For the purposes of my study, it is important that I collect a sample of fish every month. This is to ensure that I will be able to detect changes in the condition of the gonads throughout the course of a year which will in turn help me to elucidate the breeding cycle of this species. Fish are collected once per month, using hand poles equipped with a size 16 limerick hook baited with frozen shrimp. Because these fish are carnivorous, they will take a baited hook.
I chose to use this method of collection because it is the least destructive method for collecting this species and also because of its efficiency. Collecting this way is highly species-specific, meaning that it targets O‘opu Akupa and can ensure that I will not be harming any other species of O‘opu that might be in the same stream. Other species of O‘opu that are common in lower-elevation streams where O‘opu Akupa are found are O‘opu Nakea and O‘opu Naniha. O‘opu Nakea is an omnivore, but prefers algae, and thus seldom takes a baited hook. O‘opu Naniha appears to be a detritivore and never takes a baited hook. Thus, by using hook and line as a collection method, I can ensure that I will not be catching any native fish that I am not targeting, and I can also return any O‘opu Akupa that I catch and do not need for my study. Because the limerick hooks are small and almost always hook the fish on the lip (rather than in the gut), fish can be returned to the stream with almost no damage, and will recover quickly.
After collecting a representative sample of fish (usually 10-12 fish per month), I euthanize the fish with a chemical called tricaine methanesulfonate (MS-222). This is considered the most humane method of sacrificing fish and is the method encouraged by the University of Hawaii Animal Care Committee. Once fish have been euthanized, I measure and record their standard length (length from the tip of the snout to the base of the caudal peduncle), and total length (length from the tip of the snout to the end of the caudal fin). I also record the sex of each fish by looking at the genital papillae, which is a flap of skin posterior to the anus. In males, this flap is pointed, whereas in females it is rounded. Fish are then preserved in formalin for dissection.
This male O'opu on the right was the largest specimen caught during the study. Please note the smaller, average size O'opu that was collected in the 2 gallon bucket below. Due to ethical reasons, this fish was released after carefully measuring the total length.
I have collected O'opu Akupa from the following streams:
Oahu
Nuuanu Stream 
Located in the middle of downtown Honolulu.
Kauai
Limahuli Stream
Located on the North shore of Kauai.
Hanamaulu Stream 
Located on the Eastern side of Kauai near Lihue.
Big Island of Hawaii
Wailoa river
Located along Hilo's Bay, this stream is situated between the airport and Hilo town.
Hakalau stream
Located along the Hamakua Coastline and about a 25 minute drive from the Hilo airport.