Overlapping territory of a benthophagous fish, Goniistius zonatus (Teleostei: Cheilodactylidae)

Abstract

Overlapping territories of a benthophagous morwong, Goniistius zonatus, were studied at two temperate water locations (Morode and Arakashi) in southern Japan. At both locations, total length (TL) of the fish inhabiting the study areas ranged from 12 cm to 34 cm, but fish 20–25 cm TL were not found in the Arakashi study area. At Morode, individuals maintained territories against conspecifics of similar size, and the territories broadly overlapped among three size classes (small < 20 cm ≤ medium <25 cm ≤ large). At Arakashi, large‐sized fish chased individuals of both the same‐ and medium‐sized individuals from their territories, resulting in territory overlap only between large and small size classes. The territories were apparently maintained for feeding, as the main activity of the fish within the territories was foraging and no reproductive behavior was observed at either location. All fish foraged on similar substrates in the daytime. At Morode, however, the diet composition differed among different size classes, whereas at Arakashi, fish of all sizes fed on quite similar foods. A comparison between the two populations indicates that the territory overlap among the three size classes at Morode may have resulted from food‐resource partitioning.