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- Objectives
- Estimate age, growth, maturity, and fecundity of yellowfin from four distinct areas of the eastern Pacific for use in spatially-structured stock assessment models
- Background
- Current estimates of age, growth, maturity, and fecundity of yellowfin are based on otolith and ovarian tissue samples collected over 30 years ago.
- During 2009-2016 observers collected otolith and ovarian tissues samples at sea throughout the EPO
- Tagging and morphometrics data indicate there are multiple stocks of yellowfin in the EPO, probably with different life history characteristics
- Heavily-exploited fish stocks often show trends towards earlier maturation
- Relevance for management
- Spatially-structured stock assessments based on geographically-explicit life history parameters will provide a more accurate basis for the staff’s management advice
- Duration
- 5 years; initiated in 2017
- Workplan and status
- 2017-2022: Preparation and reading of otolith samples for age estimates
- 2018-2021: Preparation and reading of ovarian tissue samples for maturity and fecundity estimates
- 2019-2023: Analyses of age and growth and reproductive biology data, and preparation of manuscripts
- Deliverables
- Updated, geographically-explicit life-history parameters for use in spatiallystructured stock assessments
- Manuscripts for publication in scientific journals
- Updated date: 01 May 2022
- Progress summary for the reporting period
- Daily increment counts for 279 otoliths have been completed, 134 from the central offshore region, 130 from the central nearshore region, and 15 from the northern area.
- A general additive model was used to investigate whether differences in growth exists between the central nearshore and offshore regions.
- Microscopic slides of ovarian tissues from 1,756 fish from the four distinct areas have been evaluated and histological classifications of reproductive status completed.
- Fecundity estimates from 146 female yellowfin tuna have been completed.
- Fuller, D. and K. Schaefer. Abstract in Proceedings of the 69th annual tuna conference, 21-24 May 2018, Lake Arrowhead, USA
- Fuller, D. and K. Schaefer. Abstract in Report of the workshop on age and growth of bigeye and yellowfin tunas in the Pacific Ocean, 23-25 January 2019, La Jolla, USA
- Schaefer, K. M., and Fuller, D. W. 2022. Spatiotemporal variability in the reproductive biology of yellowfin tuna (Thunnus albacares) in the eastern Pacific Ocean. Fisheries Research, 248, 106225.
- Comments
- Due to the continuation of the COVID-19 pandemic access to the SWFSC has slowed progress on preparation and reading of otoliths. Otolith preparation and reading was further slowed by the hiring and subsequent training of new staff members.