ORCID Profile
0000-0001-7180-6982
Current Organisations
Macquarie University
,
Charles Darwin University
,
NSW Department of Primary Industries
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Publisher: Wiley
Date: 17-08-2022
DOI: 10.1002/ECY.3812
Publisher: Inter-Research Science Center
Date: 30-07-2018
DOI: 10.3354/MEPS12661
Publisher: Wiley
Date: 22-03-2023
DOI: 10.1111/JFB.15370
Abstract: Recreational fishing waste, produced from processing catches at shore‐based fish cleaning facilities and discarded into adjacent waters, is foraged by various aquatic species. However, the potential alterations to the diet of consumers of these resources are poorly studied. Smooth stingrays ( Bathytoshia brevicaudata ) are a large demersal mesopredatory ray species and common scavenger of recreational fishing discards around southern Australia. Due to their attraction to fish cleaning sites, they are also common targets of unregulated ‘stingray feeding’ tourism where they are fed commercially produced baits ( e.g. , pilchards). This study provides a preliminary assessment of the diet of smooth stingrays provisioned recreational fishing discards and baits at two sites in southern New South Wales, Australia (Discard Site: recreational fishing discards only Provisioning Site: recreational fishing discards and commercial baits) using stable isotope analysis of carbon ( δ 13 C) and nitrogen ( δ 15 N), and Bayesian stable isotope mixing models. Our results indicate that at both sites invertebrates, considered a main part of the natural diet of smooth stingrays, made a limited contribution to the diets of provisioned stingrays, while a benthic teleost fish that is a common recreational catch was the dominant contributor. As the assessed teleost is potentially a natural prey item for smooth stingrays, it remains unclear whether the contribution came from recreational fishing discards or natural foraging. However, due to smooth stingrays’ typically opportunistic foraging strategy, we expected a greater mixture of resources from low to high trophic level prey than was observed. These results suggest that smooth stingrays have either lower reliance on invertebrates as a result of utilizing provisioned resources or higher reliance on teleost fishes than previously thought. Commercial bait products fed to stingrays at the Provisioning Site were not a major contributor to the diets of smooth stingrays, suggesting this activity has a low impact on their nutrition.
Publisher: American Fisheries Society
Date: 2022
Publisher: Frontiers Media SA
Date: 29-04-2021
DOI: 10.3389/FMARS.2021.641761
Abstract: The advent of new technologies and statistical analyses has provided valuable insights into chondrichthyan social behavior. It has become apparent that sharks and rays lead more complex social lives than previously believed. Heterarchy combines hierarchy and social network theory and although it is not a new concept, it is rarely applied to animal social interactions. Here, we applied heterarchy to a case study involving smooth stingrays foraging for fish scraps at boat r in Jervis Bay, NSW Australia. We took advantage of their attraction to this site to examine their social behavior during agonistic interactions over the provisioned resource. We observed a stable, relatively linear but shallow dominance hierarchy that was highly transitive dominated by a single in idual. Social network analysis revealed a non-random social network centered on the dominant in idual. Contrary to previous research, size did not predict dominance, but it was correlated with network centrality. The factors determining dominance of lower ranks were difficult to discern, which is characteristic of despotic societies. This study provides the first heterarchical assessment of stingray sociality, and suggests this species is capable of complex social behavior. Given higher dominance and centrality relate to greater access to the provisioned resource, the observed social structure likely has fitness implications.
Publisher: CSIRO Publishing
Date: 30-01-2023
DOI: 10.1071/MF22146
Abstract: Context It is common for recreational anglers to discard waste produced from filleting catches back into the water, which results in a highly spatio-temporally predictable food subsidy for wildlife to scavenge. However, the behavioural responses of these scavengers has received little attention. Aims We aimed to assess the visitation of a common mesopredatory scavenger in relation to temporal patterns in waste discarding at a boat r in south-eastern Australia. Methods Using passive acoustic telemetry, the movements of 13 adult female smooth stingrays (Bathytoshia brevicaudata) were tracked, and patterns in their acoustic detections and duration of time spent in different sections within the study area were compared. Key results Use of the study area was strongly focused around the boat r , and peaked during periods of increased provisioning activity (i.e. afternoons and weekends). Environmental variables had limited influence on visitation, suggesting that the use of the area was not likely to be linked to natural behaviours. Conclusions The observed patterns indicated that the movements of smooth stingrays were linked to waste-discard practices by recreational anglers. Implications This study has implications for the management of discard practices for recreational fishing.
Publisher: American Geophysical Union (AGU)
Date: 02-2021
DOI: 10.1029/2020WR027463
Abstract: The presence of permafrost influences the flow paths of water through Arctic landscapes and thereby has the potential to impact stream discharge and thermal regimes. Observations from 11 headwater streams in Alaska showed that July water temperatures were higher in catchments with more near‐surface permafrost. We apply a fully coupled cryohydrology model to investigate if the impact of permafrost on flow path depth could cause the same pattern in temperatures of groundwater discharging from hillslopes to streams. The model simulates surface energy and water balances, snow, and subsurface water and energy balances for two‐dimensional hillslope model cases with varying permafrost extent. We find that hillslopes with continuous permafrost have more shallow flow paths and twice as high rates of evapotranspiration, compared to hillslopes with no permafrost. For our simulated cases, 6.7% of the horizontal water flux moves through the top organic soil layers when there is continuous permafrost, while only 0.5% moves through organic layers without permafrost. The deeper flow paths in permafrost‐free simulations buffer seasonal temperature extremes, so that summer groundwater discharge temperatures are highest with continuous permafrost. Our results suggest that permafrost thawing alters groundwater flow paths and can lead to decreases in summer stream temperatures and reductions in evapotranspiration in headwater catchments. These changes are of potential importance for stream biotic components of ecosystems, however, the full impact remains unknown.
Publisher: Elsevier BV
Date: 07-2023
No related grants have been discovered for Joshua Koch.