Falklands Conservation

The Patagonian Sea is a highly productive marine ecosystem and a hotspot for seabird diversity and density in the Southwest Atlantic Ocean. Reports of unusual mortality events are relatively scarce in this region, likely due to under detection and investigation. In this study, we report on four unusual mortality events affecting seabirds in the Patagonian Sea from 2000 to 2006. Events 1 and 2 occurred at Golfo Nuevo and Chubut coast, Argentina in September–December 2000, affecting at least 4550 seabirds, mainly Magellanic penguins (Spheniscus magellanicus). Event 3 occurred at the Falkland/Malvinas Islands during December 2002–January 2003, affecting at least 3500 seabirds, mainly gentoo penguins (Pygoscelis papua). Event 4 occurred at Punta Loma and Punta León, Argentina, in November 2006, affecting at least 57 seabirds, mainly kelp gulls (Larus dominicanus). The aetiology of Events 1 and 2 could not be determined, but malnutrition/starvation and paralytic shellfish poisoning, respectively, were identified as potential causes. Pathological findings and toxicological testing supported paralytic shellfish poisoning as the cause of Events 3 and 4. Our results illustrate how identifying the occurrence, cause and extent of unusual mortality events affecting seabirds can present significant challenges. Moreover, our investigations of the events display variations in timeliness and completeness, and our lack of certainty on aetiology reflects the shortcomings often faced in remote locations and low resource settings. Technological advances, such as smartphones, increased public awareness and connectivity, coupled with more and better equipped protected areas and diagnostic laboratories will likely aid in overcoming difficulties from past decades.

Extreme weather events are among the most critical aspects of climate change, but our understanding of their impacts on biological populations remains limited. Here, we exploit the rare opportunity provided by the availability of concurrent longitudinal demographic data on two neighbouring marine top predator populations (the black-browed albatross, Thalassarche melanophris, breeding in two nearby colonies) hit by an exceptionally violent storm during one study year. The aim of this study is to quantify the demographic impacts of extreme events on albatrosses and test the hypothesis that extreme events would synchronously decrease survival rates of neighbouring populations. Using demographic modelling we found that, contrary to our expectation, the storm affected the survival of albatrosses from only one of the two colonies, more than doubling the annual mortality rate compared to the study average. Furthermore, the effects of storms on adult survival would lead to substantial population declines (up to 2% per year) under simulated scenarios of increased storm frequencies. We, therefore, conclude that extreme events can result in very different local-scale impacts on sympatric populations. Crucially, by driving demographic asynchrony, extreme events can hamper our understanding of the demographic responses of wild populations to mean, long-term shifts in climate.

Abstract Invasive non‐native species (INNS) are recognized as a major threat to island biodiversity, ecosystems, and economies globally. Preventing high‐risk INNS from being introduced is the most cost‐effective way to avoid their adverse impacts. We applied a horizon scanning approach to identify potentially INNS in the United Kingdom Overseas Territories (OTs), ranging from Antarctica to the Caribbean, and from the Pacific to the Atlantic. High‐risk species were identified according to their potential for arrival, establishment, and likely impacts on biodiversity and ecosystem function, economies, and human health. Across OTs, 231 taxa were included on high‐risk lists. The highest ranking species were the Asian green mussel ( Perna viridis ), little fire ant ( Wasmannia auropunctata ), brown rat ( Rattus norvegicus ), and mesquite tree ( Prosopis juliflora ). Shipping containers were identified as the introduction pathway associated with the most species. The shared high‐risk species and pathways identified provide a guide for other remote islands and archipelagos to focus ongoing biosecurity and surveillance aimed at preventing future incursions.

Abstract Population monitoring of colonial seabirds is often complicated by the large size of colonies, remote locations, and close inter- and intra-species aggregation. While drones have been successfully used to monitor large inaccessible colonies, the vast amount of imagery collected introduces a data analysis bottleneck. Convolutional neural networks (CNN) are evolving as a prominent means for object detection and can be applied to drone imagery for population monitoring. In this study, we explored the use of these technologies to increase capabilities for seabird monitoring by using CNNs to detect and enumerate Black-browed Albatrosses (Thalassarche melanophris) and Southern Rockhopper Penguins (Eudyptes c. chrysocome) at one of their largest breeding colonies, the Falkland (Malvinas) Islands. Our results showed that these techniques have great potential for seabird monitoring at significant and spatially complex colonies, producing accuracies of correctly detecting and counting birds at 97.66% (Black-browed Albatrosses) and 87.16% (Southern Rockhopper Penguins), with 90% of automated counts being within 5% of manual counts from imagery. The results of this study indicate CNN methods are a viable population assessment tool, providing opportunities to reduce manual labor, cost, and human error.

Patagonian toothfish Dissostichus eleginoides Smitt 1898, is an important commercially targeted Notothenioid species in South-Atlantic waters. In this study we aimed to clarify several aspects of reproductive biology of Patagonian toothfish in the Falkland Islands waters. Histological examination of female gonads indicates that with the beginning of maturation females maintain at least two populations of oocytes, suggesting that toothfish requires up to two years for oocytes development. Females become mature at an average size of 79.1 cm indicating a decrease of first maturity size if toothfish females in the Falkland Island waters. The majority of females spawn at the size from 101 to 130 cm total length. Distribution of reproductive phases shows an increase of females at developing stage in December and March prior to the spawning peaks in May and August respectively. However, the majority of the toothfish population consist of non-spawning individuals remaining in regressing phase (55.8 to 85.6%) including the spawning period. The skip-spawning for toothfish has been defined as reabsorbing non-reproductive and resting types. The abbreviation of oocytes development in the gonads was observed from 1 to 22.1% of females which omitted the spawning season. Most likely females which remain in the spawning area have the opportunity to spawn more often, whereas females which undergo foraging migration toward Northern parts of the Falklands waters return to the spawning ground less often. Females remain Northern area longer to accumulate necessary amount of energy. This hypnotise is supported by the presence of females in immature, developing and regressing phase throughout surrounding Falkland Islands waters. Presence of post-spawning females in regressing stage throughout the Falklands waters suggest that toothfish may undertake irregular spawning/foraging migration when favourable for spawning condition occur.

Abstract Remote island ecosystems are vulnerable to human disturbance and habitat destruction, yet they often have limited capacity to revegetate degraded habitats, especially with native species. To revegetate degraded island habitats, practitioners often rely on importing non‐native species, thereby increasing the number of introduced species on islands. In this study, we investigated the effectiveness of sowing wild collected native seeds and locally sourced treatments for revegetating different eroded soil types (clay, peat, and sand) across the Falkland Islands. A seed mixture of 15 native species was sown with different supportive treatments (sheep dung, sheep dags [woolly off‐cuts], and geotextile matting [coir]) and their combinations. After 1 year, native seeds provided up to 70% plant cover and accrued 1.98 kg/m2 in biomass. Three key native species Elymus magellanicus, Poa flabellata, and Poa alopecurus occurred in 64, 50, and 50% of all sown plots. However, supportive treatments equally facilitated the colonization and establishment of non‐native species. At the same time, there was no difference in native plant cover and biomass across different treatments or soil types, although in the absence of supportive treatments there was little to no revegetation. Thus, locally sourced treatments (i.e. sheep dung and dags) may provide an equally effective but low‐cost alternative to imported treatments (i.e. geotextiles). We further discuss challenges of integrating revegetation using native seeds and livestock grazing on the Falkland Islands. Our study demonstrates that native species and local treatments can provide a rapid approach to revegetating degraded island habitats.

South Georgia has been the southernmost location where populations of invasive house mice Mus musculus are found. The distribution of mice was investigated at Cape Rosa and the Nunez Peninsula, the two areas of South Georgia where the species is known to occur. Live-trapping and kill-trapping took place during March 2012, at the end of the austral summer, with traps in four grids (3.2–4.0 ha in area) and on 34 trap lines distributed across a range of habitats from the shoreline to 250 m above sea level. Mice were scarce, with just 68 captures in about 1750 trap nights. Mouse densities in tussock habitat were estimated at 2.1–2.8 mice/ha, with higher densities of 5.3–6.4 mice/ha along the coastline. Mice were found in all habitats apart from higher-altitude fellfield, but were relatively less abundant in tussock habitat with large numbers of seals. Mice were breeding at both sites with 58 % of mature females pregnant or lactating. Litter size (7.1 ± 2.3 embryos) and adult body mass (21.4 ± 4.6 g) were typical of most other island mice populations. Population densities of mice on South Georgia are two orders of magnitude lower than mouse densities measured at other sub-Antarctic islands. The very low population density and its restricted distribution, with most captures close to the shore, and the presence of large numbers of burrowing petrels and South Georgia pipits Anthus antarcticus at both sites, suggest that mice have a relatively limited impact on South Georgia’s vertebrate biodiversity.

Mackerel icefish (Champsocephalus gunnari) is a semi-pelagic finfish species inhabiting shelf areas in the Southern Ocean. The population at South Georgia is currently exploited by pelagic trawlers fishing close to the seabed. Annual catches peaked at 150,000 t in 1983 and have declined since the mid-to-late 1980s. Bottom-trawl surveys have been conducted since 1987, providing a time series of abundance and size distribution for use in assessing the status of the stock and setting quotas. Food web models suggest that estimates of the biomass from survey data are substantially lower than the amount of icefish required by the local ecosystem. The aim of this study was to assess the uncertainty around current estimates of density and variance, using alternative nonparametric stratified bootstrapping methods. The stratified rescaling bootstrap estimator was identified as the most appropriate method of those tested: in comparison with the existing method, confidence intervals and the inter-annual variability of the estimates were reduced. Numbers-at-age were estimated from mixture distribution models fitted to length-disaggregated density data in order to determine whether individual cohorts were consistently detected by the surveys. Estimates of numbers-at-age could not consistently delineate cohorts in successive years indicating that survey-based estimates of density were biased. These biases may have arisen because the trawl gear did not select individuals of all sizes equally, or because sampling was restricted to the demersal component of the stock. Estimates of abundance of the pelagic component of the stock should be derived from acoustic data to improve the assessment.

This study investigated spatial and temporal patterns in distribution, population structure and diet of Bolin's lanternfish Protomyctophum bolini, Tenison's lanternfish Protomyctophum tenisoni and gaptooth lanternfish Protomyctophum choriodon in the Scotia Sea using data collected by midwater trawl during spring, summer and autumn. Protomyctophum bolini was the most abundant species of the genus encountered throughout the Scotia Sea with the greatest concentrations occurring around the Antarctic Polar Front (APF). This species had a life cycle of 2+ years, but spatial differences in population structure were apparent as the I-group was absent from all regions south of the APF, suggesting that the species does not recruit in the Scotia Sea. Protomyctophum tenisoni occurred mostly in waters characteristic of the APF and was absent from the southern Scotia Sea. It had a limited size range, but there was clear size-related sexual dimorphism with males significantly larger than females. The species had a life cycle of c. 2 years, but the I-group (c. 1 year old, 1 November to 31 October the next year) occurred only in regions close to the APF suggesting that recruitment is restricted to these waters. A seasonal southward migration for P. choriodon is likely as the species occurred mostly to the south-west of South Georgia in summer, but extended to the sea-ice sectors in autumn. Protomyctophum choriodon had a life cycle of 4+ years in the Scotia Sea and the population was dominated by age classes >3 years old. Larval stages were absent during the surveys for all species. Diurnal variations in vertical distribution were apparent for all three species. Interspecific variations in diet were evident, but all species were primarily copepod feeders, with Metridia spp., Rhincalanus gigas and Calanus simillimus generally dominating their diet. Small euphausiids, principally Thysanoessa spp., were also an important component of their diets, particularly for P. choriodon which had the largest body size. The spatial and temporal variations in diet for both P. bolini and P. tenisoni were broadly consistent with underlying abundance patterns within the mesozooplankton community.

The biology of littoral fauna of the Falkland Islands is largely unknown. This pilot study was launched by Shallow Marine Surveys Group and was aimed at investigating life history of the Antarctic starfish, Anasterias antarctica, a dominating invertebrate predator of intertidal and subtidal, including its distribution, seasonal and ontogenetic migrations, spawning seasonality, fecundity, growth, and feeding habits. A total of 3,426 starfish were sampled in different habitats around the Falkland Islands at low tide using SCUBA diving. Sampling included measuring arm length, presence/absence of brooding and feeding; the prey was identified to the lowest taxa and measured if condition permitted. In a total of 48 broods, eggs were counted and embryonic stage assigned. This medium-sized species attains an arm length of 96 mm (85.4 g). The size increased with depth and starfish carry out seasonal bathymetric migrations with smaller animals ( 10 m depth in winter. Egg laying occurs between March and July, and juvenile dispersal—mostly in October–November. Fecundity (52–363 eggs) and egg/offspring size increase with maternal size. Juvenile starfish are of ca. 2 mm arm length and grow to 9–11 mm in 1 year. Feeding intensity is at a maximum before and after the reproductive period. Females might occasionally resume feeding when they are still brooding a small number of juveniles. The starfish prey upon isopods (Sphaeromatidae), molluscs Pareuthria spp. and variety of gastropods, bivalves chitons, barnacles, and also scavenges. Prey size increases with starfish size.