Latitudinal and seasonal variation in space use by a large, predatory reef fish,Plectropomus leopardus

Abstract

Temperature directly affects the metabolic rate and resource requirements of ectothermic animals, which is likely to influence their movement and habitat use. Space use is a fundamental component of an animal’s ecology, and the extent of an animal’s home range has consequences for individual distributions, community structure and ecosystem function. As ocean temperatures continue to rise as a result of global warming, determining the effects of temperature on space use and movement patterns of important fisheries species is vital. Our aim was to investigate the spatial and temporal variation in space use by a tropical fisheries species, the leopard coralgrouper (Plectropomus leopardus), from two latitudinally distinct locations on Australia’s Great Barrier Reef to determine the potential response of large‐bodied tropical fishes to ocean warming through behavioural modification. Using passive acoustic telemetry of 36 tagged individuals, we found that both core use areas (50%KUD) and home range extent (95%KUD) varied with respect to location, season, body size and temperature. Average home range extent (95%KUD) for tagged P. leopardus was 0.32 km2 at the high‐latitude location (Heron Island) compared to 0.23 km2 at the low‐latitude location (Opal Reef). However, core use areas (50%KUD) did not differ significantly between the two locations. Seasonal differences were also apparent at both locations with P. leopardusshowing contraction in home range extent during the summertime. This effect was most pronounced at the low‐latitude location where home range was significantly reduced during summer when temperatures exceeded 27°C. Taken together, our findings indicate that higher ambient temperature may elicit a sustained and significant decline in space use by a commercially important reef fish. Given projected increases in ocean temperature due to global climate change, large‐bodied reef fishes may be increasingly constrained in their movement and space use, which will have ramifications for individual fitness, population viability, fisheries productivity and ecological function. A plain language summary is available for this article.

Direct and indirect effects of heatwaves on a coral reef fishery

“…Higher feeding rates in warmer seas may explain the increase in catchability: the reef line fishery uses bait or lures to catch fish (Leigh et al, 2014), so fish may be more likely to take the line if they are feeding at a higher rate. Warming to the extent that occurred in the heatwave reduces spontaneous swimming speed (Johansen et al, 2014), and warmer climates and seasons are also associated with smaller home ranges (Scott et al, 2019). Swimming speed and home range size may both affect the likelihood that coral trout take bait or lures.…”

“…However, it is unlikely that the reduction in biomass observed is indicative of coral trout migrating to reefs beyond the span of the UVC surveys, because coral trout are most common down to depths of 20 m (Leigh et al, 2014) and the UVC surveys included surveys to 17 m (Stuart‐Smith et al, 2018). Home range size also changes in response to temperature (Scott et al, 2019), and home‐range size may affect the likelihood of detecting fish on UVC surveys, though it is not clear in what direction. Electronic tagging studies (e.g.…”

“…Electronic tagging studies (e.g. Scott et al, 2019) and paired catch‐UVC studies (Bacheler & Shertzer, 2020) would help identify the mechanism for reduced biomass at warm sites.…”

Comparative demography of commercially important species of coral grouper, Plectropomus leopardus and P. laevis, from Australia's great barrier reef and Coral Sea marine parks

“…Individuals of P. leopardus , for example, modified their food intake at warmer temperatures and spent more time resting to meet the energetic demands associated with an increasing metabolism (Johansen et al ., 2014, 2015). Studies also show that the activity of P. leopardus declines at temperatures above 27°C (Scott et al ., 2019). Such effects are likely to have cascading consequences for the population dynamics and demography of these commercially and functionally important species.…”

“…Studies also show that the activity of P. leopardus declines at temperatures above 27 C (Scott et al, 2019). Such effects are likely to have cascading consequences for the population dynamics and demography of these commercially and functionally important species.…”