title
Trapping, spawning and trend surveys of Bonneville cutthroat trout at Manning Meadow Reservoir, 2003 : a sport fish and native cutthroat trout restoration project
author
Array ( [0] => Hepworth, Dale K. [1] => Ottenbacher, Michael J. [2] => Chamberlain, Charles B. [3] => Whelan, James E. )
abstract
date
2003-01-01
organization
Utah. Division of Wildlife Resources
species
Array ( [0] => Not Specified )
file_path
https://grey-lit.s3.wasabisys.com/trapping-spawning-and-trend-surveys-of-bonneville-cutthroat-trout-at-manning-meadow-reservoir-2003-a.pdf
thumb
https://grey-lit.s3.wasabisys.com/trapping-spawning-and-trend-surveys-of-bonneville-cutthroat-trout-at-manning-meadow-reservoir-2003-a-pdf-1-791x1024.jpg
content
TRAPPING, SPAWNING, AND TREND SURVEYS OF BONNEVILLE CUTTHROAT TROUT CONDUCTED AT MANNING MEADOW RESERVOIR, 2003 A Sport Fish and Native Cutthroat Trout Restoration Project Dale K. Hepworth UDWR Regional Aquatic Program Manager Michael J. Ottenbacher UDWR Regional Aquatic Biologist Charles B. Chamberlain UDWR Regional Project Biologist James E. Whelan U.S. Forest Service / UDWR Aquatic Biologist Utah Department of Natural Resources Division of Wildlife Resources (UDWR) 1596 West North Temple Salt Lake City, Utah 84116 An equal opportunity employer Kevin Conway Director August 2003 Introduction This report covers activities for the year 2003, the 12th consecutive year Bonneville cutthroat trout were trapped and spawned at Manning Meadow Reservoir. Bonneville cutthroat trout were introduced into the reservoir with transplants from Pine Creek in 1990 and 1991. Eggs were collected from spawning trout for the first time in 1992. Trout were trapped at either the reservoir inflow or at the spillway. Eggs were taken manually from wild trout and incubated, hatched, and reared at state facilities. Results were compared among years for spawning, trapping, and trend-netting activities. Methods The inflow trap was set on 13 June and operated until 25 June, 2003, about mid-range among trap operation times for all years. The reservoir spilled for several weeks during early June and some additional fish were trapped at the outlet. Spawning trout were trapped at the inlet and outlet where the were attracted to moving water and readily entered compartmentalized pens where the could be collected, sorted, and held for spawning. Utah Division of Wildlife Resources personnel or other government agency volunteers were stationed at the reservoir for 24 hours per day while the inflow trap was in operation. Spawning was conducted on June 18 and 25. The overall project and schedule was supervised by Glenwood Fish Hatchery personnel. Spawning was conducted by personnel from Egan Fish Hatchery. All fish were sorted and ripe fish were spawned using standard state methods. Females were spawned 10 fish at a time, with enough fish spawned to easily exceed 20 paired matings. Females and males were spawned at a ratio of about 2:1. Five males were deemed sufficient to fertilize eggs taken from 10 females. Eggs were water hardened for at least an hour and then transported to the Fish Lake isolation station for incubation. Loa Hatchery personnel were responsible for egg care during incubation, until the eggs were fully eyed and then moved to the Glenwood Fish Hatchery for further rearing. Disease certification was completed as required by standard protocol, including a 60-fish lethal sample and ovarian fluids from 60 different females. Disease work was conducted by personnel from the Fisheries Experiment Station, Logan, Utah. Some of the lethal sample for disease certification was obtained from gill-net surveys conducted concurrently with spawning actives. The remainder of the 60-fish sample that could not be obtained from gill nets was taken from the spawning trap. Gill-net surveys were used to compare population trend data and condition of fish among years. Data was recorded and tabulated to keep records on spawning times, number of trout trapped, number of fish spawned, size of trout, and number of eggs taken. In addition, data was recorded on relative fish densities and condition (KTL) of fish in the reservoir to allow adjustments in reservoir stocking rates and management of the brood stock. Measurements and estimates of various parameters are presented, at times, in English and metric units. English units were generally used to facilitate comparisons among fish culture aspects of the project. Trend data was reported in metric units, allowing consistency in comparisons among related data. Results and Discussion Spawning during 2003 occurred during mid-June, about mid-range for all years that spawning has been conducted at Manning Meadow Reservoir (Table 1). Total number of eggs taken was the third highest for all years, but less than the last two years (Tables 2 and 3). The project was completed by spawning on two days, scheduled a week apart, compared to some years that required 3 weeks and 3 spawns to collect even less eggs. Total number of trout trapped peaked in 2001 at 1,809 and decreased to 753 in 2003. Size of trout and number of eggs per female continued to increase through 2003, reaching the highest values since 1994-1995. Reservoir stocking since 1998 and the most recent fishing regulations were adjusted to reduce overall fish density, increase mean age and size of trout, and maximize egg-taking potential. Since trend netting data was first conducted in 2000, mean fish length increased from 296 to 359 mm and mean weight more than doubled from 280 to 596 g (Table 4). Also, condition improved from 1.05 to 1.29. Of concern, however, the overall gill-net catch dropped to 8 fish per net-night in 2003 (Table 4). Catches of 20-30 trout per net-night are considered good with higher values thought to be excessive enough to impair growth and condition of trout. Trends at Manning Meadow Reservoir during 2000-2002 were higher than desired but then suddenly dropped to lower than desired levels in 2003. Netting data may have been an artifact of poor conditions for catching fish resulting in sampling error, but trends in trout numbers collected in the spawning trap, overall increases in average fish size, and increased mean condition seem to verify a substantial reduction in reservoir fish density. Discontinued stocking of “holdovers” since 1998 was the main means of reducing overall trout abundance (Table 5). Since then, replacement of the reservoir brood stock has been totally dependent on stocking of “fry.” Fry are deemed a better alternative to stocking holdovers (providing that survival is adequate) because: (1) fry minimize any potential selection on the brood stock due to hatchery rearing; (2) they have an appearance similar to wild trout with little fin damage compared to holdovers; and (3) stocking of fry minimizes the chance of inadvertently stocking other nonnative trout from a hatchery source compared to holdovers. The abundance of holdovers (identifiable by fin condition) in gill-net samples and spawning traps declined to 25 % during 2003 (Table 4). Holdovers were at least 6 years old -- the last time they were stocked was 1998 (Table 5). Conversely, 75% of all the fish observed during 2003 resulted from stocking fry. Although holdovers have been observed to spawn at ages 2-3, they have the advantage of extra growth from being held in a hatchery over-winter. It is expected that trout stocked as fry generally would not mature until age 3 or 4. This being the case, most trout spawned during 2003 that were stocked as fry, were likely introduced into the reservoir in 1999 and 2000 when over 12,000 fry were stocked each year. After that, stocking was reduced to approximately 10,000 fish in 2001 and no stocking at all in 2002. A review of the stocking history, gill-net results, and spawning totals suggests that further declines in the population of spawning adults might occur over the next year or two. It is recommended that stocking be increased to 15,000 - 20,000 fry per year. Hopefully, this will compensate for holdovers being totally displaced from the population and keep spawning and egg-taking capabilities in the range that has occurred the past 3 years. Prior to 1990, Manning Meadow Reservoir was managed with Yellowstone cutthroat trout. A regular quota of 20,000 fry was stocked per year but adult fish had slightly less than desired mean lengths, weights, and condition factors. In recent years, Bonneville cutthroat trout numbers, size and condition have been close to desired levels, but it will likely be necessary to increase stocking of fry to maintain these levels. Table 1. Bonnevile cutthroat trout spawning times at Manning Meadow Reservoir, Utah 1992- 2003. Year Trap operation dates Dates spawned Number days spawned Lake water temperature (Fahrenheit) Begin End First Last First spawn Last spawn 1992 2 June 30 June 16 June 30 June 3 55 62 1993 21 June 6 July 22 June 6 July 3 62 62 1994 14 June 22 June 16 June 22 June 2 56 60 1995 3 July 11 July 5 July 11 July 2 60 62 1996 24 June 2 July 26 June 2 July 2 58 60 1997 23 June 1 July 25 June 8 July 3 59 62 1998 29 June 13 July 1 July 13 July 3 58 63 1999 18 June 6 July 22 June 6 July 3 58 62 2000 5 June 13 June 6 June 13 June 3 58 59 2001 12 June 20 June 14 June 20 June 2 58 61 2002 7 June 18 June 11 June 18 June 2 58 61 2003 13 June 25 June 18 June 25 June 2 55 57 Table 2. Spawning totals at Manning Meadow Reservoir during 2003. Date Lake water temperature Number females spawned Number males spawned Total eggs Eggs per ounce Mean number of eggs per female 18 June 55 202 100 163,836 369 811 25 June 57 68 49 59,778 369 879 Total -- 270 149 223,614 369 828 Table 3. Bonneville cutthroat trout spawning totals at Manning Meadow Reservoir for 1992-2003. Year Number of females spawned Mean length (inches) Total eggs Eggs per fluid ounce Mean number of eggs per female Total number of trout trapped Female Male 1992 27 13.4 -- 19,218 361 712 -- 1993 61 15.2 -- 61,148 328 1002 -- 1994 45 15.8 -- 57,000 345 1267 -- 1995 218 13.5 14.4 176,896 383 811 -- 1996 198 13.5 14.2 136,980 283 691 485 1997 141 14.4 14.8 92,603 368 657 271 1998 116 14.3 12.7 80,514 359 694 330 1999 296 12.4 13.1 198,895 420 672 744 2000 265 12.7 13.2 173,484 377 655 1099 2001 516 12.9 13.5 330,129 375 640 1809 2002 560 13.4 14.1 368,688 327 658 1310 2003 270 14.1 14.5 223,614 369 828 753 Table 4. Annual trend gill-net results at Manning Meadow Reservoir, 2000 - 2003 (CTSB = Southern Bonneville cutthroat trout). Year Number nets set overnight and (total CTSB caught) Number CTSB caught per net-night Mean total length (mm) (range) Mean weight (g) (range) Mean KTL Number CTSB from “fry” stocking (%) Number CTSB from “hold-over” stocking (%) Floaters Divers 2000 1 (79) 1 (86) 83 296 (187- 391) 280 (67- 596) 1.05 74 (45% ) 91 (55%) 2001 1 (38) 1 (90) 64 310 (213- 397) 320 (79- 597) 1.07 84 (66%) 44 (34%) 2002 1 (46) 1 (72) 59 332 (220- 380) 427 (119- 636) 1.15 78 (66%) 40 (34%) 2003 1 (7) 1 (9) 8 359 (288- 409) 596 (317- 1050) 1.29 12 (75%) 4 (25%) Table 5. Total number, size, and age of Bonneville cutthroat trout stocked in Manning Meadow Reservoir as brood stock replacement, 1990-2002. Transplants were of various sizes and ages, holdovers were age 1 (5-8 inches mean total length), and fry were age 0 (1.5-2.5 inches mean total length). Holdovers were stocked in June and July. Fry were stocked in October. Year Number fish stocked Transplants Holdovers Fry 1990 469 -- -- 1991 245 -- -- 1992 -- -- -- 1993 -- 1,995 -- 1994 -- 1,999 4,648 1995 -- -- 6,024 1996 -- -- 5,060 1997 -- 1,499 8,202 1998 -- 2,008 9,506 1999 -- -- 12,428 2000 -- -- 12,001 2001 -- -- 10,729 2002 -- -- --
geography
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Tue, 05 May 2020 19:04:31 +0000
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