Each fish will repeat the spawning act many times over a period of days or weeks. The fertilized eggs sink to the rock bottom and fall into the protective crevices. Here the current of the passing water keeps the eggs oxygenated and silt free. A single female may lay 2,, eggs depending on her size. The embryos develop for 4 to 5 months and hatch into alevins free swimming embryos then in February and March.
The alevins live in the rock crevices for another few weeks while they finish their fin development. Then they disperse into the lake. Conservation and Management Lake trout used to be a very important commercial fish in the Great Lakes.
A combination of predation by the sea lamprey, declines in the cisco populations their main food , and overfishing caused their populations to go way down. Today they are recovering in Lake Superior, but they probably will never return to their previous numbers. The lake now has exotic competitors, like coho and chinook salmon, as well as exotic forage fish like smelt and alewives. The ecosystem is a very different one from what it was when the lake trout was king.
They do this by using poisons that selectively kill larval sea lampreys. Permission is granted for the non-commercial educational or scientific use of the text and images on this Web document. Please credit the author or authors listed below. Photographs by Konrad P. Lake trout become sexually mature at 6 or 7 years of age. The average adult weighs 9 to 10 pounds but some individuals weigh up to 50 pounds state record is 61 pounds, 8 ounces.
Their life-span may exceed 25 years. It can be found in all five of the Great Lakes and many large, deep, cold water inland lakes of Michigan. The lake trout prefers water temperatures between degrees Fahrenheit. In the fall, winter and spring seasons this fish may be found in shallow water areas of the lake, 10 to 30 feet deep. As near shore waters warm in the summer, it follows the cold water temperatures to depths of to feet or more. In the Great Lakes environment lake trout will often range many miles in search of prey.
Over commercial fishing and the introduction of the parasitic sea lamprey severely reduced the lake trout populations in the Great Lakes from to Later, chemical contaminants may have also contributed to reproduction problems. Now with better fisheries management, control of the sea lamprey, and solving pollution problems, the stocks are coming back.
Lake trout can successfully hybridize with brook trout to form "splake". This can occur naturally or more commonly in hatcheries by fertilizing lake trout eggs with brook trout sperm. Splake will live for 5 or 10 years and can reach 16 pounds in weight.
River spawning is very rare. The males are first to arrive at the spawning areas, cleaning algae and sand from the rocky substrate at depths ranging from 1to feet. A inch female deposits approximately 18, eggs , eggs per pound of body weight over 1.
Following fertilization by one or more males, the eggs are left to fall between the rocks where they incubate with no parental care. The eggs hatch 4 to 5 months later in the spring of the following year. Lake trout generally mature at age 6 to 7, but in the north it may be delayed a few years. Following complete absorption of the yolk sac, the first food taken by the young is zooplankton. With increasing size, the diet shifts to a wide variety of aquatic and terrestrial invertebrates and eventually fish.
In deep lakes where forage fish are not available during the summer, Lake Trout populations rely on zooplankton, which results in slower growth during that period.
Management methods vary for each species, but all aim to keep fish populations healthy, balanced, and productive.
0コメント