Fine-scale variability in catch and growth rates of western rock lobsters (Panulirus cygnus) show heterogeneous life-history parameters

Authors

A Miller, University of Western Australia
Jason How, Department of Primary Industries and Regional Development, Western AustraliaFollow
Simon de Lestang, Department of Primary Industries and Regional Development, Western AustraliaFollow
Brooke A. Gibbons, The University of Western Australia
E Lester, University of Western Australia
M Navarro, The University of Western Australia
J Fitzhardinge, Southerly Designs
Tim J. Langlois, University of Western AustraliaFollow

Document Type

Article

Publication Date

2-8-2023

Journal Title

Marine and Freshwater Research

ISSN

Print: 1323-1650 Electronic: 1448-6059

Keywords

catchability, commercial fishing, fine-scale variability, fisheries ecology, fishery management, mark–recapture, trap fishery, western rock lobster

Disciplines

Aquaculture and Fisheries

Abstract

Context: The western rock lobster fishery is recognised to be conservatively managed, with breeding stock levels estimated to be at record levels over the past decade. Despite this, anecdotal reports from commercial fishers identified an area of unexpectedly low catches in the centre of the fishery and lobsters’ biogeographic distribution.

Aim: To confirm the presence of this suspected ‘low-catch’ zone and examine the variability in catch and growth rates of lobsters if identified.

Methods: This study conducted an intensive mark–recapture survey over 8 months to explore catch rate, density, movement and growth rates across this ‘low-catch’ zone and three comparable locations.

Key results: In total, 9318 lobsters were caught and 7565 individuals were tagged during the study. Consistently low catch rates of under-sized lobsters were observed in the ‘low-catch’ zone, with catch rates increasing with distance from the zone. By contrast, similar catch rates of legal-sized lobsters were observed across all locations.

Conclusions: The study confirmed low catch rates, for under-sized lobsters, within an area of perceived low catch rates within the centre of the fishery. The lack of difference found in legal-sized catch rates among locations is likely to be due to the low fishing pressure in the ‘low-catch’ zone, resulting from hyperstability of fishers adapting to the historical perceived low catch rate. Modelled data demonstrated the ‘low-catch’ zone to be associated with faster growth rates and high fine-scale migration, indicating a potential release from density-dependent processes.

Implications: We anticipate that these results will be a useful starting point for future research into the mechanisms responsible for the unexpectedly low catch of sublegal lobsters within the ‘low-catch’ zone and the implications it may have on the wider population, both regionally and across the species distribution.

Recommended Citation

Miller A., de Lestang S., How J., Gibbons B., Lester E., Navarro M., Fitzhardinge J., Brooker M., Langlois T. (2023) Fine-scale variability in catch and growth rates of western rock lobsters (Panulirus cygnus) show heterogeneous life-history parameters. Marine and Freshwater Research 74, 335-346. https://doi.org/10.1071/MF22084