Distinguishing Wild from Hatchery-Produced Juvenile Red Snapper with Otolith Chemical Signatures

North American Journal of Fisheries Management
Gibson, ;Phelps, Ronald P.;Patterson, W. P.;Patterson, W. F.;Chen, Z.
Pub ID:
Otolith chemical signatures were evaluated as natural tags to distinguish wild from hatcheryproduced
juvenile red snapper Lutjanus campechanus. Otoliths were sampled from 59 hatchery-reared fish
and 146 wild fish collected over the continental shelf from northwest Florida to Texas. One sagitta from each
fish was cleaned, dissolved in ultrapure nitric acid, and analyzed with sector field inductively coupled plasma
mass spectrometry to test for differences in otolith element:Ca ratios (Ba:Ca, Li:Ca, Mg:Ca, Mn:Ca, and
Sr:Ca) between wild and hatchery fish. The second sagitta was cleaned, ground to a fine powder, and analyzed
with stable isotope ratio mass spectrometry to test for differences in delta (d) values of the stable isotopes 13C
and 18O. Significant differences existed in otolith chemical signatures between hatchery and wild juveniles
(multivariate analysis of variance, Pillai’s trace: P< 0.001). Jackknifed classification accuracies from linear
discriminant function analysis indicated that hatchery fish could be distinguished from wild fish with 100%
accuracy based on otolith chemical signatures. The most important otolith chemistry feature in distinguishing
hatchery from wild fish was d13C, with the mean difference in d13C between hatchery and wild fish (2.6%)
being similar to the mean difference in d13C between hatchery feeds and the predominant food of wild
juveniles (2.8%). Overall, results suggest that otolith chemical signatures may be employed as effective
natural tags for mass marking of future stockings of red snapper or other marine fishes to estimate the
hatchery contribution to wild populations.
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