Ecological interactions between Antarctic krill (Euphausia superba) and baleen whales in the South Sandwich Islands region – Exploring predator-prey biomass ratios

Following the cessation of whaling, the southwest Atlantic humpback whale (Megaptera novaeangliae) population is thought to be close to pre-exploitation size, reversing 20th century changes in abundance. Using a model-based approach applied to concurrently collected data on baleen whale abundance and Antarctic krill (Euphausia superba) biomass in the South Sandwich Islands (SSI) region, we explore ecological interactions between these taxa. Krill biomass and baleen whale density were highest to the north and northeast of the SSI, where the Antarctic Circumpolar Current (ACC) is deflected around the island chain. Humpback whale density was elevated at locations of krill biomass density >150 gm-2. Krill consumption by baleen whales was estimated at 19–29% of the available krill standing stock. We used historic whaling data to confirm the plausibility of these consumption rates and found evidence of rapid weight gain in humpback whales, such that blubber depleted during the breeding season could be restored in a much shorter period than previously assumed. Little is known about krill replenishment rates in the flow of the ACC, or about niche separation between recovering baleen whale populations; both factors may affect species carrying capacities and further monitoring will be required to inform the management of human activities in the region

Site use and connectivity of female grey seals (Halichoerus grypus) around Wales

The UK Natural Environment Research Council (NERC) provided core funding to the Sea Mammal Research Unit during this work and NERC Grant No. NE/G008930/1 to PP and LH to develop photo-ID use for grey seals. The Esmée Fairbairn Foundation provided additional funding to PP and LH for photo-ID work with grey seals. NRW funded survey work by MB, LM, SW and PS; contracted LH for survey design, software development and data management; IL and PP for work related to the production of this manuscript.Grey seals (Halichoerus grypus) are a qualifying feature of three special areas of conservation (SACs) in Wales, yet relatively little is known of their site use along this coastline. Since 1992, many individuals and organisations have contributed to a grey seal photographic identification database held by Natural Resources Wales, which is one of the largest and oldest of its kind, providing key information from grey seal haul-out sites around the Celtic and Irish Seas. Here, we investigated spatial connectivity of haul-out sites and fidelity of adult females to breeding sites. The minimum number of adult female grey seals using the area between 1992 and 2016 was 2688. Individual capture histories and relative spatial transition probabilities (Pij) between pairs of location groups were calculated. Adjacent locations were highly connected (e.g. Lleyn Peninsula and Bardsey, Pij = 0.7) but connections spanned the entire region, up to 230 km apart (e.g. Skomer and Dee Estuary, Pij = 0.004). Resights were recorded within SACs (e.g. Lleyn Peninsula and Bardsey [Lleyn Peninsula and the Sarnau SAC], Pij = 0.7), between SACs (e.g. Bardsey and Skomer [Pembrokeshire Marine], Pij = 0.03), between SACs and non-designated areas (e.g. Skerries and Bardsey, Pij = 0.09) and between sites outside any protected area (e.g. Dee Estuary and Anglesey, Pij = 0.5). While inter-annual fidelity to breeding sites was high (Pij = 0.82–1), individual female grey seals moved throughout the region. This evidence of extensive site use beyond protected areas is important for the management and conservation of grey seals around Wales.Publisher PDFPeer reviewe

Glucocorticoids can activate the α-ENaC gene promoter independently of SGK1

The role of SGK1 (serum- and glucocorticoid-induced protein kinase 1) in the glucocorticoid induction of α-ENaC (epithelial Na+ channel α subunit) gene transcription was explored by monitoring the transcriptional activity of a luciferase-linked, α-ENaC reporter gene construct (pGL3-KR1) expressed in H441 airway epithelial cells. Dexamethasone evoked a concentration-dependent (EC50∼4 μM) increase in transcriptional activity dependent upon a glucocorticoid response element in the α-ENaC sequence. Although dexamethasone also activated endogenous SGK1, artificially increasing cellular SGK1 activity by expressing a constitutively active SGK1 mutant (SGK1-S422D) in hormone-deprived cells did not activate pGL3-KR1. Moreover, expression of catalytically inactive SGK1 (SGK1-K127A) suppressed the activation of endogenous SGK1 without affecting the transcriptional response to dexamethasone. Increasing cellular PI3K (phosphoinositide 3-kinase) activity by expressing a membrane-anchored form of the catalytic PI3K-P110α subunit [CD2 (cluster of differentiation 2)-P110α] also activated endogenous SGK1 without affecting pGL3-KR1activity. A catalytically inactive form of CD2-P110α (R1130P), on the other hand, prevented the dexamethasone-induced activation of SGK1, but did not inhibit the activation of pGL3-KR1. However, expression of SGK1-S422D or CD2-P110α enhanced the transcriptional responses to maximally effective concentrations of dexamethasone and this effect occurred with no change in EC50. Dexamethasone-induced (0.3–300 nM) activation of pGL3-KR1 was unaffected by inhibitors of PI3K (PI-103 and wortmanin) and by rapamycin, a selective inhibitor of the TORC1 (target of rapamycin complex 1) signalling complex. Dexamethasone-induced activation of the α-ENaC gene promoter can thus occur independently of SGK1/PI3K, although this pathway does provide a mechanism that allows this transcriptional response to dexamethasone to be enhanced

Predicting suitable coastal habitat for sei whales, southern right whales and dolphins around the Falkland Islands.

Species distribution models (SDMs) are valuable tools for describing the occurrence of species and predicting suitable habitats. This study used generalized additive models (GAMs) and MaxEnt models to predict the relative densities of four cetacean species (sei whale Balaeanoptera borealis, southern right whale Eubalaena australis, Peale's dolphin Lagenorhynchus australis, and Commerson's dolphin Cephalorhynchus commersonii) in neritic waters (≤100 m depth) around the Falkland Islands, using boat survey data collected over three seasons (2017-2019). The model predictor variables (PVs) included remotely sensed environmental variables (sea surface temperature, SST, and chlorophyll-a concentration) and static geographical variables (e.g. water depth, distance to shore, slope). The GAM results explained 35 to 41% of the total deviance for sei whale, combined sei whales and unidentified large baleen whales, and Commerson's dolphins, but only 17% of the deviance for Peale's dolphins. The MaxEnt models for all species had low to moderate discriminatory power. The relative density of sei whales increased with SST in both models, and their predicted distribution was widespread across the inner shelf which is consistent with the use of Falklands' waters as a coastal summer feeding ground. Peale's dolphins and Commerson's dolphins were largely sympatric across the study area. However, the relative densities of Commerson's dolphins were generally predicted to be higher in nearshore, semi-enclosed, waters compared with Peale's dolphins, suggesting some habitat partitioning. The models for southern right whales performed poorly and the results were not considered meaningful, perhaps due to this species exhibiting fewer strong habitat preferences around the Falklands. The modelling results are applicable to marine spatial planning to identify where the occurrence of cetacean species and anthropogenic activities may most overlap. Additionally, the results can inform the process of delineating a potential Key Biodiversity Area for sei whales in the Falkland Islands

Upwellings, canyons and whales: An important winter habitat for balaenopterid whales off Mauritania, northwest Africa

ABSTRACT The aim of this study was to identify critical habitats for baleen whales in the Mauritanian upwelling zone using data collected from a platform of opportunity: a 60 day geophysical survey approximately 100km southwest of Cap Blanc, Mauritania in winter (2012/13). The bathymetry of the 5,500km 2 study area was complex, including parts of the Cap Timiris Canyon system. Large whales, including sei and blue whales, accounted for 70% of the 238 cetacean sightings. Species identification was often problematic, especially in the case of balaenopterid whales, so data for all whales of this genus were pooled for the estimation of abundance and distribution. Spatial modelling was applied to estimate abundance and to plot a predicted density map of balaenopterid whales. Depth and the chlorophyll-a concentration when at its peak (in the previous September) were significant predictors of whale density. Point abundance in the study area was estimated at 272 whales (95% CI 265-279) and density was highest in the depth range 500-2,250m near to the canyon system (6.18 whales/100km 2 , 95% CI 6.03-6.51). Steep seabed topography created by canyons running off the shelf edge, together with the strong upwelling system, probably create optimal habitats for the euphausiid prey of sei and blue whales. Sei whales were observed skim-feeding at dawn or dusk on seven occasions; in one sighting an aggregation of 18 skim-feeding sei whales were observed. The high density of these baleen whale species in such a highly productive area and direct observation of feeding behaviour in sei whales, provides evidence of feeding during the winter breeding season, when they have previously been presumed to feed less. This study demonstrates the potential value of collecting further data on seismic survey vessels and would improve understanding of cetacean ecology in remote and under-explored regions

Cetacean sightings from the British Antarctic Survey CCAMLR synoptic krill survey of South Georgia and the South Sandwich Islands, January to February 2019

Cetacean sightings in South Georgia and South Sandwich Islands waters, made by a team of four professional marine mammal observers during the British Antarctic Survey CCAMLR synoptic krill survey on the RRS James Cook (DY098), January and February 2019. The latitude and longitude of each sighting, the identified species, bearing and distance from the vessel, and estimated group size are provided. These data have been used by BAS to estimate (i) humpback whale and (ii) baleen whale abundance in South Georgia and South Sandwich Islands waters in 2019. Funding provided by the Foreign, Commonwealth and Development Office, as part of the Overseas Territories Blue Belt programme, as well as the South Georgia Heritage Trust and Darwin PLUS award DPLUS057.,Sightings data were collated in the LOGGER database, using standard cetacean sighting survey protocols as detailed in the associated document "Discovery survey protocol final" and in the publication associated with these data. Distance sampling surveys took place whilst the vessel was making way (speed approx. 9 knots), there was sufficient daylight, wind speed was less than 27 knots and sea state is less than Beaufort 6. Surveys did not take place when krill trawls were in progress. Whilst on effort, there were a minimum of two observers on watch at all times and one data recorder (DR) recording sightings. Watches ran throughout the day, to maximise the time available within the constraints of the working hours specified by the UK's Natural Environment Research Council. Watch periods did not run for more than 12 hours and within that were flexible according to survey constraints and weather. The survey team rotated position every hour, with each observer spending one hour watching and the following hour either as DR or off watch, to minimise exposure. In conditions where cold exposure was heightened, the watch period was reduced to 30 minutes. Observers searched with naked eyes, scanning their search area in a consistent manner without focussing on particular regions-but making particular effort to watch directly ahead (i.e., the trackline) as much as possible. The trackline in front of the survey vessel was the sector of primary interest (for distance sampling purposes), but the sides were not neglected. The following search pattern was employed: - Port observer: searched the area from 90° port to about 10° starboard, - Starboard observer: searched the area from 90° starboard to about 10° port. This ensured that the trackline was covered by both observers. All species of cetacean were recorded. The main responsibility of the observer team was to obtain accurate information on the time, angle, radial distance, species identification and school size of as many cetacean sightings as possible. Each observer used 7x50 binoculars with reticles, a watch set to UTC and paper sightings forms & pencils to be used if LOGGER failed. Angle boards were mounted to the platform to assist with bearing identification (0 indicating directly ahead of the vessel). Radial distances to sightings were estimated using reticles to measure distance from the horizon. Angles from the trackline to the sighting were read from pointers on the mounted angle boards. At the point of the sighting, the DR also noted the direct heading of the vessel in case it differed from bearing of the vessel track (i.e. due to weather conditions). The Bridge, any ornithologists, crew or other observers were instructed not to indicate any sightings to the observers. On detecting a cue, the observer immediately informed the data recorder that they have a sighting via UHF radio. The data recorder then recorded the information straight into LOGGER. Sighting numbers are assigned in LOGGER automatically. When one observer made a detection, the other observer kept searching in their usual way unless assistance with taxonomic ID was requested. Re-sightings of the same animals were not recorded.,Sighting data were collated using LOGGER software version 2010. Each observer used 7x50 binoculars with reticles.,Data collection and QC are detailed in "Discovery survey protocol final". Where species identification was unclear, sightings were described as "unidentified whale" or similar.

Population abundance of recovering humpback whales Megaptera novaeangliae and other baleen whales in Scotia Arc, South Atlantic

The data collected from the RV ‘Kronprins Haakon’ work was supported by the Norwegian Ministry of Trade, Industry and Fisheries (NFD, via project number 15208), the Institute of Marine Research (IMR) and the IMR project Krill (project number 14246). The data collected from the FV ‘Cabo de Hornos’ was financed by the Association of Responsible Krill Harvesting Companies (ARK, www.ark-krill.org), Aker Biomarine AS (www.akerbiomarine.com), NFD via project number 15208 and the IMR project Krill.Following the cessation of whaling, South Atlantic populations of humpback Megaptera novaeangliae and some other baleen whale species are recovering, but there has been limited monitoring of their recovery in the Scotia Arc, a former whaling epicentre and a hotspot for Antarctic krill Euphausia superba. To inform the management of krill fisheries, up-to-date assessment of whale biomass and prey consumption is essential. Using a model-based approach, we provide the first estimates of whale abundance and krill consumption for South Georgia and the South Sandwich Islands and total abundance of humpback whales across their southwestern Atlantic feeding grounds, using data collected in 2019. Humpback whale abundance was estimated at 24543 (coefficient of variation, CV = 0.26; 95% CI = 14863-40528), similar to that measured in Brazil on the main wintering ground for this population. The abundance of baleen whales in South Georgia and the South Sandwich Islands, including those not identified to species level, was estimated at 43824 (CV = 0.15, 95% CI = 33509-59077). Based on the proportion of humpback whales identified during the surveys (83%), the majority of these are likely to be humpback whales. Annual krill consumption by baleen whales was estimated to be in the range 4.8 to 7.2 million tons, representing 7 to 10% of the estimated krill biomass in the region. However, there is a need to better understand feeding rates in baleen whales, and further research into this field should be a priority to improve the accuracy and precision of prey consumption rate estimation.PostprintPeer reviewe