Temperature alters the predator-prey size relationships and size-selectivity of Southern Ocean fish.

A primary response of many marine ectotherms to warming is a reduction in body size, to lower the metabolic costs associated with higher temperatures. The impact of such changes on ecosystem dynamics and stability will depend on the resulting changes to community size-structure, but few studies have investigated how temperature affects the relative size of predators and their prey in natural systems. We utilise >3700 prey size measurements from ten Southern Ocean lanternfish species sampled across >10° of latitude to investigate how temperature influences predator-prey size relationships and size-selective feeding.

Diving into the vertical dimension of elasmobranch movement ecology.

Knowledge of the three-dimensional movement patterns of elasmobranchs is vital to understand their ecological roles and exposure to anthropogenic pressures. To date, comparative studies among species at global scales have mostly focused on horizontal movements. Our study addresses the knowledge gap of vertical movements by compiling the first global synthesis of vertical habitat use by elasmobranchs from data obtained by deployment of 989 biotelemetry tags on 38 elasmobranch species.

Myctobase, a circumpolar database of mesopelagic fishes for new insights into deep pelagic prey fields.

The global importance of mesopelagic fish is increasingly recognised, but they remain poorly studied. This is particularly true in the Southern Ocean, where mesopelagic fishes are both key predators and prey, but where the remote environment makes sampling challenging. Despite this, multiple national Antarctic research programs have undertaken regional sampling of mesopelagic fish over several decades.

Oxidative stress, metabolic activity and mercury concentrations in Antarctic krill Euphausia superba and myctophid fish of the Southern Ocean.

Indicators of oxidative stress and metabolic capacity are key factors in understanding the fitness of wild populations. In the present study, these factors were evaluated in the pelagic Southern Ocean taxa Antarctic krill (Euphausia superba) and myctophid fish (Electrona antarctica, Gymnoscopelus braueri and G. nicholsi) to establish a baseline record for future studies.

Mercury biomagnification in a Southern Ocean food web.

Biomagnification of mercury (Hg) in the Scotia Sea food web of the Southern Ocean was examined using the stable isotope ratios of nitrogen (δN) and carbon (δC) as proxies for trophic level and feeding habitat, respectively. Total Hg and stable isotopes were measured in samples of particulate organic matter (POM), zooplankton, squid, myctophid fish, notothenioid fish and seabird tissues collected in two years (austral summers 2007/08 and 2016/17). Overall, there was extensive overlap in δC values across taxonomic groups suggesting similarities in habitats, with the exception of the seabirds, which showed some differences, possibly due to the type of tissue analysed (feathers instead of muscle).

Main drivers of mercury levels in Southern Ocean lantern fish Myctophidae.

Myctophids are the most abundant fish group in the Southern Ocean pelagic ecosystem and are an important link in the Antarctic marine food web. Due to their major ecological role, evaluating the level of mercury (Hg) contamination in myctophids is important as a step towards understanding the trophic pathway of this contaminant. The concentrations of total Hg were determined in muscle, gill, heart and liver tissue of 9 myctophid species to quantify tissue partitioning variability between species.

Age and growth of Brauer's lanternfish Gymnoscopelus braueri and rhombic lanternfish Krefftichthys anderssoni (Family Myctophidae) in the Scotia Sea, Southern Ocean.

This study examines age and growth of Brauer's lanternfish Gymnoscopelus braueri and rhombic lanternfish Krefftichthys anderssoni from the Scotia Sea in the Southern Ocean, through the analysis of annual growth increments deposited on sagittal otoliths. Otolith pairs from 177 G. braueri and 118 K.