The Delaware River walleye remain as they have always been _ the antique fish that Ray Bergman trolled sea lamprey larvae for in deep, nameless and secret pools.
42.
Across its range it is in decline, and it is listed as Vulnerable to global extinction by the IUCN Red List . and also by sea lamprey predation
43.
Peggy Minnis was explaining that the invasion of the sea lamprey into the Great Lakes may have been eased by the locks in the canal that joined the lakes.
44.
Trolling sea lamprey larvae at night through unnamed Delaware River pools, they catch plenty of walleye up to five pounds, and hook an unseen monster that straightens the hook.
45.
Conversely, the construction of artificial channels has exposed new habitats for colonisation notably in North America where sea lampreys have become a significant introduced pest in the Great Lakes.
46.
Research was done to find a way to prevent the migration of the sea lamprey into Lake Couchiching and Lake Simcoe, while still effectively increasing the flow of traffic.
47.
However, logging operations, fishing and the installation of an electric barrier to prevent sea lampreys from travelling upstream ( removed in 1960 ) have reduced sturgeon activity in the river.
48.
Fishing was at its peak in the early 20th century, but suffered from the introduction of the invasive sea lamprey to the upper Great Lakes through the Welland Canal in 1921.
49.
Disrupting the sea lamprey's mating call may be the key to limiting its numbers in the Great Lakes, where the eel-like parasite sucks the life out of sport fish, scientists say.
50.
The sea lamprey is an aggressive predator by nature, which gives it a competitive advantage in a lake system where it has no predators and its prey lacks defenses against it.
