It is unclear if the sea lamprey was native to Lake Ontario or not. But the
canals that connected the upper lakes to Lake Ontario, and Lake Ontario to the
Hudson, made it possible for the lamprey to enter all of the Great Lakes.
Lampreys are eel-like fishes that spend most of their long life cycle in the
sediments of the streams in which they spawn. They spend their eighteen
month parasitic phase patrolling open lake waters attaching themselves like
giant leeches to the sides of large fishes and sucking them dry.
The tributaries that had transported logs and were subject to scouring
during rain events were transformed into nearly ideal lamprey habitat. As they
moved into their new homes after the logging was completed, they went largely
unnoticed because of their small numbers and relatively long life cycle. But with
abundant food, and no natural competition, they bred unchecked. Within two
or three lamprey generations, the population of piscivorous fish started to
decline dramatically.
With the fish-eating fish on the decline, there was no natural control for the
planktivores – the fish that eat zooplankton. Their populations exploded. The
faster one species could eat, the more that species could out-compete rivals.
The introduced alewife, with its ability to use three feeding methods, not only
grew its population, but also out-competed the native herring and ciscoes. And
the population of zooplankton collapsed.
It is unclear if the sea lamprey was native to Lake Ontario or not. But thecanals that connected the upper lakes to Lake Ontario, and Lake Ontario to theHudson, made it possible for the lamprey to enter all of the Great Lakes.Lampreys are eel-like fishes that spend most of their long life cycle in thesediments of the streams in which they spawn. They spend their eighteenmonth parasitic phase patrolling open lake waters attaching themselves likegiant leeches to the sides of large fishes and sucking them dry.The tributaries that had transported logs and were subject to scouringduring rain events were transformed into nearly ideal lamprey habitat. As theymoved into their new homes after the logging was completed, they went largelyunnoticed because of their small numbers and relatively long life cycle. But withabundant food, and no natural competition, they bred unchecked. Within twoor three lamprey generations, the population of piscivorous fish started todecline dramatically.With the fish-eating fish on the decline, there was no natural control for theplanktivores – the fish that eat zooplankton. Their populations exploded. Thefaster one species could eat, the more that species could out-compete rivals.The introduced alewife, with its ability to use three feeding methods, not onlygrew its population, but also out-competed the native herring and ciscoes. Andthe population of zooplankton collapsed.
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