Research

Stock Assessment Research

Thursday, 26 February 2009 18:37

In the stock assessment section we carry out research in several broad areas. We carry out research to improve the regional assessments, by developing new methods and by new analyses of fishery data. We collaborate on this work with other research agencies, including organizations in Japan, Australia, USA, New Caledonia, Europe, Chinese Taipei, and New Zealand. We develop software to run the assessments, and to help fishery managers and stakeholders interpret the stock assessments and the resulting management advice.

Method development for WCPO stock assessments

Wednesday, 27 October 2010 11:58

We continually work to improve the accuracy and reliability of the stock assessments. Changes to assessment structure and methods are investigated and, where approved by the WCPFC Scientific Committee, included in the stock assessments.

SC6-SA-WP-01. 2010. Background analyses in the development of the 2010 WCPO bigeye tuna assessment. S. Harley, S. Hoyle, P. Williams, J. Hampton.
SC6-SA-WP-10. 2010. Stock Assessment of skipjack tuna in the western and central Pacific Ocean. S. Hoyle, P. Kleiber, N. Davies, S.J. Harley, J. Hampton.
SC6-SA-IP-01. 2010. Report from the pre-assessment workshop in April 2010. S. J. Harley, S. D. Hoyle.
SC5-SA-WP-03. 2009. Stock assessment of yellowfin tuna in the western and central Pacific Ocean. A. Langley, S. Harley, S. Hoyle, N. Davies, J. Hampton, P. Kleiber.
SC5-SA-WP-06. 2009. Stock assessment of albacore tuna in the south Pacific Ocean. SPC, Noumea, New Caledonia. S. Hoyle, N. Davies.
SC5-SA-IP-01. 2009. Report from the SPC pre-assessment workshop, Noumea, April 2009. S. J. Harley, N. Davies, S. D. Hoyle.
SC4-SA-WP-1. 2008. Stock assessment of bigeye tuna in the western and central Pacific Ocean, including an analysis of management options. A. Langley, J. Hampton, P. Kleiber, S. Hoyle.

For further information contact Shelton Harley, Simon Hoyle, or John Hampton.

Reference points for fishery management

Wednesday, 27 October 2010 11:59

Fishery reference points link stock assessment results with management action. We study the performance of alternative reference points.

SC6-MI-WP-01. 2010. Stochastic and deterministic projections: A framework to evaluate the potential impacts of limit reference points, including multi-species considerations. N. Davies, S.J. Harley.
SC5-ME-WP-02. 2009. Characteristics of potential reference points for use in WCPFC tuna stock assessments. S. Harley, S. Hoyle, J. Hampton, and P. Kleiber.

For further information contact Shelton Harley, Nick Davies, or John Hampton.

Biological parameters for WCPO stock assessments

Wednesday, 27 October 2010 12:05

We develop better methods for estimating and modelling the biological parameters used in stock assessments, such as natural mortality, reproductive potential, and growth. We update biological parameters based on recent data. We also investigate the effects of alternative approaches on stock assessment results, and possible benefits of better data.

SC5-BI-WP-03. 2009. Revised biological parameter estimates for application in yellowfin stock assessment. S. Hoyle, S. Nicol, D. Itano.
SC4-ME-WP-1. 2008. Sensitivity of the bigeye tuna stock assessment to alternative biological and reproductive assumptions. S. Hoyle, S. Nicol.
SC4-ME-WP-2. 2008. Adjusted biological parameters and spawning biomass calculations for albacore tuna in the south pacific, and their implications for stock assessments. S. Hoyle, S. Nicol.

For further information contact Simon Hoyle or Simon Nicol.

Structural sensitivity analysis

Wednesday, 27 October 2010 12:04

Stock assessment models simplify reality. In some cases alternative assumptions can be made, and may give different results. The differences between the alternative results are part of the uncertainty in the results. We carry out sensitivity analyses to measure this uncertainty, and to work out the best ways to reduce it. We also develop new methods for structural sensitivity analysis.

SC5-SA-IP-03. 2009. General structural sensitivity analysis for the yellowfin tuna stock assessment. S. J. Harley, S. D. Hoyle, F. Bouyé.
SC5-SA-IP-04. 2009. General structural sensitivity analysis for the albacore tuna stock assessment in the south Pacific Ocean. N. Davies, S.D. Hoyle, F. Bouyé.
SC4-SA-WP-3. 2008. General structural sensitivity analysis for the bigeye tuna stock assessment. S.D. Hoyle, A.D. Langley, J. Hampton.

For further information contact Simon Hoyle or Shelton Harley.

CPUE analysis methods

Wednesday, 27 October 2010 12:00

All of our main WCPO stock assessments use standardized catch per unit effort (CPUE) data as influential indices of abundance. We are researching better analysis methods, to provide more reliable CPUE indices.

SC6-SA-WP-02. 2010. Analyses of Japanese longline operational catch and effort for bigeye tuna in the WCPO. S.D. Hoyle, H. Shono, H. Okamoto, A.D. Langley.
SC6-SA-WP-03. 2010. CPUE standardisation for bigeye and yellowfin tuna in the western and central Pacific Ocean. S. Hoyle.
SC6-SA-WP-08. 2010. A standardized CPUE analysis of the Japanese distant-water skipjack pole-and-line fishery in the western and central Pacific Ocean (WCPO), 1972-2009. A. Langley. K. Uosaki, S. Hoyle, H. Shono, M. Ogura.
SC5-SA-WP-01. 2009. CPUE Standardization for bigeye and yellowfin tuna in the western and central Pacific Ocean. SPC, Noumea, New Caledonia. S. Hoyle.
SC5-SA-WP-02. 2009. Yellowfin CPUE standardization for Taiwanese distant water longline fishery in the WCPO - with emphasis on target change. Chang, S-K., S. Hoyle, H-I Liu.
SC5-SA-WP-05. 2009. Standardized CPUE for distant water fleets targeting south Pacific albacore. Bigelow, K., S. Hoyle.
SC3-ME-IP-01. 2007. Proceedings of the pelagic longline catch rate standardization meeting. S.D. Hoyle, K. Bigelow, A. Langley, M. Maunder.

For further information contact Simon Hoyle or Shelton Harley.

Analysis of size frequency data

Wednesday, 27 October 2010 12:06

WCPO stock assessments fit to size (length and weight) data, and are sensitive to the way these data are collected, analyzed and modelled. We investigate ways to improve the assessments by improving the ways we use these data.

SC6-SA-WP-01. 2010. Background analyses in the development of the 2010 WCPO bigeye tuna assessment. S. Harley, S. Hoyle, P. Williams, J. Hampton.
SC5-SA-IP-05. 2009. Factors influencing the size of albacore tuna sampled from the South Pacific albacore longline fisheries. D. Bromhead, S.D. Hoyle, A. Williams, S.B. Wang, S.K.Chang.
SC4-ST-IP-03. 2008. Length frequency sampling data and its influence on the south Pacific albacore stock assessment. S. Hoyle, P. Sharples.
SC3-SA-IP-01. 2007. Trends in size composition of longline-caught albacore in the South Pacific. B. Molony.
SC2-ME-IP-02. 2006. Spatial and temporal variation in the size composition of the yellowfin and bigeye longline catch in the WCPO. A. Langley.

For further information contact Simon Hoyle.

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Main activities

Stock assessment