I'm not too sure about a short life span...Most fish that have such a span are usually rather fast growers and I have not seen this with scombs,unless they are an exception?
Scombs have a very short life span, but they are also a fairly small fish. I consider a scomb to be mature at eight inches, and it would only take the fish about six to eight months to get there.
Let's compare that to the North American rock bass. Rock bass, like scombs, are sexually mature at about seven inches. Like scombs, their normal adult size is seven to ten inches. Like scombs, an exceptional specimen will reach about 15 inches. Unlike scomberoides, a yoy rocky will take
three years to reach seven inches! A 3" yoy scomb will see seven inches in about 6-8 months
with a proper, nutritious diet. That means balanced, quality food. Some may have quick growth even with fatty, thiaminase infested cyprinids such as goldfish or rosies, but good pellets or filets will always be better.
But I digress. My point is, quite simply, scombs are very fast to mature fish, but this doesn't mean that they have to be fast growers. They don't get nearly as large as Hepsetus odoe, and therefore their growth rate will not match it. However, they do grow fast enough that they can reach sexual maturity before their first winter, and can breed twice or more in their natural life span.