Predator-prey interactions associated with larval Gilchristella aestuaria (family clupeidae) in mangrove and non-mangrove estuaries

Abstract The predator-prey interactions between the larvae of a common mid-trophic species, Gilchristella aestuaria, and dominant zooplankton were compared between similar warm temperate estuaries with and without mangroves. It is hypothesized that higher abundances of G. aestuaria larvae and their prey species will be found in estuaries with mangroves as these systems would provide an enhanced feeding environment for all species, compared to estuaries devoid of mangroves. Generalized Additive Models found that an interaction of mangrove presence, turbidity, copepod prey density and competition pressures by predatory mysids were the most significant at explaining postflexion G. aestuaria densities. Postflexion G. aestuaria negatively selected Paracartia longipatella in the four sampled estuaries, despite co-occurring at high densities. Postflexion larvae consumed more of the larger copepod species, Pseudodiaptomus hessei, within the two mangrove estuaries than the two non-mangrove estuaries, despite other prey species occurring at similar densities. This selective feeding behaviour may be as a consequence of the relatively low prey densities found in all the sampled estuaries as well as the lower turbidity seen in the mangrove estuaries. This study is the first of its kind investigating the relationship between mangroves and fodder fish populations. It highlights the importance of predator-prey interactions when assessing the nursery value of mangrove habitats to fishes.