The 'o'opu was a fish relished by the people in the old days. The 'o'opu 'akupa, nakea, and nopili, as well as the hinana (the fry or juvenile fish) were all eaten. The 'o'opu alamo'o was returned to the rivers as it was considered bad luck to eat by fishermen. The 'akupa and naniha 'o'opu have been observed in the waters of Hamakua.

It was usually women who fished for 'o'opu, but men did carry out this job at times. 'O'opu were caught by hand, by woven fish traps, and with small baited fishing poles.

Here is another 'o'opu fishing technique: When big rains came and the streams were swollen with high waters, 'o'opu would leave their holes to escape from the dirty water. It was at these times that men built a dam across the river to divert the clean upper layer. The 'o'opu would rise from the dirty water behind the dam and spill over to a large grass free area where they were easily caught.

In ancient times 'o'opu were found in fishponds, wetland taro patches (lo'i), rivers and all sorts of clear freshwater ponds, but the very young hinana need saltwater to survive. 'O'opu are fat in the Hawaiian lunar month of Welo (around April). The 'o'opu nakea and 'akupa lay their eggs between the months of Mahoemua and Welehu (roughly corresponding to the period of August to November). The 'o'opu alamo'o lays its eggs all year round.

Ka i'a ka welelau o ke ahi "The fish at the top edge of the fire" An ancient proverb refering to the lawalu method of cooking 'o'opu. 'O'opu were cooked in lawalu style (wrapped in ti leaves and set amongst the embers of a fire which has burnt down), eaten raw, or dried. It is said that in ancient times the 'o'opu of Kawainui was tame and did not flee when a person tried to grasp it. It gave itself up. It would have been the same for the 'o'opu of Hamakua.