Standard Talk (15 mins) Australian Society for Fish Biology Conference 2022

Diel behaviour change and ontogenetic shifts of vagrant coral reef fish (#163)

Alexander Rigg 1 , William Knoke 1 , Lucas Djurichkovic 1 , Clara Bellotto 1 , David Booth 1
  1. Uts, Sydney, NSW, Australia

Coral reef fish expatriated to temperate receiving areas (vagrants) are subjected to suboptimal conditions that impact physiological performance and behaviour. Little is known about the ontogeny of vagrant fish, especially as they mature into the austral autumn and winter. This lab study evaluated diel patterns of behaviour and physiological performance of two size classes of common vagrant, A. vaigiensis (sergeant major damselfish). Fish were filmed at morning, midday, afternoon, and night (infrared camera at night) and were exposed to the following treatments: normal, plus food, plus simulated predator, and post-predator. The behavioural characteristics (alertness, water column position, aggressiveness, area of shoal, activity, and habitat usage) and performance (burst speed and bite rate) were quantified at each treatment. Preliminary findings show larger fish were more reliant on habitat through all treatments, whilst smaller fish relied on shoaling mechanisms. Smaller fish had a higher bite rate and schooled at a higher volume when feeding compared to larger fish, but a difference occurred in the morning, where larger fish had an increased bite rate. The latency from the predator response followed a similar trend across all treatments, but larger fish recovered sooner, demonstrated by high activity levels and an increased area use after the predator simulation. Larger fish used the upper part of the water column at night under normal conditions and feeding, and smaller fish showed signs of stress by abrupt swimming and decreased area being utilised. This study highlights the shifts that occur as vagrant fish mature in novel ecosystems and the behaviours that underpin ontogeny. Understanding of vagrant fish and the mechanisms that drive ontogeny will play an important role in assessing the impacts of invasive fish in temperate marine ecosystems under climate change.