Rapid changes in fish utilization of mangrove habitat in Western Madagascar

Abstract

Fish use of a mangrove habitat was studied in a small mangrove forest on the West coast of Madagascar. A sand bar near the inlet retains water in parts of the channel (pools) at low tide. Fishes in four of these pools were examined daily at all phases of the tidal cycle for 3 weeks using underwater visual census. During week 1, fishes were diverse and abundant in all pools: the dominant species were cardinalfish (related to Apogon lateralis); monos, Monodactylus argenteus; black spotted snappers, Lutjanus ehrenbergi; double bar bream, Acanthopagrus bifasciatus; emperors, Lethrinus lentjan and L. sp., surgeon fish, Acanthurus nigricauda; red-lined sweetlips, Plectorhinchus plagiodesmis; and butterflyfish, Chaetodon kleini. Some species were more abundant in shaded pools; others in more open pools. During week 2 a dramatic difference was noted: the only fishes found were schools of cardinalfish and one moray eel. This week had neap tides, with high tides in the morning and low tides in the afternoon. As the week progressed and during week 3 (spring tides), fishes slowly repopulated the habitat and diversity increased. Monos, absent in week 2, now had increasing numbers of small individuals. While large emperors were scarce, small individuals appeared. The larger butterflyfish and surgeonfish seen in week 1 were replaced by small ones during week 3. Species that had been rare in week 1 were more abundant, including pipefish and small barracudas. While species richness increased during week 3, the community was strikingly different from that seen 2 weeks earlier. Only Pool 1, closest to the entrance, recovered its original species richness. Abundance was much lower than in week 1. Our snapshot study apparently captured a time when older juveniles left the mangrove forest and smaller fishes recruited into it. Utilization of this habitat will likely vary throughout the year depending on the reproductive cycle of the different species whose juveniles utilize it. Longer studies are needed to learn about cycles in fish use of the mangroves.

Tidal, diel and lunar patterns in intertidal and subtidal mangrove creek fish assemblages from southwest Thailand

“…In macrotidal mangroves of the Neotropics, the temporal patterns in intertidal habitat use of tidally-migrating fish have intensively been studied, based on intended comparisons between similar sites (North Brazil: e.g., Krumme et al 2004;Krumme 2004;Brenner and Krumme 2007;Krumme et al 2008;Giarrizzo et al 2010;Castellanos-Galindo and Krumme 2014;Pacific Colombia: Castellanos-Galindo and Krumme 2013). In contrast, in the Indo-Pacific realm, investigations on short-term patterns in intertidal mangrove fish communities are scattered over the whole region and the consolidation of these studies is constrained by methodological differences, including different habitat types, sampling methods, or survey designs (Australia: e.g., Davis 1988;Robertson and Duke 1990;Jelbart et al 2007;Meynecke et al 2008;Madagascar: Laroche et al 1997;Weis et al 2009;Thailand: Zagars et al 2011). Despite the methodological differences, the studies addressed various aspects of the role of tidal magnitude and the diel cycle for temporal changes in intertidal fish assemblage compositions and feeding activity, and some also provided evidence for regular tidal connectivity between mangroves at high tide and nearby subtidal habitats at low tide.…”

Finfish diversity and seasonal abundance in the largest arid mangrove forest of the Indus Delta, Northern Arabian Sea

“…Laroche et al (1997). Weis et al (2009) has also examined mangrove fish assemblages in the western Indian Ocean.…”