Larger fish, like catfish and freshwater bass, are preferred by adults more than in length. Particularly small fish are likely to be eaten only in case of sudden encounter, mostly in shallow, dry-season ponds where not much effort is needed to catch the small, agile prey. Most observed fishing by crocodiles takes place in waters less than deep and fish are often caught when they swim into contact with the crocodile's head, even literally right into the reptile's mouth. Across much of their range, they take any fish they encounter, but largish and relatively sluggish mesopredator fish such as lungfish and "Barbus" carp seem to be most widely reported. Many other genera are taken widely and relatively regularly, including "Tilapia" (which was the most significant prey genus in Lake Turkana), "Clarias", "Haplochromis", and "Mormyrus". In Uganda and Zambia, lungfish comprised nearly two-thirds of the piscivorian diet for crocodiles. Similarly, in Lake Baringo, the lungfish is the crocodile's main prey and the crocodile is the lungfish's primary predator. In the Okavango Delta, the African pikes ("Hepsetus" spp.) were the leading prey group for subadults, comprising more than a fourth of the diet. Extremely large fish, such as Nile perch ("Lates niloticus"), goliath tigerfish ("Hydrocynus goliath"), and even sharks, are taken on occasion, in addition to big catfish, such as "Bagrus" spp. and "Clarias gariepinus", which are preyed upon quite regularly in areas where they are common. In the Zambezi River and Lake St. Lucia, Nile crocodiles have been known to prey on bull sharks ("Carcharhinus leucas") and sand tiger sharks ("Carcharias taurus"). The largest fishes attacked in such cases may potentially weigh more than .