Inconsistencies have been detected the way that this stocks are assessed, with underestimated stock size based on Catch per Unit Effort (CPUE) biomass indices. Last stock assessment was performed in 2003 using the Stock Assessment program CASAL to estimate virgin biomass (B0) and current biomass and based on Bayesian estimation with several assumptions defined in MPI (2012). The base case model included CPUE indices and the alternative case comprised egg survey and CPUE indices (MPI, 2014a).
The 2006 update of the assessment was considered as unreliable and CPUE indices used considered as inadequate. As no new data on abundance is available, no new stock assessment could be performed (MPI, 2014a).
Stock assessments are conducted by independent researchers contracted by the Ministry for Primary Industries (MPI) and the results are peer reviewed by the Deepwater Fisheries Assessment Working Group (DFAWG) which is composed by scientists of the National Institute of Water and Atmospheric Research (NIWA), the Ministry and the industry. The DFAWG, under MPI, evaluates the state of the fisheries and stocks and analyze management scenarios, not being responsible by management recommendations or decisions which are taken by the MPI. A final decision is discussed in a multi-stakeholder meeting. Catch limits at 200 tons, in place since 1999/2000, are considered to be sustainable and the stock to be rebuilding (MPI, 2014a,b).
A biomass target reference point is adopted, BMSY, at 30% of B0. However BMSY for orange roughy stocks was reassessed in 2014 at 26% of B0 (Cordue, 2014, DWG, 2014). Other biological reference points are set:
- Soft limit is a “biomass level below which a stock is deemed to be “overfished” or depleted and needs to be actively rebuilt”, is 20% of B0 and considered as the limit reference point (Blim);
- Hard limit is a “biomass level below which a stock is deemed to be “collapsed” where fishery closures should be considered in order to rebuild a stock at the fastest possible rate”, is 10% of B0 (MPI, 2012).
But the level of virgin biomass (B0) is not currently known so absolute levels of reference points, although theoretically set, cannot be determined. In addition, a MSC pre-assessment cautioned against the 30-40% of B0 target in place for other orange roughy stocks, given the low productivity of the species (Punt et al., 2013).
Current abundance or fishing mortality estimates are not available. North East Cape stock represented 26% of catches (of QMA 2A) in 2012/2013 with 190 tons (MPI, 2014a).
Catches were higher during 1994/1995 and 1999/2000 (above 1.500 tons; more than 50% of catches for the whole ORH 2A), decreased greatly in result of TAC reduction and maintained at around 170 – 271 tons since 2001/2002. Last estimate, from 2003, situated the stock below the target, at 24% of B0, around 5,100 tons. Fishing mortality (F) was decreasing in result of catch limits reduction since 1999/2000, and considered to be stable (MoF, 2011).