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Environment
PROJECT NUMBER • 2019-062
PROJECT STATUS:
CURRENT

Knowledge to improve the assessment and management of Giant Mud Crabs (Scylla serrata) in Queensland

Researchers from the Department of Agriculture and Fisheries (DAF) Queensland, CQUniversity (CQU) and the Department of Primary Industries (DPI) NSW Fisheries are collaborating on a Fisheries Research and Development (FRDC) co-funded research project on mud crab populations in Queensland. The...
ORGANISATION:
Department of Agriculture and Fisheries EcoScience Precinct
TAGS
Wild Catch
Tagging
Reproduction
Rac Qld
Rac Nsw
SPECIES
Mud Crabs
FLYER
•
PUBLISHED DATE: 01 Dec 2020
FRDC-DAF Mud crab flyer.pdf
FACT SHEET
•
PUBLISHED DATE: 01 Dec 2020
FRDC-DAF Mud crab factsheet.pdf
 
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Environment
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People

Understanding environmental and fisheries factors causing fluctuations in mud crab and blue swimmer crab fisheries in northern Australia to inform harvest strategies

Project number: 2017-047
Project Status:
Completed
Budget expenditure: $161,433.33
Principal Investigator: Julie B. Robins
Organisation: Department of Agriculture and Fisheries EcoScience Precinct
Project start/end date: 9 Jul 2017 - 30 Dec 2018
Contact:
FRDC
TAGS
Reproduction
Rac Qld
Rac Nt
Population Dynamics
Oceanography
SPECIES
Blue Swimmer Crab
Mud Crabs

Need

The work is needed to:
(i) critically review the available literature on environmental factors influencing crab fisheries;
(ii) update analytical relationships between catch and environmental factors to include the extreme climate events experienced in the past 10 years in the GoC, and for a broader range of environmental factors than previously considered;
(iii) expand jurisdictional stock modelling to a more biologically appropriate scale and support cross-jurisdictional collaboration;
(iv) test the ability of model results to inform management of the relative importance of fishing pressure compared to environmental factors;
(v) develop reference point concepts suitable for adaptive harvest strategies for crab fisheries in northern Australia.

The project will provide information at a broad spatial scale (i.e., GoC) for crab species with different life histories and potentially different responses to environmental factors. It will compare the declining catches of mud crabs with the anecdotally reported increasing catches of blue swimmer crabs in the GoC.

Recent increases in blue swimmer crab catches in the GoC needs to be investigated to clarify which species are present and to assess their vulnerability to fishing.

The adaptation of an existing crab population model will be a case study that potentially could be applied to the Queensland east coast and other crustacean species. The current work will assist in determining whether the NT GoC mud crab fishery warrants management intervention as a consequence of environmental factors. The recent closure of blue swimmer crab fisheries in WA highlights the potential of environmental factors to seriously impact a stock to the point where fishing needs to be removed (Johnston et al 2011).

Objectives

1. Evaluate the role of a broad range of environmental drivers on catch variation in Northern Territory and Queensland crab fisheries of the Gulf of Carpentaria.
2. Explore the relative importance of fishing pressure compared to environmentally driven variability using a population model of the GoC mud crab fishery.
3. Provide advice to support the development of harvest strategies appropriate for crab fisheries in northern Australia.

Final report

ISBN: 978-0-7345-0465-4
Authors: J.B. Robins A.R. Northrop M.A. Grubert R.C. Buckworth M. McLennan W.D. Sumpton and T. Saunders
Final Report • 2020-06-01 • 5.32 MB
2017-047-DLD.pdf

Summary

This project investigated relationships between environmental factors and harvests of crabs in the Gulf of Carpentaria (GoC), northern Australia. Desktop correlative analyses clearly indicated that recent fluctuations in the catches of Giant Mud Crabs in the GoC are most likely driven by environmental factors including river flow, rainfall, temperature, evaporation, and sea level changes. Declines in catches of Giant Mud Crabs between 2009 and 2016 in the NT and 2013 and 2016 in Qld coincided with a sequence of years with low rainfall, high temperatures and below average mean sea levels. The GoC may be atypical in the effects of environmental factors on populations of Giant Mud Crabs. The western and southern GoC has an east-west layout of the coastline, such that mobile organisms cannot retreat southwards to avoid heat events. The GoC has a mostly diurnal tidal regime resulting in the exposure of inter-tidal areas to the extremes of heat in summer and cold in winter. Rainfall and associated flooding in the catchments of the GoC occurs during a relatively short wet season and the reliability of annual rainfall and flooding is relatively low. We suggest that the GoC is an area where Giant Mud Crabs and their associated fisheries may be at high vulnerability to climate events, more so in the western and south-eastern regions (e.g. Roper and McArthur) than in the eastern and northern regions (e.g. Pormpuraaw and Weipa-Mapoon). During extreme climate events, environmental factors may have been relatively more important than fishing pressure.

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