Journal of Fish Biology (2011) 78, 344–354 doi:10.1111/j.1095-8649.2010.02851.x, available online at wileyonlinelibrary.com Influence of moon phase on fish assemblages in estuarine mangrove tidal creeks J. A. A. Ramos*†, M. Barletta*†‡, D. V. Dantas*†, A. R. A. Lima*† and M. F. Costa*† *Laborat´ orio de Ecologia e Gerenciamento de Ecossistemas Costeiros e Estuarinos, Dpt Oceanografia, UFPE, Cidade Universit´ aria, 50740-550 Recife, Pernambuco, Brazil and †Instituto de Ecologia de Gerenciamento de Ecossistemas Costeiros e Estuarinos (IEGEA), P. O. Box 8132, Recife, Pernambuco, CEP 51020-970, Brazil (Received 11 June 2010, Accepted 14 October 2010) Significant differences in the composition of fish assemblages during different moon phases were detected in mangrove tidal creeks of the Goiana Estuary. The numbers of Zabaleta anchovy Anchovia clupeoides, Tarpon snook Centropomus pectinatus and Guavina Guavina guavina as well as at least 15 other species showed significant changes according to moon phase and were higher in terms of individuals (32%) and mass (34%) during the new moon.  2011 The Authors Journal of Fish Biology  2011 The Fisheries Society of the British Isles Key words: estuarine fishes; lunar cycle; north-east Brazil; tropical estuary. Mangrove forests are ecosystems with high biological productivity and diversity, which provide protection, food and nursery grounds for many resident and migra- tory invertebrate and fish species (Barletta et al., 2000, 2003, 2010; Barletta-Bergan et al., 2002a, b; Sheridan & Hays, 2003; Krumme et al., 2005). Many of these species are of social and commercial importance, which represents a strong argu- ment for the conservation of the mangrove areas (Griffin, 1985; Lenaton & Potter, 1987; Barletta et al., 1998). Estuaries are naturally fluctuating environments where tide, temperature, salinity and dissolved oxygen change daily and annually (Kjerfve, 1990; Barletta et al., 2005). In most mangroves, there are intertidal creeks which drain the flooded forest according to the tidal regime. These creeks are used and explored by larvae, juvenile and adult fishes and crustaceans. Most come back to the main channel of the estuary and adjacent coastal region during low tide (Vance et al., 1996; R¨ onnb¨ ack et al., 1999; Barletta et al., 2003). A few stay in this habitat during low tide, as a strategy to minimize the effects of low water levels and exposure to predators (Barletta et al., 2000). Studies reporting the composition of fish assemblages in mangrove areas in differ- ent parts of the tropical world such as Tulear Lagoon, Madagascar (Laroche et al., ‡Author to whom correspondence should be addressed. Tel.: +55 81 2126 8225; email: mario.barletta@ pq.cnpq.br 344  2011 The Authors Journal of Fish Biology  2011 The Fisheries Society of the British Isles