One of the projects I have been working on is a program that looks at the way the hobby handles conservation priority species, and asks the tough questions about whether we are handling them correctly or not. I am most concerned with the need to preserve the genetic resource in a species. My research landed me ultimately within the aquaculture science industry, where researches are light years ahead of the aquarium hobby when it comes to breeding fish and getting the most benefit out of limited breeding stocks. There are a LOT of things to take a hard look at, and I want to have these discussions in our club. I am going to start one of these 'something to think about' threads periodically with one of the changes that I believe needs to happen in the hobby. Some of them will overlap. Some will make immediate sense. Others take some effort to wrap your head around. Some are easy changes, and others will make you question the validity of hobby conservation at all. But they are things we need to look at, as fish breeders, if we are serious about species maintenance. Topic 1: Breeding with even sex ratios There is a tool in aquaculture known as the 'effective breeding number' (N), which is a calculation that predicts the number of fish in a breeding population that are actually useful. The only fish that count in the number are the males and females that actually produce fry. The larger the N value the better to prevent a bad situation called genetic erosion. Lots of things go into genetic erosion (inbreeding being a big reason), but that is a discussion for another thread. It is hard to put a calculation in this forum, so I will spell it out: Effective Breeding Number (N) = 4(# males)(# females) (# males) + (# females) In this calculation only the males and females that produce fry count. The highest the N value can be is the total number of fish in the population, and it will only get to be that large if the sex ratio is even. Example 1: Uneven sex ratio 2 males 10 females (like a colony of cichlids) 4(2 males)(10 females) (2 males) + (10 females) 80 / 12 = 6.67 This means that even though there are 12 fish in the breeding pool, the effect on the genetic health of the population is as if there were only 6 or 7 fish in the breeding pool. This is because half of the genes in the offspring are only coming from two fish. Example 2: even sex ratio 10 males 10 females 4(10)(10) 10 + 10 400 / 20 = 20 So when the sex ratios are even the effective breeding number goes up to the actual population. OK... this is an ideal situation where all of the fish are spawning. This may work with livebearers, cory cats, danios and other fish that do not get dominant males that kill each other... but in even sex ratios in mbuna tank will not result in all the fish breeding. Only the dominant males will spawn. Or is that really true? Maybe so in a 55 gallon tank, but the opposite has been demonstrated in aquaculture. Take a population of 100 Psuedotropheus demasoni, with an even sex ratio (50 of each), put them in a 2000 gallon pond or vat and watch what happens. Given the space and numbers, dominance changes. A male that is breeding today may not be breeding tomorrow. Ten males may have breeding stations set up all at the same time, and a breeding female may spawn with more than one of them in a single session... literally laying ten eggs with one male, five with another, ten more with a third and so on until she is done. Can this dynamic even be attempted in an aquarium situation? Is there a way to create a breeding population of, for example, 20 fish in an even sex ratio with all ten males bringing sperm to the party? I know there is a way. More than one... but let's see what we can come up with as a group.