Water abstraction impacts on flow dependent fisheries species of the Northern Territory, Australia - a synthesis of current knowledge and future research needs

Project number: 2021-114
Project Status:
Completed
Budget expenditure: $101,740.68
Principal Investigator: Kaitlyn O'Mara
Organisation: Griffith University Nathan Campus
Project start/end date: 30 Jul 2022 - 30 Jul 2023
Contact:
FRDC

Need

The tropical waters of northern Australia contain unique and diverse aquatic species that are adapted to the seasonally variable climate. Many species rely on seasonal river flows to move, forage, reproduce and fulfil critical life history stages, particularly in ephemeral rivers which become disconnected in the dry season. River flows and harvest are known to influence both freshwater and marine fish and fisheries. However, river flows have been modified in several tropical catchments by water abstraction and development of water storage infrastructure for agriculture and drinking water. Additionally, there is increasing pressure to develop new water resource infrastructure in northern Australia. A large and disparate body of literature exists that has documented the relationships between tropical fish species and the seasonal variations in river flow. Production of several commercially, recreationally, and traditionally important tropical aquatic species is linked to flow, suggesting that these may be at risk from the multiple pressures of water abstraction and harvesting, warranting the need for a synthesis of current knowledge on water abstraction impacts and identification of knowledge gaps for targeted future research.

We will address this priority task through the delivery of a stakeholder targeted synthesis of current knowledge on the impacts of water abstraction on tropical aquatic species by a team of recognised experts who have worked extensively on the flow dependence of tropical aquatic species in northern Australia. Through this synthesis, we aim to increase stakeholder understanding of water abstraction impacts on aquatic species.

Objectives

1. Determine key directives for the synthesis during initial meeting in Darwin with the NT government research advisory committee
2. Review and synthesise relevant grey and published literature
3. Identify potential risks of surface water abstraction on priority fish species and identify critical knowledge gaps and future research needs
4. Share the outcomes with project stakeholders and provide research advice

Final report

Authors: Kaitlyn O’Mara Leah Beesley Keller Kopf Michele Burford Michael Douglas Ben Stewart-Koster Mark Kennard
Final Report • 2023-12-12 • 14.77 MB
2021-114-DLD.pdf

Summary

This project synthesised information that could be used to help guide decision making around the protection of fisheries species that may be impacted by water abstraction. This review was led by Griffith University and conducted in collaboration with the University of Western Australia, Charles Darwin University, and the Northern Territory Fisheries. The synthesis of existing information on the impacts of water abstraction found substantial evidence for impacts on some species and large gaps in the research literature for others. The reviewed studies showed that the severity of predicted impacts varies between river systems and between different modes of water abstraction, as well as with different timing, magnitude, and thresholds of water take. The collective results of these studies modelling potential impacts of water abstraction warrant a precautionary approach to setting water takes, with particular emphasis on ensuring the continuation of high flow years which disproportionately support fishery biomass. It is recommended that the flow dependencies of these species be carefully considered when implementing water policies and research be conducted to fill knowledge gaps for species where little is known about their dependency on the natural flow regime.

Related research

Environment
Industry
Environment

Improving bycatch reduction strategies and escape vents in Queensland Mud Crab fisheries

Project number: 2021-119
Project Status:
Completed
Budget expenditure: $129,915.00
Principal Investigator: Julie B. Robins
Organisation: Department of Primary Industries (QLD)
Project start/end date: 30 Apr 2022 - 29 Jul 2023
Contact:
FRDC
SPECIES

Need

The proposed work directly targets the opportunity
• to benchmark bycatch reduction devices (including escape vents) and strategies currently in use in the Queensland Crab Fishery,
• to trial refined escape vents for better (i) retention of legal crabs and exclusion of non-legal crabs and fish bycatch.

Recommended refinements to the regulation of escape vents in commercial mud crab pots will be provided to Fisheries Queensland by October/November 2022 for potential inclusion in the next round of regulatory amendments to the Crab Fishery.

More appropriately specified escape vents will produce better commercial outcomes (i.e., retention of legal crabs) and better ecological outcomes (e.g. exclusion of sub-legal crabs and finfish prone to entrapment in crab pots). Reports from crabbers indicate that some of the regulated escape vents allow legal crabs to escape, whilst the small escape vent (75 x 60 mm) reportedly allows very little bycatch to escape. A quantitative study that encompasses regional variation in mud crab morphometrics (i.e., carapace depth/height ~carapace width) would provide empirical data upon which management decisions can be objectively made.

Better documentation on marine turtle entrapment in crab pots (which is currently of limited public access) and gear modification to efficiently reduce or prevent marine turtle entrapment would be of benefit to threatened and endangered marine turtle populations of Queensland (in particular loggerhead turtles) and would contribute to the development of a risk mitigation strategy for the fishery.

Objectives

1. Benchmark bycatch reduction devices and strategies currently in use in the Queensland crab fishery.
2. Trial alternate configurations and advise on potential changes to escape vent regulations achieve better commercial and ecological outcomes.
3. Collate information on marine turtle interactions with crab pots (including ghost pots) and consider pot configuration(s) that could contribute to a risk mitigation strategy for marine turtles in the Qld crab fishery.
4. Develop options for adoption of bycatch reduction devices and strategies in the recreational sector of the Qld crab fishery.

Final report

ISBN: 978-0-6456352-7-0
Authors: J.B. Robins N.J. Stratford S. Seghers and S.M. Leahy
Final Report • 2024-11-11 • 6.03 MB
2021-119-DLD.pdf

Summary

The Queensland Crab Fishery is an iconic fishery, which encompasses the harvest of mud crabs (Scylla serrata, the Giant Mud Crab, and Scylla olivacea, the Orange Mud Crab) and Blue Swimmer Crabs (Portunus armatus and Portunus pelagicus), predominately using baited crab pots of various designs. The Fishery has a limited entry commercial sector that requires a C1 symbol to catch these species of crabs, plus possession of appropriate quota to catch mud crabs on the Queensland East Coast (EC1), Queensland Gulf of Carpentaria (GC1) or Blue Swimmer Crabs anywhere in Queensland (BC1). The Fishery also has a significant recreational sector, that uses similar apparatus and does not require a licence, but does have in possession limits.
The current research investigated the performance of escape vents in crab pots targeting Giant Mud Crabs to determine if current Queensland fisheries regulations should be revised to provide better commercial outcomes (i.e., retention of legal mud crabs – male and 150 mm carapace width or greater), whilst minimising the bycatch of non-legal crabs, finfish and other bycatch species, such as water rats. The research focussed on the Giant Mud Crab as it comprises greater than 99% of the commercial harvest of mud crabs in Queensland
The ongoing issue of marine turtle interactions with crabbing apparatus, including a recent increase of stranding reports, led to the research also collating available information about these interactions to support a risk mitigation strategy for the fishery’s interaction with protected marine turtle species.
Results are to be considered by management, Fisheries Queensland and the Crab Working Group as part of the Harvest Strategy arrangements for the Queensland Crab Fishery.