https://nova.newcastle.edu.au/vital/access/ /manager/Index en-au 5 https://nova.newcastle.edu.au/vital/access/ /manager/Repository/uon:48212 Wed 28 Jun 2023 20:19:32 AEST ]]> https://nova.newcastle.edu.au/vital/access/ /manager/Repository/uon:34563 Othos dentex and to use these data, together with in situ observations of feeding behaviour, to elucidate how foraging and diet are optimized by this piscivorous serranid. Seasonal spear and line fishing over reefs in south-western Australia yielded 426 O. dentex (total length, L_T, 183-605 mm), among which the stomachs of 95 contained food. The food in the stomachs of 76 fish was sufficiently undigested to be seen to contain, almost invariably, a single fish prey, which was typically identifiable to family and often to species. The prey of O. dentex, which were measured (L_T), represented 10 families, of which the Labridae and Pempheridae constituted nearly two-thirds of the prey volume. Two-way crossed analysis of similarities of volumetric data for stomach contents showed that the dietary compositions of the different length classes of O. dentex in the various seasons were significantly related to length class of prey, but not to prey family, length class within the various prey families or season. Furthermore, an inverse (Q-mode) analysis, including one-way analysis of similarities, showed that the patterns in the prey consumed by the different length classes of O. dentex in the various seasons were related more strongly to length class than prey family. The former trend is exemplified in a shade plot, by a marked diagonality of the length classes of prey with increasing predator size. The ingestion of typically a single teleost prey, whose body size increases as that of O. dentex increases, reduces the frequency required for seeking prey, thus saving energy and reducing the potential for intraspecific competition for food. The ability of O. dentex to ingest large prey is facilitated by its possession of a very large gape, prominent recurved teeth, dorsal and independently-moveable eyes, cryptic colouration and effective ambush behaviour. Othos dentex has thus evolved very cost-effective mechanisms for optimizing its foraging and diet.]]> Wed 27 Mar 2019 17:05:17 AEDT ]]> https://nova.newcastle.edu.au/vital/access/ /manager/Repository/uon:40517 Wed 19 Apr 2023 10:00:48 AEST ]]> https://nova.newcastle.edu.au/vital/access/ /manager/Repository/uon:52139 Wed 04 Oct 2023 09:53:04 AEDT ]]> https://nova.newcastle.edu.au/vital/access/ /manager/Repository/uon:36499 D) and their embryos (7.0–42.3 cm W_D) and also yolks and histrotroph, to assess the potential implications for juvenile nutrition and habitat use. Irrespective of their development in the uterus, embryos had similar δ¹³C values in their muscle tissue as the mothers and both had greater values than in the histotroph. During gestation, δ¹³C values increased across all sample types. However, while embryo muscle tissue and the histotroph were associated with increasing ¹⁵N levels during embryonic development, this was depleted in the mothers’ muscle tissue and yolk. Although speculative, the observed variation in stable‐isotope ratios might imply a dietary shift among gravid females during their early gestation. Irrespective of the underlying mechanisms, the results indicate neonates will have relatively greater δ¹⁵N values than post‐partum females, which would probably confound juvenile foraging‐ecology estimates.]]> Tue 26 May 2020 13:53:17 AEST ]]> https://nova.newcastle.edu.au/vital/access/ /manager/Repository/uon:37666 Choerodon rubescens in marine waters of the outer reefs in the World Heritage Area of Shark Bay (26° S; 114° E) and of Choerodon schoenleinii in inner protected reefs of that large embayment. The dietary compositions of C. rubescens and C. schoenleinii differed significantly among length classes, progressed serially with increasing body size, both overall and almost invariably in each season and were more closely related to body size than season, whose effect was at best minimal. The size‐related dietary change in C. rubescens involved, in particular, a shift from crustaceans and non‐mytilid bivalves to mytilid bivalves and echinoid echinoderms. Although the diet of C. schoenleinii followed similar size‐related changes, it contained a greater volume of gastropods when the fish were small and mytilids when large and only a small volume of echinoids. The dietary composition of C. rubescens in the Abrolhos Islands, 300 km to the south of Shark Bay, was related both to length class and season and differed from that of this labrid in Shark Bay with the ingestion of lesser volumes of mytilids and greater volumes of echinoids. The size‐related changes in diet imply that these species shift from foraging over soft substrata to over reefs as their very well‐developed jaws become sufficiently strong to remove attached and larger prey. The dietary compositions of C. rubescens and C. schoenleinii in Shark Bay and of C. rubescens at the Abrolhos Islands were related far more to habitat–locational differences than to length class and season. The above intraspecific and interspecific differences in diet are consistent with qualitative accounts of the relative abundances of the main prey in their respective environments, supporting the view that, despite specializations in their feeding apparatus, these labrids can feed opportunistically to a certain extent and could thus potentially respond to moderate changes in the composition of their prey caused by climate change and other anthropogenic effects.]]> Tue 09 Mar 2021 18:05:52 AEDT ]]> https://nova.newcastle.edu.au/vital/access/ /manager/Repository/uon:38530 Thu 28 Oct 2021 14:47:01 AEDT ]]> https://nova.newcastle.edu.au/vital/access/ /manager/Repository/uon:37768 Sphyrna mokarran are the largest member of Sphyrnidae, yet the roles of these large sharks in the food webs of coastal ecosystems are still poorly understood. Here we obtained samples of muscle, liver and vertebrae from large S. mokarran (234–383 cm total length; L_T) caught as by‐catch off eastern Australia and used stable‐isotope analyses of δ¹⁵N, δ¹³C and δ³⁴S to infer their resource use and any associated ontogenetic patterns. The results indicated large S. mokarran are apex predators primarily relying on other sharks and rays for their diet, with a preference for benthic resources such as Australian cownose rays Rhinoperon neglecta during the austral summer. Teleosts, cephalopods and crustaceans were not significant components of S. mokarran diets, though some conspecifics appeared to rely on more diverse resources over the austral summer. Ontogenetic shifts in resource use were detected but trajectories of the increases in trophic level varied among individuals. Most S. mokarran had non‐linear trajectories in ontogenetic resource‐use shifts implying size was not the main explanatory factor. Stable isotope values of δ¹³C and δ³⁴S in muscle suggest S. mokarran span coastal, pelagic and benthic food webs in eastern Australia.]]> Thu 15 Apr 2021 10:37:54 AEST ]]> https://nova.newcastle.edu.au/vital/access/ /manager/Repository/uon:5275 Sat 24 Mar 2018 07:46:27 AEDT ]]> https://nova.newcastle.edu.au/vital/access/ /manager/Repository/uon:30353 Sat 24 Mar 2018 07:40:24 AEDT ]]> https://nova.newcastle.edu.au/vital/access/ /manager/Repository/uon:4694 Sat 24 Mar 2018 07:19:26 AEDT ]]> https://nova.newcastle.edu.au/vital/access/ /manager/Repository/uon:48196 Sat 11 Mar 2023 12:30:29 AEDT ]]> https://nova.newcastle.edu.au/vital/access/ /manager/Repository/uon:51569 Mon 11 Sep 2023 14:22:22 AEST ]]> https://nova.newcastle.edu.au/vital/access/ /manager/Repository/uon:40580 Fri 30 Jun 2023 10:30:28 AEST ]]>