lesson 5: trout: predator or prey?

reading 5.1

  • On the English and Scottish coasts, more than 24,000 puffin nests were empty.
  • Puffins are sea birds that build their nests in the cliffs along the ocean coasts.
  • They eat sand eels. Sand eels live in the surrounding waters of the North Sea.
  • The sand eels have disappeared.
  • Sand eels are a main food source for the puffin, because the puffin does not have a lot of prey.
  • They have to fly long distances, using energy, so they cannot lay eggs.
  • Sand eels eat cold water plankton.
  • The plankton in the North Sea moved north because the water was too warm.
  • Sand eels prefer cold-water plankton over warm-water plankton because they are bigger and have more calories.
  • Puffins also have to compete with other seabirds for sand eels.

The decrease in plankton affects a lot of populations. It could lead to many changes in the ecosystem.

reading 5.2

What do you think would happen if a new organism suddenly came into an ecosystem? What things might it affect?

It might affect the numbers of populations in the ecosystem.

  • It might overeat producers.

  • It might multiply rapidly in population if it doesn't have any predators in the new ecosystem.

  • the fish decreased in number since the previous year

  • there are wounds on the big fish, eg trout

  • quarter-sized wound, blood loss

  • this is due to an invasive species

  • sea lamprey is causing trout to decrease

invasive species

what is an invasive species?

a species that is non-native to its ecosystem. It can cause harm to the environment, economy, or humans. Example: brown marmorated stink bug

how does a species become invasive?

  • very successful in their new ecosystem
  • introduced by outside factors (humans)
  • grow and reproduce quickly
  • spread fast
  • cause harm to native species
  • tolerate variety of habitats and conditions
  • compete aggressively for resources
  • lack natural predators

  Example: red turpentine beetle

  What effect can invasives have?

  • displace native species
  • reduce native wildlife habitat
  • reduce forest health
  • alter ecosystem processes
  • degrade recreation areas

  Example: In Oregon, the woody adelgid displaced the native trees of anthony lakes.

  What can be done with them?

  • research can be conducted to learn more about them
  • eradication efforts can be sped up.
  • observations can be increased. we can regularly monitor populations to easily detect and control infestations of invasive species.