1. Conger eel: This is the most common meaning of "congery." It refers to a large, predatory eel species (Conger conger) found in the North Atlantic Ocean.
2. A kind of fish: Historically, "congery" could also refer to any type of fish, although this usage is now obsolete.
Therefore, when you encounter the word "congery," it is most likely referring to a conger eel.