Five species of lampreys are found in the upper three Great Lakes. All species require certain physical factors for successful spawning such as suitable bottom substrates, water velocities, and temperatures. Nest construction (usually started by males) and spawning behavior are similar although some differences exist. In sea lamprey an average spawning act lasts about 2–5 s and is repeated every 4–5 min; generally nesting is monogamous with little polyandrous nesting (1.2–5.0%); average egg production is about 60 000 eggs. An estimated 86% of the eggs of sea lamprey are not deposited in the nests; however, the fertilization and survival of eggs deposited in the nest is high and may approach 90%.Key words: Petromyzon marinus, Ichthyomyzon unicuspis, I. castaneus, I. fossor, Lampetra lamottei, spawning requirement, nest construction, fecundity, nest productivity, water temperature
The external metamorphosis of the sea lamprey was divided into four stages, based primarily on the condition of the mouth: mouth reduced, mouth fused, mouth enclosed, and mouth elongated. During metamorphosis, the eye enlarged greatly, the snout and mouth region changed from a fleshy hood enclosing a sieve apparatus to a large sucking disc, the nasopore membrane and the branchial area shrank, the branchiopores changed in shape, the general color changed from dark brown and yellow to an intense blue-black dorsally and white ventrally, and the total length increased. Metamorphosis began in early to mid-July and did not take place after August. The duration of external metamorphosis was about 3 months for lampreys transforming under natural conditions. The mean lengths of metamorphosing lampreys from tributaries of lakes Superior and Michigan were 145 and 136 mm, respectively.
The sterility method of pest control could be an effective tool in the sea lamprey (Petromyzon marinus) control program in the Great Lakes. Some of the requirements for its successful application have been met. A field study demonstrated that the release of male sea lampreys, sterilized by the injection of 100 mg/kg of P,P-bis(1-aziridinyl)-N-methylphosphinothioic amide (bisazir), will reduce the number of viable larvae produced. The actual reduction in reproductive success that occurred was directly related to the ratio of sterile to normal males in the population. The technique can be used in many ways in an integrated control program and has considerable potential for the more effective control of the sea lamprey. Eradication is a distinct possibility.Key words: sea lamprey, Petromyzon marinus; pest control, fish control, sterile-male technique, sterilization, chemosterilants, bisazir, Great Lakes
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