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Live reef fish displaying physiological evidence of cyanide poisoning are still traded in the EU marine aquarium industry
Recently a new study has been published by the developers of the first non-invasive cyanide test. This research finds 15% of fish purchased from European wholesalers and screened show evidence of being collected illegally using cyanide. Link to study: Live reef fish displaying physiological evidence of cyanide... An earlier similar study in the US by For the Fishes, see: Assessing the prevalence of cyanide-caught fish... tested 51% of fish positive for the thiocyanate anion, a metabolite originating from the internal detoxification process displayed by any vertebrates poisoned by cyanide.
The quite different results might be explained by the difficulties in applying the test method and interpreting results, see Hertz et al. 2016.
Many questions remain open (how fish biomass, or the initial concentration of CN-, or the time window from exposure to screening, or temperature, or salinity, etc. affects the process) thus figures have to be treated with caution. With the test being cost and time intensive to conduct and results difficult to interpret, it will be tough to repeat such studies and extend sample size over a longer period and be representative.
There is another difference in results in regards of the species/families being tested positive for cyanide fishing by the two studies. The US study identified mainly damsels (family Pomacentridae) and one species of dartfish (family Microdesmidae) and one species of surgeonfish (family Acanthuridae) as being caught with cyanide. The more recent study in the EU indicates the "Families Chaetodontidae (butterflyfishes), Pomacanthidae (angelfishes) and Acanthuridae (surgeonfishes) were the ones displaying the highest number of specimens (3, 3 and 2, respectively) excreting SCN− at concentrations >10 µg L−1 at the end of the screening”.
While different, both results comply with the observation by exporters and local NGOs (e.g. LINI) that cyanide is mainly used for collecting solitary, fast swimming fish, also at greater depth, and small fish that can hide in coral crevices.
However, what we can conclude from both studies is that cyanide fishing remains a topic in the marine aquarium industry, even when a price increase in cyanide and more enforcement of the cyanide ban by local authorities led to reduced (or more secretive?) usage compared to 15 years ago…We also are aware that there is another, likely nowadays more important component to cyanide fishing: the Live Reef Fish Trade within Asia for the high priced food service market. However, it is the MAT with major markets in countries usually demanding ecological sustainability (US, EU) that is more likely to be interested in a solution and eradication of cyanide use in collecting their products and where it is unlikely that hobbyists are happy with being associated with illegal fishery products. It is thus a reasonable request to industry and hobbyists to engage and to invest in the development of a non-invasive cyanide test that is applicable in the field, using natural seawater and minimal preparations. Only when traders in producing (exporters) same as in market countries (importers) have a test at hand, they can exercise their own buying power and eradicate cyanide fishing from their supply chains. Certainly that will also require improved transparency in the flow of marine ornamentals from reef to retail, incl. at middlemen and export level, where fish from many different catch areas get mixed up and thus traceability back to the collector is not given.
Investing in transparency and ensuring purchased product is legal should be key interests of an ethical and sustainable marine aquarium trade.