Trophic ecology of northern Australia's terapontids: ontogenetic dietary shifts and feeding classification

Abstract

The diets of 21 terapontid species from freshwater environments in northern Australia were investigated to determine the similarity and dissimilarity among species and the extent of any ontogenetic shifts. Distinct ontogenetic dietary shifts occurred in all species for which sufficient data were available, with many species passing through several discrete trophic categories during their life histories. Diets of all juvenile terapontids were similar, mainly comprising aquatic insects and zooplankton. Larger size classes of terapontids diverged into a broad spectrum of feeding groups comprising carnivorous dietary modes (including piscivory and lepidophagy), omnivory (including frugivory and consumption of allochthonous prey), herbivory and detritivory. The results indicate that the terapontids represent Australia's most trophically diverse freshwater fish family.

Omnivory and opportunism characterize food webs in a large dry-tropics river system

“…Also shown is mean connectance (with standard deviation [SD]) across all sites. Sites as per Table 1 juveniles of most terapontid species are invertivorous, but become carnivorous, omnivorous, herbivorous, or detritivorous as they grow (Davis et al 2011). These transitions also are affected by habitat and environmental variability (Davis et al 2012b).…”

“…However, Kilham et al (2009) reported Δδ 15 N values between 0.8 and 3.4‰ across food webs in tropical and temperate aquatic ecosystems, and McCutchan et al (2003) found that δ 15 N in consumers can vary depending on diet: 1.4 ± 0.20‰ on macroinvertebrate and 3.3 ± 0.26‰ on high-protein diets. Assigning discrete TEF values to herbivorous and predatory macroinvertebrates was straightforward because of their conservative dietary preferences, whereas fish were assigned to feeding groups on the basis of stomach-content analysis (see Davis et al 2011) and previous studies (Jepsen and Winemiller 2002, Douglas et al 2005 because of their widespread omnivory in tropical rivers. Some species had large δ 15 N values that placed them outside source-mixing polygons even after TEF correction, so we used alternative (nontrophic aligned) TEF values to place fishes within the source-mixing polygon (site-specific predator TEF used first, then H. fuliginosus size class 4 TEF -8.06 ± 0.47, which was the largest calculated TEF in our study).…”

Ontogenetic development of intestinal length and relationships to diet in an Australasian fish family (Terapontidae)

“…Fish for dietary and morphometric quantification were collected from a number of fish survey studies conducted across fresh water and marine habitats across Australia [44] and Papua New Guinea, as well as being sourced from museum collections. Fish were preserved in either buffered formalin or ethanol.…”

“…The Terapontidae is one of the most speciose and trophically diverse of Australia’s freshwater fish families, exhibiting carnivorous, omnivorous, herbivorous and detritivorous feeding habits [44]. A genus-level phylogeny of the family by Vari [45] relied heavily on differences in ontogenetic development of intestinal configuration as a diagnostic character.…”

Age and size compositions, habitats, growth and reproductive characteristics of a terapontid (Pelates octolineatus) in coastal waters

“…This family is widely distributed in the marine coastal, brackish and freshwaters of the Indo-West Pacific from Africa to Japan, Fiji and Samoa, with at least 22 of these species occurring in Australian waters, where some are particularly abundant (Morgan et al 1998;Davis et al 2011). Seagrass provides a nursery habitat for the eastern striped grunter Pelates sexlineatus in estuaries in eastern Australia (Smith and Suthers 2000) and for its congener the western striped grunter Pelates octolineatusand the sea trumpeter Pelsartia humeralis in coastal marine waters in south-western Australia (Valesini et al 1997(Valesini et al , 2004Crawley et al 2006;Wakefield et al2013).…”