Fishermen is a technical term used within the Polkadot blockchain protocol to refer to full nodes who are responsible for the network’s and nodes’ integrity. Fishermen are responsible for monitoring the relay chain and other parts of the protocol in order to detect and report abnormal behavior to validator nodes. Fishermen monitor the process to ensure that no invalid state transactions are included, rather than packaging state transitions and producing the next parachain blocks like Polkadot collators. Fishermen typically stake a small amount of DOT at first and are rewarded for detecting undesirable network behavior.