Hiding in plain sight: a summary of defensive tactics of fishes in mangroves and tidal creeks of northern coast of São Paulo, Brazil
by Ivan Sazima – aqua 25 (4) – pp. 133-148
Mangroves and tidal creeks harbour rich and varied fish assemblages composed mostly of small, juvenile, and larval individuals. Fish species that forage on the bottom or in the water column in open areas would be at greater risk of predation by visually-oriented hunters (piscivorous birds and fishes) than fish species that forage among vegetation. I studied open areas of shallow and clear stretches of two mangroves, two tidal creeks, and one inlet under freshwater influence in southeastern Brazil, and recorded morphological features and behavioural tactics that would lessen predation risks imposed to the fishes by piscivorous birds and fishes. Besides antipredator tactics of the fishes, I recorded potential visually-hunting predators at the same sites. Among the 24 fish species recorded, camouflage was the most common tactic and included crypsis (background matching and countershading) and masquerade (resemblance to decaying plant pieces). Transparency or translucency was another common form of camouflage, although restricted to larval stages. I also recorded instances of warning colouration, Batesian mimicry, and social mimicry. Fish species that used camouflage or mimicry as defensive tactics displayed particular behaviours, as well as colour changes, which enhanced their disguise. Most summaries and reviews on protective resemblance focus on fish species rather than habitats, and observational studies on defensive tactics against visually-guided predators in diverse habitats would be very instructive.