Not breeding any fish under 15 can also result in problems because you then effectively exclude the two salt fish. The best would be to artificially select the largest and most healthiest fish from each years returns. Not hard to do these days with scale samples. Only problem is that the department is too lazy to do it. There are other means of artificially selecting also that would require less work. Using native broodstock is one of the easiest if there are adequate numbers of wild fish for that. But there are also other cost-effective methods not being employed.