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.

The Effect of Feeding Habitats on Dietary Shifts during the Growth in a Benthophagous Suction-Feeding Fish

“…This fish takes small benthic animals from the substrate using a suctorial feeding mode without visual discrimination towards individual prey (Matsumoto, 2001). We found many individuals of G. zonatus at two locations: plenty of calcareous algal patches, one of the main feeding substrates of this fish, in one site, whereas scanty in the other.…”

“…Underwater observations were made between 09:00 and 17:00 hr, when G. zonatus actively foraged (Sano and Moyer, 1985;Matsumoto, 2001). Each identified individual was focally followed for ca.…”

“…Total observation time per individual ranged from 27.3 min to 365.0 min (on average 134.7 min ± 87.1 SD, n=46). This species forcefully thrusts the mouth against the substrate and takes prey organisms together with sediment using powerful suctorial force produced by the rapid expansion of the buccal cavity, and then filters out the sediment through the gill openings (Matsumoto, 2001). The fish often repeatedly sucks at the same site on calcareous algal mat so as to exploit infaunal organisms inhabiting inside the algal mat, whereas usually takes single sporadic suctions on other substrates (Matsumoto and Kohda, 2001a).…”

“…We recorded sucking number with discrimination of substrate types (algal mat, bare rocks, sand and corals). Goniistius zonatus maintains a feeding territory against conspecifics of similar size (Matsumoto, 2001). Swimming tracks of the identified individuals were recorded (for ca.…”

“…Swimming tracks of the identified individuals were recorded (for ca. 1 hr for each) at the two sites in 1994, and an area enclosed by outermost total swimming tracks was defined as a territory for each fish (Matsumoto, 2001). …”