Western Rock Octopus (2020)
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The Western Rock Octopus is endemic to the temperate waters of WA from Shark Bay to Esperance. The species is captured in specialised traps, and the stock is classified as sustainable.
Photo, Anthony Hart, Department of Primary Industries and Regional Development, Western Australia
Stock Status Overview
|Western Australia||Western Australia||Sustainable||
Octopus djinda (Subfamily Octopodinae), or the Western Rock Octopus, is endemic to the temperate waters of Western Australia from Shark Bay to Esperance. It is closely related to the cosmopolitan Octopus vulgaris species complex, and to Octopus tetricus on the east coast of Australia and New Zealand, but has been conclusively identified as a separate species through genetic and morphometric studies [Guzik et al. 2005, Amor et al. 2014],
Harvest of Western Rock Octopus in Western Australia is managed by a formal harvest strategy, as defined in the Octopus Resource of Western Australia Harvest Strategy 2018–22 [DPIRD 2018]. The main index of abundance is standardised catch per unit effort (CPUE) based on the catch rate of octopus from specialised traps [Hart et al. 2019]. The standardised catch per unit effort (CPUE) in the Western Rock Octopus resource in 2020 was 0.7, which was 45 per cent above the target of 0.48. The units of CPUE are kg/trap. Western Rock Octopus was subject to a recent comprehensive resource assessment which addressed biology, fishing efficiency and stock abundance and distribution [Hart et al. 2018]. The overall conclusion was that the stock is highly productive, with an average maximum age of 1.5 years, as well as abundant and widely distributed along the west and south Coast of Western Australia. The estimated area of fished habitat in 2019 was 1500 km2 and this was a minor percentage (7 per cent) of the total estimated habitat area on the West Coast of 20 073 km2 [Hart et al. 2019]. The above evidence indicates that the biomass of this stock is unlikely to be depleted and that recruitment is unlikely to be impaired. The above evidence also indicates that the current level of fishing mortality is unlikely to cause the stock to become recruitment impaired.
Based on the evidence provided above, the Western Australian Western Rock Octopus management unit is classified as a sustainable stock.
The biological characteristics of Western Rock Octopus include rapid growth, short lifespan and early maturity [Leporati and Hart 2015, Leporati et al. 2015]. This highly productive species has a relatively low vulnerability to fishing. This species spawns year-round, has sperm storage, and males are far more likely to enter the octopus traps. Males and females are usually a similar size, and maximum weight recorded is a 4.5 kg female [Leporati et al. 2015].
|Species||Longevity / Maximum Size||Maturity (50 per cent)|
|Western Rock Octopus||
Maximum age 1.5 years. maximum recorded weight 4.5 kg
Males: mature at 6 months.
Females: mature at 12 months
|Hand Line, Hand Reel or Powered Reels|
|Octopus Traps And Pots|
|Traps and Pots|
|Pots and Traps|
|Charter||< 0.5 t|
|Recreational||3 t (2017–18)|
- Amor, M. D., Norman, M. D., Cameron, H. E., and Strugnell, J. M. 2014. Allopatric speciation within a cryptic species complex of Australasian octopuses. PLoS One, 9: e98982–13.
- Department of Primary Industries and Regional Development (DPIRD), Western Australia (2018). Octopus resource of Western Australia harvest strategy 2018–2022. Fisheries Management Paper No. 286. Department of Primary Industries and Regional Development, Western Australia, Perth. 31pp.
- Hart, A. M., Murphy, D. M., Harry, A. V. and Fisher, E. A. (2018). Western Australian Marine Stewardship Council Report Series No. 14: Resource Assessment Report Western Australian Octopus Resource. Department of Primary Industries and Regional Development, Western Australia. 114pp.
- Hart, A. M., Murphy, D., Hesp, S. A., & Leporati, S. (2019). Biomass estimates and harvest strategies for the Western Australian Octopus aff. tetricus fishery. ICES Journal of Marine Science, 76(7), 2205-2217.
- Leporati, SC, Hart AM (2015). Stylet weight as a proxy for age in a merobenthic octopus population. Fisheries Research. 161: 235-243
- Leporati, SC, Hart AM, Larsen R, Franken LE, De Graaf MD (2015). Octopus life history relative to age, in a multi-geared developmental fishery. Fisheries Research 165: 28-41
- Molecular phylogeny of the benthic shallow-water octopuses (Cephalopoda: Octopodinae). Molecular Phylogenetics & Evolution 37, 235–248.
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