The recent invasion of lionfish (Pterois volitans) in the Atlantic is considered a new threat to benthic and fish communities in the Caribbean region. This species was first reported in Venezuela in 2009 at various sites. Increasing reports in the past five years suggest lionfish has expanded its range of distribution and habitats. Nevertheless, this information is mostly anecdotal and extensive surveys aimed to determine its abundance, size structure and other ecological aspects encompassing wider spatial scales are necessary to understand the actual role of this species on sub-tidal marine communities in Venezuela. We determined its density and population size structure through visual census along the Venezuelan coast. Visual censuses were made following strip transects at a depth between 5 and 20m and in daylight time, at 19 sites in five localities. Average density ranged between 7 to 55 individuals per hectare among sites. Most individuals were adults and most were found in caves, coexisting with other lionfish or with different species, while others were actively preying. The fish Pterois volitans seems to be well-established along the Venezuelan coast in densities that in some sites appear to be higher than in their Pacific native range but lower than in some invaded localities of the Atlantic.
Key words: Exotic species, visual census, South Caribbean, Pterois volitans.
Resumen
La reciente invasión del pez león (Pterois volitans) en el Atlántico se considera una nueva amenaza para bentónicos y peces de las comunidades en la región del Caribe. Esta especie fue informada por primera vez en varios sitios de Venezuela en 2009. El aumento de informes en los últimos cinco años sugiere que ha ampliado su distribución y hábitats. Sin embargo, esta información es principalmente anecdótica por lo que son necesarios estudios dirigidos a determinar su abundancia, estructura de tallas y otros aspectos ecológicos que abarquen más escalas espaciales para entender el papel real de esta especie en comunidades marinas en Venezuela. Determinamos la densidad y estructura del tamaño poblacional del pez león a través de censos visuales en la costa venezolana. Realizamos censos visuales siguiendo transectos lineales a una profundidad entre 5 y 20m durante el día, en 19 sitios de cinco localidades. La densidad media varia entre 7 y 55 individuos por hectárea entre sitios. La mayoría de los individuos eran adultos que se encontraban en cuevas, coexistiendo con otro peces león o con diferentes especies; mientras que otros estaban forrajeando activamente. El pez Pterois volitans esta bien establecido a lo largo de la costa venezolana y sus densidades en algunos sitios parecen exceder lo informado para su distribución nativa en el Pacífico pero son densidades menores que las informadas en localidades del Atlántico.
Palabras clave: Las especies exóticas, censos visuales, volitans del Sur del Caribe, Pterois
The introduction of exotic species is considered a major threat to biodiversity because it has produced significant phase shifts in marine ecosystems worldwide (Gurevitch & Padilla, 2004; Ruiz, Carlton, Grosholz & Hines, 1997). Among exotic marine species, Pterois volitans, commonly known as lionfish, has recently received special attention. This species is native and ]]>
P. volitans has invaded from Florida to North Carolina, most of the Caribbean and the Gulf of Mexico (Schofield, 2010). Lionfish was first reported in Venezuelan in 2009, in Cape Bay in the Central Coast of Venezuela and in Morrocoy National Park. After 2010, reports increased in frequency, and it is presumed that P. volitans moved from west to east along the coast, according to a database created for divers, fishermen and scientists to report sightings the species (http://pezleon.cbm.usb.ve). Currently, P. volitans seems to be well established all along the Venezuelan coast (Lasso-Alcalá & Posada, 2010).
Pterois volitans is a voracious predator feeding from a wide range of fishes and crustaceans (Albins & Hixon, 2008). It has been suggested that the presence of this species in the Atlantic may have negative effects on reef fish communities such as significant reduction in recruitment rates (Albins & Hixon, 2008; 2011). It is also believed that the introduction of ]]>
We present a preliminary survey of ]]>
Materials and Methods
Study sites: The study was conducted at five localities and two to five sites within each locality: (1) Morrocoy National Park (five sites: Caimán, Mero, Boca Seca, Cayo Sombrero and Cayo Norte), (2) Ocumare de la Costa (five sites: Guabinas, Canal de la Ciénaga, Punta de la Ciénaga, Valle Seco and Chuao), (3) Chichirivichi de la Costa (two sites: Punta de Chichirivichi and Bahía de Chichirivichi), ]]>
Morrocoy national park is located at the western coast of Venezuela (10°51’60”N, 68°14’10”W) it is a marine protected area with major tropical marine communities (seagrass beds, mangrove forest, sandy and rocky shores and coral ]]>
Lionfish surveys: Visual censuses were made to estimate abundance of lionfish. In each site 7 to 12 belt transects (4m wide and 30m long, 120m2) were surveyed, according to reef´s size and at depth varying from 20m to 5m. This was made according to the depth in each reef which was a lot deeper in Ocumare ]]>
Statistical analysis: A two factor permutation analysis of variance (PERMANOVA), (Anderson, 2005) based on Euclidean distance was used to test the null hypothesis of no differences in lionfish density or biomass between localities (fixed factor with five levels) and across sites (nested factor within localities with 2 to five levels). All analyses were conducted using ]]>
Results
A total of 62 lionfish were found in 200 belt transects, with significant difference in density observed between localities but not across sites within each locality (
Fig. 1). Lionfish were found at all sites except in Playa Colorada and Burbujas in Mochima. Mochima was also the locality with the lowest average density (6ind/ha). Average density across sites showed a high variability ranging from 7ind/ha in Cayo Norte (locality Morrocoy), to 55ind/ha in Punta Capino (Chuspa) (Table 1).
Statistical ]]>
Fig. 2). ]]>
Fig. 3), where most individuals belong to the biggest sizes (Fig. 4).
Regarding their behavior, fifty percent of the lionfish were found hiding in caves and crevices. We also observed lionfish floating over the reef (32%) and individuals ]]>
Discussion
This study confirmed that lionfish are well-established and widely spread along the coastline of Venezuela. Densities per site range between 6ind/ha to 55ind/ha and the density for Venezuelan Coast was 25.83±66.51. Average density of lionfish for the Venezuelan Coast seems to be lower than those reported for other invaded localities in the Caribbean, like the Bahamas, but is ]]>
Chichirivichi de la Costa was one of the first localities were P. volitans/miles was reported (January ]]>
Using the CBM database we were able to hypothesize about lionfish dispersion along the Venezuelan coast. We presume it started in the west between November and December of 2009. During 2010 sightings were made in several places of the central coast. We postulate that lionfish did not reach the eastern areas of the Venezuelan coast until the middle of 2011, almost two years after the first report. This may explain why a low average density and so few ]]>
P. volitans/miles has been present since 2004 (Schofield, 2010). This also means there is the possibility of Venezuela having similar densities in the near future. Nevertheless, it has to be considered that the frequency of the reports ]]>
High variability in density of lionfish was found between sites at the same localities. Lionfish density may be influenced by factors acting locally like availability of refuges and structural complexity as it know they spend a lot of time hiding in holes and crevice (Fishelson, 1997). Sites in Ocumare de ]]>
unpublished data) but with a lot of holes and crevices where lionfish was observed specially in sites like La Cienaga, where mostly of the individuals were seeing hiding in caves. In Chichirivichi de la Costa Bay where also found high density. This site was form by group of rocks mixed with artificial structure made of concrete use by fisherman for anchoring their boats. Sites sampled in Mochima were rocky reef mostly flat with few holes and vertical structures. ]]>
The low density of lionfish of small sizes, less than 10cm. (only 6%) may be a consequence of the little power of detecting individuals specially of small sizes (Green et al., 2013). It was reported also a high underestimation of P. volitans densities especially in structural complex reef. This suggests ]]>
Pterois volitans/miles has been reported as a crepuscular species with nocturnal behavior in its native environment (Fishelson, 1997). In this study, most of the individuals ]]>
Stegastes planifrons and adults of Stegastes partitus. We observed a fishing behavior similar to those described by Côté and Maljkovic (2010) wherein lionfish remain motionless and only move to strike and eat prey passing nearby. They are also considered as solitary individuals (Fishelson, 1997), which is contrary to our observation of groups of up to seven individuals of ]]>
In conclusion, this study provides the first baseline of lionfish distribution and abundance based on wide-scale standardized surveys encompassing sites and localities along the coast of Venezuela, southern Caribbean. The results corroborate anecdotal information suggesting that the invasive species had become established invading rocky reef, coral reefs and coral communities on ]]>
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Acknowledgments
We are thankful to Cesar Herrera and Aldo Croquer for critically reviewing the manuscript and to Luis Miguel Montilla, Jose Cappeletto and Alejandra Hernandez for provide valuable help during dives and visual census. We also thank Juan Jose Cruz-Motta for his contribution in the design of the project. This ]]>
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1. Laboratorio de Ecología Experimental, Universidad Simón Bolívar, 1086, Caracas, Venezuela; estebanagudo@yahoo.com
2. Laboratorio de Sensores Remotos, Universidad Simón Bolívar, 1086, Caracas, Venezuela.
Received 01-IX-2013. Corrected 23-II-2014. Accepted 24-III-2014.