Science Advisory Report  2012/011

Pre-season run size forecasts for Fraser River Sockeye in 2012

Summary

• Salmon forecasts are in general highly uncertain due to wide variability in annual survival rates from the egg stage to adult returns.
• For Fraser Sockeye, quantitative or qualitative indicators of survival explored to-date have not reduced forecast uncertainty and remain an active area of research.
• In the absence of indicators, Fraser Sockeye forecasts have been particularly uncertain in recent decades due to persistent declines in productivity exhibited by most stocks, with the lowest productivity on record observed for the 2005 brood year (2009 four year old and 2010 five year old returns). The subsequent 2006 (2010 four year old returns) and 2007 (2011 four year old returns) brood year stock productivities appear to have improved.
• The 2012 single forecast scenario differs from recent years forecasts that presented two scenarios: Recent Productivity (stock-specific forecasts used best performing recent productivity models evaluated only in recent low productivity periods) and Long-Term Average Productivity (stock-specific forecasts used best performing long-term average productivity models evaluated over the entire time series).
• In contrast, the 2012 forecast presents only a single forecast scenario. Under this scenario, the stock-specific forecasts were produced using either recent productivity or long-term productivity (full time series) models, selected largely based on their ability to predict a stock’s true returns over its full stock-recruitment time series. Stock-recruitment data included up to the 2004 brood year.
• The 2012 forecast indicates a one in 10 chance (10% probability) the total Fraser Sockeye return will be at or below 743,000, and a nine in 10 chance (90% probability) it will be at or below 6.6 million, given that stock productivity is similar to past observations. The mid-point of this distribution (50% probability) is 2.1 million at which there is an equal chance the return will be greater or less.
• Summer Run stocks, particularly Chilko, Late Stuart and Stellako, are expected to contribute 67% to the total return forecast, whereas Early Stuart (5%), Early Summer (17%) and Late Run stocks (11%) will each contribute considerably less.
• The 2012 Fraser Sockeye forecasted return distribution falls largely (up to a three in four chance, based on past observations) below the cycle average (3.8 million). The below average return is attributed to the well below average 2008 brood year escapements for Early Summer and Late Run stocks.
• The 2012 Fraser Sockeye return has the potential to be amongst the lowest observed on this cycle if stock productivities are at the low end of past observations.
• Due to the lower 2008 escapements (which produce four year olds in 2012) relative to 2007 (which produce five year olds in 2012), the total forecasted four year old return proportion (~75%) is below average (82% average four year old proportions for all stocks combined, excluding Harrison). Expected four year old proportions range from 10% to 98%, depending on the stock.

This Science Advisory Report has resulted from a Fisheries and Oceans Canada, Canadian Science Advisory Secretariat, Regional Peer Review Meeting on February 1, 2012 on the Assessment of Fraser River Sockeye Salmon and Forecast 2012.  Additional publications from this process will be posted as they become available on the Fisheries and Oceans Canada Science Advisory Schedule.

Complete document (PDF, 176 KB)

Accessibility Notice

This document is available in PDF format. If the document is not accessible to you, please contact the Secretariat to obtain another appropriate format, such as regular print, large print, Braille or audio version.