Fisheries Management On Lake Vermilion In 2012 MN Dept. of Natural Resources Division of Fish and Wildlife Section of Fisheries 650 Highway 169 Tower, MN 55790 Phone: 218-753-2580 2 Introduction Lake Vermilion is part of the statewide Large Lake Program, an intensive fisheries management program on the 10 largest lakes in Minnesota. The Large Lake Program was started in 1984 when it became apparent that more detailed biological information was needed to properly manage these important lakes. A Large Lake Specialist was assigned to each lake to manage the program at the area level. The Large Lake Program includes annual fish population assessments, annual water quality monitoring, and regularly scheduled creel surveys. A variety of sampling gear is used during population assessments to collect the various fish species and life stages; including gill nets, trap nets, beach seines, and an electrofishing boat. Sampling for each gear type is conducted at the same time and place each year in order to determine population trends for the major species. Data is also collected on length, weight, age, and growth for each of the major species. Creel surveys are scheduled on Lake Vermilion for two consecutive years out of every six years. Creel survey is a scientific method of estimating fishing pressure and fish harvest from a series of boat counts and angler interviews. The last creel surveys were done in 2008 and 2009 with the next cycle of creel surveys scheduled for 2014 and 2015. The results of the 2012 fish population assessment are presented in the balance of this report. We encourage anyone with questions or comments to contact the Tower Fisheries office or stop by our office for a visit. We are located just west of Tower on Highway 169. Duane Williams, Large Lake Specialist Phone: 218-753-2580, ext. 224 Email: duane.williams@state.mn.us Edie Evarts, Area Fisheries Supervisor Phone: 218-753-2580, ext. 222 email: edie.evarts@state.mn.us 3 Walleye The walleye gill net catch in 2012 was 15.4 fish/net, slightly less than the catch in 2011, but still above the long-term average for Lake Vermilion (Figure 1). Walleye gill net catches were slightly below average from 2008 to 2010 due to poor reproduction in 2004, 2005, 2008, and 2009. Improved walleye catches in 2011 and 2012 were due to good reproduction in 2007 and 2010, and higher than normal catches of older fish. There are often differences in fish populations between the two major lake basins, East Vermilion and West Vermilion, and some of the assessment data is analyzed separately. The 2012 walleye gill net catch on East Vermilion was 19.3 fish/net, while the walleye catch on West Vermilion was 9.5 fish/net. Walleye gill net catches are usually higher on East Vermilion, while the average size is larger on West Vermilion. Walleye populations in large natural walleye lakes often fluctuate in response to strong and weak year classes. Generally, strong year classes are produced every few years, which is sufficient to maintain a good population. Because fish production is limited by lake productivity, it would be impossible for lakes to sustain strong year classes every year. Lakes with excessive walleye harvest tend to have highly variable reproduction and walleye abundance. Lakes with low walleye harvest tend to have more stable populations. Figure 1. Walleye Gill Net Catches, 1984-2012 4 The mean length of walleye sampled by gill nets was 14.9 inches, well above the historic average. Good numbers of large and medium sized walleye were sampled during the survey, while the catch of smaller fish was slightly below average (Figure 2). The high catch of 15-20 inch fish was due primarily to a strong 2007 year class, which has dominated the fishery in recent years. Most of the walleye over 20 inches long were sampled on West Vermilion and came from strong year classes produced in 2002 and 2003. Low to average numbers of small walleye in the gill net catch reflects poor reproduction in 2008 and 2009. The gill net catch of small walleye was considerably higher on East Vermilion, where the 2010 year class appears to be stronger than it is on West Vermilion. Small walleye are nearly always more abundant than medium and large fish although this is not reflected in the gill net catch. The experimental gill nets used for population assessments do not sample small fish very well so small fish are under-represented in the gill net catch. Walleye are not sampled at maximum efficiency until they are about 13 inches long. The decline in the gill net catch of fish larger than 13 inches represents the effects of mortality and declining abundance. Healthy walleye populations will have good numbers of fish across a wide range of size classes. Heavily exploited walleye populations tend to have high numbers of small fish and few large fish. Figure 2. Walleye Length Frequency From Gill Nets, 2012 5 Walleye year class strength can be represented by indices that are calculated from gill net catches of each year class for several years of netting (Figure 3). High values indicate strong year classes, while low values represent poor year classes. The strongest year classes produced in recent years were the 2006, 2007, and 2010 year classes. Strong year classes were also produced in 2002 and 2003, especially on West Vermilion. Year classes produced in 2004, 2005, 2008, and 2009 were all weaker than average. Unusually cool weather in 2004 and 2009 probably affected walleye reproduction in those years. Weak year classes of walleye on Lake Vermilion are often related to cool spring and summer weather which can negatively affect first-year growth and survival. Nearly all of the major fish species experienced poor reproduction in 2004 and 2009, due to the cool spring and summer weather in those years. It takes at least two years to calculate a year class strength index for any individual year class, therefore indices have not yet been calculated for the 2011 and 2012 year classes. One year of netting indicates the 2011 year may be stronger than average. Figure 3. Walleye Year Class Strength Indices, 1984-2010. 6 Fall electrofishing is used to sample young-of-the-year walleye and help determine reproductive success for the year. The 2012 fall electrofishing catch of young-of-the year walleye was 216 fish/hour, well above the historic average (Figure 4). It was the second consecutive year of high electrofishing catches, after unusually low catches in 2009 and 2010. East Vermilion had a much higher electrofishing catch than West Vermilion. Electrofishing catches are usually higher on East Vermilion. The mean length of young-of-the-year walleye sampled by electrofishing in 2012 was 6.0 inches, well above the historic average. Data from our sampling program indicates growth of young-of-the-year walleye is an important factor in future survival, with large fast growing young-of-the-year walleye producing strong year classes and small slow growing fish producing weak year classes. An example of this occurred in 2010. Although the electrofishing catch was unusually low, the walleye were much larger than average and consequently it appears the 2010 year class will be stronger than average. The mean length of young-of-the- year walleye and the total number caught can be used in a predictive model that will give a good indication of how strong a year class will be. The mean length and total catch indicate the 2012 year class will likely be stronger than average on East Vermilion, and about average on West Vermilion. Figure 4. Electrofishing Catches of Young-Of-The-Year Walleye, 1988-2012. 7 Angling prospects for walleye look favorable in 2013. There are good numbers of 13-17 inch walleye in the population, especially on East Vermilion. Most of these fish are from strong year classes produced in 2007 and 2010. Prospects for catching quality sized fish (over 18 inches) are also favorable, especially on West Vermilion where there are still good numbers of fish in the population from strong year classes produced in 2002 and 2003. However, most of these fish are over 18 inches and must be released in order to comply with the special regulation on Lake Vermilion. The special walleye regulation on Lake Vermilion was modified in 2012 to an 18-26 inch protected slot, with one fish allowed over 26 inches, and a four-fish bag limit. The previous special regulation was implemented in 2006 and had a protected slot of 17-26 inches. The regulation change was prompted by angler concerns over catching keeper-sized walleye on West Vermilion. Due to strong reproduction in 2002 and 2003 and several years of poor to fair reproduction since then, the walleye population in that lake basin has been dominated by larger fish and anglers had difficulty catching walleye less than 17 inches long. The DNR agreed to review the regulation and see if the protected slot could be modified to allow harvest of larger fish while still meeting management goals for the lake. After considering all the biological data and public input, it was decided the 18-26 inch protected slot was the best choice to allow some additional harvest while keeping harvest at a safe level. The original special regulation was adopted because of increased fishing pressure and walleye harvest. Creel surveys in 2002 and 2003 documented the highest walleye harvest ever observed on Lake Vermilion, well above the safe harvest level established for the lake. Consistent harvest above the safe harvest target could negatively affect the walleye population. Creel surveys in 2008 and 2009 indicated the regulation did help keep harvest at a safe level. Walleye harvest will be documented again during the next cycle of creel surveys in 2014 and 2015. 8 Northern pike The 2012 gill net catch of northern pike was 0.7 fish/net, slightly below the historic average (Figure 5). Gill net catches of northern pike have historically been fairly stable at a relatively low level. West Vermilion usually has higher gill net catches of northern pike than East Vermilion, reflecting higher abundance in that lake basin. The mean length of northern pike in the gill net catch was 29.6 inches, well above the historic average. Over half of the northern pike sampled were over 30 inches long. Northern pike reproduction is usually fairly consistent from year to year, without exceptionally strong or weak year classes. Angling prospects for large northern pike are better than average in 2013, as gill net catches of large pike have been above average for several years. A special regulation for northern pike has been in effect since 2003: a 24-36 inch protected slot, with one fish allowed over 36 inches. The bag limit remains at three fish. The regulation is part of a statewide initiative to improve the size structure of pike populations in a number of lakes across the state. Lake Vermilion was chosen for this special regulation because of its potential to produce quality sized fish. An ice-out trap net assessment will be conducted in 2013 and 2014 to evaluate the regulation. Figure 5. Northern Pike Gill Net Catches, 1984-2012 9 Yellow perch The 2012 gill net catch of yellow perch was 23.2 fish/net, higher than catches in recent years, but still below the historic average (Figure 6). The improved perch catch in 2012 was due to a much higher catch on West Vermilion. The perch catch on East Vermilion remained well below average. Perch gill net catches are usually higher on West Vermilion, while the average size is larger on East Vermilion The mean length of gillnetted perch was 7.3 inches, which is near the historic average. The catch of 5-6 inch perch was well above average, especially on West Vermilion. Other size classes were poorly represented in the gill net catch. The high catch of small perch on West Vermilion was due to a strong 2010 year class. Prior to 2010, perch reproduction and survival had been poor for a number of years. Perch fishing is relatively insignificant on Lake Vermilion, with most of the harvest coming from anglers fishing for other species. There are more large perch in East Vermilion and most of the harvest comes from that lake basin. Perch in East Vermilion grow faster than West Vermilion perch, probably because they feed extensively on juvenile rusty crayfish that are abundant in that area of the lake. Perch are also an important prey item for several species of gamefish, including walleye and northern pike. Figure 6. Yellow Perch Gill Net Catches, 1984-2012 10 Smallmouth bass An electrofishing boat is used as the standard sampling gear for smallmouth bass because they are not often caught in standard assessment nets. The 2012 smallmouth bass catch was 36.5 fish/ hour of electrofishing, which is near the historic average (Figure 7). Electrofishing was not done on West Vermilion in 2012 due to poor weather during the time period scheduled for sampling. Smallmouth bass catches are usually higher on West Vermilion while the average size is larger on East Vermilion. Smallmouth bass sampled by electrofishing had a mean length of 11.6 inches, well above the historic average. Good numbers of 12-18 inch bass were sampled from strong year classes produced in 2002, 2003, 2005, and 2006. One year of sampling indicates the 2010 year class may be stronger than average as well. Weak year classes of smallmouth bass were produced in 2004, 2008, and 2009. Angling prospects for smallmouth bass look favorable in 2013. There are good numbers of medium sized and large fish in the population from several strong year classes. Anglers may catch fewer small fish than normal due to poor reproduction in 2008 and 2009. There is not a sampling program in place that targets largemouth bass. Recent creel surveys and angler reports indicate the largemouth bass population has increased, especially on West Vermilion. Figure 7. Smallmouth Bass Electrofishing Catches, 1989-2012 11 Muskie Muskellunge were not known to be native to Lake Vermilion, although there are some accounts of muskie being caught prior to 1960. The first muskie were first stocked in 1968. Leech Lake strain muskie have been stocked regularly since 1987. Muskie population assessments are done every 4-6 years on Lake Vermilion. Due to the large size of the lake, East Vermilion and West Vermilion are done in different years. An assessment was done on East Vermilion in 2011 and an assessment was done on West Vermilion in 2012. Muskie trapnet assessments target spawning fish in the spring shortly after ice-out. The 2011 muskie catch on East Vermilion was 2.8 fish net, while the West Vermilion catch in 2012 was 1.1 fish/net. Muskie trap net catches have been gradually increasing since they were introduced as more year classes recruit to the spawning stock. To date, muskie catches have been higher on East Vermilion, while the average size has been larger on West Vermilion. The mean length of trapnetted muskie was 44.9 inches on East Vermilion and 46.2 inches on West Vermilion. About 19% of the muskie sampled during the two surveys were over 50 inches long (Figure 8). The largest muskie sampled was 55.6 inches long. Figure 8. Muskie Length Frequency From Trap Nets, 2011-2012 12 Invasive Species There are several invasive species known to be present in Lake Vermilion. Rusty crayfish are very abundant in East Vermilion and are now expanding into West Vermilion. Curly-leaf pondweed is present in Everett’s Bay and Stuntz Bay in East Vermilion. Chinese mystery snails were discovered in 2011 in Spring Bay at the far west end of the lake. These invasive species were probably introduced by careless anglers or boaters. The DNR has taken several steps to prevent the spread of invasive species. It is illegal to transport water, plants, or animals from lake to lake. The DNR also established a program to inspect boats at some public accesses. Enforcement and education efforts have been increased. Guidelines were adopted to ensure DNR hatcheries and private aquaculture operations do not harbor or spread invasive species. Regulations were adopted that limit the use of smelt and cisco for bait. These species are known carriers of VHS, a virus that is lethal to many species of fish. There is now mandatory training on invasive species for lake service providers, including businesses that install or move docks and boat lifts. Legislation passed in 2011 increased funding for invasive species programs and increased penalties for violating laws related to invasive species. The Sportsmen’s Club of Lake Vermilion (SCLV) also has a monitoring program to keep invasive species out of Lake Vermilion. SCLV volunteers conduct voluntary boat inspections at public accesses several times a year. The SCLV has also used a variety of educational methods including billboards, brochures, and restaurant place mats to inform anglers and boaters about invasive species. Anglers and boaters should always take preventative measures to avoid moving water, plants, or animals to other lakes. Boats and trailers should be thoroughly cleaned or dried before moving to other bodies of water. All bilges and live wells must be drained. All drain plugs must be removed and left out for transport. For more information on invasive species and new regulations, go to the DNR website at mndnr.gov. 13 Cormorants In recent years there has been a large increase in the number of cormorants on Lake Vermilion. A nesting colony on Potato Is. grew from 32 nests in 2004 to 434 nests in 2012. Potato Is. is located in Big Bay in the eastern part of the lake. Many anglers and lake residents are concerned that high cormorant numbers might harm gamefish populations, especially walleye. Cormorants usually exist at population levels that do not significantly affect fish populations, however there have been cases where cormorants were linked to fish population declines. Cormorants are protected by the Migratory Bird Act, which makes unregulated killing of these birds illegal. Some limited control of cormorants is allowed in Minnesota through a depredation order managed by the U.S. Fish and Wildlife Service. However, there must be evidence of damage before control would be approved. There is mounting evidence that cormorant predation may be affecting yellow perch abundance in East Vermilion. Perch gill net catches have been persistently low in that lake basin since 2007, the same time period the cormorant population has been expanding. The Fisheries Research unit examined data from Lake Vermilion and concluded that cormorant predation was the most likely factor contributing to low perch abundance, although evidence of this link was not conclusive. Based on the decline in the perch population, the DNR is working with the U.S. Fish & Wildlife Service to develop a cormorant control program for Lake Vermilion. The goal of a control program would be to reduce cormorant numbers to a level that allows the perch population to recover, while still maintaining a viable cormorant nesting colony on Potato Island. 14 Walleye Stocking The Minnesota DNR operates a major walleye egg-take station and hatchery at the mouth of the Pike River on Lake Vermilion. Walleye produced at the hatchery are used for stocking programs in northeastern Minnesota and other areas of the state. A portion of the fry produced each year are stocked back into Lake Vermilion to mitigate egg removal from the lake. In recent years, 5-20 million walleye fry have been stocked into Lake Vermilion annually. A research project began in 2008 to evaluate walleye fry stocking on several lakes with egg-take stations, including Lake Vermilion. The project involves marking all walleye fry stocked back into the research lakes for five years. Walleye fry are marked by immersion in an oxytetracycline bath. This leaves a permanent mark on bony structures in the head that can be identified at later stages of life. The goals of the project are to determine how many walleye fry are produced naturally in these lakes and the optimal stocking rates to produce strong year classes. Because of water chemistry issues, marking was unsuccessful in 2008 and 2009. Adjustments were made in the methodology and good marks were attained in 2010, 2011, and 2012. Population estimates of naturally produced fry were made each year based on the ratio of marked and unmarked young-of-the-year walleye sampled by fall electrofishing. Population estimates of wild fry ranged from 474 fry/littoral acre in 2012 to 666 fry/littoral acre in 2010. The littoral area is the portion of the lake less than 15 feet deep and the most productive area of a lake. Total fry densities (wild + stocked) were over 1,000 fry/littoral acre each year. Strong year classes were produced on Red Lake and Leech Lake at total fry densities of 300-600 fry/littoral acre, much less than total fry densities on Lake Vermilion. While it is important to have sufficient walleye fry for producing good year classes, excessive stocking beyond that level is probably not productive and may actually be counter-productive by slowing growth and reducing survival. Fry marking was originally scheduled to end in 2012. However, because fry marking was unsuccessful in 2008 and 2009, fry will be marked again in 2013. 15 Habitat and Water Quality Preserving fish habitat and water quality continues to be a management priority on Lake Vermilion. The DNR has several programs that protect fish habitat and water quality by regulating shoreline alterations and the removal of aquatic plants. Aquatic vegetation and shallow near-shore areas both provide critical habitat for a number of fish species. Individual property owners can also take steps to manage their shoreline in an environmentally sound manner. Information can be found at the DNR website: mndnr.gov. Fishing Tournaments There are four fishing tournaments scheduled so far on Lake Vermilion in 2013. Permits from the DNR are needed for most fishing tournaments, and permits have been issued or applications received for the tournaments listed below. The DNR is responsible for regulating fishing tournaments and manages them in a manner that will protect fish populations and minimize conflict with other lake users. •May 18: City Auto Glass Walleye Classic, 125 boats. •May 19: MN Pro Bass Team Trail (Excel), 50 boats. •May 20: Super Slam Bass Tour, 50 boats. •August 17: Lake Vermilion Muskie Challenge, 50 boats. License Fee Initiative Most fishing and hunting license fees will be going up in 2013 due to legislation passed in 2012. These fee increases are essential for maintaining the integrity of Minnesota’s Game and Fish fund which was projected to “go negative” by as early as July 2013. About 95% of the operating budget of the Division of Fish and Wildlife comes from the Game and Fish fund. Without these fee increases significant cuts to programs that affect fishing and hunting would have been necessary. Fishing and hunting license fees had not been raised since 2001, the longest period without a fee increase in more than 40 years. The fee increases would not have been possible without the support of the state’s anglers, hunters, and outdoor organizations. Thank you for your support!