Abstract
Variations in otolith elemental composition are widely used to reconstruct fish movements. However, reconstructing habitat use and environmental histories of fishes within estuaries is still a major challenge due to the dynamic nature of these coastal environments. In this study, we performed a laboratory experiment to investigate the effects of variations in salinity (3 levels; 5, 18, 30) and temperature (2 levels; 16oC, 21oC) in the otolith elemental composition (Mg:Ca, Mn:Ca, Sr:Ca, Ba:Ca) of juvenile Senegalese sole Solea senegalensis. Temperature and salinity treatments mirrored the natural conditions of the estuarine habitats generally occupied by juvenile Senegalese sole, thereby providing information on the applicability of otolith microchemistry to reconstruct habitat use patterns within estuarine nurseries, where individual fish move across complex salinity and temperature gradients. While Sr:Ca and Ba:Ca in otoliths were both positively related to salinity, no temperature effect was observed. Partition coefficients, proxies for element incorporation rates increased with increasing salinity for Sr (DSr) and Ba (DBa). In contrast, salinity and temperature had little influence on otolith Mn:Ca and Mg:Ca, supporting physiological control on the incorporation of these elements. Our results are a stepping stone for the interpretation of otolith chemical profiles for fish collected in their natural habitats and contribute to better understanding the processes involved in otolith element incorporation.
Highlights
Estuaries are key nursery areas for many marine fish (Beck et al, 2001; Sheaves et al, 2006; Nagelkerken et al, 2013), including flatfishes (Le Pape et al, 2003; Martinho et al, 2010; Vasconcelos et al, 2011; Freitas et al, 2012)
Otolith Chemistry in Juvenile Flatfish sense, development of management and protection plans should take into account connectivity between the distinct ontogenetic habitats, as connectivity is directly linked to population dynamics, productivity and resilience to harvest (Cowen et al, 2000; Thorrold et al, 2001; Pihl et al, 2002)
Juvenile S. senegalensis increased in total length in all treatments during the 98-day experimental procedure: initial average TL 9.8 ± 1.1 cm; final average TL 11.2 ± 1.1 cm (Figure 1)
Summary
Estuaries are key nursery areas for many marine fish (Beck et al, 2001; Sheaves et al, 2006; Nagelkerken et al, 2013), including flatfishes (Le Pape et al, 2003; Martinho et al, 2010; Vasconcelos et al, 2011; Freitas et al, 2012). These species often have complex life cycles, which include migrations between coastal areas and inshore nurseries of up to 100s of kilometers. A suite of other elements, such as magnesium (Mg) or manganese (Mn), reflect multiple environmental and physiological responses of individual fish to the surrounding ambient water conditions and can aid in environmental reconstructions (Martin and Thorrold, 2005; Tanner et al, 2013a)
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