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 Infectious Pancreatic Necrosis (IPN): Coming to a Stream Near You?
Posted by AvidDavid on Monday, August 20 @ 07:10:55 PDT
(The following is excerpted from a post on Flies and Fins and is posted here after a request from Greg.) In June, my son and I made our first trip of this year to the Connetquot River State Park on Long Island (NY). We were surprised to find that several of the rules for fishing had been changed due to the discovery of fish infected with Infectious Pancreatic Necrosis (IPN) a disease that is dangerous for salmonids (Brook Trout, Rainbow Trout, Brown Trout, Atlantic Salmon – see www.dec.ny.gov/environmentaldec/18330.html).
A little research revealed that IPN is caused by a Infectious Pancreatic Necrosis Virus (IPNV – of the species Aquabirnavirus) and is quite harmful to young trout (hatchlings and fry). Other than a darker appearance in young trout, I found no clearly visible indications that will help us distinguish infected from non-infected trout. The virus can be transmitted from fish to fish and from fish to young (presumably in the eggs). IPN was first described in the United States for freshwater trout in the 1950’s. Since that time IPN has been seen in salmonids surrounding the North Atlantic and has affected the British Salmon industry. It has no known adverse medical effect to humans.
Over the past few years, there has been concern that the myxosporean that causes a different infection, Whirling disease, could be transmitted to rivers via waders that have been in other locations with the myxosporean. If introduced upstream of a hatchery (such as in the Connetquot River) a Whirling Disease epidemic could occur. Therefore, NO wading has been permitted above the hatchery for several years. Similar concerns over the spread of IPNV have led to further restrictions of wading, even in the portions of the river downstream from the hatchery. The ranger at the check-in booth told me that there is concern about stirring up the mud in the river and that some of the virus (IPNV) may be trapped in the mud and could be released by fisherman wading in the river. He indicated that the new restriction “only waders no taller than hipwaders may be used,” will avoid fisherman wading into deeper portions of the river and stirring up sediment that has been present for a longer period of time.
Many fish were euthanized earlier this year in an attempt to control the spread of IPN. Larger fish that may be affected have been released downstream of the hatchery. Further, no fish have been stocked above the hatchery. One statement on a blog indicated that if the steps that have been taken now do not eradicate the virus in the Connetquot River by 2009, all the fish in the hatchery and river may need to be killed!
Since my son and I had only chest waders, we chose to fish (without wading) in a deep pool upstream of the hatchery. While we were successful in catching a few fish, it was quite clear that the number of fish available was much less than we had seen in previous trips. Whereas we were accustomed to catching 15-30 fish each in a four hour session, yesterday we caught only 3 fish each. In addition, the fish seemed much more wary. The Upper Connetquot (above the hatchery) is now becoming a much more “real-life” trout stream, with fewer bold and careless stockies and perhaps a predominance of larger, educated holdover fish 15” and up.
This change in the complexion of Long Island’s most abundant supply of coldwater species may be considered good or bad; but the thought of losing this treasure is frightening. Please be aware that this deadly infectious virus may be present in locations other than on Long Island and that fishermen may play a role in avoiding the transport of the virus from locale to locale!
Fliesandfinsnorth.com is certainly a forum with many fly fishermen that I would expect to be interested in spreading the word about this viral infection. Written material from the Connetquot River State Park indicates that “Anglers have the responsibility to wash and disinfect their equipment before and after fishing Connetquot and other waters.” Upon calling the park in June, I was told that disinfection can be performed by using a 20% solution of chlorine bleach. I infer that disinfection of equipment should include rods, reels, line, flies as well as waders, wading staffs, and boots!
Is anyone aware of this devastating disease's prevalence? Might it affect the coldwater species in our pristine Northern waters? The epidemic of this viral infection in salmon of the British Isles suggests to me that our Northern Waters may be very susceptible to this problem. But the lack of outwardly visible signs (other than a decreased density of fish) may require fishermen/women to engage in more active dialogue with Rangers and Fisheries Personnel in order to learn more about the disease and how to eradicate it.
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