Egg size variation between the fluvial-lacustrine and lacustrine types of a landlocked Rhinogobius goby in the Lake Biwa water system

The egg size of a landlocked goby, Rhinogobius sp. (the orange form), in the Lake Biwa water system was compared between the fluvial-lacustrine and lacustrine types. The former spawned larger eggs than the latter in the laboratory under the same environmental conditions of water temperature and current. This difference in egg size was also found in the field among six local populations from tributary rivers and lake shore. These results suggested that egg size is largely associated with the life history type that has experienced a different selection regimen, such as the risk of larval starvation, associated with their respective life cycles.