Comparison of survival rates between domesticated and semi-native char using Bayesian multi-variate state-space model

Abstract

Streams depleted of their native salmonid populations are often stocked with domesticated fish for supplementation. However, these domesticated salmonids have a lower adaptability to environmental conditions and thus have a lower survival rate than “native” salmonids. Recent studies suggest the stocking of “semi-native” strains of fish (hybrids between native males and domesticated females) as an alternative to domesticated fish. We evaluated the difference in the apparent survival rates of semi-native and domesticated juvenile char after their stocking in mountain streams. The analysis used multi-site variable time-series data with a Bayesian multi-variate state-space model reflecting the characteristics of the data, including time-series variation, site-specific effects, and observation error. The resulting odds ratio, which represents the general and potential strain effect of the semi-native char stocking, was 2.49 (95% CI = 2.12–2.94), implying that the apparent survival rate of the semi-native char was approximately 2.5 times higher than that of the domesticated char in the mountain streams studied. The results suggest that hybridization might be a viable approach for stocking and harvest augmentation of the commercial and recreational fisheries in fragmented populations.