Feeding habits and gill raker morphology of three planktivorous pelagic fish species off the coast of northern and western Kyushu in summer

Feeding habits and gill raker morphology were examined for the three major planktivorous pelagic fishes, Japanese anchovy Engraulis japonicus , Pacific round herring Etrumeus teres and Japanese jack mackerel Trachurus japonicus , off the northern and western coasts of Kyushu, in the north‐eastern part of the East China Sea in the summer months of 2001. Using fishes in the same size range (80–140 mm, standard length), the stomach contents of the three fish species were compared. The diet of the Japanese anchovy mainly consisted of Oncaeidae copepods, while the diets of the Pacific round herring and Japanese jack mackerel were dominated by calanoid copepods at all stations. Comparisons between prey size in the stomach, zooplankton size in the water and gill raker morphology suggested that the stomach contents of the three species were characterized mainly by the difference in the feeding behaviour between Japanese anchovy (filter‐feeding) and the other two species (particulate‐feeding), rather than by the difference in the morphology of feeding apparatus only. It was concluded that behavioural adaptations in the feeding of these pelagic fishes brought about trophic partitioning to some degree in this pelagic ecosystem in summer. Although the diets of these three species overlapped to some extent, there was still little likelihood of competition between the Japanese anchovy and the other two species. The potential for competition between the Pacific round herring and the Japanese jack mackerel is discussed.