Dietary separation between two blennies and the Pacific gregory in northern Taiwan: evidence from stomach content and stable isotope analyses

Abstract

Two blennies, Ecsenius lineatus Klausewitz and Ecsenius namiyei (Jordan and Evermann), and a cohabiting territorial damselfish, the Pacific gregory, Stegastes fasciolatus (Ogilby), were collected from shallow reefs in northern Taiwan between September and November 2004, and in October 2005 for stomach content and d 13 C and d 15 N analyses in an effort to study how extensively their food sources overlapped and to delineate the pattern of cohabiting interactions. These analyses showed differences in food use between the Ecsenius blennies and S. fasciolatus. However, there were inconsistencies. Epiphytic algae were their major food items of E. namiyei and E. lineatus. Macroalgae were rarely taken. Nevertheless, d 13 C and d 15 N signatures suggested that E. namiyei and E. lineatus might have assimilated mainly macroalgae-derived detritus instead of epiphytic algae. In contrast, macroalgae were the major food items of S. fasciolatus, followed by epiphytic algae. Differences in both d 13 C and 15 N values indicated that for S. fasciolatus, algae (both macroalgae and epiphytic algae) might not be as important as the stomach contents showed. Instead, polychaetes were possibly its major food source. Differences between stomach contents and evidence from the separation of stable isotope signatures between blennies and the Pacific gregory indicate that some of the interspecific interactions derived from exploitative competition may have been alleviated. Moreover, their widespread territory overlap is possibly a sign of mutualism: S. fasciolatus allows territory sharing, while Ecsenius blennies, in return, clean up the algal mat by removing sand and detritus.

Does hatchery-reared Siniperca chuatsi (Actinopterygii, Perciformes) compete significantly with two wild Siniperca populations for diets in a shallow lake?

“…2, 3). These results are consistent with many previous studies (Renones et al, 2002;Ho et al, 2007;Hadwen et al, 2007). In general, these discrepancies suggest that although individuals can focus their foraging on particularly abundant prey items on a day-to-day basis, they feed on a wider range of taxa over longer periods (Hadwen et al, 2007).…”

The cerato-mandibular ligament: a key functional trait for grazing in damselfishes (Pomacentridae)

“…Accurate bites should also be useful for weeding out the undesirable algae without scraping the palatable filamentous algae. The very low fecal ash contents in the herbivorous damselfish species Stegastes dorsopunicans and S. planifrons [76] and the low amounts of sediment in the stomach contents of Pomacentrus wardi, Stegastes fasciolatus, S. fuscus, S. variabilis and Dischistodus perspicillatus [77][78][79][80] suggest highly selective feeding bites.…”

Diversity of trophic niches among herbivorous fishes on a Caribbean reef (Guadeloupe, Lesser Antilles), evidenced by stable isotope and gut content analyses

“…Recently, Plass-Johnson et al (2013) recommended a mean nitrogen enrichment equal to +2.3‰ for parrotfishes, due to their diet consisting of both low and high-proteins foods. The use of stable isotope analyses has considerably increased over the last decades to discriminate different trophic groups in food web studies (Cocheret de la Morinière et al 2003, Carassou et al 2008Wyatt et al 2012), compare trophic niches in a fish community (Ho et al 2007, Frédérich et al 2009, Nagelkerken et al 2009, Layman and Allgeier 2012, Lamb et al 2012, show ontogenetic changes in diet (Cocheret de la Morinière et al 2003, Kolasinski et al 2009, Carreón-Palau et al 2013, Plass-Johnson et al 2013 or plasticity of feeding habits (Ho et al 2009). Coupling digestive content and stable isotopes analyses represents a powerful tool to determine trophic niches.…”