The Fourth International Stock Enhancement & Searanching

Poster Abstract

3. THREE STRATEGIES TO MINIMIZE GENETIC LOSSES IN ENHANCEMENT PROGRAMS


Blanco Gonzalez1, Tetsuya Umino2, Nobuhiko Taniguchi1,
1 The Research Institute of Marine Bioresources, Fukuyama University, 452-10 Innoshima-Ohama, Onomichi 722-2101, Japan
2 Graduate School of Biosphere Science, Hiroshima University, 1-4-4 Kagamiyama, Higashi-Hiroshima 739-8528, Japan

The limited number of breeders kept in the hatcheries represents a cornerstone in managing stock enhancement and restocking programs. Most of the programs conducted on marine finfish use 50-200 specimens as broodstock. However, the differential contribution among them reduces the effective number of breeders (Nb), leading to a reduction in the genetic variability. In this paper, we introduce three strategies adopted in two different black sea bream (Acanthopagrus schlegelii) broodstocks used for stock enhancement. The first mean involves increasing the number of breeders. Results obtained keeping different numbers of breeders were compared. Secondly, we evaluated the improvements achieved collecting the eggs at different timings. This strategy confirmed the differential contribution among parental fish and enabled identifying minor contributors. A simplified protocol to reduce egg collection and tedious rearing procedures is also presented. Hence, it can be a promising tool to increase Nb, minimize the undesired loss of genetic variability and improve offspring fitness. Finally, genetic relationships among breeders was assessed and compared to those of the offspring before and after the release (Fig. 1). The post-release sample was genetically closer to the broodstock that produced juveniles for stocking than to the native wild population. The posterior genetic analysis evidenced the close relationships among specimens. In summary, the adoption of these three strategies has shown promising results to minimize deleterious genetic effects in black sea bream and we encourage testing their usefulness in other species.
Fig. 1. Post-release black sea bream genotype probability for assignment to putative parental baselines (wild pre-release and broodstock) plotted on a log scale.