Patrick Cordue, the stock assessment author of the 2014 New Zealand orange roughy assessments, reflects on how the science and management of New Zealand’s orange roughy fisheries have advanced in the last two decades.
New Zealand orange roughy fisheries have been transformed over the past two decades from often quoted “unstainable fisheries” to key fisheries that have rebuilt and are sustainably managed. These fisheries now meet the high standards required by Marine Stewardship Council (MSC) certification. This is no small feat. It is due to the major progress that has been made in the science and management of these fisheries
The three largest New Zealand fisheries, two on the Chatham Rise (to the east of New Zealand) and one on the Challenger Plateau (to the west), are the first orange roughy fisheries in the world to achieve MSC certification – the gold standard for sustainable seafood.
New Zealand’s Quota Management System (QMS) is the foundation on which these fisheries have been rebuilt. The QMS, introduced in 1986, is based on Individual Transferrable Quotas (ITQ) and Total Allowable Commercial Catches (TACCs). The QMS enables the direct control of harvest levels based on scientific stock assessments. Both government and the fishing industry have strong incentives to ensure that fisheries are managed sustainably. The quota owners have a direct commercial incentive to maintain the value of their quota through the long term sustainability of the fisheries. They have invested millions in fisheries research and innovative acoustic survey technologies to ensure that top quality science is used to underpin management decisions.
A journey of discovery
New Zealand’s orange roughy fisheries were established from the late 1970s through to the 1980s when little was known about orange roughy growth and reproduction. The optimism at the time that the large orange roughy aggregations represented a vast new resource was based on the usual productivity assumptions for inshore and middle depth species, which are typically very productive and can support high fishing intensities.
Not until the late 1980s, when juvenile orange roughy were found in some numbers on the Chatham Rise, was it realised that orange roughy were very long lived and slow growing. With this discovery, it became clear that orange roughy populations were much less productive than had been assumed and that, consequently, the catch limits had been set too high. As a result, most orange roughy stocks were overfished. It is now known that orange roughy can live to over 100 years, and may not spawn until they are 30 years, or older.
Further advances were made in the 1990s with improvements in the stock assessment models, but the lack of reliable age and abundance data limited the usefulness of these models for management. Trawl surveys at the time on the Chatham Rise became unreliable because of the patchy nature of the spawning aggregations. Biomass indices based on commercial catch rates (i.e. catch per unit effort indices, CPUE) were used in some orange roughy assessments but these had their own drawbacks. It later became clear that such indices were at best only indexing local sub-populations rather than the biomass from the whole stock.
Promising techniques lead to accurate estimates
Acoustic surveys of orange roughy were first used in the mid 1980s. The technique was seen as promising then but was still not delivering usable results more than a decade later. The problem was trying to get an accurate estimate of the target strength of orange roughy (the proportion of acoustic energy that an individual fish reflects). This was not adequately resolved until 2012 with the use of a combined acoustic and optical system that could acoustically “ping” on individual fish at the same time as photographing them to identify the species. This enabled the target strength to be determined which allowed the acoustic backscatter measured during surveys to be much more accurately converted into biomass estimates.
The final obstacle was the ageing of orange roughy, which had been providing inconsistent results. With no age data available the stock assessment models were too simplistic to be considered reliable and orange roughy stock assessment using models was discontinued in New Zealand in 2008. However, the ageing of orange roughy was revisited and by 2009 a new protocol that gave more consistent resuts had been developed and fully tested.
Into the light
A successful return to full model-based stock assessment occurred in 2013 when Innovative Solutions Ltd (ISL) was contracted by the Ministry for Primary Industries (MPI) to assess the Mid East Coast orange roughy stock. This success led to four orange roughy stocks being assessed by ISL in 2014.
These assessments represent a new approach. The focus is very much on the acoustic surveys as relative but “informed” biomass indices. Ancillary information, on target strength and on the proportion of spawning biomass being surveyed, is used to inform the model about the true scale of the spawning population (as seen through the acoustic surveys). Biomass indices produced from the analysis of catch and effort data are no longer used. Age frequencies, developed using the new reading protocol, are used in these assessments to provide vital information on recruitment patterns. The threshold of accepting data into the models has been raised with only the most defendable data now being accepted for use in orange roughy assessments.
The 2014 assessments were developed in conjunction with MPI’s Deepwater Fisheries Assessment Working Group (DFAWG). The DWFAWG includes experienced scientists from research providers as well as MPI, industry, and NGOs. MPI’s working group process is an open scientific forum that peer-reviews all research before it can be accepted by MPI fisheries managers and used to inform management decisions. The orange roughy assessments were rigourously reviewed, debated and modified during a series of meetings from late 2013 through early 2014. The final assessments were further reviewed at the May 2014 Plenary meeting before being accepted for use in providing management advice.
A major milestone
The acceptance of the four 2014 orange roughy assessments by MPI represented a major milestone for New Zealand’s orange roughy fisheries. The successful assessments were only made possible because of the decades of investment by the government and by the seafood industry (into orange roughy acoustics in particular).
The four stock assessments were used to develop a robust harvest strategy for orange roughy. The largest uncertainty for orange roughy is the level of recruitment that can be expected to enter these fisheries over the next 20 years as cohorts spawned from relatively low stock sizes reach maturity. The harvest strategy is designed to adapt to changes in recruitment by altering the catch limits accordingly.
Gaining MSC certification is a proud moment. This major milestone could not have been reached without the strong partnerships and collaboration between scientists, the fishing industry, and government.