Ecology and management of the invasive lionfish Pterois volitans/miles complex (Perciformes: Scorpaenidae) in Southern Costa Rica.

Invasive species alter ecosystem integrity and functioning and are considered one of the major threats to biodiversity on a global scale. The indopacific lionfish (Plerois volitans [Linnaeus, 1758] / miles [Bennet, 1882] complex) is the first non-native marine fish that has established itself in the Western Atlantic. It was first reported in Florida in the 1980s and then spread across the entire Caribbean in subsequent years. In Costa Rica, lionfish were first sighted by the end of 2008 and are now present in all South Caribbean reefs. Lionfish are a major problem for local fisherman by displacing native fish species. The aim of this study was to determine population density, size and diet of lionfish populations at four study sites along the Southern Caribbean coast of Costa Rica. Two of the sites were located inside the National Park Cahuita where regular lionfish removal occurs, whereas the other two study sides do not experiment this kind of management. Total length and wet weight of >450 lionfish individuals were determined between March and June 2011. Three relative metrics of prey quantity (percent number, percent frequency, and percent weight) were compared from approximately 300 lionfish caught with the polespear in shallow waters (<7 m depth). Population density was assessed weekly through visual transect surveys. Our results showed that lionfish preyed mostly upon teleosts and crustaceans. Teleosts dominated lionfish diet in percent frequency (71%) and percent weight (85%), whereas crustaceans had the highest percent number (58%). The top five teleost families of dietary importance were Pomacentridae, Acanthuridae, Blennidae, Labridae and Serranidae. The average total length (+/- SD) of lionfish was 18.7 (+/- 5.7)cm and varied significantly between sites (p<0.001). Mean density of lionfish was 92fish/ha with no significant differences between sites. Smallest fish and lowest densities were found at the two sites inside the National Park Cahuita. Despite management efforts on a regional scale, nationwide efforts are ineffective and lionfish control activities are poorly implemented. We conclude that there is an urgent need to develop an improved institutional framework for local lionfish control that promotes effective coordination among the relevant stakeholders in order to deal with invasive lionfish in Costa Rica.

Nitrogen Fuelling of the Pelagic Food Web of the Tropical Atlantic.

We estimated the relative contribution of atmosphere (ic Nitrogen (N) input (wet and dry deposition and N fixation) to the epipelagic food web by measuring N isotopes of different functional groups of epipelagic zooplankton along 23°W (17°N-4°S) and 18°N (20-24°W) in the Eastern Tropical Atlantic. Results were related to water column observations of nutrient distribution and vertical diffusive flux as well as colony abundance of Trichodesmium obtained with an Underwater Vision Profiler (UVP5). The thickness and depth of the nitracline and phosphocline proved to be significant predictors of zooplankton stable N isotope values. Atmospheric N input was highest (61% of total N) in the strongly stratified and oligotrophic region between 3 and 7°N, which featured very high depth-integrated Trichodesmium abundance (up to 9.4×10(4) colonies m(-2)), strong thermohaline stratification and low zooplankton δ15N (~2‰). Relative atmospheric N input was lowest south of the equatorial upwelling between 3 and 5°S (27%). Values in the Guinea Dome region and north of Cape Verde ranged between 45 and 50%, respectively. The microstructure-derived estimate of the vertical diffusive N flux in the equatorial region was about one order of magnitude higher than in any other area (approximately 8 mmol m(-2) d(1)). At the same time, this region received considerable atmospheric N input (35% of total). In general, zooplankton δ15N and Trichodesmium abundance were closely correlated, indicating that N fixation is the major source of atmospheric N input. Although Trichodesmium is not the only N fixing organism, its abundance can be used with high confidence to estimate the relative atmospheric N input in the tropical Atlantic (r2 = 0.95). Estimates of absolute N fixation rates are two- to tenfold higher than incubation-derived rates reported for the same regions. Our approach integrates over large spatial and temporal scales and also quantifies fixed N released as dissolved inorganic and organic N. In a global analysis, it may thus help to close the gap in oceanic N budgets.

Ecology and management of the invasive lionfish Pterois volitans/miles complex (Perciformes: Scorpaenidae) in Southern Costa Rica / Ecología y manejo del pez león Pterois volitans/miles complex (Perciformes: Scorpanidae) en el Caribe sur de Costa Rica

Invasive species alter ecosystem integrity and functioning and are considered one of the major threats to biodiversity on a global scale. The indopacific lionfish (Pterois volitans [Linnaeus, 1758] / miles [Bennet, 1882] complex) is the first non-native marine fish that has established itself in the Western Atlantic. It was first reported in Florida in the 1980s and then spread across the entire Caribbean in subsequent years. In Costa Rica, lionfish were first sighted by the end of 2008 and are now present in all South Caribbean reefs. Lionfish are a major problem for local fisherman by displacing native fish species. The aim of this study was to determine population density, size and diet of lionfish populations at four study sites along the Southern Caribbean coast of Costa Rica. Two of the sites were located inside the National Park Cahuita where regular lionfish removal occurs, whereas the other two study sides do not experiment this kind of management. Total length and wet weight of >450 lionfish individuals were determined between March and June 2011. Three relative metrics of prey quantity (percent number, percent frequency, and percent weight) were compared from ~300 lionfish caught with the polespear in shallow waters (<7m depth). Population density was assessed weekly through visual transect surveys. Our results showed that lionfish preyed mostly upon teleosts and crustaceans. Teleosts dominated lionfish diet in percent frequency (71%) and percent weight (85%), whereas crustaceans had the highest percent number (58%). The top five teleost families of dietary importance were Pomacentridae, Acanthuridae, Blennidae, Labridae and Serranidae. The average total length (±SD) of lionfish was 18.7(±5.7)cm and varied significantly between sites (p<0.001). Mean density of lionfish was 92fish/ha with no significant differences between sites. Smallest fish and lowest densities were found at the two sites inside the National Park Cahuita. Despite management efforts on a regional scale, nationwide efforts are ineffective and lionfish control activities are poorly implemented. We conclude that there is an urgent need to develop an improved institutional framework for local lionfish control that promotes effective coordination among the relevant stakeholders in order to deal with invasive lionfish in Costa Rica.

Las especies invasoras alteran la integridad y el funcionamiento de los ecosistemas y se consideran una de las mayores amenazas para la biodiversidad a nivel global. El pez león (Pterois volitans [Linnaeus, 1758]/ miles [Bennet, 1882] complex) del Indo-Pacífico es el primer pez marino no-nativo que se ha establecido en el Atlántico oeste. Fue reportado por primera vez en Florida en los años 80´s y se propagó en todo el Caribe en los años subsiguientes. En Costa Rica, el pez león se reporto por primera vez a finales del 2008 y hoy en día se encuentra en todos los arrecifes del Caribe Sur. El pez león es un grave problema para los pescadores locales por desplazar a los recursos pesqueros nativos. El objetivo de este estudio fue determinar la densidad poblacional, talla y la dieta de las poblaciones del pez león en cuatro sitios de muestreo a lo largo de la costa del Caribe Sur de Costa Rica. Dos de los sitios fueron localizados dentro del Parque Nacional Cahuita donde se efectúan remociones periódicos del pez león, mientras que los otros dos sitios no experimenten este tipo de manejo. Se midieron la longitud total y el peso fresco de >450 individuos entre marzo y junio 2011. Se compararon tres medidas relativas para el análisis estomacal (composición por número, por frecuencia y por peso) de ~300 individuos capturados con un arpón marino en las aguas someras (<7m profundidad). La densidad poblacional fue estimada a partir de transectos visuales semanales. Nuestros resultados muestran que el pez león se alimentó principalmente de teleósteos y crustáceos. Los teleósteos dominaron la dieta en cuanto a composición por frecuencia (71%) y composición por peso (85%), mientras que los crustáceos prevalecieron en cuanto a composición por número (58%). Las cinco familias más importantes en la dieta del pez león fueron los Pomacentridae, Acanthuridae, Blennidae, Labridae y Serranidae. La longitud total media (±DE) fue 18.7(±5.7)cm y varió significativamente entre los sitios (p<0.001). La densidad media fue de 92 peces/ha y no fue estadísticamente diferente entre los sitios. Los peces con la menor talla y las densidades poblacionales más bajas fueron encontrados en los dos sitios dentro del Parque Nacional Cahuita. A pesar de los esfuerzos de manejo que existen a nivel regional, las estrategias nacionales son deficientes y las actividades para el control de la especie invasiva son escasos en Costa Rica. Es preciso desarrollar un marco institucional para el control local del pez león que incluye todo los implicados y que promueva la coordinación efectiva entre ellos.