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

Catch from fishing districts with only one stream system are assigned to that stream (i.e.,Togiak, Ugashik, and Egegik). For districts with more than one river system, catch hashistorically been apportioned post-season based on relative escapements by age (Bernard1983). For instance, the catch of sockeye age-2.2 in the Kvichak-Naknek District isapportioned between the Kvichak and Naknek systems based on the relative proportion ofage-2.2 fish that occurred in each escapement.It has always been assumed that once sockeye enter the Bay, interception of fish in nonnataldistricts and streams was for the most part negligible, but assumptions createuncertainty. However, these assumptions have not been needed in recent years due togenetic stock identification (GSI) from catch samples. Dann et al. (2009) found thepercent of the Kvichak run harvested in the Ugashik and Egegik districts was 4.7% in2006, 4.9% in 2007, and 13.2% in 2008. An additional genetics study is underway thatwill estimate the stock compositions for the historical database based on scale samplestaken in earlier years (T. Baker, pers. comm., ADF&G). Better estimates of riverspecificharvest may change historical and future catch assignments enough to alterpreviously held conceptions of abundance trends and spawner-recruit relationships forsome systems (Baker et al. 2009), but we doubt these changes will be substantial.Harvest estimatesHistorical harvest from Bristol Bay has been characterized by two features (Figure 27;Appendix L). First, there has been a decadal pattern in productivity and catch regimesattributed to the Pacific Decadal Oscillation, which has contributed to periodic and twotothree-fold shifts in catches across some decades. Second, the Bay-wide run followed acycle of high catches for one and two years followed by “off-cycle” years of lowercatches, driven by the dynamics of the Kvichak River system (Figure 27; Eggers andRogers 1987; Fair 2003). Reasons for this cycle have not been definitive, and debate inthe Bay and the scientific literature continues, but the data suggest it was influenced bymarine and freshwater processes and largely reinforced by historical fishing patterns anda cyclic escapement goal policy (Ruggerone and Link 2006). Whatever the cause, thecycle began to break down during the mid-1990s and the Kvichak has failed to dominatethe Bay-wide run since. Harvest has ranged from 9.9 to 44.2 million fish with an averageof 25.5 million over the past 20 years (1991-2010; Appendix L). The Egegik stock hasdominated this period with an average harvest of 8.7 million followed by the Kvichakand Naknek stocks with 4.3 and 3.5 million. Since 2004, harvest has been quite stable(average=28.0 million, range = 24.4-30.9).136