gillnets with cath juvenile perch

angling animal apex aquatic asp background beautiful biodiversity body bycatch catch cath close closeup conservation depletion detail ecological ecosystem entanglement entrapment environmental escapement european eyes fauna fin fish fisheries fisherman fishery fishing fleet freshwater gear genus gillnets green habitat harvesting head impact juvenile lake life management measure mesh monitoring mortality nature net number overexploitation overfishing perch population predator predatory rate recruitment regulation reservoir river riverine sampling school selectivity shoal species specimen stocking survival sustainability top unintended water wild wildlife