ECOLOGY OF SHEEPSCOT RIVER ESTUARY SPECIAL SCIENTIFIC REPORT-FISHERIES No. 309 UNITED STATES DEPARTMENT OF THE INTERIOR FISH AND WILDLIFE SERVICE United States Department of the Interior, Fred A. Seaton, Secretary Fish and Wildlife Service, Arnie J. Suomela, Commissioner ECOLOGY OF THE SHEEPSCOT RIVER ESTUARY By Alden P. Stickney Fishery Research BiolOgist Bureau of Sport Fisheries and Wildlife Special Scientific Report- - Fisheries No. 309 Washington, D. C. May 1959 Librarr cf Conpress cat log curd fo~ his! ublica ion: Stickney, Alden P Ecology of the. heepscot Hi\' r (' tlWI'.\ ,Ya hina1011. T. D pt. of th Int rio!', Fi h nnd Wildlifl' , Pl'vicf', JI ;,0. iv, 21 p. llJu" map, flill!:r.. :!7 I'lIl II '1111 "'( 'nldi filII rI­ II her! ,no. 3(YJ) Bibliography: p. 20--21. 2 Ecolo::(v - ~[nlnp -:11 ' nlv r. I Title. (:-:; rles: C, f 1"11 IIrlli Wllellle, n In', In) I n Illc report-Il . herle , no 3tY.)) lnt ,j!)-~ 4 U. Dept. of th 1 nterlM. Llhr ry for Library of ongre.· Library of Congress catalog card for the Fish and 1; 'ildlife Service serial, 3pecial Scientific Report--Fisheries' U. S. Fi8h and Wildlife Service. Special scientific report: fisheries. no. 1- (Washington] 1949- no. iIlus., maps, dlagrs. 27 CIll. Supersedes in part the Service's Special sclentific report. 1. Fisheries-Research. SH11.A335 639.2072 59-60217 Library of Congress i1 CONTENTS Page Introduction ..... 1 Methods and materials 1 Geography .... 1 Hydrography . 3 Bottom sediments . 6 Tides and currents 6 Plankton ..... 9 Other populations . 9 Summary ..... 13 Literature cited . 20 Acknowledgments 21 ABSTRACT Three Fish and Wildlife Service and three State of Maine organiza­ tions collaborated on a comprehensive study of the ecology of the Sheep scot River estuary. This paper gives background material to introduce papers to follow by describing the physical, and biological characteristics of the estuary: Its geography, hydrography, bottom sediments, plankton com­ position and distribution, and higher animals and plants in the several habitat zones. Lists of the common aquatic animals and plants are included. iii Tidal falls at Sheepscot Village. Top: From an old photograph (circa 1900) showing one-time dam and tide gates. Tide is flooding. Bottom: Appearance of the falls at the present time. The view is ~rom a lower elevation. Tide is ebbing. iv ECOLOGY OF THE SHEEPSCOT RIVER ESTUARY In 1954 the Atlantic salmon research of (Oxner, 1920) and, where less accuracy was the U . S. Fish and Wildlife Service was oriented permissible, by means of specially calibrated to include a study of the ecological complex in a hydrometers. Temperatures were taken with a salmon river and its estuary. The project has mercury thermometer directly in the sampling been coordinated with the regular activities of bottle. ,As the time required to raise the bot­ State and Federal agencies concerned with the tle from the deepest water sampled was only a study of certain estuarine species and has been few seconds, change in temperature within the concentrated in a single river, the Sheepscot, bottle was disregarded. near Boothbay Harbor, Maine. Plankton was collected by two methods: Cooperating on this project are the Clam vertical hauls from bottom to surface with a Investigations, the Atlantic Herring Investigations, 1/2 -meter #2 silk plankton net and four -minute and the Atlantic Salmon Investigations of the U.S. surface tows with a Clarke-Bumpus plankton Fish and Wildlife Service; and the Department of sampler equipped with a # 10 silk net. Currents Sea and Shore Fisheries, the Department of In­ were measured according to a method described land Fish and Game, and the Atlantic Salmon by Pritchard and Burt (1951), in which a weighted Commission of the State of Maine. current cross is suspended at various depths and the wire angles resulting from the drag of The Sheepscot River was selected as a the current are measured to compute the direc­ suitable study area as it was convenient to a well­ tion and velocity of current. equipped fishery laboratory in Boothbay Harbor where personnel of four of the cooperating agen­ Fish were collected by means of gill nets cies were stationed; in addition, studies were and seines of several sizes, traps, fyke nets, already in progress on several economically and a small otter trawl. Intertidal invertebrate important species in that area, such as herring, populations were sampled by removing a 0.1 M2 alewife, smelt and clams. quadrat from the sediment to a depth of 10 centi­ meters. The material was then sieved through The Sheep scot River itself is not an im­ a 14 x 16 mesh-per-inch plastic screen. Sub­ portant salmon stream, but it does support tidal populations were sampled with a 0.1 M2 small natural runs of these fish and is regularly Petersen -type grab and similarly sieved. These stocked with hatchery-reared young. procedures were supplemented by numerous field observations and hand collections. A The purpose of the present report is to counting weir was constructed near the head -of­ give a comprehensive description of the study tide in the river to obtain information on the area to provide a background for other more movements of salmon and other anadromous fish. detailed reports covering specific problems. Stomach analyses were made on numerous fish It will also serve to complement the report of and some birds to aid in the study of certain Bryant (1956) which described the fresh -water food relationships. part of the river. Geography Methods and materials The Sheep scot River is a stream of mod­ A series of stations was first established est size !!which originates in the low uplands where regular observations were to be made, between the Penobscot and Kennebec valleys and (fig. 1). Water samples were collected at these flows generally southward to the Gulf of Maine. stations with a Kemmerer sampling bottle. Salinities were determined by titration with ij A description of the river proper may be silver nitrate according to Knudsen's method found in Bryant, 1956. See list of literature cited. 1 SCALE o 2 3 4 NAUTICAL MILES N o GULF OF MAINE ! Figure 1. - -Outline chart of the Sheepscot area showing the locations of principal geographic features, water masses, and sampling stations (numbers in circles). 2 Where it intersects the coastline it forms a deep, being greatest at the time of the spring thaw in narrow embayment superficially resembling a April or after heavy rains, and lowest during fjord. The valley, however, is river cut rather August and September. The salinity of the than glacier cut (Johnson, 1925) and has no sill estuary varies accordingly. at its seaward end. It is a typical submerged or "drowned" river valley. The size of this Tidal variation in salinity depends on portion of the estuary relative to the size of the the stage of the river and the particular locality, river itself is so large that it is not, strictly but fluctuations between high and low tides often speaking, an estuarine environment. For the exceed 15 0/00 in much of the upper estuary. purposes of this discussion, therefore, it will Seasonally, at a given location and tidal stage, be referred to as the lower estuary and distin­ salinity varies by about 15 to 20 0/00, as can guished from the upper or true estuary, which be seen from Station 13 in fig. 3. occupies a shallow valley about five miles long from the river mouth to the upper end of the In comparison, the lower estuary is lower estuary. The town of Wiscasset, Maine characterized by: deeper water, smaller tidal and the U.S. Route 1 highway bridge form a exchange ratiO, higher and less variable salinity, convenient dividing line between the two. and a narrower range of temperatures. Dilution by the Sheepscot River is rapidly attenuated be­ The lower estuary ranges from about 60 low Wiscasset and is hardly distinguishable five meters in depth at its seaward end to about 20 miles south of that town where, due to the nar­ meters at its upper end. For the most part its rownes s of the basin, swift currents mix the shores are steep and rocky. The upper estuary diluted surface water with the highly saline deeper is much shallower, with a channel from 1 to 10 layers. The mixed water extends southward to meters in depth at mean low water and bordered the region opposite the entrance of the Sasanoa by extensive mud flats and salt marshes. About River near Station 3 where the surface water is midway along this upper estuary at Sheepscot again diluted by an influx of low salinity water Village is a constriction between two headlands from the Kennebec. The area thus influenced where a transverse ledge of rock tends to hold extends southward along the western shore of back the water above it, creating a waterfall on the lower estuary to the Gulf of Maine. the ebbing tide. At one time a mill dam was erected at this site. There are other constric­ Below a depth of ten meters water of tions at several places in the estuary where rather uniformly high salinity extends the entire currents are rapid but without falls. There are length of the lower estuary. Fig. 2 shows the two major tributary branches to the upper estu­ vertical distributions of salinity on a longitudinal ary: Marsh River and Dyer River. Both are section of the estuary from the Gulf of Maine to largely tidal but are fed by streams. Wiscasset as it appeared on a typical spring day (showing the effect of the spring runoff) and on As can be seen in fig.