Complex sentence: The "Law on Fisheries" requires setting total allowable catch (TAC) levels for fishery stocks, which it defines as the "scientifically justified annual catch of aquatic biological resources of particular species in a fishing area".
Split into simpler sentences: The "Law on Fisheries" requires that total allowable catch (TAC) levels are set for fishery stocks. It defines these levels as the "scientifically justified annual catch of aquatic biological resources of particular species in a fishing area".