Project number: 1984-023
Project Status:
Completed
Budget expenditure: $0.00
Principal Investigator: Mike Potter
Organisation: Department of Agriculture and Fisheries EcoScience Precinct
Project start/end date: 28 Dec 1986 - 31 Dec 1986
Contact:
FRDC

Objectives

1. Compare, contrast life history parameters of sand crab in sub-tropical sth Qld vs. Gulf of Carpentaria & temperate waters.
2. Assess Moreton Bay sand crab stocks
relative impact of recreational, otterboard trawl & commercial crab pot fisheries
effectiveness existing mgt strategies & alternatives

Final report

Author: M.A. Potter W.D. Sumpton
Final Report • 1986-12-31 • 1.77 MB
1984-023-DLD.pdf

Summary

Based on logbook records the sand crab commercial pot fishery in Moreton Bay is worth in the vicinity of $2 million wholesale annually. Sand crabs are also taken as an incidental by-catch by otter trawlers and in addition Moreton Bay supports a substantial recreational fishery.

Sand crabs are caught throughout the year but fishing effort is greatest from October to June. Peak catches in the pot fishery occur during March and April when daily catch rates may exceed 3 legal males per pot. Gravid females are present throughout the year but the highest proportion of egg bearing females is found in the population during August and September. Peaks in mating activity occur in autumn and spring with recruitment of juvenile crabs commencing in November. The parasitic barnacle Sacculina granifera infects 3% of all sand crabs in Moreton Bay and a previously unreported microsporidian parasite is found in 0.7% of the population.

Tagging studies show that fishing effort and mortality of sand crabs is highly variable throughout the Bay. Recapture rates for different areas vary from 1% to 65% with an overall return rate of 14%. The pattern of tag returns does not indicate any ordered directional movement of crabs either into or out of the Bay.

Male and female sand crabs exhibit differences in preferred habitat. Large males are generally more abundant in deeper water, whereas females predominate in shallower water, particularly on the top of sand banks.

Management recommendations arising from the project work include a change in the method of sand crab measurement to the width at the base of the antero-lateral spines, lowering of the existing size limit, the introduction of a bag 1 limit for recreational fishermen and an abolition of the prohibition on taking females provided that suitable management conditions can be maintained.

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