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

Number of years from 1980 to 20051086420Mean = 4%0 2 4 6 8 10 12 14% of escapement not countedFigure 37 Projected percent of the sockeye escapement that would not have beencounted if the 3-day-under-1% rule for ending enumeration projects hadbeen used for the Nushagak River, Alaska.In-season forecasting of total run from catch and escapementResearch staff uses the cumulative catch and escapement (C+E) to a given date toforecast total run to a district or river system. Given the effects of subtle changes in runtiming can have on these forecasts, the estimates are not particularly precise until later inthe season when about 60% of the run has returned. In-season forecasting methods andresults are not made public by ADF&G nor are they consistent across managers in BristolBay. Some AMBs routinely liken the current year’s cumulative C+E to a year in the pastwith a similar entry pattern and magnitude to give a guesstimate of what to expect for theyear-end total (P. Salomone, pers. comm.). Others divide the current year’s cumulativecatch and escapement (C+E) by what proportion of the total run has historically returnedon a given date. Forecasts can be made for each system separately, except where twosystems empty into a common commercial fishing district in which case the forecast isjust district specific. Some river systems are more amenable than others with respect toproviding accurate forecasts. Further, river systems vary with respect to accuracy on agiven date, due to minor differences in run timings. ADF&G begins to use thisforecasting technique for a given system to some extent after they feel 50%-60% of the160