Karin Hendrickson- 2 -April 9, 2015
Department of Fish and Game
DIVISION OF SPORT FISH
Soldotna
43961 Kalifornsky Beach Rd, Suite B
Soldotna, AK 99669-8276
Main: 907.262.9368
Fax: 907.262.4709
Karin Hendrickson- 2 -April 9, 2015
To: Karin Hendrickson
Pesticides Program Manager
Alaska Department of Environmental Conservation
1700 E. Bogard Rd., Bldg B, Suite 103
Wasilla, AK 99654
Re: Summary of Treatment Results for permit #14-AQU-01
Hello,
Below is a Summary of Treatment Results for a pesticide application conducted in the western branch of the Soldotna Creek drainage under permit #14-AQU-01. The treatment area included Union Lake, West Mackey Lake, East Mackey Lake, Derks Lake, some adjacent inundated wetlands and approximately 1.6 miles of interlake creek. The treatment area is located a few miles northeast of the city of Soldotna and was treated with rotenone by the Alaska Department of Fish and Game in the fall of 2014 to eradicate the illegally introduced northern pike population.
Summary of Treatment Results
Product names: CFT Legumine™ and Prentox® Prenfish™ Rotenone Fish Toxicant Powder
EPA registration #: 75338-2 and 655-691
Target pest: Northern Pike
Application dates: October 6 through 11, 2014
Application time: The application began October 6, 2014at 1:00 pmat Union Lake and concluded on October 11, 2014 at 2:00 p.m.at Derks Lake.
Method of application: The pesticides were applied using four outboard boats, one airboat, up to five backpack sprayers, an ATV sprayer and by placing rotenone/sand/gelatin mixture balls to seeps and springs by hand. No drip stations were used to apply rotenone to the streams, instead, conditions allowed us to use backpack and ATV spraying to treat streams.
Weather conditions during application:The treatment began at Union Lake and associated wetlands/creeks on October 6th, 2014, and the mid-day air temperature was in the mid 40’s Fahrenheit, the wind was negligible and skies were mostly clear. On September 7th, we began treatment of West Mackey Lake and associated wetlands and creeks; morning air temperature was in the teens and north windsbuilt throughout the day (estimated gusts at 10-25 mph) with overcast skies and mid-day temperatures reached the low 40’s. On October 8th we treated East Mackey Lake and associated wetlands and creeks; morning air temperatures were in the teens and winds built throughout the day with gusts at 10-20 mph and mid-day temperatures reached the low 40’s. On October 9th we treated Derks Lake;morning temperatures were just below freezing, skies were overcast and winds were moderate (~10 mph), mid-day temperatures reached the high 30’s with light drizzle turning to heavy rainfall by nightfall and continuing through the morning of October 9th totaling about 1.5 inches of precipitation. Temperatures on October 10th began in the 20’s and reached the 40’s mid-day with moderate winds and overcast skies. We did not conduct any treatments of October 10th. On October 11th, skies were partly cloudy, winds were light and morning temperatures were near freezing and by mid-day were near 40 F. We treated about two acres of wetlands near Derks Lake on October 11th which concluded the treatment.
Total amount of pesticide used: 460 gallons of CFT Legumine™ and 5,070.6 pounds of Prentox® Prenfish™ Rotenone Fish Toxicant Powder. The amount of pesticide used was less than anticipated because the wetland areas adjacent to most of the lakes were less inundated than expected, stream discharges (~2cfs) were relatively low and Derks Lake was lowered (~2.5 feet) when a beaver dam was breached near the lake outlet.
Location and size of treatment area: The entire treatment area consisted of: 1) four lakes totaling (405 surface acres), 2) ~20 surface acres of wetlands/floating lake-edge bog and 3) 1.66 miles of small streams (~2.0 cfs).
Names of applicators:
1)Robert Massengill (certified pesticide applicator #9718-1706-6)
2)Kristine Dunker (certified pesticide applicator #9595-1509-6)
3)Jerry Strait (certified pesticide applicator #9773-1606-6)
4)Tim McKinley
5)Tony Eskelin
6)Adam Reimer
7)Jeff Pershbacher
8)Cody Jacobson
9)Chuck Pratt
10)Amanda Alaniz
11)Adam Craig
12)Branden Bornemann
13)Matt Smukall
14)Emily Healy
15)Jason Everett
16)David Rutz
17)Jessica Johnson
18)Branden Key
19)John Bailey
20)Meg Inokuma
21)Glen Hollowell
22)Cecil Rich
Pesticide purchase, storage and disposal information: All pesticide was purchased from Central Life Sciences, 1501 East Woodfield Road #200, Schambert, IL 60173. After the treatment all empty product containers were tripled-rinsed with site water and disposed of at the Soldotna Landfill. Leftover pesticide (~ 75 gallons of CFT Legumine™ and 220 lbs. of Prentox Fish Toxicant Powder) is stored in an enclosed and locked building at the ADFG Crooked Creek Maintenance Facility, 21880 Johnson Lake Road, Kasilof, AK 99610.
Assessment of success of treatment: The pesticide treatment is believed to have removed all the invasive northern pike from the western branch of the Soldotna Creek drainage. This determination was made based upon the following indicators:
1)All caged sentinel fish (juvenile coho salmon) placed throughout the lake during the treatment died before the treatment was completed,
2)Post-treatment lab analysis of treatment water indicated the treatment achieved a pesticide target concentration of ~25ppb rotenone and that the pesticide was evenly distributed throughout the treatment area. (Note, our target rotenone concentration was 50ppb but we only attained 25ppb, which we assume was due to the rotenone binding with phytoplankton in the water column, however, 25 ppb rotenone is very lethal to northern pike.
3)No live fish were observed in any of the treated waters during post-treatment visual inspections
In the spring of 2015, ADFG will be conducting gillnet surveys and pike environmental DNA sampling to help assess whether all the pike were eradicated as is currently believed. ADFG intends to restock the treatment area in 2015 with native fish species once we confirm northern pike are no longer present. Temporary stream fish barriers now in place will prevent the reentry of northern pike into the treatment area.
Observed effects on human health, safety or welfare, animals or environment: It is believed that all fish found in the treatment area (Area 1) were eradicated during the pesticide treatment. We conducted pretreatment invertebrate surveys to document species presence and plan to conduct posttreatment surveys this summer (2015) to evaluate potential treatment related effects. Posttreatment, many species of macroinvertebrates were opportunistically observed in the treatment area; however, we anticipate zooplankton abundance will be temporarily reduced for a 1-3 year period posttreatment. Sentinel fish placed in Soldotna Creek immediately downstream of the confluence of the Derks Lake outlet creek began to showsigns of rotenone stress (lethargy, imbalance, gasping) starting on October 15, 2014 when discharge from Derks Lake (> 2 cfs) began to increase from recent rainfall. Although Soldotna Creek is part of the overall treatment area, we did not wish to impact native fish in Soldotna Creek until a planned rotenone treatment is conducted there in 2016 (Area 2 treatment). Based on sentinel fish responses in Soldotna Creek, we chemically deactivated rotenone in the Derks Lake outlet stream for one month using potassium permanganate (KMNO4). Chemical deactivation began on October 15, 2014 and continued virtually non-stop until November 12, 2014. Depending on the Derks Lake outlet stream discharge which we monitored daily, we applied KMNO4 at a rate of 18.0 – 6.0 grams/minute during this month-long period. After this deactivation period, caged sentinel fish in Soldotna Creek no longer exhibited rotenone stress symptoms despite no chemical deactivation occurring. As a precaution, we maintained caged sentinel fish in Soldotna Creek until January 28, 2015 and no signs of rotenone stress to these fish were ever detected. At no time did we observe any wild fish kills in Soldotna Creek which we monitored visually on a daily basis until it completely froze over in December.
Posttreatment we have periodically collected water samples throughout the treatment area including samples from several lakeside private wells. To date, no rotenone has been detected in any well water samples as expected. Our last lake water results collected February 2, 2015 indicate rotenone was still present in the lakes at concentrations varying from 22 to 9.5 ppb but rotenone was undetectable in Soldotna Creek. We collected new lake and well water samples on April 8, 2015 and expect results within 10 days.
For any questions, please contact Rob Massengill at (907) 260-2928.
Sincerely, Rob Massengill
ADF&G Sport Fish Division
Fisheries Biologist
43961 K-Beach Rd., Suite B
Soldotna, AK 99669