Based on allozyme studies, the Mid-East Coast (MEC) stock comprises the Quota Management Areas (QMA) ORH 2A South, 2B (Wairarapa) and 3A (Kaikoura) that, since 1994/95, is separately managed from the East Cape stock that includes QMA ORH 2A North (MPI, 2013a).
Combined spawning biomass (SSB) estimate from an acoustic survey (2013); a trawl-survey time series of relative biomass indices (1992–1994, 2010) with associated length frequencies (1992, 1994), age frequencies and estimates of proportion spawning at age (1993, 2010); length and age frequencies collected from the commercial fisheries, including four spawning-season age frequencies (1989-1991, 2010) were fitted in an Age-structured CASAL model with Bayesian estimation (MPI, 2014a).
Input data are considered of “high quality”; “low” and “medium” quality data (e.g. catch per unit effort index) were not used. Besides, the assessment meets the New Zealand’s Science and Research Information Standard for New Zealand Fisheries in place since 2011 (MPI, 2014b). Natural mortality (M) was assumed as a constant at 0.045 and a Beverton-Holt stock-recruitment relationship.
Uncertainties relate to the proportion of the stock indexed by the 2013 acoustic survey and patterns of year class strengths that are based only on 5 years of age composition data (MPI, 2014a,b) as well as in the estimation of BMSY, due to uncertainty in steepness and in the form of the stock-recruitment relationship (Cordue, 2014; MPI, 2014d).
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.
According to the stock status two scenarios were considered: at the current catch limit at 930 tons, SSB is expected to increase in the next 5 years but remaining below the Soft limit. Considering a scenario of zero catches it would take 21 years (Tmin) to reach the lower bound of the biomass target range (30% of B0) with 70% of probability (MPI, 2014a).
Reference points are calculated in relation to B0 which is estimated at 100.000 tons. The management strategy for the stock was based on fluctuation of the stock around the estimated BMSY = 30-40% of B0, between 30.000-40.000 tons (MPI, 2014a). BMSY for orange roughy was reassessed in 2014 at 26% of B0 considering a Beverton-Holt stock-recruitment relationship based mainly on data collected from this fishery, as it had the most data on recruitment at low stock sizes (Cordue, 2014). BMSY for this stock as such is now estimated to be 26,000 tons. The target range was being reviewed and the upper limit (40% of B0) will probably be adopted as the mid-point considering the range between 30-50% of B0 (Cordue, 2014; MPI, 2014d).
Fishing intensity target is currently set between U30%B0–U40%B0 (MPI, 2014a).
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= 20.000 tons and considered as 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= 10.000 tons.
MSC pre-assessment report considers the Hard limit as Blim and both BMSY and Blim as inadequate for the management of this fishery (Punt et al., 2013).
The current biomass level at 14% of B0 = 14.000 tons, Very Unlikely (< 10%) to be at or above the lower end of the management target range, Likely (> 60%) to be below the Soft Limit and Unlikely (< 40%) to be below the Hard Limit. Fishing intensity in 2014 was estimated at U35%B0, meaning that fishing at 35 would cause the SSB to reach deterministic equilibrium at 35% of B0. Overfishing is About as Likely as Not (40-60%) to be occurring. Catches have been following limits trends, decreasing in the last years (MPI, 2014a).
Following an increasing trend, in the beginning of the 1990s landings reached 10.000 tonnes. Since then decreased to around 0.888 t (the minimum value) in 2004 and have increasing since then. Based on both performed models, the spawning stock has been increasing since 2000 and the fishing intensity has been decreasing recently (MPI, 2014a).