Potting is a fishing technique that generally uses a baited pot or cage – creatures are attracted to the pot and can easily enter but cannot leave as easily. Potting avoids many of the direct environmental harms of bottom trawling,[1] and has the potential to be more targeted and less damaging to catch.[2] It can also provide live seafood, which if unsuitable can be returned to the wild, or sold into premium live seafood markets.
Tāruke (crayfish traps) were used traditionally by Māori to catch crayfish, by using a mix of natural materials such as mānuka stems, supplejack vine, and flax. Modernised potting is used extensively in the rock lobster industry in Aotearoa New Zealand. The fishery has comparatively low rates of bycatch – most frequently octopuses/wheke[3] (which prey on rock lobsters) and conger eels/ngōiro.[4–7] Interactions with seabirds and mammals are also relatively low, though pot lines can create an entanglement risk.[8] Rock lobster are a high value product and most are unharmed on capture (see case study: Mixed messages: Are we overfishing our rock lobsters?).
Taruke kōura (crayfish trap), maker unknown. Purchased date unknown. Taonga Māori collection, Te Papa Tongarewa Museum of New Zealand (ME003080).
New Zealand scampi. Image credit: Rob Major.
Given that potting can present many advantages to bottom trawling, there’s been interest in Aotearoa New Zealand about whether the technique could be applied to other fisheries. New Zealand scampi is a type of lobster that lives in the offshore areas of Aotearoa New Zealand at about 200-600 m depth. Scampi are mostly harvested by bottom trawling, which can cause damage to the seabed as well as presenting issues such as bycatch, including of non-target fish species, seabirds, and marine mammals. Scampi has the highest bycatch rate of any New Zealand fishery, with scampi making up less than 20% of scampi-targeted trawls.[9, 10] This means that a large proportion of catch is discarded – thousands of tonnes a year. There are currently no species from this genus that are harvested using potting methods.[11]
Overseas, pots are used extensively to catch another type of scampi known as Norway lobsters.[12] While Norway lobsters have many small differences to New Zealand scampi and are part of a different genus, the similarities between the species provided inspiration for the possibility of a commercially viable potting operation in Aotearoa New Zealand inspired by traditional Māori potting methods.
The Waikawa Fishing Company is owned and operated by a Māori family that has been fishing the northern most part of the South Island for many generations.[13] As the company became more aware of some of the negative environmental impacts of their operation, they saw that it did not align with their responsibilities as kaitiaki. This responsibility drove their desire to innovate, experiment and learn.
Waikawa Fishing Company and Cawthron Institute worked together to develop a research programme along with Zebra-tech Ltd and the University of Auckland. The result was a research programme ‘Ka Hao te Rangatahi: Revolutionary Potting Technologies and Aquaculture for Scampi’. The programme aims to link Māori innovation with leading edge research, design and engineering. Part of the programme focuses on how to employ innovative Māori-based potting technologies. This change in technology would herald the first major advance in this fishery in thirty years. The potting technologies developed during this research were based on designs used overseas, using local ecological knowledge and application of mātauranga approaches to modify a design suited to the Aotearoa New Zealand fishery. Research continues to overcome the challenges to potting local scampi and has emphasised the need to understand more about the species.
The success of potting for a fishery depends heavily on understanding the biology and behaviour of a species. For scampi, the method of potting can only be successful when scampi are foraging (when they can be found outside of their burrows[14]). It can takes years of research to understand behaviours, physical design, baiting and other factors that allow us to achieve a successful and less harmful alternative to traditional technologies[15] but the benefits are enormous.
While work on scampi continues, the potting method was reconfirmed as a viable harvesting method for the large bottom-dwelling fish ling. Ling, an increasingly valuable commercial species (see case study: Trade limitations hindering the sale of a high value fish by-product), would readily enter pots without need for specific attractants. Ling are high-level predators which means that once they are inside the pots, smaller fish (that would be prey of ling) do not enter the pots, or if they do they are eaten. By using this method for ling, bycatch has reportedly reduced to less than 1% by weight, with no seabird or mammal bycatch.[16] In addition to this there is reportedly little to no seabed damage and a large reduction in fuel use.[16] The design means that the fish caught are not crushed and the lack of bycatch means there is no longer a need to sort through the catch when landed. Further studies to understand the ecosystem impacts of potting for ling instead of trawling would be beneficial.
Waikawa Fishing Company has now converted all ling harvesting to the potting method. This is a success story where an alternative that causes less environmental and ecological harm can be commercially viable.
It also emphasises the importance of understanding the characteristics of different species. The success with ling, a bottom-dwelling and predatory species, provides insight into other fisheries in which a potting approach could be successful, but as learned for scampi, success is species-dependent.
Success is species-dependent.
Gurnard and rig were suggested by the researchers involved as two potential fisheries where potting could be an alternative to traditional harvesting methods (trawl and set netting) due to their similar behaviour. The utility of the potting method is especially relevant when considering the recent introduction of restrictions to catch methods in habitat areas deemed critical to Māui and Hector’s dolphins and other taonga species. Research and trials in this area could provide the first steps towards wider use of potting technologies, and potentially identify other fisheries where potting could be applied.
Ling caught in pots. Image credit: Waikawa Fishing Company.
References and footnotes
[1] Fisheries New Zealand (2017) Rock lobster (CRA and PHC), Fisheries Assessment Plenary, pp. 231–337.
[2] Chambers, B. (2012) Enhancing catch value from matauranga Maori-based fish potting methodologies. A thesis submitted for the degree of Master of Science at the Lincoln University, Canterbury, New Zealand.
[3] Forty-two species in the order Octopoda.
[4] Conger verreauxi and Conger wilsoni.
[5] Breen, P. (2005) Managing the effects of fishing on the environment: What does it mean for the rock lobster (Jasus edwardsii) fishery?, New Zealand Fisheries Assessment Report 2005/53.
[6] Kane, P. L. (2015) Investigating the catchability of the New Zealand rock lobster (Jasus edwardsii), with aspects to fisheries ecology. A thesis submitted for the degree of Master of Science in Marine Science, The University of Auckland, Auckland, New Zealand.
[7] National Rock Lobster Management Group (2019) Review of Rock Lobster Sustainability Measures for 2020/21. Discussion Document No: 2019/20.
[8] Abraham, E. and Richard, Y. (2020) Estimated capture of seabirds in New Zealand trawl and longline fisheries, to 2017–18. New Zealand Aquatic Environment and Biodiversity Report No. 249.
[9] Ogilvie, S. et al. (2016) Ka Hao Te Rangatahi: New directions for the New Zealand scampi fishery?, p. 17.
[10] Ministry for Primary Industries (2020) Aquatic environment and biodiversity annual review 2019-20, p. 724.
[11] Major, R. N. et al. (2017) Laboratory investigations of the foraging behaviour of New Zealand scampi, Journal of Experimental Marine Biology and Ecology, 497, pp. 99–106.
[12] Nephrops norvegicus.
[13] Ogilvie, S. et al. (2018) Mātauranga Māori driving innovation in the New Zealand scampi fishery, New Zealand Journal of Marine and Freshwater Research, 52(4), pp. 590–602.
[14] Major, R. and Jeffs, A. (2017) Orientation and food search behaviour of a deep sea lobster in turbulent versus laminar odour plumes, Helgoland Marine Research, 71(9), pp. 14.
[15] Major, R. N. et al. (2017) Factors affecting bycatch in a developing New Zealand scampi potting fishery, Fisheries Research, 186, pp. 55–64.
[16] Ogilvie, S. et al. (2019) Investigating mātauranga Māori approaches to enhancing the environmental performance of commercial NZ fisheries, New Zealand Marine Sciences Society Conference.