Non‐lethal sampling for the stable isotope analysis of the critically endangered European eel Anguilla anguilla: how fin and mucus compare to dorsal muscle

Abstract

Ecological studies on the critically endangered European eel Anguilla anguilla often incorporate stable isotope analysis that typically uses dorsal muscle sampled from euthanised eels. To minimise the lethal sampling of imperilled populations, fin tissue and/or epidermal mucus can provide non‐lethal alternatives to muscle. The results here indicate that δ13C and δ15N values of both eel fin and mucus are not significantly different from those of muscle and can be applied directly in comparative SI studies.

New insights into detecting alizarin from autofluorescence in marked glass eels

“…While extracting the pectoral fins can affect the growth, stability, propulsion and the survival of the fish 16 , 17 it is possible to extract a caudal fin clip without affecting the fish survival. Numerous studies have developed non-lethal detection method with caudal fin clips for small fish (> 50 mm) 1 – 4 , 6 , 18 and already in European eels 7 . The caudal can indeed regenerate rapidly in fish and the caudal fin clip results in low mortality in early stages 2 , 4 , 7 , 17 – 21 .…”

“…Numerous studies have developed non-lethal detection method with caudal fin clips for small fish (> 50 mm) 1 – 4 , 6 , 18 and already in European eels 7 . The caudal can indeed regenerate rapidly in fish and the caudal fin clip results in low mortality in early stages 2 , 4 , 7 , 17 – 21 . These results are promising for developing a non-lethal alizarin detection method in marked eels using caudal fins 7 .…”

“…The caudal can indeed regenerate rapidly in fish and the caudal fin clip results in low mortality in early stages 2 , 4 , 7 , 17 – 21 . These results are promising for developing a non-lethal alizarin detection method in marked eels using caudal fins 7 .…”

“…Studies have extensively demonstrated how to detect fluorescent stains in the fins of marked fish (guppie 1 ; zebrafish 2 ; trout 3 ; tilapia 4 ; sturgeon 5 ). In eels, the fin tips are widely used in genomics studies 6 and recently, in stable isotope studies 7 . However, eel fins are not yet employed in alizarin mark detection studies.…”

Caudal fin as a proxy for dorsal muscle for nutrient enrichment monitoring using stable isotope analysis: the case of Gerres filamentosus and G. oyena from mangrove creeks of Tanzania

“…Despite the widespread use of fish in ecological studies using the stable isotopes approach, the use of dorsal muscles extracted from fish -an invasive method that results in the death of the specimens, limits their applicability in species of concern such as rare and endangered species, or when large sample sizes and replicates are required. This has prompted research into plausible non-lethal sampling methods that may be used as a proxy for dorsal muscle, with various studies selecting fish fins, fish scales, mucous, liver, plasma, and red blood cells as candidates (Boardman et al, 2022;Church et al, 2009;Hayden et al, 2015;Hayden et al, 2017;Matley et al, 2016;McIntosh and Reid, 2021;Tronquart et al, 2012).…”