Abundance of Skeena River Chum Salmon during the Early Rise of Commercial Fishing

Abstract

We used reported commercial catch data and historical information to estimate the abundance of Skeena River Chum Salmon Oncorhynchus keta during the early rise (1916)(1917)(1918)(1919) in the commercial fishery to provide historical perspective for recovery plans. We applied a Bayesian analysis to address the uncertainties associated with the estimation process. Based on the historical catch of 204,000 in 1919 and an estimated harvest rate of 0.32-0.58, the estimated return of Skeena Chum Salmon ranged from 355,000 to 619,000, with the most probable single estimate being 431,000. The estimated return of Chum Salmon based on the 1916-1919 geometric mean catch of 154,000 ranged from 268,000 to 471,000, with the most probable single estimate being 325,000. Our posterior modal historical estimates are 8-11 times larger than the estimates for the contemporary period 1982-2010 and 39-52 times larger than those for the most recent period of 2007-2010. Intense harvest pressure is the single most probable factor explaining the sustained decline in Chum Salmon abundance, but other interactive factors, notably natural variations in survival, the loss of spawning and rearing habitat, and poor data quality, also are important considerations. Nonetheless, the Skeena catchment is largely pristine today, and our robust estimates of historical abundance should be of value to contemporary management and conservation agencies for the rebuilding of such severely diminished populations.

Juvenile Salmon Usage of the Skeena River Estuary

“…On a finer scale, the proposed development region contained particularly high salmon population diversity, with individual fish assigned to 13 sockeye salmon and 4 Chinook salmon populations. Some of the fish that we captured in this proposed development region are of conservation concern, such as sockeye salmon from Morice and Lakelse lakes and chum salmon from throughout the Skeena River watershed, for which low escapements in recent years compared with historical abundances have prompted calls for recovery planning [ 30 ]. Our data indicate that the Skeena estuary, especially the areas where development projects are proposed, represents important habitat for multiple salmon species and populations.…”

“…The total returns are higher when the various fisheries are taken into account—the Northern Boundary Technical Committee of the Pacific Salmon Commission estimate an average run size of nearly 3,000,000 sockeye salmon (1985–2012) with an average exploitation rate of 41% [ 28 ], and an average exploitation rate for Chinook salmon of about 50% [ 28 ]. Chum salmon are the least numerous of the commercially-exploited anadromous species, with estimated escapements of several thousand in recent years [ 29 ], considerably less than historical abundances [ 30 ]. Steelhead returns to the Skeena River during the past decade have been between 20,000 and 50,000 [ 31 ].…”

Criteria for a good catch: A conceptual framework to guide sourcing of sustainable salmon fisheries

“…We believe that place-based salmon management is most likely to succeed when most, perhaps all, salmon harvest occurs at spatial scales closer to the rivers of origin than today's mixed-stock marine fisheries, much as it did in the early 20th century (Lichatowich 2013;Price et al 2013). Data requirements for place-based management are likely to be relatively high in the short term because of neglect on the part of management agencies to prioritize or fund regular monitoring of smaller spawning populations often caught in mixed-stock fisheries (Price et al 2008(Price et al , 2017Lichatowich et al 2017).…”