Complex sentence: The roundnose grenadier ("Coryphaenoides rupestris ") and the onion-eye grenadier ("Macrourus berglax") were the only fish species of potential commercial importance-they were caught in mid water at depths of between and were up to a metre in length.
Split into simpler sentences: The roundnose grenadier ("Coryphaenoides rupestris ") and the onion-eye grenadier ("Macrourus berglax") were the only fish species of potential commercial importance. They were caught in mid water at depths of between and were up to a metre in length.