Figure 1. Trawl locations ("S" represents trawls not capturing sturgeon, "G" represents trawls capturing 1 or more sturgeon) on Lake St. Clair from 1996 to 1999.

 

 

Figure 2. Year class frequency for lake sturgeon captured in the St. Clair River and Lake St. Clair from 1997 through 1999. Ages based on pectoral fin ray sections.

 

2000

2000 will be the fourth year of the current five year federal aid project. Our field sampling effort will be similar to 1999, with setline and trawl surveys continuing on the St. Clair River and Lake St. Clair. The adult telemetry project has been strengthened with the addition of EPA funding for a graduate student at UM. We also plan to focus more on characterizing the habitat in the "sturgeon hole" area of Lake St. Clair to help us understand why sturgeon are so commonly encountered in this region of the lake.

 

University of Michigan School of Natural Resources and Environment Contacts: Jim S. Diana and Jim Boase Phone: (734)763-5834  Fax: (734)936-2195 E-mail: jimd@umich.edu         james_boase@fws.gov

1999

Within the St. Clair River system, a population of sturgeon exists which appears to spawn within the St. Clair River and juveniles continue to reside there for some period of time. Work in the early 1980s allowed us to collect small sturgeon throughout the year using set lines, and work during the spawning season 1996-1999 indicates that large adult sturgeon are common during the late May/early June spawning period. The nature of this stock is relatively unknown. In particular, we do not know the extent and locations of spawning habitats, the characteristics of selected spawning sites, the potential competitors and predators on eggs in these spawning sites, nor the residence or distribution of potential stocks. This lack of knowledge stimulated Michigan DNR, University of Michigan, U.S. Fish and Wildlife Service-Alpena Fishery Resources Office, and the U.S. Geological Survey-Great Lakes Science Center to initiate complimentary studies on the sturgeon population. Mark-and-recapture estimates have indicated a fairly large population of sturgeon spawn in this area, but whether these sturgeon represent fish resident in Lake St. Clair or in the wider Great Lakes system is unknown. The purpose of this telemetry study is to evaluate both spawning site selection and long-range movements of sturgeon that spawn in the St. Clair River system.

Lake sturgeon spawning appears to occur in the north channel of the St. Clair River, in the main part of the channel at a depth of about 30-50 feet. Collections by setlines are fairly useful in evaluating sturgeon numbers and collecting fish for implantation. For this study, we used fish in excess of 55 inches in length, so that they would be fully mature and also tolerate the large transmitters. For the set lining data, the size structure indicates that most of the fish collected were smaller than this minimum size and that juvenile fish were relatively common in the St. Clair River.

A total of six fish were implanted during the 1997 season with both radio and ultrasonic transmitters. Four more fish were implanted with ultrasonic transmitters in the spring of 1998. The ultrasonic transmitters have batteries that are rated to last for 15 months, because of this we expected the transmitters that were implanted in the spring of 1997 to fail sometime during the 1999 season. Six new fish were implanted with ultrasonic transmitters in the spring of 1999. These fish were implanted to replace the fish from the first year. All fish used in this study were captured between late May and early June. Details on the dates of implantation and tracking are listed in Table 1.

The transmitters that were implanted in fish in 1997 did not fail during 1999 as expected. They have continued to provide us with information well past the 15 months that they were rated, although the strength of the signal is much weaker than when they were new. This year we were able to track movements of sturgeon back to their spawning location due to the extended life of the transmitters. In early May, we first located fish 5 in the lake close to our field station; two weeks later, the fish had moved into the St. Clair River (Figure 1). The fish remained in the river until after the spawning season was over and then moved back into the lake. Fish 4 was captured in the spring of 1997 in the North Channel (Figure 2). After it was implanted and released, it moved out into the lake then remained there the rest of the year. In 1998, the fish was first located in the river and has remained there since. In the early spring of 1999, the fish was captured by a local fisherman from the end of his dock on the North Channel. The man kept the fish alive in the water and notified Michigan DNR. Two biologists visited to gather biological information and to assess the overall health of the fish. The fish appeared to be in excellent health, and the location of the incision for the transmitter was almost non-detectable. The fish was released and is still located in the river. In 1999, fish 1 was relocated. This fish was implanted in the North Channel in 1997, then it was feared there was either a mechanical failure with the transmitter or it had moved out of the range of our sampling area. Fish 1 was found in August and September this year near the Detroit River.

In 1997 and 1998, after most fish had moved out of the North Channel, our search efforts were concentrated on the northern portions of Lake St. Clair. This year we wanted to focus more attention searching for fish in some of the more remote locations of the lake to see if we could locate individual fish using other areas. As a result, we did find sturgeon in remote locations, areas that in the past two years had only been checked infrequently (Figures 3 and 4).

During the 1999 season, contact was established with all 10 fish implanted in 1997 and 1998. We have also been able to follow four of the six fish that were implanted with transmitters this spring. We experienced various problems with three of the six fish that were implanted this spring. We lost contact with fish 12 a week after it was implanted. After fish 15 was implanted, it was tracked moving up the river over the next two weeks and was found in three separate locations. Two weeks after the last contact with fish 15 we tried unsuccessfully to find it and fish 12 by searching the entire river from Lake Huron to Lake St. Clair. We searched this stretch of river on two other occasions, and also checked some smaller branches that drain across the delta area with no success. The remaining four fish were followed throughout the summer, fall and early winter (Figure 5).

As of December 1999, we had a total of 445 fixed locations of fish (Figure 6). The majority of the sturgeon continue to congregate in an area off the St. Clair River Delta in water that is from 12 to 18 feet deep. At the onset of this project, we expected to see movement or longer term residence of sturgeon in habitats that are shallower and closer to shore. Areas such as these are very conducive to the production of benthic invertebrates, especially mayflies, a principal component of their diet. During the entire three-year sampling period, no fish were detected in shallow water near shore. It is still unclear what features may attract adult lake sturgeon to this particular location. We evaluated temperature and dissolved oxygen as possible reasons why the fish may not be using other areas of the lake, because Anchor Bay and the southeastern end of the lake should represent areas with the greatest potential for stratification. We detected no significant difference in temperature or dissolved oxygen at these locations compared to the delta area.

 

Table 1. Biological and tracking information for 16 lake sturgeon captured from the St. Clair River, 1997-1999 (last tracking date 12/17/99).

 

 

Figure 1. Movement of fish 5. "S" represents 1997; "$" represents 1998; and "#" represents 1999.

 

 

 

Figure 2. Movement of fish 4; notations as in Figure 1.

 

 

Figure 3. Movement of fish 3; notations as in Figure 1.

 

 

Figure 4. Movement of fish 8; notations as in Figure 1.

 

 

Figure 5. Locations of fish implanted in spring 1999.

 

 

Figure 6. Locations for all fish through December 1999 (dark gray #) and listening locations where fish were not located (light gray).

 

2000

We expect to track eight to ten fish through the summer and fall of 2000. We feel the information obtained from this study is excellent and should provide valuable additions to the information taken from mark-and-recapture work by Michigan DNR. In fact, because few fish have been recaptured at present, only the telemetry work is giving us any indication of stock dispersal at this time.

During this summer, we plan to address some potential reasons why sturgeon congregate in certain locations in Lake St. Clair. We plan to expand sampling of vegetation and benthic invertebrates, particularly in the area off the river delta and incorporate our results with those of previous studies. We also would like to estimate the type of forage lake sturgeon are consuming. To do this, we will attempt to use some method of gastric lavage. If this does not work, we will analyze stomach contents of fish that will be sacrificed for toxicology information. The number of fish to be sacrificed for toxicology has yet to be determined.

In the long term, we envision following up this study with a study of behavior of juvenile sturgeon in the St. Clair River system. During the past three springs, the large majority of fish taken by longlines were juveniles. These fish appeared to remain in the river system after the spawning season ended, and not move out into the lake as most adults did. The differential behavior of juvenile and adult fish is interesting, and it would be useful to know whether the juvenile stock in the St. Clair River system resides entirely there, or if some of those individuals also move out to Lake St. Clair or beyond.

 

U. S. Geological Survey Great Lakes Science Center Contact: S. Jerrine Nichols Phone: (734)214-7218  Fax: (734)994-8780 E-mail: S_Jerrine_Nichols@usgs.gov

1999

The St. Clair River and Lake St. Clair ecosystem supports one of the only documented, significant population of free ranging, riverine-spawning lake sturgeon still extant in the Great Lakes. Historically, the St. Clair River contained a number of spawning sites (Goodyear et al. 1982) but only two are known to be active today: one in Port Huron, at the head of the river, and the second, in the North Channel, just before the river empties into Lake St. Clair. Relationships and connectivity, if any, between these two spawning stocks is still being determined. These two spawning grounds will be critical in the continuing recovery of lake sturgeon in this river system if they provide suitable habitat not only for spawning to occur, but also for the survival of larval sturgeon. There is no information presently available about the degree of spawning effort, or larval production from either of these sites. Further concerns were recently raised since the exotic fish, the round goby (Neogobius melanostomus), has successfully colonized the St. Clair River (Baker 1980). This bottom-dwelling fish is a voracious feeder known to eat a wide variety of prey, including fish eggs and larvae (Charlebois et al. 1997). Densities of round gobies have increased exponentially throughout the St. Clair River system and in June 1997, Great Lakes Science Center divers videotaped numerous round gobies colonizing the sturgeon-spawning reef in the North Channel. Furthermore, sturgeon eggs were found in the stomachs of several of these gobies.

In 1998 and 1999, we surveyed the spawning reef in the North Channel in order to determine if it was an important recruitment site for lake sturgeon and to assess the potential problems that may be occurring due to round goby colonization. This spawning reef in the North Channel of the St. Clair River is small (1/8ha or 7500 sq. m), ranges from 6-13 m deep, and has an average water velocity of 1-3 m/sec. The reef is not a natural substrate, but instead is composed of coal clinkers, that were deposited over 100 years ago when this area served as a dock for salt freighters. These coal clinkers are irregular in shape, ranging from 0.5-12 cm in size and form deposits up to 2 m deep. No submersed vegetation is found on the site.

Lake sturgeon spawning behavior

The spawning period is of short duration and triggered by the onset of 13�C water temperatures. Adult sturgeon gather in a holding pattern about 1.3 km upstream of the reef in the North Channel. A few smaller sturgeon (~ 1m in length) are seen in and near the reef before temperatures reach 13�C, but no spawning occurs. Once temperatures reached 13�C, on May 17^th in 1998, and May 25^th in 1999, egg deposition began. Spawning occurred over the next 3 days in 1998 ending on May 20^th and over 1.5 days in 1999, ending on May 27^th. Adult sturgeon then left the reef and returned to the staging area. Based on SCUBA diver surveys and videotape analysis, only about 30-50 adult sturgeon were involved in the spawning runs in 1998 and somewhat fewer fish in 1999. Estimates of the number of adult fish present are conservatively low due to sampling constraints. First, dive time on the reef was limited to a maximum period of 4 hours/day. The fixed video camera provided more information as it was taping continuously, but its fixed position only provided view of sturgeon immediately in front of it. The divers never saw more than 3 groups of spawning adults at any time. Some of the fish were distinctively marked and remained on the reef for much of the spawning period. One had a severely deformed tail, and another appeared black in color. In both years, females were larger than the males, up to 8 ft in length, and fewer in number. We also assumed that spawning intensity was not different during the night. All of this observational data was used to estimate the number of adult sturgeon using the reef. Sex determination was based solely on behavior during the spawning runs as adult sturgeon are not sexually dimorphic (see Figure 3). In both years, a second spawning run occurred about 41 days after the first; on June 26^th in 1998 and July 1^st in 1999 when water temperatures were between 18-19� C. The number of adults in the second spawning run in 1998 was estimated at less than 20. No estimate was obtained for the number of adults involved in the second spawning run in 1999.

One concern we initially had was that the sturgeon would react negatively to the presence of the SCUBA divers. In fact, spawning sturgeon were greatly attracted to the divers and would rub up against them, allow themselves to be scratched and in general treated the divers as another large sturgeon.

Egg deposition rates

Estimates of the number of eggs deposited on the reef varied significantly between types of gear. Estimates based on the number of eggs in the polypropylene filter mats measured average egg deposition in 1998 at 2254 eggs/m² and fewer, 1638 eggs/m² in 1999. There was a significant difference in the number of eggs deposited between years and between mats within years. In 1998, egg deposition ranged between 1450/m� and 3659/m� (mean 2254; median 1659; standard deviation 1023; degrees of freedom 9). In 1999, egg deposition ranged between 651 and 3967 / m� (mean 1638; median 921; standard deviation 1410; degrees of freedom 9). The rate of egg deposition between years was compared using a two-tailed t-test. The t-statistic was 0.6506 indicating a significant difference in deposition rates between 1998 and 1999.

In 1998, estimates of egg deposition based on the quadrat samples averaged 185/m² (range 10-500/m²; median 115; standard deviation 227.9; degrees of freedom 4). Number of eggs collected by each diver varied according to water flow and water clarity. This technique was not used in 1999.

In 1998, the plastic trays filled with rubble provided the lowest estimate of egg densities averaging 7.1/m² (range 0-30/m²; median 2.95; standard deviation 9.9; degrees of freedom 24). This sampling gear was only used in 1998 as many of the trays silted in within a few days of being placed on the reef.

Egg viability and fate of fry

Sturgeon eggs are about 4 mm in diameter and are enclosed in an adhesive coating that anchors them loosely to the substrate. Around day 3 or 4 post-spawn, this sticky coat ruptures and the developing embryo drops down into the substrate. A cursory examination of the substrate cannot detect eggs or embryos once the sticky coat ruptures. Eggs hatched between 9-11 days after spawning in both 1998 and 1999. Sac fry were first observed on May 27^th in 1998 and on June 4^th in 1999. The hatch rate of the artificially spawned eggs that were loaded into trays and planted back on the reef was low, averaging 3%. Siltation was a severe problem with all the trays. The hatch rate of the naturally spawned eggs loaded into the metal cylinder and planted on the reef had an average that was higher than that of the eggs in the trays, but lower than that of the eggs sent to the hatchery. The average hatch in the cylinders was 19% (range 5-32%) based on 5 cylinders pulled between June 16^th and June 22^nd. Cylinders pulled after that date, when the larvae would have passed the yolk sac stage and been actively feeding contained no larvae but did contain a lot of fungused material.

The modified dig sampling technique did detect eggs, newly hatched larvae, and fully formed fry (Table 1), up to 20 cm down in the rubble. Fry were detected for a period of about 2 weeks after hatch, though in declining numbers (Table 1). By the 20^th day after hatch, no sturgeon larvae of any size could be collected on the reef. On a few occasions, divers noted that fry were present in the substrate, but avoided capture in the net by evasive swimming maneuvers (swimming over the net and back into the substrate). The sac fry (newly hatched) averaged 10 mm in total length in both years. Over the next 20 days or so, the fry completed development of eyes and mouth, lost the yolk sac, and grew to an average length of 17 mm. Fewer dig samples were collected in 1999, only 8 total; five on June 7^th and 3 on June 22^nd. Unlike the 1998 data, only one dig sample, taken on June 7^th contained live fry (6 total). Three of the other four digs contained a total of 23 decaying fry. The fifth sample was empty. The modified dig sampler was the only technique that ever detected live sac fry or older larvae on the reef. The other techniques, such as fry traps, drift nets, etc., never collected larvae or fry in either 1998 or 1999.

Predation on sturgeon eggs and larvae by round gobies and native fish.

The predation on sturgeon eggs on this reef is limited to the period between the time of deposition and the time when the sticky coat ruptures and releases the embryo into the substrate, about 3-5 days. Round gobies have even less opportunity to feed on sturgeon eggs, as they leave the reef while the adult sturgeon are present. Adult sturgeon are known to prey on round gobies over other fishes (Thomas and Haas 1999). To date, no sturgeon sac fry or larvae have been found in any fish stomach.

A total of 106 round gobies (67-144 mm TL), 19 logperch (Percina caprodes, 67-114 mm TL), 2 yellow perch (Perca flavescens, 179, 247 mm TL), and 5 redhorse (Moxostoma spp.) were captured from May-July, 1998. Of the 106 gobies, 46 were female and were smaller than the males TL 85 + 11.4 mm (S.D.) for the females compared to 103.7 + 18.3mm. Every type of fish collected from May 17th – May 23, ate sturgeon eggs and redhorse eggs and fry. Table 2 shows the importance of various food items to round goby during the sampling season in 1998. Round gobies are opportunistic feeders on this reef, feeding mainly on invertebrates including zebra mussels, ephemeropterans, dipterans, crayfish, etc. Sturgeon eggs are eaten, but only for a short period of time. In 1999, we collected fewer fish: 52 gobies, 5 redhorse, 2 yellow perch, 1 walleye, and 1 common carp. Fish were collected from May 27^th, at the start of spawning, to June 1^st. Two separate sets of samples after those dates were lost underwater during diver gear failure.

Use of the reef by native and non-native fish

The reef fish community and physical structure changes during the season, as native and exotic fish spawn and feed on the site. At the start of the diving on the reef in 1998 (April 30^th), the reef had a smooth slope flowing along a gradient from 6 m down to 12 m in depth. The substrate was moderately to heavily silted with visibility between 1.5-2 m. Water flow across the reef was constant at around 1.3 m/sec and visibility was poor, usually around 2 m. In late April, few fish were seen on the reef. Round gobies were the most commonly seen fish, at densities of 2-3 gobies /m� with an occasional carp (Cyprinus carpio) noted in the deeper areas.

During the second week in May, redhorse suckers (Moxostoma spp.) arrived on the reef and began cleaning the gravel in preparation for spawning. At first, only 20-30 redhorse were present, and cleaned only a small portion of the cobble, but by the following week several hundred redhorse were digging nest depressions. By this time much of the reef had been cleaned of silt and visibility dropped to <1 m. This digging behavior changes the entire surface topography of the reef. The reef surface changed from a smooth gradient to extremely rough, with large craters, plateaus and steep drops scattered throughout. Only the 11-13 m depth range was still smooth, although now mostly free from silt. As the surface gradient changed, water currents changed. There were now areas of lower current, swirling currents, eddies and channelized regions with extremely fast currents. The round gobies were pushed off most of the reef and were concentrated upstream and along the shallow edge (6 m) of the reef at densities of about 5-6 / m� and at the downstream end. The downstream, or back of the reef had an unusual current flow, an upwelling eddy that curled back upstream onto the back of the reef. This area was heavily colonized by round gobies, at densities of approximately 120 / m�. They were feeding heavily on redhorse eggs and the benthic invertebrates that were drifting back as the redhorse dug up the reef substrate. The following week, as spawning waned, the numbers of adult redhorse dropped to an average of 75-80 fish on the entire reef.

On the 17th of May the lake sturgeon appeared and began spawning. The divers never observed more than 3-5 groups of spawning sturgeon at any one time, with a single group consisting of one large female and 2-3 attendant males. In 1998, several of the males on the reef were very distinctive in appearance. One was almost black in color and another had a malformed tail. These males remained on the reef throughout the spawning period. As the sturgeon were spawning, redhorse suckers moved down to the middle and the downstream end of the reef. However, redhorse were observed following the spawning sturgeon and feeding on sturgeon eggs, as they were deposited. After sturgeon spawning finished, the number of redhorse present on the reef dropped to 40- 50 fish.

Once the adult sturgeon left the reef round gobies returned, at densities up to 25 / m� and fed heavily on sturgeon eggs and redhorse eggs and fry. Logperch and yellow perch also appeared on the reef at this time. Logperch reached densities of 8-10 / m� from mid reef to the back of the reef in waters from 6-7 m deep. They were uncommon in waters deeper than 7m. Yellow perch schools of 15-20 fish up to 30 cm in length, were found in the same areas. Small mouth bass, 30-50 cm in length, appeared a few days later. Round goby densities dropped during this time to about 12-15/m�. By mid June, just before the second sturgeon spawning run, there were just a few each of bass, log perch, redhorse, and yellow perch on the reef and round goby densities dropped to 1-2 / m�.

In 1999, the patterns of fish use of the reef were the same as in 1998, but the timing and densities differed. In 1999, the arrival of the redhorse and arrival of the sturgeon occurred one-two weeks later than the previous year. Fish densities were drastically reduced particularly the redhorse. Only about 150 -200 redhorse were on the reef and they were concentrated and cleaned only the shallower areas (6-10 m areas). The deeper parts of the reef, 11-12 m, were minimally disturbed, and this part of the reef remained relatively flat and silty. The reef was not cleared of silt as completely as it had been in 1998.

Table 1. Number of lake sturgeon eggs and fry collected in the modified dig samples in 1998.

* seen by the divers, but escaped the net.

 

Table 2. Index of relative importance (IRI) of prey in stomachs of round gobies from the lake sturgeon spawning reef in the St. Clair River, 1998. N is percent number, V is percent volume, F is percent frequency, n is number of goby stomachs sampled.

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DETROIT RIVER

U.S. Fish and Wildlife Service Alpena Fishery Resources Office Contact: Jerry R. McClain Phone: (989)356-5102  Fax: (989)356-4651 E-mail: jerry_mcclain@fws.gov

1999

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 incidental catch of young, genetically unique, juvenile lake sturgeon indicates that recruitment has occurred in western Lake Erie (Porter et al. 1997). 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. Similarly, no studies have been initiated to determine the location or current condition of other potential spawning, nursery, and feeding micro-habitats that are consistent with those known to support self-sustaining stocks of lake sturgeon (Kempinger 1988; 1996). 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. 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 spring of 1999 to begin filling the data gaps on Detroit River lake sturgeon and their habitats. This study was undertaken to begin directing attention to the Detroit River through a cursory examination of historical lake sturgeon spawning sites to evaluate the current physical condition and determine whether lake sturgeon are currently using those or other sites in the river.

Six of the seven historical Detroit River lake sturgeon spawning sites identified by Goodyear et al. (1982) were investigated in this study (Table 1). The seventh site, near Peche Island at the head of the Detroit River, was geographically distant from the other six sites and was not logistically feasible to sample. The Sturgeon Bar site was eliminated because habitat alteration in that region of the Detroit River no longer provides depth or flow considered minimal for lake sturgeon spawning. In addition, areas adjacent to the six primary sample sites where river currents create a depositional zone were investigated concurrently for use as lake sturgeon feeding areas. Based on similar sampling efforts in the St. Clair River it appears that depositional zones are effective assessment fishing sites prior to spawning (M. Thomas, Michigan DNR, personal communication).

Table 1. Six historical lake sturgeon spawning sites in the Detroit River, Michigan (from Goodyear et al. 1982)

Setlines were fished three to four days per week from May through July 1999. Setline configuration was similar to that used by Thomas and Haas (1999) in the St. Clair River. Hooks were baited with a combination of round gobies (Neogobius melanostomus) and other fish species. Round gobies were used as extensively as allowed by availability due to an apparent feeding preference by lake sturgeon in the St. Clair River.

Data collected from all captured lake sturgeon included; total length (cm), fork length (cm), girth (cm), and weight (kg). The leading pectoral fin ray from the left side of the fish was removed for aging purposes and a 1 cm² section of the distal portion was removed and placed in a 15 ml vial containing 95% ethanol for later genetic analysis. Each lake sturgeon was externally marked with a self-piercing Monel livestock ear tag to assist in the determination of seasonal movement and distribution patterns. Abiotic data collected at each site included water depth, surface water temperature, bottom water temperature, dissolved oxygen (bottom), and latitude/longitude.

Results

A total of 54 one night sets were made at, or immediately adjacent to, 5 of the historical spawning sites listed in Table 1 between April 27 and July 15, 1999 with setlines. Two lake sturgeon were captured near Fighting Island (Table 2) but neither fish was near the coordinates referenced in Goodyear et al. (1982). Both fish were of sufficient size and age to be sexually mature but no signs of maturation were externally evident.

A total of 37 one night sets was made at depositional sites near the reference historical spawning sites, or during exploratory sampling within the Detroit River system between April 27 and July 15, 1999 with setlines. Six lake sturgeon were captured at the Ballard’s Reef site and represents the greatest aggregation of lake sturgeon encountered during this initial sampling period. The six fish ranged in size from 93 – 157 cm (T.L.) and were captured primarily in May 1999 (Table 2). No age structures were taken from the two largest fish from this location but the fish were estimated to be of sufficient size and age to have been sexually mature. However, no external indication of sexual maturity was observed. It is assumed that this site and the occurrence of these fish were related to feeding activity rather than spawning.

Table 2. Data summary for lake sturgeon captured with set-lines in the Detroit River, 1999.

Three additional lake sturgeon were captured with 8 overnight setline sets at the Fighting Island, Ballard’s Reef and Turkey Island sites in October 1999 (Table 2). The fall sampling, was completed to examine the relative abundance of lake sturgeon in the Detroit River in the fall. Other studies have indicated a fall migration of Great Lakes sturgeon into river systems for over-winter feeding and holding (R. Bruch, Wisconsin DNR, personal communication). Anecdotal reports of target fishing for lake sturgeon in this region of the Detroit River supports the hypothesis of such a movement. Reported numbers of sport caught lake sturgeon encountered in October and November indicates that aggregations of fish are common at that time of year.

Overall, a total of 11 lake sturgeon were captured with set-lines fished in the lower Detroit River, May-October 1999. All fish were tagged with Monel self-piercing livestock ear tags. Tags were affixed to the musculature at the base of the dorsal fin. As represented by the 8 fish aged, captured fish represented age classes 7-38. No external signs of sexual maturity were observed in any of the fish captured, therefore, no confirmation of spawning activity can be made at any of the historical sites cited.

2000

Staff from the Alpena FRO will work in cooperation with Central Michigan University to conduct a telemetry study on adult lake sturgeon in the Detroit River. The US EPA Great Lakes National Program Office and the Ohio Division of Wildlife are funding the study. It should allow the identification of lake sturgeon spawning locations in the Detroit River.

 

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LAKE ERIE

Ohio Division of Wildlife Sandusky Fisheries Research Station Contact: Dave Davies Phone: (419) 625-8062  Fax: 625-6272 E-mail: dave.davies@dnr.state.oh.us

1999

The program of lake sturgeon reporting was continued in the Lake Erie basin in 1999. A total of 38 fish were reported to the Ohio DOW in 1999 as compared to 45 reported in 1998 and 64 reported in 1997. Again, as was the case in 1998, lake sturgeon reports came from a variety of sources, including commercial fishers, sport fishers, shoreline residents and others (Figure 1). The distribution of lake sturgeon sightings was lake-wide with the greatest occurrences, again, in the Lakeside-Marblehead and Cedar Point areas (Figure 2).

The length frequency distribution for lake sturgeon reported in 1999 is provided in Figure 3. Although no aging structures were collected from reporting sources, it is apparent that several age classes are represented in those fish reported in 1999.

 

 

Figure 1. Numbers of Lake Erie lake sturgeon reported to Ohio DOW in 1999, by source.

 

 

 

Figure 2. Sightings of lake sturgeon in Lake Erie, 1997, as reported to Ohio DOW from all sources. Relative size of circles denotes frequency of reports from individual sites.

 

 

Figure 3. Length frequency distribution of lake sturgeon reported to Ohio DOW from all sources in Lake Erie, 1999.

 

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NIAGARA RIVER / LAKE ONTARIO

U.S. Fish and Wildlife Service Lower Great Lakes Fishery Resources Office Contact: Chris Lowie Phone: (716) 691-5456  Fax: (716) 691-6154 E-mail: chris_lowie@fws.gov

1999

Great Lakes Lake Sturgeon Genetics

A report entitled, Great Lakes Lake Sturgeon Genetics Status Assessment: An Analysis of Samples, Methods, and Standardization (Lowie 1999) was completed and distributed to agencies throughout the Great Lakes Basin. The objective of the report was to compile information on existing genetic samples and programs conducted by various natural resource agencies to determine compatibility and identify potential standardization methods. A genetics workshop, held in December 1999, complemented the report by providing a forum for biologists, managers, and geneticists to discuss the current state-of-knowledge, identify information needs, and standardize further collection and analysis of genetic samples. A brief overview from the open discussion session is provided below; however, these minutes have not been critically reviewed. The information is being provided for planning purposes only and should not be referenced. A proceedings document will be available in the near future, which will include final recommendations for future sample collection, distribution, and analysis.

Genetics Workshop Summary

Collection, fixing, and preservation methods: Samples should be collected primarily from spawning populations; however, samples from open water fish are valuable. Fin tissue is the most effective, yet least invasive, tissue type and should be provided in most circumstances. Use best professional judgement as to the quantity of tissue collected; however, more is better (up to 1 square inch from adults). Water rinse and wipe hands and utensils between samples to ensure they are not contaminated. The best fixing and preservation method was determined by geneticists to be air-drying. Drying is most easily achieved by placing the sample in a paper envelope. However, this is not best for archiving samples due to possible pest infestation. The second best method for preservation is putting the sample in 95% alcohol (not denatured alcohol), particularly if archiving the sample. It is best to change the alcohol after the initial fixation for long term storage. Completely submerge sample in at least two times as much alcohol as sample. If samples are frozen, keep them frozen until analysis is conducted.

Centralized depository for samples:  It was discussed whether a depository should be established for samples or data. It was determined a database would be acceptable, which would be available to Great Lakes agencies. The database will be held within the USFWS Great Lakes Basin Ecosystem Team, Lake Sturgeon Committee’s standardized database (to be held at the Alpena, MI FRO). This database will include information on standard biological data, tagging data, collector, location, etc.

Analysis methods:  Microsatellite analysis is fastest for stock identification; however, experimentation with other methods will be left open for the future. A library of microsatellite markers is being established between some cooperative labs. More microsatellite markers might be needed; however, all existing markers should be examined more thoroughly to evaluate their usefulness. Existing and additional markers should be standardized and available to allow multiple labs to compare data. Contracts between agencies and genetic labs should be specific as to the use of samples and data.

The LGLFRO continues to lead the effort to obtain funding for genetics analysis. Proposals have been submitted to three sources, requesting funding over four years to collect additional samples from spawning populations, develop new markers, standardize the markers, perform stock structure analysis, and prepare a basin-wide management plan. To facilitate this study, it is recommended to continue collecting genetics samples and to hold them for later analysis. However, if there is an immediate need to have them analyzed, a contractual agreement should first be established.

PROJECTS

Lower Niagara River

Since the summer of 1998, we have been studying the population of lake sturgeon in the lower Niagara River. This lake sturgeon project is in cooperation with the State University of New York - College at Brockport. The data provided here is considered preliminary results, with complete analysis of the data being provided via a thesis publication (Hughes et al. manuscript in progress).

The overall goal of our study is to identify key spawning and feeding habitats in the river in order to better manage, protect, and enhance the lake sturgeon population. The research objectives of our study are to: (1) compare the daily, seasonal, and diel movement patterns of juvenile and adult lake sturgeon, (2) compare the utilization of macro- (e.g., river, main lake) and micro- (e.g., high flow, back eddy) habitats between juvenile and adult lake sturgeon, (3) determine the age and growth of adult and juvenile lake sturgeon, and (4) determine the genetic discreteness of Niagara River lake sturgeon.

To date, we have collected 32 lake sturgeon by SCUBA diving, gill nets and baited setlines. In 1999, we captured a total of 26 sturgeon with a CPUE of 0.27 fish per night for all methods (Table 1). We began our 1999 gillnetting efforts in late April by targeting adult fish (> 1200 mm) with 10" stretch mesh gillnets. We successfully captured five suspected adult fish (two known ripe males) before increased algal and macrophyte drift decreased our sampling efficiency. We continued to sample through the summer; however, no additional adult sturgeon were captured. During the months of September and October, we had tremendous success using setlines baited with Chinook salmon egg skein, with a CPUE of 0.58 fish per night. We believe the sturgeon were keying in on the salmon eggs as large numbers of salmon were migrating up the river for their annual fall spawning run. Additionally in 1999, a considerable number of anglers reported catching lake sturgeon while salmon fishing.

Not knowing the age at maturity of the Niagara River population, we feel we have been catching primarily juvenile (<1000 mm TL) and sub-adult (1000-1200 mm TL) fish, with at least five fish, based on length, likely to be adults (>1200 mm TL) (Table 2). Two fish were known to be ripe adults since milt was observed during processing. We were unsuccessful, via internal examination through incision, in determining the sex and maturity of the other adult-sized fish.

Table 1. Comparison of lake sturgeon catch among different gear types in lower Niagara River, 1999.

 

Pectoral fin rays were collected and analyzed to interpret the ages of all lake sturgeon captured. Ages of lake sturgeon captured ranged from 1 to 20 years old, with a majority (n =19) of fish between 4 to 6 years old (Figure 1, Table 2). Suspected adult fish were determined to be between the ages of 12 and 20 years old. Both of the ripe males were 12-year-old fish. In addition, two fish categorized as sub-adults (based on total length) were determined to be 12 years old and could potentially be adult fish (Table 2). The growth of these fish appear to be higher than populations from the Lake Huron Basin (Hill and McClain 1999). Specifically, lake sturgeon from the Niagara River tend to be longer and heavier than lake sturgeon of the same age from Lake Huron waters (Hill and McClain 1999). Age-length relationship is shown in Figure 2.

 

Figure 1. Age distribution of lake sturgeon caught in the lower Niagara River, 1998-99.

 

Table 2. Biological data for lake sturgeon captured in lower Niagara River, 1998-99.

*Maturity classification based on age and total length of fish.

 

Our sampling methods proved to be effective in catching lake sturgeon greater than 700 mm, with a mean total length of fish captured in 1999 of 996 mm (Table 1). We only captured two fish less than 700 mm (Figure 3). This reflects more the selectivity of our sampling gear and methodology rather than smaller size classes being absent from the population. Our gill nets (with few panels of 4-inch stretch mesh or less) and setlines targeted primarily larger fish. Divers indicate they have seen a fairly even distribution of size classes in the river.

 

 

Figure 2. Relationship of age vs. length of lake sturgeon caught in the lower Niagara River, 1998-99.

 

Figure 3. Length distribution of lake sturgeon caught in the lower Niagara River, 1998-99.

 

Ultrasonic Biotelemetry

Since August 1998, 19 fish have been fitted with ultrasonic transmitters to monitor their long-term movements in the lower Niagara River and its confluence with Lake Ontario (Table 3). Tags were attached externally to either the dorsal fin, when suitable tissue was available, or through the dorsal scutes. Several sonic tags have become ‘idle’ (e.g., lost tag) as indicated by prolonged stationary fixes, while other tags/fish have not been located since shortly after tagging (i.e. absent) (Table 3). Tag retention (track duration) averaged only 60 days among those tags that are currently ‘idle.’ Two adult fish (#293 and #257) have not been located since mid-June, the end of the suspected spawning period. Currently, we are actively tracking six fish, with five fish absent, and eight ‘idle’ tags (Table 3).

Table 3. Tagging data for ultrasonic tagged lake sturgeon captured in lower Niagara River, 1998-99. Tracking status as of 12/22/99.

* #356 captured in 1998 contains fixes (4/12/99 and 4/26/99) prior to being recaptured and re-tagged in 1999.

 

In general, our tagged lake sturgeon inhabit both the Niagara River and Lake Ontario at its confluence with the river (Figure 4, Table 4). Fish in the lake (within our tracking ‘circuit’) are very seldom found outside the confluence of the river (Figure 4, Table 4). Juvenile lake sturgeon seemed to prefer nearshore, slow water currents (mean bottom velocity 0.19 m/s), primarily remaining where they were collected, in Peggy’s Eddy and the Queenston Long Drift (Figure 4, Tables 4 & 5). Adults seemed to prefer the faster currents (mean bottom velocity 0.37 m/s) of the river and its confluence with the lake (Figure 4, Tables 4 & 5). Juveniles (mean depth 10.4 m), sub-adults (mean depth 9.3 m), and adults (mean depth 10.6 m) occupied similar depths (Table 6). Overall, lake sturgeon occupied depths ranging from 2.3 to 25.3 m with a mean depth of 10.3 m (Figure 5, Table 6).

 

Table 4. Macro-habitat (river vs. lake) and within-habitat current preferences of different life stages of lake sturgeon in lower Niagara River, 1998-99.

 

Table 5. Average velocities of tagged lake sturgeon in lower Niagara River and its confluence with Lake Ontario, 1999.

Adult lake sturgeon generally occupied two areas in the river during preferred spawning temperatures (13 to 18 ^oC literature range; May - June); the mouth of the river at Fort Niagara and the ‘red cliffs’ region from Stella Niagara upstream to Lewiston (Figures 4 & 6). On 5 June 1999 (water temperature 16 ^oC), three of five adult fish were located in close proximity to one another in the ‘red cliffs’ region (Figure 6, rkm 9). We have identified these areas as potential spawning sites in the lower river.

 

 

Figure 4. Location of lake sturgeon in Lake Ontario and the lower Niagara River, 1999.

Table 6. Depth preferences among different life stages of ultrasonic tagged lake sturgeon, 1998-99.

 

Figure 5. Depth distribution of lake sturgeon caught in the lower Niagara River, 1998-99.

 

 

Figure 6. Seasonal movement of five adult lake sturgeon in the lower Niagara River and Lake Ontario. River kilometer zero represents the mouth of the river. Positive river kilometers represent river locations and negative numbers represent lake locations. Disconnected lines indicate when a fish was ‘absent’ from the tracking area or when the interval between tracking events was greater than 14 days (e.g. we did not rack between 8 November and 22 December).

 

The substrate composition in ‘high use’ areas was surveyed using a Ponar dredge. In the eddy environments substrate was made up of silt, sand, and gravel. As flow increased, on the outside of eddies and in the main current, successive dredges collected very little substrate particles. In these areas, the substrate was characterized as hard bottom. The benthic fauna in the eddies consisted primarily of Oligochaetes, Chironomids, Mollusks (Dresseina sp., snails, fingernail clams), and Amphipods. No diet studies have been performed.

Twenty-four hour tracking events occurred on August 31, September 2, and September 3, 1998 to investigate the diel movement of tagged lake sturgeon. Prior to our study, we hypothesized that (1) lake sturgeon may be utilizing deeper waters (> 15 m) during the day then moving into shallow waters (< 10 m) to feed at night; and, (2) some fish may occupy the lake during the day and move into the river at night, particularly at or near its mouth. These suspicions were not confirmed by our sample of ultrasonic tagged fish. In general, fish did not exhibit large-scale movement patterns between day and nighttime hours. However, fish did appear to be more active at night, as indicated by increased localized movements. Unfortunately, we were unable to conduct more 24-hour tracking with greater sample sizes of fish, so we cannot draw any significant conclusions from the diel movement data.

Genesee River

In a cooperative effort with New York State Department of Environmental Conservation (NYSDEC) Region 8, Avon and Endangered Species, and U.S. Geological Survey, Tunison Laboratory of Aquatic Science, we are determining the habitat suitability for, and the present utilization of lake sturgeon in the Genesee River below Rochester. Our office deployed 10-inch stretch gillnets in the river to catch adult lake sturgeon potentially migrating during the suspected spawning period. In addition, during the summer months (July and August), experimental gillnets were fished to capture young lake sturgeon. No lake sturgeon were caught after 27 gillnet nights of effort (Table 7). According to the HSI for lake sturgeon (Threader et. al. 1998), suitable spawning habitat (0.5-2.5 m depth, 50-240 cm/s velocity, 10-18^o C, and boulder/cobble substrate) was found below the lower falls. Sub-optimum juvenile habitat was found in the downstream areas of the river. The Rochester Embayment is listed as an Area of Concern, therefore the effects of chemical contamination on the suitability for lake sturgeon cannot be ignored. However, no water chemical analysis was done in 1999.

 

Table 7. Lake sturgeon sampling effort in lower Genesee River, 1999.

Oswegatchie River

The Oswegatchie River lake sturgeon project is in cooperation with the New York State Department of Environmental Conservation (NYSDEC) and the State University of New York - College of Environmental Science and Forestry. To determine the success of the restoration effort several objectives were set forth. These included determining the distribution, movement, and habitat utilization of stocked juvenile lake sturgeon in the Oswegatchie River, tributary to the St. Lawrence River at Ogdensburg, NY (Lowie et al. 1999).

Sampling continued to determine downstream distribution of stocked juvenile lake sturgeon at selected sites. Gillnetting was conducted on 15 nights consisting of 50 individual gillnet sets (4 sampling periods, May - Oct.). This yielded 264 lake sturgeon comprised of 5 year classes (24 specimens age not determined). A total of 23 lake sturgeon were captured from the 1999 stocking year class, 45 from the 1998 stocking year class, 127 from the 1997 year class, 44 from the 1996 year class, and 1 lake sturgeon from the 1995 stocking year class. The 23 lake sturgeon from the 1999 stocking year class were captured during the October sampling period and were released from the hatchery less than one month prior. Table 8 shows mean total length for each stocked year class collected in 1998 and 1999.

Movements of 1998 radio tagged lake sturgeon were monitored in 1999, and fish continue to show a pattern of downstream movement. The tagged naturalized lake sturgeon eventually displayed the same pattern as the newly stocked hatchery sturgeon but moved downstream at a much slower rate. As shown in the 1998 data (Lowie et al. 1999), newly stocked lake sturgeon remain in the upper reaches of the sampled area. As lake sturgeon remain in the system, they tend to move to the middle and then downstream reaches of the river. Compared to 1998, a shift in dominant year class composition was obsserved at the four standardized sampling sites. This supports the telemetry data showing the same overall downstream movement of stocked juvenile lake sturgeon.

 

Table 8. Mean total length of stocked lake sturgeon caught in the Oswegatchie River, 1998 and 1999.