Virginia Institute of Marine Science
Globally, tunas are among the most valuable fish stocks, but are also inherently difficult to monitor
and assess. Samples of larvae of Western Atlantic bluefin tuna Thunnus thynnus (Linnaeus, 1758) from
standardized annual surveys in the northern Gulf of Mexico provide a potential source of “offspring”
for close‑kin mark‑recapture (CKMR) estimates of abundance. However, the spatial patchiness and
highly skewed numbers of larvae per tow suggest sampled larvae may come from a small number of
parents, compromising the precision of CKMR. We used high throughput genomic profiling to study
sibship within and among larval tows from the 2016 standardized Gulf‑wide survey compared to
targeted sampling carried out in 2017. Full‑ and half‑siblings were found within both years, with 12%
of 156 samples in 2016 and 56% of 317 samples in 2017 having at least one sibling. There were also
two pairs of cross cohort half‑siblings. Targeted sampling increased the number of larvae collected
per sampling event but resulted in a higher proportion of siblings. The combined effective sample size
across both years was about 75% of the nominal size, indicating that Gulf of Mexico larval collections
could be a suitable source of juveniles for CKMR in Western Atlantic bluefin tuna.
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McDowell, Jan; Bravington, Mark; Grewe, Peter; (...); Biesack, Ellen E.; and et al, Low levels of sibship encourage use of larvae in western Atlantic bluefin tuna abundance estimation by close-kin mark-recapture (2022). Scienfic Reports, 12(1), 18606.