Admittedly my attempt at this isn’t too far from the typical “they just eat fish” solution, but I thought it would be interesting to play with how they acknowledge their respective statuses as predators and prey.
The two species have different but complimentary funeral rites. When a prey animal dies, it is ritually butchered and its meat consumed by a predator. When a predator dies, seeds are buried with the body so their remains fertilize crops that are eaten by members of the prey species. Specific individuals or families are chosen by the deceased in their will to carry out this task, and the relationship is treated like being a godparent.
cf : all the predators now extinct like mountain lions in Europe