Wednesday, November 6, 2013

Adirondack Fish: Spawning Lake Trout

Spawning Lake troutAs cold weather becomes more common and intense, the temperature of lakes, ponds and marshes drop significantly, with ice soon appearing over the surface of our smaller and more shallow waterways. As these aquatic settings continue to relinquish heat to the atmosphere, most of their resident, cold-blooded creatures are forced by the low temperatures to become extremely lethargic or lapse into a dormant state until spring.

There are, however, a few forms of life that remain active throughout the winter, as these entities are well adapted for an existence in frigid waters. Among the animals that thrive in northern lakes, even during winter, is the lake trout, a sizeable predator that resides only in our largest and deepest lakes; and it is during mid to late autumn when this prized game fish migrates to certain gravel bottom locations in order to spawn.

The lake trout is a large and robust member of the trout and salmon family, characterized by a single dorsal fin supported by soft and flexible rays rather than spines, and an adipose fin. Aside from its size, this species of char is identified by its dark colored back and sides marked with light, irregular-shaped splotches.

This native member of the Adirondack fauna gets its name from its ability to remain in large and deep bodies of water throughout the duration of its life. Nearly all species of trout and salmon require the well oxygenated water that occurs in streams and brook where a gravel bottom develops from the current in which to spawn. However, lake trout eggs, and the fry that eventually emerge from them, do not require the same high concentration of dissolved oxygen as the eggs and fry of other members of this family.

As a general rule, the lake trout migrates to specific shoals covered with course gravel when spawning season arrives. It’s not known why some shoals are regularly used and others are ignored as spawning beds, however, researchers have noted that temperature is a critical factor, as are lake currents and underwater turbulence generated by large waves on the surface.
During mid to late autumn, strong November gales can create sizeable waves in some sections of a large lake. This can produce enough unwanted random movement of the water across a shallow shoal to make it unacceptable as a spawning site. Deeper shoals offer quiet waters; however, the amount of dissolved oxygen at lower depths may not be in the range preferred by the eggs and fry of this trout. The presence of fish-egg eating creatures active at that location, and the abundance of predators that consume fry are other factors believed to influence the process of selecting a spawning site.

As the water cools, the lake trout is able to expand its travel options into shallow sections of a lake, as this fish prefers to inhabit water in the upper to mid 40’s. Lake trout develop more fat and oils throughout their entire body than other members of this family of fish. Such deposits of fat better insulate this hardy fish against the frigid water, which enables it to more effectively function in cold locations.

The fats and oils that develop in the body of a lake trout contribute to its “fishier” or “stronger” flavor than that of other trout and salmon, making the lake trout less appealing to eat. Some people, however, find this oily presence and unique taste flavorful, especially when it has been cooked with various spices and seasonings.

Regardless of how its has been prepared, the high concentration of fats in a lake trout allows its body to retain more unwanted chemicals acquired from ingesting smaller fish, than almost any other type of Adirondack fish. Not long ago, DDT was the main contaminant that accumulated in the body of a lake trout; however, this toxic substance has been removed from our environment and now methyl mercury is of primary concern. Health officials from New York State have issued warnings over the past decades against the over consumption of fish taken from Adirondack waters because of the amount of methyl mercury present in their meat. While some types of fish do not contain much of this dangerous compound, the lake trout does because of its longevity and its high body fat composition.

Although fishing season has ended for most bodies of water, there are still several waterways in the Park that are open for fishing. Please check the local fishing regulations before venturing out with a rod and reel, and note the health statements regarding lake trout put out by the State. Many Adirondack lakes have vibrant populations of lake trout because of the large size, great depth, extreme clarity and cold temperatures of these bodies of water throughout the year. And during the latter part of autumn, this powerful predator goes on the move, searching for a suitable spawning bed and a breeding partner.

Photo: Spawning Lake Trout (Photo courtesy UVM, with funding by USFWS).

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Tom Kalinowski is an avid outdoor enthusiast who taught field biology and ecology at Saranac Lake High School for 33 years. He has written numerous articles on natural history for Adirondack Life, The Conservationist, and Adirondack Explorer magazines and a weekly nature column for the Lake Placid News. In addition, Tom’s books, An Adirondack Almanac, and his most recent work entitled Adirondack Nature Notes, focuses on various events that occur among the region’s flora and fauna during very specific times of the calendar year. He also spends time photographing wildlife. Tom’s pictures have appeared in various publications across the New York State.

4 Responses

  1. Mark f says:

    Very Interesting article, thanks.

  2. Donn R says:

    Where was the picture taken? I have never seen that many Lake Trout in one area. Usually they swim alone or in a small group. I notice the Zebra Mussels on the rocks

  3. Donn R says:

    I also notice the Lake Trout out front has a scar from probably a lamprey. So I’m guessing Lake Ontario?