Fisheries Infosite

Plenary (SNA_FINAL 08)

SNA_FINAL 08.pdf

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SNA_FINAL 08.pdf (547.6 kb)


No new stock assessments are presented for snapper stocks. The assessments from earlier years are summarised below.
These stocks were last assessed in 2000. The status of the two sub-stocks differs.
East Northland
The base case East Northland stock assessment completed in 2000 indicated that the recruited biomass at that time was at about the BMSY reference point and is expected to exceed BMSY at the end of the twenty-year projection period (with 67% probability). This conclusion is robust to all sensitivities investigated, except when a low natural mortality was investigated. Even in this sensitivity, the stock is expected to increase to near BMSY at the end of the projection period.
Hauraki Gulf/Bay of Plenty
The base case Hauraki Gulf/Bay of Plenty stock assessment completed in 2000 indicated that the recruited biomass at that time was less than the BMSY reference point but expected to increase over the next twenty years under the current TACC and estimated levels of recreational and unreported catch.
It is expected to exceed the BMSY reference point at the end of the projection period (with 100% probability). This conclusion is robust to all sensitivities investigated. For SNA 1 as a whole, catches at the level of the TAC will allow the stock to increase over the next
20 years.

An assessment model was fitted to four years of proportions at age data in 2002. As there are no indices of biomass available, model estimates must be treated with caution. For almost all runs, the current biomass was estimated to be near to or somewhat below BMSY but was projected to increase
towards BMSY by 2006 at the current catch level (436 t).

An assessment was completed in 2002 for this stock. Model results indicated that the stock should have rebuilt substantially since the low levels of the early 1980s. However, there are no current indices of abundance for this stock to verify the results from the assessment model; only catch at age
data is available for recent years.
The MLEs for B2001 for the base case and all of the sensitivity runs are well above BMSY. The large reduction in catches from the mid-1980’s and the long period that cohorts persist in the recent catch at age data are reflected in model estimates of a rebuilding stock. The results indicate the stock would
continue to increase even if future catches were substantially larger than those currently being taken.

The 2005 stock assessment indicated that current biomass (start of year 2004–05) was between 8% and 12% B0 and the biomass was predicted to slowly increase at the TACC level of 1500 t. However, from 1 October 2005 the TACC was reduced to 1300 t to ensure a faster rebuild of the stock. At this
TACC level the rebuild to BMSY (20%B0) occurred after 2018 in all cases assuming either constant recreational effort, or capped recreational catch at the alternative levels of 300 t or 600 t per year. Rebuilding tended to be slower for runs that allowed the recreational catch to rise with increasing biomass.

Document date
Thursday, 15 May 2008
Document type
V 1.3
File format
Adobe PDF
File size
547.6 kb
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Uploaded date
Friday, 7 November 2008

Search tags
Species: SNA;
Stock: SNA1; SNA10; SNA2; SNA3; SNA7; SNA8; SNAET;

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