Complex sentence: For example the native Red Squirrel population suffered dramatically with the introduction of the American Grey Squirrel, which carries the squirrel pox virus, while Brown Trout cannot compete with the larger and more aggressive Rainbow Trout.
Split into simpler sentences: For example the native Red Squirrel population suffered dramatically with the introduction of the American Grey Squirrel, which carries the Squirrel pox virus. This is also the case with Brown Trout, which are cannot compete with the larger and more aggressive Rainbow trout.