DeMartini, E. E.

Habitat and endemism of recruits to shallow reef fish populations: Selection criteria for no-take MPAs in the NWHI Coral Reef Ecosystem Reserve

2003

Bulletin of Marine Science

74

1

185-205

"Temporal abundance and spatial distribution patterns are described for shallow (< 15 m-deep) reef fish populations at French Frigate Shoals (FFS) and Midway Atoll (Midway), two isolated oceanic atolls 800 km apart in the NW Hawaiian Islands (NWHI), during 1992-93 and 1995-2000. Particular emphasis is given to two complementary (young-of-year = yoy, and older) life stages whose relative abundances differed between FFS and Midway. Older fishes averaged one-third higher in density at FFS, whereas yoy were two-threefold higher at Midway. Populations of fishes at the two atolls thus have different underlying temporal dynamics. Endemic species were generally important at both atolls, especially at Midway, farther upchain (and downcurrent) in the archipelago. The yoy of Hawaiian endemics were disproportionately numerous, which may indicate more consistent recruitment of endemics - an observation worthy of further evaluation elsewhere. Despite the whole reef-scale differences in yoy densities between atolls, habitat effects on yoy were largely consistent at both. The size/age composition of fishes differed among habitats, with yoy dominating numerically on semi-sheltered backreefs and especially on sheltered lagoonal patch reefs. This is likely due to two related factors: the wave-sheltered location and the relative abundance of small-sized shelter (coral rubble and branching corals) in (semi) sheltered habitats compared to the scoured limestone and large-scale 'spur-and-groove' relief of wave-exposed forereefs. In the NWHI, extensive areas of (semi)sheltered habitat occur only at emergent and drowned atolls that are increasingly represented in the more ancient, northwestern part of the archipelago. The potential importance of sheltered atoll lagoons as juvenile nursery habitat makes atolls prime candidates for consideration as no-take Marine Protected Areas within the provisional NWHI Coral Reef Ecosystem Reserve and perhaps elsewhere. This tentative conclusion justifies a long-term evaluation of spatial variations in recruitment among habitats of varying wave exposure at additional atolls, at other more wave-exposed fringing reefs surrounding basalt pinnacles in the NWHI, and at other oceanic atolls and continental reefs. "

FY2003 CRCP Project ID 1086; Project Title: Long-Term Monitoring of Reef Fish, U.S. Pacific Islands; Principal Investigator: Edward DeMartini