Depth distribution and abundance of benthic organisms and fishes at the subtropical Kermadec Islands

Abstract

Subtidal areas of the Kermadec Islands have not previously been described; samples from a bay at Raoul Island are discussed here. Abundances and percentage cover of benthic organisms were assessed from the high intertidal to 20 m depth using quadrat sampling. Fish abundances were assessed subtidally by random transects in shallow (3-6 m deep) and deep (14-20 m) areas of the reef. Hard corals occurred at 2-18 m depths at densities of 5 colonies per m 2 , but colonies were generally small. Soft coral colonies occurred at similar densities, but were confined to depths of 5-13 m. The mean percentage cover of corals did not exceed 20% at any one depth, and coral reefs did not occur. Fucalean and laminarian algae were not seen. The most abundant algae were foliose and filamentous species, and encrusting red algae. These covered over 80% of the reef at some depths. Grazing invertebrates were not abundant. Echinoids were found primarily in shallow water, reaching a density of 5 per m 2 at 5 m depth. The most abundant gastropod was the endemic limpet, Patella kermadecensis, which reached densities of 21 per m 2 , and was confined entirely to a zone in the low intertidal-shallow subtidal region. Mid to high intertidal areas were mostly barren, with high numbers of Nerita atramentosa, but few other invertebrates. Forty-five species of fish were seen, 11 of which were new records for the Kermadec Islands. Several herbivorous fish (kyphosids, pomacentrids, and aplodactylids) were found mostly on shallow areas of the Corals were sparsely distributed and stands of large brown algae were not encountered. Sea urchins were abundant in patches, whereas larger herbivorous fish were found only in shallow water. The geographic isolation of these islands and their relatively recent geological history may be the most important factors affecting species composition for this area of the Pacific Ocean.

Confirmation ofParma polylepis,a pomacentrid teleost, in New Zealand waters (note)

“…Parma polylepis has previously been reported from the Kermadec Islands by Paulin & Stewart (1985) and Schiel et al (1986). Francis et al (1987) have shown that those reports were based on misidentifications of the recently described and morphologically similar P. kermadecensis (though Allen (1987) was apparently unaware of the reports and did not include them in the synonymy of P. kermadecensis).…”

“…Parma kermadecensis is endemic to the Kermadec Islands, where it is common to abundant (Allen 1987;Francis et al 1987). Parma polylepis Gunther, 1862 was reported from the Kermadec Islands by Paulin & Stewart (1985) and Schiel et al (1986), but their reports were based on misidentified P. kermadecensis (Francis et al 1987). Therefore there are currently no valid reports of P. polylepis from New Zealand waters.…”

Patterns of abundance and population size structure of herbivorous fishes at the subtropical Kermadec Islands and in mainland New Zealand

“…Some of those areas may also have abundant laminarian macroalgae (e.g., Houtman Abrolhos- Hatcher & Rimmer 1985;Solitary Islands-Veron et al 1974;Harriot et al 1994). Subtropical areas described to date mainly harboured browsing piscine herbivores such as kyphosids and girellids, although herbivorous pomacentrids also occur (e.g., Schiel et al 1986;Cole et al 1992;Francis 1993Francis , 1996. Kyphosid and girellid fishes may be abundant (Hatcher & Rimmer 1985;Schiel et al 1986; review of Choat 1991;Cole et al 1992), but patterns of abundance along depth gradients are unknown.…”

“…The geography, geology, and biogeography of these groups have been reviewed by Hoggett & Rowe (1988), Francis (1993), and Brook (1998a). Kermadec Islands are one of the more thoroughly described of the subtropical areas (Nelson & Adams 1984;Schiel et al 1986;Francis et al 1987;Cole et al 1992;Francis 1993Francis , 1996Brook 1998aBrook ,b 1999. Kermadec Islands possess a flora of inconspicuous macroalgae (Nelson & Adams 1984;Schiel et al 1986) and a limited fauna of scleractinian corals (Brook 1999).…”

“…Kermadec Islands are one of the more thoroughly described of the subtropical areas (Nelson & Adams 1984;Schiel et al 1986;Francis et al 1987;Cole et al 1992;Francis 1993Francis , 1996Brook 1998aBrook ,b 1999. Kermadec Islands possess a flora of inconspicuous macroalgae (Nelson & Adams 1984;Schiel et al 1986) and a limited fauna of scleractinian corals (Brook 1999). The piscine fauna has been assessed in some detail (Francis et al 1987;Francis 1991Francis , 1993Francis , 1996 and includes kyphosid, girellid, aplodactylid, and pomacentrid fishes.…”