Linking otolith microchemistry and dendritic isoscapes to map heterogeneous production of fish across river basins

Abstract

Production patterns of highly mobile species, such as anadromous fish, often exhibit high spatial and temporal heterogeneity across landscapes. Such variability is often asynchronous in time among habitats, which stabilizes production at aggregate scales of complexity. Reconstructing production patterns explicitly in space and time across multiple scales, however, remains difficult but is important for prioritizing habitat conservation. This is especially true for fishes inhabiting river basins due to long-range dispersal, high mortality at early life stages, complex population structure and elusive life history variation. We develop a new approach for mapping production patterns of Pacific salmon across a large river basin by integrating otolith microchemistry and dendritic isoscape models. The geographically continuous Bayesian assignment framework presented here yielded high accuracies (>90%) and relatively high precisions (precisions <4%; i.e., assignment areas of <530 river km of the 13 100 km total river length) when used to determine the natal source of known-origin juvenile Chinook salmon captured throughout the study region. Integrating these methods enabled us to base estimates of provenance and habitat use of individuals on a per location basis using strontium isotopic data throughout the continuous spatial domain of a river network. Such a framework provides substantial advantages over the more common nominal approach to employing otolith microchemistry to reconstruct movement patterns of fish. In doing so, we reconstructed the spatial production patterns of adult Chinook salmon returning to a large watershed in Bristol Bay, Alaska and illustrate the power of such an approach to conservation efforts.

The art of otolith chemistry: interpreting patterns by integrating perspectives

“…This model was further improved by Bataille et al (2014) through refinements of model components including siliciclastic sedimentary rock submodel improvements to account for grain recycling, and an updated weathering model for Alaska that incorporated permafrost and glacial processes that can affect Sr flux at higher latitudes. These models point to the need to incorporate both general isotope systematics as well as regional hydrodynamic processes to more accurately estimate the dissolved 87 Sr/ 86 Sr present in streams and rivers that fish inhabit, thereby allowing highly accurate estimation of natal origins and migration patterns of freshwater and diadromous fishes (Brennan and Schindler 2017).…”

Simultaneous determination of87Sr/86Sr and trace-element data in otoliths and other sclerochronological hard structures

“…Fish otoliths grow in sequential layers of biogenic aragonite, preserving trace elements and isotopes unique to the environments the fish inhabits through its life (Campana 1999, Campana andThorrold 2001). These chemical tracers have been used to uncover the population structure of fish populations , Muhlfeld et al 2012, Brennan and Schindler 2017, as well as the details of their migratory paths (Hegg et al 2015, 2019, Sturrock et al 2015b, Chittaro et al 2019, sometimes with incredible precision on the landscape (Hamann and Kennedy 2012). Otoliths thus provide a high-resolution, broad scale, dataset of location, growth, and ontogeny across the life of the organism which is not possible in using tagging or tracking technologies (Hegg et al 2018).…”

Commercial traceability of &lt;i&gt;Arapaima&lt;/i&gt; spp. fisheries in the Amazon basin: can biogeochemical tags be useful?

“…The methodological assumptions to discriminate fish stocks are based on (i) the isotopic heterogeneity among stocks and (ii) the low mobilization rates in the analyzed tissue (Kerr and Campana, 2013). Isotopic information can be extracted from calcified structures of fishes (scale, otolith, or vertebrae) in order to preserve fish integrity for commercial use and eventually reconstruct fish life history (Campana, 1999;Pouilly et al, 2014;Pracheil et al, 2014). Strontium isotopes have been used as an origin tracer of food products because of their robust response in terms of origin authenticity and fraud detection (Baffi and Trincherini, 2016).…”

“…On the other hand, carbon isotopes have been used to distinguish farmed and wild fishes according to feeding patterns (Rojas et al, 2007;Turchini et al, 2009). Fish otoliths, or ear bones, are calcified structures that grow continually and record ambient conditions throughout a fish's life (Campana, 1999). Since Sr isotopes in otoliths are not reabsorbed and do not fractionate during biological uptake, the isotopic ratio of this element is a robust geographic marker (Kennedy et al, 2000;Kerr and Campana, 2013;Pouilly et al, 2014).…”