Temporal stability and rates of post‐depositional change in geochemical signatures of brown trout Salmo trutta scales

Abstract

This study investigates temporal stability in the scale microchemistry of brown trout Salmo trutta in feeder streams of a large heterogeneous lake catchment and rates of change after migration into the lake. Laser-ablation inductively coupled plasma mass spectrometry was used to quantify the elemental concentrations of Na, Mg, Mn, Cu, Zn, Ba and Sr in archived (1997-2002) scales of juvenile S. trutta collected from six major feeder streams of Lough Mask, County Mayo, Ireland. Water-element Ca ratios within these streams were determined for the fish sampling period and for a later period (2013-2015). Salmo trutta scale Sr and Ba concentrations were significantly (P < 0·05) correlated with stream water sample Sr:Ca and Ba:Ca ratios respectively from both periods, indicating multi-annual stability in scale and water-elemental signatures. Discriminant analysis of scale chemistries correctly classified 91% of sampled juvenile S. trutta to their stream of origin using a cross-validated classification model. This model was used to test whether assumed post-depositional change in scale element concentrations reduced correct natal stream classification of S. trutta in successive years after migration into Lough Mask. Fish residing in the lake for 1-3 years could be reliably classified to their most likely natal stream, but the probability of correct classification diminished strongly with longer lake residence. Use of scale chemistry to identify natal streams of lake S. trutta should focus on recent migrants, but may not require contemporary water chemistry data.

Assignment of Gilthead Seabream Sparus aurata to Its Origin through Scale Shape and Microchemistry Composition: Management Implications for Aquaculture Escapees

“…In contrast to scale shapes, which can be mediated both by genetic and environmental influences, scale chemistry can equally serve as a biogeochemical tag [17,18,26,37] and a pollution bioindicator of the habitat [38], as the hydroxyapatite or apatite-(CaOH) layer of scale can accommodate a wide range of elements directly from seawater [39]. In addition, several authors have noted the temporal stability and/or low rates of post-depositional alterations of scale-derived apatite of anadromous species [18,26,37,40], which allows correct fish classification back to their original environment.…”

Consistency of elemental and isotope‐ratio patterns across multiple scales from individual fish

“…Much of this work has employed a series of spots assayed from the core to edge of scales with a focus on elements that are useful for identifying movements across salinity or other chemical gradients (Coutant & Chen, 1993;Courtemanche et al, 2005;Borcherding et al, 2008). More recently, workers have used continuous ablation profiles across increments either on the surface of the scale or targeting the calcified external layer in a cross-sectioned scale (Clarke et al, 2007;Holá et al, 2009;Wolff et al, 2013;Campbell et al, 2015;Seeley et al, 2015;Ryan et al, 2016). The cross-sectional approach, as employed in this study, has the advantage of avoiding instrumental error associated with top-down ablations of highly rugose scales, particularly those that vary (Tables I and II); , scale b; , scale c. significantly in thickness from core to edge thereby causing problems for laser focusing in continuous transects.…”

Straying of brown trout in the catchment of a large New Zealand river evaluated by otolith microchemistry

“…Also using only YoY stage of brown trout for the study aimed to reduce variation due to physiological effects on otolith trace element composition, related to increasing size, maturation and reproductive state. Relatively limited interannual variability of otolith chemical signatures has been observed in juvenile brown trout and other salmonids in river catchments of New Zealand and elsewhere (Barnett‐Johnson et al, 2010; Martin et al, 2013; Ryan et al, 2016).…”