Download Piscirickettsia in Lake St. Clair Muskie

Lake St. Clair Muskellunge and
Piscirickettsia
35
Rod hours/muskie caught
30
25
20
15
10
5
0
1985
1988
1991
1994
1997
2000
Angler diary program catch rates (expressed as rod hours per
fish caught) for muskellunge from Lake St. Clair
90
40
80
60
35
50
40
30
30
Weight (lbs.)
Number of fish
70
20
10
0
25
1986
1988
Entries
1990 1992 1994 1996
Number over 30 pounds
1998 2000
Max. wt.
2002
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.
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?
Grassy Island Site
Clinton River Site
Clinton River
$
Walpole Island Site
Shipping Channel Site
Thames River Site
Thames River
•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:
1. Will take lead in developing educational flyer for anglers to help in
identifying the external signs of the disease.
2. 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.
3. Will expedite collectors permits for anglers assisting in collection of
muskellunge from Ontario waters.
4. Will participate as co-investigators on any future funding proposals
regarding this disease in Lake St. Clair.
5. 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.