Enchanted Pond's Resident White Suckers

Abstract

During a September 1995 gill netting survey conducted on Enchanted Pond, a deep oligotrophic lake located in Somerset County, Maine, a sample of 228 white suckers (Catostomus commersoni Lacepede) was captured. All the fish were relatively small (between 45 and 247 mm). Other surveys on Enchanted Pond between 1979 and 1994 captured 81 white suckers, all less than 270 mm in length. It seemed likely that the white sucker population in Enchanted Pond was comprised of either stunted individuals, or of dwarf or pygmy forms. Stunting is caused by competition for limited food resources when a species is at high densities. When fish densities become very large, individual fish growth tends to lag and the size distribution of the population is uniform and relatively small compared to other populations in the region. If the density of a stunted population is reduced the fish grow normally. Dwarf or pygmy forms of a species are genetically distinct from normal forms and represent a diversi? fication in life-history often related to trophic ecology (Taylor and Bentzen 1993). Fish in these populations are also small relative to other populations in the region, however, individuals are not capable of normal growth. Enchanted Pond has a surface area of 133.5 hectares, a maximum depth of 56 meters, and a mean depth of 21m. Fish currently inhabiting En? chanted Pond include white sucker, brook trout (Salvelinus fontinalis Mitchill), lake chub (Couesius plumbeus Agassiz), and blacknose dace (Rhinichthys atratulus Hermann) (Anonymous 1979). Artie charr {Salvelinus alpinus oquassa L.) were introduced in 1991. The gill net survey used nylon and monofilament nets with meshes ranging from 16 to 64 mm stretch measure, 2m high and either 60m or 120m long. The nets were set on bottom from 24m to 56m deep and fished for five to twenty hours. Of the 228 white suckers captured, 50 fish were randomly selected and extended total length was recorded. Sex and maturity were recorded for six of these fish. Saccular otoliths, right pectoral fins, and scales were removed from an additional 20 randomly selected fish and placed in paper envelopes to dry. Length, weight, sex, and maturity were recorded on the envelopes. After comparing annuli on the three structures, pectoral fin rays were chosen as the hard structure to be used in determining age (Fig. 1). Beamish (1973), Beamish and Harvey (1969), and Quinn and Ross (1982) found fin rays to be the most reliable structure for aging suckers. Fish were aged according to methods similar to those described by Scidmore and Glass (1953). Direct age validation and confirmation of true annulus