Effects of isolation and fishing on the marine ecosystems of Easter Island and Salas y Gómez, Chile

An expedition to Salas y Gomez and Easter islands was conducted to develop a comprehensive baseline of the nearshore marine ecosystem, to survey seamounts of the recently created Motu Motiro Hiva Marine Park (MMHMP) – a no-take marine reserve of 150 000 km2 – and to compare these results with Easter Island where the marine ecosystem is similar but has no marine protection. Live coral cover was surprisingly high at both Easter Island (53%) and Salas y Gomez (44%), especially considering their sub-tropical location, high wave energy environments, and geographic isolation. Endemic and regionally-endemic species comprised 77% of the fish abundance at Easter Island and 73% at Salas y Gomez. Fish biomass at Salas y Gomez was relatively high (1.2 t ha-1) and included a large proportion of apex predators (43%), whereas at Easter Island it was almost three times lower (0.45 t ha-1) with large predators accounting for less than 2% of the biomass, despite good habitat quality. The large cohort of small sharks and the absence of larger sharks at Salas y Gomez suggest mesopredator release consistent with recent shark fishing. The fish fauna at the seamounts between Easter Island and Salas y Gomez, outside of MMHMP, harboured 46% endemic species, including a new species of damselfish (Chromis sp. nov.) and probably a new species of Chimaera (Hydrolagus). Numerous seamounts adjacent to Salas y Gomez are currently not included in the MMHMP. This expedition highlights the high biodiversity value of this remote part of the Pacific owing to the uniqueness (endemicity) of the fauna, large apex predator biomass, and geographic isolation. Copyright © 2013 John Wiley & Sons, Ltd.