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Fish communities were studied in 38 stations located in two mangrove lagoons of Guadeloupe (Caribbean): the bays of Petit Cul-de-Sac Marin (PCSM) and Grand Cul-de-Sac Marin (GCSM). Fishes were sampled with nets during the dry season, and 14 environmental descriptors were recorded in each site. A total of 105 fish species were observed in mangrove lagoons. Ordination analyses and classifications were performed on data sets related to fish presence-absence, abundance, and biomass. The PCSM stations and GCSM mangrove islets sites are characterised by an assemblage composed by fish species either found in coral reefs, seagrass beds, or mangroves. Distinct mangrove fish assemblages are found across environmental gradients linked to salinity, proximities of reefs and river mouths, and presence of seagrass beds. Considering trophic categories, planktivores are numerically dominant in most stations, whereas second-order carnivores and omnivores dominate in biomass in river mouths stations of the GCSM Bay. First-level carnivores are mainly observed in mangrove stations with neighbouring seagrass beds. These last results suggest that food availability plays an important role in the structure of mangrove fish communities in addition to abiotic factors.

The feeding habits and habitats of the speckled worm eel Myrophis punctatus were studied on the mangrove edge of the Indian River Lagoon (IRL, Florida) using gut-content and stable-isotope analyses of carbon (δ(13) C) and nitrogen (δ(15) N). Four taxa were identified through analyses of gut contents, and the index of relative importance suggested that amphipods, microphytobenthos and annelids are the most important food sources in the fish's diet. To assess the feeding habits of the fish after their recruitment to the IRL, these food sources were collected from mangroves and nearby seagrass beds for isotope analyses. Stable isotopes constituted a powerful tool for discriminating fish prey items from mangroves (mean ± s.d.δ(13) C = -20·5 ± 0·6‰) and those from seagrass beds (mean ± s.d.δ(13) C = -16·9 ± 0·6‰), thus providing good evidence of food source origins. The 56 M. punctatus collected [10·0 < total length (L(T) ) < 16·2 cm] had average isotopic signatures of δ(13) C = -16·7 ± 0·2‰ and δ(15) N = 8·2 ± 0·1‰. A significant depletion in (13) C was observed for larger juveniles (15·0 < L(T) < 16·2 cm), suggesting that they found a portion of their food in mangroves. Estimation of the trophic level from stable isotopes (T(Liso)) was similar among different size groups of juvenile fish (T(Liso) = 3·2-3·5); therefore, M. punctatus was considered a secondary consumer, which is consistent with its zoobenthic diet. The concentration-dependent mixing Stable Isotope Analysis in R (SIAR) model revealed the importance of food sources from seagrass beds as carbon sources for all the fish collected, with a significant increase in mangrove prey contributions, such as annelids, in the diet of larger juveniles. This study highlights the importance of seagrass beds as feeding habitats for juveniles of M. punctatus after their recruitment to coastal waters.

SummaryWeight-length relationships (WLR) are reported for 20 fish species from the mangroves of Guadeloupe (Lesser Antilles). The fishes were collected using fishing hoop nets. In the present study, the regressions were calculated after separating juveniles and adults. The b coefficient in the WLR varied between 2.37 and 3.85, with a mean of 3.15 ± 0.15.

Stable isotope (δ(13)C and δ(15)N) and gut content analyses were used to investigate size-related feeding habits of four reef fishes (the beaugregory Stegastes leucostictus, the french grunt Haemulon flavolineatum, the schoolmaster snapper Lutjanus apodus and the yellowtail snapper Ocyurus chrysurus) inhabiting an offshore (non-estuarine) mangrove islet off Belize, Central America. Comparisons of isotopic niche space and Schoener diet similarity index suggested a low to moderate degree of niche overlap between fish size groups. The δ(13)C gradient between mangrove and seagrass prey as well as results of Bayesian mixing models revealed that sampled fishes relied mostly on seagrass prey items. Only small and large juveniles of the carnivorous species L. apodus derived a part of their diet from mangroves by targeting mangrove-associated Grapsidae crabs and fish prey, respectively. Isotopic niche shifts were particularly obvious for carnivorous fishes that ingested larger prey items (Xanthidae crabs and fishes) during their ontogeny. The utilization of mangrove food resources is less than expected and depends on the ecology and life history of the fish species considered. This research highlights that mangrove-derived carbon contributed relatively little to the diets of four fish taxa from an offshore mangrove islet.

ABSTRACT. Mangroves and seagrass beds represent suitable fish habitats as nurseries or feeding areas. This study was conducted in a Caribbean lagoon to assess the foraging habits of juvenile transient reef fishes in these two habitats. Twelve fish species were sampled in coastal mangroves, an offshore mangrove islet, and a seagrass bed site, and stable isotope analyses were performed on fishes and their prey items. The SIAR mixing model indicated that transient fishes from both mangroves and seagrass beds derived most of their food from seagrass beds and their associated epiphytic community. Only a few species including planktivores (Harengula clupeola, Anchoa lyolepis) and carnivores (Centropomus undecimalis and small specimens of Ocyurus chrysurus) presented depleted carbon values, showing reliance on mangrove prey in their diets. Mangrove-derived organic matter contributed marginally to the diet of transient fishes, which relied more on seagrass food sources. Thus, mangroves seem to function more as refuge than feeding habitats for juvenile transient fishes.Keys words: mangrove, seagrass, fish, stable isotopes, SIAR. RESUMEN.Los manglares y las praderas de pastos marinos son hábitats adecuados para la reproducción y alimentación de peces. En este estudio se evaluaron los hábitos alimentarios de peces arrecifales juveniles que transitan por estos dos tipos de hábitat en una laguna del Caribe. Se recolectaron 12 especies de peces en los manglares costeros, un islote de manglares y un sitio de praderas de pastos marinos, y se realizaron análisis de isótopos estables en los peces y sus presas. El modelo SIAR indicó que los peces transeúntes se alimentaron principalmente de los pastos marinos y su comunidad epifita asociada. Sólo unas cuantas especies incluyendo peces planctívoros (Harengula clupeola, Anchoa lyolepis) y carnívoros (Centropomus undecimalis y pequeños ejemplares de Ocyurus chrysurus) presentaron valores de carbono empobrecidos, lo que indica una dependencia de las presas de manglares para sus dietas. La materia orgánica producida en el manglar contribuyó poco a la dieta de los peces transeúntes, los cuales dependieron más de fuentes provenientes de los pastos marinos. Por lo tanto, los peces juveniles transeúntes usan los manglares más como refugio que como hábitat de alimentación.

Foraging habitats of juveniles of the Mayan cichlid, Cichlasoma urophthalmus (Günther, 1862), were investigated in two mangrove ponds located in Twin Cays offshore islet in Belize: Sink Hole pond (SH) and Hidden Lake pond (HL). Sink Hole pond is a semiclosed body of water, whereas Hidden Lake pond is connected by a channel to adjacent seagrass beds that surround the islet. Gut contents of 21 juvenile C. urophthalmus (9.8-13.2 cm total length) were analyzed, and five prey taxa were identified. In both mangrove ponds, C. urophthalmus were opportunistic carnivores and consumed primarily crustaceans. Plant material and detritus present in gut contents were most likely ingested incidentally when the fish foraged on small invertebrates. Carbon isotopic values of fish specimens from the two ponds were similar (mean ± SD of -19.2 ± 0.4‰ in SH and -19.4 ± 0.4‰ in HL), and were close to those of mangrove prey (mean ± SD = -20.2 ± 1.5‰), suggesting that this fish species forages in this habitat. Mixing models showed a higher contribution of mangrove food sources to the fish diet than seagrass food sources. This study reveals that young Mayan cichlids, inhabiting two Belize mangrove ponds, are generalists and opportunistic carnivores that forage on mangrove food sources and do not appear to move to adjacent seagrass beds to complement their diets. Understanding trophic linkages between aquatic consumers and food resources may contribute to better management of threatened coastal ecosystems.Habitats de alimentação de juvenis do ciclídeo-maia, Cichlasoma urophthalmus (Günther, 1862), foram investigados em duas lagoas de mangue localizadas nas ilhas Twin Cays em alto mar em Belize: Sink Hole Lake (SH) e Hidden Lake (HL). Sink Hole é um corpo d'água parcialmente isolado, enquanto Hidden Lake é ligada por um canal com bancos de sargaços que cercam a ilhota. O conteúdo estomacal de 21 juvenil de C. urophthalmus (9,8-13,2 cm de comprimento total) foram analisados e cinco táxons de presas foram identificados. Em ambas as lagoas de mangue, 'C.' urophthalmus foram carnívoros oportunistas e consumiram principalmente crustáceos. Material vegetal e detritos presentes no conteúdo digestivo foram provavelmente ingeridos acidentalmente quando o peixe se alimentava de pequenos invertebrados. Os valores de isótopos estáveis do carbono em espécimes de peixes das duas lagoas foram semelhantes (média ± SD -19,2 ± 0,4 ‰ em SH e -19,4 ± 0,4 ‰ em HL), e foram próximos aos de presas de mangue (mean ± SD = -20.2 ± 1.5 ‰), sugerindo que esta espécie de peixe vai à procura de alimentos neste habitat. Modelos mistos mostraram uma maior contribuição de fontes alimentares de mangue para a dieta dos peixes do que de fontes alimentares de algas marinhas. Este estudo revela que juvenis do ciclídeo-maia que habitam duas lagoas de mangue em Belize, são carnívoros generalistas e oportunistas que se ingerem alimentos dos manguezais e não parecem se mover para leitos de algas marinhas adjacentes para complementar suas dietas. Compreender as ligações tróficas ent...

International audienceResource use of seagrass herbivorous fishes Resource use by three juvenile scarids (Cryptotomus roseus, Scarus iseri, Sparisoma radians) in Caribbean seagrass bed