Microhabitat selection in intertidal gobiid fishes: Species- and size-associated variation

Patterns of space use and the individual-based behaviour of microhabitat selection were investigated in three intertidal gobiid fishes, Bathygobius fuscus, Chaenogobius annularis and C. gulosus, from Kyushu, southern Japan. While the three species tended to occupy slightly different types of tidepool, their patterns of distribution largely overlapped in the field. Laboratory experiments involving choice of shelter (i.e. underneath a stone plate) and four different substrate types were conducted to examine size- and time-related variation in habitat selection. The shelter area was preferred by small- and large-sized C. gulosus (day and night), large C. annularis (day and night) and small C. annularis (daytime only), while no preference was evident in small B. fuscus (day and night) and small C. annularis (night). Patterns of substrate choice also differed among species, size groups and between day and night. Size differences in substrate use were evident in B. fuscus and C. gulosus but not in C. annularis, while diel differences were shown by all species groups except large B. fuscus. The gravel and sand substrates tended to be used more frequently than the bare rock substrate, but the strength of preference of a particular substrate type varied among individuals/species. Our results demonstrate that habitat selection by the three gobiid species is variable depending on species, body size and time of day, which must ultimately bear upon mitigating intra-/interspecific interactions in tidepool environments.