Gastric lavage as a non-lethal method for stingray (Myliobatiformes) diet sampling

Abstract

Understanding the trophic interactions of ecologically important mesopredators such as Myliobatiformes(stingrays) is vital, but, given their susceptibility to overexploitation, the collection of stomach contents for dietary analysis necessitates the use of non-lethal methods. We provide a detailed method of using gastric lavage to collect stomach contents from the 'Vulnerable' porcupine ray Urogymnus asperrimus at the St Joseph Atoll of the Amirantes Group, Seychelles. Rays were captured by hand, inverted and restrained while a plastic hose, connected to a bilge pump, was inserted into the stomach to flush out the contents. A high percentage (94.5%) of gastric lavage attempts resulted in the collection of stomach contents. There was no visual evidence of stress or short-term, post-release mortality and, given the success and relative ease of this technique, we conclude that the described method of gastric lavage is an effective, non-lethal means of obtaining stomach contents from stingrays.

Dietary composition and prey selectivity of juvenile porcupine raysUrogymnus asperrimus

“…Thus, 55 U . asperrimus were hand captured during daylight hours in May and June 2014 and subjected to non‐lethal gastric lavage for the collection of stomach contents (Elston et al , ). The fish were captured only on the reef flats because acoustic telemetry revealed that: U .…”

“…The capture and gastric lavage technique are detailed in Elston et al (), but briefly, U . asperrimus were approached from behind until close enough to lunge and place a gloved hand around the base of the tail.…”

“…Examining stomach contents remains one of the most reliable means of obtaining fine-scale taxonomic resolution of dietary items, despite the much cited drawback that it only provides a snapshot view of an animal's dietary composition (Pinnegar & Polunin, 1999;MacNeil et al, 2005;Kim et al, 2012). Thus, 55 U. asperrimus were hand captured during daylight hours in May and June 2014 and subjected to non-lethal gastric lavage for the collection of stomach contents (Elston et al, 2015). The fish were captured only on the reef flats because acoustic telemetry revealed that: U. asperrimus spend most of their time in this habitat, rarely moving into the deep lagoon (Elston, 2016); visual observations confirmed regular feeding in this habitat; hand capture in the deeper (3-7 m) and turbid inner lagoon of the atoll was not possible.…”

“…The capture and gastric lavage technique are detailed in Elston et al (2015), but briefly, U. asperrimus were approached from behind until close enough to lunge and place a gloved hand around the base of the tail. As this is the only dasyatid species to lack a spine on the tail, the method was safe and less harmful than a capture technique involving hook and line.…”

Effects of lipid and urea extraction on stable isotope values (δ13C and δ15N) of two batoids: A call for more species‐specific investigations

“…Ecologists typically use δ 13 C in animal tissues to determine the source of primary production in consumer diets (DeNiro and Epstein 1978;Tieszen et al 1983;Peterson 1999) and δ 15 N to assess the trophic level of consumers within a food web (DeNiro and Epstein 1981;Post 2002;Vanderklift and Ponsard 2003). The use of stable isotopes to trace consumer resource use is advantageous over traditional methods such as gut content analysis as stable isotope sampling can be less invasive (e.g., small tissue sample collected for stable isotopes vs. lethal sampling, O'Shea et al 2013 or gut flushing, Barnett et al 2010;Elston et al 2015 to collect stomach contents) and can shed light on resources used over longer time periods (Tieszen et al 1983;Hussey et al 2012a), as opposed to just the most recently used resources.…”