Yes... they do
Mainly the fishes which are poisonous , very small [ with a body made up of fins ], having more bones , having spines over the body , etc are not suitable for eating . Eg: Puffer Fish, Toad Fish
An echidna's body is covered with spikes, or spines. These spines are not poisonous, but they are sharp and offer the echidna protection from predators.
defensive
defensive
A body covered with spines is the reason why a saltwater fish has the name porcupine puffer. The ability to inflate their bodies to twice the ordinary vertical size and to make porcupine-reminiscent sharp spines project even further outward serve as the Diodontidae family member's two main defenses. Porcupine puffers tend to be popular with saltwater aquarium owners because of docile behavior, slow speeds and unusual looks.
defensive nova net
Different puffers have different deterrents. Some simply inflate themselves to appear larger than they are to either scare the other predator or to prevent themselves from being swallowed. Some have spines along their body to damage a would be predator. A few are even poisonous. Puffers are a predatory fish and as such have fast growing, strong teeth that can tear fins and devour prey.
one spine
When the puffer fish inflates its body to increase its size it is a behavior called a defense mechanism. Puffer fish have highly elastic stomachs and the ability to quickly take in air or water to puff themselves up. This turns them into an inedible ball.
Mucus,spikes,scales.
Their spines
its scales, body, spines