Examination of a great abundance of filefish, Pervagor spilosoma, in Hawaii

Synopsis

The endemic filefish Pervagor spilosoma appeared in exceptionally large numbers throughout the major Hawaiian Islands during the spring of 1985 and remained abundant through 1988. We examined this occurrence with a perspective gained from studies of reef communities at the Island of Hawaii by one or both of us during most years from 1969 to 1994. P. spilosoma is known to vary in numbers, but such great abundances are rare. Although the species is considered a reef fish, individuals constituting the abundance were mostly in the water column, and spread from coastal reefs to the pelagic zone offshore. One might assume they represented an extraordinary recruitment of pelagic juveniles in the process of shifting to benthic habits, but our data indicate a more complex situation. Individuals in the water column tended to be larger than individuals near the reef, and although the former were feeding on plankton when collected, many had shifted to planktivory from earlier feeding on the benthos. Also, many in the water column were ailing, with moribund and dead individuals common, and these tended to carry parasites of types known to induce their hosts to rise toward the surface. We suggest that the great number of filefish we observed above near-shore reefs represented the shoreward fringe of a vast pool of individuals, varied in age, that had accumulated during the exceptionally long pelagic-juvenile period that is characteristic of tetraodontiforms.