This new study identifies two genes in Nile tilapia related to the expression of stress in crowded environments: sstl and fosab. This is good news for breeders as it might be possible to selectively breed fish that perform better under crowded conditions.
Figure 1. Experimental set up for mirror image stimulation used to assess aggression in Nile tilapia
Aquaculture has been aiming towards intensification – grow more with less. In the case of fish farming, this involves more fish in less space, with less water, and less feed. This requires careful selection of species and individuals that will perform well in crowded environments. Fish domestication changes social behaviour and aggression is one of the key behaviours in crowded spaces. In the case of Nile tilapia high stocking density causes a shift from antagonistic (aggressive) to shoaling behaviour.
Our hypothesis was that rearing density would influence the frequency of aggression – individuals with different aggression levels and stress‐coping styles would differ in the expression of key genes involved in the stress response. We concluded that the crowding inhibits aggressive behaviour in Nile tilapia and results in changes in the expression of stress-related genes that accompany the shift from social hierarchies maintained by agonistic interactions at low density, to shoaling at high density.
D. Rodriguez-Barreto, O. Rey, T. Uren Webster, G. Castaldo, S. Consuegra, C. Garcia de Leaniz, Transcriptomic response to aquaculture intensification in Nile tilapia, (2019). doi:10.6084/m9.figshare.8198408.v1.
The full paper can be found here https://onlinelibrary.wiley.com/doi/full/10.1111/eva.12830
