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July 18, 2012
Column

Bad Bait Fish

by Maddelyn Harden, Dr. Heather Deese, and Catherine Schmitt

Uncertainty about the future availability of bait looms over Maine’s lobster industry like a big, gray cloud. What if restrictions on the herring fishery tighten or herring become too expensive? Past bait shortages and concerns about the future already have prompted many lobstermen to pursue alternative bait sources and types. But with different bait comes new concerns about the impacts on lobster health, human health, public perception, and the marine ecosystem.

Viral hemorrhagic septicemia (VHS) is an infectious disease caused by the virus VHSV that adversely affects rainbow trout and other freshwater fish species. Related strains of the virus have been found in marine fish in both the North Pacific and North Atlantic oceans; the Great Lakes recently experienced a damaging outbreak of the disease and recovery may take decades.

The concern for Maine has been that bait fish species used in Maine may be susceptible to the virus, although the spread of VHS through bait fish has never been documented. Threat of VHS has existed for several years; however, no current policies in Maine exist to stop the import of bait fish suspected of hosting the pathogen. The issue has been discussed at the 2012 Maine Fishermen’s Forum, Canadian/US Lobstermen’s Town Meeting, and other industry gatherings.

Currently, the greatest known threat is the strain known as VHSV IVb, according to Deborah Bouchard, of the University of Maine’s Animal Health Laboratory and Aquaculture Research Institute. This strain, which is present throughout the Great Lakes ecosystem, is an RNA virus. RNA viruses can mutate quickly, allowing the virus to adapt to new environments. While the effects on the marine ecosystem are uncertain, the virus could devastate Maine’s freshwater ecosystems if introduced. “It’s a bio-security issue, because we have several state hatcheries raising salmonids, trout species and minnows which are all very susceptible to VHSV,” said Bouchard, who worked with  Dr. Ian Bricknell, director of UMaine’s Aquaculture Research Institute, to conduct laboratory experiments to see how long VHSV could survive in carp fish heads. The virus remained viable in dead and degrading fish, even after salting at room temperature, although salting did work to inactivate the disease after several days.

The transmission of VHSV can occur as a result of fish to fish contact, water transfer, contaminated eggs, and the use of infected fish as bait. Fish infected with VHSV are carriers of the virus their whole lives and can subsequently infect their environment through natural biological life cycles.

Detecting a diseased or infected fish in a natural environment can be difficult. External symptoms include bloated abdomens, red or swollen eyes and red coloration of the skin, gills and fins. Red dots may occur in varying sizes on the skin’s surface. Fish may display abnormal behavior such as erratic and continued flashing (a documented fish behavior where the fish scrapes its body or gill on hard surfaces) if they are infected. There are no signs that indicate the disease affects human health.

When VHSV IVb affected the Great Lakes region, very few states had policies in place regulating the export of live bait fish. After the outbreaks which occurred around 2005, several new policies emerged in Michigan, New York, Ohio, Pennsylvania and Wisconsin regarding the transport of live bait fish, with other policies and regulations being drafted in other regions of the United States.

Compared to other states, Maine has a strict regulatory system for aquaculture finfish species. But there is little regulatory oversight or restrictions on lobster bait products, although use of salmon carcasses is limited to prevent transfer of infectious salmon anemia virus from Cobscook Bay to other parts of the state.

Deidre Gilbert and Carl Wilson of the Maine Department of Marine Resources (DMR) outlined the actions being taken by the agency to help ameliorate the threat of the pathogen.

According to Gilbert, there has been a dichotomy in the regulatory process concerning bait. “Five years ago, in response to the use of cow hides as bait, the Legislature prohibited ‘the waste or rendering of any non-marine organism’ as bait, language which inadvertently included freshwater fish species. But freshwater fish had been used for years. Everyone uses suckers as bait, and at the time there was no reason why this couldn’t be,” Gilbert explained. “Now that VHS is a threat to bait fish, a framework needs to be provided under which regulators from the DMR can create parameters or prohibitions on high-risk organisms.”

According to Gilbert, “We need a mechanism to ban high-risk aquatic species of bait fish. The department needs to create an evaluation process.”

Toward that end, emergency legislation enacted in February 2012 allows the Department of Marine Resources commissioner to maintain a list of acceptable and prohibited bait types.

Bouchard suggested additional risk reduction policies that could protect the industry and the ecosystem could include tracking bait fish origins and conditions of bait fish harvest.

Carl Wilson of the Maine DMR stated, “Lobster fishermen would be remiss if they were doing something to harm the entire ecosystem. The industry has responded well to the threat.”

This article is made possible by funds from Maine Sea Grant.

Maddelyn Harden is a marine science student at the University of Maine. Heather Deese holds a doctorate in oceanography and is the Island Institute’s vice president of programs. Catherine Schmitt is communications coordinator for Maine Sea Grant.

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