UW Aquatic & Fishery Sciences Quantitative Seminar

Bridget Ferris

School of Aquatic & Fishery Sciences, UW

Variation in tuna mercury levels: links with oceanography, life history, and diet


Mercury (Hg) levels vary in high trophic level fish and can often exceed consumption advisories. Among those species identified as having elevated Hg levels, bigeye and yellowfin tuna (Thunnus obesus and Thunnus albacares) are notable because they are also the target of some of the largest commercial fisheries in the Pacific Ocean. Regionally, Hg concentrations in tunas may vary because Hg levels and speciation in the water column depend on dissolved oxygen concentrations and primary production rates. We tested whether variation in water Hg concentrations would translate into elevated Hg levels in bigeye and yellowfin tuna captured in areas having these characteristics. Analysis of available oceanographic data confirmed that regions with high tuna Hg levels were those with elevated chlorophyll and shallow minimum oxygen depths. Trace metals are also useful in estimating biological parameters difficult to measure in fish. In addition to the study described above, I will show preliminary results of life history and diet parameter estimation using Hg concentrations combined with individual mass balance models.

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