Contribution to the feeding ecology of the banded puffer fish Colomesus psittacus (Tetraodontidae) in north Brazilian mangrove creeks

ECOLOGY Contribution to the feeding ecology of the banded puffer fish Colomesus psittacus (Tetraodontidae) in north Brazilian mangrove creeks Krumme, U.a*, Keuthen, H.b, Saint-Paul, U.a and Villwock, W.b Center for Tropical Marine Ecology, ZMT, Fahrenheitstr. 6, 28359 Bremen, Germany a Zoological Institute and Zoological Museum, University of Hamburg, Martin-Luther-King-Platz 3, 20146 Hamburg, Germany b *e-mail: Received April 11, 2005 – Accepted July 22, 2006 – Distributed August 31, 2007 (With 4 figures) Abstract Stomach contents were examined from 102 banded puffer, Colomesus psittacus (Tetraodontidae), caught from intertidal mangrove creeks at diurnal neap tides between June and September, 1997 (early dry season) near Bragança (north Brazil). The study found that C. psittacus were specialized predators of Cirripedia (Balanus spp.) and Brachyuran crabs (Uca spp., Pachygrapsus gracilis) (mean: 58 and 38% by dry weight, respectively), emphasizing a short food chain in the mangrove system. Cirripedia and Brachyura dominated the diet in all size classes, however, the prey spectrum narrowed with fish size. The mean daily consumption of Cirripedia and Brachyura was 6.2% body weight of C. psittacus. On average C. psittacus consumed 100.3 g.ha-1.d-1 of Cirripedia and 178.7 g.ha-1.d-1 of Brachyura (wet weight). The predation on Brachyuran crabs – a significant driver of fluxes of organic matter and energy in the system – provides C. psittacus with an important ecological function in the mangrove food web. A plant-animal interaction is proposed where C. psittacus exerts a mutually beneficial cleaning function on the Aufwuchs (Cirripedia and associated epibiota) of Rhizophora mangle stilt roots. Our results and those of other studies suggest that C. psittacus encounter optimum foraging conditions in the mangrove at high inundations at daylight (spring tide-day) whereas darkness and low inundations are linked to poor foraging conditions (neap tide-night). The C. psittacus resource could be used as an alternative income in the region in terms of i) sustainable catch and filet processing for exports to East Asia, ii) developing certified aquaculture methods for breeding puffers for the aquarium trade. Keywords: Brachyura, Cirripedia, fish diets, ontogeny, plant-animal interaction. Contribuição à ecologia alimentar do baiacu Colomesus psittacus (Tetraodontidae) em canais de maré com vegetação de mangue no norte do Brasil Resumo Conteúdos estomacais de 102 baiacus Colomesus psittacus (Tetraodontidae) foram examinados. A amostragem foi realizada em canais de maré com vegetação de mangue, durante as marés de quadratura de dia, entre junho e setembro de 1997 (no início do período seco), nas proximidades de Bragança (norte do Brasil). O estudo constatou que C. psittacus era um predador especializado em Cirripedia (Balanus spp.) e Brachyura (Uca spp., Pachygrapsus gracilis), com médias de 58 e 38% em peso seco, respectivamente, caracterizando uma curta cadeia alimentar no sistema de manguezal. Cirripedia e Brachyura dominaram a dieta em todos os tamanhos, entretanto, o espectro alimentar diminuiu de acordo com o tamanho do peixe. O consumo diário médio de Cirripedia e Brachyura foi de 6,2% em peso corporal de C. psittacus. C. psittacus consumiu uma média de 100,3 g.ha-1.d-1 de Cirripedia e 178,7 g.ha-1.d-1 de Brachyura (peso úmido). A intensa predação de Brachyura por C. psittacus enfatiza a importante função ecológica desta espécie na cadeia alimentar do manguezal, contribuindo significativamente no fluxo de matéria orgânica. Uma interação planta-animal é indicada no fato que C. psittacus exerce uma função limpadora mutuamente beneficiável ao se alimentar do Aufwuchs (Cirripedia e epibiota asociada) que cresce nas raízes aéreas de Rhizophora mangle. Nossos resultados e os de outros estudos sugerem que C. psittacus encontra no manguezal as melhores condições para se alimentar no período diurno durante as maiores inundações (marés de sizigia - de dia), enquanto que períodos noturnos e de pequenas inundações determinam as piores condições para forragear (maré de quadratura - de noite). C. psittacus poderia ser usado como alternativa de renda na região com respeito a: i) pesca sustentável e processamento de filés para exportação ao leste da Ásia, ii) desenvolvimento de métodos de aqüicultura certificada para a criação de baiacu para o comércio de peixes ornamentais. Palavras-chave: Brachyura, Cirripedia, dieta de peixes, ontogenia, interação planta-animal. Braz. J. Biol., 67(3): 383-392, 2007 383 Krumme, U. et al. 1. Introduction In the western Pacific, tetraodontids are commercially valuable and highly regarded as fish food, even though the presence of the family-specific tetraodoxin still causes the death of gastronomers each year (Fiedler, 1991). Furthermore, there is an increasing demand for tetraodontids in the aquarium trade. Although tetraodontids are used commercially, basic ecological knowledge of natural populations is usually scarce. In tropical and subtropical mangroves, tetraodontids are often amongst the most common fish species sampled (Bell et al., 1984; Hindell and Jenkins, 2004). The banded puffer Colomesus psittacus (Bloch and Schneider, 1801) is distributed along the coast from east Venezuela to north Brazil but also occurs in freshwater, e.g. several 100 km upstream in the Amazon and its tributary river systems (Barthem, 1985; Cervigon et al., 1992). In freshwater, C. psittacus is carnivorous, feeding mainly on mollusks (Keith et al., 2000) but little is known about marine environments. In mangroves along the north Brazilian coast C. psittacus is one of the dominant fish species of tidal channels year-round (Castro, 2001; Barletta et al., 2003; Krumme, 2004; Krumme et al., 2004). The intestines of tidally migrating C. psittacus were empty at flood tide and well-filled at ebb tide when the fish returned from the intertidal zone (Krumme, 2004). C. psittacus is usually the only tretraodontid species in these mangroves. Juvenile Spheroides testudineus occur as accidental visitors. The toxicity of pufferfish is well-known among fishermen and only very few seem to have really ever eaten puffer filet (pers. comm. with fishermen). Therefore, C. psittacus is usually discarded from the semi-commercial tapagem and curral catches (Barletta et al., 1998) and is of no commercial importance and not marketed. Puffers have three defense mechanisms against predators: being poisonous, inflation (with water or air) and aposematism (dorsal transverse black bars as warning coloration; Krebs and Davies, 1993). Puffers have a beak-like, terminal mouth with a bony plate in both jaws that can crush hard-shelled organisms. In mangroves, these adaptations enable them to prey on the ubiquitous fiddler crabs, which are unapproachable by many other fish species. Given the important functional role that these crabs have, puffers may have a significant impact on the ecological functionin (...truncated)