Early Events Could Forecast Busy Summer Season of Fish Kills for DNREC
June 18, 2008
On Tuesday, DNREC staff responded to a fish kill involving an estimated 30,000 young menhaden in Dirickson Creek, a tributary of Assawoman Bay near Fenwick Island. The cause was the same as two earlier fish kills in the Inland Bays this year: not enough dissolved oxygen in the water.
These three events could be just the beginning of what promises to be a busy year for fish kills, Fisheries Manager and Fish Kill Coordinator Craig Shirey said today. “Last year we had very, very few fish kills in the Inland Bays, but this year seems to be shaping up very differently,” Shirey said. “We’re not seeing a significant difference in water quality this year. What we are seeing, however, is a bumper crop of menhaden.”
Atlantic menhaden provide a vital link in the food chain of the Inland Bays and adjoining ocean, serving as a protein-rich food source for striped bass, bluefish and a host of other species. Menhaden are rich in oils and are also processed for food supplements. Adults spawn in the ocean in early spring, and their fry swim into the Inland Bays and other estuaries, where they grow large enough to return to the sea at the end of the summer.
Young menhaden travel in huge, dense schools, seeking rich areas of plankton and algae to feed upon – and, Shirey explained, the larger the school, the more dissolved oxygen in the water the fish need. “During sunny summer days, aquatic plants make oxygen. When the sun goes down, they stop making oxygen and begin consuming it. Levels can drop a little or a lot, depending on demand. So if you have a school of thousands of menhaden as well as other aquatic organisms using up the oxygen, nighttime levels can drop too low for their survival. The result is a fish kill,” Shirey explained.
An algae bloom can complicate this equation. Bright sunny days encourage algae growth, contributing to the oxygen supply, and then consuming it at night. “Plus, the algae can die, drop to the bottom and decompose, consuming even more oxygen,” Shirey said.
A number of other factors can also contribute to or cause fish kills, including toxic species of marine microorganisms. However, none of the fish kills that have occurred in the Inland Bays this year appear to have been caused by any toxic species, he added.
 Although the Inland Bays rise and fall with the tides, these salty inland waters have only two inlets from the ocean – one at Indian River and one at Ocean City. Those inlets do not generate the flushing movement necessary to circulate the water and evenly distribute the oxygen in it, especially in still water coves, as well as creeks such as Dirickson, Pepper and Blackwater, where this year’s fish kills have occurred, Shirey added.
Fisheries biologists routinely monitor the status of fish and other aquatic species, while environmental laboratory scientists from the DNREC Division of Water Resources keep an ongoing record of water quality in the Inland Bays as well as other waterways throughout the state. In the Inland Bays area, DNREC also works with volunteers in the Citizens Monitoring Program for sampling and other information gathering.
Between 1981 and 2007, DNREC has documented 59 fish kills in the Inland Bays, with only four in May and June, noted Marine Biologist Dr. Robin Tyler, one of the scientists who currently monitor water quality in the area. “What these three early kills mean for the rest of the season is hard to say. However, with the unpredictable weather and early heat wave, the number of citizens complaints we’ve already had about algae and what appears to be a very large class of juvenile menhaden for 2008, I feel we could see more than usual this summer,” Tyler added.
Area residents who observe an unusual number of dead or dying fish are encouraged to report their observations, including an estimate of how many fish are involved and what species if they can tell. Depending on the situation, Fisheries biologists, Fish and Wildlife Enforcement, environmental scientists and/or volunteers will respond to check out a fish kill. To help determine the cause of the event, responders will estimate the number of dead fish, note the species, location and other conditions, and, when necessary, take water samples.
“Fish kills are sometimes a natural occurrence. However, human activities ranging from changes to the shoreline to lawn fertilizer runoff providing extra nutrients in the water can have a bearing on these events. Our job is to monitor them, determine causes and watch for potentially preventable problems such as pollution,” Shirey said.
To report a suspected fish kill, please call 302-739-9914 from 8 a.m. to 4:30 p.m. Monday through Friday and 800-523-3336 weekends and after hours.
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Permits Needed Before Using Chemicals or Herbicides on Aquatic Vegetation
June 4, 2008
SPOONER, Wis. — Waterfront owners buying chemicals for weed treatments along and in their shorelines should know they need a Department of Natural Resources permit before using the product. The permit is necessary to insure proper use of the chemical and prevent harm to the lake or stream.
“Aquatic plants are important parts of a lake’s ecosystem – they provide oxygen for the fishery, habitat and water quality,” said Tom Jerow, waters media leader for the DNR’s northern region. “But we recognize that too much of a good thing is a problem and shore owners sometimes need to control plants. We use the permits to make sure that plant treatments are applied at the best times and in the best way to protect the lake.”
A number of advertisements have been placed in the media recently announcing chemicals that “kill weeds.” The ads, however, fail to mention the need for a Department of Natural Resources permit and other important information.
Jerow said that only those chemicals registered with the U.S. EPA and the Wisconsin Department of Agriculture, Trade, and Consumer Protection (DATCP) can be used on Wisconsin waterways. He added that when controlling aquatic plants with chemicals, it is important to correctly identify the plants and the appropriate chemical beforehand and to be certain that treatment occurs at the proper timing and dosage. To apply chemicals in liquid form, the applicator must be licensed with the DATCP. It is often best to contract with a commercial applicator.
The only time a permit is not required to control aquatic plants is when a shoreline owner hand-pulls or rakes plants, except wild rice, from his/her shoreline. That work can occur in an area that is 30 feet or less in width extending from the shore to open water. Non-native invasive plants (Eurasian water milfoil, curly leaf pondweed, and purple loosestrife) may be manually removed beyond 30 feet without a permit, as long as native plants are not harmed. Wild rice removal always requires a permit and is only allowed in very restricted circumstances after consultation with Tribal Natural Resources Departments.
“Working together to assure good management of aquatic plants, we can maintain the qualities of a waterway that attracted the shoreline owner to the area in the first place,” Jerow said.
FOR MORE INFORMATION CONTACT: Tom Jerow - 715-365-8901
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DNR Finds Eurasian Watermilfoil in a New Lake Near Brainerd
June 4, 2008
Eurasian watermilfoil, an invasive species already found in some Minnesota lakes, was discovered Monday in Upper Mission Lake, located 15 miles north of Brainerd.
Minnesota Department of Natural Resources (DNR) staff were conducting a survey of aquatic plants when they noticed fragments of Eurasian watermilfoil floating in the lake. Rooted plants were found growing near shore in one location. Researchers are now trying to determine the extent of the problem in the lake.
Milfoil is now known to have spread to 205 bodies of water in the Minnesota since it was discovered in the late 1980s. The majority of infested water bodies are in central and north-central Minnesota, according to Chip Welling, DNR Eurasian Watermilfoil Program coordinator. Of the 416 lakes in Crow Wing County, five are now known to have milfoil. The full list of infested waters is available on the DNR Web site at www.mndnr.gov
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Welling urges boaters to take precautions to avoid spreading invasive species. “They should inspect their boats, trailers and equipment inside and outside and remove plants, animals and mud,” Welling said. “It is important to wash and dry boats, tackle, downriggers, trailers and other recreational equipment. Washing will remove or kill harmful species that were not visible at the water access.”
Anglers are also advised to dispose of unwanted bait in the trash.
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Weed Control Successful at Dewart Lake
May 29, 2008
An aquatic herbicide application two years ago to control Eurasian water milfoil in Dewart Lake has nearly eliminated the noxious non-native weed from the 551-acre Kosciusko County lake.
During sampling late this month, milfoil was found at only three of 90 locations checked by DNR Division of Fish and Wildlife biologists. Last year, biologists were unable to find milfoil at any of the 90 locations in May or July.
Prior to 2006, Eurasian water milfoil covered nearly 60 percent of the shallow water area of the lake and 80 percent of the area between 5 and 15 feet deep. In some spots, the plant reached the surface and was so thick that boaters could not get through it.
This invasive weed, which interferes with boating and fishing, was the target of a state-approved, lake-wide control program in May 2006. Funds for the treatment came from the DNR Lake and River Enhancement (LARE) program and local lake residents.
A licensed contractor was hired to apply approximately 28 gallons of Sonar® to the lake. The herbicide contains the chemical fluridone, which, when used properly at low dosages, can selectively kill milfoil with little harm to other plants.
“The herbicide treatment was very effective and knocked milfoil down to a very low level,” said Jed Pearson, DNR fisheries biologist. “We expect it to come back but it should be easier to control with spot treatments.”
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Although the fluridone application caused some damage to coontail and other native plants in the lake, Pearson said he expects them to recover.
“Coontail covered 43 percent of the lake’s shallow-water area before the treatment and dropped to 12 percent after,” Pearson said. “Hopefully, coontail will come back to that same level. Overall, aquatic plants still cover more than 80 percent and include a good mix of native species.”
Biologists will re-check Dewart Lake in July and monitor the plant community for several years to study long-term benefits of the treatment.
Success of the milfoil control program at Dewart is similar to results at other lakes in northern Indiana, including Heaton Lake in Elkhart County, Lake-of-the-Woods in Marshall County, and Wall Lake in LaGrange County.Â
“The treatments reduced milfoil in all cases, but we won’t know how long the control will last or the full effects for many years,” said Rod Edgell, a DNR biologist who has examined the impacts of fluridone on water quality and food habits of fish at Dewart and Heaton lakes.
No changes in largemouth bass diets were detected at either lake after fluridone treatments.
“Although we’re content with results so far, we want to be cautious when approving fluridone use at other lakes,” Edgell said.
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DNR Seeks Comments on Two Lake Vegetation Management Plans in Duluth Area
May 29, 2008
The Minnesota Department of Natural Resources (DNR) is seeking public comments until June 13 on lake vegetation management plans for Caribou and Nichols lakes, which are located near Duluth in St. Louis County.
The draft plans and comment forms are available on the DNR Web site at: http://www.mndnr.gov/areas/fisheries/duluth/reports.html
Draft plans are also available for review at the DNR Area Fisheries Office in Duluth from8 a.m. to 4:30 p.m., Monday through Friday. People can receive a copy of the plans in the mail by calling (218) 525-0853, ext. 200. Comments should be sent to Nick Frohnauer; DNR Fisheries; 5351 North Shore Drive; Duluth MN 55804 or e-mailed to nick [dot] frohnauer [at] dnr [dot] state [dot] mn [dot] us.
Lake vegetation management plans describe current and historical conditions of the lake. The plans identify specific management activities planned for that lake in the next five years. Those activities include shoreline owner aquatic plant management standards, lake commons area aquatic plant management, and measures to help reduce nutrient inputs.
Minnesota has seen an increase in the number of aquatic plant management permits in the last 10 years. Aquatic plant management permits give a shoreland owner permission to remove certain aquatic plants. DNR Fisheries in Duluth has developed lake vegetation management plans for lakes with associations that do intensive plant management.
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CT DEP Reminds Opening Day Anglers To Take Precautions To Prevent Spread Of “Didymo” Into Connecticut Waters
April 25, 2008
Highly invasive alga found last year in several popular trout streams in the Northeast, Anglers considered an important vector in spread of didymo.
With Opening Day of trout season this weekend, the Connecticut Department of Environmental Protection (DEP) is reminding anglers and boaters to be on the lookout for the highly invasive freshwater alga Didymosphenia geminata, known as “didymo,” and to take precautions to prevents its spread into Connecticut waters.
In 2007, the presence of didymo was confirmed in the northern reaches of the Connecticut River (NH/VT), White River (VT), Batten Kill (NY/VT) and the East and West Branches of the Delaware River (NY/PA), all popular trout streams. These were the first official reports of didymo in the northeastern United States.
Didymo (commonly referred to as “rock snot”) is most frequently found in cold, relatively shallow streams and rivers having a rocky bottom, characteristics that are also typical of good trout habitat. During blooms, didymo can form thick mats of material that feel like wet wool and are typically gray, white and/or brown, but never green in color. These mats form on the bottoms of rivers and streams and can potentially smother aquatic plants, aquatic insects and mollusks, alter stream flow characteristics and fish habitat, and impact the food chain. Dense mats of didymo can also reduce the recreational and aesthetic value of the affected river.
Anglers may have contributed to the recent spread of didymo. The microscopic cells can cling to fishing gear, waders (felt soles can be especially problematic), boots and boats, and remain viable for months under even slightly moist conditions. Although didymo has not yet been found in CT, it has been found in near-by states. It is recommended that trout anglers, especially those who also fish streams outside Connecticut, practice CHECK, CLEAN, DRY procedures.
CHECK: Before leaving a river, stream or lake, remove all obvious clumps of algae and plant material from fishing gear, waders, clothing & footwear, canoes & kayaks, and anything else that has been in the water and look for hidden clumps. Leave them at the site. If you find any later, clean your gear and dispose of all material in the trash.
CLEAN: Soak/spray & scrub boats and all other “hard” items for at least one minute in either very hot (140°F) water, a 2% bleach solution, or a 5% dishwashing detergent solution. Absorbent materials such as clothes and felt soles on waders should be soaked for at least 40 minutes in very hot water (140°F), or 30 minutes in hot water (115°F) with 5% dishwashing detergent. Freezing thoroughly will also kill didymo.
DRY: If cleaning is not practical, after the item is completely dry to touch, wait an additional 48 hours before contact or use in any other waterway.
The above procedures will also be effective against other unwanted organisms.
Although didymo has not yet been found in Connecticut, DEP is taking additional precautions to prevent the introduction and/or spread of this and other invasive species. DEP’s Inland Fisheries Division is currently developing a formal “Biosecurity” policy for its field operations, with implementation to begin this upcoming field season. Also, as part of its outreach efforts on invasive species issues, DEP will be mailing an informational flier on didymo to many of the state’s bait & tackle shops this week.
An excellent source for information on didymo is the Biosecurity New Zealand web site www.biosecurity.govt.nz/didymo. Additional resources include the New Hampshire DES web site: www.des.state.nh.us/wmb/exoticspecies/didymo/index.html and the US EPA Region 8 website www.epa.gov/region8/water/didymosphenia/.
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