Lake St. Clair Muskellunge and Piscirickettsia

Angler diary program catch rates (expressed as rod hours per fish caught) for muskellunge from Lake St. Clair

Master Angler program entries for Lake St. Clair muskellunge

Factors contributing to the consistent high quality of this fishery include: a positive response to increased minimum size limits on both sides of the lake since the mid-1980’s; physical and biological changes in the lake such as clearer water and increased aquatic plant growth resulting in improved habitat for muskellunge; and, increased voluntary catch and release fishing for muskies in Lake St. Clair by both sport and charter anglers.

MDNR workers began to notice red sores/spots on LSC muskie in 2000. No complaints from anglers about muskies with sores. No sign of any unusual mortalities for LSC muskies.

Lesions were in the form of raised, reddish, scabby looking sores, often circular in shape, that varied in diameter from 3 mm to 2 cm.

In May, 2002, muskies with red sores were collected with trap nets from Anchor Bay and examined/sampled by Dr. M. Faisal.

Dr. Faisal collected samples from the external lesions and from internal organs.

Several different forms of bacteria and fungus were present in the lesions as secondary infections.

Transmission electron mirograph showing curved or donut shaped Piscirickettsia-like organisms (arrows). Electron microscopy and live-cell culture verified the presence of a Piscirickettsia-like bacteria (intracellular organism) in blood, skin, and internal organs of the fish. Molecular techniques indicate the bacterium is from the Genus Piscirickettsia, but the species hasn’t yet been determined.

Piscirickettsia salmonis Piscirickettsia-like bacteria are an “emerging” group of pathogens in fish. These are intracellular bacteria, and probability of detection is highest when live fish are sampled. P. salmonis was first “rickettsia-like” bacteria to be recognized as a pathogenic agent of fish. Infects wide range of salmonid fish causing a systemic infection associated with high mortalities in fish culture situations in NA, SA, and Europe. Not previously reported from wild fish, muskellunge, or Great Lakes fish. Contacts in Ontario suggest that Severn Sound muskies (Georgian Bay, Lake Huron) may have exhibited similar external lesions since the mid-1990’s.

Pertinent questions about the disease in LSC muskellunge? How widespread? What is the infection rate among? Is it increasing? Has the disease caused increased mortality? What is the source of the disease? Any measure to control it or to prevent spread to other waters? Other fish species affected? Do parasites play a role? Vertical transmission? Could C&R or tournament practices play a role in the spread of the disease? Will the infection affect the abundance of muskellunge in the lake? What is the species, it’s pathology, how related to P. salmonis?

Study proposed to sample 30 muskellunge (20 with lesions, 10 w/o) from each of 5 regions of the lake (total of 150 fish). Some fish from agency sampling, but many will be from volunteer anglers. Other species bearing red sores will also be sampled when available. Attached parasites will also be sampled (lamprey, Argulus)

Additional information on rate of external lesions in muskellunge will be collected from Angler Diary program participants. Live fish samples are practically a necessity for studying this organism. Coordinating the collection of live fish samples by numerous anglers will present a significant challenge. MDNR will work with angling groups to organize “events” to maximize likelihood of success.

Another significant challenge will be to educate cooperating anglers to recognize the sores. Unfortunately, many Lake St. Clair muskies bear silver lamprey wounds – could be confused with Piscirickettsia sores by anglers.

Ontario Ministry of Natural Resources: Will take lead in developing educational flyer for anglers to help in identifying the external signs of the disease. Will publish and distribute the flyer to Angler Diary program participants and encourage them to record the presence AND absence of such external sores on the fish they catch this summer. Will expedite collectors permits for anglers assisting in collection of muskellunge from Ontario waters. Will participate as co-investigators on any future funding proposals regarding this disease in Lake St. Clair. Will pursue further information from Georgian Bay regarding possible similar sores on muskies and perhaps coordinate sample collection.

Financial needs: Estimated $20,000 needed to process 150 muskellunge and 50 samples of other fish species and macroparasites. An additional $10,000 could be used to hire charter anglers to collect samples if volunteer angler effort is unsuccessful.

Yes, this is finally the end!

NY muskie redsore at Chatagua Lake