During the time from when they are roughly long (roughly 5 to 9 years old), Nile crocodiles seem to have the broadest diet of any age range. They take more or less much the same small prey as smaller crocodiles, including insects and arachnids, but also take many small to medium-sized vertebrates and quickly become capable taking down prey up to their own weight. Fish become especially significant around this age and size. However, Cott (1961) found that the only size range where fish were numerically dominant over other types of food was from . This size range consists of subadult males and a mixture of subadult and adult females. In Lake Turkana, fish were the only food in the stomachs of 45.4% of the crocodiles that did not have empty stomachs, in total 87.8% of the crocodiles that did not have empty stomachs there had fish in their stomachs. Graham (1968) noted that throughout East Africa, crocodile diets are driven by the regional availability of prey. The arid land surrounding Lake Turkana is a relatively barren region for diverse or numerous prey other than fish, so fish are an exceptionally important food source to crocodiles there. In Lake Kyoga and Lake Kwana, 73.1% of the crocodiles that did not have empty stomachs had fish in their stomachs. At Lake St. Lucia in South Africa, many Nile crocodile congregate to feed on striped mullet ("Mugil cephalus") as they make their seaward migration for spawning. Here, the crocodiles may line up in dozens across narrow straits of the estuary to effectively force the mullet into easy striking distance, with no observed in-fighting among these crocodile feeding congregations. At this time of plenty (before irrigation operations by humans led St. Lucia to have dangerously high saline levels), a crocodile could expect to eat of mullet daily, an exceptionally large daily amount for a crocodile.