Trophic niches of estuarine fish and evidence of mangrove-fishery causal links in the Southern Caribbean (Colombia)

Abstract

The trophic organization of estuarine fish communities is poorly known. We used Stable Isotopes (δ¹³C and δ¹⁵N) to classify the most abundant fishes of the Atrato River Delta (Colombia) into trophic guilds. We examined trophic niches and the relationships between the abundance of the trophic guilds (catch per unit effort) and environmental variables. The zoobenthivores were the dominant trophic guild. The isotopic niche width, based on Bayesian estimate of the standard ellipse areas, was more significant for carnivores (25.3‰²) and planktivores (24.4‰²) than for omnivores (7.8‰²) and phytobenthivores (3.1‰²). The overlap combinations showed a medium probability of isotopic overlap (≈50%) between carnivores and planktivores and between carnivores and omnivores. Isotopic niche size and overlap suggested diversity in food sources and considerable niche segregation of the fish community. Mangrove area was the main factor explaining the abundance of omnivores and zoobenthivores, supporting that the causal links between mangrove habitat and local fishery production may be explained through the trophic contribution of mangroves and mangrove-related sources. The results underscore the importance of mangrove areas in the trophic organization of fish communities and can inform strategies aimed at managing the ecosystem impacts of fishing and protecting extensive mangrove areas in the southern Caribbean.