Number of fish is from birth rate minus death. High birth strategies outpace death from imperfect care. Can try separating the eggs and replacing nutrition from cannibalism with unfertilized eggs. Fish brought to our estate seemed to do fine without many casualties or constant replacement, despite very different environment and likely little prior experience from piscinists raising koi outside Kiri. They are here taking care of the fish, observable. Do not think Tsunade will be necessary for normal care, only reviving dead eggs on another Path, which may not even be possible with modern science. How many years were spent on domestication? Bad care for too long would make an extinct