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The Falkland Shelf is a highly productive ecosystem in the Southwest Atlantic Ocean. It is characterized by upwelling oceanographic dynamics and displays a wasp-waist structure, with few intermediate trophic-level species and many top predators that migrate on the shelf for feeding. One of these resident intermediate trophic-level species, the Patagonian longfin-squid Doryteuthis gahi, is abundant and plays an important role in the ecosystem. We used two methods to estimate the trophic structure of the Falkland Shelf food web, focusing on the trophic niche of D. gahi and its impacts on other species and functional groups to highlight the importance of D. gahi in the ecosystem. First, stable isotope measurements served to calculate trophic levels based on an established nitrogen baseline. Second, an Ecopath model was built to corroborate trophic levels derived from stable isotopes and inform about trophic interactions of D. gahi with other functional groups. The results of both methods placed D. gahi in the centre of the ecosystem with a trophic level of ∼ 3. The Ecopath model predicted high impacts and therefore a high keystoneness for both seasonal cohorts of D. gahi. Our results show that the Falkland Shelf is not only controlled by species feeding at the top and the bottom of the trophic chain. The importance of species feeding at the third trophic level (e.g. D. gahi and Patagonotothen ramsayi) and observed architecture of energy flows confirm the ecosystem's wasp-waist structure with middle-out control mechanisms at play.

Zooplankton communities vary in space and time. Their composition is strongly influenced by lower trophic levels that are dependent on the availability of light and nutrients. As all marine ecosystems are relying on zooplankton as intermediate trophic step between primary production and higher trophic levels, changes in the zooplankton community composition and biomass can cascade through the food web with important impacts on fish communities and through that on fisheries yields. An intense fisheries exist around the Falkland Islands in the SW Atlantic Ocean, around 51° S, but to the best of our knowledge, no previous study has to date investigated the seasonal variation in zooplankton community composition in these waters. We show that copepods (39.2%), the larvae of the anomurid Grimothea gregaria (33.1%) and euphausiids (10.9%) dominate the local mesozooplankton community by biomass. All species showed seasonal patterns, including ontogenetic behaviour of G. gregaria migrating to deeper waters with development, which were significantly explained by temperature (p < 0.001). While overall biomass significantly decreased with distance from shore (p < 0.001), mesozooplankton diversity was highest at 30 km from shore. The presented study is the first assessment of the mesozooplankton biomass off the Falkland Islands and provides a first baseline to aid future ecosystem studies in the context of ecosystem based fisheries management in the region.

The Falkland Islands marine environment host a mix of temperate and subantarctic species. This review synthesizes baseline information regarding ontogenetic migration patterns and trophic interactions in relation to oceanographic dynamics of the Falkland Shelf, which is useful to inform ecosystem modelling. Many species are strongly influenced by regional oceanographic dynamics that bring together different water masses, resulting in high primary production which supports high biomass in the rest of the food web. Further, many species, including those of commercial interest, show complex ontogenetic migrations that separate spawning, nursing, and feeding grounds spatially and temporally, producing food web connections across space and time. The oceanographic and biological dynamics may make the ecosystem vulnerable to climatic changes in temperature and shifts in the surrounding area. The Falkland marine ecosystem has been understudied and various functional groups, deep-sea habitats and inshore-offshore connections are poorly understood and should be priorities for further research.

Marine biota are redistributing at a rapid pace in response to climate change and shifting seascapes. While changes in fish populations and community structure threaten the sustainability of fisheries, our capacity to adapt by tracking and projecting marine species remains a challenge due to data discontinuities in biological observations, lack of data availability, and mismatch between data and real species distributions. To assess the extent of this challenge, we review the global status and accessibility of ongoing scientific bottom trawl surveys. In total, we gathered metadata for 283,925 samples from 95 surveys conducted regularly from 2001 to 2019. We identified that 59% of the metadata collected are not publicly available, highlighting that the availability of data is the most important challenge to assess species redistributions under global climate change. Given that the primary purpose of surveys is to provide independent data to inform stock assessment of commercially important populations, we further highlight that single surveys do not cover the full range of the main commercial demersal fish species. An average of 18 surveys is needed to cover at least 50% of species ranges, demonstrating the importance of combining multiple surveys to evaluate species range shifts. We assess the potential for combining surveys to track transboundary species redistributions and show that differences in sampling schemes and inconsistency in sampling can be overcome with spatio‐temporal modeling to follow species density redistributions. In light of our global assessment, we establish a framework for improving the management and conservation of transboundary and migrating marine demersal species. We provide directions to improve data availability and encourage countries to share survey data, to assess species vulnerabilities, and to support management adaptation in a time of climate‐driven ocean changes.

Cephalopod fisheries have expanded over the last decade. They are characterised by annual uncertainty in yield quantity and quality. This is attributed to changes in environmental conditions such as temperature combined with the semelparous life strategy (one reproductive cycle during life) of the majority of squid species. We determined the effect of environmental temperature on several individual- and population-level characteristics of Illex argentinus, a squid species in the South Atlantic that sustains one of the largest commercial squid resources in the world. The effect of temperature on dorsal mantle length, proportion of mature females, and abundance was determined in the context of the I. argentinus life cycle periods, and migration patterns. This was achieved by performing 520 linear regressions using a 20-year time series of fisheries data and monthly temperature data from the key regions associated with I. argentinus life cycle on the Patagonian Shelf in the Southwest Atlantic. Temperatures above 17.5 °C in the hatching grounds lead to smaller and less mature females in the Falkland Islands waters, during the feeding period. Larger females, a higher proportion of mature and maturing females, and a lower abundance of I. argentinus were found in the Falkland Islands waters when temperatures in the migration areas were higher than 13.5 °C. These findings will aid in the forecasting and assessment for future fishing seasons of this vital squid resource in the Southwest Atlantic.

Marine biota are redistributing at a rapid pace in response to climate change and shifting seascapes. While changes in fish populations and community structure threaten the sustainability of fisheries, our capacity to adapt by tracking and projecting marine species remains a challenge due to data discontinuities in biological observations, lack of data availability, and mismatch between data and real species distributions. To assess the extent of this challenge, we review the global status and accessibility of ongoing scientific bottom trawl surveys. In total, we gathered metadata for 283,925 samples from 95 surveys conducted regularly from 2001 to 2019. We identified that 59% of the metadata collected are not publicly available, highlighting that the availability of data is the most important challenge to assess species redistributions under global climate change. Given that the primary purpose of surveys is to provide independent data to inform stock assessment of commercially important populations, we further highlight that single surveys do not cover the full range of the main commercial demersal fish species. An average of 18 surveys is needed to cover at least 50% of species ranges, demonstrating the importance of combining multiple surveys to evaluate species range shifts. We assess the potential for combining surveys to track transboundary species redistributions and show that differences in sampling schemes and inconsistency in sampling can be overcome with spatio-temporal modeling to follow species density redistributions. In light of our global assessment, we establish a framework for improving the management and conservation of transboundary and migrating marine demersal species. We provide directions to improve data availability and encourage countries to share survey data, to assess species vulnerabilities, and to support management adaptation in a time of climate-driven ocean changes.

Southern blue whiting (Micromesistius australis australis) once contributed to one of the largest finfish fisheries in the Southwest Atlantic. Intense exploitation began in the late 1970s with peak total annual catches attaining 258.000 tonnes in 1983. Continuing levels of exploitation hereafter resulted in a significant reduction in its abundance by the early 1990s and forced the implementation of a suite of conservation measures to rebuild these stocks. Improved recruitment levels in recent years suggests that these measures have been effective. However, more information on habitat use and behaviour during the early life history stages of this fish is required to be able to draw firm conclusions. Here, we use complimentary investigations into otolith microstructure and trace elemental composition (by LA-ICPMS) to study the early stages of ontogeny in M. a. australis. We provide evidentiary support for the formation of daily growth increments on the otoliths of juvenile M. a. australis and utilise these to estimate the age at onset and completion of metamorphosis (30.5 ± 0.3 and 60.7 ± 1.8 days after the first increment formation, respectively). The timing of a newly defined ‘juvenile transition-mark’ (corresponding to the transition from the epipelagic larval habitat to a deeper juvenile habitat) was estimated to form at 76.5 ± 2.0 days after first increment formation, suggesting that early juveniles remain in the epipelagic habitat for over two weeks post-metamorphosis. Significant shifts in element:42Ca ratios were found for elements 24Mg, 55Mn, 88Sr and 138Ba between otolith zones corresponding to different ontogenetic stages: (A) larval-, (B) metamorphosis- and (C) juvenile zone. These shifts could be correlated with changes in behaviour and habitat. Elemental ‘fingerprints’ for each of the three otolith zones were found to be distinct through high classification accuracies of the Random Forest classifier (81.1 ± 0.1 %), with 55Mn:42Ca contributing most to the

South American fur seals (Arctocephalus australis) are widely distributed, yet surprisingly little is known about their ecology. In particular, population data are sparse and outdated for many breeding locations, including the Falkland Islands. Data deficiency impedes the development of coherent conservation and management strategies. To address knowledge gaps, for the first time since 1965 an archipelago‐wide census of South American fur seals breeding at the Falkland Islands was undertaken, which provided the first pup abundance estimate since 1926 – data that are critical for assessing population trends. In total, 36,425 South American fur seal pups were counted at the Falkland Islands in 2018, a greater than four‐fold increase since the last census, and far greater than the 7,990 pups counted in Uruguay, which was presumed to be the largest South American fur seal population in the world. Hence, based on pup abundance, the Falkland Islands is presently the largest population of South American fur seals, even when considering a correction factor of 3.9 that was applied to pup counts in Uruguay, which yielded an estimated 31,160 pups. The results redefine South American fur seal abundance, the contribution of breeding locations (Falkland Islands, Uruguay, Argentina, Chile) and the distribution of breeding colonies at the Falkland Islands, which has far reaching implications for conservation and management. In particular, the present study has effectively doubled the Atlantic population size of the species, which is now estimated to comprise about 76,000 pups, of which the Falkland Islands accounts for 48% and Uruguay 41%. Accordingly, changes in the number of South American fur seals breeding at the Falkland Islands will influence the global population trends and conservation status of the species. Monitoring South American fur seals breeding at the Falkland Islands is therefore crucial to understand the impacts of anthropogenic pressures, such as fisheries, and t

The jumbo squid Dosidicus gigas was recently claimed to he an iteroparous species with ovaries returning to an immature, resting stage after spawning. Analysis of the data and figures presented in two recent articles revealed that this claim was based on misinterpretation of histological information and that Dosidicus is not iteroparous. Having consensus on the reproductive strategy of Dosidicus is important for the management of fisheries for this species.

The Patagonian long-finned squid Doryteuthis gahi is an abundant commercial species within Falkland Island waters. The population consists of two temporally distinct spawning cohorts, inferred to have markedly different patterns of migration and timings of ontogenetic events. Ontogenetic migrations of each cohort were confirmed by analysis of the chemical composition of statoliths collected from both cohorts in two consecutive years. Trace element concentrations were quantified using laser ablation inductively coupled plasma mass spectrometry (LA-ICP-MS), to determine temporal and cohort-specific variation. Individual ablation craters, ablated in a transect from the nucleus to the rostrum edge, were aged to produce high-resolution elemental chronologies. Generalized additive mixed models (GAMM) indicated that cohort and life history stage had a significant effect on Sr/Ca and Ba/Ca ratios. Sr/Ca and Ba/Ca ratios were both negatively correlated with near-bottom water temperature, with Ba/Ca also potentially correlated to depth. Statolith elemental chronologies have useful applications as natural tags, discriminating between spawning cohorts.

Global abundances and commercial fisheries of cephalopods have increased over recent decades, creating a need for effective fishery management. This management is often focused on the ability to ascertain the age structure of key populations. There are several main techniques for age and growth rate determination in cephalopods. Because of biological differences between species groups, not all techniques are applicable for every species. This review outlines the use of five main ageregistering structures (statoliths, gladii, beaks, stylets, and eye lenses) along with one chemical aging technique (lipofuscin) and their application to cephalopod species groups.

Human activities have substantially changed the world’s oceans in recent decades, altering marine food webs, habitats and biogeochemical processes. Cephalopods (squid, cuttlefish and octopuses) have a unique set of biological traits, including rapid growth, short lifespans and strong life-history plasticity, allowing them to adapt quickly to changing environmental conditions. There has been growing speculation that cephalopod populations are proliferating in response to a changing environment, a perception fuelled by increasing trends in cephalopod fisheries catch. To investigate long-term trends in cephalopod abundance, we assembled global time-series of cephalopod catch rates (catch per unit of fishing or sampling effort). We show that cephalopod populations have increased over the last six decades, a result that was remarkably consistent across a highly diverse set of cephalopod taxa. Positive trends were also evident for both fisheries-dependent and fisheries-independent time-series, suggesting that trends are not solely due to factors associated with developing fisheries. Our results suggest that large-scale, directional processes, common to a range of coastal and oceanic environments, are responsible. This study presents the first evidence that cephalopod populations have increased globally, indicating that these ecologically and commercially important invertebrates may have benefited from a changing ocean environment

Some 290 species of squids comprise the order Teuthida that belongs to the molluscan Class Cephalopoda. Of these, about 30–40 squid species have substantial commercial importance around the world. Squid fisheries make a rather small contribution to world landings from capture fisheries relative to that of fish, but the proportion has increased steadily over the last decade, with some signs of recent leveling off. The present overview describes all substantial squid fisheries around the globe. The main ecological and biological features of exploited stocks, and key aspects of fisheries management are presented for each commercial species of squid worldwide. The history and fishing methods used in squid fisheries are also described. Special attention has been paid to interactions between squid fisheries and marine ecosystems including the effects of fishing gear, the role of squid in ecosystem change induced by overfishing on groundfish, and ecosystem-based fishery management.

Cephalopods are a relatively small class of molluscs (~ 800 species), but they support some large industrial scale fisheries and numerous small-scale, local, artisanal fisheries. For several decades, landings of cephalopods globally have grown against a background of total finfish landings levelling off and then declining. There is now evidence that in recent years, growth in cephalopod landings has declined. The commercially exploited cephalopod species are fast-growing, short-lived ecological opportunists. Annual variability in abundance is strongly influenced by environmental variability, but the underlying causes of the links between environment and population dynamics are poorly understood. Stock assessment models have recently been developed that incorporate environmental processes that drive variability in recruitment, distribution and migration patterns. These models can be expected to improve as more, and better, data are obtained on environmental effects and as techniques for stock identification improve. A key element of future progress will be improved understanding of trophic dynamics at all phases in the cephalopod life cycle. In the meantime, there is no routine stock assessment in many targeted fisheries or in the numerous by-catch fisheries for cephalopods. There is a particular need for a precautionary approach in these cases. Assessment in many fisheries is complicated because cephalopods are ecological opportunists and stocks appear to have benefited from the reduction of key predator by overexploitation. Because of the complexities involved, ecosystem-based fisheries management integrating social, economic and ecological considerations is desirable for cephalopod fisheries. An ecological approach to management is routine in many fisheries, but to be effective, good scientific understanding of the relationships between the environment, trophic dynamics and population dynamics is essential. Fisheries and the ecosystems they depend on can only be m

Doryteuthis gahi (Orbigny, 1835) is a relatively small squid typically attaining 13–17 cm mantle length that inhabits the shelves around the southern tip of South America from southern Peru in the Pacific to southern Argentina and the Falkland Islands in the Atlantic. It is most abundant around the Falkland Islands, where it is a subject of important commercial fishery with a total annual catch around 50,000 t. Among Loliginidae, D. gahi is the coldest water species associated with mixed waters of temperate and Sub-Antarctic origin. The squid spawns at water temperatures between 4 and 11°C, with embryogenesis taking between 1.5 months in spring-summer to 4.5 months in winter. Population structure consists of two cohorts that differ by spawning season (autumn-spawning and spring-spawning squid), extent of offshore migrations and fecundity. Both cohorts have annual life cycle, with high growth rates best described by Shnute growth function. Main prey of D. gahi are planktonic crustaceans; euphausiids and pelagic amphipod Themisto guadichaudii. Large animals also cannibalize on smaller squid. Doryteuthis gahi is an important prey for most nektonic fishes, sea birds and mammals inhabiting Patagonian Shelf.

Illex argentinus, a close relative of the other North Atlantic Illex species, concentrates on the Patagonian shelf edge and spreads over the shelf from Southern Brazil to the Falkland Islands. It supports one of the world’s largest squid fisheries. The fishery mostly exploits the winter spawning, south Patagonian stock, which is more abundant, grows to a larger body size and extends further south than the summer spawners. Spawning takes place in the northern part of the range and the eggs hatch into a typical ommastrephid rhynchoteuthon paralarva. I. argentinus is short-lived and semelparous living approximately one year, at the end of which the squid die after spawning. Growth is rapid and the largest individuals - females from the South Patagonian, winter spawning stock - reach a mean mantle length of 330 mm (maximum of 400 mm ML) when fully grown. Large scale migrations between the spawning grounds and the feeding grounds, and back again, over the one year life cycle are accompanied by diel vertical migrations. Immature and maturing squid occur 3 - 20 m off the bottom during the day but at night they ascend to 5 - 20 m over the shelf and to 20 - 200 m beyond the shelf break. Mature squid of the South Patagonian Stock migrate northward along the continental slope to the spawning grounds in May – July remaining close to the sea bed (500 - 900 m) at night and ascend to 200-300 m above the bottom during the day. The paralarvae are thought to feed using their proboscis, on body mucus enriched with microorganisms and other food particles that stick to it. Juveniles and adults are opportunistic predators feeding on fishes, crustaceans, and cephalopods including smaller conspecifics. The diet generally reflects the plankton and nekton available. Small quid < 200 mm ML eat only crustaceans but may switch increasingly to fish as they grow. Cannibalism is a feature of the largest squids. Overall, crustaceans (euphausiids and pelagic amphipods) are the main prey, representin

This project aimed to the development of the research and the technology necessary to promote higher added value to fishing activity. This is to be achieved by obtaining profit from a finfish species (“Rockcod”, Patagonotothen spp.) not known to consumers and currently discarded by the EU fishing fleet operating in the South West Atlantic, in order to supply the EU seafood industry with a good quality raw material for human food manufacturing. Use of this species, caught as a by-catch in the existing fisheries targeting hakes and cephalopods, should also increase the profitability of the fleet, contribute to maintaining employment and help to counterbalance the negative effects of fishing activity and discards in the ecosystem. The main scientific-technological objectives and expected achievements were the following: - Description of the fisheries - Improved knowledge of the biology of the species - Biomass assessment - Estimation of catches and discards - Analysis of the spatial and temporal distribution of the resource. Fishery forecasting and testing - Sensorial, Microbiological, Nutritional and Biochemical Evaluation of Rock cod - Development of the technical modifications on board commercial vessels - Development of new processed products from frozen Rock cod

The Argentine shortfin squid (Illex argentinus) is a common neritic species occurring in waters off Brazil, Uruguay, Argentina, and the Falkland/Malvinas Islands in the southwest Atlantic. Illex is the most important cephalopod species in the area and plays a significant role in the ecosystem. It is object of major fisheries using both trawlers (mostly from European countries) and jigging vessels (mainly from Asian countries) and the actual total annual catch could reach up to 700 thousand tons. Fishery and biological information collected by scientific observers aboard commercial trawlers between 1988 and 2003 was analysed in relation to physical and environmental factors to establish the spatio-temporal pattern of the species distribution. The data included 26 168 fishing haul records, of which 11103 were positive. CPUE (Catch Per Unit Effort, kg⋅hr-1) was used as abundance index. The analyses of the general spatio-temporal pattern of fish abundance, and the influence of environmental factors, such as SST, SBT and depth on squid abundance and distribution, was based on correlation, variograms, and time-series maps created using GIS. The areas of the highest densities were found in deep waters of the High Seas between 44.5º S – 47.0º S outside the Argentinean EEZ and to the north-west of the Islands in February–May. The correlations between squid abundance and cloud index at different moon phases were also analyzed.

The reproductive biology of one of the most abundant notothenioids, Patagonotothen ramsayi, was investigated between February 2003 and November 2004 on the Falkland and Patagonian Shelves (Southwest Atlantic). Male and female P. ramsayi were mature at 27.6 and 24.8 cm LT, respectively. P. ramsayi is a total spawner, with a total fecundity ranging between 24,300 and 76,700 eggs. Spawning occurs on the shelf breaks between June and August with the peak in gonado-somatic indices in June. Analysis of length frequency distributions over the year and sex ratios of mature fish during the spawning season may indicate the presence of a nesting and nest guarding behaviour in male fish, similar to other rockcods. Features of its reproductive strategy, which enabled P. ramsayi to dominate the medium-sized demersal fishes on the Patagonian shelf are discussed and compared with those of other nototheniids and cottid sculpins from the Northern Hemisphere.