Defining Invasive Species

 Invasive species are species that are non-native to a certain habitat but have been introduced and are thriving in that area, resulting in the disruption of the habitat that was originally there. When people think of invasive species they often think of plants but animals can also be considered invasive when they have been brought into a new area and have begun to affect the population of animals already present.





Story of the Cutthroat and Rainbow Trout

The cutthroat trout are native to western North America and can be found in many freshwater rivers and streams (Hitt 2003). Many subspecies can be found but they are now in danger of extinction due to the loss or fragmentation of aquatic habitats, as well as the introduction of nonnative species. The coloration of the cutthroat trout can vary between species but they can usually be distinguished by two prominent red slashes on their lower jaw. They are also lightly spotted on the back and sides while the tails are more heavily spotted. Their long body allows them to easily maneuver through the rapid currents that can be found with their habitat (Coldwater Fish Species). Some species remain in the tributaries where they were born, others will migrate to lakes for some part of their life, while another group may migrate to the ocean during the spring and then return to freshwater to spawn much like the salmon life cycle.

The story with rainbow trout are a little more complicated because they are also considered to be native to western North America. They are anadromous, migrating to the ocean as juveniles and then returning to freshwater to lay their eggs. They can be recognized by their blue-green or yellow-green color pattern with a pink streak along their sides, a white belly and small black spots on their fins and back. They are able to survive on a variety of insects and crustaceans which has also allowed them to be successful through the country.

Although they are native species, their ability to thrive in hatcheries have allowed them to be introduced into lakes and rivers across the country.  They are now one of the top five most sought after species for fly fishers.  Rainbow trout stocking, this process of raising large number of fish in hatcheries, has brought about much controversy because the result of introduction of these nonnative rainbow trout species has had unintentional consequences on the surrounding freshwater biota such as the cutthroat trout(Rubidge 2011). The introduction of these fish into lakes and rivers has resulted in an increased competition for food and habitat.