Proceedings of the International Cyanide Detection Testing Workshop

metabolism by blocking the key enzyme
system, cytochrome oxidase (Metzler, 2001),
and blocks enzymatic pathways in the liver
(Solomonson, 1981). Some of the effects,
such as blocking enzyme functions, are
irreversible and lead to the death of the fi sh
(Way, Leung et al., 1988). Once inside the
fi sh tissue, cyanide reacts with thiosulfate in
the presence of rhodanese to produce the
comparatively nontoxic thiocyanate. The
thiocyanate is excreted in the urine. Rapid
detoxifi cation enables animals, such as fi sh,
to ingest high, sub-lethal doses of cyanide
(Eisler, 1991).
Chu (Chu, Liu et al., 2001) used attenuated
total reflectance and transform infrared
microspectroscopy to evaluate the molecular
mechanisms of cyanide toxicity. The results
showed changes in structural conformation
of biomolecular/protein components of gill
tissue and ultimate loss of function.
It is not possible to defi nitively identify the
half-life of cyanide in marine fi sh. However,
because of the volatile nature of cyanide,
it is known that cyanide breaks down very
rapidly (Logue, Kirschten et al., 2005). This is
particularly true in fi sh and even more so in a
salt-water environment. Logue et al. (Logue,
Kirschten et al., 2005) state that depending
on the route and duration of exposure, in
humans cyanide is typically eliminated from
blood within 20 minutes post-exposure.
Exposure of marine fish to a 10 μM
concentration of potassium cyanide for 15
minutes is considered to be a sub-lethal dose
(Mak, Yanase et al., 2005). Preliminary tests
to examine cyanide concentrations present
in marine fi sh after exposure to cyanide
identifi ed a range of 0.04 ppm to 1.02 ppm
(Hodgson, pers. com.).
98
Eisler (Eisler, 1991) reported baseline levels
of cyanide in freshwater fi sh at less than 1
μg/kg or 1 ppb fresh weight in gills. However,
values up to 50 μg/kg occurred occasionally
in fi sh found in natural streams (Eisler, 1991).
Cyanide concentrations in fi sh from streams
that were deliberately poisoned with cyanide
ranged between 10 and 100 μg/kg (10-100
ppb) total cyanide whole body fresh weight
(Wiley, 1984). Total cyanide concentrations in
gill tissues of salmonids under widely varying
conditions of temperature, nominal water
concentrations, and duration of exposure
ranged from about 30 μg/kg fresh weight
to greater than 7,000 μg/kg (Holden and
Marsden, 1964; Eisler, 1991).
What Does Cyanide Do to the Coral Reef?
It is even more diffi cult to assess the impact
of cyanide use on the reef environment.
Ultimately, the dose of cyanide experienced
by corals and surrounding organisms is
a function of cyanide concentration, the
proximity to target fi sh to the cyanide source,
and the local hydrological conditions. Under
conditions of cyanide fi shing, corals are likely
to experience initially high (10 –1 to 10 –2 M),
rapidly fl uctuating concentrations of cyanide
that ultimately fall to very low levels (10 –5 to
10 –6 M) (Jones and Steven, 1997). In some
cases, water currents can dissipate cyanide and
carry the toxin away from the reef. However,
research using dyed water showed that water
can be trapped in stagnant zones behind coral
heads (Wolanski and Jones, 1980). Under
such conditions, cyanide fi shing could result
in coral mortality (Jones and Steven, 1997).
Early research showed that photosynthesis
and calcification of staghorn corals were
inhibited at concentrations greater than 1
x10 –5 M cyanide (Chalker and Taylor, 1975).
More recently, Jones and Steven (Jones and
Steven, 1997) showed that respiratory rates
of Pocillopora damicornis were inhibited by