Fraser River Sockeye Fisheries and Fisheries Management - Cohen ...

survey 20 times, 19 of the survey results would be within this confidence interval. Inother words, there is a 1 in 20 (5%) chance that the survey result will be outside the 95%confidence interval (e.g., the 2010 sockeye return was above the upper limit of the 95%confidence interval).For the purpose of this report:Precision of the methods and estimates will be assessed within years by examining thesize of confidence intervals associated with the resulting estimates. Where possible, weprovide the 95% confidence intervals expressed as a percentage of the estimate(e.g. ± 10%).The term “reliability” is often used to combine both precision and accuracy. In someinstances, we may not be able to quantify accuracy or precision but there may besufficient information to indicate whether or not an estimate is reliable. For example, thecatch estimates that are based on mandatory reporting in log books or at landing sites canbe evaluated in terms of compliance with these mandatory reporting requirements. Ifmost fishers report their catch and the portion of active fishers reporting is known, theestimates would be highly reliable. With regard to escapement, where the “actual”number of spawners is never known, reliability is typically used as a relative term. Themost reliable estimates are those derived from counting fences or rigorous mark-recaptureprograms whereas unreliable estimates are derived from visual surveys where waterclarity is poor or effort is insufficient to cover the spawning grounds or spawning period.For the purpose of this report:Reliability of the methods will be qualitatively assessed on a relative basis (e.g., MethodA is more reliable than Method B).Reliability of the estimates will also be qualitatively assessed on a relative basis usingavailable information on the application of method (e.g., we assess whether the surveyeffort was sufficiently large in scope to produce a reliable estimate).Our evaluations of the pre-season and in-season run size forecasting methods used forFraser and Bristol Bay sockeye stocks included more quantitative assessments of theaccuracy, precision, and reliability of the forecasts. Additional clarification of theseterms are found under the relevant headings.16