In a subsequent article, Bellwood investigated where cyanide might accumulate in the fishes' body other than the gastrointestinal tract, and what effects the drug might cause. Three test fish (called at the time but now reclassified as ) were subjected to a 1.84 ppm solution of potassium cyanide. This particular compound is an intentionally radioactive form of the drug C-14 potassium cyanide or KCN. The radioactive cyanide was used as a marker to easily locate where the cyanide would build up in the fishes' body. Two of the fish were starved for 24 hours prior to exposure; the other one was fed heavily before dosing. They were left in the solution until they were anaesthetized, plus an additional 30 seconds to ensure they were completely knocked out. Immediately afterward, the fishes were euthanized and their brain, gills, stomach, intestine, liver and spleen were removed and weighed. Each organ was then tested for radioactive cyanide.
The rates of photosynthesis and respiration of most plants are readily affected by the presence of added chemicals. The action of some substances that have strong affinities for certain components of the photosynthetic and respiratory apparatus is specific and effective. The skillful use of such substances may help to differentiate the component reactions of photosynthesis. Warburg initiated the work by using potassium cyanide on the green algae, Chlordla pyrenoidosa (1). Gaffron has used many inhibitory effects to explain the complex chemistry of photosynthesis (2--4). Greenfield has made a detailed study of the inhibitory effects of inorganic compounds on photosynthesis in Chlorella (5). Except for a few specific cases, little is known concerning the various ways in which the different inhibitors affect the separate processes of photosynthesis and respiration. The present work was intended as a qualitative exploration of the effects of some common inhibitors on the rates of photosynthesis and respiration in ChloreUa pyrenoidosa. Some less studied inhibitors were included in the study while taking the common inhibitor,
There is another important point to be gleaned from this study. The fishes that were exposed to cyanide took 821 ± 86 seconds to recover fully. But, 19% of those fishes failed to recover at all and perished from the cyanide exposure protocol. Additionally, in pilot studies performed prior to this study, fishes were exposed for two minutes. All of these fish failed to recover and perished. So clearly, cyanide can be deadly depending on the concentration and exposure time.
Next, they conducted a second series of experiments in which fishes were exposed to 25 or 50 ppm cyanide, but all groups (again, ten fish per group) were treated for only 60 seconds. They added some stressors to some of these groups of fishes to see what results, if any, would occur. There were two groups of fishes; one was exposed to 25 ppm while the other was exposed to 50 ppm, but neither had any additional stress imposed. Another two groups of 25 and 50 ppm exposed fishes were bagged in two liters of seawater for ten minutes before being returned to their aquariums, to simulate transport. The final two groups were intentionally chased with a hand net in their tanks for 10 minutes two and one half weeks after exposure, simulating a retail experience (although, speaking as a former local fish store employee, if you can't catch a damsel from a retail tank in less than one minute, you deserve to be handed your walking papers). None of the groups experienced any mortalities except for the group exposed at 50 ppm for 60 seconds that was bagged. All of those fishes died.
In this study 154 fish (Pomacentrus coelestis) were collected with barrier and hand nets from the Great Barrier Reef, Australia. Of these, ten fish were immediately killed, and then they performed necropsies taking measurements of various intestinal parameters as a pretreatment control group. The remaining 144 fish were split into nine equal groups of sixteen each for further testing. The first group was a control which was handled as little as possible. The second group was another control group that were handled just like the fish that would be exposed to cyanide, but instead of immersing them in a cyanide water bath, they were simply dunked into a separate container of seawater. The third group was exposed to cyanide at a concentration of 10 ppm for a mean time of 85 seconds plus an additional 5 seconds to ensure a complete effect. The fourth group was a stress group. Whereas all unstressed fishes had a 1,000 cm pile of live rock rubble in their tanks, the stressed fish had only one piece of rubble. Additionally, each day the piece was removed for 30 seconds. The fifth group was deprived of any food for the duration of the experiment, 16 days. Then, there were various combination treatments. At the end of the study period, all fish were euthanized, dissected and their intestinal tracts were examined. The results are seen in Table 1 below.
Second, use the tips and information provided here to avoid supporting the cyanide industry. When you buy wild-caught fish, do everything you can to ensure that they were not captured using this drug. Reward with your purchases the good vendors who sell only healthy, net caught fishes, and punish the bad apples who specialize in cheap, suspect animals by boycotting their stores. I have no sympathy for, and will not be kept up at night over, the thought of unscrupulous or ignorant shop owners going out of business because no one will purchase their suspect animals. It is time to cull the herd and drive these people out of the industry.
For one thing, it's important to note that collectors are typically using rather crude squirt bottles for administering cyanide. As such, they are severely limited in controlling the dosage delivered (Hall & Bellwood, 1995 and Hanawa , 1998). Additionally, there is one reference that I found where actual squirt bottles were confiscated and tested (Pet & Djohani, 1998). They showed that the bottles contained dosages of 762.50, 1251.00, 1401.00, and 2017.50 ppm. So, the collectors themselves don't always use a consistent dosage. Moreover, it should be understood that the second this mixture begins to emerge from the squirt bottles, it is instantly diluted with the surrounding ocean water, further changing is concentration. We can still divine a few things, however, by using some common sense. From a collector's standpoint, the goal would be to catch the greatest number of fishes in the shortest amount of time while having the lowest initial mortalities, thereby maximizing profitability. With that frame of mind in place, the early Bellwood article's speculation on dosages seems dubious to me. At 1-5 ppm, it took 2-3 minutes to knock out the fishes. Two to three minutes seems like an awfully long time for a collector to wait to capture a fish. I imagine that a scared and frightened reef fish could travel a great distance from the cyanide fisherman in that amount of time. These fish could easily become quite problematic to locate before the anesthetic effect wore off, not to mention how difficult it would be to maintain that concentration in the open ocean's currents for those periods of time. The same applies to the later Hall & Bellwood paper. On average, it took 85 seconds to anesthetize the fish in that study. Again, that seems too long to me. The Hanawa (1998) paper showed that fish could be anesthetized for capture in as little as 10 seconds with 25 or 50 ppm dosages. And it was not until these dosages were prolonged for one to two minutes that the fish suffered 100% initial mortalities. So dosages of 25-50 ppm delivered in short bursts seem the most probable to me. That does not mean, however, that surrounding corals could not be harmed by these dosages. The Cervino (2003) paper showed mortalities occurred even at the relatively low 50 ppm concentration studied. Additionally, the initial plume of cyanide might be considerably stronger such that once it is diluted by ocean water that concentration that the target fishes are exposed to is sufficient to anaesthetize them. So clearly, from the research performed to date we can see that fishes and corals can be killed by cyanide exposure depending on the concentration used and the exposure's duration, and that the most likely dosage for effective catch rates would be within this toxic range.
Potassium cyanide, which preferably inhibits the Blackman reaction in photosynthesis, decreases the light intensity at which the contrast sensitivity starts to decrease.