DOI: 10.5061/dryad.nvx0k6dt4
title: Sizes of steelhead families raised in hatchery tanks vs in artificial streams

description: Salmonid fish raised in hatcheries often have lower fitness (number of
 returning adult offspring) than wild fish when both spawn in the wild.
 Body size at release from hatcheries is positively correlated with
 survival at sea. So one explanation for reduced fitness is that hatcheries
 inadvertently select for trait values that enhance growth rate under the
 unnatural environment of a hatchery, but that are maladaptive in the wild
 environment. A simple prediction of this hypothesis is that juveniles of
 hatchery origin should grow more quickly than fish of wild origin under
 hatchery conditions, but should have lower survival under wild conditions.
 We tested that hypothesis using multiple full sibling families of
 steelhead (Oncorhynchus mykiss) that were spawned using either two wild
 parents (WxW) or two first-generation hatchery (HxH) parents. Offspring
 from all the families were grown together under hatchery conditions and
 under semi-natural conditions in artificial streams. HxH families grew
 significantly faster in the hatchery, but had significantly lower survival
 in the streams. That we see this tradeoff after only a single generation
 of selection suggests that the traits involved are under very strong
 selection. We also considered one possible alteration to the hatchery
 environment that might reduce the intensity of selection among families in
 size at release. Here we tested whether reducing the fat content of
 hatchery feed would reduce the variance among families in body size.
 Although fish raised under a low-fat diet were slightly smaller, the
 variation among families in final size was unchanged. Thus, there is no
 evidence that reducing the fat content of hatchery feed would reduce the
 opportunity for selection among families on size at release.
description: Full sibling families of fry were pooled together and raised in
 400 L tanks, or in artificial streams at a research hatchery.  These
 datasets provide family average growth to compare with family survival,
 and the individual growth data.
description: File
 'Family_survival___family_Avg_size' contains average sizes of
 families of steelhead raised under hatchery conditions at Oregon State
 University's Aquatic Animal Health lab in 2017.  Tanks were fed
 either a high-fat diet or a low-fat diet.  The families were pooled
 together in each tank, and then were sorted out at the end of the
 experiment via DNA genotyping. The same families were also pooled and
 released into artificial streams at the Oregon Hatchery Research Center.
 The file also contains counts of survivors from each family out of 120
 fish per family put into the artificial streams.  Column names are: DIET = high fat or low fat
 diet FISH-TYPE =
 offspring of a cross between two wild fish (WxW) or two
 1<sup>st</sup>-generation hatchery fish (HxH) FAMILY = the family
 identity AVGFAMSIZE = the average fork
 length of each family SURVIVAL(COUNT) = number of
 survivors per family out of 120   File
 'Sizes_of_indiv_fish_in_tanks' contains the individual sizes
 (fork length) of each fish from each tank in the hatchery. Column names are: TREATMENT = high or low fat food
 for each tank TANK = tank identification
 number.  SUB-TANK
 = each tank was divided into two tanks half way through the growth
 period.  Sub-tank is the name of the tanks after they were
 split. INDIV =
 individual ID for each fish LENGTH = fork length
 FAMILY = family
 ORIGIN = same as fish-type
 above (offspring of a cross between two wild fish (WxW) or two
 1<sup>st</sup>-generation hatchery fish (HxH))