Otolith geochemistry in young‐of‐the‐year peacock bass Cichla temensis for investigating natal dispersal in the Rio Negro (Amazon – Brazil) river system

Abstract

This study examined otolith geochemistry as a natural marker of natal origins in young‐of‐the‐year (YOY) Cichla temensis in the Negro River Basin of Brazil. We analysed trace element and isotopic composition of otoliths of YOY collected off spawning nests from the main stem and major tributaries. These were compared with regional bedrock geologic composition to explore underlying mechanisms of differences in otolith geochemistry. Our results suggest that spatial differences in otolith geochemistry can be used to distinguish natal origins based on 87Sr/86Sr, Sr/Ca and Ba/Ca ratios. This approach allowed us to correctly classify 99% of juvenile fish to their natal streams using cross‐validation in a linear discriminant function analysis (LDFA). Patterns of otolith isotopic composition correspond with patterns in regional geology as expected based on previously demonstrated correlations, although some fine‐scale spatial differences cannot be accounted for by available geologic information. These results demonstrate that otolith chemistry is valuable as a natural marker of natal origins in this system and suggest that inferences from geologic maps may be useful for interpreting movements based on otolith geochemical signatures. This information provides the basis for future work to investigate the early life history and spatial ecology of this important cichlid.

Movement patterns of adult peacock bass Cichla temensis between tributaries of the middle Negro River basin (Amazonas – Brazil): an otolith geochemical analysis

“…Given the degree of spatial heterogeneity in isotopic and elemental water chemistry inferred from YOY otolith results (Garcez et al . ), it is likely that most adults were captured in the general vicinity of where they were born (e.g. the same river).…”

“…For example, Garcez et al . () documented Paleoproterozoic intrusions in bedrock of the upper Preto River watershed. It is therefore possible that upstream tributaries in the Preto system have high 87 Sr/ 86 Sr and the pattern observed in the ablation transect of this individual reflects movement into one of these areas.…”

“…The degree of spatial heterogeneity in isotopic and elemental composition of rivers (as revealed in YOY otoliths) is remarkable and reflects heterogeneity in basin geology (Garcez et al . ), making this an excellent setting in which to apply otolith geochemical chronology to study fish movement. Additional research characterising not only spatial but also temporal variation in water chemistry in this system would enhance applications of this method for characterising the ecology of Cichla fisheries.…”

“…; Garcez et al . ). In river basins with sufficiently heterogeneous bedrock geology, tributaries may be distinguished by differences in elemental and/or isotopic water chemistry (Humston & Harbor ; Barnett‐Johnson et al .…”

Identification of nurseries areas of juvenile Prochilodus lineatus (Valenciennes, 1836) (Characiformes: Prochilodontidae) by scale and otolith morphometry and microchemistry

“…In relation to monitoring and use of otolith microchemistry, analyzing the geochemical origin of different studied elements, as well as the incorporation of isotopical relations could generate other markers of origin to study even adult individuals (Ashford & Jones, 2007;Walther & Thorrold, 2009;Niklitschek et al, 2010;Hegg et al, 2013Hegg et al, , 2015Garcez et al, 2015).…”