Predominance of cross-predation between lateral morphs in a largemouth bass and a freshwater goby.

The predator-prey relationship between largemouth bass, Micropterus salmoides, and freshwater goby, Rhinogobius spp., in Lake Biwa, Japan, was examined with respect to their morphological antisymmetry (laterality). Largemouth bass and Rhinogobius gobies exhibited lateral dimorphism in the height of the mandible and the length of the dentary, respectively. Populations of both species were composed of both left-developed and right-developed individuals. Each predation event was categorized as either cross-predation (a predator caught prey of the opposite morph) or parallel-predation (a predator caught prey of the same morph). Stomach contents analysis revealed that cross-predation events predominated over parallel-predation. Annual sampling for eight years demonstrated that in both largemouth bass and Rhinogobius gobies, the ratio of right-developed individuals in the population fluctuated temporally around 0.5. As the predominance of cross-predation was found in the relationship between the exotic largemouth bass and an endemic goby, the predominance may be caused by a kinematical interplay at each predation event.