3. Results
Figure 1a shows the bimodal size distribution of the 518 juveniles that
could be caught from the wild. As expected, the random sample of 375
juveniles that was genotyped for parental assignment did not
significantly differ in body lengths from the non-genotyped fish
(Welch’s F = 1.7, p = 0.19). In total 301 (80.3%) of these 375
wild-caught juveniles could be assigned to 56 of the 60 experimental sib
groups. Their average (± SD) body lengths and weights were 95.6 ± 10.6
mm and 11.3 ± 3.9 g, respectively, and were always below the 125 mm that
the Bayesian mixture model had identified as upper size for 0+ fish
(Fig. 1b). All but one of them could be genetically sexed. The overall
male ratio was 48.3% and not significantly biased (χ2 = 0.33, p = 0.56).
The Bayesian model identified 57 of the remaining 74 genotyped fish as
wild-born 0+ juveniles and the larger ones as 1+ or older (Fig. 1b). The
wild-born 0+ were on average 17.6 mm smaller than the experimentally
bred 0+ (Fig. 1b; F = 122.5, p < 0.001). Among the
experimentally bred 0+, males were on average 2.6 mm larger than females
(F = 4.4, p = 0.03; Fig. 1b). Among the wild-born 0+, males were on
average 3.0 mm larger than females, which was in this smaller sample not
statistically significant (F = 1.6, p = 0.21). However, the wild-born 0+
had a male-based sex ratio (63.2% males) that was not observed in the
experimentally bred 0+ (χ2 = 4.3, p = 0.04; Fig. 1c).
We obtained 47 kinship coefficients (mean ± SD = -0.0003 ± 0.04). One
full-sib family with a kinship coefficient of 0.226 was classified as
outlier (because »3 SDs away from the mean, following the three-sigma
rule) and excluded from all further analyses, leaving 251 genetically
sexed juveniles of 46 full-sib families for the final analyses. The
kinship coefficients of these sib groups could partly be predicted by
the parental inbreeding coefficients: Higher parental inbreeding
coefficients led to higher average kinship coefficients among their
offspring (rs = 0.61, n = 20, p = 0.004; Supplementary
Figure S1).
The body sizes of female juveniles declined with increased kinship
coefficients, while the body sizes of male juveniles did not seem to be
affected (Figure 2; Table 1; Supplementary Figure S2; Supplementary
Table S1). Juvenile body size also varied among maternal but not
paternal sib groups (Table 1).
The recapture rates per full-sib family, i.e., the mean number of
recovered juveniles per number of released larvae, varied between 0.0
and 0.68 and were not correlated with the kinship coefficients
(rs = 0.13, n= 48, p = 0.38) nor with the inbreeding
coefficients of the dams (rs = 0.39, n= 11, p = 0.23) or
the sires (rs = 0.05, n= 9, p = 0.90).
The number of recovered juveniles per experimental sib group that was
represented in our sample varied from 1 to 17 (mean = 5.3, SD = 3.1),
i.e., sex ratios per individual family could mostly not be determined
due to low N. However, the number of recovered juveniles per dam varied
from 5 and 52 (mean = 24.3, SD = 10.6). Family sex ratio differed among
the maternal sib groups (χ 2 = 22.5, d.f. = 11, p =
0.02) but could not be predicted by maternal inbreeding coefficients
(rs = -0.19, p = 0.57) nor the average kinship per
maternal sib group (rs = 0.30, p = 0.37). The number of
recovered juveniles per sire varied from 17 to 51 (mean = 29.2, SD =
10.6). Family sex ratio did not differ among the paternal sib groups (χ2 = 10.8, d.f. = 9, p = 0.29) and was not correlated
with paternal inbreeding coefficients (rs = 0.65, p =
0.06) or average kinship per paternal sib group (rs =
0.37, p = 0.33).