Lake Sturgeon Status Survey in Michigan Waters of Lake Huron
as Reported by Commercial Fishers

March 2000

Tracy Hill and Scott Koproski
U.S. Fish and Wildlife Service
Fishery Resources Office
Alpena, Michigan
scott_koproski@fws.gov

Provisional data, not to be cited without permission.

Introduction

There are 27 species of sturgeon worldwide, nine are endemic to North America, however, only the lake sturgeon, Acipenser fulvescens, is native to the Great Lakes basin. Lake sturgeon is the only sturgeon species which lives its entire life in freshwater (Auer 1999). Lake sturgeon once ranged throughout the Mississippi River, Hudson Bay and the Great Lakes basin (Harkness and Dymond 1961; Scott and Crossman 1973). Once an abundant member of the Great Lakes fish community, lake sturgeon were, and continue to be, commercially valuable and can provide tremendous sport fishing opportunities (Auer 1999). This species has and continues to represent an important biological component of the Great Lakes fish community. By the early 1900's many populations of lake sturgeon throughout their range had been greatly reduced or extirpated as a combination of overfishing, habitat loss, the construction of dams, and pollution (Ono et al. 1983). Lake sturgeon are listed as either threatened or endangered by 19 of the 20 states within its original range in the United States (Auer 1991). The American Fisheries Society considers lake sturgeon a threatened species in North America (Williams et al. 1989). Considered relicts, fossil evidence suggests sturgeons existed one hundred to two hundred million years ago (Auer 1999).

Sturgeon retain many characteristics of primitive fishes. They possess a shark-like heterocercal tail, bony scutes along their head, back and sides, a cartilaginous skeleton, and a toothless, protrusible mouth (Auer 1999). Lake sturgeon are the largest freshwater fish in the Great Lakes basin. They feed on chironomid larvae, molluscs, mayfly nymphs, caddisfly larvae, crustaceans, and fish (Harkness and Dymond 1961; Thomas and Haas 1999). Lake sturgeon are late maturing, slow-growing, long-lived fish that reach ages of 100-150 years (Guenette et al. 1993). Unlike many fishes, lake sturgeon require fifteen to twenty-five years to reach maturity and are intermittent spawners (Priegel and Wirth 1977).

The U.S. Fish and Wildlife Service-Alpena Fishery Resources Office (FRO) began investigating the Lake Huron lake sturgeon population in 1995. The purpose for the study was to gather critical information on Lake Huron lake sturgeon necessary for determination of federal listing and the development of recovery plans. Previous year's reports for this project can be found on the Alpena FRO web page (www.fws.gov/midwest/alpena/index.html) under station reports.

 

Study Site

Lake Huron is the second largest (by surface area) of the Great Lakes with a total surface area of 59,596 km². It is a deep oligotrophic lake, with a mean depth of 59 m and depths greater than approximately 30 m over two-thirds of its surface (Berst and Spangler 1973). Lake Huron lies in the center of the Great Lakes and receives discharge from both Lakes Superior and Michigan (Eshenroder et al. 1992).

Most of the lake sturgeon collected for this study came from Saginaw Bay, Lake Huron (Figure 1). Saginaw Bay is one of the largest bays in the Great Lakes. It is a shallow, well-mixed extension of the western shoreline of Lake Huron. Total area of the bay is 2,771 km², and total water volume is 24.5 km³. Bottom substrates in Saginaw Bay range from silt to mostly cobble and rock.

 

 

 

Methods

Lake sturgeon monitoring continued in 1999 for the fifth straight year. Similar to previous years, all lake sturgeon were collected by commercial fishers as by-catch in their trap net fishery (Hill and McClain 1998). Michigan state-licensed commercial fishers use large commercial trap nets to capture fishes. Lake whitefish Coregonus clupeaformis, yellow perch Perca flavescens, and channel catfish Ictalurus punctatus are the species primarily targeted by the trap net fishery. Lake sturgeon are often encountered as by-catch during normal fishing operations. This has allowed Alpena FRO staff an opportunity to obtain information from this prehistoric fish. Total length (TL), fork length (FL), and girth were measured for all captured lake sturgeon. The leading (marginal) ray of the left pectoral fin was removed from each fish to provide estimates of age. The distal portion of the fin ray is being utilized 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 handled by the commercial fishers, including data collection and fish tagging. All materials necessary to collect the biotic information was provided by the Alpena FRO (Figure 2). Each fisher was provided a box containing instructions for fish tagging and fin ray removal, tags and an applicator, fin ray saw, data note book 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 or observed (if fish was tagged) was recorded as well.

To maximize the information being collected on Lake Huron lake sturgeon, the Alpena FRO has been working closely with the Ontario Ministry of Natural Resources-Lake Huron Management Unit (OMNR-LHMU). Coordination between OMNR-LHMU and the Alpena FRO resulted in standardized data collection for lake sturgeon. This coordination enhanced the chances of recovering tag information from both sides of the lake and allowed a better understanding of the seasonal movement patterns of Lake Huron lake sturgeon.

 

Results and Discussion

Assistance from commercial fishers has been invaluable to the success of this study. Eleven commercial fishers (operating 18 boats) are providing information on incidentally captured lake sturgeon; nine of these fishers operate in Saginaw Bay. One new fisher began assisting with the project in 1999 (Table 1). Biological data were recorded from 45 lake sturgeon in 1999. The total number of lake sturgeon tagged increased slightly in 1999 compared to 1998 and was second to 1997 in total number of sturgeon tagged in one season. Since 1995, a total of 194 lake sturgeon have been tagged by commercial fishers.

 

 

Table 1. Number of lake sturgeon tagged by participating commercial fishers in Lake Huron trap net fishery since 1995. Dash indicates the fisher was not participating in the program.

Fisher	Year Enrolled	1995	1996	1997	1998	1999	Total
Barbeaux Fishery	1996	-	1	7	0	0	8
Bay Port Fish Company	1995	13	7	10	8	12	50
Beardsley Fish Company	1997	-	-	0	0	0	0
Cederville Fish Company	1997	-	-	1	7	9	17
Gauthier-Spaulding Fishery	1995	2	0	2	2	4	10
Kuhl Fishery	1999	-	-	-	-	1	1
Lentz Fishery	1995	3	8	8	9	10	38
M&W Fish Company*	1995	1	3	4	4	2	14
Serafin Fishery	1996	-	10	17	3	4	34
Beers Fishery	1995	2	0	1	0	0	3
Whytes Fishery	1995	2	7	3	4	3	19
Total		23	36	53	37	45	194

*Formerly Sam’s Fishery

 

Fork length of lake sturgeon captured in 1999 ranged from 41 cm to 185 cm with a mean fork length of 106 cm (Table 2). Age of these fish ranged from 3 to 30 years with a mean of 15 years. A summary of morphological data for lake sturgeon captured during the five years of this study are shown in Table 2. Figures 3 and 4 illustrate the length frequency and age frequency, respectively, of lake sturgeon collected during the course of this study. Biotic parameters which were collected from the lake sturgeon have been standardized to assist with data exchange among other agencies involved in sturgeon status surveys. Several relationships were developed with these parameters to aid information exchange between the agencies. Figures 5 and 6 illustrate total length-fork length and girth-fork length relationships, respectively. These relationships are similar to information collected by OMNR-LHMU for Ontario waters of Lake Huron (Lloyd Mohr, personal communication).

 

 

Table 2. Summary of morphological data collected on lake sturgeon by commercial fishers in Michigan waters of Lake Huron. Dash indicates data was not collected.

	1995	1996	1997	1998	1999
Mean Fork Length (cm)	111	92	101	111	106
Median Fork Length (cm)	111	90	99	109	103
Fork Length Range (cm)	71 - 155	50 - 135	42 - 185	67 - 171	41 - 185
Mean Age (years)	-	-	17	14	15
Median Age (years)	-	-	13	12	13
Age Range (years)	-	-	4 - 72	4 - 59	3 - 30

 

Figure 3. Length frequency of 194 Lake Huron lake sturgeon captured as by-catch in the trap net fishery, 1995-1999.

 

Figure 4. Age frequency of 95 Lake Huron lake sturgeon captured as by-catch in the trap net fishery, 1997-1999.

 

Figure 5. Fork length to total length relationship for Lake Huron lake sturgeon captured as by-catch in the trap net fishery, 1995-1999.

 

Figure 6. Fork length to girth relationship for Lake Huron lake sturgeon captured as by-catch in the trap net fishery, 1995-1999.

 

 

Weight information is limited for the lake sturgeon collected during this study because the commercial fishers collecting the data are not equipped to record weight information. However, biologists working with lake sturgeon in Ontario waters of Lake Huron have developed an equation to predict weight of sturgeon based on total length and girth measurements. The equation is as follows:

Log (Weight)=Log (Total length) X 2.44499+Log(Girth) X 1.00584 - 21.1645

where weight is in kg and total length and girth are in mm.

Overall, the age distribution of lake sturgeon caught in 1997, 1998 and 1999 is dominated by sturgeon older than 11 years with a total of 29 year-classes represented (Figure 4). Lake sturgeon younger than 8 years old represent 13% of the sturgeon sampled in the trap net fishery. This may be due to poor recruitment, gear selectivity, distribution of young sturgeon, or it may indicate that Saginaw Bay is merely a staging area for sub-adult lake sturgeon.

Seventeen previously tagged lake sturgeon have been recaptured in Saginaw Bay, the Main Basin and North Channel of Lake Huron (Table 3). All tagged lake sturgeon recaptured by Michigan state-licensed commercial fishers have been released unharmed. Coordination between OMNR-LHMU and the Alpena FRO on the lake sturgeon project in Lake Huron has provided documentation of interbasin movement of sturgeon between Saginaw Bay, the Main Basin and North Channel. Serafin Fishery has tagged five lake sturgeon that have been recaptured by other fishers (Figure 7). Three of these fish (4036, 4041 and 4043) have exhibited interbasin movement. Purdy Fisheries recaptured two of the fish (green and yellow) the third fish (blue) was found dead near Grand Bend, Ontario. The remaining two lake sturgeon (red and purple) were recaptured in Saginaw Bay. Purdy Fisheries have tagged two lake sturgeon in the southern Main Basin of Lake Huron that have been recaptured in Saginaw Bay (Figure 8). Fish number 485 (yellow) was tagged by Purdy Fisheries in southern Lake Huron and then recaptured by Cedarville Fishery in Saginaw Bay. Fish number 285 (red) was tagged by Purdy Fisheries on 22 October 1996. It was recaptured by Lentz Fishery on 6 June 1997. On 6 April 1999, it was again encountered in a commercial trap net north of Green Bay, Wisconsin, in Lake Michigan (grid 706, Robert Elliott, personal communication). This fish represents the first known documented case of significant upstream movement by a lake sturgeon. Several lake sturgeon that have been tagged in the Great Lakes have exhibited downstream movement (Ron Bruch, WI DNR; Lloyd Mohr, OMNR; Mike Thomas, MI DNR; Dave Davies, OH DOW, personal communications). Fish 161 exhibited movement between the North Channel and Northern Main Basin of Lake Huron (Table 3). In 1999, 7 lake sturgeon were recaptured by commercial fishers. This represents the greatest number of lake sturgeon recaptured by the Michigan state-licensed commercial fishers during a single season since the project began in 1995.

 

 Table 3. Summary of lake sturgeon recapture information.

 

Tag Number	Date Tagged	Date Recaptured	Tagging Grid	Recapture Grid	Tagging Fisher	Recapturing Fisher
FWS00036	10/4/95	8/17/96	1509	1606	Bay Port	M&W
FWS00049	9/28/95	12/25/97	1608	1606	Bay Port	Sport Angler
161	6/4/96	10/15/97	212	306	Nyman	Barbeaux
285	10/22/96	6/6/97	2016	1408	Purdy	Lentz
485	7/17/99	11/9/99	2015	1509	Purdy	Cedarville
4033	10/29/96	5/22/97	1508	1508	Serafin	Serafin
4036	4/26/97	10/6/97	1508	2016	Serafin	Purdy
4041	7/2/97	10/6/97	1508	2016	Serafin	Purdy
4043	8/25/97	8/28/98	1508	1919	Serafin	OMNR
4047	10/6/97	6/3/99	1408	1507	Serafin	Lentz
4059	5/4/98	5/20/99	1508	1509	Whytes	Cedarville
4087	10/4/98	10/6/98	1508	2016	Bay Port	Purdy
4110	11/17/98	10/11/99	1507	1507	Lentz	Lentz
4114	9/20/98	4/26/99	1507	1508	Lentz	Bay Port
4125	6/23/97	9/29/97	1508	1509	Lentz	Bay Port
4159	10/12/98	4/20/99	1609	1508	Cedarville	Bay Port
4168	10/31/99	11/1/99	1509	1509	Cedarville	Cedarville

 

Figure 7. Lake sturgeon tagged by Serafin Fishery. The "#" represents tagging location, "C" indicates recapture locations. Colors denote individual fish.

 

Figure 8. Lake sturgeon tagged by Purdy Fisheries. The "#" indicates tagging location, "C" indicates recapture locations. Colors denote individual fish.

 

Data collected on lake sturgeon by our commercial fishing partners are biased because the fishers are not targeting sturgeon. The lake sturgeon are captured as by-catch while the fishers are targeting other fish species. There are, however, temporal differences in habitat overlap between lake sturgeon and the commercially targeted species. The greatest overlap occurs in the spring and fall period. Lake sturgeon are captured most frequently in May and October (Figure 9). This temporal information may prove useful in developing sampling protocol for assessment activities targeting lake sturgeon.

 

Figure 9. Number of lake sturgeon captured by Lake Huron commercial fishers, 1995-1999.

 

Summary

The cooperation and assistance provided by Lake Huron commercial fishers provides crucial information on the lake sturgeon populations in Saginaw Bay and the northern regions of Lake Huron. Lake sturgeon appear to be less abundant in U.S. waters of Lake Huron than in Canadian waters based on by-catch return data. This is not surprising given that historically important spawning streams in Michigan have been blocked by hydropower projects. Several large streams with available spawning habitat are still free-flowing in Ontario, providing some degree of sustainability for lake sturgeon populations.

Increasing participation by commercial fishers should result in an escalation of lake sturgeon reports over the next few years. As the project continues and more lake sturgeon are tagged, additional information on seasonal movement should result from increased recaptures of previously tagged fish. In addition, collaboration between OMNR-LHMU and the Alpena FRO on the lake sturgeon project has begun to define movements of tagged sturgeon between the different basins of Lake Huron.

Despite the limited number of tagged lake sturgeon (194), a few discernible biotic and abiotic trends are developing. Personal discussions with the fishers indicate that small lake sturgeon have been observed in years prior to the initiation of this project. Although the mean age of captured lake sturgeon is 15 years, this mean was calculated from a small number of fish and may not represent the true age structure of the sturgeon population. Continued collection of age information should provide evidence of local recruitment in Michigan waters of Lake Huron if it is occurring. In addition, a few clusters of lake sturgeon captures are identifying areas that should be more closely examined for their habitat value to existing lake sturgeon populations and the possibility of supporting successful lake spawning stocks.

Expansion of the Alpena FRO and OMNR-LHMU efforts for lake sturgeon status surveys in the next few years will aid in understanding the current status, and the potential for a successful lake-wide recovery effort for this important native species.

 

Acknowledgements

The information presented in this report was collected entirely though the voluntary assistance of Barbeaux Fishery, Bay Port Fish Company, Beardsley Fish Company, Cederville Fish Company, Gauthier-Spaulding Fishery, Lentz Fishery, Kuhl Fishery, M&W Fishery, Serafin Fishery, Beers Fishery, and Whytes Fishery. Their cooperation, interest, and enthusiasm continue to be invaluable in defining the current status and trends of this native Lake Huron fish species. The authors wish to thank Aaron Woldt for providing GIS analysis and maps of the recapture information.

 

References