1. Project Title: Evaluation of Tawas Artificial Reef as Fish Spawning Habitat
2. Contact
Neal R. Foster or Gregory W. Kennedy
National Biological Service, Great Lakes Science Center (NBS-GLSC), 1451 Green Rd., Ann Arbor, MI 48105, USA
Tel.: (313) 994-3331, ext. 264 (NRF) or ext. 215 (GWK); FAX: (313) 994-8780;
E-mail: (cc-mail) R8 NFRC.GL or nealfost@umich.edu
3. Agencies Involved
Walleyes for Iosco County, c/o Walter Snow, 1746 Cowan Drive, National City, MI 48748, USA
Michigan Sea Grant Extension Office, Cooperative Extension Service, P.O. Box 599, Tawas City, MI 48764, USA
Michigan Department of Natural Resources (DNR), Alpena Fisheries Station, 4343 M-32 West, Alpena, MI 49707, USA
U.S. Fish and Wildlife Service (FWS), Alpena Fisheries Resources Office, Federal Building #203, Alpena, MI 49707, USA
National Biological Service, Great Lakes Science Center (NBS-GLSC), 1451 Green Rd., Ann Arbor, MI 48105, USA
4. Restoration Goal
Installation of a rock-rubble reef to enhance fish spawning and reproduction and to improve fishing opportunities in nearshore, protected areas.
5. Project Type
Conduct a study of the project area to determine effects of the reef placement on aquatic biota and habitat in the surrounding bay. Assess use by and behavior of fish during spawning on Tawas reef using a remotely operated vehicle (ROV) with underwater video camera. Determine egg deposition on the reef using egg traps. Conduct an egg/fry survival study on the reef using fry traps. Conduct a mark-recapture study of adult lake trout during the spawning period.
6. Background and Rationale
In August 1987, the Michigan DNR, with the assistance of a local sportsfishing organization, Walleyes for Iosco County, constructed Tawas artificial reef to improve recreational fishing in Tawas Bay. Post-construction assessment netting by the Michigan DNR during fall 1987-89 found dense aggregations of lake trout closely associated with the reef. In spring 1990-91, the Michigan DNR conducted fry trapping to document any successful reproduction on the reef. Live lake trout and lake whitefish fry were collected in these traps. In fall 1989, the Michigan DNR asked the NBS-GLSC to observe activity and behavior of these fish with the ROV, and possibly to determine if any spawning activity was taking place on the reef. An assessment to determine the extent of egg deposition by lake trout (and lake whitefish) on Tawas reef was performed during 1989-1993.
7. Regulatory Considerations
The Michigan DNR was the permitting agency for construction of the reef; they were also the lead agency involved in pre- and post-construction biological assessment. The NBS-GLSC provided pre- and post-construction habitat/substrate assessment and further biological assessment.
8. Criteria
Create habitat suitable for walleye (and other fish species) spawning, protection, and survival. Improve local angling success by creating habitat that would attract desirable fish species to more accessible areas.
9. Project Design
The Michigan DNR supervised materials selection, construction of the reef, and performed the initial gill net assessments. The NBS-GLSC designed the spawning behavior/egg deposition study. The behavioral study used the ROV to obtain video observations of lake trout during the spawning period, fall 1989-1993. The observations included (1) estimation of relative density of lake trout in the vicinity of the reef versus in the surrounding "sand flats" area of the bay and (2) direct observation of prespawning behavior on the reef with comparison to observations made on fish at natural reef sites and under laboratory conditions. The egg deposition study was conducted during fall 1990-1993, using two hundred 20.3 cm diameter, individually numbered egg traps set on the reef and on the surrounding sand substrate. Data collected included trap location, numbers of lake trout and lake whitefish eggs (live and dead), macroinvertebrates (including zebra mussels), trapped fish, and relative amounts and composition of sediment and detritus in each trap. The FWS (with assistance from NBS-GLSC and the Michigan DNR) initiated a mark-recapture study to document the presence and relative abundance of naturally produced (no finclip) adult lake trout that may be present at the reef during the spawning period. This study began in fall 1992, and is presently (1995) ongoing.
10. Implementation
The construction of the Tawas artificial reef occurred within 1 day, in August 1987 (Figure 1). By October of that year, lake trout began congregating around the reef area in significantly greater numbers than elsewhere in the bay. Fry traps were set, by divers, in the Spring 1990-91, over a 2-4 week period (April/May) to collect larval fish that may have been produced on the reef. The study to observe lake trout prespawning behavior and egg deposition began in October 1989. ROV operations occurred at night for 1 to 2 nights, usually around the period of peak lake trout concentrations on the reef. Egg traps were generally set from mid-October through late November, a period that included all spawning activity of lake trout and most spawning activity of lake whitefish. Traps were set in gangs (chains) of 25 (1991-1993) to 50 (1990) traps per gang and deployed and retrieved from a small boat. The ROV was used to document the position of each trap relative to the reef. The mark-recapture study was initiated in the fall 1992, and was performed over a 3-week period (2-3 nights/wk) encompassing the lake trout spawning period (mid-October through early-November). Fish were collected using a 91-183 m gill net set along the length of the reef. Nets were set after dark, and never exceeded more than 4 hours in the water to minimize fish casualties.
11. Degree of Environmental Intervention
The introduction of about 3 628 tonnes of limestone rock (15-30 cm dia) was accomplished using a self-unloader freighter. The rock was deposited in one continuous pile, approximately 450 m in length. While occupying a relatively small area relative to the size of the bay, the structure of the immediate area is quite different from what it was prior to construction of the reef.
The east end of the reef area has shown an increase in the density
and composition of aquatic macrophyte growth and accompanying
settlement of finer-grained sediments than was present before
installation of the reef. The reef itself has also become infested
with zebra mussels, which were first detected on the reef in 1991.
The effect that zebra mussels will have on the reef and surrounding
biota has not yet been determined. However, the bay as a whole
has shown little or no change as a result of reef construction.
12. Cost
The Tawas artificial reef cost an estimated $40 000 to build; however, much of the design, engineering, and materials were donated, making the actual cost difficult to determine. The per-year cost estimate for the behavior/egg deposition study is about $35 000, which includes about 2 months time for four researchers (about 5-10 days in the field, the rest for data processing and analysis), travel, equipment, and boat costs.
13. Biological Assessment
A 4-year study to document the use and usefulness of the Tawas artificial reef as a fish spawning site was performed. Qualitative underwater observations with an ROV of lake trout prespawning behavior helped in understanding physical and biological habitat conditions necessary for lake trout reproduction. Quantitative assessment with egg traps of egg deposition patterns further evaluated habitat and spatial preferences. Methodology and results of this study are detailed in a published manuscript (See "Key References"). In addition, assessment and documentation of fry production has been performed, indicating egg survival through the winter is possible on Tawas reef. Finally, assessment of the returning adult lake trout population has been initiated (1992) and is ongoing. Worthwhile additions to the assessment would be seasonal ichthyoplankton net tows and short-term gill net sets to determine utilization of the reef by other fish species.
14. Measures of Success
Relatively consistent numbers of lake trout eggs have been collected in the egg traps every year at Tawas reef. ROV surveys also documented a relatively stable, dense lake trout population congregating on the reef during the spawning period. The ROV and mark-recapture surveys also confirm that the population currently consists of about 99% hatchery produced.(i.e., finclipped) adults. Documentation of naturally produced (i.e., no finclip) adult lake trout returning (presumably homing) to the reef would be the most critical evidence that the artificial reef has actually enhanced lake trout production in Tawas Bay.
(Lake trout)
Success Rating: 4
The project was successful in creating lake trout spawning habitat. It is still unknown whether egg deposition on the reef has resulted or will result in an increased proportion of wild (unfinclipped) spawners.
(Walleye)
Success Rating: 3
The original goal of the reef was increased walleye production / angling success; however, little is known about the reef as a walleye attractor or as a site for walleye reproduction.
15. Key References
Foster, N.R., and Kennedy, G.W. 1995. Egg deposition by lake trout and lake whitefish at Tawas Artificial Reef, Lake Huron, 1990-1993, p. xx-xx. In T. Edsall, M. Munawar, and J. Leach [editors]. Lake Huron Basin Symposium, September 1993. Elsevier Books. (In press)
Marsden, J.E., Krueger, C.C., and Hawkins, H.M. 1991. An improved trap for passive capture of demersal eggs during spawning: an efficiency comparison with egg nets. N. Amer. J. Fish. Manage. 11: 364-368.
Perkins, D.L., and Krueger, C.C. 1995. Dynamics of reproduction by hatchery-origin lake trout (Salvelinus namaycush) in Lake Ontario. J. Great Lakes Res. (In press)
Schreiner, D., Bronte, C.R., Payne, N.R., Fitzsimons, J.W., and Casselman, J.M. 1995. Use of egg traps to investigate lake trout spawning in the Great Lakes. J. Great Lakes Res. (In press)
Correct citation for this contribution:
Foster, N.R., and Kennedy, G.W. 1995. Evaluation of Tawas artifical reef as fish spawning habitat, p. 267-271. In J.R.M. Kelso and J.H. Hartig [editors]. Methods of modifying habitat to benefit the Great Lakes ecosystem. CISTI (Can. Inst. Sci. Tech. Inf.) Occas. Pap. No. 1.