Identification of families for F2 individuals and investigation of reproductive bias
The results of the estimations of GG or UANN relationships were combined to identify the families to which each F2 individual belonged. To identify the family, we also indirectly used the FS relationships between F2 individuals. For example, if a GG relationship is estimated between F0 individual A and F2 individual B, and an FS is estimated between F2 individual B and F2 individual C, then individual A and individual C are also considered to have a GG relationship, even if a GG relationship is not detected between A and C..
To test the significance of reproductive bias, we performed Pearson’s\(\chi\)-square goodness-of-fit tests with the null hypothesis that all families contributed equally to breeding regardless of the number of F1 individuals released, i.e., each family was responsible for the birth of an equal number of F2individuals.
The families taken into consideration were determined based on the F1 birth year and release status. Table S3 shows the number of F1 individuals released from each family from spring 2017, when releases to the NN6 pool began, to spring 2019, when all individuals that could have contributed to the birth of the 2019 year-group had been released. Here, only three F1groups—A1, A2, and A3—born at the facility in 2016 and released in spring of 2017 and 2018, could be the parents of the 2018 year-group. This is because age at first maturity of T. ichikawai is 2 years old or later. In addition, individuals listed as spring releases were released around May, just before the June–July breeding season of this species, so individuals released in the spring of 2018 may have also contributed to the birth of the 2018 year-group. In the same way, the families that could be parents of the 2019 year-group are the A1, A2, and A3 groups released in spring of 2017, 2018, and 2019, and the A4, A5, and A6A7A9 groups, born at the facility in 2017 and released in fall 2017, spring 2018, and spring 2019, for a total of six groups. Although the possibility of their reproducing is unlikely, the A10, A11, A12, A15, A16, and A17 families were also included in the analysis as they were released at the same location.