A large predatory reef fish species moderates feeding and activity patterns in response to seasonal and latitudinal temperature variation

Molly Scott,Andrew Tobin,Morgan Pratchett,Michelle Heupel

doi:10.1038/s41598-017-13277-4

Abstract

Climate-driven increases in ocean temperatures are expected to affect the metabolic requirements of marine species substantially. To mitigate the impacts of increasing temperatures in the short-term, it may be necessary for ectothermic organisms to alter their foraging behaviour and activity. Herein, we investigate seasonal variation in foraging behaviour and activity of latitudinally distinct populations of a large coral reef predator, the common coral trout, Plectropomus leopardus, from the Great Barrier Reef, Australia. P. leopardus exhibited increased foraging frequency in summer versus winter time, irrespective of latitude, however, foraging frequency substantially declined at water temperatures >30 °C. Foraging frequency also decreased with body size but there was no interaction with temperature. Activity patterns were directly correlated with water temperature; during summer, the low-latitude population of P. leopardus spent up to 62% of their time inactive, compared with 43% for the high-latitude population. The impact of water temperature on activity patterns was greatest for larger individuals. These results show that P. leopardus moderate their foraging behaviour and activity according to changes in ambient temperatures. It seems likely that increasing ocean temperatures may impose significant constraints on the capacity of large-bodied fishes to obtain sufficient prey resources while simultaneously conserving energy.

Highlights

Sustained and ongoing ocean warming[1], is exposing marine organisms to unprecedented and ever-increasing temperatures
For common coral trout (Plectropomus leopardus), there does not appear to be any difference in thermal sensitivity, between fish sampled from latitudinally distinct locations where average maximum summer temperatures differ by up to 3 °C31
In situ observations of foraging behaviour and activity were undertaken for P. leopardus in summer (February– March 2016) and winter (July–August 2016) at Lizard Island (14°40′S, 145°27′E) in the northern Great Barrier Reef (GBR) and Heron Island (23°29′S, 151°52E) in the southern GBR

Summary

Introduction

Sustained and ongoing ocean warming[1], is exposing marine organisms to unprecedented and ever-increasing temperatures. Temperate waters regularly vary up to 10 °C annually[25] This means that for coral reef species, small increases in ambient water temperature may subject individuals and populations to unprecedented temperatures, leading to a greater energetic cost of maintaining standard metabolic activity[26,27]. For common coral trout (Plectropomus leopardus), there does not appear to be any difference in thermal sensitivity (i.e. sensitivity to variations in water temperatures), between fish sampled from latitudinally distinct locations where average maximum summer temperatures differ by up to 3 °C31 Individuals from both populations exhibited declines in performance when subjected to water temperatures >30 °C10,32. P. leopardus may compensate for temperature-induced increases in metabolism by modifying their food intake[11], provided food is not limited by prey availability or abundance[34], and through a reduction in swimming activity[10]

Methods

Results

Conclusion