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Advisor(s)
Abstract(s)
Xenoestrogenic effects have been reported in thicklip grey mullet, Chelon labrosus, used as
pollution sentinel organisms in estuaries in the Southeast Bay of Biscay with intersex gonads described
in populations from some contaminated estuaries. Despite evidence of reproductive stress in this
catadromous fish species, knowledge of mullet reproductive movements and connectivity between
estuaries is lacking. This study investigates the population structure of C. labrosus using otolith shape
and elemental signatures of 60 adult individuals collected from two estuaries found in the Southeast
Bay of Biscay (Gernika and Plentzia). All samples were collected in June–July 2020. Otolith shape
analysis was determined using elliptical Fourier descriptors, while elemental signatures (Sr:Ca, Li:Ca,
Mg:Ca, Mn:Ca, Co:Ca, Ni:Ca, Cu:Ca and Ba:Ca) of whole sagittae were determined by inductively
coupled plasma mass spectrophotometry. Both natural tags were analyzed with univariate and
multivariate statistics to determine whether these signatures are geographically distinct and can be
used to assess the degree of separation between individuals. The data showed significant differences
in the otolith shape and elemental analyses, with canonical analysis of principal coordinates plots
identifying two different groups, each one belonging to each estuary of origin. Differences in whole
otolith elemental signatures between locations were driven by Sr:Ca, Li:Ca, and Ba:Ca. Sr:Ca and
Li:Ca ratios were higher in Plentzia than in Gernika, while Ba:Ca was higher in Gernika. The high
re-classification success rate using both tools obtained from stepwise linear discriminant function
analysis supports these findings and suggests that Gernika and Plentzia individuals passed enough
time in separated water compartments and should be regarded as two different population units.
This could suggest that the intersex condition in mullets from Gernika is due to life-long exposure to
xenoestrogens after homing during early larval development in that estuary, without migrations to
other estuaries.
Description
Keywords
Chelon labrosus Otoliths Shape and elemental signatures Population structure
Citation
Nzioka, A., Cancio, I., Diaz De Cerio, O. D., Ortiz-Zarragoitia, M., Pinto, E., Almeida, A., & Correia, A. T. (2022). Use of Otolith Shape and Elemental Signatures to Infer the Population Structure of the Thicklip Grey Mullet Chelon labrosus in the Southern Bay of Biscay. SIBIC 2022. https://doi.org/10.3390/blsf2022013071
Publisher
MDPI