A shrimp successfully defends itself against an octopus:
Animals eat animals. The human animal has a choice though. The ethics of humans eating animals based upon their intelligence or sentience seems to have less footing than the ethics of eating animals based upon how they were treated ... since the more we observe animals the more intelligence they appear to possess. (That is, if you choose to eat animals.)
Back to that prior post ... I think imprisoning one sentient animal in a glass jar for the purpose of feeding it to another sentient animal imprisoned in a glass tank - so we may watch - is ruthless. At least give the shrimp some ability to get away.