An clabater is some form of strange fish, as described by Caldemeyn in the short story The Lesser Evil. Apparently they can be of interest to mages.
"You're not stupid, Carrypebble. Listen, Geralt, maybe our local wizard will spare you something for that carcass. The fishermen bring him the oddest fish — octopedes, clabaters or herrongs — many have made some money on them."
- - pg.78, The Last Wish (UK edition)
- In Danusia Stok's translation, the list of strange fish is one monster short. The original quote in Polish does not say "fishermen bring him the oddest fish — octopedes, clabaters or herrongs", but rather "fishermen bring him dziworyby, octopedes, clabaters or herrongs". The name for "dziworyba" is not translated into English.
- To be fair, "dziworyba" does roughly translate to "odd" or "weird" fish, but in the original Polish text, it is listed as an instance of a creature, not a catch-all expression.
- In German folkore, there is sea creature, a kind of water sprite, known as a Klabautermann. It's possible the reference comes from this tale.