1. New Zealand Orange Roughy Fisheries and assessments SPRFMO THIRD WORKSHOP - DEEP WATER WORKING GROUP
Alistair Dunn
23 May 2017

2. Overview New Zealand orange roughy stocks Assessments and management
A (brief) history
Current status
Assessments and management
Example: Puysegur
Assumptions of productivity
The role of CPUE, age/length data, trawl surveys, and acoustics
MSC Certification

3. Orange roughy in New Zealand
Multiple stocks around New Zealand
Managed as several separate stocks
But, stock structure not certain

4. Orange roughy distribution around New Zealand
Wide-spread at depths of 700m to 1500m
Most abundant m

5. Orange roughy An important fishery in New Zealand
Commercially valuable
estimated export value NZ$62 Million
Current catches are about 8600 t
Main fisheries on the Chatham Rise and Challenger Plateau
Previously closed fishery in Puysegur about to re-open in the sub-Antarctic

6. Assessment and status before 2014
F based strategy
Used individual (absolute) estimates of acoustic biomass
Integrated models attempted …
CPUE, egg surveys, and trawl surveys
Age and length data
Stock status uncertain
“Controversial” assessment processes and management responses

7. Assessments since 2014
Currently assessed using statistical catch-at-age integrated models
ORH 3B (North-west Chatham Rise and East & south Chatham Rise)
ORH 7A
ORH MEC
ORH 3B (Puysegur)

8. Currently not formally assessed
Catch limits based on historical catch trends, or CPUE
ORH 1
ORH 2A (north)
ORH 7B (closed)

9. Productivity
Typically live to a maximum of about years. M=0.045y-1
Maturity assumed to be between years
interpretation of the transition zone on otoliths
Spawning fish likely to be older
Based on ageing of spawning aggregations
50% of fish spawning range from 32–41 years

10. CPUE indices
CPUE (catch per unit effort) previously used as an index of abundance
But
Inconsistencies between CPUE and survey indices
Strong evidence of hyper-depletion from assessment models
CPUE estimates from spawning aggregations on hills difficult to interpret

11. Acoustic surveys
Improvement in survey design and acoustic technologies
Multi-frequency and Acoustic-Optical Systems
Resulting in improvements in acoustic abundance indices
Determination of prior on acoustic q allowed better interpretation of interpretation of relative indices

12. Stock status Most orange roughy stocks were initially overfished
Estimated to be about t of orange roughy in New Zealand before fishing
Current status of the assessed stocks
range from low (MEC) to healthy (Puysegur)
15-50% B0

13. Stock biomass (SSB) trajectories

14. Example: Puysuger Stock in the Southern region of New Zealand
Stock reduction analysis based on CPUE estimated the stock size at 7% B0
Closed in 1997/98

15. Example: Puysegur Reliability of the previous assessments not known
New approaches to the treatment and inclusion of historical data
More robust
Higher threshold for data quality
Better understanding of orange roughy population dynamics (better methods)
New data (2015) included acoustic biomass estimates and associated age data

16. Example: Puysegur

17. Example: Puysegur SSB trajectory
No evidence from this stock assessment that the stock was ever at 7% B0. Pretty much as expected as soon as the 2015 AF was sited.

18. Example: Puysegur stock assessment
Integrated statistical catch-at-age model (CASAL)
Single sex
Single area
Ages
Mature & immature fish
Two time periods
Non-spawning season fishery
Spawning season fishery
Fixed M=0.045, steepness=0.75
Length-weight and growth rates assumed from other areas

19. MPD fits to trawl LF (start of 1993 FY)

20. Base model: MCMC residuals: biomass
Most of each distribution inside +- 2 which is fine.

21. Base model: MCMC residuals: trawl LF 93

22. Base model: MCMC: acoustic q prior and posterior
Moved to the left a tad – certainly moved.

23. Base model: MCMC: true YCS

24. Base model: MCMC: SSB trajectory
No evidence from this stock assessment that the stock was ever at 7% B0. Pretty much as expected as soon as the 2015 AF was sited.

25. Marine Stewardship Council certification
NZ orange roughy certified by MSC
Certified in December 2016
About 6000 t certified (~70% of total catch)
But
Large investment by industry and New Zealand
Initial MSC pre-assessment in 2013
Followed by a programme of investment to bring the fishery up to standard
The certification was objected to and subject to a full hearing with an independent adjudicator

26. Summary
Current assessment using integrated statistical catch-at-age models
Relies on age frequency data and acoustic indices
Use assumptions of productivity based on data collection on the area of interest or ‘borrowed’ from neighbouring areas
Reasonably sophisticated modelling, but these are becoming more ‘standard’ as experience grows
Management advice based on harvest control rules from management strategy evaluations