Monday, December 15, 2014

New Report Considers Future Of Lake Trout

Spawning-Lake-troutSince the retreat of the glaciers, lake trout (Salvelinus namaycush) have been the top native predator in Adirondack waters. These northern fish require true cold (less than 55°F) and move downward when surface waters warm in late spring and summer. Consequently, they are isolated to the largest and deepest Adirondack lakes – most of them deeper than 30 feet – where they stay in the dark chilly depths all summer and early fall. The species name namaycush is believed to be an Algonquin term for “dweller of the deep.”

This need for very cold, clean, high-oxygen water can bring to light otherwise invisible changes beneath the surface. Water quality in the Adirondack interior, where we don’t have much industry or farming, can be  abstract. You usually can’t see it, touch it or even taste it. But lake trout make the health of our coldest lakes real and tangible.

2013 Lake Placid Lake Trout Survey (Mary Thill Photo)Over the past year, I worked with the Adirondack Chapter of The Nature Conservancy to compile a report on the status of lake trout in northern New York. The document synthesizes the expertise of New York Department of Environmental Conservation (DEC) biologists and private lake managers as well as historical records, scientific literature and DEC databases. Released today, the paper will hopefully provide a new baseline to help gauge the future of not just an individual species, but also the region’s coldwater lakes.

Lake Trout and Climate Change in the Adirondacks: Status and long-term viability finds that 102 inland North Country lakes (with an average surface area of 923 acres) have current or recent records of lake trout. Looking forward, the paper overlays what we know about the region’s lake trout against anticipated changes in climate.

Mean annual air temperature in the eastern Adirondacks warmed by 2.1°F between 1976 and 2005, according to a 2010 report by the Adirondack and Vermont chapters of The Nature Conservancy. The range of anticipated additional warming in northern New York over this century is 6–11°F. Weather records show that episodes of heavy rain have been more frequent here in the past four decades than in the early 1900s.

Since the Adirondacks is near the southern limit of lake trout range, scientists expect these factors to eliminate a significant portion of the region’s coldwater fish habitat over this century.

As summer-like temperatures extend into spring and fall, small pockets of cold in shallower lakes are expected to shrink and run low on oxygen. Prolonged summer conditions are also expected to magnify problems in larger lakes impaired by fertilizers and introduced species such as bass.

four seasonsHow much deep water will become uninhabitable in the Adirondacks has not yet been estimated. The total will depend on the characteristics of individual lakes, the dynamics of change, and steps taken to minimize fertilizer and stormwater inputs, introduced species and other pressures on lake trout, ciscoes, round whitefish and their coldwater cohorts.

On the other hand, a number of larger, deeper, fast-flushing, highly oxygenated lakes in forested watersheds show high potential for long-term resilience. Every indication is that these lakes can remain lifeboats for coldwater fish at relatively little or no cost, if we take common-sense steps to minimize other stresses.

Nature itself could be a lake’s best defense against extreme weather. Buffers of trees and native plants along shorelines can act as sponges, soaking up runoff and the algae-feeding nutrients and silt it carries. Lake trout also give people yet another reason to make sure their wastewater systems are tight.

The Conservancy initiated the report in hopes that private and public lake managers can use the information to plan for intensified stresses on Adirondack coldwater fish. You can’t manage what you don’t measure, so the report points to a need to track when these types of lakes stratify into temperature layers in spring and re-oxygenate in autumn, and to monitor late-summer temperature and oxygen.

Several researchers have pointed out that oxygen has always been a limiting factor for lake trout in the Adirondacks. Despite regional land-use protections, water quality decline is one of the major reasons the species is no longer found in 74 lakes here with historical records. So in that sense we’re not entering entirely new territory. But something to watch for as temperatures warm is whether deepwater oxygen also declines in lakes where nutrient inputs haven’t increased, creating exceptions to a 150-year pattern of increased nutrients/decreased oxygen.

A copy of the lake trout report can be found here.

Photos: Spawning lake trout (UVM /USFWS), and DEC aquatic biologists Rob Fiorentino (left) and Jim Pinheiro inspect a lake trout netted during a survey of Lake Placid in 2013 (Mary Thill). Illustration: Lake trout life events and potential climate change impacts by season. Climate change is expected to magnify stresses on Adirondack lake trout by depleting oxygen at the bottom of lakes in summer and fall, by shrinking coldwater habitats, and by increasing predation on young trout by introduced warm-tolerant fish such as bass (Illustration by Matt Paul).

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Mary Thill lives in Saranac Lake and has worked alternately in journalism and Adirondack conservation for three decades.

10 Responses

  1. Paul says:

    Interesting story, but is this accurate?

    “Since the Adirondacks is near the southern limit of lake trout range”

    Lake trout are found in many of the Finger Lakes. Of course they are much deeper than Adirondack lakes.

    • John Warren says:

      Paul is unfamiliar with the meaning of “near”.

      • Heavy says:

        Perhaps you are the one that is unfamilair with the term.

        New Jersey also boasts two fabulous Trophy Trout Lakes. Round Valley and Merrill Creek Reservoirs both support monster rainbow trout, brown trout and lake trout. Round Valley supports perhaps one of the most southern naturally reproducing populations of lake trout and boasts the current state record of more than thirty-two pounds!

        (not that i would have even picked up on this, but if you are be snarky in someone asking a question)

  2. Jim S. says:

    Be nice, I appreciate Paul’s comments. Don’t go angling for

  3. Paul says:

    It is interesting the oxygen levels must be influenced by the aquatic vegetation (as well as mixing where these waterbodies can pick up oxygen).

    Increased buffering of the shore line with trees (and the fact that we are seeing more extreme weather which probably means more cloudy days) this lower level of sunlight must have an impact on plant growth as well as photosynthesis rates in the plants. That all adds up to less O2 in the water.

  4. Bob says:

    At least two of the Essex Chain Lakes currently have healthy native Lake Trout populations, Third and Fifth Lakes. This was true several years ago and remains the case as of this past season. They are not stocked fish.

  5. Mary Thill says:

    Belated thanks for all the comments. The southern limit of lake trout is (with the exceptions of the extremely deep Finger Lakes and Great Lakes, as the report states) 43° latitude, the southern boundary of the Canadian Shield and the Adirondack Park.

    According to the New Jersey Department of Environmental Protection, lake trout were introduced into Round Lake Reservoir in 1977. They’ve also been introduced in other parts of the world, including more southerly New York reservoirs, where they’ve become self-sustaining.

    And yes there is a wild, self-sustaining population in the Essex Chain, although abundance appears to be low.

    • Paul says:

      Thanks for the reply. Like I indicated in my comment, yes the finger lakes are far deeper than anything in the Adirondacks. It makes sense that they are an exception to where we normally would find this fish.

      Since the smaller (warmer) waterbodies can sustain the fish it must be that these waterbodies have more O2? It seems that adequate sunlight is a key factor. It is tricky since the same thing that can improve photosynthesis of the aquatic vegetation and improve the oxygen content, can also warm the water?

      We need cold sunny (and even windy) days!

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