Influence of a shipwreck on a nearshore-reef fish assemblages off the coast of Rio de Janeiro, Brazil

Lat. Am. J. Aquat. Res., 39(1): 103-116,Influence 2011 of a shipwreck on the associated fish assemblages, Brazil DOI: 10.3856/vol39-issue1-fulltext-10 103 Research Article Influence of a shipwreck on a nearshore-reef fish assemblages off the coast of Rio de Janeiro, Brazil Eduardo Barros Fagundes-Netto1,2, Luiz Ricardo Gaelzer¹, Ricardo Coutinho1,2 & Ilana R. Zalmon2 1 Instituto de Estudos do Mar Almirante Paulo Moreira, Departamento de Oceanografia Rua Kioto 253, 28930-000, Arraial do Cabo, RJ, Brazil 2 Universidade Estadual do Norte Fluminense, Av. Alberto Lamego 2000, 28013-602 Campos dos Goytacazes, RJ, Brazil ABSTRACT. The effect of the Orion shipwreck on fish assemblage distribution near the reef was studied to the northeast of Rio de Janeiro with six different fishing gears: gillnets, mid-water longlines, circular traps, rectangular traps, vertical longlines, and bottom trawling. The study consisted of a pre-monitoring survey four months before the shipwreck in the area (A) and in two control areas (B and C). After 36 months, a total of 56 species were caught in the Orion reef area, 49 in control area B and 59 in control area C. The similarity analysis, considering the number of fish caught during the nine surveys in the three study areas, clustered the pre-monitoring and first post-settlement surveys of the three sites. This occurred due to the low number of fish captured and the dominance of Trichiurus lepturus and Lagocephalus laevigatus. These results differed from all the other studies in the three areas due to the co-dominance of Ctenosciaena gracilicirrhus and Stephanolepis hispidus. Such spatial similarity shows the low influence of the Orion reef in the area after three years. Biomass values were 15% higher in the Orion reef area than in the control areas, representing an increase of up to 1.2 times in wet weight. The increment of fish communities is still insufficient for proposing sustainable fishery activity in the shipwreck area. The monitoring time (32 months) after the sinking of the Orion may be considered too short to assure that the wreckage had reached its maturity as an artificial reef, either as a fish attractor or producer. Keywords: shipwreck, artificial reef, monitoring, management, fish assemblage, southern Brazil. Influencia de un buque sumergido sobre agregaciones de peces asociados a un arrecife somero de la costa nordeste de Rio de Janeiro, Brasil RESUMEN. El efecto del buque sumergido Orión sobre la distribución de las comunidades de peces próximas al arrecife fue estudiado en el noreste de Rio de Janeiro utilizándose seis artes de pesca: red de enmalle, palangre pelágico, trampas circulares, trampas rectangulares, palangres y red de arrastre de fondo. El estudio consistió en una investigación premonitoreo, cuatro meses antes del naufragio en el área (A) y en dos áreas control (B y C). Después de 36 meses, 56 especies fueron capturadas en el arrecife Orión, 49 en el área control B y 59 en el control C. Los análisis de similitud considerando el número de peces capturados durante las nueve campañas en las tres áreas de estudio, agruparon las campañas de premonitoreo y la primera de posasentamiento, en las tres localidades, debido a la baja captura de individuos y a la dominancia de Trichiurus lepturus y Lagocephalus laevigatus. Estos resultados fueron distintos en todas las otras investigaciones en las tres localidades, debido a la codominancia de Ctenosciaena gracilicirrhus y Stephanolepis hispidus. Esta similitud espacial muestra la baja influencia del arrecife Orión en el área después de tres años. Los valores de biomasa fueron 15% mayores en la área del arrecife Orión que en las áreas control, representando un aumento de hasta 1,2 veces en peso húmedo. El aumento de las comunidades de peces en el área es todavía insuficiente para proponer la actividad pesquera sustentable en la región del naufragio. El periodo de monitoreo (32 meses), despues del asentamiento del Orión, puede ser considerado corto para asegurar que el naufragio, tenga legado a su madurez como arrecife artificial, como atractivo o productor de peces. Palabras clave: naufragio, arrecife artificial, monitoreo, manejo, comunidad de peces, sur de Brasil. ___________________ Corresponding author: Eduardo Fagundes-Netto () 104 Lat. Am. J. Aquat. Res. INTRODUCTION MATERIALS AND METHODS The use of decommissioned marine ships as artificial reefs for fisheries or conservation is a common practice in many coastal countries (Jensen et al., 2000; Love et al., 2006) and increased fishing yield can be obtained almost immediately after the installation of artificial structures (Seaman & Jensen, 2000). Despite of the increased use as artificial reefs, studies comparing fish assemblages on shipwrecks and natural reefs are still scarce (Arena et al., 2007). According to Rilov & Benayahu (2000), one should take into consideration that complex vertical artificial structures do not necessarily imitate the natural environment, but can establish their own community, which is influenced by the spatial orientation and complexity of the structure. Abandoned ships have been settled since 1935 (Stone, 1985) to promote the success of tourism and commercial fishing (Seaman & Jensen, 2000). Walker et al. (2007) pointed out that artificial reefs including shipwrecks are characterized by different ecological interactions. Epibenthic communities provide food resources for consumers and act as a secondary habitat for other benthic invertebrates, increasing the complexity of the habitat including shelter for fish (Moura et al., 2007; Nicoletti et al., 2007). Wreckage of ships, accidentally or planned, are known among fishers as abundant areas for fish species which live there, or ground for feeding and spawning activities (Supongpan, 2004). The latter aspect has led over the last decade to a refinement of the historical view of reefs as simple attractors (Seaman & Jensen, 2000). The biodiversity and great biomass of fish and invertebrates in deliberate sinking ships, and the replacement of less selective fishing practices to more conservative gears in these habitats have highlighted the potential for the controlled use of the seafloor (Silva, 2001). Given the shortage of new opportunities for fishery resources in coastal areas of Rio de Janeiro state, the Brazilian oil and gas company (Petrobras) and the Brazilian Navy established an artificial reef project based on the decommissioning of the hydrographic ship Orion, expecting to create potential habitats for different marine species. This study aimed to evaluate the influence of the Orion shipwreck on the composition and structure of the associated fish assemblages on the northeast coast of Rio de Janeiro, assuming that it enhances fish assemblage’s densities and biomass contributing for the artisanal fishing yield. Study area The shallow platform in the northeast region of Rio de Janeiro is characterized mainly by sandy and muddy subst (...truncated)