Phone: 989-356-5102 |
Evaluation
of Lake Sturgeon in the Detroit River
as Reported by Sport Anglers
March 1999
Tracy Hill
Fishery Biologist
U.S. Fish and Wildlife Service
Fishery Resources Office
Alpena, Michigan
tracy_hill@fws.gov
Provisional data, not to be cited without permission.
Introduction
Lake sturgeon (Acipenser fulvescens) were historically abundant throughout the Great Lakes and their connecting waterways, but loss of habitat, over-fishing, and water pollution greatly reduced sturgeon numbers. Lake sturgeon populations are now estimated to be about 1% of their former abundance (Tody 1974). They are listed as either threatened or endangered by 19 of 20 states in their original range (Auer 1991). Lake sturgeon have been identified as a species of special concern by the U.S. Fish and Wildlife Service and are considered a threatened species in North America by the American Fisheries Society (Williams et al. 1989). Remnant, free-ranging, riverine spawning populations of Great Lakes lake sturgeon are now known to exist in only a few tributaries to southern Lake Superior, the St. Clair River and the St. Lawrence River. Recent increases in incidental catch of young, genetically unique, juvenile lake sturgeon indicates that recruitment is now occurring in western Lake Erie. The source of this recruitment is undetermined but is speculated to be associated with the lower Detroit River.
Seven historical lake sturgeon spawning sites were identified in the Detroit River by Goodyear et al. (1982), however, no assessment has been conducted to evaluate current use of these sites by lake sturgeon, or the present habitat condition of these sites. Identification and qualitative assessment of habitats utilized by the various life stages of any species is critical for successful recovery efforts, and for guidance of habitat protection, enhancement or restoration efforts.
Lake sturgeon are frequently encountered by sport fishers in U.S. and Canadian waters of the Detroit River and some target fishing is known to occur. However, essentially no biological information is available on this population and no knowledge exists relative to the connection or contribution of this population to those existing in the St. Clair system or western Lake Erie. The U.S. Fish and Wildlife Service-Alpena Fishery Resources Office (FRO) in cooperation with U.S. Geological Survey-Biological Resources Division-Great Lakes Science Center (GLSC) initiated a project in the fall of 1998 to begin filling the data gaps on Detroit River lake sturgeon and their habitats. This project will have long range benefits to basin-wide efforts to restore the species and protect remnant critical habitats.
Staff from the Alpena FRO initiated contact with local sports groups in the lower Detroit River in the Fall of 1998 to inform them about and solicit their assistance on a lake sturgeon project. Local anglers who specifically target lake sturgeon were identified as a result of these contacts. Three anglers agreed to tag and collect information on the lake sturgeon that they captured. This report details information collected on lake sturgeon captured by those anglers in 1998.
Methods
All lake sturgeon were captured using hook and line. Anglers fished from boats using dead bait, usually blunt nose minnows Pimephales notatus. Angling began in late-September and ended in early-December. Most fish were captured between 1800 and 2400 hours. Total length (TL), fork length (FL), and girth were measured, to the nearest cm, for all captured lake sturgeon. Weight was recorded to the nearest kilogram. The leading (marginal) ray of the left pectoral fin was removed from each fish to provide estimates of age. Distal portions of the fin ray was preserved in Sarcosyl for genetic analysis. All fish were tagged in the left operculum with a serially numbered Monel self-piercing animal ear tag (National Band and Tag CO., Newport, Kentucky). All lake sturgeon were released unharmed back into the Detroit River.
All materials necessary to collect the biotic information was provided by the Alpena FRO. The anglers were provided a box containing; instructions for fish tagging and fin ray removal, tags and an applicator, fin ray removal saw, data notebook and cards, fin ray envelops, a soft measuring tape and a disposable camera. Abiotic data recorded for each lake sturgeon captured included; date, latitude/longitude, water depth and temperature, and bottom type. In addition, tag type, agency, and identification number of tag applied to the fish was also recorded.
Size and arrangements of bottom substrates at five of the seven reputed lake sturgeon spawning sites was assessed in October 1998 using a 100-kHz side scan sonar, following methodology in Edsall et al. (1997).
Foods vomited by captured lake sturgeon in the holding tank were preserved in 10% buffered formaline and identified under a dissecting microscope.
Results and Discussion
A total of 21 lake sturgeon were captured in 25 fishing trips. Fork length of these fish ranged from 51 cm to 135 cm with a mean fork length of 106 cm (Figure 1). Age of lake sturgeon captured in the lower Detroit River ranged from 2 to 22 years with a mean of 12 years (Figure 2). A summary of morphological data collected from the lake sturgeon are shown in Table 1.
Figure 1. Length frequency of 21 Detroit River lake sturgeon captured by anglers between 30 September and 10 December 1998.
Figure 2. Age frequency of 21 Detroit River lake sturgeon capture by anglers between 30 September and 10 December 1998.
Table 1. Summary of morphological data collected from 21 Detroit River lake sturgeon captured by anglers between 30 September and 10 December 1998.
| Variable | Mean |
Median |
Range |
| Fork Length (cm) | 106 |
108 |
51 - 135 |
| Total Length (cm) | 116 |
119 |
58 - 148 |
| Girth (cm) | 43 |
44 |
20 - 57 |
| Weight (kg) | 11 |
11 |
1 - 20 |
| Age (years) | 12 |
13 |
2 - 22 |
Biotic parameters were collected to assist with data exchange among other agencies involved in lake sturgeon status surveys. Several relationships were developed with these parameters to aid information exchange between the agencies. Figures 3 and 4 illustrate weight-girth and weight-age relationships, respectively. These relationships will be compared with similar relationships produced for other lake sturgeon populations (St. Clair Waterway, southern Lake Huron and Saginaw Bay) in the central Great Lakes.
Figure 3. Girth to weight relationship for 21 Detroit River lake sturgeon captured by anglers between 30 September and 10 December 1998.
Figure 4. Age to weight relationship for 21 Detroit River lake sturgeon captured by anglers between 30 September and 10 December 1998.
Preliminary examination of the side scan survey data revealed that bottom substrates at the heads of islands were clean gravel and sand, underlain by limestone shelf rock. In deeper channel areas, the bottom was featureless sand and clay with occasional gravel patches.Foods vomited by captured lake sturgeon in decreasing order of occurrence included whole and crushed zebra mussel Dreissena polymorpha shells, snail shells, and fish remains. Also discharged with these foods were fine gravel, sand cinders, leaves and organic fibers.
Summary
The excellent cooperation provided by the Detroit River anglers provided important information on the lake sturgeon population in this area of the central Great Lakes. Although the data is biased by the collection technique, they are valuable information. The age distribution of the lake sturgeon collected from the Detroit River described sub-adult lake sturgeon too young to spawn. Anglers provided a photograph of an adult female captured in May 1998 in the Detroit River that weighed 264 kg (120 lb), was 188 cm (74 inches) in length, and gravid with eggs. Hence, lake sturgeon in spawning condition occupy the river in May. Lake sturgeon of all sizes were collected from a site in the lower river in October and early November but could not be caught by hook and line after 8 November 1998. Lake sturgeon that were captured by the anglers were growing logarithmically and appeared to be in excellent condition. Zebra mussels appear to be a common food of lake sturgeon in the Detroit River. Several fish bore scars of lamprey Petromyzon sp. attacks.
ACKNOWLEDGMENTS
The information presented in this report was collected entirely though the voluntary assistance of Detroit River lake sturgeon anglers. Their cooperation, interest, and enthusiasm was invaluable to the initiation of this project. The authors wish to thank them for their assistance.
REFERENCES
Auer, N.A. 1991. Conservation of the threatened lake sturgeon. Michigan Department of Natural Resources, Nongame Wildlife Fund and Living Resources Small Grants Program. Final Report, Lansing.
Edsall, T.A., T.E. Behrendt, G. Cholwek, J.W. Frey, G.W. Kennedy, and S.B. Smith. 1997. Use of remote-sensing techniques to survey the physical habitat of large rivers. U.S. Geological Survey, Great Lakes Science Center, 1451 Green Road, Ann Arbor, Michigan, Contribution No. 983. 20 pp.
Goodyear, C.S., T.A. Edsall, D.M. Ormsby Dempsey, G.D. Moss, and P.E. Polanski. 1982. Atlas of the spawning and nursery areas of Great Lakes fishes. Volume 5, Lake Huron. U.S. Fish and Wildlife Service, Washington, D.C.
Tody, W.H. 1974. Whitefish, sturgeon, and the early Michigan commercial fishery. Pages 45-60 in Michigan Fisheries Centennial Report 1873-1973. Michigan Department of Natural Resources, Lansing.
Williams, J.E., J.E. Johnson, D.A. Hendrickson, S. Contreras-Balderas, J.D. Williams, M.Navarro-Mendoza, D.E. McAllister, and J.E. Deacon. 1989. Fishes of North America, endangered, threatened, or of special concern. Fisheries 17(6):2-20.
