The potential of fiddler crabs for secondary productivity of mangroves

Mangroves are well-recognized productive environments that perform important ecological functions such as nursery areas for marine life, coastline protection, carbon sequestration, and the production of fishery resources. Despite the productivity of mangroves being a highly valuable ecosystem service, studies on this subject are mainly concentrated on primary production. However, most economically important fish species benefit from the secondary productivity of mangroves, as they feed on organisms that are lower in the trophic levels. In Brazilian mangroves, fiddler crabs have the potential to be one of the main contributors to secondary production due to their high abundance and generalist distribution. Fiddler crabs produce pelagic larvae that develop in coastal environments adjacent to mangroves and therefore constitute a food resource for planktivorous fish. Although the contribution of fiddler crabs to secondary productivity is not yet well understood, it could be affected by climate change, as these crustaceans are sensitive to temperature variations. The aim of this study was to estimate the secondary productivity of fiddler crab larvae in the Santos/São Vicente estuary. For this, the presence of ovigerous females and the ambient temperature in populations of four species of fiddler crabs were monitored ( <i>Leptuca uruguayensis, L. leptodactyla, L. thayeri</i><i> </i>and <i>Minuca rapax</i>)<i>.</i> In the laboratory, larval production per species was estimated and it was tested whether the fertility of females is affected by increasing temperature. The density of fiddler crab larvae in coastal waters was evaluated according to distance from the coast and season. This study aimed to elucidate the ecological and economic importance of mangroves and to assess how climate change affects one of their most characteristic ecosystem services—productivity.