Science Response 2014/041

Supplement to the pre-season return forecasts for Fraser River Sockeye Salmon in 2014

Context

Since most Fraser Sockeye Salmon return as four year old fish after spending two winters in freshwater and two winters in the marine environment, the majority of Sockeye returning in 2014 will be recruits from eggs spawned by adults in 2010 (i.e. the 2010 brood year). Predicting Fraser Sockeye returns in 2014 is a particular challenge, given the exceptional escapements observed for a number of stocks in the 2010 brood year (including Scotch, Seymour, Chilko, Harrison, Late Shuswap, and Portage). These record high brood year escapements require that forecast models be extrapolated beyond the observed stock-recruitment data range, creating additional uncertainty in forecasts for 2014. However, juvenile (fry and smolt) data for various key stocks in the 2010 brood year (Shuswap and Chilko) provide evidence of density-dependent compensation (lower freshwater survival) due to these record high spawner abundances. The juvenile data, therefore, support model forms that predict overcompensation at high spawner abundances.

To provide further context for the 2014 Fraser Sockeye forecasts, additional information on the condition of Fraser Sockeye throughout their various life-history stages is reported in the current document. The Shuswap, Chilko, and Harrison stocks are evaluated, given their unprecedented high escapements in 2010. Quesnel is also included, due to poor survival observed for this stock in recent years, which diverges from the improvements in survival observed for most other Fraser Sockeye stocks between the 2006 and 2009 brood years (2010 to 2013 return years). Fish and environmental conditions are examined for the adults spawners in 2010 (all stocks), fry in 2011 (Shuswap and Quesnel lakes only), outmigrating smolts in 2012 (Shuswap and Chilko), Fraser River downstream smolt migration at Mission (all stocks), and subsequent Strait of Georgia and Johnstone Strait juvenile migrations (all stocks). In addition, the stock composition in the 2010 escapements, and 2012 smolt downstream migration and juvenile ocean surveys, and 2014 return forecasts are compared to evaluate proportional changes through time. This information will be used to supplement DFO’s official Fraser River Sockeye Salmon forecasts.

This Science Response Report results from a Regional Science Response Process held January 2014 to summarize data on fish condition and/or survival (including adults escapement in 2010 and their juvenile offspring). This Science Response is intended to provide context for the official DFO Fraser Sockeye forecasts in 2014.

Complete document (PDF, 3,948  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.