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

Abstract

An expedition to Salas y Gómez 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 Gómez (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 Gómez. Fish biomass at Salas y Gómez 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 Gómez suggest mesopredator release consistent with recent shark fishing. The fish fauna at the seamounts between Easter Island and Salas y Gómez, 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 Gómez 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.

Overview of recent advances in oceanographic, ecological and fisheries research on oceanic islands in the southeastern Pacific Ocean

“…This low sampling effort explains why the species richness of seamounts inside the EEZ is only 7% of that found on seamounts near Salas y Gómez Island, outside the EEZ . The same pattern is found when analysing different taxa individually (7.4% fishes, 2.6% for crustaceans; in Fernández et al, 2014, estimated from Parin et al, 1997Stocks, 2009;Friedlander et al, 2013). These results show how little we currently know about biodiversity on seamounts.…”

“…Only during the last decade were conducted the first explorations to characterize the biodiversity of marine communities associated with seamounts in the Juan Fernández Archipelago (Yañez et al, 2009) and Salas y Gómez Island (Friedlander et al, 2013). Although we highlight these contributions within the EEZ of Chile, the review by Fernández et al (2014) suggests that sampling effort is still poor for this area.…”

“…It is also remarkable that spatial patterns of distribution of functional community structure did not follow geographic characteristics, but rather showed a strong similarity in benthic and fish functional groups among sites, suggesting a strong coupling with coastal oceanographic conditions that varies on small scales. Wieters et al (2014) not only analyze spatial patterns, but also report temporal variability in the functional structure of shallow hard bottom communities, showing a consistent increase in coral abundance in shallow habitats over the past 15 years despite the deterioration of fish assemblages (low fish abundances and small body sizes due to fishing pressure; Friedlander et al, 2013). Disturbance, changes in coral settlement, released competition and escape from predation are some of the processes proposed by Wieters et al (2014) to explain the observed patterns.…”

“…This occurred in spite of the high concentration of endemic species Pérez-Matus et al, 2014;Rodríguez-Ruiz et al, 2014) and growing fishing pressure around Chile's oceanic islands Zylich et al, 2014). Nonetheless, a few sporadic studies, associated with both national (e.g., CIMAR, Yáñez et al, 2008) and international initiatives (e.g., Friedlander et al, 2013), have contributed to our knowledge of the ecosystems associated with seamounts and oceanic islands in Chile. This special volume presents a review and analysis of the current information available on marine ecosystems associated with the oceanic islands in the Juan Fernández Archipelago and Easter Island Province (Easter and Salas y Gómez islands).…”

“…Recent studies in Easter, Salas y Gómez, and Robinson Crusoe islands have focused on community structure. Additionally to the comparative work by Friedlander et al (2013), Pérez-Matus et al (2014), Wieters et al (2014) and Rodríguez-Ruiz et al (2014) report the most recent studies conducted in the inter and subtidal in the representative habitats of Juan Fernández Archipelago and Easter Island that characterize community structure. Pérez-Matus et al (2014) characterized the coastal ichthyofauna of Robinson Crusoe Island, presenting the first analysis of reef fish and macrobenthic community structure in Juan Fernández Archipelago.…”