All experiments were approved by the University of Hawaii’s Institutional Animal Care & Use Committee (IACUC) under protocol #1045. For determination of growth, larval Amphiprion ocellaris were euthanized using a solution of 0.06 g/ml Ethyl 3-aminobenzoate methanesulfonate salt (MS222) (Sigma-Aldrich Inc., Saint Louis, MO, USA; catalog no. A5040-25G), preserved in a solution of 5% formalin in seawater, and measured for total length and jaw size within one week of fixation.
Behavioral observations were made of predator-prey interactions between larval fish and copepod prey under conditions that were similar to the feeding conditions in the rearing tank in terms of prey numbers and fish density. For each trial, 10 A. ocellaris larvae were transferred from the rearing tank into the observation chamber (18 x 18 x 10 cm aquarium made of Plexiglas) filled with 3 L of filtered seawater (Whatman filters, GF/C). The fish larvae were allowed to acclimate for 15 minutes, before adding the 3000 prey. Each experimental trial lasted for 60 minutes and prey densities declined by 25% or less during this time. During the trial, a CCTV video camera (Panasonic Corporation, Kadoma, Osaka, Japan; model WV-BP310) equipped with a Nikkor 50 mm lens (Nikon Corporation, Shinjuku, Tokyo, Japan; model 1433) recorded continuously and stored the recording on a digital high definition videocassette recorder (Sony Corporation, Minato, Tokyo, Japan; model GV-HD700). The camera lens was positioned 0.3 m from the observation chamber and the lens was focused in a plane at the center such that the field of view was 4 cm2. The container was uniformly illuminated from above with one 20-watt fluorescent light providing 1,900 lumens of light.
Two separate experimental series were completed: the first one focused on three larval fish ages (1, 3, and 10 dph), and offered a single prey type per experiment (nauplii, copepodites or adults). The second one recorded predatory-prey interactions for larval ages 1 to 14 dph and mixed prey fields (nauplii + copepodites + adults). Capture success was determined from video recordings of predatory interactions between larval clownfish and three developmental stage groups of the copepod Parvocalanus crassirostris.