most fish survive though you will notice the dramatic difference in their usual behaviour and wonder why.
I watched a program last night on parasites. The heron segment showed the heron fishing and releasing the parasite, which lives in the heron. The parasite enters the fish and the fish's reflexes slow way down, making it easy prey. The heron eats the parasite infested fish and the cycle starts over. The fish illustrated in the show was about 3" long and the parasite was about 2". BTW there is a parasite in about 50% of US citizens that has some what the same effect.
