| Budget Amount *help |
¥1,900,000 (Direct Cost: ¥1,900,000)
Fiscal Year 1989: ¥300,000 (Direct Cost: ¥300,000)
Fiscal Year 1988: ¥500,000 (Direct Cost: ¥500,000)
Fiscal Year 1987: ¥1,100,000 (Direct Cost: ¥1,100,000)
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| Research Abstract |
Pinkgray goby, Amblychaeturicliys hexanema (BLEEKER), occur significantly in boat-seining grounds aiming at shirasu, a commercial name of postlarvae of anchovy and sardine, in the northwestern Suruga Bay. The gobby may insert appreciable influence upon commercially important clupeids postlarvae. The author examined weight, and species and size composition of contents of digestive tract for clarifying food habits of the postlarval gobbles. The study provides clues to understand competition between the gobies and clupeids.
1. Postlarvae of pinkgrey gobies and related species inhabit near the sea floor around 10 m depth in day-time, together with postlarval clupeids.
2. In the northwestern Suruga Bay postlarvae of pinkgrey gobies, together with common gobby, Acanthogohius flavimanus Temminck & Schlegell, occur most abundantly during early April through mid- May when water temperature remains at 15.0ﾟ-16.5ﾟC, and then reduce its abundance with rise of temperature to 18.0ﾟ-19.6ﾟC.
3. Zooplankton comprise major food items of postlarvae and juveniles of pinkgrey gobbles. Dominant species in digestive tract change by size of fish: nauplii of copepods for the fish less than 8.1 mm in total length, and Calanus in addition to the above nauplii and Paracalanus, Acartia, Corycaetis and Appendicularia for the larger fish.
4. Content of digestive tract of gobbies differ both in species and size of individuals from plankton in net collection. The difference indicates selective feeding of juveniles of pinkgrey gobbies to zooplankton. It is assumed that gobbles selectively take the food items by size but not by species, because the fish avoid very small copepods of 0.60-0.69 mm in total length bat eat larger individuals.
5. juveniles of pinkgrey gobby share the same habitat and food organisms with postlarval anchovy and sardine. The postlarval clupeoids may be competing with pinkgrey gobbies as well as common gobbles when the latter increase in number during spring.
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