Volume 081 Article 07 Little Salmon River Spring Chinook Oncorhynchus tshawytscha Sport Harvest, 1986 to 1990 By Peter F. Hassemer Fishery Research Biologist July 1991 TABLE OF CONTENTS INTRODUCTION ............................................................................................................1 METHODS ..................................................................................................................... 1 Sport Fishery Creel Survey ..................................................................................1 1986 Creel Survey .................................................................................... 2 1987 Creel Survey .................................................................................... 4 1988 Creel Survey ................................................................................... 4 1990 Creel Survey ................................................................................... 5 Nez Perce Tribal Harvest ...................................................................................... 5 Rapid River Hatchery Rack Returns ..................................................................... 6 Spring Chinook Run Prediction Models ................................................................ 6 RESULTS ...................................................................................................................... 6 Sport Fishery Effort and Harvest ......................................................................... 7 Nez Perce Tribal Harvest ...................................................................................... 7 Hatchery Rack Returns .........................................................................................12 Brood Year Return Analysis ..................................................................................12 Spring Chinook Run Prediction Models ................................................................12 DISCUSSION ...................................................................................................................17 LITERATURE CITED ........................................................................................................19 i LIST OF TABLES Table 1. Estimates of angler effort and harvest for the 1986 through 1990 Little Salmon River chinook salmon sport fisheries. Estimates are stratified by weekend and weekdays periods. Number of days reported is the number of open fishing days, not angler days ................................................... 8 Table 2. Spring chinook sport fishery and Nez Perce Tribal harvest estimates and Rapid River hatchery rack returns for Rapid and Little Salmon rivers, 1984-1990. Nez Perce Tribal harvest estimates are from Mauney (1990) except as indicated ............................................................................................................................10 Table 3. Little Salmon River/Rapid River area spring chinook salmon sport and Nez Perce Tribal harvests and hatchery rack returns classified by age, 1984-1990 ..............................................................................................................................................13 Table 4. Little Salmon River/Rapid River area spring chinook salmon brood year returns by age class, and total brood year returns estimated from sport and tribal harvests and hatchery rack returns, 1984-1987. Brood year returns for 1986 and 1987 are incomplete .............................................................................15 Table 5. Models tested for predicting the returns of 4-year old and 5-year old spring chinook to the Rapid River/Little Salmon River area............................................16 ii LIST OF FIGURES Figure 1. Effort (angler hours) and harvest in the 1990 spring chinook sport fishery on the Little Salmon River................................................................9 Figure 2. Percent of spring chinook salmon returning to the Little Salmon River/Rapid River area accounted for at the hatchery rack and in the sport harvest and tribal harvest, 1986-90...................................................................................11 Figure 3. Returns, by age class, of spring chinook salmon to the Rapid River hatchery rack, 1984 - 1990 ........................................................................................................................14 Figure 4. Rapid River/Little Salmon River area spring chinook salmon brood year returns to the Rapid River hatchery rack and brood year harvests in the sport and Nez Perce Tribe subsistence fisheries, 1981 - 1985 brood years ...............................................................................................................18 iii ABSTRACT The Idaho Department of Fish and Game operates Rapid River hatchery as a spring chinook (Oncorhynchus tshawvtscha) production facility, with funding provided by Idaho Power Company. Estimated annual spring chinook returns to the Little Salmon River/Rapid River area have ranged from 3,344 to 10,008 for the period 1986 through 1990. Harvestable surpluses in 1986, 1987, 1988, and 1990 allowed limited sport fisheries in those years, and sport harvests ranged from 422 to 1,430 spring chinook. Chinook sport anglers harvested 6.3% to 14.3% of the total return to the Little Salmon River/Rapid River area when sport seasons were open. iv INTRODUCTION Rapid River hatchery is a spring chinook (Oncorhynchus tshawvtscha) production facility operated by the Idaho Department of Fish and Game (IDFG). Operational funds are provided by Idaho Power Company (IPC), as part mitigation for the Brownlee, Oxbow, Hells Canyon dam complex on the mid-Snake River. The spring chinook stock returning to the facility was developed from transplanted mid-Snake River chinook collected at Hells Canyon dam beginning in 1964 (Howell et al. 1985). Rapid River is a tributary to the Little Salmon River, entering approximately four miles above the confluence of the Little Salmon and Salmon rivers. Spring chinook migrating through the Little Salmon River on their return to the hatchery have provided harvest opportunities for sport anglers. Members of the Nez Perce Tribe (NPT) also utilize spring chinook returning to Rapid River for ceremonial and subsistence harvest. In addition to funding hatchery operations, IPC also has provided funds to monitor and evaluate the sport fishery in years when it was open. The purpose of this report is to provide estimates of sport harvest from 1986 through 1990. Also included are tribal harvest estimates and hatchery rack return information. Returns by brood year are provided and estimates of brood year return are made. Finally, models were developed to predict returns of 4-year and 5-year old spring chinook salmon using previous brood year return information. METHODS Sport Fishery Creel Survey Chinook salmon sport fisheries on the Little Salmon River were allowed most recently in 1986, 1987, 1988, and 1990. Season structures varied among years to satisfy specific management objectives for each year. Changes in season structure required modifying the format of the creel survey used to estimate sport harvest each year. Each year's survey format is described separately below. While conducting creel survey angler interviews all fish harvested by interviewees were sexed and measured (fork length, nearest cm). Length measurements were used to determine the age composition of the catch. Spring chinook returning to Rapid River are classified as either jacks, 4-year olds, or 5-year olds (see Rapid River Hatchery Rack Returns for age descriptions). The 1986 through 1988 sport fisheries were limited to the 4 mile section of the Little Salmon River from its mouth upstream to the mouth of Rapid River. 1 The fishing area was extended in 1990 to include approximately 15 miles of the Little Salmon River above Rapid River. 1986 Creel Survey Length of a fishing day was 17.5 hours (4:00 AM to 9:30 PM). Each fishing day was divided into three 3-hour periods (strata) within which angler counts and interviews were conducted. The 3-hour periods were: 6:00 to 9:00 AM, 12:00 noon to 3:00 PM, and 6:00 to 9:00 PM. A roving creel survey (Neuhold and Lu 1957) using a stratified, sampling with replacement sample design was used to estimate angler effort and harvest. Count/interview sessions were conducted during two of the three 3-hour strata each day. Angler counts were made at the beginning and end of each stratum, with angler interviews conducted between the counts in each stratum. All angler counts were completed within one hour and are considered instantaneous counts. The two strata to be sampled on the first survey day of the fishing season were randomly chosen. On the second and subsequent survey days the one strata not sampled on the previous survey day was automatically selected to be sampled on that survey day. The second strata to be sampled on a survey day was randomly selected from the other two strata. Fishing effort (angler hours) was estimated using the angler counts. Angler interviews were used to estimate catch and harvest rates. Because of increased angler effort on weekends, estimates of effort, catch rates, and harvest were stratified by weekend and weekday periods (holidays were considered weekend days). Total effort and harvest for the season were obtained by summing the weekend and weekday effort and harvest estimates. Interviews with anglers who had not completed their fishing trips were used to estimate catch and harvest rate.