The shallow-water fish assemblage of Isla del Coco National Park, Costa Rica: structure and patterns in an isolated, predator-dominated ecosystem

Alan M Friedlander,Allan Bolaños,Brian J Zgliczynski,Enric Ballesteros,Enric Sala,Octavio Aburto-Oropeza

doi:10.15517/rbt.v60i3.28407

Abstract

Fishes at Isla del Coco National Park, Costa Rica, were surveyed as part of a larger scientific expedition to the area in September 2009. The average total biomass of nearshore fishes was 7.8 tonnes per ha, among the largest observed in the tropics, with apex predators such as sharks, jacks, and groupers accounting for nearly 40% of the total biomass. The abundance of reef and pelagic sharks, particularly large aggregations of threatened species such as the scalloped hammerhead shark (up to 42 hammerheads ha-1) and large schools of jacks and snappers show the capacity for high biomass in unfished ecosystems in the Eastern Tropical Pacific. However, the abundance of hammerhead and reef whitetip sharks appears to have been declining since the late 1990s, and likely causes may include increasing fishing pressure on sharks in the region and illegal fishing inside the Park. One Galapagos shark tagged on September 20, 2009 in the Isla del Coco National Park moved 255km southeast towards Malpelo Island in Colombia, when it stopped transmitting. These results contribute to the evidence that sharks conduct large-scale movements between marine protected areas (Isla del Coco, Malpelo, Galápagos) in the Eastern tropical Pacific and emphasize the need for regional-scale management. More than half of the species and 90% of the individuals observed were endemic to the tropical eastern Pacific. These high biomass and endemicity values highlight the uniqueness of the fish assemblage at Isla del Coco and its importance as a global biodiversity hotspot. Citation: Friedlander, A., B.J. Zgliczynski, E. Ballesteros, O. Aburto-Oropeza, A. Bolaños & E. Sala. 2012. The shallow-water fish assemblage of Isla del Coco National Park, Costa Rica: structure and patterns in an isolated, predator-dominated ecosystem. Rev. Biol. Trop. 60 (Suppl. 3): 321-338. Epub 2012 Dec 01.

Highlights

Isla del Coco, Costa Rica, is known worldwide for its aggregations of sharks and other mega-fauna (Bakus 1975, Garrison 2005)
Isla del Coco is located in the Eastern Tropical Pacific (ETP) Biogeographic Region, which is delimited by the Gulf of California southward to the northern boundary of Peru and includes five oceanic islands and archipelagos (Hastings 2000; see Figure 1)
Endemism and biogeography: More than 50% of the species and 91% of the individuals surveyed on belt transects at Isla del Coco are endemic to the ETP (Table 2)

Summary

Introduction

Isla del Coco, Costa Rica, is known worldwide for its aggregations of sharks and other mega-fauna (Bakus 1975, Garrison 2005). It. Isla del Coco is located in the Eastern Tropical Pacific (ETP) Biogeographic Region, which is delimited by the Gulf of California southward to the northern boundary of Peru and includes five oceanic islands and archipelagos (Hastings 2000; see Figure 1). Within the ETP, there are three major recognized biogeographic provinces: 1) Cortez (Gulf of California and lower Pacific Baja), 2) Panamic (southward along the continental margin to Peru), and 3) the five oceanic islands/archipelagos including Galapagos, Isla del Coco and Malpelo (Robertson & Cramer 2009). 5o30’ N local conservation organizations conducted a scientific expedition to Isla del Coco and Las Gemelas seamounts, Costa Rica, from September 9 to 24, 2009. The goals of the expedition were to: 1) describe the biogeography and endemism of the nearshore fish assemblage; 2) measure the abundance, size, and biomass of reef and pelagic fishes, including sharks at Isla del Coco National Park; 3) conduct a preliminary assessment of the migratory movements of sharks; and 4) explore and survey deep habitats in the National Park and the unprotected Las Gemelas seamounts south of the Park (see Starr et al 2012)

Methods

Results

Conclusion