The Effectiveness of Semi-Natural Rearing of Coho Salmon (Oncorhynchus kisutch) at the Nitinat River Hatchery, British Columbia

Robert Brouwer1, Amanda Ross1, Ian Trepanier1, Ronald W. Tanasichuk2, *
1 Fisheries and Oceans Canada, Nitinat River Hatchery, P.O. Box 369, Port Alberni, BC, V9Y 7M8, Canada;
2 Swale Rock Marine Research, 3649 Place Road, Nanaimo, BC, V9T 1M9, Canada

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© 2014 Brouwer et al.

open-access license: This is an open access article distributed under the terms of the Creative Commons Attribution 4.0 International Public License (CC-BY 4.0), a copy of which is available at: This license permits unrestricted use, distribution, and reproduction in any medium, provided the original author and source are credited.

* Address correspondence to this author at Swale Rock Marine Research, 3649 Place Road, Nanaimo, V9T 1M9, B. C. Canada; Tel: 250-816-6726; Email:


We compared: 1) rearing mortality, 2) size at release (mean length), 3) jack, male and female sizes, and 4) jack, female, and adult returns of coho salmon (Oncorhynchus kisutch) from three consecutive brood years reared at the Nitinat River hatchery using a conventional or a semi-natural rearing method. The semi-natural method included feeding restrictions, shading of the rearing ponds, lower rearing temperature and rearing densities, exposure to a predator and a volitional release. We found no significant effects of brood year or rearing method on rearing mortality; it was significantly lower during the marking to release phase than during the other two phases (eyed-egg to ponding, ponding to marking). Conventionally reared smolts were significantly longer. Conventionally reared males were longer. As a proportion of number of smolts released, semi-natural rearing produced 86% fewer jacks, the same proportion of females and 15% more adults. Adult production trends, described as marine survival rate (returning adults • smolt-1) for Nitinat River Hatchery coho, and as ln recruits • female spawner-1 for a nearby wild coho population, were similar. Jacking rates were lower in Nitinat River hatchery coho than for the nearby wild coho population. We concluded that the semi-natural rearing methodology produces adult fish more efficiently than the conventional rearing method does, and at 73% of the cost.

Keywords: Hatcheries, production, salmon, semi-natural rearing, survival.