Evaluation of Three Types of Artificial Habitats for Fishes in a Freshwater Pond in Maine, Usa
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BULLETIN Or MARINE SCIENCE. 55(2-3): 1149-1159. 1994 EVALUATION OF THREE TYPES OF ARTIFICIAL HABITATS FOR FISHES IN A FRESHWATER POND IN MAINE, USA John R. Moring and Peter H. Nicholson ABSTRACT Three types of artificial structures (brush bundles, cinder blocks, tire bundles) were studied along transects in Lac D'or, a boreal, freshwater pond in central Maine. Observations were made of 1,397 adult and juvenile fishes by means of 18 dives during the day and 6 dives during the night in 1990. Cover attracted the five species of fishes in the pond (pumpkinseed, Lepomis gibbosus; chain pickerel, Esox niger; brown bullhead, Ameiurus nebu/osus; common shiner, Luxi/us comutus; and golden shiner, Notemigonus crysoleucas). Numbers of fishes were significantly higher in areas with artificial cover (70% of fishes, average counts pcr transcct), or in areas with natural weed beds (29%) than in areas without cover «1%). Pumpkinseeds were distributed about equally in areas with tire bundles (38%), cinder blocks (34%), and brush bundles (28%), whereas golden and common shiners were attracted pri- marily to brush bundles (62%). Numbers of fishes associated with artificial habitat werc significantly higher at night. Common and golden shiners occupied locations on the periphery of structures, whereas pumpkinseeds frequently inhabited recesses of cinder blocks and brush bundles. Associations with artificial habitat decreascd rapidly in Octobcr when water tcm- perature declined to below 12°C, By early November, as water temperatures decreased to 7°C, fishes moved to the bottom, away from cover, and markedly reduced their movements. Artificial habitats were re-examined in June 1991 following winter ice cover. All structures remained intact, except several branches from submerged brush bundles had been removed by animals, probably beaver Castor canadensis (Castoridae). Although artificial habitat may only serve to redistribute fishes in a lakc or pond, such structures arc rccommendcd as a long-term option for freshwaters where cover limits carrying capacity of fishes. Artificial habitat has long been used by management biologists to improve local sportfisheries by providing cover and protection for fishes and attachment sites for macroinvertebrates and other prey (Wege and Anderson, 1979; Moring et aI., 1989), although the magnitude of the added food organisms is not always clear (Bohnsack et aI., 1991). Both predatory and prey fishes are attracted to artificial reefs (Wege and Anderson, 1979) and such concentrations of fishes, in turn, attract anglers (Polovina, 1991). Although most artificial reefs have been constructed in marine waters, fresh- water reefs have been utilized since before the 1930s (Stone, 1985). Initially, these were "brush shelters." During the 1930s and 1940s, the State of Michigan placed piles of brush in numerous lakes (Hubbs and Eschmeyer, 1938; Rodeheffer, 1939, 1945). Other types of artificial material, such as submerged pulpwood and other woody debris (Moring et aI., 1989), plastic "trees," "lily pads," and tubes (1. Warnecke, Arizona Game and Fish Department, Phoenix, Arizona, unpubl. data) and rocks to increase spawning areas (Trendall, 1988) have also been introduced to freshwater environments. In recent years, logs (48%), brush (27%), and tires (21 %) have been the most common materials introduced to freshwater lakes (Sport Fishing Institute, 1984). Most reefs have been constructed in the South and Midwest as attractants for black basses and other centrarchids and for catfishes (Ictaluridae). But, evaluations of this management technique in freshwater ponds of boreal waters have been 1149 1150 BULLETIN OF MARINE SCIENCE, VOL. 55, NO. 2-3, 1994 limited (Haley et aI., 1987), The only study of artificial structures in Maine (with only limited analysis) occurred in the early 1970s, in Sand Pond, near Baldwin (DeRoche, 1973). Natural materials tended to attract largemouth bass (Mierop- terus salmoides), yellow perch (Perea fiaveseens), and pumpkinseed (Lepomis gibbosus), Waters of northern New England have long been managed primarily for sal- monid fishes. Yet, the recent increase in popularity of fishing for black basses (Hartley and Moring, 1991), esocids (Herke, 1988), and other non-salmonid ga- mefishes in ponds and lakes of northern New England has led to the need for new management techniques to meet angler demands. The objectives of this study were to evaluate three types of artificial structures as attractors of freshwater fishes, and to evaluate seasonal changes in fish abundance. STUDY SITE Three types of artificial reef material were evaluated in Lac O'or, a freshwater pond that is part of Hirundo Wildlife Refuge, near Alton, Maine (Fig. I). Area and maximum depth of the pond are 1.4 ha and 3 m, respectively. Water temperatures during the growth season ranged from 7°C in November to 26°C in August. The non-natural impoundment has contained a fish community for almost 25 years and the fishes have been studied since 1972 (Moring, 1988). Five fish species are currently in the pond: pumpkinseed, chain pickerel (Esox niger), brown bullhead (Ameiurus Ilebulosus), common shin- er (Luxilus cornutus), and golden shiner (Notemigonus crysoleucas). The pond is ideally suited for studies of artificial habitat because it is logistically convenient, closed to angling, and protecled from wind and other disturbances. The fish fauna is representative of many non-salmonid fish communities of northern New England. METHODS AND MATERIALS Prior to the introduction of artificial structures in Lac O'or, four transects were established in the deepest part of the pond on 8 June 1990 (Fig. 1). Each transect was 46 m (150 ft) long and marked by a rope, staked at each end. Each metal stake was attached to a clear plastic fishing bobber with monofilament line so that the position of each transect could be easily located. At the same time, the markers were inconspicuous and did not detract from the natural setting of the refuge. Pre-introduction surveys were conducted on 15 and 18 June 1990 by two divers who swam along the length of each transect and counted all fishes within sight during two passes, one near the bottom and one just below the surface. Artificial habitats were introduced on 20 and 21 June 1990 to three of the transects; the fourth transect served as a control. One unit of each of three types of artificial structure was placed at 15 m intervals along the length of each transect: bundled tires, brush bundles, and concrete blocks. Thus, there were three replicates of each treatment. The sequence of structures was different for each transect (Fig. 1). Tire bundles consisted of four tires placed end-to-end in a "+" pattern. Holes were drilled in the tires, and each tire bundle was secured with coated rope. No anchor was necessary bccause the protected conditions in the pond prevented displacement by winds or waves. Two 4-tire units were placed in an interlocking pattern on each transect. Concrete cinder blocks (each 20 cm X 41 em, with two open recesses), were stacked three layers high, but in an irregular pattern on each transect rope. Brush bundles consisted of tripod wooden frames, each 1.2 m X 1.2 m X 1.2 m of 5 em X 10 em wooden boards, to which bundles of white birch and white spruce limbs were tied. The tripod frames were then anchored to the bottom. On each sampling date, divers swam slowly along the bottom and recorded the species, number, and approximate size of all fishes associated with each type of structure or along the control transect. Because of the limited visibility, the divers then made a second pass near the surface to record fishes associated with the upper parts of the structures. Graham (\992) found that counts of fishes made by divers near freshwater artificial structures can be influenced by diver disturbance and diver adaptation to low light levels. Our structures were in comparatively shallow water and, because divers approached laterally, along a transect, the effect of disturbance should be equal for each structure, thus making diver counts appropriate as a technique. Data were recorded on underwater writing slates. In addition to fish counts, water temperature, weather conditions, time, underwater (horizontal) visibility, and Secchi disc measurements from the surface were also recorded. Following the two dives prior to installation of structures, on 15 and 18 MORING AND NICHOLSON: FRESHWATER ARTIFICIAL HABITATS 1151 j, ':, DAM ,~i, '/,".' " ; •••• I r.',: . : ... J' ." :1 . ','. LAC O'OR ALTON I MAl NE SCALE; SOm .. -. , . Figure I. Lac D'or, Hirundo Wildlife Refuge, near Alton, Maine, and locations of three experimental transects (I, 2, 3) and a control transect (4) for studies in June-November 1990. C = cinder blocks; T = tires; and B = brush bundles, June 1990, 16 dives were made during the day at about weekly intervals from 21 June (4 h after final introduction of habitat) to 7 November 1990. In addition, six dives were made at night between 3 August and 16 October to count fish, Only two transects could be surveyed on two of the night dives because underwater lights failed (transects I and 2 on 3 August and 20 September). Sampling was terminated after the 7 November dive because the water temperature declined to 7°C and diving conditions became more difficult. A final daytime dive was made on 19 June 1991. The purpose of this dive was to examine the 1]52 BULLETIN OF MARINE SCIENCE. VOL. 55. NO. 2-3, 1994 60 • 150 0 0 • DAY 50 Z • o NIGHT 0 0 Z • DAY •... 120 0 0 o NIGHT u 0 :::> • ... + CONTROL .0 Q U ::;) 0 90 C '"•... '"•... 0 •• '"•... Z •.. • Z 30 ::) '" 0 :J Z 0 0 60 V • 0 0 U I •+ 20 •I • 0 + I • I 0 • 30 I 10 I 0• + I • I • 0 ++ • I JU JUL AUG 5EP OCT NOV JUN JUl AUG SEP I OCT NOV MONTH MONTH Figure 2.