Life‐history studies by non‐lethal sampling: using microchemical constituents of fin rays as chronological recorders

Abstract

Chemical properties of fin rays were investigated in nine fish species to test whether life-history characteristics can be analysed using a non-lethal and minimally invasive methodology. Fish specimens from public aquariums were acquired after fishes died in captivity. Analyses concentrated on exploring the differences between the wild and captive life periods of each fish, which were known from aquarium records. Differences between the two life periods were observed in both the trace-element and stable-isotope compositions of the chemical matrix of the fin ray. Trace-element concentrations in fin rays were compared with those in otoliths using measures of resolved variance and cross-correlation to test the assumption of conserved matrices in the fin ray. Divalent ions and positively charged transition metals (i.e. Fe and Co) had strong associations between the two structures, suggesting conservation of material. Stable-isotope values of δ C and δ N differed between the wild and captive life periods in most of the fishes, also suggesting conserved matrices. δ C and δ N were derived from the organic matrix within the fin ray, which may present a stable-isotope chronology. Future studies can use these chronologies to study diet and movement trends on a temporal scale consistent with the entire lifetime of an individual.

Frontiers in otolith chemistry: insights, advances and applications

“…Tzadik et al . () investigated elemental and isotope ratio profiles across fin rays of a number of species and found strong concordance in patterns of some constituents between otoliths and fin rays from the same individuals, supporting the utility of fin rays as a non‐lethal alternative to sampling otoliths. Lifetime patterns of organic stable isotope ratios (δ 15 N and δ 13 C) were also consistent with known individual histories, suggesting that these structures with higher organic fractions offer additional insight into dietary chronologies that are analytically difficult to obtain from otoliths themselves.…”

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

“…: +1 361 825 4168; email: benjamin.walther@tamucc.edu are imperiled, subject to catch-and-release fisheries or where mortality must otherwise be avoided. The need for non-lethal analogues to otoliths has prompted investigation into alternative structures that may provide comparable growth and chemical histories, including fin rays, fin spines, scutes and scales (Gillanders, 2001;Arai et al, 2002;Smith & Whitledge, 2011;Altenritter et al, 2015;Tzadik et al, 2017b).…”

Identification of Hatchery‐Reared Lake Sturgeon Using Natural Elemental Signatures and Elemental Marking of Fin Rays

“…; Tzadik et al. 2017b; Warren‐Myers 2018b). Naturally occurring trace elements (e.g., Sr 2+ , Ba 2+ , Mg 2+ , Mn 2+ , and Zn 2+ ) are incorporated by fish from the surrounding aquatic environment and are substituted for calcium (Ca 2+ ) in hydroxyapatite (Ca 10 [PO 4 ] 6 [OH] 2 ) in bone material or for calcium carbonate (CaCO 3 ) in otoliths due to their similar chemical properties (i.e., atomic size and valence charge; Campana ; Loewen et al.…”

“…A variety of marking techniques is available, including passive, electronic, and biological tagging, each with their own distinct advantages and disadvantages (Pine et al 2003;Cadrin et al 2004;Drenner et al 2012;Warren-Myers et al 2018a). As an alternative to physical tags, elemental signatures in hard structures (i.e., otoliths, fin rays, vertebrae, and eye lenses) of fish have proven useful as natural markers to reconstruct environmental life histories and identify the natal origin or nursery habitats of individuals (Thorrold et al 2001;Tzadik et al 2017b;Warren-Myers 2018b). Naturally occurring trace elements (e.g., Sr 2+ , Ba 2+ , Mg 2+ , Mn 2+ , and Zn 2+ ) are incorporated by fish from the surrounding aquatic environment and are substituted for calcium (Ca 2+ ) in hydroxyapatite (Ca 10 [PO 4 ] 6 [OH] 2 ) in bone material or for calcium carbonate (CaCO 3 ) in otoliths due to their similar chemical properties (i.e., atomic size and valence charge; Campana 1999;Loewen et al 2016;Tzadik et al 2017a).…”