Excreted thiocyanate detects live reef fishes illegally collected using cyanide--a non-invasive and non-destructive testing approach
Authors: Peter J Rubec
Ricardo Calado
Teresa A P Rocha-Santos
Marcela C M Vaz
Armando C Duarte
Rui J M Rocha
Ruth Pereira
Isabel Lopes
Journal: PLoS ONE (2012)
Discipline: Multidisciplinary
Keywords: Cyanide fishing; marine fish; coral reefs; Southeast Asia; marine aquarium trade
Affiliations: Departamento de Biologia & CESAM, Universidade de Aveiro, Campus Universitário de Santiago, Aveiro, Portugal.

Abstract:  Cyanide fishing is a method employed to capture marine fish alive on coral reefs. They are shipped to markets for human consumption in Southeast Asia, as well as to supply the marine aquarium trade worldwide. Although several techniques can be used to detect cyanide in reef fish, there is still no testing method that can be used to survey the whole supply chain. Most methods for cyanide detection are time-consuming and require the sacrifice of the sampled fish. Thiocyanate anion (SCN(-)) is a metabolite produced by the main metabolic pathway for cyanide anion (CN(-)) detoxification. Our study employed an optical fiber (OF) methodology (analytical time &lt;6 min) to detect SCN(-) in a non-invasive and non-destructive manner. Our OF methodology is able to detect trace levels (&gt;3.16 µg L(-1)) of SCN(-) in seawater. Given that marine fish exposed to cyanide excrete SCN(-) in the urine, elevated levels of SCN(-) present in the seawater holding live reef fish indicate that the surveyed specimens were likely exposed to cyanide. In our study, captive-bred clownfish (Amphiprion clarkii) pulse exposed for 60 s to either 12.5 or 25 mg L(-1) of CN(-) excreted up to 6.96±0.03 and 9.84±0.03 µg L(-1) of SCN(-), respectively, during the 28 days following exposure. No detectable levels of SCN(-) were recorded in the water holding control organisms not exposed to CN(-), or in synthetic seawater lacking fish. While further research is necessary, our methodology can allow a rapid detection of SCN(-) in the holding water and can be used as a screening tool to indicate if live reef fish were collected with cyanide. 

Retracted: No

PubPeer comments:
 This paper has been refuted by two publications, with both attempts to replicate the experiment and also a mathematical examination of the data presented in the paper. It is clear that the data presented in this paper is not possible. Refuted by: Herz et al. 2016 https: coastfish.spc.int en publications bulletins live-reef-fish 460-live-reef-fish-information-bulletin-21 Breen et al. 2018 https: doi.org 10.1371 journal.pone.0196841 A simple examination of Figure 2 is very disturbing. Figure 2 from Vaz et al. 2012 shows averages u00b1 standard error. Control and two treatments. ![img] Notice the tiny error bars presented in the figure. This suggests a high level of precision between replicates. In fact, we have tried to replicate this level of precision but it is not possible even with analytical standards. The authors have never provided any explanation of how they created the dataset. The corresponding author and lead author have no access to the original data from the optical fiber sensor. ,