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Wisconsin Natural Resources magazine

Wisconsin Natural Resources magazine

DNR fisheries staff collect ovarian fluids from a spotted musky. Muskies are among the species most vulnerable to VHS. © David Rowe
DNR fisheries staff collect ovarian fluids from a spotted musky. Muskies are among the species most vulnerable to VHS.

© David Rowe

August 2008

Tidings from the watery world

Updates of fish issues we've been following

Lisa Gaumnitz, Andy Fayram and Brian Sloss

Viral hemorrhagic septicemia (VHS)
Tournament rules
Musky genetics

When a deadly new fish disease was first detected in six fish from Lake Winnebago and Lake Michigan waters in May 2007, state fisheries officials feared the worst.

The disease, viral hemorrhagic septicemia, or VHS for short, does not affect humans, but it can infect dozens of species of game fish, panfish and bait fish, instead of a single species or related species, which is more typical of most fish diseases. VHS can spread rapidly, fish-to-fish and through the water, and it caused large fish kills in 2005 and 2006 in the lower Great Lakes.

A year later, Wisconsin fish officials are breathing a little easier. "The good news is that we have not seen the big fish die-offs we feared, nor has our testing to date found VHS beyond Lake Michigan or Lake Winnebago waters," says Mike Staggs, the Department of fisheries director. "It appears that the steps the anglers, boaters and wild bait harvesters are taking are working to contain the disease."

More than 180 lots of wild fish from more than 50 waters were tested in 2007, and none had VHS beyond the six fish documented from the Lake Winnebago and Lake Michigan systems. Nor has VHS been found in the fish tested through June 5 from the 30 waters scheduled for monitoring in spring 2008. VHS was found in June in round gobies washed ashore on a Milwaukee beach, but that was not a surprise given the virus had already been found in Lake Michigan fish.

Wisconsin's hatchery system got a clean bill of health as well, with more than 6,000 hatchery-raised fish and hatchery water supplies testing negative for VHS in 2007 and so far in 2008.

Despite that good news, VHS remains a serious fish health issue for Wisconsin, our $2.75 billion sport fishing industry and $14 million aquaculture industry. VHS, which can cause fish to bleed to death, is one of nine fish diseases worldwide that must be reported to international authorities due to the high fish mortality and economic consequences they can cause. The federal government has limited the movement of 37 species of fish susceptible to VHS out of the eight Great Lakes states and two Canadian provinces and also restricts movement among those jurisdictions.

The impact of VHS on wild fish populations in Wisconsin may not be known for five years or more, Staggs says. The VHS affecting Wisconsin and other Great Lakes freshwater fish is a new strain of a virus that historically caused disease in farm-raised rainbow trout; more recently, other strains have infected marine fish in the Pacific and Atlantic coasts. Based on what's happened in other Great Lakes states where the disease was documented earlier than in Wisconsin, this new strain tends to kill young fish right after hatching, so it will take time for such losses to be noticeable in a fish population, Staggs says.

VHS has already triggered significant changes in fish management and anglers' fishing habits $#8211 and that's a good thing, given the increasing risk that new diseases and invasive species will be introduced to Wisconsin waters as global trade increases, Staggs says.

Infected bait fish are the main way that VHS spreads to new waters. Moving large quantities of water with VHS from a lake or river to another is a far less common transmission route. So anglers and boaters are now required to follow rules aimed at preventing people and their boating equipment from carrying the disease to uninfected waters. Minnows purchased from a Wisconsin bait dealer and left over at the end of a trip can be used again on the same or other waters under certain limited circumstances. Otherwise they should be discarded and live wells/bilges emptied, cleaned and dried before boats are moved to other waters.

State fish hatcheries have overhauled their egg collection and handling procedures, instituted VHS testing system wide, stopped transferring wild fish from one lake to another, and limited where fish from certain hatcheries are stocked if the broodstock comes from any waters in the Lake Michigan or Lake Winnebago systems.

People who harvest wild minnows for commercial sale must now get permits to collect wild bait. They and fish farmers are required to have their bait fish tested or inspected for VHS before it can be sold. And all DNR staff who work in the water are required to disinfect their boats and gear before moving to new areas to reduce the risk of carrying VHS to other waters.

"Although the issue for us today is VHS, many of the steps we've taken to slow disease transmission provide better protection from future disease outbreaks, such as the changes in boating and angling regulations. Outreach and education are very good strategies to reduce or stop the spread of invasive species," Staggs says.

If anglers, boaters, the bait industry all do a good job in following the new practices and requirements, Stagges believes, Wisconsin can continue to keep diseases in check. "That will give us more time to understand disease, monitor fish populations and adjust to the disease. Whatever impacts we have from VHS wouldn't hit all waters at once. It will give us time to improve our testing and detection methods," says Staggs.

The VHS test takes 30 days to run, so there's concern that results can be outdated by the time they're received. Fish – or hatchery water supplies for that matter – can become infected in the intervening time and that uncertainty has huge ripple effects: it's why DNR is not allowing transfers of wild fish, has limited where fish from hatcheries within the Lake Michigan and Lake Winnebago basins can be stocked, and has moved away from using live suckers as feed for its hatchery-raised musky and walleye, to name a few precautions.

The cost of the test – $500 to check a lot of 60 fish – and the logistics of collecting and getting the samples to the laboratories within the needed time frame for accurate testing limit how much monitoring for the disease can be done. Wisconsin's surveillance program, while significantly more robust than in many other states where VHS has been detected, has reached only a limited portion of the state's 15,081 lakes and 42,000 miles of perennially flowing rivers.

Work is underway by New York researchers to develop a rapid, one-day test to detect VHS. Even when that test is available, Staggs says the key is for everyone to do their part to prevent the spread of VHS and the next invasive to come down the pike.

"I think it's fair to say our management goal is to contain this disease. It may pop up in a few other waters, but that doesn't mean it's inevitable that it becomes widespread. History in our state and other states with invasive species is that we can slow the spread if we all act responsibly."

Lisa Gaumnitz is DNR public affairs manager for water and fisheries issues.

Tournament rules

Tournaments continue to attract those who like to fish, compete and have a chance at winning prizes. We continue to refine fishing tournament rules to protect fisheries, protect the rights of other water users and the interests of those who appreciate fishing as a quiet way to relax and unwind outdoors. Since 2004, the Wisconsin Department of Natural Resources was directed to write rules to govern tournament fishing to maintain benefits for all water users and address issues like crowding at public access sites, noise and behavior on the water, and perceived effects of fishing tournaments on fish populations.

In developing such rules, DNR created an advisory committee of tournament organizers, members of fishing organizations, the Wisconsin Conservation Congress and groups representing other water uses like recreational boating. The committee met 12 times beginning in August 2004 to discuss comprehensive changes to fishing tournament regulations. Public hearings were also held in 2006 and both results and recommendations were presented to the Natural Resources Board. The rules were subsequently modified based on reactions from the public, the legislature, the Fishing Tournament Advisory Committee and feedback from the Natural Resources Board.

To distinguish small "tournaments" among a few friends from the larger ones that advertise, offer prizes and attract a crowd, the rules describe which sorts of events would warrant monitoring and permits to cover those costs. A fishing tournament that meets any of the following criteria would need a permit under these proposed rules: 1) The tournament consists of 20 or more boats or 100 or more participants; 2) The tournament targets trout on classified trout streams; 3) The tournament is a "catch-hold-release" tournament with an offsite weigh-in; or 4) The total prize value is $10,000 or greater.

Fees charged to these fishing tournaments are higher ($100 or $200 vs. $25) if they are commercial in nature or the tournament rules would raise a higher chance of unintentionally killing fish. Tournament fees were calculated to cover the estimated $33,000 annual cost of administering the program. Costs would be equitably split among the estimated number of tournaments in each category.

In response to concerns raised by the Natural Resources Board, DNR fisheries staff added provisions to the rules that would provide flexibility to reduce the daily bag limit to three fish for walleye and bass tournaments held during hotter summer weather when fish are more stressed. These would apply from the second Saturday in June to the first Sunday in September for walleye and from the second Saturday in July to the second Sunday in August for "catch-hold-release" tournaments when fewer fish might survive before they were released. These reduced bag limits would be specified when the tournament permit is issued well before the actual event. For tournaments where fish are caught, verified and immediately released, such reduced bag limits would not apply.

In addition, the DNR agreed to remove certain program costs from proposed tournament fees to cover expenses for law enforcement and on-site data collection by fisheries technicians. These dramatically reduced the fees charged to tournament organizers. The Natural Resources Board passed a revised version of the tournament rules in January 2008. On May 1, 2008, the Assembly Committee on Natural Resources held a hearing on the proposal. Some individuals supported the rules, but many voiced concerns. The Committee sent the rules back to the DNR for further revision. Tournament organizers didn't like provisions that required participants to submit their boat and live wells to inspection by a conservation warden. Modifications and other small changes have been reviewed by the Natural Resources Board and will again be forwarded to the legislature for its review before new tournament regulations would take effect.

Andy Fayram is a DNR fisheries policy analyst.

Hayward Fisheries Team Supervisor Dave Neuswanger releases one of the muskies sampled to track the genetic lineage of both wild and stocked fish. © DNR Photo
Hayward Fisheries Team Supervisor Dave Neuswanger releases one of the muskies sampled to track the genetic lineage of both wild and stocked fish.

© DNR Photo

Musky genetics

Our research to identify the lineage and genetic makeup of muskellunge statewide is progressing nicely. To date tissue samples have been collected and analyzed from more than 44 musky populations representing all the major water drainages throughout the musky's native range.

Though we've emphasized testing native musky populations where these mighty fish naturally reproduce (Class 1 waters), we've also tested some populations where muskies have to be stocked to maintain a full complement of fish (Class 2). Further, we tested fish from waters where stocking is critical to maintain a viable musky population because the fish don't reproduce on their own or don't have much reproductive success (Class 3). This genetic analysis is conducted at the Molecular Conservation Genetics Laboratory at the University of Wisconsin-Stevens Point where we've now compiled genetic data from more than 1,440 muskies.

Results show there is a great deal of genetic diversity within Wisconsin musky populations, which is a good indicator of the genetic pool from which muskies draw. Greater diversity means greater chance of natural variation which protects a population from genetic weaknesses and recessive traits.

Our tests show a definite split in the genetic makeup of musky populations from the northeastern areas of the state (including the Upper Wisconsin and Upper Chippewa River drainage areas) and the northwestern portions. These distributions and differences do not correspond to contemporary fish management units suggesting these differences are more the result of long-term, natural variations.

One of two explanations or a combination of the two likely describe the current patterns we're seeing. First, the Upper Chippewa River musky populations and the eastern Lake Superior populations may have historically been connected to the upper Wisconsin. This would explain the genetic heritage we are documenting in these fish. Secondly, the influence of stocking cannot be eliminated as a contributing influence if fish were planted from nearby hatcheries rather than relying on established fish management boundaries. For example, the musky populations found in the Upper Chippewa Management Unit are geographically closer to those raised at the Art Oehmcke State Hatchery in Woodruff than the Tommy G. Thompson Hatchery in Spooner. Despite this possibility, we believe this is a minor issue at present due to a high degree of unique genetic features in individual musky populations.

The differences we've observed among populations in western Wisconsin could be due to a combination of their shared ancestry and/or residual effects of the populations originating from a relatively small number of fish. A weak but significant group of muskellunge populations that seem to have slower growth rates has been observed in the genetic data. If this pattern holds up over subsequent data collection and analysis, this could be evidence of a genetic heritage to small/slow growth populations.

The research also suggests that each of the discrete musky populations in western Wisconsin may have grown over time from smaller numbers of isolated fish whose genetic makeup has more of an effect in shaping the genetic characteristics of Wisconsin muskies. Under these conditions, the makeup of muskellunge genetic characteristics is more the result of random chance than adaptation.

We expect the final round of data for these genetic heritage studies in Wisconsin musky will be collected, analyzed, summarized and released by fall 2009.

Extracted from an interim report on FY 2008 Wisconsin Muskellunge Genetic Research by Dr. Brian L. Sloss, Wisconsin Cooperative Fish Research Unit and Director of the Molecular Conservation Genetics Laboratory, College of Natural Resources, University of Wisconsin-Stevens Point.