Orange roughy stock health

Orange roughy are slow-moving and form large, predictable aggregations, which makes them easy to capture. They tend to aggregate around underwater topographical features (UTFs), which include seamounts, knolls, ridges and canyons. These are home to diverse benthic flora and fauna, which is damaged by the trawl gear used to harvest orange roughy (see ‘Habitat’ section). Although genetic studies suggest that there is just one worldwide population of orange roughy,[4, 5] it is possible to deplete the local population at a specific UTF. Individuals migrate between specific feeding and spawning sites.

In Aotearoa New Zealand, commercial fishing of orange roughy began in 1979.[6] At the time, their low productivity and long lifespan were not known, with estimates suggesting a maximum age of about 30 years. Early stock assessments, based on trawl survey biomass estimates, greatly overestimated the unfished biomass B₀ (a generally contested number for many species (see ‘Original biomass’ section). The species’ inherent susceptibility to overfishing, combined with inadequate data and knowledge, led to a period of unsustainable overfishing.

Between 1983 and 1990, around 50,000 tonnes were harvested each year – but reported catch was likely underestimated (by as much as 50%) due to catch being lost at sea and to discrepancies in converting fillet weight to whole fish.[2] Reported catch peaked in 1989 at 57,000 tonnes.[6] By 1994, the harvest had dropped to less than 20,000 tonnes. By the end of the 1990s, three of Aotearoa New Zealand’s eight orange roughy fisheries had collapsed and were closed. TAC was reduced substantially for the fisheries that remained open.

Since the late 80s, evidence for the long lifespan of orange roughy had emerged and mounted. Fish age can be determined via a range of methods, including counting circuli on scales, counting growth rings in otoliths (ear bones), radiometric dating of otoliths, and lead-radium dating. By 1988, trawl surveys undertaken showed the species was long-lived and slow growing with low productivity.[7] A subsequent review in 1999 also concluded that orange roughy are indeed long-lived and slow growing.[8] Since then, one individual sampled 1,500 km east of Wellington was estimated to be 230-245 years old. Further documentation of the early history of the science and management of the Chatham Rise orange roughy fishery can be found in Sissenwine and Mace.[9]

In the last two decades, innovative technologies and better research methods have improved the management and sustainability of the orange roughy fisheries (alongside the significant reduction in catch). The stock is divided into eight QMAs, with monitoring every four years. Stock assessments incorporate several data sources, including fisheries data, life-history characteristics, and tagging data. Acoustic and video surveys and better ageing techniques enable more accurate estimates of population size and demographics. In turn, this informs management decisions to support the recovery of orange roughy stocks.

Now, some orange roughy stocks have rebuilt. In 2020, the TAC was just under 11,000 tonnes, and a commercial catch of 8,627 tonnes was reported across the eight QMAs. Most assessed stocks sit around the management target level – between 30-50% of B₀ – which aims to balance sustainability and use. In 2016, three orange roughy fisheries in Aotearoa New Zealand achieved sustainability certification from the MSC (see case study: The Marine Stewardship Council).

However, there are currently two stocks of orange roughy that are assessed by Fisheries New Zealand as experiencing overfishing. A TACC reduction was implemented in 2014 for the fishery on the mid-east coast of the North and South Islands. The other overfished stock, on the west coast of the South Island (ORH7B), has effectively been closed, with a TACC of one tonne. These reductions in TACC aim to allow the stocks to rebuild. The orange roughy story is a cautionary tale that highlights the need to use the best possible data to inform stock assessment, the importance of reassessing assumptions as new information is presented, and the need to build uncertainty into our management decisions.