Commercial fishing kills enormous quantities of invertebrates as bycatch, including starfish, sea urchins, and crustaceans whose welfare significance is uncertain but whose deaths occur at massive scale.
The welfare significance of invertebrate bycatch depends on whether specific taxa experience suffering. For decapod crustaceans — now recognized as likely sentient — the bycatch welfare question is particularly important. For other invertebrates the question remains genuinely uncertain. The scale of invertebrate fishing mortality warrants application of the precautionary principle while science advances.