58_OEO3A_09

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58_OEO3A_09.pdf

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58_OEO3A_09.pdf (470.7 kb)

Abstract
The smooth oreo stock assessment was updated in 2009. The black oreo stock assessment is
unchanged from 2004.
5.1 Black oreo, OEO 3A
The current and virgin biomass for black oreo in OEO 3A were estimated using a CASAL spatial stock assessment. Total mature biomass for 2002–03 was estimated to be 52% of the initial biomass (B0), which is greater than BMSY (27%B0). However, the size of the current biomass relative to initial biomass is not equal across the three sub-areas, with Areas 2 and 3 being 29% and 7% of their respective mature equilibrium virgin biomass levels while Area 1 is estimated to be at 96%. There is uncertainty in the estimates of biomass in Area 1 because the acoustic estimate is based on black oreo in layers that are a mixture of species for which the acoustic method has potential bias problems.

Five year projections to estimate future mature and vulnerable biomass were carried out at different constant annual catches assuming the current catch split between areas. An annual catch of 1885 t, the likely maximum catch of black oreo for the fished areas (areas 2 and 3), given the current management arrangements, gave a 100% probability that mature biomass would be greater than both 20% B0 and 27%B0 (BMSY). The corresponding probabilities for vulnerable biomass are a 65 % probability that it would be greater than 20% B0 and a 0 % probability that it would be greater than 27 %B0 (BMSY). The difference between the mature and vulnerable biomass status is a consequence of the current stock assessment that estimates a large biomass of mature black oreo in area 1 that is not fished.

Model biomass estimates are uncertain because of a range of factors, including sensitivity to the target strength of black oreo, uncertainty in the estimates of M, and the assumption that recruitment is deterministic.

5.2 Smooth oreo, OEO 3A
This assessment was updated in 2009. Total mature biomass for 2008 09 was estimated to be 36% (29–45 % 95% confidence interval) of the initial biomass (B0). The projections showed that biomass should increase at catch levels of 1400 t over the next 5 years.

Model biomass estimates are uncertain because of a range of factors, including the assumption that recruitment is deterministic, that the acoustic index is assumed to be an absolute estimate of abundance, uncertainty in the estimates of M, and the sex ratio of the mature biomass (see section 4.3.3 “Other factors” above).

Document date
Sunday, 31 May 2009

Document type
V 1.3

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Adobe PDF

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470.7 kb

Reference number
2009

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M:\SCIPOL\Working Groups 2009\Plenary 2009\FINAL\MFish 2009 May Plenary\May 2009 - PDF\58_OEO3A_09.pdf

Uploaded date
Thursday, 11 June 2009

Search tags

Species: OEO;
Stock: OEO3A;

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