Proportions of Hatchery Fish in Escapements of Summer‐Run Chum Salmon in Southeast Alaska, 2013–2015

Abstract

The Alaska salmon hatchery program is intended to supplement salmon fisheries without supplanting wild stocks. Hatchery‐origin Chum Salmon Oncorhynchus keta spend most of their lives interacting with wild salmon, including some degree of straying to spawning streams. Our study was designed and implemented to measure the extent and annual variability of straying by hatchery‐produced, summer‐run Chum Salmon in Southeast Alaska from 2013 to 2015 by sampling in individual streams to estimate the proportion of hatchery strays. In the sampled index streams, the proportion ranged from 0.000 to 0.854 over the 3 years. Unbiased estimates of the proportions of hatchery‐origin fish spawning in each of the three management units ranged from 0.016 to 0.081, and the estimated hatchery proportions spawning across Southeast Alaska ranged from 0.032 to 0.060. The proportion of hatchery strays decreased as the distance from hatchery release sites increased; proportions were highest at streams located within 50 km of the nearest release site. The proportion of hatchery‐origin spawners was negatively related to the index of spawning escapement in a stream. A hatchery donor stray rate of 0.8–4.8% was estimated. Hatchery‐origin Chum Salmon occur at low levels in most Chum Salmon systems in Southeast Alaska and at higher levels in systems close to hatchery release sites.

Big Catch, Undecided Risks: Perspectives of Risk, Reward, and Trade‐Offs in Alaska's Salmon Enhancement Program

“…Given the significant body of literature showing that hatchery breeding and rearing practices have a demonstrated impact on salmon and given ongoing findings from ADFG's straying study that demonstrate mixing between hatchery‐ and non‐hatchery‐origin salmon (ADFG 2021b; Josephson et al. 2021; Knudsen et al. 2021; Shedd et al.…”

“…This language raises a key question: what does "without adverse impact" mean? Given the significant body of literature showing that hatchery breeding and rearing practices have a demonstrated impact on salmon and given ongoing findings from ADFG's straying study that demonstrate mixing between hatchery-and non-hatcheryorigin salmon (ADFG 2021b;Josephson et al 2021;Knudsen et al 2021;Shedd et al 2022), it is reasonable to infer that hatchery-reared fish are having some kind of impact on non-hatchery salmon and their ecosystems. With that in mind, the pressing questions then become (1) "What does 'adverse' mean to salmon stakeholders?…”

Salmon hatchery strays can demographically boost wild populations at the cost of diversity: quantitative genetic modelling of Alaska pink salmon

“…However, concerns have risen over potential adverse ecological and genetic impacts of hatcheries on wild populations [3][4][5][6][7]. The impacts of large-scale fishery enhancement programs, intended to allow harvest segregation of hatchery and wild populations, are particularly controversial [1,8,9], in part because many unharvested hatchery-origin individuals may 'stray' onto the spawning grounds of wild populations [10,11]. Although straying occurs naturally among wild salmon populations [12], and hatchery strays are typically a small fraction of total returns, hatchery programs operating on scales of tens of millions of returning adults can contribute substantially to wild population demographics [11].…”