Otolith fingerprints as natural tags to identify juvenile fish life in ports

Abstract

The construction of ports has caused substantial habitat destruction in coastal areas previously used as nursery grounds by many fish species, with consequences to fish stocks. These artificial coastal areas might provide alternative nursery habitats for several species for juvenile fish abundances and growth in ports, although their contribution to adult stocks had never been estimated. The variability of otolith composition in the juveniles of two Diplodus species was investigated in three contrasting port areas and two adjacent coastal juvenile habitats of the Bay of Toulon (northwestern Mediterranean) in order to determine the possible use of otolith fingerprints as natural tags for the identification of juvenile fishes in ports. The global accuracy of discrimination between ports and coastal areas was very high (94%) irrespective of species, suggesting that otolith fingerprints can be used with confidence to retrospectively identify past residency in the ports of this bay. However, Ba was systematically the most discriminating element, since its concentrations in otoliths were generally higher outside ports than in inside them, probably due to river runoff. Moreover, otolith signatures varied greatly by species and between sampling sites. Furthermore, although Cu and Pb concentrations in water were at least 2.3-34-fold higher inside ports than outside, this was not consistently reflected in fish otoliths, confirming that spatial differences in otolith concentrations depend on the species and do not directly reflect differences in environmental contamination levels. Therefore, it seems unlikely that otolith microchemistry could provide a universal fingerprint capable of discriminating ports from other coastal areas. Nevertheless, the contribution of ports to adult fish populations can be determined well by establishing a library of otolith fingerprints for all juvenile habitats.

Otolith microchemistry: a useful tool for investigating stock structure of yellowfin tuna (Thunnus albacares) in the Indian Ocean

“…Rooker et al 2008bRooker et al , 2016Wells et al 2012;Macdonald et al 2013). However, in recent years, machine learning techniques have emerged as promising classification tools in otolith-related studies (Zhang et al 2016;Tournois et al 2017;Bouchoucha et al 2018). The accuracy of each technique will depend on the nature of the data analysed, and the results of this study agree with those of recent studies encouraging the use of machine learning methods when otolith chemical data are not multivariate normal or exhibit skewed distributions (Mercier et al 2011;Jones et al 2017).…”

Population Connectivity and Genetic Assessment of Exploited and Natural Populations of Pearl Oysters within a French Polynesian Atoll Lagoon

“…Nowadays, multiple techniques can be used to characterize the geographical and demographical origin of individuals: direct tagging of individuals using fluorochromes, dispersal modelling, [7,[12][13][14][15][16] or parentage analysis through the use of genetic markers [17,18]. Genetic markers also have the advantages to inform about the putative genetic diversity of the parental populations as well as demographic parameters such as the estimated number of adults reproducing in a population.…”

Elemental Fingerprints of Sparus Aurata Otoliths – Insight Into the Diversity of Nursery Habitats

“…Testing for natal homing is very challenging due to the di culty in tracking all life stages 44 . Generally, otolith chemistry is affected by water chemistry 35,[49][50][51] , and it has proved useful in examining movements among life stages in regions where there is detectable spatial variation 37 . Considering Sparus aurata, previous studies showed that juveniles occupy seasonally contiguous lagoons 10,25,27,32,34 , while adults inhabited open sea waters 27,28,32 .…”

“…The accurate discrimination by multivariate analyses indicated that S. aurata specimens originating from speci c geographic areas in the Adriatic Sea have distinct elemental signatures that potentially enable their re-allocation to speci c nursery habitats along the coast. Multivariate analyses have become a desirable tool for such purposes, since they are capable of separating different perturbations from natural spatiotemporal variability displayed by most populations 67 with an analytical procedure 52,49,58 . However, the lower rate of success (35-45%) achieved in differentiating between the analysed nursery areas may be driven by two potential mechanisms.…”