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Southern blue whiting (Micromesistius australis) fishery assessment for the 1995-96 fishing year

By: Hanchet, S.M.
Contributor(s): Ingerson, J.K.V | NIWA Wellington (N.Z.).
Material type: materialTypeLabelBookSeries: New Zealand fisheries assessment research document ; 95/20.Publisher: Wellington : NIWA, 1995Description: 24 p.Subject(s): SOUTHERN BLUE WHITING | NEW ZEALAND | FISHERY RESOURCES | CAMPBELL ISLAND | BIOMASS | BOUNTY PLATFORM | PUKAKI RISE | STOCK ASSESSMENTOnline resources: Click here to access online
Incomplete contents:
This paper reviews the stock assessment of southern blue whiting (SBW) resources in New Zealand waters. A summary of the recent fishing season is presented and the results of research carried out over the past year are outlined. For the Campbell Island stock, catch-at-age data from 1979 to 1994, CPUE data from 1986 to 1994, and acoustic estimates of adult biomass from 1993 to 1994 were fitted using the separable Sequential Population Analysis used in last year's assessment. Estimates of mid-season spawning stock biomass declined from 1979 to 1993, but increased sharply in 1994. This increase was due to the recruitment of the very strong 1991 year class to the fishery. CAY (F/ sub 0.1/ yield) was estimated for 1994-95 by projecting forward 1995 beginning of year numbers at age from the model, assuming recruitment at age 2 equalled the geometric mean of recruitment over the period 1979 to 1992. Similarly, CAY for 1995-96 was estimated assuming the 1994-95 catch equalled (i) CAY/sub 1994-95/ or (ii) 11 000 t. CAY/sub 1994-95/ equalled 44 000 t (90% CI 33 000-60 000 t). CAY/sub 1995-96/ equalled 39 000 t (90% CI 30 000-52 000 t) under assumption (i), and 50 000 t (90% CI 38 000-67 000 t) under assumption (ii). MSY was estimated by multiplying the yield per recruit at F/sub max/ by the arithmetic mean of recruitment over the period 1979 to 1992, and equalled 12 700 t. Estimates of current biomass for the Bounty Platform and Pukaki Rise stocks were derived from the results of the acoustic surveys. Adult biomass estimates from surveys in 1993 and 1994, together with the estimated recruitment (also from those surveys), were projected forward to 1995 assuming changes in the population from natural mortality were exactly balanced by growth. The projection was carried forward to 1996 using the estimated recruitments from the surveys, making the same assumptions about M and growth, and assuming the 1994-95 catch equalled (i) CAY/sub 1994-95/ and (ii) the current (1993-94) catch limit. Estimates of CAY/sub 1994-95/ on Bounty Platform ranged from 22 000 to 30 000 t and CAY/sub 1995-96/ ranged from 15 000 to 25 000 t. Estimates of CAY/sub 1994-95/ on Pukaki Rise ranged from 12 000 to 22 000 t. and CAY/sub 1995-96/ ranged from 8 000 to 20 000 t. (auths)
In: New Zealand fisheries assessment research document
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Item type Current location Call number Copy number Status Date due Barcode
JOURNAL JOURNAL WELLINGTON
JOURNALS
NO. 95/20 1 Available J09944

15 refs; 14 tables; 10 figs.- Not to be cited without permission of the author(s)

This paper reviews the stock assessment of southern blue whiting (SBW) resources in New Zealand waters. A summary of the recent fishing season is presented and the results of research carried out over the past year are outlined. For the Campbell Island stock, catch-at-age data from 1979 to 1994, CPUE data from 1986 to 1994, and acoustic estimates of adult biomass from 1993 to 1994 were fitted using the separable Sequential Population Analysis used in last year's assessment. Estimates of mid-season spawning stock biomass declined from 1979 to 1993, but increased sharply in 1994. This increase was due to the recruitment of the very strong 1991 year class to the fishery. CAY (F/ sub 0.1/ yield) was estimated for 1994-95 by projecting forward 1995 beginning of year numbers at age from the model, assuming recruitment at age 2 equalled the geometric mean of recruitment over the period 1979 to 1992. Similarly, CAY for 1995-96 was estimated assuming the 1994-95 catch equalled (i) CAY/sub 1994-95/ or (ii) 11 000 t. CAY/sub 1994-95/ equalled 44 000 t (90% CI 33 000-60 000 t). CAY/sub 1995-96/ equalled 39 000 t (90% CI 30 000-52 000 t) under assumption (i), and 50 000 t (90% CI 38 000-67 000 t) under assumption (ii). MSY was estimated by multiplying the yield per recruit at F/sub max/ by the arithmetic mean of recruitment over the period 1979 to 1992, and equalled 12 700 t. Estimates of current biomass for the Bounty Platform and Pukaki Rise stocks were derived from the results of the acoustic surveys. Adult biomass estimates from surveys in 1993 and 1994, together with the estimated recruitment (also from those surveys), were projected forward to 1995 assuming changes in the population from natural mortality were exactly balanced by growth. The projection was carried forward to 1996 using the estimated recruitments from the surveys, making the same assumptions about M and growth, and assuming the 1994-95 catch equalled (i) CAY/sub 1994-95/ and (ii) the current (1993-94) catch limit. Estimates of CAY/sub 1994-95/ on Bounty Platform ranged from 22 000 to 30 000 t and CAY/sub 1995-96/ ranged from 15 000 to 25 000 t. Estimates of CAY/sub 1994-95/ on Pukaki Rise ranged from 12 000 to 22 000 t. and CAY/sub 1995-96/ ranged from 8 000 to 20 000 t. (auths)

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