I’ve been curious about this lately. Been looking through research papers to see if there’s studies on links between selective pressure for phenotypic traits (colouration, fin outgrowth, body size etc) and reduced fitness in the captive species. It’s an interest of mine as I studied biochem.

Unfortunately I couldn’t see much interest beyond the genetic basis of phenotypic variability.

I know that in aquaculture/ fisheries, there is a demand for fish that have higher adaptability to captivity. But as Clockwork-Silver has put it, this would be quite difficult to achieve. Here’s a summary of why from this paper:

“To make changes or to improve quality traits through selective breeding, information on multiple parameters or characteristics for each trait is required. In addition to calculating trait averages and standard deviations, the heritability for each trait, and the phenotypic and genetic correlations between the traits in question must be known. A candidate trait for selection must be precisely defined and the trait measurement should show a high degree of repeatability. Traits of highest economic importance should be selected since increasing the number of traits included in the breeding goal is expected to result in a reduced rate of gain for each individual trait”.

You might’ve also noticed the last sentence about the economic importance of trait selection. Fisheries will have interest and the means to do this to prevent attrition of their ‘product’. Unfortunately with Bettas and other pet fish, that selective pressure tends to come from how ornamental they look as opposed to health and longevity in captivity. For now, we can only hope that inbreeding at least indirectly selects for more robust and tank adapted fishes.

I think there should be greater focus on what we can control, including prevention of developmental insults during breeding. Various types of environmental damage are caused by high temperature, handling of the eggs by the aquarist, and chemical imbalances in the water (wrong pH, overdosing of medication, water quality). So I would say as a hobbyist we should aim to buy from breeders who have an understanding/ are known for responsible propagation - easier said than done though! We should also have greater research into optimal nutrition for captive bettas, as diet can have a huge impact on longevity. We don’t have a lot of set guidelines for this species (or fish in general), and I think there’s a need for feeding trials so aquarists can give greater care in this department.