What are pyloric caeca, and how do they help salmonids digest food?

Pyloric caeca are fingerlike appendages that open off the intestine of a fish, located immediately posterior to the stomach.1

In salmonids, these structures play a vital role in the digestive process by secreting enzymes and providing additional surface area for digestion within the intestine. While there is a general tendency for more predacious salmonid species to possess a higher number of these appendages, the relationship between diet and the development of pyloric caeca is not consistent across all fish families; for instance, highly predacious pikes lack them entirely, while some algae-eating species possess them in great numbers.1