A comparison of the growth histories of pre- and post-decline brood years of sockeye salmon (Oncorhynchus nerka) from Rivers Inlet based on otolith analysis and in relation to environmental conditions

The widths of growth zones recorded on otoliths of sockeye salmon (Oncorhynchus nerka) from Rivers Inlet were measured to assess the impacts of environmental conditions on growth at different life history stages. Otoliths from the pre-decline (1984-1987) and post-decline brood years (1997-2005) were compared. Post-decline juveniles were significantly larger than pre-decline individuals during the migration to sea, but grew less in the first marine year. Final size was not significantly different between time periods. Functional regression analyses were performed to investigate the relationship between otolith growth and sea surface salinity at McInnes Island. Otolith growth was positively correlated with salinity during September and October. Decreased salinity under a 30 ppt threshold appears to have signalled recent unfavourable oceanic conditions for growth and possibly survival.