Fisheries Currents

Science news from the American Fisheries Society Issue 2, April 2006 Welcome to the second edition of Fisheries Currents, a digest of newsmaking fisheries science articles from the journals of the American Fisheries Society. Each issue, highlighted articles will include a broad array of topics related to recreational and commercial fishing, aquaculture, endangered species, and aquatic environmental issues. Links to the abstracts are provided--please e-mail Beth Beard at [email protected] if you would like a PDF file or fax with the full text. Is a Lead Sinker Ban Needed to Protect Waterfowl? Since lead shot for hunting waterfowl was nationally banned in 1991, some jurisdictions have turned their attention toward the lead sinkers used by recreational anglers. Several studies have indicated that water birds do ingest lead sinkers and then suffer or die from lead poisoning. Lost fishing line has also been known to entangle birds and other wildlife. In a recent article in the North American Journal of Fisheries Management, Minnesota Department of Natural Resources scientists attempted to estimate how much fishing tackle is actually being lost. More than 6,000 angler parties were interviewed over several months at five Minnesota lakes to determine how much tackle they had lost that day. Although the amounts of tackle being lost per hour was relatively low (97% of anglers reported losing no split shot sinkers after a day fishing), the estimated total loss of tackle for the summer was 214,811 items, of which over 100,000 contained lead (totaling about 1 metric ton of lead lost). Assuming the reported tackle loss rates, the estimate of cumulative lead tackle loss for three of the five lakes from 1983 to 2004 was over 16 metric tons of lead. It was estimated anglers left more than 1 million pieces of lead in one lake alone over this 20-year time period. Although further research is needed, anglers fishing in areas with both critical water bird populations and high angler activity should consider alternatives to lead sinkers. Estimates of Tackle Loss for Five Minnesota Walleye Fisheries, by Paul Radomski, Tom Heinrich, Thomas S. Jones, Pat Rivers, and Phil Talmage. North American Journal of Fisheries Management 26:206-212. Radomski may be contacted at [email protected]. One in Four Western Stream Fish Is Not Native. Although nonnative fish have been recognized as threat to native species in many individual western streams or watersheds, no study has attempted to quantify the issue on a larger scale. In a recent article in the North American Journal of Fisheries Management, scientists from the U.S. Geological Survey Cooperative Fish and Wildlife Unit at the University of Arizona systematically collected fish over 3 years at 689 stream sites in 12 western states. They also recorded the site conditions such stream size and human land use. Nonnative species were found in about half of the streams that contained fish, and accounted for one in four of the individual fish collected. Colorado had the highest abundance of nonnative fish, where two out of three fish were nonnative, followed by Arizona where one out of two fish was nonnative. In North Dakota only 1 in 12 fish was nonnative. The 10 most common nonnative species were brook trout, brown trout, rainbow trout, common carp, smallmouth bass, largemouth bass, green sunfish, fathead minnow, yellow perch, and yellow bullhead. Counterintuitively, the relative abundance of nonnative species was higher in less disturbed streams and those with lower human population densities. However, the scientists did find an expected inverse relationship between the abundances of native and nonnative fishes. Distribution and Abundance of Nonnative Fishes in Streams in the Western United States, by Charles B. Schade and Scott A. Bonar. North American Journal of Fisheries Management 25:1386-1394. Scott Bonar can be contacted at [email protected]. How High Can Brook Trout Jump? Related to the above story, sometimes it is necessary to keep brook trout out of western streams that are home to threatened or endangered species of native cutthroat trout. Brook trout are the number one nonnative species found in West (see above) and will out compete cutthroat trout for both food and habitat. One way to restore cutthroat trout is to eradicate brook trout in stream sections, which are then protected from reinvasion by a natural or artificial barrier such as a waterfall. Conversely, brook trout in their native range in the East often encounter migration obstacles like dams and culverts that are thought to be detrimental to their population. So the question is, just how high can brook trout jump? And how would you find out? Researchers at Colorado State University put 11,000 brookies to the test, 25 trout at a time, in a recent article in Transactions of the American Fisheries Society. Different sizes of hatchery-reared brook trout were given 24 hours to clear different combinations of pool depths and waterfall heights. Those found at the other end the next day were deemed successful jumpers. The larger fish were able to clear 73 centimeter waterfalls, or 2.9 to 4 times their body length, as long as the plunge pool was deep enough. The authors note that they conducted the tests in the laboratory using hatchery fish, so wild fish might jump higher under natural conditions. Thus a barrier at least 1 meter high with a shallow 10 centimeter plunge pool should be sufficient to keep out brook trout. On the other hand, if you want brook trout to get past obstacles in their native range in the East, then the height should be below 40 centimeters, with a deep plunge pool. How High Can Brook Trout Jump? A Laboratory Evaluation of Brook Trout Jumping Performance, by Matthew C. Kondratieff and Christopher A. Myrick. Transactions of the American Fisheries Society 135:361-370. Matthew Kondratieff can be reached at [email protected]. Angling’s Effect on Largemouth Bass Virus. In recent years, largemouth bass virus (LMBV) has emerged a cause of fish kills of largemouth bass. Both anglers and scientists have watched in alarm as the virus has spread across several states, although one of the mysteries of this disease is that some waterbodies suffer large fish kills while others have very low mortality from the virus. Is another factor responsible for this highly variable response to the virus? Scientists from the University of Illinois studied whether angling was related to either LMBV mortality or transmission. In an article in the Journal of Aquatic Animal Health, they simulated effects of catch-and-release angling on bass infected with the virus. Infected bass angled out of tanks did not have higher mortality or viral loads than fish that weren’t angled out of the tanks. However, if infected fish and uninfected fish were held together in a tank simulating live well conditions, LMBV was transmitted through the water, even if the fish were kept out of direct contact. Effects of Practices Related to Catch-and-Release Angling on Mortality and Viral Transmission in Juvenile Largemouth Bass Infected with Largemouth Bass Virus, by Emily C. Grant, Kate R. Inendino, William J. Love, David P. Philipp, and Tony L. Goldberg. Journal of Aquatic Animal Health 17:315-322. Tony Goldberg can be contacted at [email protected]. Media Advisory: The 136th Annual Meeting of the American Fisheries Society will be held September 10-14, 2006 in Lake Placid, New York. This year’s meeting theme is “Fish in the Balance.” A list of the 32 symposia sessions is now available online at http://www.afslakeplacid.org/, along with a searchable database of meeting abstracts. Media can register for free by contacting Beth Beard at [email protected].