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State of Owasco Lake Fisheries 2018

An informational meeting on the current state of Owasco Lakes fisheries was held by the DEC on February 28, 2018 at the Bass Pro Shops in Auburn, NY. Below is summary information from that meeting.

Owasco Lake Fisheries

  • Owasco Lake is the 2nd smallest Finger Lake in Region 7, comprising a bit over 6,800 acres. Maximum depth in the lake is around 170 feet. Auburn at the north end; Moravia at the southern end. Popular fishing tributaries include the Owasco Inlet, Hemlock Creek, Mill Creek, and Dutch Hollow Brook.

  • Like many of the finger lakes, it is a two story fishery, supporting popular coldwater species such as rainbow, brown and lake trout, and popular warmwater species including largemouth and smallmouth bass, northern pike and walleye
    Also popular for panfishermen, with decent catches of yellow perch, rock bass, black crappie and sunfish.

  • Main forage species in the lake are alewife and rainbow smelt. While our standard netting surveys provide some relative information on forage in the lake, we are still currently lacking an adequate and practical assessment method to properly monitor prey populations in the lake.

  • DEC is currently managing the lake to improve the populations of brown and rainbow trout. Walleye stocking occurred from 1996-2006. No stocking has taken place since. Walleye were prime suspects in the collapse of the rainbow and brown trout fishery that occurred approximately 4-6 years after their introduction in the lake.

  • We hypothesize that the walleye population is slowly dwindling in the lake - average age of walleyes caught in our surveys was around 17 years, and no juvenile fish have been recently observed. Natural reproduction is likely minimal to low in the lake due to predation of walleye fry by alewives.

  • Lake trout stocking has been cut in half as well (as they're known to cannibalize and also prey heavily on other juvenile salmonid stocks).

  • Rainbow trout are currently stocked at around 25,000 yearling equivalents annually, both in lake and tributary stocking; around 11,000 brown trout stocked annually. These stockings supplement limited recruitment from natural reproduction. 10,500 lake trout are stocked annually - which almost entirely supports the adult population in the lake as there is little to no natural reproduction of lake trout in Owasco.

  • A lake trout population index survey is conducted approximately every four (4) years on the lake. Current data shows a slight decline in the lake trout catch rate, which was expected following stocking adjustments. However, numbers per net were still on par with the long term average, and the population showed a stable age distribution and healthy average length. This will be monitored on an on-going basis and our stocking policies will be reexamined if necessary based upon our surveys and angler diary catch data.

  • We are also attempting to assess adult walleye and rainbow trout populations in the lake using similar survey methods, and are still evaluating this on an experimental basis.

  • The smallmouth bass and northern pike fishery (and largemouths to a lesser degree) appear to be fairly robust for anglers targeting them (decent numbers and respectable average lengths).

  • Wild production of rainbow and brown trout is estimated/monitored annually from backpack electrofishing surveys conducted in popular spawning tributaries. Hemlock Creek in Locke is a steady consistent producer of rainbow trout, followed closely by the upper Owasco Inlet in and around Groton. Dutch Hollow Brook is a contributor as well, and with planned habitat work on the mid-reaches of this tributary, should only improve in the coming years. Brown trout show decent levels of reproduction in the mid-upper reaches of the Owasco Inlet.

  • Many wild brown and rainbow trout are produced, however, the general consensus is that natural mortality (i.e. predation especially by lake trout and walleye) still has a significant effect on their chances of recruitment to the adult population in the lake.

Owasco Lakes CSLAP Program

Lakes vary in their underlying water quality or trophic state due to factors relating to formation, geology, chemistry, size and shape, hydrology, and land use. Lake aging, called eutrophication, occurs with time as a lake collects and retains nutrients and sediment resulting in degrading water quality. This normally takes centuries. Cultural eutrophication is an acceleration (decades) of lake aging as a result of human activities such as: land use changes, development, agriculture, and hydrology modification resulting in excessive nutrient (P, N) and sediment inputs.

Eutrophic lakes have high levels of nutrients and are highly biologically productive. Thus, eutrophic lakes often experience excessive algal and plant growth. Mesotrophic lakes have moderate levels of nutrients and biological productivity and experience nuisance algal and plant growth, at times. Oligotrophic lakes are low nutrient lakes and generally have low biological production. New York State has explicit criteria for defining trophic state based on summer average total phosphorus (TP) concentration, chlorophyll-a (Chl-a) concentration (a surrogate of algal biomass), and/or Secchi disk clarity.

The DEC utilizes the Citizens Statewide Lake Assessment Program (CSLAP), to help assess ponded waters in NYS. CSLAP is a volunteer lake monitoring/education program managed by NYSDEC and NYS Federation of Lake Associations. CSLAP was initiated in 1986 and is now mandated by ECL (17-0305). The program employs a consistent and approved monitoring approach, the volunteers are trained, use approved sampling methods (standard operating procedures), and certified labs analyze the water samples (NYS ELAP certified). The resulting lake data are interpreted by professionals. CSLAP has three major objectives: (1) collect lake data for representative lakes throughout NYS, (2) identify lake problems and changes in water quality, and (3) educate the public about lake conservation and management. The data educates stakeholders, adds to the long-term DEC data sets, can be used in water quality management plans, and supports many DEC management programs and activities including 9-Element Plan development. In 2017, CSLAP was expanded into the Finger Lakes, including Owasco Lake. For 15 weeks, two sets of citizen scientists collected surface and metalimnetic water quality samples for nutrients, chlorophyll-a, algal toxins, pH, conductivity, calcium, and dissolved carbon at two locations to assess the water quality of Owasco Lake.

Summer average TP (at the surface) for Owasco Lake was 14 µg/L, placing it in the mesotrophic range for water quality and less than the NYS average for TP. In 2017, the NYS average TP concentration for CSLAP lakes was 28 µg/L with a range of 4 µg/L to greater than 300 µg/L. Chlorophyll-a (summer average) in the upper waters of Owasco Lake was 5.3 µg/L (mesotrophic), 42% lower than the NYS summer average Chl-a concentration (9.1 µg/L). The range in Chl-a averages from CSLAP lakes in 2017 was less than 1.0 µg/L to greater than 50 µg/L. The summer average Secchi disk clarity for NYS ranged from less than 1 meters (poor clarity) to greater than 9 meters (very high clarity). The NYS average was 3.3 meters. In 2017, the summer average clarity of Owasco Lake was 3.4 meters, approximately at the state average. The composite average of these three indicators showed that Owasco Lake was mesotrophic in 2017.

Carlson's Trophic State Index (TSI; Carlson 1977) is a numerical scoring technique for defining trophic state that considers summer average TP, Chl-a, and Secchi disk clarity on scale from 0 (good water quality) to 100 (poor water quality). The TSI for Owasco Lake in 2017 was 44, in the mesotrophic range which ranked as 7th lowest of the eleven Finger Lakes. The current water quality in the open water of Owasco Lake was similar to results presented in the 1970's (Bloomfield 1978) and in the late 1990's (Callinan 2001) at sites similar to the current sampling location (Table 1). For both historical periods, Owasco Lake was mesotrophic. Compared with the late 1990's, TP was slightly higher in 2017 (+2 µg/L), Chl-a was substantially higher in 2017 (+1.5 µg/L), and Secchi disk clarity was slightly higher (~+0.2 m).

The Owasco Lake watershed and the lake itself have experienced many changes over recent years. Changes in climate and precipitation, land use changes, human and animal population shifts, and the establishment of invasive species have all influenced the water quality of Owasco Lake.

Ongoing work and analyses are currently underway to fill in the historical gaps of Owasco Lake's water quality. The Owasco Watershed Lake Association (OWLA) is supporting a comprehensive analysis of all water chemistry data collected on Owasco Lake from the 1970s to the present. Data from multiple agencies (EPA, NYSDEC), academic institutions (Hobart and William Smith Colleges), and research organizations (Finger Lakes Institute and Upstate Freshwater Institute) is being compiled to determine trends in water quality that will help managers determine reasons causing the recent increases in documented Harmful Algal Blooms (HABs).

Summary of summer average water quality conditions of Owasco Lake.
Year Total P (ug/L) Chl-a (ug/L) Secchi disk (m)
1970s 12 5.5 2.8
Late 1990s 12 3.8 3.1
2017 14 5.3 3.4

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