, serpentine, gneiss and quartzite are com- mon (Willard, 1970). Climax vegetation is oak-chestnut Fig. 1. Conowingo Creek drainage basin and location forest. Soils are podzolic. of stations 1-11. ChesapeakeScience Vol. 16. No. 1 June, 1975 144 Short Papers and Notes

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TABLE 2. Spearman's correlation coefficients* for factors influencing fish distribution in Conowingo Creek.

1 2 3 4 5 6 7

1. River km (Station) 1.00 (.0000) 2. Width .85 1.00 (.00 12) (.0000) 3. Depth .75 .78 1.00 (.0080) (.0049) (.0000) 4. Gradient -.03 -.45 -.43 1.00 (.9341) (.1672) (.1795) (.0000) 5. No. of Organisms -.33 .00 -.07 -.52 1.00 (.3272) (.9863) (.8322) (.0982) (.0000) 6. No. of Species .31 .61 .60 -.90 .54 1.00 (.6453) (.0437) (.0489) (.0003) (.0817) (.0000) 7. Diversity Indices .35 .67 .57 -.87 .51 .95 1.00 (.2985) (.0228) (.0664) (.0008) (.1072) (.0001) (.0000) * Number in parenthesis is the probability > IRI under the H,: R = 0 (d.f. = 11).

propanol. Stream gradients in meters per kilometer were 32 calculated between elevation intervals on topographic 28 maps scaled 1:24,000, 7.5 minute quadrangles. Diversity indices were calculated using the formula: 24 JeE H I x N! 20 N Loge ( x N,! x N,! x ... N E where: Lo \Ni! 12 N is the number of organisms in the collection; N,,N2, Ni are the number of organisms in 8 species one, two ..., etc.; and s is the number of 4 species in the collection (Pielou 1969). Because the data did not satisfy all of the assump- 0 2 4 6 8 10 12 14 16 18 20 22 tions of a normal distribution, a rank cor- Spearman's Number of Species relation coefficient matrix (Conover, 1971) was deter- 2. of the number of fish versus mined for river kilometer (station locality), gradient, Fig. Analysis species in meters kilometer for width, depth, number of specimens, number of species, gradient per Conowingo Creek, Md.-Pa. and diversity indices. Results were compared with the physical variables (river kilome- Twenty-one collections yielded 27 species and 1,817 ter, width, depth and gradient), showed that the effects of specimens (Table 1). No single species was common to physical parameters were interrelated. However, gradi- all stations. Exoglossum maxillingua, Notropis cornutus, ent was the parameter that most influenced the distribu- Rhinichthys atratulus and Catostomus commersoni were tion of fish in Conowingo Creek. The greatest number of each present at ten sample sites. Salmo trutta, Semotilus species in Conowingo Creek was found at gradients corporalis, Ictalurus nebulosus and Lepomis between 2.5 and 3.4 m/km. macrochirus were each collected from a single locality. Station locality (river kilometer) was correlated The most abundant species present was R. atratulus (542 highly with width (0.85) and depth (0.75), but had little specimens), followed by N. cornutus (142), E. influence on the number of taxa (0.31) or specimens maxillingua (137), Semotilus atromaculatus (120), and (-0.33) collected. Width and depth were highly cor- C. commersoni (103). related (0.78), but were of significantly less importance Gradient decreased in Conowingo Creek from the than gradient (-0.90) in influencing distribution of fish headwaters to the Maryland/Pennsylvania state line, but in Conowingo Creek (Fig. 2). increased substantially to the mouth thereafter. In- Numbers of each species collected per locality indi- creased gradient in the lower course was caused by the cated that Clinostomus funduloides and S. creek flowing through high bluffs bordering the Sus- atromaculatus were headwater species. In contrast, No- quehanna River, which has cut through the peneplain comis micropogon and Notropis rubellus were most terraces of the surrounding piedmont to the present base common in the lower course of Conowingo Creek. level. Rhinichthys cataractae and R. atratulus were collected in Results obtained by Spearman's rank correlation most of the survey area, but were more abundant in coefficient matrix (Table 2) when the total number of middle to headwater localities. Greatest numbers of organisms, total number of species, and diversity indices Campostoma anomalum, E. maxillingua, Notropis hud- 146 Short Papers and Notes

sonius, Notropis procne, Hypentelium nigricans, and that Cyprinus carpio, Notropis amoenus, Notemigonus Etheostoma olmstedi were collected near the middle of crysoleucas, Carpiodes cyprinus, Percina caprodes, and the survey area. Pimephales notatus was abundant only Percina peltata, which have been taken in Conowingo at Station 8, location of lowest gradient. Reservoir near the mouth of Conowingo Creek, may be Species succession in stream fishes is usually a factor found within the study area (particularly Station 11) at of species addition rather than one of replacement certain times of the year. Ictalurus punctatus entered (Sheldon, 1968; Lotrich, 1973). This was observed in Stations 10 and 11 from the reservoir in this manner, but Conowingo Creek where the number of species increased has not successfully traversed the swift currents to from three at Station 1 (headwaters) to 21 at Station 8. A populate upstream localities. Etheostoma zonale was sharp reduction in stream gradient occurred between recently collected from nearby Wissler's Run, a tributary these localities. Gradient increased and number of spe- of the lower Susquehanna River, Conowingo Reservoir. cies decreased downstream from Station 8. Its distribution was apparently enhanced by severe Larimore et al. (1952) depicted relative abundafice of flooding that accompanied Hurricane Agnes (T. W. four species of darters in Jordan Creek, Illinois, by Robbins, pers. commun.); other upper Susquehanna taxa percent catch of each species per locality. This approach may have spread similarly in distribution. was applied to Conowingo Creek data for the four most Many physical factors have been shown to influence abundant cyprinids: R. atratulus, N. cornutus, E. the longitudinal distribution of stream fishes. Most maxillingua and S. atromaculatus (Figure 3). In terms of factors are inseparable, each playing a significant role in relative abundance, R. atratulus decreased in abundance forming the specific microhabitat. However, as demon- and N. cornutus increased in abundance from headwaters strated by the results of this and other (Shelford 1968; to mouth. S. atromaculatus distribution was similar to Moyle and Nichols 1973) investigations, it is possible to that of R. atratulus although its abundance was consider- distinguish those factors most important. As indicated by ably lower. E. maxillingua showed preference for low this investigation, gradient could help explain the distri- gradient localities similar to those found at Stations 6-9. bution of many Pennsylvania fishes which have not been systematically studied since the early work of Fowler Discussion (1919). Additional species may occur in Conowingo Creek other than those collected. salmoides has Micropterus ACKNOWLEDGMENTS been reported (D. W. Daniels, pers. commun.). Also, the Pennsylvania Fish Commission has stocked Salvelinus Our gratitude is extended to Dr. John Cairns, Jr., fontinalis and Salmo gairdneri in the Pennsylvania Virginia Polytechnic Institute and State University, who portion of Conowingo Creek in recent years. It is likely reviewed the manuscript.

Grodient (mrn/km)

19.3 10.0 13.4 7.8 5.5 3.0 3.0 2.6 34 28.4 28.4 10 0 ...... i .,-...... 90 *i . ... :i-;c -...

0 0 ......

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0

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Station Fig. 3. Distribution (in percent) of the four most abundant minnows (Cyprinidae) collected in Conowingo Creek, stations 1-11, with gradients noted. (A: Exoglossum maxillingua; B: Semotilus atromaculatus; C: Rhinichthys atratulus; and D: Notropis cornutus). Short Papers and Notes 147

LITERATURE CITED PIELOU, E. C. 1969. An introduction to mathematical John & N.Y. BURTON,G. W., ANDE. P. ODUM.1945. The distribution ecology. Wiley Sons, Inc., 231p. Ross, R. D. 1969. evolution and fish distribu- of stream fish in the vicinity of Mountain Lake, Drainage tion in the southern of Vir- Virginia. 26(2):182-194. problems Appalachians Ecology 277-292. In P. C. Holt The distribu- CONOVER,W. J. 1971. Practical statis- ginia, p. (ed.), nonparametric tional of the biota of the southern tics. John Wiley & Sons, Inc., N.Y. history Appala- chians. Part I: Invertebrates.-Res. Div. FOWLER,H. W. 1919. A list of the fishes in Pennsylva- Monogr. nia. Proc. Biol. Soc. Wash. 32:49-73. 1, Va. Poly. Inst. & St. Univ., Blacksburg, Va. V. E. 1911. succession. Stream HUET, M. 1959. Profiles and biology of Western Euro- SHELFORD, Ecological I. fishes and the method of Biol. pean streams as related to fish management. Trans. physiographic analysis. Bull. 21:9-35. Amer. Fish. Soc. 88(3):155-163. A. L. 1968. KUEHNE, R. A. 1962. A classification of streams, SHELDON, Species diversity and longitudinal succession in stream fishes. illustrated by fish distribution in an eastern Kentucky Ecology 49(2):193-198. D. ANDF. D. HUNT. 1930. The fishes of creek. Ecology 43(4):608-614. THOMPSON, H., Ill. LARIMORE,R. W., Q. H. PICKERING,AND L. DURHAM. Champaign County, Illinois. Nat. Hist. Surv. Bull. 1952. An inventory of the fishes of Jordan Creek, 19(l):5-101. M. B. 1942. Fish distribution and abundance Vermillion County, Illinois. Ill. Nat. Hist. Surv. Biol. TRAUTMAN, Notes 29:1-26. correlated with stream gradients as a consideration in , AND P. W. SMITH.1963. The fishes of Cham- stocking programs. Trans. 7th N. Amer. Wildl. Conf. 7:211-224. paign County, Illinois, as affected by 60 years of B. 1970. summarized. stream changes. Ill. Nat. Hist. Surv. Bull. WILLARD, Pennsylvania geology Pa. 28(2):299-382. Publ. Geol. Surv., Educ. Ser. No. 4:1-17. LOTRICH,V. A. 1973. Growth, production, and commu- CHARLESH. HOCUTT' nity composition of fishes inhabiting a first-, second-, JAY R. STAUFFER2 and third-order stream of eastern Kentucky. Ecol. Ichthyological Associates Monogr. 4(3):377-397. Drumore, Pennsylvania 17537 LUCE, W. M. 1933. A study of the fishery of the Kaskaskia River. Ill. Nat. Hist. Surv. Bull. 20(2):71-123. 'Present address: Environmental Research & Tech- MOYLE,P. B., AND R. D. NICHOLS.1973. Ecology of nology, Inc., Concord, Massachusetts 01742. some native and introduced fishes of the Sierra 2 Present address: Department of Biology, Virginia Nevada foothills in Central California. Copeia Polytechnic Institute and State University, Blacksburg, 1973(3):478-490. Virginia 24061.

Abundance of Submerged Vascular Vegetation in the from 1966 to 1973

ABSTRACT: Surveys on the distribution and abun- Introduction dance of submerged vascular plants in the Rhode River This report presents data on the abundance of five showed that there was an irregular decline in the amount species of submerged vascular plants in the Rhode River of vegetation from 1966 to 1973, along with significant (Fig. 1), a subestuary of Chesapeak Bay, seven miles changes in species dominance. In 1966, redheadgrass south of Annapolis. Preliminary observations in the early (Potamogeton perfoliatus) and Eurasian watermilfoil 1960's indicated that the Rhode River had an abundant (Myriophyllum spicatum) were both very abundant with community of submerged macrophytes which was domi- lesser amounts of widgeongrass (Ruppia maritima), nated in the mid-60's by Eurasian watermilfoil (Myrio- horned pondweed (Zannichellia palustris), sago pondweed phyllum spicatum) and redheadgrass (Potamogeton (Potamogeton pectinatus), and elodea (Elodea perfoliatus). The former was part of an explosive growth canadensis). In 1967, all of these species declined substan- of watermilfoil which occurred throughout the upper Bay tially, and elodea disappeared entirely. In 1968, redhead- in the early 1960's and displaced much of the native grass and horned pondweed returned in substantial abun- vegetation (Bayley, Rabin and Southwick 1968; Elser dance, but they again declined in 1969 and virtually all 1966). submerged aquatics disappeared in 1970. In 1972, horned We began accurate field surveys of submerged vegeta- pondweed and sago pondweed reached an eight-year peak, tion in Middle, Back and Rhode rivers in 1966. In this but other species remained at very low levels. In 1973, all year, there was a prominent decline in the abundance and species were low, and a prominent lack of vegetation distribution of watermilfoil throughout the upper Bay, similar to 1967, 1970, and 1971 occurred again. Elodea probably caused by the interaction of milfoil disease and has not been seen in the Rhode River since 1966. We increased turbidity (Bayley et al. 1968; Elser 1967). In believe these changes represent a decline in environmental 1967, virtually all submerged vegetation disappeared in quality in the Rhode River that may have serious long- the Rhode River, a phenomenon called the "Rhode River range implications. evanescence" by Elser (1967). We established an annual ChesapeakeScience Vol. 16, No. 1 June, 1975