Fish Health Studies

Adult lake trout and some least cisco caught under the ice in Teshekpuk Lake, November 2005

Mold on Fish in Nuiqsut

Saprolegnia is a water mold that was found on Aanaakłiq by Nuiqsut fishermen during the fall of 2013 to 2016. This water mold is common in freshwater around the world and grows on live and dead matter (fish eggs, insects, etc.). It can infect fish through wounds on their skin. Saprolegnia can cause a disease in fish called Saprolegniosis. Normally, fish have a healthy mucous coating on their skin as a natural barrier. Injuries to fish or stress can reduce this mucous coating which can lead to infection. Some causes of stress could be crowding, pollution, changes in environment (as in water temperature, salinity, water flow), and reproduction (especially spawning males). The water mold can penetrate the skin of the injured or stressed fish, causing fluid loss and can lead to death. Symptoms of this disease are whitish, moldy patches on the body (see picture below).

The water mold was found on fish caught from the Colville main channel and the Niġliq channel. Saprolegniosis has not been reported from Nuiqsut before, but one case was reported on the Inaru River in 1980. Saprolegniosis has been reported in no other species of fish to date on the North Slope; however, it has been found on salmonid species (salmon, trout, char, whitefish, and grayling) in other parts of Alaska and Canada.

The cause of these recent cases of Saprolegniosis is not yet known. Baseline data will continue to be collected and a NSB-DWM Task Force has been formed to develop a monitoring plan with Nuiqsut. According to the State of Alaska, Saprolegnia will not harm humans. However, NSB-DWM recommends maintaining your traditional and customary practices when handling unusual fish. For more information, or to report a sighting or catch, please call NSB-DWM at 907-852-0350. You may also contact Todd Sformo or Raphaela Stimmelmayr.

Below you will find the Compilation of Reports on Fish Mold and Contaminants in Nuiqsut Fish (2013-2016), plus reports from contaminant studies dating back to 2002.


​Study of Food Chain Pathways – Environment to Humans – Fish

This study, which is part of a larger food chain pathway project, includes analysis of the contaminant levels of freshwater and marine fish on the North Slope. Fish species sampled were arctic cod, arctic char, pink salmon, and fourhorn sculpin. Results of the study showed that persistent organochlorine levels in the fish species sampled were low, lower than marine mammals. Recommendations for human consumption are that these fish are considered safe to eat.


Review of Contaminant Studies – Colville River Area Fish

During 1998-2001, four separate studies contributed to an assessment of contaminants levels in the fish taken in the Nuiqsut subsistence fishery. Those studies were initiated because of the news that relatively high levels of contaminants were documented in some fish from the Umiat area, upriver from Nuiqsut. All of the four studies ultimately concluded that fish taken in the Nuiqsut subsistence fishery were safe to eat based on an ASTDR review, detailing 4 different exposure levels for persons eating higher amounts of burbot livers.

The Colville River is the largest river drainage system on the North Slope and is an important subsistence resource for North Slope residents, especially the people of Nuiqsut. Umiat, about 90 miles south, or upstream of Nuiqsut, on the Colville River, is a former base for U.S. Navy oil exploration and Air Force defense site. This industrial and military activity led to its listing as a federally registered contaminated site. The Army Corps of Engineers started cleanup activities in the late 1990’s. Cleanup activities are not yet completed at Umiat.

Research entities involved: NSB Dept. of Wildlife Management (DWM) and then-graduate student Paul Hoekstra and Dr. Derek Muir (Environment Canada), Agency for Toxic Substances and Disease Registry (ASTDR), Ecology & Environment, Inc (evaluation study for Army Corps of Engineers or ACOE), and the Jesse Ford group (Jesse Ford, Susan Allen-Gil NSF study).

Summary of results:

See below or click here for a more detailed summary.

NSB Department of Wildlife Management – Assessment of PCBs and DDTs in fish from Nuiqsut subsistence fishery as a comparison to fish from Umiat

This analysis effort on Colville River fish came about following the discovery of elevated levels of some contaminates in fish caught at Umiat as part of clean up activities. The Army Corps of Engineers started cleanup activities in the late 1990’s. NSB initial results (2000) – Good News – Nuiqsut fish are safe to eat!

PCB and DDT levels found in Burbot livers from Umiat and Nuiqsut

Fish tested from the Nuiqsut subsistence fishery were considerably lower in PCBs and DDT than Umiat area caught fish. The burbot from the Nuiqsut area were 7 times lower for PCBs and 25 times lower for DDTs than the Umiat fish. The Nuiqsut fishery burbot tested lower for PCBs and DDTs than bowhead whale blubber. It has been documented that these levels in bowhead whale blubber are low enough that the blubber is safe to eat. Click here for more information on nutrients and here on contaminants in bowhead whale subsistence foods.

NSB Department of Wildlife Management staff collect and report on additional fish collected from Nuiqsut resident fisherman in 2001

Summary of results:

The 2001 results show that Nuiqsut fish are 10 and 45 times lower than the Umiat original (1998) test results. PCB and DDT levels in the fish from the Nuiqsut fishery were 7-11 times lower for PCBs and 25-45 times lower for DDTs than the Umiat area fish. When the 2001 PCB and DDT levels in the Nuiqsut fish are figured into Canadian guidelines (Jensen et al. 1997) the “allowed or recommended consumption amounts” are below.

Allowed amounts of Nuiqsut burbot liver

  • for PCB levels found, it is allowed to eat:
    • 31 pounds per week per person for a lifetime
  • for DDT levels found, it is allowed to eat:
    • 2,117 pounds per week per person for a lifetime

Agency for Toxic Substances and Disease Registry (ATSDR) Health Consultation regarding fish from Umiat

See June 25, 2001 report for details.

Summary of findings:

  • There is a point source of PCB and DDT contaminants in the Umiat Slough, and slough fish are exposed to these contaminants.
    • Since no one is fishing and eating fish from the Umiat Slough, it is not a current public health problem.
  • The Colville River fish sampled from within 4 miles of Umiat up and down stream do not indicate a need for public health concern.
    • Broad whitefish levels were very low.
    • The extent of downstream contamination is not yet well known.
    • Appropriate dietary information (where people fish and how much is eaten) is not yet available to adequately assess the potential risks.
  • The dietary nutritional benefits of the native subsistence diet must be considered prior to changing the diet in the Umiat/Colville area.
    • Nutrient benefit values and contaminant data should be evaluated at the same time to determine the safety of fish in diet of area residents.
    • Dietary fish survey for subsistence users should be done.

New Ecology and Environment, Inc. (E&E)/Army Corps of Engineers (ACOE) Umiat Study

Additional fish were analyzed, including fish and water downstream of Umiat.

Summary of findings:

  • The Umiat Slough contaminants were not responsible for the levels in fish near Nuiqsut.
  • The highest levels of PCBs and DDTs in burbot were found in fish from locations near the Umiat Slough.
    • Burbot and other fish that migrate into the Umiat Slough “are responsible for the higher concentrations in the Colville River fishery upstream and downstream of Umiat.
    • Most of the burbot affected by PCBs and DDTs from the Umiat Slough were found nearest the slough, but some of these burbot have migrated approximately 60 miles downstream to Ocean Point.
  • The main source of PCB and DDT contamination of burbot in the main Colville River is atmospheric (global pollution effect).
    • The levels of PCBs and DDTs in Colville River burbot are similar to burbot caught from other areas of the arctic (13 Canadian Yukon lakes).
  • Contaminant patterns in the water samples show PCBs and DDTs present in the Umiat Slough affecting nearby downstream locations, but not locations nearest Nuiqsut.

ATSDR determined that the fish from the Nuiqsut subsistence fishery are safe to eat at four different exposure levels (in November 2003)

  1. Eating fish from the river every day for 70 years “Conservative chronic exposure” from eating a high quantity of fish (up to almost a pound) from the river every day for 70 years.
  2. Eating whole burbot in high quantities 4 months of the year “Intermediate exposure” from eating burbot in high quantities during certain times of the year (for example, during the seasonal harvest).
  3. Eating burbot livers 4 months of the year “Intermediate exposure” in which the elders of the Nuiqsut community eat about six burbot livers per week and children eat about three livers per week during the 4-month burbot. harvest.
  4. Eating several burbot livers in one sitting “Acute exposure scenario” in which elders eat six burbot livers during one meal.

Although PCBs, DDT, and DDT derivatives were detected in fish collected from multiple areas of the river, the levels were low, and exposures to those levels are not expected to cause harmful health effects. Go to the ATSDR website for more information.

Summary of Jesse Ford, Susan Allen-Gil NSF study – July 2004:

In July 2004, the Jesse Ford group traveled to villages for community meetings to review the preliminary results of their work. Staff from KBRW accompanied them and aired the meetings live. As part of their study, they checked some tittaliq for contaminants and reviewed the results in light of community concern stemming from the information about Umiat fish. Their analysis showed:

  • Tittaliq (burbot) liver higher in contaminant than Aanakliq and Iqalusaaq (broad whitefish and least cisco).
  • Contaminate levels downstream (not right at Umiat) are much lower than Umiat levels.
  • Contaminate levels are similar to commercial food levels.

Go to Jesse Ford’s website for more information on her work.

Sampling fish for hydrocarbons

Petroleum Hydrocarbons in Fish Study

Principal Investigators J. Craig George, Ph. D.
Project Coordinator Cyd Hanns
Collaborators Dana Wetzel, Mote Marine Laboratory
Alaska Department of Commerce, Community and Economic Development


We collected fish from Teshekpuk, Ikpikpuk, Colville/Nuiqsut fishery areas; sampled fish and sediments for baseline PAHs (focused on broad whitefish and burbot). This project analyzes PAHs and biomarkers. No direct testing of other contaminants was done. Biomarker results give some indication of general health status/exposures of fish. Preliminary report below and final report pending.

Preliminary report from Dana Wetzel as of September 2007:

This project focuses on collecting baseline information related to oil exposure in subsistence harvested fish species in NPR-A. The information can help with monitoring for changes in levels and sources. Fish may be exposed to petroleum oil from natural sources such as the North Slope’s natural seeps or coal bed areas, or human related activities associated with industry, camps, or docks – minor or major oil spills. Oil industry activities are expanding across NPR-A.

Petroleum hydrocarbons are the chemical building blocks of petroleum oil, other fossil fuels, and man-made petroleum products (made up of a variety of hydrocarbon chemical chains of various lengths and shapes). This project tests specifically for petroleum “polycyclic aromatic hydrocarbons” (PAHs) since they include the most toxic fractions of oil.

Fish (vertebrates) metabolize and excrete PAHs so they are not stored (don’t accumulate) in fish very long under normal circumstances. PAHs are metabolized in the liver and by-products (metabolites) are excreted through the bile. Some of these breakdown products are more toxic than others. Generally, in order to find PAHs in tissues, the tissues must be collected within a short window of time after exposure (about 2 weeks) or when there is longer-term chronic (consistent) exposure as in more highly polluted areas.

We work directly with many local subsistence fisherman and involved students at Barrow and Nuiqsut with collecting fish and sampling. A separately funded continuation of the original project is planned for the next two years and will include subsistence fishery areas for Wainwright and Atqasuk.

To date we have:

  • Fish and sediment results from Teshekpuk Lake, Mayurgiaq, Ikpikpuk, Colville River areas (broad whitefish, burbot, and sediments or bottom mud).
  • Samples of fish from Wainwright & Atqasuk subsistence fishing sites. Analyses in progress.

So far, as expected and overall, the fish tissue levels of PAH contamination have been very low or non-detectable. PAHs were detected in all sediments (not surprisingly, low levels) and showed several different profiles (component varieties) suggesting different or a combination of sources of petroleum. Some fish liver samples were analyzed for biomarkers (specific measures of chemical changes related to stressors, exposures to contaminants, and the health condition of the fish) – no biomarker sign that fish are stressed, and the final report is pending.


More Information on Fish Studies and Fish Health

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