Complex sentence: They may not be the most elusive fish in the river, in fact, in the right conditions are fairly easy to catch they are however a very hardy fish who will fight right until you slip your landing net under them.
Split into simpler sentences: They may not be the most elusive fish in the river; in fact, in the right conditions they are fairly easy to catch. They are, however, very hardy fish who will fight right until you slip your landing net under them.