Date of Award
Doctor of Philosophy (PhD)
Cynthia M. Jones
Simon R. Thorrold
Dayanand N. Naik
This is the first work examining the utility of scale chemistry for determining natal origins and habitat associations. I quantified a relationship of scale chemistry to water chemistry, quantified geographic variation in scale chemistry, and evaluated stability of scale chemistry through maturation. Scale chemistry accurately reflected trace element composition of the water in which fish had lived. Juvenile spot (Leiostomus xanthurus) were held in four concentrations of Sr, Cd, and Ba maintained at either 20°C or 25°C, for 42 days. Strontium:Ca, Cd:Ca, and Ba:Ca levels in scales were linearly related to environmental concentrations while temperature had no effect. These results suggested scale chemistry could reflect differences related to habitat use by fishes. To test this, Mg:Ca, Mn:Ca, Sr:Ca, and Ba:Ca levels in scales from juvenile weakfish (Cynoscion regalis) from five estuaries along the Atlantic coast were measured. Significant variability in multivariate elemental signatures was found among estuaries and between collections from 1996 and 1997. Linear discriminant function analysis was used to classify individual juvenile weakfish to natal estuary with ∼65% accuracy. Results from simulated learning and test samples derived from the juvenile data indicated a maximum likelihood (ML) procedure could estimate proportions of juveniles from each natal estuary with ∼90–95% accuracy. Inter-annual variability in the trace element signatures meant fish could not be accurately classified to natal estuary based on signatures collected from juvenile fish in a different year. Trace element levels in scales were significantly correlated with otolith concentrations from the same fish in both studies, suggesting that similar processes control both scale and otolith chemistries. Finally, using natal-estuary signatures, natal location of adult weakfish collected in Pamlico Sound, Chesapeake Bay, and Delaware Bay was estimated with ML. Composition of adults was estimated similarly by otolith and scale chemistries. However, these data suggested that scale chemistry was not stable after the juvenile period possibly due to continued crystallization. In all, at least some trace elements in scales reflect levels in the ambient environment, and may be useful for quantifying life-history characteristics of individual fish. However, caution is required when applying the technique to adults as elemental signatures may degrade.
Wells, Brian K..
"Evaluation of Fish Scale Chemistry for Determining Habitat Associations"
(2000). Doctor of Philosophy (PhD), dissertation, Biological Sciences, Old Dominion University, DOI: 10.25777/yv2w-kn73