Cray, crayfish, rock lobster, kōura: this prized crustacean goes by many names. Jasus edwardsii is a rock lobster species inhabiting shallow reefs around Aotearoa New Zealand’s coasts as well as southern Australia. It is reported to be a relatively slow-growing and long-lived species,[1] though some suggest that the science in Aotearoa New Zealand is not fully settled.[2] It is one of our most lucrative fisheries, with exports worth around $300 million in 2019.[3] It is highly valued by Māori and recreational fishers. Rock lobsters are captured live in baited pots, or by divers, and the peak season is between June and November.
In Aotearoa New Zealand, the rock lobster fishery was first introduced into the QMS in 1990 and is divided into ten management stocks (see map on right, although CRA 10 is nominal and is not commercially fished). Although most of the plenary stocks are classified as sustainable and none of these stocks are categorised as ‘collapsed’ by Fisheries New Zealand, CRA2, covering Te Moana-a-Toitehuatahi the Bay of Plenty north to Tīkapa Moana the Hauraki Gulf, is ‘virtually certain’ to be experiencing overfishing (table below) and CRA4 in the Te Matau-a-Māui Hawke’s Bay/Wairarapa region is ‘likely’ to be experiencing overfishing.
Homing in on the CRA2 stock, we can see an example of divergence between the industry, regulator and independent researchers in estimation of stock performance. The stock was last assessed by Fisheries New Zealand in 2017 – brought forward a year earlier than scheduled as iwi, recreational fishers, and commercial fishers all expressed concern about the stock. The stock assessment used the ‘lobster stock dynamics’ model and was overseen by the Rock Lobster Fishery Assessment Working Group. The assessment determined that CRA2 was ‘likely’ below the soft limit (20% of unfished spawning stock biomass), but ‘very unlikely’ to be below the hard limit (10% of unfished spawning stock biomass).[4]
Homing in on the CRA2 stock, we can see an example of divergence between the industry, regulator and independent researchers in estimation of stock performance.
Rock lobster (Jasus edwardsii). Image credit: lcolmer/iNaturalist (CC BY-NC 4.0).
Map showing the different management stocks for rock lobster. Image credit: NIWA.
Status of Rock Lobster fishery by management stock as reported by Fisheries New Zealand.
| Plenary stock | At or above target levels? | Overfishing? | Below the hard limit? | Below the soft limit? | Last assessment date | Corrective management action |
|---|---|---|---|---|---|---|
| CRA1 Northland | Unlikely | About as likely as not | Very unlikely | Very unlikely | 2019 | TAC reduction currently being considered. |
| CRA2 Bay of Plenty | Exceptionally unlikely | Virtually certain | Very unlikely | Likely | 2017 | Significant TACC and recreational allowance reductions in 2018. Further recreational measures currently being considered. |
| CRA3 Gisborne | About as likely as not | About as likely as not | Exceptionally unlikely | Exceptionally unlikely | 2019 | - |
| CRA4 Hawke's Bay-Wairarapa | About as likely as not | Likely | Exceptionally unlikely | Exceptionally unlikely | 2019 | TAC reduced in 2017. |
| CRA5 Marlborough-Canterbury | Virtually certain | Very unlikely | Exceptionally unlikely | Exceptionally unlikely | 2019 | - |
| CRA6 Chatham Islands | Unlikely | Unknown | Very unlikely | Unlikely | 2018 | - |
| CRA7 Otago | Very likely | Very unlikely | Unlikely | Unlikely | 2019 | - |
| CRA8 Southern | Virtually certain | Very unlikely | Exceptionally unlikely | Exceptionally unlikely | 2019 | - |
| CRA9 Westland-Taranaki | Unknown | Unknown | Unknown | Unknown | 2015 | - |
| PHC1 | Unknown | Unknown | Unknown | Unknown | - | -[5] |
As a result of the assessment, new catch limits were set from 1 April 2018: a TACC of 80 tonnes, and a recreational allowance of 34 tonnes. From 1 July 2020, the recreational daily bag limit was dropped from six lobsters to three. These measures are part of a multi-stage plan attempting to rebuild the stock. Fisheries New Zealand has proposed that a review of the CRA2 TAC, allowances, TACC, and other management controls will be undertaken at the time of the next CRA2 stock assessment, which is scheduled for 2021.[6]
Others describe the CRA2 stock decline in more definitive terms: that the rock lobster is ‘functionally extinct’ within Tīkapa Moana the Hauraki Gulf.[7] The New Zealand Marine Sciences Society submitted fishery-independent analysis to the CRA2 consultation undertaken by Fisheries New Zealand in 2018 on recreational catch, outlining results from monitoring research of rock lobster abundance inside and outside marine reserves within CRA2, using the reserves as ‘unfished’ reference points of what natural biomass looks like (though some state that marine reserves are not representative of habitat in the wider QMS). At Leigh and Tāwharanui north of Tāmaki Makaurau Auckland in Tīkapa Moana the Hauraki Gulf, biomass of legal-sized lobsters outside local marine reserves was 2-3% of that inside the reserves.[8] At Hahei off the Coromandel, legal-sized lobster biomass was around 7% of the biomass in the local marine reserve. These small protected areas were cited as likely to underestimate natural ‘unfished’ abundance (see ‘Original biomass’), because the rock lobster populations inside the reserves have been steadily declining for the past 10 years, consistent with intense fishing pressure on the edges. These numbers suggest that the CRA2 stock, at least in Tīkapa Moana the Hauraki Gulf and Te Tara-o-te-Ika a Māui Coromandel parts of CRA2, may be well below the hard limit that would force a fishery closure. Part of the discrepancy is due to contested views of the biomass that is being described and how it has been calculated. For commercial fisheries where there is a significant recreational catch, stock assessments can be more uncertain due to the very limited information about the size of recreational catches.
Part of the discrepancy is due to contested views of the biomass that is being described and how it has been calculated. For commercial fisheries where there is a significant recreational catch, stock assessments can be more uncertain due to the very limited information about the size of recreational catches.
Rock lobster larva. Image credit: Jo Virens/iNaturalist (CC BY-NC 4.0).
Rock lobsters play an important role in rocky reef ecosystems: they are predators of other invertebrates such as kina. When rock lobsters are removed from the ecosystem, this can result in a trophic cascade.[9, 10] Kina numbers boom, and kina eat swathes of seaweed and other macroalgae. Diverse seaweed assemblages are a major primary productivity source and provide habitat for other marine organisms, so their removal has flow-on effects for a range of other species. This trophic cascade is discussed in the case study ‘The Noises vs Cape Rodney-Okakari Point Marine Reserve’.
Modelling of invertebrate fishing impacts (specifically for the south coast of Wellington, in CRA4) revealed that the ecosystem effects of harvesting lobster were greater than harvesting pāua or kina.[11] The analysis found that current rates of rock lobster exploitation exceed rates needed for MSY (see ‘Maximum sustainable yield’).[11] Reducing exploitation would increase target captures, raise CPUE, and reduce ecosystem impacts.
Another rock lobster stock of interest is CRA8, which extends around the southern and western coasts of the South Island and includes the subantarctic islands. Over the 1990s, the industry operating in the CRA8 area began to recognise that the fishery was in trouble. Fishers who had joined forces as the Southern Rock Lobster Research and Development Committee earlier in the 90s became the CRA8 Management Committee in 1996, and advocated for a management strategy to reverse the decline. This is considered a success story, with biomass increasing since around 2000 and now holding steady at more than 40% of the unfished level. This example shows that with good management, stocks can be improved, and the management strategy used in funding setting of annual catch limits could potentially be usefully deployed in other fisheries. However, wider questions remain around the functioning of these ecosystems and long-term impacts.
The New Zealand Rock Lobster Industry have pointed out that since these assessments management action was taken on 1 April 2020 to reduce catch in CRA1 and CRA2 is rebuilding. The next assessment will ascertain the impact of these actions.
References and footnotes
[1] National Rock Lobster Management Group (2018) Review of Rock Lobster Sustainability Measures for 1 April 2018: Final advice paper, MPI Information Paper No: 2018/02, p. 96.
[2] Input from New Zealand Rock Lobster Industry Council Ltd.
[3] Seafood New Zealand (2020) Economic review of the seafood industry December 2019, Seafood New Zealand, 28(2), pp. 42-43.
[4] Webber, D. N. et al. (2018) The 2017 stock assessment and management procedure development for red rock lobsters (Jasus edwardsii) in CRA 2.
[5] Input from the New Zealand Rock Lobster Industry Council: In 2020, industry funded a characterisation and the first stock assessment for packhorse rock lobster (PHC 1) though this does not year appear to be publicly available. Industry reports that the assessment suggests that following a period in the 60s and 70s when the stock was overfished, the stock has rebuilt strongly to nearly unfished levels and consideration is currently being given to catch limit increases.
[6] National Rock Lobster Management Group (2019) Review of Rock Lobster Sustainability Measures for 2020/21. Discussion Document No: 2019/20.
[7] Hauraki Gulf Forum (2020) State of our Gulf 2020. Hauraki Gulf/Tīkapa Moana/Te Moananui-ā-Toi State of the Environment Report 2020.
[8] LaScala-Gruenewald, D. E. et al. (In Press) Small marine reserves do not provide a safeguard against overfishing, Conservation Science and Practice.
[9] Shears, N. and Babcock, R. (2003) Continuing trophic cascade effects after 25 years of no-take marine reserve protection, Marine Ecology Progress Series, 246, pp. 1–16.
[10] Input from NZ Rock Lobster Industry Council Ltd: Not all habitats are susceptible to kina barren in the absence of rock lobster. The trophic cascade hypothesis is disputed by the National Rock Lobster Management Group, which has provided advice to the Minister stating, “This hypothesis is controversial and the literature equivocal…sea urchins populations are affected by factors other than predation, such as diseases and temperature”.
[11] Eddy, T. D. et al. (2015) Trade-offs between invertebrate fisheries catches and ecosystem impacts in coastal New Zealand, ICES Journal of Marine Science, 72(5), pp. 1380–1388.