What lives in streams?

What lives in strems? well two things are insects and fish ofcourse. Pictured above is a mayfly or Ephemeroptera. This is its adult stage where it may only live a short time (1-2 weeks or shorter) before it dies. Its main goal at this time is to mate and pass on its genes. Since they live a short time they may not have any functioning mouthparts and therefore don't eat. Amazing right? I must admit since studying stream organisms I have a new found fascination for the little buggers. The picture below is a newly hatched fish, trout to be specific. This one is from the Family Salmonidae.