Atherinella blackburni (Schultz, 1949) at Itamambuca Beach, Ubatuba, SP: ecological characterization and distribution on the Brazilian coast (Teleostei: Atheriniformes: Atherinopsidae) Mattox, GMT.a*, Gondolo, GF.b and Cunningham, PTM.b aDepartamento de Zoologia, Instituto de Biociências, Universidade de São Paulo – USP, CP 11461, CEP 05422-970, São Paulo, SP, Brazil bDepartamento de Oceanografia Biológica, Instituto Oceanográfico, Universidade de São Paulo – USP, Praça do Oceanográfico, 191, Cidade Universitária, CEP 05508-900, São Paulo, SP, Brazil *e-mail: [email protected] Received July 7, 2006 – Accepted February 27, 2007 – Distributed May 31, 2008 (With 7 figures) Abstract Atherinella blackburni is a silverside species whose occurrence on the Brazilian coast was not properly registered until recently. So far, records of its distribution along the Brazilian shore were limited to Itaparica Island, Bahia State, and Porto Inhaúma, Rio de Janeiro State. In a recent survey of the ichthyofauna of Itamambuca Beach, Ubatuba, São Paulo State, 100 specimens of this species were collected, yielding a considerable source of information regarding its ecol- ogy and a new southern limit of its distribution. A detailed survey of an ichthyological collection revealed lots of this species from regions of the Brazilian Northeast, resulting in a northward expansion of the occurrence of A. blackburni in Brazilian waters. Besides the populations found on the Brazilian coast, the species also occurs discontinuously in the Atlantic coasts of Costa Rica, Panama and Venezuela. Meristic and morphometric analysis showed overlapped values between Brazilian populations and the ones closer to the Caribbean. An ecological study of A. blackburni at Itamambuca Beach revealed that it is a predominantly diurnal species with preference for warm and salty waters, often occurring in sandy-bottom environments. It was more abundant in Summer and Winter, when individuals with smaller values of length and weight also occurred. Keywords: ecology, marine fish, new occurrence, silverside, West Atlantic. Atherinella blackburni (Schultz, 1949) na praia de Itamambuca, Ubatuba, SP: caracterização ecológica e distribuição na costa brasileira (Teleostei: Atheriniformes: Atherinopsidae) Resumo Atherinella blackburni é uma espécie de peixe-rei cuja ocorrência na costa brasileira não havia sido precisamente registrada até recentemente. Ainda assim, sua distribuição no litoral brasileiro estava restrita à Ilha de Itaparica, Bahia e Porto Inhaúma, Rio de Janeiro. Em um recente levantamento da ictiofauna da Praia de Itamambuca, Ubatuba, São Paulo, foram coletados 100 espécimes desta espécie, originando uma fonte considerável de informações no tocante à sua ecologia e a um novo limite sul de sua distribuição. Um estudo detalhado revelou lotes desta espécie em regiões do nordeste brasileiro em coleção ictiológica, resultando na expansão para o norte da ocorrência de A. blackburni em águas brasileiras. Além das populações encontradas na costa brasileira, a espécie também ocorre descontinuamente na costa Atlântica da Costa Rica, Panamá e Venezuela. Análise merística e morfométrica revelou valores sobrepostos entre populações brasileiras e aquelas mais próximas ao Caribe. O estudo ecológico de A. blackburni na Praia de Itamambuca evidenciou que é uma espécie predominantemente diurna com preferência por águas quentes e salgadas, freqüente em ambientes com fundo arenoso. Foi mais abundante no verão e inverno, quando indivíduos com menores valores de comprimento e peso também ocorreram. Palavras-chave: Atlântico ocidental, ecologia, nova ocorrência, peixe marinho, peixe-rei. 1. Introduction Knowledge of Brazilian marine fishes is not as in- Figueiredo and Menezes (1978) stated that the taxon- complete as the one of Neotropical freshwater fishes, omy of South American silversides had not been ade- but much is yet to be done regarding the marine fish quately studied and despite of some studies dealing with fauna on the Brazilian coast (Menezes et al., 2003). the taxonomy of higher level taxa in the last 20 years Braz. J. Biol., 68(2): 307-313, 2008 307 Mattox, GMT., Gondolo, GF. and Cunningham, PTM. (Chernoff, 1986; Dyer and Chernoff, 1996; Dyer, 2006), Brasileiro do Meio Ambiente e dos Recursos Naturais there are still questions to be pursued at the species level Renováveis), August 15, 2003. (e.g. Malabarba and Dyer, 2002). The silverside species Five points were selected along the beach (Figure 1) Atherinella blackburni (Schultz, 1949) well illustrates and each one was sampled three times in a 50 meter this issue. long transect with a beach-seine measuring 9 x 1.5 m, Atherinella blackburni was originally described in 5 mm of internode distance in the central 3 m-mesh and the genus Coleotropis based on seven specimens col- 15 mm in the two lateral 3 m-mesh. For standardization lected in 1925 in the Gulf of Venezuela (Schultz, 1949). purposes collections were made monthly, in full moon Additional collections expanded its area of occurrence, periods, at morning and night. Total length (Lt, mm) which has a discontinuous distribution between the and total weight (Wt, g) was taken from each individual, Caribbean coast of Costa Rica and Porto Inhaúma, Brazil and then the fishes were fixed in formalin 4%, stored in (Gilbert and Caldwell, 1967; Chernoff, 1986; Cervigón, ethanol 70% and deposited in the ichthyological collec- 1991; Aguilera, 1998). The austral limit of the species tion of Museu de Zoologia da Universidade de São Paulo distribution was registered as the Brazilian Central Coast (MZUSP). The identification was made based on the (Gilbert and Caldwell, 1967), but the exact location of works of Schultz (1949), Gilbert and Caldwell (1967) Porto Inhaúma was not explicit. According to J. Williams and Lopes and Oliveira-Silva (2001). (pers. comm.), the complete locality of the specimen The ecological study included all specimens collect- from Porto Inhaúma is “Bay of Rio, Porto da Inhaúma, ed at Itamambuca Beach (n = 100). Additional material Brazil” (22° 52’ 19” S and 43° 16’ 50” W). was obtained from Enseada Beach (23° 26’ 13’’ S and Occurrence of Atherinella blackburni on the 45° 04’ 08’’ W), Ubatuba, São Paulo, in April 2005. For Brazilian shore was poorly documented to date. Besides the meristic and morphometric analysis, 69 specimens the single specimen from Porto Inhaúma (Gilbert and from Itamambuca Beach were used, 9 from Enseada Caldwell, 1967), only Lopes and Oliveira-Silva (2001) Beach and 19 from the Brazilian Northeast previously registered its occurrence in Brazilian waters, at Itaparica deposited in MZUSP (n = 97). Island, Bahia State (13° 07’’ S and 38° 45’’ W), based on The ecological analysis included relative frequency 29 specimens. These authors briefly discussed their mer- of numerical abundance and the population structure istic and morphometric data in relation to values from was based on the average Lt and Wt at the five collec- Venezuelan populations given by Gilbert and Caldwell tion points, in mornings and nights, along the year. Lt (1967) and attributed the differences found to intra-spe- and Wt were taken with an ichthyometer and a digital cific variation. scale of 0.01 g precision, respectively. Temperature and Despite the high collection effort in many ar- salinity were taken with a thermometer and a refractom- eas of the Brazilian shore, Atherinella blackburni was eter, respectively. Counts and measures followed Schultz never among registered species along the coast (e.g., (1949), Gilbert and Caldwell (1967) and Lopes and Figueiredo and Menezes, 1978; Giannini and Paiva Oliveira-Silva (2001). Measures were taken on the left Filho, 1995; Pessanha et al., 2000; Camargo and Isaac, side of the body, whenever possible, with a digital cali- 2001; Pessanha and Araújo, 2003; Pessanha et al., per of 0.01 mm precision. Simple statistical descriptors 2003). Another two species of Atherinopsidae are fre- were obtained for each meristic and morphometric char- quently registered in the Brazilian coast: Odontesthes acter (i.e., range, average and standard deviation) which bonariensis and Atherinella brasiliensis, the latter being were tabled (Table 1) in comparison with data from pre- the only congener of A. blackburni known in Brazilian vious works dealing with this species (Schultz, 1949; waters (Chernoff, 1986; Dyer, 2003). Gilbert and Caldwell, 1967; Lopes and Oliveira-Silva, Several specimens of Atherinella blackburni were 2001). collected in a recent survey of the ichthyofauna of Itamambuca Beach, Ubatuba, São Paulo State (23° 24’ S 3. Results and 45° 00’ W). This study aims to update the data re- garding distribution of A. blackburni on the Brazilian 3.1. Atherinella blackburni (Schultz, 1949) (Figure 2) coast, to compare meristic and morphometric data of Coleotropis blackburni Schultz, 1949 [original specimens collected in Brazil with ones from other lo- s description, type-locality: Jacuque Point, Gulf calities, to present characters diagnosing A. blackburni, of Venezuela, Venezuela]; Gilbert and Caldwell, and to contribute to the knowledge of its ecology at Itamambuca Beach through a study of its spatial and 1967 [description and comparison with C. starski, temporal (diel and seasonal) repartition. occurrence in Costa Rica]; s Coleotropis colecanos Caldwell, 1962 [original description, type-locality: Tortuguero, Costa 2. Material and Methods Rica]; and A list of all material examined is attached. The ma- s Atherinella blackburni (Schultz, 1949) – Chernoff jority of