Trophic position and isotopic niche of mangrove fish assemblages at both sides of the Isthmus of Panama

Fishes are important components of marine coastal ecosystems, often represented in food webs as second and third order consumers. Fish trophic positions (TP) in these food webs can vary across ontogeny and accurate estimation can provide insights into the functioning of these ecosystems. Mangrove ecosystem function can also vary depending on local and regional environmental conditions. Panamanian mangroves in the Caribbean Sea and the Pacific Ocean occur under strikingly different environmental conditions after the closure of the Panama Isthmus over 3 mya and likely function differently. Here, we use δ¹⁵N and δ¹³C and Bayesian models to calculate the TP and the Convex Hull Area (TA) of the most common fish species inhabiting mangroves of the Gulf of Montijo and Bocas del Toro on the Pacific and Caribbean coasts of Panama, respectively. Thirteen dominant fishes were used for the estimation of TP, eight in the Pacific and five in the Caribbean. Mean TP of the communities was similar but with significantly larger variations in the Caribbean than in the Pacific. Similarly, the TA was larger for the Caribbean fish assemblage than for the Pacific. Both results indicate that trophic modes in the Caribbean fish assemblages are more varied than in the Pacific. With some exceptions, FishBase TP estimates correlated positively with TP stable isotope estimates. Our results suggest that TP and TA are good proxies for mangrove fish communities' trophic modes and that these metrics may vary depending on mangrove environmental settings.