Holbert et al. 2023 — Mercury in Hawaiian recreational fish
Holbert and colleagues measured total mercury (THg) in muscle, liver, and kidney tissues of four nearshore recreational fish species commonly caught around O’ahu, Hawai’i: giant trevally, bluefin trevally, and two species of bonefish. The study compared THg to FDA and EPA consumption advisory benchmarks. Both bonefish species had mean muscle THg exceeding FDA/EPA benchmarks, suggesting consumption advisories should be considered. The authors also evaluated metallothionein (MET) and thioredoxin reductase (TrxR) mRNA expression as molecular biomarkers of mercury exposure, finding that MET expression in round jaw bonefish kidney tissue showed a marginally significant positive correlation with kidney THg.
Key numbers
- Round jaw bonefish (A. glossodonta, n=19) mean muscle THg: 330 ng/g wm (0.330 mg/kg)
- Round jaw bonefish mean kidney THg: 1,156 ng/g wm (highest tissue; kidney as demethylation site)
- Round jaw bonefish mean liver THg: 339 ng/g wm
- Giant trevally (C. ignobilis, n=13) mean muscle THg: 187 ng/g wm (0.187 mg/kg)
- Giant trevally mean liver THg: 277 ng/g wm
- Bluefin trevally (C. melampygus, n=4): not separately reported for muscle mean in abstract
- Sharp jaw bonefish (A. virgata, n=2): insufficient n for statistical analysis
- FDA action level for commercial fish: 1,000 ng/g wm (1 mg/kg); both bonefishes below this commercial threshold
- FDA/EPA consumption advisory benchmarks for recreational consumption: lower thresholds apply; bonefishes exceeded these lower benchmarks
- THg accumulated with length and calculated age in round jaw bonefish and giant trevally (bioaccumulation with age confirmed)
- MeHg typically constitutes >95% of THg in fish muscle; speciation not performed, but tissue distribution (high kidney relative to muscle) suggests demethylation processes
Methods (brief)
THg in muscle, liver, kidney by cold vapor atomic fluorescence spectrometry (CVAFS) or equivalent (not specified in abstract; standard for THg in fish). Sample collection around O’ahu; n=38 total across four species. mRNA extraction and quantitative PCR for MET and TrxR transcripts. Fish age estimated from length-weight relationships and otolith rings (implied by “calculated age”).
Implications
Certification: Round jaw bonefish muscle THg (mean 330 ng/g) exceeds recreational consumption advisory benchmarks. For any product incorporating Hawaii-sourced recreational catch species, THg monitoring is warranted. Giant trevally at 187 ng/g warrants advisory consideration at higher consumption frequencies.
Courses: Demonstrates how nearshore recreational fish differ from commercially traded species in mercury burden; Hawaii-specific context for seafood safety discussions.
App: Giant trevally and bonefish should be flagged as moderate-to-high THg risk species if listed as ingredients. The kidney/liver THg distribution pattern is relevant to understanding tissue-specific risk.