Abstract
The feeding activity of three herbivorous fishes (Sparisoma viride, Scarus iserti and Acanthurus coeruleus) and its impact on two coral reefs were studied during the dry (February) and rainy (August) seasons of 2006 in Cuba. One of the reef stations is at the "Acuario" dive point in the Guanahacabibes National Park, and is relatively pristine. The second one is located at the north coast of Havana City facing the Instituto de Oceanología (IdO) and is subject to pollution and fishing pressures. Herbivore fish composition was analized, and foraging intensity was measured for all Acanthurid and Scarid species, by counting fish bites in 1 m2 during five minute intervals (25 replicates). Concurrently, species foraging intensity was measured for juvenile, intermediate, and adult phases, counting fish bites during 10 minutes intervals (10 replicates). Algal consumption rate was estimated using a coefficent of consumed biomass per bite, for each size class. The algal cover was sampled at 20 m linear transects with four replicates at each site. Food items were assessed sampling algae at the observed bitten substrates. Compared to Acuario, herbivores in IdO showed lower species richness and higher density of small size fishes, but large-sized parrotfish was almost absent due to intense fishing. The highest bite rate was observed for the smallest fish size, but net consumption rate was three times greater for medium and great size fishes, which were more abundant in the protected area. Algal cover was lower in Acuario, while in IdO it was very high, and coral cover was very low. In both locations epiphytic algae were the preferred food. These results support generalizations referring to the importance of great size herbivores fishes in controlling excesive algal proliferation on coral reefs.
Highlights
Algunos arrecifes del Caribe han sufrido un cambio de fase, de un estado dominado por corales a otro en que predominan las algas carnosas (Pandolfi et al 2005)
Este trabajo tiene como objetivos caracterizar la actividad de búsqeuda de alimento de los peces herbívoros en dos arrecifes frontales con diferente grado de antropización y evaluar su influencia sobre la salud del arrecife, cuantificar la cobertura de algas en las dos localidades y su relación con la actividad alimentaria de los peces herbívoros, así como contribuir al conocimiento de la alimentación de tres de las especies más abundantes en Cuba y el Caribe
En Instituto de oceanología (IdO), predominaron S. iserti, ejemplares pequeños de S. viride, y en general muy baja densidad de herbívoros mayores de 15 cm, mientras que en Acuario se observó una densidad similar de peces de las tres clases de tallas (Cuadro 3)
Summary
Los muestreos se realizaron en dos arrecifes frontales fisiográficamente muy parecidos pero con muy diferente nivel de influencia antrópica. La intensidad de forrajeo y la densidad de los peces de las familias Scaridae y Acanthuridae se evaluaron mediante observación directa, utilizando el método descrito por Steneck (1983), que consiste en registrar la especie, talla estimada y número de mordiscos que realizan los peces herbívoros sobre un 1 m2 del sustrato durante 5 minutos, con un total de 25 réplicas en cada estación. Se tomaron cinco muestras por cada clase de talla de cada una de las tres especies, en las dos localidades y épocas de muestreo. No se observaron diferencias en la composición por tallas de las especies más abundantes, entre las dos épocas del año en cada estación (Cuadro 1).
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