By Ken Kristian

Recently, worried professional fishing guides and deeply concerned anglers in British Columbia Canada contacted the Steelheader News sounding an environmental alarm with a rash of reports siting Fraser and Harrison River sturgeon stocks inflicted with mysterious black spots.

A possible explanation to the mystery has been offered by Fisheries biologists and some local BC anglers who maintain that the black spots seen on Fraser and Harrison River sturgeon may be caused by a parasite called a fluke, which burrows into the skin of fish resulting in black pigment (about pinhead size) forming in surrounding tissue. However, with the size of black spots now found on fish ranging between .5 to 2 cms, there appears to be a growing body of evidence pointing directly toward possible prolonged exposure to transient ammonia spikes (or other toxins) coming from municipal sewage outfalls and farm waste present in the water causing burns to the sturgeon’s skin tissue.

Recent findings of a four-year Lower Fraser Basin study (Fraser River, British Columbia Canada) have shown that some waterways in the Fraser Valley are overloaded with up to 15 times the level of fecal coliform bacteria considered safe by provincial recreational health guidelines; improper manure storage, dumping and spreading by Fraser Valley dairy, vegetable and poultry farmers were cited as being the main causes here.

Laboratory experiments involving other fish species have clearly demonstrated ammonia levels as low as .5 parts per million (ppm) can create stress upon fish compromising their natural immune system. Moreover, ammonia levels of 2 ppm can cause the natural immune system of the fish to cease functioning. Ammonia can be extremely toxic to fish, although the extent of its toxicity relates directly to the pH and temperature of the water. In cold water of acid pH the ammonia occurs as NH4+ or ionized ammonia, which is not toxic to fish. Once the pH and/or temperature starts to rise the ammonia begins to convert to its toxic form - NH3- unionized or free ammonia. Very low levels of free ammonia are extremely toxic to fish.

Scientists state that the effects of ammonia poisoning are disturbing osmoregulation (the maintenance of the fish's body salts), as ammonia makes the fish more permeable to water. Ammonia also reduces the oxygen-carrying capacity of the fish's blood and causes gill hyperplasia (excessive growth of new cells at the gills), which further hinders oxygen uptake. Other effects include destruction of mucous membranes, and degradation of the brain and central nervous system. The list of damage caused by ammonia on fish is seemingly endless.

Additionally, say scientists, a fish does not have the strength to cope with both ammonia-related stress and disease prevention simultaneously. As the elevated ammonia level presents, the more immediate possibility of death, all of the fish’s energy must be devoted to combatting that threat. It should also be mentioned that Nitrite is a toxic intermediary product created in the process of breaking down organic waste products such as manure. It occurs between ammonia and nitrate in the nitrification cycle. Nitrite interferes with a fish’s ability to use oxygen.

Also present to some degree in our Fraser Valley water systems are remnants of chlorine and chloramine chemicals added by municipal water authorities to kill bacteria in our drinking water. Unfortunately, these substances are also extremely lethal to fish, causing irreversible gill damage.

When the Steelheader News (British Columbia, Canada) reported on the Harrison River sturgeon deaths of June, 1999, Lee Nikl, a Federal Department of Fisheries and Ocean's biologist responsible for investigations said a naturally occurring bacteria may have been in part responsible for the yet unexplained mortalities.

Nikl stated that a known fish pathogen, Aeromonas hydrophila bacterium was found to be present in the blood and gill tissue of sample sturgeon autopsy in Abbotsford, British Columbia at the time.

"Apparently," said Nikl, "as with humans and the plague, not all fish are susceptible to this disease. Perhaps there is something we don't understand that makes certain sturgeon more likely to succumb to the bacteria that breaks down the blood cells in these fish."

Steven McAdam, Senior Hydroelectric Impacts Biologist with the BC Provincial Ministry of Fisheries had this to say on the Harrison River sturgeon deaths: "I believe I would be looking for toxics or other multiple stressers before I pointed to the secondary fish pathogen, Aeromonas hydrophila as being the ‘main cause’ of sturgeon deaths." McAdam said that he has asked biologists with Federal Department of Fisheries and Oceans who are in charge of autopsies and toxicoligical tests to check the condition of ovaries in the dead sturgeon. McAdam explained that he has suspicions of unknown stress factors possibly related to illegal toxic chemical dumps, municipal sewage, or a yet undiscovered combination of naturally occurring chemical agents that affect sturgeon in ways we do not fully understand.

McAdam, who was responsible for writing the final report on the Fraser River's 1993-94 sturgeon mortalities, also said the female sturgeon he examined had an odd ovary condition. He went on to say that of the 8 dead sturgeon found in Harrison Lake in July of 1988, and the notable die-off of white sturgeon in the Lower Fraser River during the summer/fall period of 1993 and 1994, the majority were large females.

He also felt that multiple stressers may have been present prior to the female sturgeons’ spawning periods. These unknown stress factors might have forced the female sturgeon to reabsorb their eggs. Thus throwing the sturgeons’ biological clock completely out of tune with nature. McAdam went on to explain that known toxins collect in the fatty tissue of ovaries in female sturgeon. When the sturgeons’ biological clock is thrown out of time because of possible chemical contaminants or unknown multiple stressers, accumulated toxins may be released into their bodies after they forgo the natural process of propagation of their species.

John Werring, a fisheries biologist with the Sierra Legal Defence Fund, had this to say: "I have no reason to suspect the known secondary fish pathogen, Aeromonas hydrophila as being ‘solely responsible’ for the death of sturgeon on the Harrison River. The Aeromonas hydrophila bacteria is ubiquitous (present everywhere simultaneously) and found in both fresh and brackish water throughout British Columbia. This bacteria is related to human sewage and primarily a bacteria found in human diarrhea. I feel the sturgeon would previously had to have been stressed by some unknown factor or agent before succumbing to the effects of the Aeromonas hydrophila bacteria," said Werring.

"With respect to Aeromonas Hydrophila being a possible causative factor in the deaths of the Harrison River fish," Werring said McAdam stated, "Bacteriological tests identified a secondary fish pathogen, Aeromonas hydrophila."

Werring went on to say, "The key word here is the bacteria is identified as a "secondary" fish pathogen, which is exactly where the literature takes us. Secondary pathogens typically exert their influence on stressed or otherwise compromised organisms. Clearly, McAdams concludes that even the presence of A. hydrophila in some of the dead fish was not sufficient to lead to the conclusion that disease killed the fish."

"Aeromonas hydrophila in the Harrison river mortalities could easily have come from the sewage that is being discharged into the river from the town of Harrison. This bacteria is ubiquitous (found everywhere) in fresh or brackish water so its presence on a carcass would not be unexpected, especially if there is a nearby source like a sewage outfall," said Werring.

"I am not an expert in fish diseases but I do know something about A. Hydrophila, and unless I saw clear evidence that this organism caused massive trauma to the body (i.e., gas bubbles in the musculature, liquifaction of muscle tissue and organs, gangrene, etc.), I would not be inclined to label it a causal factor in the death of these sturgeon," said Werring.

According to scientists with the Cold Spring Harbor Laboratory, New York, who are currently studying several fish pathogens, Aeromonas hydrophila bacteria was said to cause gastroenteritis and sometimes more serious disease (soft-tissue infections, meningitis) in humans. It is also a known fish pathogen, causing hemmorhagic septicemia (blood-poisoning causing copious discharge of blood from the blood vessels) in a variety of fish species. Scientists have found that the infections in fish were usually opportunistic, occurring when the host is immunosuppressed, stressed, or infected with other pathogens.

We leave the final decision on this matter up to you the reader: Is Aeromonas hydrophila bacteria or some form of pollution presently being introduced into our waterways possibly responsible for past sturgeon mortalities and the present spotted skin condition on an alarming number of sturgeon in the Fraser Valley, British Columbia, Canada.

While many questions are left unanswered in the ongoing spotted sturgeon mystery here in BC, one has to sit back and wonder if sturgeon stocks residing on the bottom of the Harrison and Fraser Rivers (where pollutants just happen to be most heavily concentrated) might be acting like the veritable canary in the mine shaft forewarning mankind of gravely serious environmental problems yet to come?