Stable isotope analysis of eye lenses from invasive lionfish yields record of resource use

Abstract

Patterns of stable isotopes recorded in metabolically stable, serially synthesized, structures such as eye lenses can yield robust descriptions of resource use across the life histories of individual fish. We performed stable isotope analysis of eye lenses sampled from invasive lionfishes Pterois spp. and a potentially competitive native mesopredator, the graysby Cephalopholis cruentata, to compare lifelong patterns of trophic resource use on a coral reef ledge in Biscayne National Park, Florida, USA. In both lionfishes and graysby, stable isotope values increased logarithmically with eye-lens radius, likely reflecting increases in trophic position with growth. Tissue samples toward the interior of the lens were the most isotopically similar between lionfish and graysby, suggesting interspecific resource use overlap may be strongest in smaller fish. We observed substantial variation in isotopic chronologies around the underlying logarithmic trend within individual fish, potentially driven by patterns of movement across measured environmental isotopic gradients, intraspecific variation in resource use specificity, or other ecological variables of interest. These results are the first to describe patterns of size-structured resource use across the life of individual lionfish, an important objective for researchers studying the interactions of this highly invasive species with the surrounding ecological communities. Additionally, through this example, we illustrate analytical approaches and considerations for the application of eye-lens stable isotope analysis to the study of vertebrate ecology.

Advancing diet reconstruction in fish eye lenses

“…Understanding how aquatic animals with complex behaviours and life cycles utilize diverse habitats is fundamental to their conservation (Hobson, 2008; Rubenstein & Hobson, 2004; Runge et al., 2014). The ability to track ontogenetic diet shifts in a single tissue provides key information on aquatic food webs, individual foraging ecology and contributions of habitats to aquatic ecosystem productivity (Curtis et al., 2020; Kurth et al., 2019; Liu et al., 2020; Meath et al., 2019; Quaeck‐Davies et al., 2018; Simpson et al., 2019; Vecchio & Peebles, 2020; Wallace et al., 2014; Xu et al., 2019).…”

“…This is due to otoliths being composed primarily of calcium carbonate and inorganic forms of carbon, with minimal protein (<1-10%), which limit these structures as dietary isotopic time-series recorders (see exceptions, Weber et al 2002;Johnson et al 2012;Lueders-Dumont et al 2018, Bell-Tilcock et al, unpublished). SIA in protein-rich eye lenses of fish tracks dietary isotopic values over a lifespan (Wallace et al 2014;Tzadik et al 2017;Quaeck-Davies et al 2018a;Kurth et al 2019;Simpson et al 2019;Curtis et al 2020;. Fish eye lenses are small, onion-like spheres composed of layers (laminae), forming continuously over life, and are no longer undergoing protein synthesis once fully formed (Nicol, 1973;Wride 2011;Greiling and Clark 2012;Wallace et al 2014;Tzadik et al 2017;Granneman, 2018;.…”

“…SIA in protein‐rich eye lenses of fish tracks dietary isotopic values over a lifespan (Curtis et al., 2020; Kurth et al., 2019; Quaeck‐Davies et al., 2018; Simpson et al., 2019; Tzadik et al., 2017; Vecchio et al., 2021; Vecchio & Peebles, 2020; Wallace et al., 2014). Fish eye lenses are small, onion‐like spheres composed of layers (laminae), forming continuously over life, and are no longer undergoing protein synthesis once fully formed (Granneman, 2018; Greiling & Clark, 2012; Nicol, 1973; Tzadik et al., 2017; Vecchio, 2020; Wallace et al., 2014; Wride, 2011).…”

Compound-Specific Nitrogen Isotope Analysis of Amino Acids in Eye Lenses as a New Tool to Reconstruct the Geographic and Trophic Histories of Fish

“…A relationship between lens size and FL was established as a reference framework (Figure 3) to assign the isotopic trends observed in interior lens tissues to specific life stages or size classes. Lens-length relationships are generally linear (Quaeck-Davies et al, 2018;Simpson et al, 2019;Curtis et al, 2020). To establish this relationship for chub mackerel, length and lens measurements across a size distribution (n = 46; FL 41-370 mm; Supplementary Table 1) were used.…”

“…The δ 15 N values are lower in the subtropical Kuroshio region than in the subarctic Oyashio region because the subtropical Kuroshio is influenced by N fixation inputs (Yoshikawa et al, 2018). Another feature expected to characterise isotopic chronologies from fish eye lenses is an increase in TP with growth (Simpson et al, 2019;Curtis et al, 2020). Such ontogenetic shifts are common in fish (Romanuk et al, 2011), primarily due to a widening of gape size that allows consumption of larger prey (Arim et al, 2010).…”