Sentence:  Loaches (or <WSD>beardies</WSD>) often also thinned our preserves, and in this they were occasionally helped by small eels. Whenever <WSD>beardies</WSD> got within an enclosure containing only creepers and caddis worms, in a very short space of time the <WSD>beardies</WSD> alone were left, so rapacious are these small fishes. 
Meaning of the word marked with <WSD> tags:  Any of several kinds of fish; a loach.