Stave River Water Use Plan - BC Hydro

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Stave River Water Use Plan Monitoring Terms of Reference June 13, 2005 2.2 Approach Fish biomass estimation will rely on hydro-acoustic survey data collected annually at a standardised time of the year. Reservoir elevation should also be similar so that sampling conditions are consistent between years. Each year, the biomass estimate and corresponding error values will be plotted with previous year’s data. Trend analysis will be used to determine the likelihood that fish biomass is increasing, remaining the same, or decreasing. To help interpret the hydro-acoustic survey data, a fish survey will be carried out as well. These surveys will only be done every second year and will consist of day and night trawls, minnow trapping, and gillnetting techniques. One of the outcomes of the survey is to associate target strength and location data with particular fish sizes and species. It is also an opportunity to collect fish morphometric data for between-year comparisons and to test for correlations with littoral and pelagic primary productivity data collected in Monitors 1 and 2. 2.3 Methods 2.3.1 Field Methods Field methods will consist of two parts, a hydro acoustic component that collects fish size and abundance data and a fish survey component that is needed to group the size and abundance data in to species and size at age categories. The two parts are described in the sections that follow. Hydro Acoustic Survey A hydro acoustic survey of Stave Lake will be carried out annually at a standardised time of year, preferably in late summer. In year one of the monitor, the optimal configuration of sounding equipment, as well as a standardised pattern of sounding transects, will be developed to standardise the data collection procedure. This will allow the survey to be replicated in subsequent years and hence minimise the potential for inter annual sampling error. Hydro acoustic surveys will be done with specially designed echo-sounding equipment and supporting software, and will involve to use of split beam transducers and/or transducer rotators to improve sounding accuracy in Stave reservoir’s difficult shoreline and bottom terrain. Surveys will be carried out both at night and during the day to track potential diel movements (vertical or offshore migration patterns) which may affect biomass estimation results. The level of sampling effort should not exceed 2 days for all sampling needs (this excludes travel costs, which may be extensive, since there are few qualified operators in BC). This specified level of effort should be sufficient to adequately sample the reservoir (B. Sables pers. comm.). Fish Survey Fish morphometric data will be needed to help interpret the hydro-acoustic survey data. Fish capture will involve a number of techniques, including the use of day BC Hydro Page 44
Stave River Water Use Plan Monitoring Terms of Reference June 13, 2005 and nigh trawling sets (requires the use of a specially equipped boat), and a variety of gillnet sets. Both day and night time gillnet sets will be done, and will include floating, sinking, and drifting sets. All sampling will conform to RIC standards (1998) and the level sampling effort is not to exceed that which can be reasonably accomplished by a two-person crew over a three-day period. This level of sampling effort should be sufficient to meet the needs for interpreting the hydro-acoustic data (B. Sables pers. comm.) All fish caught during the survey will be identified to species and measured for standard length and wet weight. If necessary, fish will be anaesthetised by CO2 saturation prior to measurement. Fish found alive in the traps will be returned to the reservoir. Dead fish however, will be autopsied in the field for sex, gonadal maturity, and stomach content information. 2.3.2 Safety Concerns A safety plan will have to be developed for all aspects of the study in accordance to BCH procedures and guidelines. Of particular concern is the night-time operation of boats in the reservoir, which has few landmarks that are visible at night for navigation. Also of concern will be boater safety during the fish sampling procedure, as there tends to be high recreational boat use during the preferred time of sampling. High recreational use in the reservoir also raises the issue vandalism, which can be prevalent in the area. 2.3.3 Data Analysis Fish biomass (kg·ha -1 ) will be estimated using standard software designed specifically for translating hydro-acoustic survey data. The biomass estimate and corresponding estimate of error will be appended to previous year’s data to be plotted as a time series. Each year, trend analysis will be carried out determine the likelihood that biomass is increasing, remaining the same, or decreasing. Results of this analysis will determine whether hypothesis H01 is to be accepted or rejected. It should be noted that every second year, interpretation of the hydro-acoustic survey would have to rely on fish morphometric data collected from the previous year’s survey. Fish catch and morphometric data will be described using simple descriptive statistics and summary tables. The primary intent of the analysis will be to support interpretation of hydro-acoustic survey data. However, because of the nature of the data, between year comparisons of catch-per-unit-effort and fish morphometry (e.g., condition factor) may be possible and should be pursued if the analysis can be done at little or no additional cost to the overall program. Correlations between cohort biomass estimates and indicators of pelagic and littoral productivity will be examined using univariate and multivariate regression analysis. The possibility of lagged effects (e.g., productivity in year 1 has a consistent effect in year 3) will be incorporated into the analysis as well. Assumptions of normality, linearity and homoscedasticity will be verified prior to all statistical testing and if necessary appropriate data transformations will be carried out. BC Hydro Page 45
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Stave River Water Use Plan - BC Hydro

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