Sterile Male Release Technique

Task Force Report

Implementation of the sterile male release technique continued in Lake Superior and the St. Marys River in 1995. Male sea lampreys were captured in six tributaries of Lakes Michigan and Huron and transported to the sterilization facility at the Lake Huron Biological Station. At the facility, lampreys were sterilized with the chemosterilant bisazir, decontaminated, and released into 27 major lamprey-producing tributaries of Lake Superior (U.S.-19, Canada-8) and the St. Marys River. In addition, the interaction of sterilized males with resident lampreys was monitored in three tributaries of Lake Superior and the St. Marys River.

The sterilization facility continued to meet the needs of the Sea Lamprey Control Program. A total of 25,236 spawning-phase male lampreys were transported to the sterilization facility during May 4 - July 25. Male lampreys were sorted from the assessment traps on the Manistique River of Lake Michigan (5,939) and the following rivers tributary to Lake Huron: Cheboygan (11,699), Ocqueoc (1,655), Echo and Thessalon (1,711 combined) and St. Marys (4,224). The lampreys were injected with bisazir at a dose of 100 mg/kg of body weight. After 48 hours of decontamination, lampreys were transported to streams for release. Sterilized males placed in streams where traps were being operated were marked with a dorsal fin clip to distinguish them from resident lampreys. (Sterilized lampreys captured in traps were released alive.) A total of 24,435 lampreys were sterilized and 23,379 were released into streams. Another 116 sterilized male lampreys were used in other studies. The death of 939 (4%) sterilized lampreys occurred prior to release from unknown causes that probably were stress related.

Performance of the auto-injector was evaluated for accurate administration of a bisazir dosage to the lampreys. In 1994, an inadequate amount of bisazir was administered 2% of the time. Following a modification of the injector software, surrogate lampreys were placed into the injector to receive a dose of saline (used in place of bisazir). After injection, each surrogate was removed and weighed to determine the amount of saline injected. The test was repeated at appropriate intervals throughout the operation in 1995 and showed the error had been eliminated.

Water from Lake Huron continually was pumped through the facility to provide fresh water for lampreys and laboratory processes. Waste water from areas where bisazir potentially could occur was collected in a sump and pumped through carbon filters before release to Lake Huron.

Facility water was monitored for presence of bisazir to comply with Michigan Department of Natural Resources (Michigan Department) permit requirements, to insure safe working conditions for personnel, and to confirm that lampreys no longer excreted bisazir prior to release. We used two protocols to monitor for bisazir. First, the effluent was monitored daily. Each day 4 samples were drawn from filtered effluent and combined into 1 sample bottle. Second, water randomly was sampled from 7 holding tanks each week immediately prior to the removal of lampreys from the facility (sterilized lampreys are held in the facility for > 48 hours after injection to metabolize or excrete all bisazir from their bodies prior to release).

Analyses showed the facility was operated within the permit requirements, but trace amounts of bisazir (less than the method detection limit of 25 ęg/L) were detected intermittently in effluent samples throughout the 1995 injection season. The first trace was detected during routine analysis of an effluent sample collected on May 23. The sample was analyzed on May 30. Sterilization of lampreys was suspended on June 1 and the Michigan Department immediately was notified. A thorough review of facility protocol and rigorous testing of the carbon filters showed integrity of the process. The trace apparently resulted from an undetermined origin. Michigan Department personnel advised that the facility was not in violation of the effluent permit. Sterilization resumed on June 2. Traces again were detected in effluent samples taken during June 2-6, and sterilization operations again were suspended on June 6. Tests again were performed on the filters on June 10 and modifications were made to the filters on June 16. The plumbing to each carbon filter was modified to keep the filter media continuously immersed in water and prevent channelization of the bed. In addition, 200 liters of new carbon were added in each filter. The facility resumed operations on June 17 and traces further were detected 12 times during June 17 - July 22. Operations continued for 1995 on July 25. Modifications to the operation will correct this situation prior to start of sterilization in 1996.

A total of 25,000 sterile male sea lampreys were predicted to be available for release in 27 Lake Superior streams, based on average spawning runs of the past 5 years. The number of sterilized males released into the lake was 19,141 (Table 24). The ratio of sterile:resident male lampreys was predicted at 2.3:1 for 27 streams and the estimated ratio was 1.5:1. The first release of sterilized males was predicted for May 15 and occurred on May 19. The final release in Lake Superior was predicted for June 13 and the final release occurred on June 20. A regression was developed that predicts the trap catch of spawners from the number of parasitic sea lampreys collected from commercial fisheries during the previous year. This relation will improve our ability to plan for the distribution of sterilized males.

The predicted number of sterilized males for release into the St. Marys River was 4,800 and 4,238 were released. The first release of sterile males was predicted to be on June 15 and occurred on June 21. The final release was predicted for July 20 and occurred on July 28.

The estimated resident population of spawning-phase sea lampreys in the St. Marys River was 19,608 (10,784 males). Assessment traps removed 9,210 lampreys (5,065 male lampreys; a theoretical reduction of 47% from trapping). An estimated 5,719 resident males remained in the river and the release of 4,238 sterilized males achieved a sterile:nonsterile resident male ratio of 0.7:1 (further theoretical reduction of 23%). The combination of removal by traps and release of sterile males resulted in a theoretical reduction of reproductive potential of 70%. The effect of the sterile male release technique to the lamprey population that was not captured in traps was a theoretical reduction of 43%.

A short-term assessment of the sterile male release technique was conducted following the study plan approved for 1994 but modified for slightly different objectives and fewer study streams. The short-term assessments went well in 1995 with results supportive of previous conclusions. A formal report will be filed in 1996. The following are preliminary results and are not to be cited for other purposes.

Studies were conducted in two classes of streams, barrier streams where known populations were created above the barrier (Rock and Misery rivers) and streams without barriers where we had to rely on mark recapture estimates of the resident (untreated) population (Wolf and St. Marys rivers).

Table 24. The estimated number of resident male sea lampreys and the number of sterile male lampreys released into 27 tributaries of Lake Superior in 1995 (listed by country and ordered by location, west to east), and the theoretical reduction in sea lamprey progeny. The predicted ratio of sterile to resident males in 1995 was 2.3:1. Sterile males were released from May 19 to June 20.

Estimated Released Theoretical Resident Sterilized Estimated Reduction Males (1) Males Ratio (Percent) (2)


  Black			451			1,119			2.5:1				71
Amnicon			660			1,827			2.8:1				73
Middle			134			381			2.8:1				74
Bad			1,152			2,151			1.9:1				65
Cranberry		17			46			2.7:1				73
Ontonagon		2,847			3,195			1.1:1				53
Firesteel		183			510			2.8:1				74
East Sleeping		72			117			1.6:1				62
Misery3			96			1,024			4.9:1				83
Traverse	  	46			54			1.2:1				54
Sturgeon		1,355			924			0.7:1				41
Huron			237			166			0.7:1				41
Salmon Trout		125			85			0.7:1				40
Chocolay		230			157			0.7:1				41
Rock (3)		89			1005			2.5:1				71
Au Train		239			163			0.7:1				41
Sucker			167			114			0.7:1				41
Two Hearted		484			330			0.7:1				41
Waiska			121			82			0.7:1				40


MacKenzie		27			32			1.2:1				 54
Wolf			12			1,195			99.6:1				99
Nipigon			1,350			1,598			1.2:1				54
Gravel			108			128			1.2:1				54
Pic			405			479			1.2:1				54
Batchawana		540			903			1.7:1				63
Chippewa		270			452			1.7:1				63
Goulais			540			904			1.7:1				63

Total 			12,357			19,141			1.5:1				61

1Populations were estimated for streams using a simple linear regression of mean stream discharge to the number of lampreys estimated to enter a subset of streams (estimated by stratified multiple mark/recapture technique.  The number of males was calculated by averaging the percent males captured in assessment traps during 1990-94 (54%).  Lampreys captured in traps and destroyed were subtracted from the estimate.
2Theoretical Reduction includes reduction from trapping in the following streams:  Amnicon River (<1%), Middle River (1%), Bad River (1%), Firesteel River (<1%), Huron River (<1%), Wolf River (5%). 3Emigration of sterilized males from the Misery River was estimated where 67 left the stream and 957 remained, and emigration of sterilized males from the Rock River was estimated where 43 left the stream and 962 remained. The estimated ratios and theoretical reductions were calculated from the number of sterile males remaining in each river. 

We observed male lampreys on nests in all four streams (Table 25). The observed and expected ratios of known sea lamprey populations in the Misery and Rock rivers were significantly different. The number of observed sterile males was higher than expected in the Misery River and lower than expected in the Rock River. Resident populations were successfully estimated in the St. Marys River but not in the Wolf River. The estimate of resident males in the St. Marys River was based on over 200 recoveries and the expected and observed ratios were the same as 1993 and 1994. The Wolf River apparently had few resident lampreys in the spawning run and the estimate of resident males was based on only two recoveries. Because of the extreme ratio of sterile:resident males, the expected value for the number of resident males to be observed was less than one and comparison with Chi-square would not be valid. We do not plan on including data from the Wolf River in subsequent analyses.

Table 25. Observations of sterile and resident lampreys in study streams.

					Misery              Rock             Wolf	St. Marys

Sterile males released                      957              962           1,195          4,238
Number of resident males                    196              389              12          5,719

Sterile males on nests                      256               41              74             27
Resident males on nests                      22               34               5             36

Expected sterile:resident ratio           4.9:1            2.5:1          99.6:1         0.74:1
Observed sterile:resident ratio          11.6:1            1.2:1          14.8:1         0.75.1
Chi-square                                 16.3             10.0            22.8           0.13
      					 xx        	    xx   		 - 		NS

Our results continue to support the conclusion that sterilized males generally appear on the nests in proportion to their relative abundance in the population of males. Only 2 of the 8 pairs of observed and expected values (pointers in Fig. 10) were significantly different (P <0.5) with 1 observed value greater than expected and 1 less. Egg samples have been processed and the results have not been analyzed. The results of this segment of the work will be included in the completion report.

A study conducted by the Lake Huron Biological Station to determine the minimum effective dose (mg/kg) of bisazir for male sea lampreys suggested we could reduce the dose of bisazir. In the current automated operation, male lampreys are injected with 100 mg of bisazir per kg of body weight. However, earlier studies suggested that a dose less than 100 mg/kg may produce 100% sterility. The objective of the current study was to determine if concentrations less than 100 mg/kg would produce 100% sterility in male sea lampreys. The study plan was similar to a study performed in 1994, except the concentration of chemosterilant was varied (range of 6 doses) while the volume of liquid (bisazir in saline) injected into the lampreys remained constant. Controls were injected with 0.9% sodium chloride. Male and female sea lampreys were placed in recirculating tanks and allowed to spawn. Pairs that were observed in the spawning act were removed from the recirculating tanks and used in the study. Eggs were stripped from the female and fertilized with milt and embryological development was monitored for 18 days. Bisazir caused death of eggs in a dose-dependant manner. Eggs in 75 and 100 mg/kg dose groups died before neural development began and prolarvae in dose groups below 75 mg/kg survived up to 18 days, but many had abnormalities incompatible with life. Results of Probit analysis suggest that about 50 mg/kg could produce 100% sterility in male sea lampreys. This is half of the current dose but further tests are needed to ensure 100% effectiveness of the dose.

Fig. 10. Expected versus observed ratios of sterile:resident males.

Several contracts were awarded to determine bisazir toxicity, residues, breakdown products, and bioaccumulation. These studies are needed to comply with a request by the Michigan Department for information needed to set tolerance limits for effluent permit at the Lake Huron Biological Station. Completion reports are being prepared by the contracted laboratories for studies on toxicity of bisazir to rainbow and Daphnia and on the octanol-water partitioning coefficient. A completion report has been received for the albino rat oral toxicity study of bisazir (the study showed bisazir oral LD50 for albino rats is 25 mg/Kg).

A project titled Radio-telemetry investigations of the upstream migratory behavior of sea lampreys, including sterilized males with principal investigator Dr. John R. M. Kelso (Department) began in 1995. This study will last three years and has operated closely with the Task Force. The objectives are to determine the: 1) upstream rate of movement, the habitat (or refugia) selected, and the migratory pathways within streams of adult sea lampreys over the course of the spring spawning migration; 2) rates of emigration from spawning streams of adult sea lampreys entering the stream from early April through May; 3) upstream migrating behavior of male sea lampreys in 2 Lake Superior study streams for comparison with male sea lampreys captured in Lake Huron tributaries, sterilized, transported to, and released in those streams, i.e. the standard operating procedures of the sterile male release technique; 4) upstream migrating behavior of male sea lampreys captured, sterilized, and returned to their selected spawning stream; 5) behavior of sterile and male sea lampreys at spawning areas; and 6) response of migrating sea lampreys to instream traps and barriers.

A total of 63 lampreys received transmitters in 3 streams (Pancake River - 23, Wolf River - 20, and Bad River - 20) in 1995. The results of this first year of study will be presented to the Commission in a separate report.

The Task Force continues to monitor the progress of the technique and adjust implementation and assessment operations. Actions for 1996 include:



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