Lake Erie Walleye
Spring 2004 Issue
Walleye Fact File
Dead Zone Update
Lake Erie's dead zone has returned again this summer according to new research in Lake Erie's Central Basin. During a six-day survey in mid-August, scientists on US.EPA's Lake Guardian, found that only 20 percent of monitoring stations had the desired amount of four milligrams per liter (mg/L) of dissolved oxygen in the water. Forty percent of the stations showed less than half that amount. The lowest oxygen concentrations were discovered in the western portion of the Central Basin, where concentrations dropped to .7 mg/L.
Over the last two years, Lake Erie has experienced dead zones or areas of anoxia, where oxygen levels in thelake are too low for fish and other aquatic species to survive. Dissolved oxygen concentrations less than 2 mg/L are considered hypoxic and can threaten aquatic life that cannot move from the area.
The key is the amount of phosphorus that goes into the Lake, says Ohio Sea Grant researcher, Dr. David Culver. "The smaller the amount of phosphorus discharged into the lake, the less likely we will have a dead zone."
Unfortunately, even with regulations in place, phosphorus concentrations have been increasing since 1995. "Scientists are beginning to suspect that they might have underestimated the amount of phosphorus still entering the lake from sewage treatment and agricultural runoff," says Jeffrey Reutter, Director of Ohio Sea Grant and Stone Lab. "High levels of phosphorus increase the growth of algae, which in turn, increases the rate of oxygen consumption."
While phosphorus levels may be the key, other factors influence the magnitude of the dead zones. Lake Erie is functioning with less water due in part to global warming and falling water levels. The thickness and volume of the hypolimnion is reduced as water levels drop, resulting in less available oxygen. Thus, if water levels continue to decline, the anoxic area may cover less of the lake's bottom, but arrive earlier and last longer each year.
Another suspect of the Lake's dead zone may be the invasive zebra and quagga mussels. Early research results indicate that as mussels process organic matter, they excrete phosphorus into the water where it is repeatedly used instead of going into the sediments.
Predictions for next year are not encouraging. "Lake Erie has had quite an eventful summer this year," says Culver. It was first pounded by 10 inches of extra rainfall, 30 percent above its average. Then, the largest power outage in the US resulted in millions of gallons of raw sewage discharged into the lake and its tributaries. And at the same time, the western basin saw a growth of algal bloom, one of the largest in recent years. "These large nutrient inputs may mean next year's dead zone will develop earlier," emphasizes Culver.
Its severity, however, will depend on the amount of wind the lake will get in the spring. If the spring is extremely windy, the wave action will cause the warmer upper water layer (epilimnion) to mix heavily with the lower cooler layer (hypolimnion), resulting in a deeper thermocline. The deeper thermocline will mean a smaller volume of oxygen in the hypolimnion and an earlier dead zone.
For more details about the dead zone, request the dead zone excerpt in Highlighted Publications (page 2) or go to the 2002 Sept/Oct issue of Twine Line at www.sg.ohio-state.edu.
This article is reprinted from the September/October, 2003 issue of Twine Line, a publication of Ohio Sea Grant.
Steelhead Trout: A Money Fish for
Steelhead trout have been stocked into Lake Erie tributary streams since 1975 through a very successful program administered by the Ohio Department of Natural Resources, Division of Wildlife. The success of the program has grown over the years, resulting in increased stocking numbers and the addition of more streams. During 2003, over 400,000 steelhead smolts were stocked in five Lake Erie tributaries. This program provides Central Basin anglers with the opportunity to catch trophy class rainbow trout (steelhead) during the summer months in the open waters of Lake Erie, and in tributary streams during the fall, winter, and spring months. Over 98 percent of steelhead are caught are in Ohio's two lake districts (#2 and #3) that stretch from Huron to Conneaut.
Creel data is collected annually by the ODNR Division of Wildlife to assess open lake steelhead angler success. During 2002, private and charter boat anglers caught approximately 41,357 steelhead in the open lake; an increase of over 41 % compared to 2001, and the highest on record since the program began. When compared to past years harvest (1995 = 3,500 and 1997 = 4,000) the increased stocking has resulted in a significant benefit to angler harvest. Unfortunately, very little is known about the harvest of steelhead from tributaries.
To learn more about this steelhead stream fishery, Ohio Sea Grant initiated a research effort to survey these anglers during the 2002-2003 tributary angling season. This is the first time an economic survey of Ohio Lake Erie steelhead stream anglers has been conducted. While the state of Ohio and other Great Lakes states have intensive management programs aimed at enhancing the steelhead fishing experience for anglers, little is known about the tastes, preferences, and values of Ohio steelhead anglers
From October 2002 through April 2003, Ohio Sea Grant personnel contacted anglers at popular streamside locations (from Vermilion to Conneaut) seeking their participation in a survey to better understand steelhead angler fishing habits, economic expenditures, and angling/visitation needs. Anglers were asked basic creel data questions and were also asked to participate in a mail survey related to the day of contact and other seasonal angling questions. Overall, 487 anglers were contacted for survey participation, with 375 surveys returned.
Within the steelhead fishery, most anglers (94%) appear to take single-day trips. Due to the low number of respondents for multiple-day trips, the study has focused on single-day trips. Respondents on single-day trips indicated taking an average of 44 steelhead fishing trips per year. About 72% of the trips individuals take are taken to the site where individuals were intercepted. Most trips are taken in fall of 2002 and spring of 2003, with a smaller proportion taken in winter. This was largely because most, if not all of the prime steelhead fishing streams were frozen solid and unfishable in most of January, February, and much of March 2003.
Anglers indicate that they keep approximately 12% ofthe fish that they catch (7.1 fish kept vs 58.4 fish caught), and that they eat approximately 49% of the fish they kept (3.5 fish eaten vs 7.1 steelhead kept). Anglers catching relatively few steelhead tend to keep a higher percentage of the fish they catch than anglers who catch large amounts of steelhead.
The survey did not consider other types of fishing in which the individuals potentially engage, but it does provide information on the way individuals fish for steelhead. Approximately 65% of steelhead anglers spin cast with bait or artificial lures while a smaller proportion fly fish (30%). The average angler surveyed had 9.0 years experience fishing for steelhead.
Individuals responded that they spend approximately $26 per trip, with more than 60% of these expenditures within 10 miles of the sites where they are fishing, suggesting that each trip generates nearly $16 in local expenditures. For just the 311 _: visitors in our single trip angler sample, taking 44 trips per year on average, this generates $218,000 in annual expenditures locally on steelhead fishing. It is not possible, unfortunately, to extrapolate the expenditure values to all steelhead anglers since the sampling protocol provides no information on the proportion of the total population that fishes for steelhead. However, if as many as one percent of the 754,704 licensed resident anglers in Ohio in 2001 fished for steelhead this would give us a total of 7,547 anglers x 44 trips x $26 = $8.6 million.
The study explored the factors that affect steelhead catch rates and the value of steelhead fishing in tributaries to Ohio's portion of Lake Erie. Overall, the results suggest that steelhead fishing is a very valuable activity in Ohio. The travel cost model used estimated that the value per trip for anglers taking part in our study ranged from $36 to $50.
The study results also made it possible to consider the value of a single fish caught. On average, individuals in the sample catch 1.33 fish per trip. This suggests that the value of each fish caught ranges from $27 to $38 per fish. Over all fish caught by the anglers in just our survey (approximately 20,323), the estimated value of catching fish is $591,300 to $832,200. In 2002, ODNR Division of Wildlife stocked 411,601 fish, for a cost of approximately $590,000 per year. These results do not fully capture all benefits of the stocking program, but suggest that the benefits of stocking do outweigh the costs.
While these results suggest that steelhead angling is highly valued by a segment of anglers in Ohio, we cannot fully estimate the benefits for all Ohioans from the limited sample collected. In the future, more thorough data collection would provide information on other anglers who fish for steelhead less frequently. Further, it would be useful to have independently collected creel data to assist in benefit cost analysis of the stocking program. Finally, the results of the survey suggested strong differences in seasonal trips, and access to a variety of sites. Further evaluation of the timing of trips and access could provide additional useful information.
This article reprinted from the November/December 2003 issue of Twineline, a publication of Ohio Sea Grant and was authored by Dave Kelch & Frank Lichtkoppler, Ohio Sea Grant Extension; and Brent Sohngen & Adam Diagneault, Ohio State University.