The neurobehavioural responses of fish exposed to ocean acidification (OA) are variable, possibly due to species-specific differences or involvement of multiple neuronal receptors. Here, we investigated behavioural responses of bicolor damselfish (Stegastes partitus) to OA and the involvement of dopamine receptors. Damselfish were exposed to control (pH 8.06; CO2 ~400 μatm) or OA (pH 7.73; CO2 ~1,000 μatm) seawater for five days, subjected to the open field, novel object approach, light/dark, and mirror-aggression tests, and returned to their respective aquaria. Two days later, tests were repeated upon treatment with the dopamine D1 receptor agonist SKF 38393. The D1 agonist, but not OA, altered locomotion in the open field test and boldness in the novel object approach test. Both the D1 agonist and OA increased anxiety-like behaviour in the light/dark test.

Video recordings were made with a FireWire 400 Colour Industrial Camera with a Tamron CCTV lens (2.8–12mm, f/1.4) Bicolor damselfish (Stegastes partitus) were ran through a battery of behavioural tests both in the absence and presence of selective D1 receptor agonist SKF 38393. Fish were gently netted from their tank and placed into the first test (open field). At the end of the test a novel object was added to the arena. Fish were then transferred to the light/dark test arena, then mirror/aggression test arena for the third and fourth tests, respectively. Two days later each fish was individually exposed to SKF 38393 and underwent the identical behavioural test battery. EthoVision motion tracking software system (v.10, Noldus, Leesburg, VA, USA) was used to record and quantify variables in each test.