Antarctic krill and ecosystem monitoring survey off the South Orkney Islands in 2023

Environmental monitoring along 5 set transect lines off South Orkney Islands in the Southern Ocean have been carried out annually (since 2011) by the Institute of Marine Research, Norway. Data are used to calculate biomass of Antarctic krill (Euphausia superba) as well as mapping distribution and demographic composition of krill, but also other macrozooplankton and fish taxa. Visual sightings of cetaceans and pinnipeds are registered systematically along the transects during daylight hours. During this year's survey, a pilot photo-drone project was also undertaken to investigate the potential of employing this type of technology to monitor body-size of individual whales to form the basis for calculating energetics and prey needs. Personnel were also deployed on Powell Island with breeding chinstrap penguins to satellite-tag penguins. At the same time, we maneuvered an unmanned sail drone, fitted with an echosounder, via satellite communication into what is known to be the preferred feeding area for chinstraps that breed at Powell Island. This data will be used to study swarm types in relation to penguins foraging strategies as well as assessing potential spatiotemporal overlaps with fisheries. Herein we report on the survey activities from 2023 and present some preliminary results.Antarctic krill and ecosystem monitoring survey off the South Orkney Islands in 2023publishedVersio

Changes in the abundance, species composition and distribution of the Barents Sea euphausiids (krill) : with focus on the expansion and reproduction of Meganyctiphanes norvegica

Euphausiids (krill) play a key role in the Barents Sea ecosystem, being an important prey for a number of species, and thereby transferring energy from primary producers to higher trophic levels. An unprecedented warming is currently happening in the Barents Sea, diminishing sea ice and affecting the distribution of water masses. As the Barents Sea environment is changing quickly, it crucial to estimate how euphausiid populations will be affected by climate change. The four main species of euphausiids in the Barents Sea are Thysanoeassa inermis, T. longicaudata, T. raschii and Meganyctiphanes norvegica. The goal of this thesis was to establish the relative species composition, distribution and abundance of the four main euphausiid species in the warm years of 2007-2015. For a reference, the results were compared with data collected in a colder period, during the years 1984-1992. Furthermore, an important part of understanding euphausiid population dynamics is the reproductive cycle. Therefore, this study also investigated the species composition, development and distribution of larvae in the southwestern Barents Sea, May 2015, and sought to compare these to investigations undertaken in 1988 and 1989 (Loftnes, 1993). My results show that there was a significant difference in the total abundance of euphausiids between the two study periods 1984-1992 and 2007-2015, having more than doubled from the first to the second, despite high capelin predation. Total euphausiid abundance was mainly distributed in the southwestern and south-central parts of the Barents Sea, south of 75°N in both study periods. However, T. inermis, T. longicaudata and the boreal, North-Atlantic species M. norvegica seemed to extend their distributional ranges into the northern parts of the Barents Sea during the years 2007-2015. Moreover, the abundance of M. norvegica increased from the first to the second study period, constituting a significant part of the species composition in the years 2007-2015. In contrast, abundances of the cold-water species T. raschii was significantly lower in the second study period. The distribution and species composition of euphausiid larvae of May 2015 were very similar to what was found in June 1988 and May 1989 with the largest abundances of larvae found in the Atlantic waters south of Bear Island, and the majority of larvae belonging to T. inermis. The spawning and development of larvae seemed to be related to water mass, being further developed in Coastal and Atlantic waters. Larvae of M norvegica were only found at the southernmost stations, indicating that there is still a thermal constraint on the reproduction of this species in the Barents Sea. However, if the warming continues, M. norvegica has the potential of completing a full life cycle in Barents Sea waters, which would highlight the ongoing Atlantification of the Barents Sea ecosystem.M-N

Changes in the abundance, species composition and distribution of the Barents Sea euphausiids (krill) : with focus on the expansion and reproduction of Meganyctiphanes norvegica

Euphausiids (krill) play a key role in the Barents Sea ecosystem, being an important prey for a number of species, and thereby transferring energy from primary producers to higher trophic levels. An unprecedented warming is currently happening in the Barents Sea, diminishing sea ice and affecting the distribution of water masses. As the Barents Sea environment is changing quickly, it crucial to estimate how euphausiid populations will be affected by climate change. The four main species of euphausiids in the Barents Sea are Thysanoeassa inermis, T. longicaudata, T. raschii and Meganyctiphanes norvegica. The goal of this thesis was to establish the relative species composition, distribution and abundance of the four main euphausiid species in the warm years of 2007-2015. For a reference, the results were compared with data collected in a colder period, during the years 1984-1992. Furthermore, an important part of understanding euphausiid population dynamics is the reproductive cycle. Therefore, this study also investigated the species composition, development and distribution of larvae in the southwestern Barents Sea, May 2015, and sought to compare these to investigations undertaken in 1988 and 1989 (Loftnes, 1993). My results show that there was a significant difference in the total abundance of euphausiids between the two study periods 1984-1992 and 2007-2015, having more than doubled from the first to the second, despite high capelin predation. Total euphausiid abundance was mainly distributed in the southwestern and south-central parts of the Barents Sea, south of 75°N in both study periods. However, T. inermis, T. longicaudata and the boreal, North-Atlantic species M. norvegica seemed to extend their distributional ranges into the northern parts of the Barents Sea during the years 2007-2015. Moreover, the abundance of M. norvegica increased from the first to the second study period, constituting a significant part of the species composition in the years 2007-2015. In contrast, abundances of the cold-water species T. raschii was significantly lower in the second study period. The distribution and species composition of euphausiid larvae of May 2015 were very similar to what was found in June 1988 and May 1989 with the largest abundances of larvae found in the Atlantic waters south of Bear Island, and the majority of larvae belonging to T. inermis. The spawning and development of larvae seemed to be related to water mass, being further developed in Coastal and Atlantic waters. Larvae of M norvegica were only found at the southernmost stations, indicating that there is still a thermal constraint on the reproduction of this species in the Barents Sea. However, if the warming continues, M. norvegica has the potential of completing a full life cycle in Barents Sea waters, which would highlight the ongoing Atlantification of the Barents Sea ecosystem