This work is based primarily on two contributions. The first, McBride and Sanford (1996), is devoted to the auteco logy of cold water fish and other "species of special interest" and is taken in large part from the "Fish Resources" section of that contribution. The second, Foster (1996b), is synecological in nature and, using somewhat restricted data sets and anecdotal information, attempts to characterize the nature of the stresses on Otsego Lake utilizing its fish resources as indicators. In using both sources, factual statements not otherwise documented are unpublished observations reported in the above mentio ned contributions for the first time.
The future of the cold water fishery of Otsego Lake is an important concern of local citizens and government. The most important objective economic index of water quality is the ability of the lake to maintain a cold water fishery (Harman, 1991 In McBride and Sanford, 1996). Other traditional water quality based utilization is assured in the process of managing and protecting such a fishery. Because fish are at the top of, or near the top of, the aquatic food chain, a healthy fishery is considered by some to be reflective of a healthy environment (McBride and Sanford, 1996). One aspect of such a fishery is reflected in the diversity of species thriving in the community (see p. 265, item 10). However, stenotopic species, such as lake trout, thriving under conditions of increasing productivity are prone to encounter density independent limiting factors which are altered by successional phenomenon (increasing eutrophy) (Andrewartha and Birch, 19 64; Lindeman, 1942). Of great concern in Otsego Lake is the amount of available oxygen in hypolimnion waters before fall overturn (see "Physical Limnology"). Low oxygen concentrations limit the volume of habitat available to cold water species in late summer and, if extreme, can result in physiological stress and mortality (Nichols, 1995).
Fish, through trophic cascades, affect many parameters often used as indicators of trophic status via increased biocycling of phosphorus (Cooke, et al, 1993). The predation on zooplankton of fish, such as rainbow smelt and alewives may determine the structure of lower trophic levels and the pattern of energy flow in aquatic systems. Lakes supporting species of zooplankton with large individuals can be expected to have clearer water than those with populations having smaller individuals due to intense grazing by the larger zooplankton on algae (Mills and Schiavone, 1982). Accordingly, the degree of fish predation on zooplankton can alter many importa nt limnological parameters, including water transparency, chlorophyll a levels, and dissolved oxygen concentrations.
The effects of fish predation on the composition and size structure of zooplankton communities is well documented (Cooke et al., 1993). The presence of planktivores such as alewives, rainbow smelt, and cisco, as well as juveniles of many species, have all been associated with loss or reductions of large zooplankton (Mills and Schiavone, 1982). In Otsego Lake, whic h is currently inhabited by all these species, it is assumed that fish populations have had a profound effect on water quality through predation on zooplankton. Harman et al. (1980) asserted "Otsego Lake would thus seem to have the potential for a higher algal standing crop and less transparency than currently observed (in 1976) without any increase in (external) nutrient loading. Factors that reduce the zooplankton grazing rate would result in greater algal standing crops (Godfrey 1977b)".
Otsego Lake supports a diverse fish community including the only lake trout fishery in the nine counties comprising DEC Region 4. Two coregonid species, the lake whitefish (Otsego bass), which is native to the lake, and the cisco (greenbacks), an introduced species, inhabit the colder, deeper waters, as do lake trout.
The warmer, shallower areas of the lake support a wide variety of fish species. Dominant game fish include largemouth bass, smallmouth bass, and chain pi ckerel. Panfish include yellow perch, pumpkinseed, bluegill, rock bass, redbreast sunfish, and brown bullhead.
The first biological survey of Otsego Lake in 1935 captured 30 species of fish (Odell and Senning, 1936) (Table 46). At the time, the lake was noted for its lake trout and lake whitefish. Smallmouth bass, largemouth bass, and walleye were considered fairly common and chain pickerel common. The most abundant panfish were rock bass, pumpkinseed, and yellow perch.
Otsego Lake fi sh populations were not sampled again until 1952. Most of the NYSDEC sampling effort since then has been to assess lake trout and coregonid populations. In the 43 year period from 1952 to 1994, lake trout populations have been sampled 22 times with between three and 32 gill net gangs per sample year (Table 47) and warm water fish populations have been sampled three times (1965, 1985, and 1988). In addition, seining was done near Cripple Creek in 1978 to assess a proposed dredging project, and seining and boat electrofishing was done in 1993 and 1994 to assess the current status of the lake's cyprinid (minnow) populations. The 1994 fish collections were also used to assess the current status of smallmouth and largemouth bass in the lake.
Major changes in the lake's fish populations since 1935 include an inadvertent introduction of cisco sometime between 1925 and 1942 during regular stockings of lake whitefish fry. Walleye were routinely stocked between 1913 and 1934. Their populations have sinc e declined to remnant levels. Rainbow smelt were illegally introduced in 1979 or 1980. Although abundant by 1982 (Sanford, 1986), smelt were rare by the late 1980s, likely as a direct result of displacement by another illegal introduction involving the release of alewives in the mid-1980s. They became abundant by 1991. European rudd were introduced in 1990 (Foster and Collura, 1991). Their impact has not been ascertained. These changes are discussed in greater detail in the section entitled "Species of Special Interest".
Fish were first stocked into Otsego Lake in 1872 when 8,000 lake trout (size not specified) were released. Although the fish were reared and stocked by a private hatchery on the west shore of Otsego Lake, the eggs and fry were provided by the state hatchery system. From 1872 through 1877, this private hatchery stocked at least 468,000 lake whitefish, 286,000 lake trout, 1,000 black bass, and 200 rock bass.
The State began stocking the lake in 1892 w hen 100,000 lake trout (size not specified, probably fry) were introduced. However, stocking was sporadic and infrequent from 1892 to 1921. During this 30 year period, fish were stocked in 1892, 1904, 1905, 1913, 1914, and 1918. Numbers stocked totalled 850,000 walleye fry, 280,120 lake trout fry and fingerlings, and 200 largemouth bass fingerlings.
Annual stocking of the lake by the State began in 1922. During the period between 1922 and 1934, stocking records show that 8.93 million lake whi tefish fry, 4.15 million walleye fry, 101,275 lake trout fingerlings, 135,000 muskellunge fry, 18,100 smallmouth bass fry, and 4,250 steelhead (migratory rainbow trout strain) fingerlings were stocked.
Following the 1935 biological survey (Odell and Senning, 1936), it was recommended that smallmouth bass, lake trout, lake whitefish, and brown bullhead be stocked. The numbers and sizes of fish were not specified. Stocking policies were modified in 1954, 1959, 1967, 1970, 1974, 1976 and 1981 (T able 48). Stocking was terminated for all species in 1954 except for lake trout. Reasons for terminating the stocking of smallmouth bass, lake whitefish, and brown bullhead were not stated, but were probably related to advances in fishery science which, by that time, had demonstrated that the stocking of warmwater species and certain coldwater fish, like whitefish, was often unnecessary. Changes in lake trout stocking rates in 1954, 1974, and 1976 appear to reflect changes in statewide lake trout sto cking guidelines. Lake trout were not stocked between 1962 and 1967 because of the poor return of Finger Lake strain lake trout which had been stocked between 1952-1956. The changes in 1959, 1967, and 1970 were part of an ongoing study to evaluate the return of stocked lake trout. Landlocked salmon stocking began in 1982.
Fish stocking records for Otsego Lake from 1942 through 1992 are summarized in Table 49. Numbers stocked were often less than the recommended numbers due in part to hatchery problems associated with rearing lake trout and landlocked salmon. Lake trout and landlocked salmon stocking was suspended in 1993 pending improvements in public boat access to Otsego Lake. Lake trout stocking was resumed in 1994 to help evaluate the current status of the wild lake trout population but at approximately one third the preexisting rate, or 4,000 spring yearlings.
Statewide angling regulations (Table 50) apply to Otsego Lake. The lake trout and landlocked salmon se ason opens April 1 and ends September 30; the bass season opens the third Saturday in June and ends November 30. Anglers may take three lake trout, three landlocked salmon, and five bass per day. Minimum size limits for lake trout, landlocked salmon and bass are 21, 15, and 12 inches, respectively. Lake whitefish can be taken at any size all year but only five fish may be taken daily. There are no seasons, minimum size restrictions, or limits for cisco, panfish (bullhead, sunfish, etc.) or other fish (carp, sucker, etc.) species. In addition, snatching and blind snatching for lake whitefish are permitted with hooks having no more than two hook points from January 1 through March 15.
Lake trout in Otsego Lake have generally been managed with statewide regulations. On October 1, 1976, the long established 15 inch minimum size limit for lake trout was raised to 21 inches for Otsego Lake with the expectation that the higher size limit would protect lake trout until they reached sexual maturi ty, increasing natural spawning and recruitment. The statewide minimum size limit on lake trout went to 21 inches on October 1, 1977, but an error in the 1977-78 fishing guide established a year around open season on Otsego Lake between October 1, 1977 and September 30, 1978. The catch rate of lake trout in DEC surveys from 1976-78 (7.2 fish/net average) was substantially higher than in 1969-74 (3.8 fish/net average) when the 15 inch minimum size limit was in effect (Sanford, 1984). Gill net catches i n 1992 and 1994 averaged 10.5 and 9.3 fish/net, respectively, and are at their highest levels this century.
Fish from Otsego Lake are considered safe to eat. In 1978, 12 lake trout with a mean length of 17.5 inches (range was 14.9 to 22.8 inches) averaged 0.50 ppm PCB's, 0.07 ppm DDT, 0.27 ppm mercury and 0.10 ppm arsenic (BEP, 1981). Six white suckers with a mean length of 16.9 inches (range was 15.7 to 18.3 inches) averaged 0.26 ppm PCB's, 0.18 ppm mercury and 0.10 ppm arsenic (BEP 1981). The current federal Food and Drug Administration tolerance levels for PCB, DDT, and mercury are 2.0, 5.0, and 1.0 ppm, respectively. A tolerance level for arsenic has not been established. The statewide health advisory states that a person should eat no more than one meal (1/2 lb) of fish per week from the freshwaters of New York State. There are no additional restrictions/guidelines pertaining to Otsego Lake fish.
SPECIES OF SPECIAL INTEREST
Lake trout are native to Otsego Lake and occasionally attain weights exceeding 20 lb. Historic abundance levels are not known. The lake trout population has been augmented by stocking most years since at least 1872. Lake trout were sampled for the first time in 1935 (Odell and Senning, 1936). Comparison of lake trout catch rates (Table 47) over the sampling history of Otsego Lake is difficult because of the variability in gill nets (length, height, netting material and mesh size) used o ver the years. Only since 1969 have standardized gill net gangs (nets strung end to end) and netting sites been used. In June/July, 1935, 11 gill nets (length not specified) with variable mesh, either 5/8, 1, 12 or 3/4 and 12 in bar mesh, were set in habitat suitable for lake trout. These nets captured eight lake trout ranging in size from 9.3 to 32.0 in and averaging 18.7 in (Table 51) for a catch rate of 0.7 fish/net (Table 47).
The effectiveness of lake trout stocking was first evaluated fr om 1952 through 1956. At that time, approximately 40,000 fall fingerling and 8,100 spring yearling Finger Lake strain lake trout were being stocked annually. All yearling and half the fingerling trout stocked from 1950 through 1953 were fin clipped. Sampling was done from early June through early November with 500 ft gill net gangs which consisted of four 125 ft experimental gill nets sewn together. Each 125 ft net was composed of five 25 ft panels of 12, 2, 22, 3, and 32 in nylon stretch mesh. Netti ng effort decreased from 32 net nights in 1952 to three by 1956. Ninety-seven lake trout were caught during this five year study for an average catch of 0.4 fish/net (range was 0.3 to 0.5 fish/net) (Table 47). Only one marked lake trout was collected. Length and age data are not available. Stocking was terminated after 1961 because of poor returns of hatchery fish up to then.
Netting in 1962 (August), 1965 (July-September), and 1966 (July) continued to further evaluate the success of the 1950 -53 stockings. Two of 20 lake trout collected were marked. Gill net catch rates for the three years averaged 0.8, 1.0, and 1.5 fish/net compared to 0.3 to 0.5 fish/net from 1952 to 1956 (Table 47). The higher catch rate was due in part to sampling the more productive netting sites from the earlier study. Mean length of trout collected declined from 21.6 inches in 1962 to 13.8 in by 1966 (Table 51). The decline probably reflects the small sample size (5-9 fish) in those years and may not represent pop ulation changes. Differences in net construction may also have affected the catches.
Stocking was resumed in 1968 preparatory to a 10 year study beginning in 1969. Study objectives were to: 1) compare present lake trout populations with those present in the 1950s, 2) compare survival of the Finger Lake with Adirondack strains of lake trout, and 3) compare survival of spring and fall stocked yearlings. The lake trout population was sampled in September with 450 ft gill net gangs (three 150 ft experimental gill nets sewn together). Each 150 ft net was composed of six 25 ft panels of 12, 2, 23. 22, 3, and 32 in multifilament stretch mesh. Sampling effort and netting sites were standardized throughout the 10 year study.
A total of 607 lake trout from 5.2 to 34.0 inches total length were collected during the 10 year netting study (Table 51). Trout catch rates exhibited a relatively steady increase throughout the period. Annual trout catch rate ranged from 3.0 fish/net in 1969 to 7.7 i n 1977. The 10 year average catch rate of 5.1 fish/net from 1968-1978 was approximately 12 times greater than the 0.4 trout/net observed in the 1952-56 study (Table 47).
Fish collections indicate that stocking augmented the lake trout population in Otsego Lake without adverse impact on wild trout which also increased in abundance (Sanford, 1984). Total annual net catch of hatchery trout increased steadily from 6 (0.5 fish/net) in 1969 to 43 (3.6 fish/net) in 1978. Total annual catch of wild l ake trout increased from 30 (2.5 fish/net) in 1969 to 46 (3.8 fish/net) in 1978 (Sanford, 1984). Since virtually all lake trout collected in the 1952-56 study were unmarked and presumably wild fish, the average gill net catch rate of wild trout recorded from 1969-1978 of 3.0 fish/net represents a seven-fold increase over the 0.4 fish/net recorded during the 1952-56 study.
Adirondack and Finger Lake strain lake trout exhibited different growth and survival rates when stocked in Otsego Lake. Ad irondack strain lake trout captured in September averaged 7.7, 9.4, 11.0, 12.7, 13.5, 14.7, and 14.8 inches at Ages 2 through 8, respectively (Sanford 1984). The Finger Lake strain averaged 9.9, 10.5, 13.5, and 19.4 inches at Ages 2 through 5, respectively (Sanford, 1984). Even though total gill net catches of Adirondack strain fish were 2.5 times higher than the Finger Lake strain between 1969 and 1978, few Adirondack strain lake trout lived long enough to reach the legal size limit of 21 in (Sanfor d, 1984). Due to the superior growth of the Finger Lake strain, the stocking of Adirondack strain lake trout was discontinued after 1974.
The performance of spring and fall yearling lake trout was compared between 1970 and 1974. There was no difference in the survival of the Finger Lakes strain yearlings stocked in the spring and fall. The total gill net catch of both spring (average length 5.7 inches) and fall (average length 8.2 inches) stocked fish averaged 0.2% of the fish stocked (Sanford , 1984). However, the catch of fall stocked Adirondack strain yearlings (average length 6.0 inches) was nearly triple the catch of spring stocked yearlings which averaged 4.2 inches long and eight times higher than the catch of spring stocked Finger Lake strain yearlings. The superior return of fall stocked Adirondack strain yearlings, however, was negated by their poor growth. Fall yearling stocking was discontinued after 1974.
Since the end of the 10 year study in 1978, lake trout populatio ns have been sampled in 1981, 1986, 1992, and 1994 using the same nets, sampling sites, and netting effort. Beginning in 1992 sampling effort was reduced by half (12 nets to 6 nets) to allow for more frequent sampling (every other year) without increasing fish mortality. Catch rates declined from 7.4 fish/net in 1978 to 3.3 fish/net in 1981 before rebounding to 4.9 fish/net in 1986, 10.5 fish/net in 1992 and 9.3 fish/net in 1994 (Table 47). The 1992 catch was the highest ever recorded and the 1994 ca tch rate was the second highest. The low catch in 1981 may be due in part to the low catch of Adirondack strain fish. Adirondack strain fish averaged 27% (range was 20-36%) of the trout catch between 1973 and 1978 but only 8% in 1981 (Region 4 Fisheries files). It is not known if the high catch rates observed in 1992 and 1994 are the result of an expanding wild lake trout population or increased survival of hatchery lake trout in response to the recent introduction of alewives, or both, or if the curr ent high catch rates can be sustained. At the present time the origin of lake trout (wild vs hatchery) can be determined, but not with complete reliability, through the comparison of back calculated lengths of hatchery and wild fish. In 1992, wild lake trout averaged 4.1 inches at Age 1 while hatchery fish averaged 7 inches or more when stocked. To reduce speculation about origin, lake trout stocked in 1994 were, and will continue to be, marked with fin clips.
Growth of wild lake trout during the September, 1969-78 study was slow with fish from Ages 2-8 averaging 7.9, 10.5, 12.8, 14.6, 16.5, 19.0 and 22.6 inches, respectively (Sanford, 1984). It took eight years for lake trout to reach the legal size of 21 inches. Since the conclusion of the 1969-78 lake trout study, both smelt and then alewife became established in Otsego Lake. In September, 1994, wild lake trout from Ages 2-6 averaged 10.8, 13.0, 19.2, 21.4 and 24.7 inches, respectively (Region 4 Fisheries files). It now takes five year s for lake trout to reach 21 inches. The improved growth rates were attributed to the abundant forage which is currently dominated by alewives. Growth of Otsego Lake lake trout is now comparable to, and sometimes faster than, growth rates reported for the western Finger Lakes (Angold, 1995).
Examination of gonads indicated that Finger Lake, Adirondack, and wild lake trout all apparently attain sexual maturity at the same size in Otsego Lake (Sanford, 1984). About half of male trout attain sex ual maturity at a length of 20 inches while females are seldom mature until at least 21 inches long.
Some lake trout historically spawned on the rocky shallows along the west shore south of Five Mile Point (Figure 12) in late November and early December. Eggs and fry have been collected in water three feet deep (Greeley, 1936). Although natural spawning still occurs, the traditional shallow water spawning has not been documented in the lake since 1954 (Region 4 Fisheries files). The locations of existing spawning sites are unknown.
Diary cooperators during the 1993 fishing season caught 335 lake trout of which 74% (248 fish) were legal ($ 21 inches) size fish. The mean length of fish caught (creeled plus released) was 23.8 inches. Almost 15% of the catch were trout 30 inches and longer. The catch rate of all size lake trout was 0.39 fish/hr and 0.29 fish/hr for legal size fish. The overall catch rate was comparable to those of the Finger Lakes where angler cooperators in 1993 ave raged 0.38 fish/hr (range was 0.06 to 0.60 fish/hr) in the eight Finger Lakes with lake trout fisheries (Central Office fisheries files). In the Finger Lakes, most of which having a 15 inch minimum size limit, the catch rate of legal size lake trout ranged from 0.04 to 0.38 fish/hr and averaged 0.33 fish/hr (Central Office fisheries files).
Landlocked Atlantic Salmon
The current landlocked salmon population in Otsego Lake is the result of a stocking program that began in 1982. This highly prized game fish has attained weights approaching 10 lbs in Otsego Lake.
Landlocked salmon were experimentally stocked in three tributaries (Shadow Brook, Hayden Creek, and Leatherstocking Creek) in 1955 and Shadow Brook and Hayden Creek in 1956. DEC has no authenticated records of any landlocked salmon being taken from the lake as a result of this effort (Fieldhouse, 1969). Salmon were not stocked again until 1982 when the recently introduced rainbow smelt became abundant [the rationale being that smelt would provide a high quality forage base for this fishery (Sanford, 1987)].
The 1982 stocking policy called for 2 spring yearlings (6.0 inch average size) per acre (8,000) yearlings annually. Because of production shortfalls in some years, the number of fish stocked annually has been as low as 4,000 fish (Table 49). Hatchery yearlings are usually stocked directly into the lake. In 1982, however, the fish averaged only 4.3 inches, which precluded direct lake sto cking. Instead they were stocked into Hayden Creek and Lawyers Creek in an effort to maximize survival (Sanford, 1986). No significant fishery resulted from these tributary stockings.
Natural reproduction was not expected since the lake's tributaries are either warm or are inaccessible to spawning salmon (Sanford, 1986). However, Foster (1990) reported finding an unspecified number of salmon parr during the summer of 1989 in Leatherstocking Creek, Mohican Canyon Creek, Shadow Brook, and Hayde n Creek. No salmon parr were found during a 1994 survey of Leatherstocking Creek and Shadow Brook (Foster, 1994).
It takes two years for salmon to reach legal size ($ 15 inches). Fall age 2, 3 and 4 salmon averaged 17.5, 18.7 and 21.4 inches, respectively (Region 4 fisheries files). An Age 5 salmon 27.8 inches long weighing 9.02 lb was netted in September, 1992. Salmon growth in Otsego Lake is good by New York standards (Hulbert, 1994).
Diary cooperators, during the 1993 fishing seaso n, caught 93 landlocked salmon of which 49% were of legal size ($ 15 inches). The mean length of fish caught (creeled plus released) was 14.9 inches. The largest fish caught was 26.0 inches. The catch rate for all size salmon was 0.11 fish/hr (0.05 fish/hr for legal size fish) and is high by New York standards. In 1993, angler cooperators on seven lakes averaged 0.04 landlocked salmon per hour (range was 0.02 to 0.11 fish/hr) and 0.01 fish/hr (range was 0.01 to 0.05 fish/hr) for legal size fish.< /u>
Lake whitefish and cisco are found in Otsego Lake and are referred to locally as Otsego bass and greenbacks, respectively. Lake whitefish are native, while cisco were probably inadvertently introduced into the lake sometime between 1925 and 1942 during regular stocking of lake whitefish fry. Cisco were first reported in 1955 when two individuals were collected (Table 47).
Whitefish were once extremely abundant in Otsego Lake. DeKay (1842) reporte d that as many as 5,000 whitefish were taken in a single seine haul. Although not as abundant in the 1900s, whitefish ,along with cisco, provided a unique, locally important sport and commercial fishery into the 1980s. Sport and commercial interest in the two species waned as the population and fitness of these fish declined drastically following the introduction and irruption of the alewife (Foster, 1996; Keenen and Ketola, 1993).
Comparisons of coregonid catch rates (Table 47) over the sampling history of Otsego Lake are difficult to make because of the variability in gill nets (length, height, netting material, and mesh size) used over the years. Only since 1969 have standardized gill net gangs and netting sites been used. In general, cisco are the dominant coregonid and it appears that both lake whitefish and cisco populations were relatively stable until the late 1980s (Frost, 1993). The high whitefish catch rate (32.2 fish/net) reported in 1962 could have been due in part to misidentify ing cisco as lake whitefish. Between 1969 and 1978, the catch of lake whitefish and cisco averaged 3.5 fish/net (range was 2.1 to 5.7) and 10.3 fish/net (range was 6.8 to 14.6), respectively (Table 47). The catch of 23.3 cisco/net in 1981 was the highest ever recorded but declined to 12.9 cisco/net in 1986. In 1992, the catch of 1.8 lake whitefish/net and 6.0 cisco/net was the lowest recorded since 1969 and catch declined further in 1994 to 1.3 and 2.8 lake whitefish and cisco/net, respectively (Tabl e 47). The decline in both lake whitefish and cisco abundance is probably the result of predation by alewives on the pelagic larva and fry. In addition, cisco and alewife are both pelagic planktivores, but alewives, because of their feeding habits, are more efficient predators on zooplankton populations than are cisco and whitefish (see "Zooplankton" section for detailed description of zooplankton population dynamics following the alewife introduction).
Whitefish and cisco average 17.0 and 1 4.5 inches, respectively (Tables 52 and 53). The largest whitefish and cisco in DEC fish collections were 20.1 and 18.9 inches, respectively. Back calculated lengths of Age 1-9 whitefish were 6.0, 9.l, 11.6, 13.5, 14.9, 15.8, 16.1, 16.6, and 16.9 inches (Newell, 1975). Back calculated lengths of Age 1-7 cisco were 6.8, 11.5, 13.3, 14.0, 14.6, 15.1, and 15.7 inches (Newell, 1975). Growth rate of whitefish has increased following 1935.
Very little is known about the early life history of corego nids in Otsego Lake. According to the literature, spawning of lake whitefish takes place in late fall near shore in water about 25 ft deep over rock, gravel, and sand (Smith, 1985). This suggests that potential spawning habitat in Otsego Lake is abundant. Greeley (1936) reported finding eyed whitefish eggs in Otsego Lake in water less than five feet deep. In Lake Huron, larval whitefish were captured at depths of 33 feet and less and were most abundant along certain deep shorelines for about one week each year (Faber, 1970) After the young whitefish leave the shallows, they descend rapidly into the thermocline where they exhibit a markedly close association with the 17EC (62.6EF) isotherm (Reckahn, 1970). By late summer, fingerling whitefish descend into the hypolimnion. Cisco spawn later than lake whitefish (Smith, 1985). Presumably, young cisco follow a similar movement pattern as young lake whitefish.
Food habit studies demonstrated that adult whitefish and cisco do not directly comp ete for food. Benthic organisms constitute the bulk of the diet of mature lake whitefish while cisco consume primarily zooplankton (Newell, 1976). Since alewives are also zooplankton grazers, and much more efficient at collecting zooplankton than are cisco, cisco populations are expected to continue their decline evident by 1990 (Frost, 1993).
There is little historic information on walleye in Otsego Lake. It is not known whether walleye are native to the Susqueh anna River drainage or not (Colby et al., 1979; Regier et al., 1969; Festa et al., 1987). Stocking records suggest that walleye were first stocked into Otsego Lake in 1913 with the heaviest stocking occurring between 1922 and 1934 when 4.15 million walleye fry were stocked. Although only four walleye were collected during the 1935 biological survey, they were judged to be fairly common. Odell and Senning (1936) lamented the establishment of walleye because they felt that they wou ld potentially impact unfavorably with more valuable species, presumably lake trout and whitefish. Walleye have not been stocked since 1934.
Fifty-two walleye were collected during the 1952-56 lake trout study. Gill net catch rates were 0.4, 0.2, 0.9, 0.7, and 0.6 walleye/net in 1952-56, respectively, and averaged 0.5 walleye/net. No information on the age and size structure of walleye captured during that study can be found. Four walleye 14.0 to 24.3 inches were captured during the 1969-78 l ake trout study, all in 1976, for a catch rate of 0.3 fish/net that year. Although the relative effectiveness of the nets used in this and the 1952-56 study cannot be quantified, the 10 year average of 0.03 walleye/net was approximately 16 times less than the 0.49 walleye/net recorded during the earlier survey. Limited sampling of littoral (inshore) zone fish populations in 1965 captured three walleye 21.9 to 27.0 inches and none in 1988. Three walleye were captured in 1992 netting operations by SUNY Biological Field Station staff (Foster, 1993). No walleye were collected or observed in 3.5 hr of night electrofishing for bass in June, 1994.
Lawyers Creek (Cripple Creek), at the north end of Otsego Lake, historically supported a major spawning run of walleye. Fish were abundant in this stream even during daylight hours. In 1969, it took only a few hours to capture and tag 100 adult walleye. Very few fish were aged because annuli were difficult to distinguish in these large 5-8 lb, presuma bly slow growing, specimens. Unfortunately, all data from this sampling effort have been lost. Reports from sportsmen in the 1970s suggested a decline in the size of the walleye spawning run in Lawyers Creek. In the late 1970s anglers began complaining about declining catches of walleye in the lake. In 1990, netting of the creek from March 31 through April 28 captured no walleye (Lehman et al., 1990).
Although sampling records are poor, all recent evidence suggest that only a vestigial walleye population remains in Otsego Lake. The decline in walleye abundance is probably related to the increasing abundance of cisco which were first reported in 1955 (Table 47) (see below). Walleye fry are transported from the spawning grounds by water currents. After the yolk has been absorbed, fry concentrate near the surface for several weeks (Houde and Forney, 1970), during which time predation by efficient planktivores may be intense.
Rainbow smelt and alewife are both recent unauthorized introductions into Otsego Lake. Smelt were introduced in 1979 or 1980 and were abundant by 1982 (Sanford, 1986). Smelt populations have since declined to low levels and are not expected to rebound although fluctuations in year class abundance are typical of the species. Some area residents reported spawning runs of smelt in a few of the larger tributaries in 1995. Alewife were collected for the first time in 1988 and were abundant by 1991. A die-off of h undred(s) of alewives occurred that spring. A die-off of thousands of alewives (4.4-5.9 inch) occurred in June, 1992.
The establishment of smelt and alewife has had both positive and adverse impacts. Lake trout growth rates have dramatically improved. In 1992, wild lake trout at Ages 3-5 averaged 11.8, 17.5, and 20.0 inches (Region 4 Fisheries files) compared to 10.5, 12.8, and 14.6 inches during the 1969-78 lake trout study (Sanford, 1986). As note, the presence of alewife may preclude the reestablishment of a self-sustaining walleye population because of predation on pelagic walleye fry. The impact of alewife on an abundant walleye population can be devastating, as illustrated by the situation in Schoharie Reservoir which is located approximately 32 mi southeast of Otsego Lake. Alewife were introduced into this reservoir in the late 1980s and became abundant by 1990-91. No age 0+, 1+, 2+, or 3+ walleye were collected during a 1995 survey, which indicates no walleye recruitment since 19 91 (Region 4 Fisheries files). However, alewife, gizzard shad and blueback herring (all small clupeids) are present in Oneida lake (ca 50 miles NW of Otsego Lake), where they coexist with walleye. Similar coexisting populations occur in the Great Lakes.
Alewives may have contributed to the demise of the previously abundant cisco population in Owasco Lake, a Finger Lake near Auburn (Chiotti, 1980). There, alewife were introduced in the late 1960s and cisco were rare by 1979. No cisco have bee n caught in Owasco Lake since 1979 (Chiotti, 1980). Cisco populations in Otsego Lake are likely to suffer a similar fate. Gill net catches of cisco and whitefish in 1992 were among the lowest recorded and declined even further in 1994 (Table 47). The abundance of large crustacean zooplankters has been drastically reduced since the introduction of smelt and alewives, and have been replaced by smaller cladoceran species and rotifers (Wigen 1990) (see "Zooplankton" section). Other likely impacts of the a lewife are detailed in sections on "Dissolved Oxygen", "Transparency", "Plant Nutrients", and "Trophic Status".
Otsego Lake supports both largemouth and smallmouth bass; however, smallmouth bass are dominant. In 1988 and 1994, smallmouth bass outnumbered largemouth bass in June electrofishing collections by 6:1 and 4:1 ratios, respectively (Table 54). The steep sided shoreline, consisting primarily of sand, gravel, cobble, and exposed bedrock (H arman et al., 1980) favors smallmouth bass.
Electrofishing catch rates for smallmouth bass were 15.7 fish/hr and 4.9 legal ($ 12 inch) fish/hr in 1988 compared to 39.4 fish/hr and 10.9 legal fish/hr in 1994. Largemouth bass catch rates were 2.7 fish/hr and 1.6 legal fish/hr in 1988 compared to 9.7 fish/hr and 4.0 legal fish/hr in 1992. The increased catch rates from 1988 to 1994 for both bass species can probably be attributed primarily to water temperature at the time of sampling. In 1988, the water temperature was 59EF compared to 69-75EF in 1994.
Proportional stock density (PSD) and relative stock density (RSD) of 12 and 14 inch fish was 44, 34, and 10 in 1988 compared to 53, 42, and 15 in 1994. The sample size of largemouth bass was too small to calculate meaningful PSD's and RSD's; however, 60% of the bass collected in 1988 and 41% in 1994 were legal size ($ 12 inch) fish (Table 18). Although larger smallmouth bass appeared to be more abundant in 1994 than in 1988, th e differences do not appear to be meaningful. Anderson (1980) suggested that a balanced bass population should have a PSD of 40 to 70 and RSD14 of 10 to 25. By these standards, Otsego Lake supports a balanced smallmouth bass population.
Relative weight (Wr), a measure of condition, for smallmouth bass in 1988 and 1994 was 87 and 90 compared to 99 and 102 for largemouth bass, respectively. The normal range of Wr for both smallmouth and largemouth bass is 95 to 100. The condition of bass has apparently been unaffected by the introduction of alewives.
Largemouth bass are faster growing than smallmouth bass and attain legal size ($12 inches) during their fifth summer at Age 4. Smallmouth bass generally attain legal size during their sixth summer at Age 5. In June, 1988, largemouth bass at Ages 4 and 5 averaged 11.9 and 12.8 inches, respectively; smallmouth bass averaged 5.7, 7.3, 9.4, 10.6, 13.0, 13.1, and 15.3 inches at Ages 2 through 8. Bass growth rates since alewives h ave become established are largely unchanged from those recorded in 1988. Age 4 and Age 5 largemouth bass collected in June, 1994, averaged 10.2 and 13.1 inches, respectively. Smallmouth bass in 1994 averaged 6.8, 9.1, 12.0, 12.9, and 14.6 inches long at Ages 3 through 7. Only Age 5 and Age 7 bass were larger than those recorded in 1994. The increase in length at Age 5 in 1994 can not be explained but is probably not due to the presence of alewives since both younger and older bass were smaller than in 1988. The larger average size of Age 7 bass in 1994 is probably due to the small sample size in 1988. By New York standards, largemouth and smallmouth bass demonstrate average and slow growth, respectively (Green et al., 1986).
New York currently has 19 fish species listed as endangered, threatened, or of special concern. The blackchin shiner is currently listed as a species of special concern. In New York, this fish has been found historically in Chautauqua Lake, the Allegheny River, the Finger Lakes, the St. Lawrence River, the Lake Champlain basin, and Otsego and Canadarago Lakes. Blackchin shiners were last collected in Otsego Lake and Canadarago Lake in 1980 and 1976, respectively. In more recent years, the blackchin shiner has only been collected in the St. Lawrence River drainage (Smith, 1985). Otsego and Canadarago Lakes are located at the southeast periphery of their North American range.
During the 1935 survey of Otseg o Lake, approximately 130 blackchin shiners were collected with 10 to 30 foot long seines at 10 locations around the lake (Region 4 Fisheries files). This shiner generally prefers the shallow parts of lakes in clear-water, vegetated areas with sandy gravel or organic debris substrate. MacWatters (1983) described blackchin shiner abundance in Otsego Lake as sporadic or rare. Seining and electrofishing by Region 4 Fisheries personnel in June, 1993, did not capture any blackchin shiners at sites where t hey were historically collected in 1935. Sampling of the remaining sites was completed in 1994 and no blackchin shiners were collected or observed. Staff from the SUNY Oneonta Biological Field Station seined at a number of sites around the lake during the summer of 1994 and they also did not collect any blackchin shiner (Foster, 1994).
Near-term and long-term trends in the fish communities of Otsego Lake have been impacted, or result from, the following phenomena (Foster, 1996b):