Last updated on 18 September 2014
The last stock assessment was conducted in 2001 using a deterministic stock reduction technique, to determine both current and virgin biomass B0. Maximum exploitation rate was fixed at 0.67, sexes separately and a Beverton-Holt stock-recruitment relationship was assumed. Abundance indices and commercial catch-effort (mean catch per tow) data were used. Trawl surveys were performed in June 1995, winter 1998 and June 2000. The results from those surveys indicated a decreasing trend but the environmental variables may have influenced the distribution of orange roughy. The size frequency data show high levels of stock variability between fisheries on features or feature groups (MPI, 2014).
Assessments were carried out for three alternative sets of biomass indices and all resulted in similar B0 estimates. Yield estimates resulted from the assessment are all much lower than recent catches. No assessment of stock status in Mercury-Colville box is currently available (MPI, 2014).
Last updated on 19 October 2014
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.
In the plenary document, catches for Mercury-Colville box are to be maintained at 200 tons (MPI, 2014). But the agreement by stakeholders was done after the last AMP and no scientific advice has been provided since then.
Last updated on 19 Oct 2014
In the 2001 stock assessment, three alternative models were developed having resulted in similar reference points. B0 was defined at 3,000 tons (Alternative 1) and 3,200 tons (Alternatives 2 and 3). The MSY biomass reference point (BMSY) was defined as 960 tons (Alternative 1) and 900 tons (Alternatives 2 and 3). It was assumed that BMSY corresponds to 30% of B0 (MPI, 2014). However BMSY for orange roughy stocks was reassessed in 2014 at 26% of B0 (Cordue, 2014, DWG, 2014).
Last updated on 18 September 2014
The current status of the orange rough biomass in Mercury-Colville box is not known: there are not current abundance indices to compare with the MSY reference point B(MSY) and the estimate of virgin biomass is not available.
The 2001 assessment of the Mercury-Colville box indicated that biomass had been reduced to 10-15% B0 which was well below estimated BMSY (currently thought to be 26% B0). Information collected since that time has not improved the understanding about the status of the stock (MPI, 2014).
Last updated on 18 Sep 2014
This fishery was developed in 1994. Prior that period, reported landings were generally small (MPI, 2014).
Between 1995-2000, the catch limit for the Mercury–Colville Box was 1,000 tons. Due to the stock condition, this value was reduced to 30 tons in 2000/2001, to be caught as bycatch in the cardinalfish fishery. Catches have been smaller than the catch limit and the target species has mostly been recorded as cardinalfish. On average, catch rates have been below or equal to 0.2 tons/tow, but tons/hour increased during the period 2007-2009 (Anderson and Dunn, 2012).