https://ogma.newcastle.edu.au/vital/access/ /manager/Index ${session.getAttribute("locale")} 5 https://ogma.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://ogma.newcastle.edu.au/vital/access/ /manager/Repository/uon:39161 in situ microhabitat assessments to assess whether reef fish community structure on shallow (6-9 m) rocky reefs varied with spatial management zone (NTAs versus PPAs), sampling season (autumn, spring) and benthic habitat condition around coastal islands and headlands within the Port Stephens-Great Lakes Marine Park (established in 2007). While fish community composition and the relative abundance of fish species did not differ significantly across spatial management zones, there were significant differences among sampling season, and spatial variation at the site level that was partly explained by geomorphology (island/headland). Notably, there was a strong association between variation in fish community structure and site-level cover of canopy-forming macroalgae among islands and headlands, which transcended management zones. Our study suggests that balancing habitat condition and geomorpho-logical setting (islands, headlands) among management zones is key to the conservation and management of shallow-water reef fish assemblages. In particular, the percent cover of canopy-forming macroalgae may be a key habitat indicator for designing, monitoring and re-balancing spatial management zones.]]> Wed 22 Mar 2023 18:16:59 AEDT ]]> https://ogma.newcastle.edu.au/vital/access/ /manager/Repository/uon:38235 Tue 27 Feb 2024 14:06:16 AEDT ]]> https://ogma.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://ogma.newcastle.edu.au/vital/access/ /manager/Repository/uon:36777 Urolophus cruciatus and U. paucimaculatus, and one draughtboard shark, Cephalocyllium laticeps) in response to an approaching demersal trawl to quantify behavioural factors that affect their catchability. The morphologically similar U.cruciatus and U. paucimaculatus were similarly abundant, i.e. 290 and 218 individuals, respectively, but displayed different net avoidance behaviours, with U. paucimaculatus being far more likely to enter the trawl. The greater catchability of U. paucimaculatus would falsely suggest this less common species was more abundant than U. cruciatus, which has implications for any assessments of the impacts of trawling on these two elasmobranchs. Collision with trawl gear was relatively common for both Urolophus spp., and this was shown to decrease their likelihood of capture. In contrast, only 1 of the 68 individuals of the morphologically-different C. laticeps collided with gear. These results will help inform future development of BRDs and highlight that understanding the behaviour of elasmobranchs in response to capture methods should form an integral component of assessments of the impacts of trawling on this highly affected group.]]> Thu 16 Feb 2023 10:01:07 AEDT ]]> https://ogma.newcastle.edu.au/vital/access/ /manager/Repository/uon:51928 350 m. On the south coast of Western Australia, depth distributions undergo an overlapping progressive gradation, from C. lineatus in inshore and nearshore shallow waters, to C. gerrardi and C. australis in nearshore deep waters, and then B. splendens and B. decadactylus in offshore deep waters. The main dietary categories of C. gerrardi change with increasing body size from crabs and isopods in small fish to teleosts in the largest fish, in which volumetrically they constituted >60% of the stomach contents. The wide range of teleost prey (at least 39 species from 33 families) ingested by C. gerrardi would be valuable to this species if continuing climate change or other anthropogenic effects lead to alterations in the composition of potential prey. Differences between depth distributions account for the fish prey of C. gerrardi comprising nearshore species, such as those of clupeids, congrids, pomacentrids and platycephalids, whereas those of B. splendens (from studies elsewhere) are dominated by myctophids, which are abundant in deeper waters. The combination of a large mouth and numerous, exclusively small teeth (edentulate morphotype) strongly suggest that C. gerrardi is a suction feeder adapted to engulfing larger prey. While the co-occurring and likewise commercially-fished Oplegnathus woodwardi also ingests substantial volumes of crabs and teleosts, its diet is distinguished from C. gerrardi by large volumes of poriferans and appreciable volumes of echinoderms, likewise reflecting feeding specialisations. Although differing in depth distributions and dietary compositions, berycid species in general are close to the apex of the food web.]]> Fri 22 Sep 2023 11:00:08 AEST ]]>