Spawning date of rainbow trout produced by fertilizing eggs from a summer-spawning line with cryopreserved milt from a winter-spawning line

Authors: Weber, Gregory - Greg; MARTIN, KYLE - Troutlodge, Inc; Palti, Yniv; Liu, Sixin; Beach, Joseph - Joe; Birkett, Jill

Submitted to: Aquaculture America Conference
Publication Type: Abstract Only
Publication Acceptance Date: 11/21/2022
Publication Date: 2/17/2023
Citation: Weber, G.M., Martin, K.E., Palti, Y., Liu, S., Beach, J.N., Birkett, J.E. 2023. Spawning date of rainbow trout produced by fertilizing eggs from a summer-spawning line with cryopreserved milt from a winter-spawning line. Aquaculture America Conference. p. 610.

Interpretive Summary:

Technical Abstract: Rainbow trout lines selected to produce gametes at different times of the year and commercial cryopreservation services for rainbow trout semen provide an opportunity for extending the availability of gametes. Nevertheless, little data are available on the effect of crossing fish with different spawning dates on the spawning date of the offspring. Egg lots from females ovulated in August were divided in half and fertilized with milt from males from the same population (‘purebred’) or cryopreserved milt from two males from a winter-spawning population, collected in February (‘hybrid’). Five crosses or families were made for each group and a total of 343 females from the purebred group and 244 females from the hybrid group were observed for spawn date. The spawning windows of both the purebred and hybrid groups lasted around three months. In addition, each family took about nine weeks for the middle 10-90% of the individual females to ovulate. However, whereas 50% of the purebred fish had ovulated by the end of August, spawning of the hybrid progeny peaked in November, on average about 10 weeks after the purebred families. Furthermore, there was little overlap in the spawn dates between the purebred and hybrid females indicating they are two distinct egg producing populations. The hybrid progeny did not spawn in May which is also midway between February and August. The hybrids exhibited a classic phenotypic distribution pattern of heterozygous F1 hybrids. These results support hybridization of lines with different spawn dates by using cryopreserved sperm enables valuable strategies for maximizing hatchery production of year-round seedstock, and for quantitative trait loci (QTL) mapping of spawning date in rainbow trout. The F1 hybrids were crossed to produce an F2 generation for future genetic analysis to map QTL for spawning date.