Stable‐isotope analysis reveals sources of organic matter and ontogenic feeding shifts of a mangrove‐dependent predator species, New Granada sea catfish, Ariopsis canteri

Abstract

To gain a better understanding on the trophic ecology of New Granada sea catfish, Ariopsis canteri, and their linkage to mangroves, nitrogen and stable carbon isotopes (δ 15 N and δ 13 C), as well as Bayesian mixing models, were used to explore trophic dynamics and potential ontogenic feeding shifts across different size classes: class I (8-20 cm), class II (21-32 cm) and class III (>32 cm). The study area was the estuary of the Atrato River Delta, where information about fish ecology is scarce. The δ 13 C of size class I was lower (mean ± S.D. = −24.96 ± 0.69‰) than that of size classes II (−22.20 ± 0.90‰) and III (−22.00 ± 1.96‰). The δ 15 N of size class I was lower (mean ± S.D. = 8.50 ± 0.67‰) than that of size classes II (9.77 ± 0.60‰) and III (10.00 ± 0.66‰). Body size was positively and significantly correlated to δ 15 N and δ 13 C. Individuals with L T > 32 cm presented the highest estimated trophic position (3.8). Five-source mixing models indicated that for class I, the mean estimated contribution of macroalgae was the highest (6%-57% C.I.), and for classes II and III, the mean estimated contribution of macrophytes was the highest (3%-53% C.I. and 4%-53% C.I., respectively). Ontogenetic feeding shifts of A. canteri were confirmed evidencing decreasing intraspecific competition between small and large individuals. Results suggest that mangroves are a nursery and feeding ground habitat for this species and that mangroves support A. canteri mainly due to the substrate/habitat that supports sources in the food webs. These results can be used in ecosystem-based fishery management focused on the protection of extensive mangrove areas in the southern Caribbean Sea.

Interpopulation trophic niches and ontogenetic shifts of a mangrove fish predator

“…Another major finding was the observation of an ontogenetic decrease in IPI through ontogeny, which was associated with a diet shift towards greater specialization, particularly with regard to more large prey items ( e.g ., small fishes, as indicated by increased trophic position) (Sandoval et al ., 2020). According to the optimal foraging theory, feeding on large prey has an energetic benefit and typically results in strong somatic conditions (Carbia et al ., 2020), which can be especially beneficial to reproductive allocation.…”

“…Particularly within mangrove ecosystems, the stable isotope method has been frequently used to assess the trophic niche of fish predators (e.g., Hammerschlag et al, 2010) and has proven to be an excellent approach to explore ontogenetic niche shifts (Sandoval et al, 2020;Xu et al, 2012).…”

“…This technique clearly outperforms more traditional dietary analyses in that it can provide more long‐term and time‐mediated information on a species' diet as well as quantify trophic niche in space and time (Hammerschlag‐Peyer et al ., 2011). Particularly within mangrove ecosystems, the stable isotope method has been frequently used to assess the trophic niche of fish predators ( e.g ., Hammerschlag et al ., 2010) and has proven to be an excellent approach to explore ontogenetic niche shifts (Sandoval et al ., 2020; Xu et al ., 2012).…”

The isotopic niche of the macrobenthos in a major mangrove area of the southern Caribbean Sea

“…In addition, isotopic niches have been useful to compare the trophic structure of fish communities across habitats and seasons (Shahraki et al, 2014;Sepulveda-Lozada et al, 2017;Stuthmann, Castellanos-Galindo, 2020), and to assess ontogenetic shifts of fish predators (e.g. Sandoval et al, 2020b;Jiao et al, 2022). Recently, Medina-Contreras and Arenas (2022) have highlighted that the isotopic niche is also useful for tracking the effect of anthropogenic activities in mangrove ecosystems, where the in a tin capsule for isotopic analysis.…”