Subtidal reef fish and macrobenthic community structure at the temperate Juan Fernandez Archipelago, Chile

Abstract

ABSTRACT. The Juan Fernández Archipelago (33º37'S, 78º51'W), an isolated group of islands 650 km west of continental Chile, has a high degree of endemism in its marine biota. Despite numerous scientific expeditions to these islands that have identified this high endemism, few studies have attempted to identify patterns of community structure in subtidal habitats. Using visual census, we surveyed fish and habitat associations at five sites located at two of the three islands of the archipelago. Given the isolation of the archipelago we asked: What is the composition of the reef fish fauna at these isolated islands? What habitats dominate subtidal environments? What influences the abundances of reef fishes? Our analysis confirms that fish communities at the archipielago are dominated by endemic species. The ichthyofauna is comprised of a mixture of subtropical and temperate taxa, with greater similarity to western than eastern South Pacific fauna. We identified different fish assemblages at wave-exposed and wave-sheltered sites. Brown and red macroalgae were correlated with the abundances of some reef fishes. Four broad trophic categories of reef fishes were present at the archipelago, with invertebrate consumers dominating abundance. To our knowledge, this is the first attempt to quantify patterns of community structure in subtidal environments at the Juan Fernández Archipelago. Keywords: rocky reefs, fish assemblages, distribution, oceanic islands, Juan Fernández Archipelago, Chile.Estructura comunitaria del macrobentos y peces costeros submareales del archipiélago Juan Fernández, Chile RESUMEN. El archipiélago Juan Fernández (33º37'S, 78º51'W), es un grupo de islas situadas a 650 km al oeste de Chile continental, con alto grado de endemismo en su biota marina. A pesar de numerosas expediciones científicas a estas islas que han identificado este alto endemismo, pocos estudios han tratado de identificar los patrones de estructura de la comunidad en hábitats submareales. Mediante censos visuales, se registraron los peces y su asociación con el hábitat en cinco sitios de estudio, en dos de las tres islas del archipiélago. Dado el aislamiento del archipiélago nos preguntamos: ¿Cuál es la composición de la fauna de peces de arrecife en estas aisladas islas? ¿Qué hábitats dominan los ambientes submareales? ¿Qué influye en la abundancia de peces de arrecife? Los análisis realizados sugieren que la comunidad de peces en el archipiélago está dominada por especies endémicas. La ictiofauna se compone de una mezcla de taxa de origen subtropical y templado, con una mayor similitud a las especies del Pacífico occidental que a las del Pacífico suroriental. Se identificaron diferentes ensambles de peces en sitios expuestos y protegidos. Las macroalgas pardas y rojas limitaron la abundancia de algunos peces de arrecife. Cuatro categorías tróficas de peces de arrecife, estuvieron presentes en el archipiélago, siendo los invertívoros los consumidores dominantes. Hasta donde se sabe, este es el primer intento en identificar los pat...

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

“…In fact, the first marine protected areas around these islands were created in the last two years, 10 years behind those established in continental Chile. 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.…”

“…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.…”

“…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. Rodríguez-Ruiz et al (2014) also conducted recent research in Juan Fernández Archipelago, characterizing coastal communities, from the intertidal to the subtidal zone, studying the three recently created Marine Parks: Tierras Blancas, El Arenal and El Palillo.…”

“…Pérez-Matus et al (2014) suggest that habitat-structuring species (e.g., brown algae) explain fish species composition, since differrences in the composition of substratum species and architectural complexity, rather than changes in abiotic factors such as depth, drive species composition and abundance. To explain the patterns of species abundance and distribution in inter and subtidal areas reported above, Rodríguez-Ruiz et al (2014) suggest the following processes structuring coastal communities: a) low grazing levels in intertidal zones (explained by low richness and abundance of grazers, which cannot control primary producers, thus the community is dominated by algae), b) a potential trophic cascade (which may explain the negative correlation between invertebrate abundance and fish abundance, which in turn is negatively correlated with fur seal abundances), c) sediments enrichment (biodeposits from the fur seal colonies in coastal sediments may support the higher biomass of depositfeeding sea cucumbers at sites hosting fur seals, compared with sites farther away from such naturallyenriched habitats; i.e., El Palillo), and d) disturbance (specifically sand dynamics, which may explain the dominance of different functional groups of algae among sites).…”

Cobble community DNA as a tool to monitor patterns of biodiversity within kelp forest ecosystems

“…Extensive research and monitoring of kelp forests along temperate shores have revealed productive communities with abundant diversity, fisheries and long histories of community use (Krumhansl et al, ; Pérez‐Matus, Ramirez, & Eddy, ; Teagle, Hawkins, Moore, & Smale, ). The Partnership for Interdisciplinary Studies of Coastal Oceans (PISCO) conducts annual monitoring surveys of macroalgae, invertebrates and fishes aimed to measure large‐ and small‐scale spatial patterns of the structure and function of kelp forest communities as well as characterize changes over time.…”