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The present study compares the ecological patterns of macrofauna in sandy beaches between the Caribbean and Pacific coasts of Costa Rica. At each beach, the intertidal zone was divided into five strata from low to high tide level. In each stratum, sediment samples (corer area: 20.2 cm2, diameter: 5.07 cm) were collected to analyze the macrofauna. Additionally, grain size composition, total organic matter and carbonates of the sediments were determined. The macrofauna diversity was higher in the Pacific coast (15 taxa, per beach) than in the Caribbean (4 taxa, per beach). The most diverse taxon group was the annelids, followed by arthropods and mollusks. Within the mollusks, the bivalves and the gastropod family Olivellidae were only present in the Pacific coast. Both Caribbean and Pacific coasts had a vertical zonation of taxa distribution from high to low tide level. Typically, the low tide level was populated by several polychaetes, mid littoral by crustacean and mollusks, and the high tidal level was populated by isopods (Cirolanidae). Faunal differences in richness, abundance and composition of assemblages between both coasts can be explained by environmental differences. The tidal range is narrower on the Caribbean (0.5–1.5 m) than the Pacific coast (2–3 m). The slope of the beach is steep in several beaches of the Caribbean, whereas the Pacific has several dissipative beaches with gentle (or flat) slopes. The organic matter was lower (1.00%) in the Caribbean than in the Pacific (2.25%). In the Caribbean coast, the sediment is ∼90% fine sand (500–63 μm), while in the Pacific this fraction was ∼65%, resulting in more heterogeneous sediments in the Pacific. Finally, evidence of change in the abundance and species composition with the latitude in each coast was detected; indicating that these communities are highly variable within a local scale, which could be due to the diversity of sandy beaches and environmental variation that Costa Rica has in both coasts. Our results indicate that beaches with higher number of species or abundance were not necessarily designated as Marine Protected Areas. This information should be considered in the future for the establishment of new Marine Protected Areas.

The crayfish plague pathogenAphanomyces astaciis one of the main factors responsible for the decline in European and Asian native crayfish species. This pathogen was transported to these regions through its natural carriers, North American crayfish species, which were introduced during the last century. Since then, the carrier species and the pathogen have spread worldwide due to globalization and the highly invasive nature of these species. In Europe, five carrier species have been categorized as high-risk as they are responsible for the loss of provisioning services, which endangers freshwater ecosystems. The red swamp crayfishProcambarus clarkii, in particular, is currently one of the most concerning species as its spread threatens crayfish biodiversity and freshwater ecosystems worldwide. In this study, we describe the first detection ofA. astaciin an introduced population ofP. clarkiiin Central America, specifically in Costa Rica. Using molecular approaches, we analyzed 48 crayfish samples collected from Reservoir Cachí and detected the presence ofA. astaciin four of these samples. The introduction ofP. clarkiiand the incorrect management of the species (related to its fishery and the commercialization of live specimens) over the past decades in Europe are mistakes that should not be repeated elsewhere. The detection of the pathogen is a warning sign about the dangerous impact that the introduction of this invasive crayfish may have, not only as a carrier of an emerging disease but also as a direct risk to the invaded ecosystems. Our results may serve to (1) assess current and future consequences, and (2) direct future research activities, such as determining the potential impacts ofA. astacion native decapod species, or on other introduced crayfish species that are used for aquaculture purposes, such asCherax quadricarinatus.

Studies of the bycatch associated to the shrimp trawling fishery in the Pacific coast of Costa Rica do not assess small organisms (< 10 cm TL) and non-dominant species (< 0.1% of total catch). There is a void in assessing the maintenance of the ecology and ecosystem on which the fishery depends. Furthermore, the Constitutional Court of Costa Rica prohibited the renewal of existing and the issuing of new shrimp bottom-trawl licenses, indicating the necessity of more scientific information on the impacts of this fishery. We present the results of a 23-month study of the shrimp bottom-trawl fishery performed between 50 and 350 m deep in the Pacific coast of Costa Rica. A total of 109 hermit crabs were collected (six species and two families). Paguristes cf. holmesi was the most common species. Zone II presented the highest species richness and abundance. Most specimens (81.8 %) were caught in shallower waters (50-149 m). More than 45% of the trawls presented hermit crabs. It is imperative to further assess the trawling effects on non-commercial benthic fauna and changes on predator-prey relationships before issuing new shrimp licenses

Background Acanthurus guttatus is distributed from the Maldives to the Hawaiian Archipelago and the Pitcairn Islands, and as north as Ryukyu Islands and as south as New Caledonia. The only known locality in the Eastern Tropical Pacific is Clipperton Atoll where three vagrant specimens have been observed. Methods On June 2016 and April 2017 small groups of A. guttatus were observed and photographed during SCUBA diving and snorkeling surveys for touristic suitability at Isla del Coco National Park, Costa Rica. Results Six specimens of A. guttatus were observed swimming over shallow rocky reefs at Isla del Coco, a volcanic island located in the Eastern Tropical Pacific. Conclusions This study represents the first record of A. guttatus at Isla del Coco, the second known location of occurrence in the Eastern Tropical Pacific, and the easternmost known range for the Whitespotted surgeonfish.

Isla del Coco (Costa Rica) forms part of the five oceanic islands of the Eastern Tropical Pacific and is well known for its high biodiversity and great endemism. While several marine biological and oceanographical surveys have been conducted around the island over the past 35 years, an integrated, systematic view of the shallow water system is lacking as is an assessment of the impact of illegal fisheries. The aim of the study was thus to identify the main biological compartments of the Isla del Coco system and to quantify its energy flow structure through the development of a trophic model for the shallow water environments (≤30 m). With the software Ecopath with Ecosim, and based on the model structure previously used for Darwin and Wolf islets in the Galápagos Archipelago, a trophic model was developed using information from several field surveys and additional data from similar systems. The total biomass of the Isla del Coco system (1,972.25 t km−2) was mainly comprised of high trophic level species such as hammerhead shark, pelagic predatory fish and other sharks. The reef ecosystem is in a healthy (relatively undisturbed) state and dominated by large apex predators and mesopredators. Of the keystone groups identified (toothed cetaceans, tiger sharks, other sharks, benthic omnivorous fish and pelagic predatory fish), toothed cetaceans and tiger sharks were identified as having the strongest influence on the structure and diversity of the community through direct and indirect interactions. The Isla del Coco ecosystem presents a higher biomass than a similar system in the Galápagos archipelago, likely due to lower fishing pressure and higher system maturity. UCR::Vicerrectoría de Investigación::Unidades de Investigación::Ciencias Básicas::Centro de Investigación en Ciencias del Mar y Limnología (CIMAR) UCR::Vicerrectoría de Docencia::Ciencias Básicas::Facultad de Ciencias::Escuela de Biología

Euphausiids have been well studied in several regions of the Pacific Ocean; however, there is less information regarding euphausiids in Costa Rican waters. We analyzed euphausiid specimens collected around Isla del Coco National Park during 2011 and 2012. A total of 130 specimens were analyzed and 13 euphausiid species were identified, belonging to four genera and one family. An annotated list of species is presented, with photographs and details for their identification. All species found represent new records for waters around Isla del Coco in the Costa Rican Pacific. The most frequent species were Euphausia diomedeae, Euphausia distinguenda, Nematoscelis gracilis and Stylocheiron affine. Los eufáusidos han sido ampliamente estudiados en el Océano Pacífico, sin embargo existe poca información respecto a los eufáusidos que habitan aguas costarricenses. Analizamos 130 especímenes de eufáusidos provenientes de muestras de zooplancton recolectadas alrededor de la Isla del Coco del 2011 y 2012. Identificamos 13 especies pertenecientes a cuatro géneros y una familia. Se presenta un listado de especies y fotografías con detalles que facilitan su identificación. Todas las especies encontradas representan nuevos informes para aguas de la Isla del Coco en el Pacífico costarricense. Las especies más frecuentes fueron Euphausia distinguenda, Nematoscelis gracilis, Euphausia diomedeae y Stylocheiron affine. Consejo Nacional de Rectores/[]/CONARE/Costa Rica Universidad de Costa Rica/[808-B0-654]/UCR/Costa Rica Universidad de Costa Rica/[808-B0-060]/UCR/Costa Rica UCR::Vicerrectoría de Investigación::Unidades de Investigación::Ciencias Básicas::Centro de Investigación en Ciencias del Mar y Limnología (CIMAR) UCR::Vicerrectoría de Docencia::Ciencias Básicas::Facultad de Ciencias::Escuela de Biología

The Galapagos Slipper lobster, Scyllarides astori, has been reported from rocky reefs along the Eastern Tropical Pacific: the Gulf of California, the Galapagos Archipelago and mainland Ecuador. Although larval stage S. astori has been found in other localities throughout this range, there are no records of adults inhabiting waters between these three locations. Here we present the first record of an adult S. astori from Isla del Coco and Costa Rican Pacific waters. The single specimen, a male, was hand-collected within a coral reef in Pajara islet. This finding increases the reported lobster species richness of Costa Rican Pacific waters to six species and expands the adult geographic range of S. astori to Isla del Coco.