Table 5.

Laboratory studies that have provided evidence for genetic changes or that found no evidence of genetic changes in phenotypic traits between hatchery-reared and wild populations of salmonid fishes.

H origin	Artificial selection?	Program	Hatchery gens.a	Species	Trait	Change	Other comments and/or caveats	Reference
Local	No	S	1	Chinook salmon	Predator avoidance	H<W	2.2% reduction in survival	Fritts et al. (2007)
Localb	No	S/H	4–7	Rainbow trout	Predator avoidance	H<W	16.3–28.9% reduction in survival	Berejikian (1995)
Local	No	S/H	5	Brown trout	Antipredator response	H<W		Ferno and Jarvi (1998)
Local	No	S/H	>5c	Brown trout	Antipredator response	H<W		Johnsson et al. (1996)
Local	No	S	1	Chinook salmon	Aggression	0	Large number of comparisons (n = 97 to 276, depending on the type of competition)	Pearsons et al. (2007)
Local	No	S/H	>5c	Brown trout	Aggression	0	Large number of comparisons (n = 287)	Johnsson et al. (1996)
Localb	No	S/H	4–7	Rainbow trout	Aggression	H> <Wd		Berejikian et al. (1996)
Local	No	S/H	>5c	Brown trout	Juvenile growth rate	H>W		Johnsson et al. (1996)
Local	No	S	0	Rainbow trout	Length/weight	H>W	Not reared under common conditions	Kostow (2004)
					Variance in length/weight	H<W	Not reared under common conditions
					Variance in age	H<W	Not reared under common conditions
Local	No	S	4–6e	Chinook salmon	Female egg size	H<W	Egg size reduction in two populations with considerable supplementation (28–43%); no change in egg size in two other populations with low supplementation (4–16%)	Heath et al. (2003)
							Genetic effects were not disentangled from environmental effects on egg size	(see Beacham 2003; Fleming et al. 2003)
Local	No	S	1	Brown trout	Juvenile growth rate	H>W	Differences were small	Dahl et al. (2006)
Local	No	S/H	<1f	Brown trout	Antipredator response	H<W	Not reared under common conditions	Dellefors and Johnsson (1995)
Local	No	S/H	>25g	Coho salmon	Aggression	H>W	Not reared under common conditions	Rhodes and Quinn (1998)
Local	Yes	H	>10h	Brook trout	Juvenile growth rate	H>W	Hatchery fish were selected for growth	Vincent (1960)
Local	Yes	H	>10h	Brook trout	Wariness	H<W	Hatchery fish were selected for growth	Vincent (1960)
Locali	Yes	F	5–7	Atlantic salmon	Antipredator response	H<W	Hatchery fish were farmed	Johnsson et al. (2001)
Local	Yes	F	1	Atlantic salmon	Body morphology	H≠W	Hatchery fish were farmed	Fleming et al. (1994)
Nonlocal	No	S	4–5j	Coho salmon	Body morphology	H≠W	Hatchery fish: smaller heads, more streamlined bodies Different ancestral origin of hatchery fish	Swain et al. (1991)
Nonlocal	No	S	2–3k	Rainbow trout	Adult body size	H>W	Inadvertent selection of larger body size	McLean et al. (2005)
Nonlocal	No	S	2–3k	Rainbow trout	Adult run-timing	H≠W	Inadvertent selection of earlier-run timing females for fulfilling hatchery recruitment requirements	McLean et al. (2005)
Nonlocal	No	S	?	Atlantic salmon	Juvenile growth rate	H>W		Kallio-Nyberg and Koljonen (1997)
Nonlocal	No	S	4–5j	Coho salmon	Aggression	H>W		Swain and Riddell (1990)
Nonlocal	No	H	?	Atlantic salmon	Aggression	H<W		Norman (1987)
Nonlocal	No	H	?	Brook trout	Aggression	H>W		Moyle (1969)
Nonlocal	No	S/H	1–2	Brown trout	Antipredator response	H<W	Not reared under common conditions	Alvarez and Nicieza (2003)
Nonlocal	No	S/H	1	Coho salmon	Male spawning performance	H<W	Not reared under common conditions	Fleming and Gross (1993)
Nonlocal	No	S	?	Chinook salmon	Male spawning performance	H<W	Not reared under common conditions	Chebanov and Riddell (1998)
Nonlocal	No	S	?	Chinook salmon	Female spawning performance	H<W	Not reared under common conditions	Chebanov and Riddell (1998)
Nonlocal	Yes	F	5–7	Atlantic salmon	Male spawning performance	H<W	Not reared under common conditions	Fleming et al. (2000)
Nonlocal	Yes	S/H	>5	Rainbow trout	Antipredator response	H<W	Hatchery fish were selected for growth	Johnsson and Abrahams (1991)
Nonlocal	Yes	S	>15l	Masu salmon	Antipredator response	H<W	Chemically simulated predator attack	Yamamoto and Reinhardt (2003)
Nonlocal	Yes	F	5–7	Atlantic salmon	Antipredator response	H<W	Hatchery fish were farmed	Einum and Fleming (1997)
Nonlocal	Yes	F	5–7	Atlantic salmon	Antipredator response	H<W	Hatchery fish were farmed	Fleming and Einum (1997)
Nonlocal	Yes	F	4–7	Atlantic salmon	Juvenile growth rate	H>W	Hatchery fish were farmed	McGinnity et al. (2003)
Nonlocal	Yes	S	>15l	Masu salmon	Juvenile growth rate	H>W	Hatchery fish were selected for growth	Yamamoto and Reinhardt (2003)
Nonlocal	Yes	S	>15l	Masu salmon	Aggression	0	Hatchery fish were selected for growth	Yamamoto and Reinhardt (2003)

Hatchery and wild populations were compared under common environmental conditions, unless otherwise noted. Statistical significance was based on P < 0.05, unless otherwise noted.

Program type: S, supplementation; C, captive-breeding; H, harvest augmentation; F, farmed/aquaculture. H<W, hatchery population showed reduced aggression/antipredator response/predator avoidance/growth rate/egg size etc. relative to the wild population; H>W, hatchery population showed greater aggression/antipredator response/predator avoidance/growth rate/egg size etc. relative to the wild population; H≠W, hatchery population shifted in other traits from the wild population (details of the main shifts provided); 0, no change observed; ?, not presented or with insufficient detail.

^aHatchery generations refer to the number of generations in which the hatchery program involving a local or nonlocal hatchery population had taken place at the time the study was conducted. Note, however, that the hatchery programs themselves might differ. In some cases, naturally-spawning adults are collected from the wild; their offspring are raised in hatcheries for a period of time and then released back into the wild. In other cases, particularly traditional hatchery programs, hatchery fish are regenerated from captive broodstock that were maintained solely in hatcheries. Particularly for older hatchery programs (i.e., more generations), details regarding whether the latter was involved were not always clear.

^bHatchery population originated from a wild population that was very geographically close to the wild population used in comparisons. The authors acknowledge that the existence of genetically distinct subpopulations within the same drainage system might have been a confounding effect for their comparison of hatchery and wild steelhead (Berejikian 1995; Berejikian et al. 1996)

^cBased on a generation time of 3.8 years for anadromous brown trout.

^dDirection of change depended on age. Newly emergent fry: H<W; 105 days postemergence: H>W.

^eBased on a generation time of 3.0 years for Chinook salmon.

^fNot stated in the article how long hatchery fish have been generated for this river. However, in this study, the important aspect was the comparison between some fish born and reared in the hatchery and those that had wild exposure for the first 1+ year of life (see Dellefors and Johnsson 1995).

^gBased on 100 years of hatchery propagation on the same wild population.

^hBased on a generation time of 3.0 years for brook trout.

ⁱAuthors acknowledge that the farmed strain was derived principally from the same wild population where comparisons were being made.

^jHatchery populations had been established for four to five generations for five of six hatchery populations, and two generations in one case.

^kBased on a generation time of 3.0 years for anadromous steelhead.

^lBased on a 2-year generation time for this masu salmon population (Yamamoto and Reinhardt 2003).