Discriminating estuarine nurseries for five fish species through otolith elemental fingerprints

Abstract

Chemical composition of otoliths may provide valuable information in establishing connectivity between nursery grounds and marine coastal stocks. Juveniles of the commercially important fish species Solea solea, S. senegalensis, Platichthys flesus, Diplodus vulgaris and Dicentrarchus labrax were captured in 8 estuarine nursery grounds along the Portuguese coast in July 2005. Concentrations of Li, Na, Mg, K, Mn, Ni, Cu, Zn, Sr, Cd, Ba and Pb were determined in whole juvenile otoliths using solution-based inductively coupled plasma mass spectrometry. Significant differences in the concentration of several elements were found between estuaries and species using ANOVA and MANOVA. Linear discriminant function analysis classified otolith fingerprints between estuaries for all species with good cross-validated results. Depending on the species, 70.2 to 92.0% of individuals were correctly assigned to their estuary of origin, with discrimination success varying with species, estuaries and number of estuaries in the analysis. Since accurate classification of juvenile fish to their nursery estuary was achieved, fingerprint analysis can be used as a natural habitat tag in assigning adult fish to their estuarine nursery. Ultimately the connectivity between Portuguese estuarine nursery grounds and coastal areas may be estimated, with possible implications for future fisheries and coastal management plans. KEY WORDS: Otolith microchemistry · Fingerprint · Juvenile fish · Estuary · Nursery · PortugalResale or republication not permitted without written consent of the publisher Mar Ecol Prog Ser 350: 117-126, 2007 (Kalish 1990, Tsukamoto & Arai 2001, (2) populations or stocks of fish (Campana 1999, Rooker et al. 2003 and (3) natal origin to near shore and estuarine habitats , Thorrold et al. 1998a, Dorval et al. 2005, Brown 2006a. This is possible due to some particular properties of otoliths reviewed by Campana (1999), Thresher (1999) and Elsdon & Gillanders (2003). Briefly, otoliths are metabolically inert and trace element uptake reflects the surrounding physical and chemical environment, although incorporation of some elements is affected by physiological regulation. Otoliths are deposited continually and contain daily and annual growth rings that can be used as life-history records reflecting habitat change through time, providing good natural tags of habitat use.Taking into account otolith properties, coastal fish that spent their juvenile period in estuaries are expected to have an otolith elemental composition which reflects their estuarine life period. The elemental composition of whole juvenile otoliths is commonly used to discriminate juvenile sites of origin as it is representative of the juvenile habitat (Thorrold et al. 1998a, Gillanders & Kingsford 2000, De Pontual et al. 2000, Dorval et al. 2005, Brown 2006b). Analysis of different regions of otoliths gives information on separate periods of ontogenetic development of the individuals. Point measurements done across daily or annual increments have be...

Otolith geochemistry discriminates among estuarine nursery areas of Solea solea and S. senegalensis over time

“…The results obtained confirm that otolith geochemistry in juvenile Solea solea and S. senegalensis are suitable natural markers to discriminate estuaries along the Portuguese coast and identify the nursery origin of adults, as suggested by Vasconcelos et al (2007bVasconcelos et al ( , 2008 (Leakey et al 2009) and to discriminate among 4 known nursery areas in the North Sea (Cuveliers et al 2010). However, none of these studies assessed the temporal variation of otolith chemistry.…”

“…through an effect of temperature on Mn:Ca ratios in otoliths of both species) to otolith composition. Similarly, the consistently high Mn:Ca ratios observed in the Mira estuary in both species and sampling years, as well as in an otolith chemistry study conducted in 2005 (Vasconcelos et al 2007b), suggests that juveniles are exposed to elevated dissolved Mn:Ca levels in the estuary. While we can only speculate as to the source of the Mn ions that were found in the juvenile sole otoliths, the only functioning ironmanganese ore mine in Portugal is located a few km north of the Mira estuary (Cercal).…”

“…among seasons, may confound spatial discrimination, leading to misinterpretation of geochemical data. The discriminatory power of otolith geochemistry in estuarine systems along the Portuguese coast and their applicability in connectivity studies has already been demonstrated (Vasconcelos et al 2007b. However, little is known about the inter-annual stability of otolith geochemistry from marine migrant species along the Portuguese coast, and temporal variation at smaller scales has yet to be investigated.…”

“…Otoliths have been widely used in age structure and growth studies and, more recently, to estimate population structure (e.g. Campana 1999, Thresher & Procter 2007, assess migration patterns (Hamer et al 2006, Fairclough et al 2011), identify natal origin or nursery areas (Vasconcelos et al 2007b, Clarke et al 2009) and retrospectively classify adults to their areas of origin (e.g. Thorrold et al 2001.…”

Large scale-variability in otolith microstructure and microchemistry: The case study ofDiplodus sargus sargus(Pisces: Sparidae) in the Mediterranean Sea

“…This is reflected in an increasing number of published papers that mostly deal with tropical regions and, to a lesser extent, with temperate regions (i.e. Forrester & Swearer 2002;Vasconcelos et al 2007Vasconcelos et al , 2008Standish et al 2008). …”