Fly Fishing - Threat to Salmonids: Infectious Pancreatic Necrosis

AvidDavid · Location: Long Island, NY

Yesterday, 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.

The Connetquot River is a State Park that offers flyfishing-only by appointment on water that is spring-fed and relatively unaffected by rains, running a cool 56 degrees all year long. In addition to providing some of the most active trout fishing on Long Island, Connetquot River State park was until the 1970’s, a private fishing and hunting club for New York’s elite.

Many years ago, in support of the club’s need for fish, a hatchery was developed on-site. The hatchery is quite active in producing Brook, Rainbow and Brown trout for the river. The hatchery is located near the midportion of the park with fishable “beats” on the river both above and below the hatchery. For several years, wading has been restricted to only those beats below the hatchery due to concern over the spread of infectious Whirling Disease. (There is concern that the myxosporean that causes Whirling disease could be transmitted to the river via waders that have been in other locations with the myxosporean and if introduced upstream of the hatchery a Whirling Disease epidemic could occur in the hatchery population.)

The recent concern over IPN discovered in the hatchery has 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!

Fliesandfins.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 today, I was told that disinfection can be performed by using a 20% solution of chlorine bleach.

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 dangerous infectious virus may be present in many more locations than on Long Island and that fishermen may play a role in avoiding the transport of the virus from locale to locale!