Habitat use and activity patterns of female Deacon Rockfish (Sebastes diaconus) at seasonal scales and in response to episodic hypoxia

We combined a high-resolution acoustic telemetry array with presence/absence receivers to conduct a preliminary study of the seasonal movements, activity patterns, and habitat associations of the newly described Deacon Rockfish (Sebastes diaconus). Eleven mature female Deacon Rockfish were tagged and monitored during an 11-month period, at a nearshore rocky reef off Seal Rock, Oregon, USA, an area of recurring seasonal hypoxia (defined as dissolved oxygen concentration [DO] < 2 mg l−1). Two tags were detected leaving the study area by day 35, indicating predation or emigration. Three tags became inactive within the array, indicating tag loss or fish death. Six “resident” fish inhabited the array for 246–326 days. Resident fish exhibited high site fidelity, small home ranges (mean 95% KDE = 4907 m2), and consistent activity patterns for the duration of the summertime high-resolution array (5 months), except during seasonal hypoxia. Resident fish were strongly diurnal in summer, with high levels of daytime activity above the bottom in relatively rugose habitat, followed by nighttime rest periods in deeper, less rugose habitat. During summertime hypoxia, resident fish exhibited less daytime activity during daytime hours with no rest periods at night, inhabited shallower water depths, and moved well away from their core activity areas on long, erratic forays. During the winter, diel patterns were less evident with higher activity levels at night (than in the summer) and lower activity levels in the day (than in the summer). We propose that some Deacon Rockfish continuously inhabit nearshore reefs throughout the year, but that daily/seasonal movement patterns, seasonally occurring hypoxia, and prey preferences for planktonic organisms influence relocation.

Behavioural traits and feeding ecology of Mediterranean lionfish and naiveté of native species to lionfish predation

The detrimental effects of invasion by Indo-Pacific lionfish Pterois volitans/miles on western Atlantic fishes have spurred concerns for Mediterranean fish biodiversity, where Lessepsian lionfish P. miles have recently established populations in the eastern basin. In order to assess the potential impact on biodiversity, we examined key behavioural and ecological traits of lionfish and the resident fish community in the Mediterranean that may contribute to lionfish invasion success. We focussed on Cyprus, where lionfish were first sighted in 2012 and have now formed abundant and stable populations. Using field observations, we examined lionfish predatory behaviour and feeding ecology, and naiveté of resident fish species to hunting lionfish. Our findings suggest that lionfish in the Mediterranean are crepuscular generalist predators, with targeted prey dominated by small-bodied benthic or bentho-pelagic associated species. Such prey are more likely to be native than introduced (Lessepsian) fishes, with native prey fishes showing greater naiveté towards lionfish than Lessepsian prey species. Notably, one of the Mediterranean’s key ecological fish species (the native damselfish Chromis chromis) showed the highest level of naiveté and was the most heavily targeted prey. Overall, lionfish in the Mediterranean show similar predatory behaviour and ecology to their western Atlantic counterparts. Although the establishment of Mediterranean lionfish populations is still recent, it may result in a similar disruption to reef fish biomass to that recorded in the Atlantic, with impacts on the structure and biodiversity of reef fish communities and the services they provide.

Behavioural traits and feeding ecology of Mediterranean lionfish and native species naiveté to lionfish predation

ABSTRACTThe detrimental effects of invasion by Indo-Pacific lionfish (Pterois volitans/miles) on western Atlantic fishes have spurred concerns for Mediterranean fish biodiversity, where a Lessepsian invasion of lionfish has recently begun. In order to assess the potential impact on biodiversity, we examine key behavioural and ecological traits of lionfish, and the resident fish community in the Mediterranean, that may contribute to lionfish invasion success. We focus on Cyprus, where lionfish populations were first sighted in 2012 and have now established abundant and stable populations. Using field observations, we examine lionfish predatory behaviour and feeding ecology, and resident fish species naiveté to hunting lionfish. Our findings suggest that lionfish in the Mediterranean are crepuscular generalist predators, with prey targeted dominated by small-bodied benthic or bentho-pelagic associated species. Such prey are more likely to be native than introduced (Lessepsian) fishes, with native prey fishes showing greater naiveté towards lionfish than Lessepsian prey species. Notably, one of the Mediterranean’s key ecological fish species (the native damselfish Chromis chromis), showed the highest level of naiveté and was the most heavily targeted prey. Overall, lionfish in the Mediterranean show similar predatory behaviour and ecology to their western Atlantic counterparts. Although the Mediterranean invasion is still relatively recent, it may result in a similar disruption to reef fish biomass to that recorded in the Atlantic, with impact to the structure and biodiversity of reef fish communities and the services they provide.