The vast frozen worlds of the Polar Regions are a major component of the Earth’s global climate s... more The vast frozen worlds of the Polar Regions are a major component of the Earth’s global climate system. The polar oceans are amongst the least understood environments on our planet. They respond to global temperature change; absorb heat and carbon from the atmosphere, including that produced by humans; they sustain millions of seabirds, whales and fish; and provide food for a hungry world. These oceans keep our planet cool and supply other oceans with nutrients. But, because of their remoteness and inhospitable nature, data coverage is extremely sparse. Understanding the polar oceans is absolutely key to understanding the big questions about our global environment. By working together scientists create observing systems to collect and interpret crucial scientific data that shapes policy, protects the environment and ultimately improves people’s lives. Recent technological advances mean that scientists can now combine high-quality land and ship-based observations with high-quality sa...
Exploitation is one of the major drivers of change in marine ecosystems. Following discovery in 1... more Exploitation is one of the major drivers of change in marine ecosystems. Following discovery in 1775, South Georgia saw sequential overexploitation of living resources, including seals, whales, and fish. Although exploitation is now tightly regulated, the ecosystem is still recovering. Marbled rockcod, Notothenia rossii (Richardson 1844), was the first fish species to be commercially exploited and high catches between 1967 and 1972 resulted in dramatic stock decline. Here, we use 30 years of trawl survey data to provide the first evidence of a sustained increase in the N. rossii population starting two decades after the prohibition of targeted fishing in 1985. The way species respond to change is mediated in part by trophic relationships with other organisms. We present the first multi-year, spatially-resolved comparison of adult N. rossii diet at South Georgia, highlighting a variable diet with less reliance on Antarctic krill than previously thought. Life history factors and possi...
This is an open access article under the terms of the Creative Commons Attribution License, which... more This is an open access article under the terms of the Creative Commons Attribution License, which permits use, distribution and reproduction in any medium, provided the original work is properly cited.
As the role of mercury is poorly known in Southern Ocean biota, the total mercury (T-Hg) concentr... more As the role of mercury is poorly known in Southern Ocean biota, the total mercury (T-Hg) concentrations were evaluated in upper/lower beaks, digestive gland, gills and mantle muscle of Adelieledone polymorpha and Pareledone turqueti, two of the most abundant octopod species around South Georgia. Beaks had the lowest T-Hg concentrations (A. polymorpha: [T-Hg] Upper = 27.2 ± 12.9 ng•g −1 and [T-Hg] Lower = 27.5 ± 20.0 ng•g −1 ; P. turqueti: [T-Hg] Upper = 34.6 ± 13.9 ng•g −1 and [T-Hg] Lower = 56.8 ± 42.0 ng•g −1), followed by gills and muscle. The highest values were recorded in the digestive gland (A. polymorpha: 251.6 ± 69.7 ng•g −1 ; P. turqueti: 347.0 ± 177.0 ng•g −1). Significant relationships were found between the concentrations of T-Hg in the beaks and muscle of A. polymorpha (T-Hg in muscle is 10 times higher than in beaks). This study shows that beaks can be used as proxy for T-Hg in muscle for some octopod species, and a helpful tool for estimating total Hg body burden from beaks.
AimMarine protected areas can serve to regulate harvesting and conserve biodiversity. Within larg... more AimMarine protected areas can serve to regulate harvesting and conserve biodiversity. Within large multi‐use MPAs, it is often unclear to what degree critical sites of biodiversity are afforded protection against commercial activities. Addressing this issue is a prerequisite if we are to appropriately assess sites against conservation targets. We evaluated whether the management regime of a large MPA conserved sites (Key Biodiversity Areas, KBAs) supporting the global persistence of top marine predators.LocationSouthwest Atlantic Ocean.MethodWe collated population and tracking data (1,418 tracks) from 14 marine predator species (Procellariiformes, Sphenisciformes, Pinnipedia) that breed at South Georgia and the South Sandwich Islands, and identified hotspots for their conservation under the recently developed KBA framework. We then evaluated the spatiotemporal overlap of these sites and the different management regimes of krill, demersal longline and pelagic trawl fisheries operatin...
The Antarctic is considered to be a pristine environment relative to other regions of the Earth, ... more The Antarctic is considered to be a pristine environment relative to other regions of the Earth, but it is increasingly vulnerable to invasions by marine, freshwater and terrestrial non‐native species. The Antarctic Peninsula region (APR), which encompasses the Antarctic Peninsula, South Shetland Islands and South Orkney Islands, is by far the most invaded part of the Antarctica continent. The risk of introduction of invasive non‐native species to the APR is likely to increase with predicted increases in the intensity, diversity and distribution of human activities. Parties that are signatories to the Antarctic Treaty have called for regional assessments of non‐native species risk. In response, taxonomic and Antarctic experts undertook a horizon scanning exercise using expert opinion and consensus approaches to identify the species that are likely to present the highest risk to biodiversity and ecosystems within the APR over the next 10 years. One hundred and three species, currentl...
In the marine environment, understanding the biophysical mechanisms that drive variability in lar... more In the marine environment, understanding the biophysical mechanisms that drive variability in larval dispersal and population connectivity is essential for estimating the potential impacts of climate change on the resilience and genetic structure of populations. Species whose populations are small, isolated and discontinuous in distribution will differ fundamentally in their response and resilience to environmental stress, compared with species that are broadly distributed, abundant and frequently exchange conspecifics. Here, we use an individual-based modelling approach, combined with a population genetics projection model, to consider the impacts of a warming climate on the population connectivity of two contrasting Antarctic fish species, and . Focussing on the Scotia Sea region, sea surface temperatures are predicted to increase significantly by the end of the 21st century, resulting in reduced planktonic duration and increased egg and larval mortality. With shorter planktonic d...
Myctophid fish play an important role in the Southern Ocean pelagic food web. The rhombic lantern... more Myctophid fish play an important role in the Southern Ocean pelagic food web. The rhombic lanternfish Krefftichthys anderssoni is one of the most common myctophids in the region, but its ecology is poorly known. This study examines spatial and temporal patterns in the species distribution of abundance, life cycle, population structure and diet using samples collected by mid-water trawl nets deployed in different seasons across the Scotia Sea. Virtually absent from the sea-ice zone, the species was most abundant in the northern Scotia Sea around the Georgia Basin at depths below 400 m associated with the Circumpolar Deep Water. The species migrates during night to the upper 400 m following their main preys: the copepods Rhincalanus gigas and Calanoides acutus, and euphausiids of genus Thysanoessa. Larvae length distribution and post-larvae length frequency analysis suggested a life cycle of ≈ 3 years with spawning and recruitment strongly connected with the APF and the South Georgia shelf. Spatial distribution, population structure and diet changed both seasonally and ontogenetically. To date, the present study is the most comprehensive for K. anderssoni
This research is the first to investigate deepwater demersal fish distribution and community stru... more This research is the first to investigate deepwater demersal fish distribution and community structure around South Georgia and Shag Rocks. Analysis of catch data from a trawl survey conducted in 2003 indicated that depth and location have a marked influence over demersal fish community structure in the region. Three distinct, depth stratified fish assemblages were observed. The demersal fish assemblage found on the shelf to depths of around 400m was dominated by nototheniids and was comprised largely of species endemic to the Southern Ocean and Scotia Sea. At the greatest depths sampled (>600m) the demersal fish community was dominated by gadiform fishes including members of the Macrouridae and Moridae, many of which are not endemic to the Southern Ocean. From 400-600m there was a transitional zone with demersal fish representatives of both the shelf and deeper slope communities. Clear geographic differences in the shelf community were apparent with differences observed in community structure between South Georgia and Shag Rocks to depths of around 400m. These data provide valuable baseline information to aid environmental management decisions and assess potential impacts of rapid ocean warming around South Georgia.
The Patagonian toothfish, Dissostichus eleginoides, is a valuable fishery species and has a disco... more The Patagonian toothfish, Dissostichus eleginoides, is a valuable fishery species and has a discontinuous distribution across the Southern Ocean. Identification of the genetic stock structure of toothfish would allow evaluation of the suitability of the spatial scale at which fisheries management operates. Genetic subdivision seems likely given the species distribution. Population genetics studies of this species have been performed; however, they have been limited by sample size, spatial coverage and/or the type of markers investigated. As a potential solution, we developed methods for extracting toothfish DNA from otoliths that are available in large numbers from collections held at several research institutes. Genetic differentiation between the three oceanic sectors was investigated. Four mitochondrial and four nuclear markers with multiple single nucleotide polymorphisms were sequenced by high throughput sequencing for samples from six locations. Genetic differentiation was fou...
<p><i>Paralomis anamerae</i> (A – Red circle), <i>Lithodes macquariae<... more <p><i>Paralomis anamerae</i> (A – Red circle), <i>Lithodes macquariae</i> (A – Blue square), <i>Kiwa sp</i>. (B – Red circle), <i>Paralomis elongata</i> (B – Blue square), <i>Thymopsis nilenta</i> (C), <i>Thymopides grobovi</i> (D – Green triangle), <i>Paralomis aculeata</i> (D – Blue squares) and <i>Neolithodes duhameli</i> (D – Red circle). Red line = Mean position of Polar Front (Moore et al., 1999).</p
Predatory interaction of marine mammals with longline fisheries is observed globally, leading to ... more Predatory interaction of marine mammals with longline fisheries is observed globally, leading to partial or complete loss of the catch and in some parts of the world to considerable financial loss. Depredation can also create additional unrecorded fishing mortality of a stock and has the potential to introduce bias to stock assessments. Here we aim to characterise depredation in the Patagonian toothfish (Dissostichus eleginoides) fishery around South Georgia focusing on the spatio-temporal component of these interactions. Antarctic fur seals (Arctocephalus gazella), sperm whales (Physeter macrocephalus), and orcas (Orcinus orca) frequently feed on fish hooked on longlines around South Georgia. A third of longlines encounter sperm whales, but loss of catch due to sperm whales is insignificant when compared to that due to orcas, which interact with only 5% of longlines but can take more than half of the catch in some cases. Orca depredation around South Georgia is spatially limited an...
Members of the anomuran crustacean family Lithodidae (commonly known as stone crabs or king crabs... more Members of the anomuran crustacean family Lithodidae (commonly known as stone crabs or king crabs) are distributed globally in the deep sea, with a few genera occurring inter-tidally at high latitudes in the northern hemisphere (Thatje et al., 2005; Hall and Thatje, 2009). Lithodids occupy predominantly cold water habitats and temperature is thought to be a constraining factor in their distribution. Lower and upper thermal limits of approximately 0.5°C and 15°C respectively govern their distribution (Thatje and Arntz, 2003; Hall and Thatje, 2011). Lithodids support important fisheries in higher-latitude regions of both the northern and southern hemisphere. Valuable fisheries, including the red king crab (Paralithodes camtschaticus) and golden king crab fisheries of the northern Pacific and the 'centolla' (Lithodes santolla) fisheries of southern South America, have developed in recent decades (Otto and MacIntosh, 1996). However, overfishing of lithodid resources has been widespread leading to a major decline in catches in many regions (Lovrich, 1997; Zaklan, 2002). Lithodids occur in both the Antarctic and sub-Antarctic regions but in the former their distribution is restricted to areas of warmer water
Notothenia rossii was the fi rst target species in Southern Ocean fi sheries. The species was alr... more Notothenia rossii was the fi rst target species in Southern Ocean fi sheries. The species was already heavily fi shed at the beginning of the 1970s. The closure of the fi shery for this species in 1985 was one of the fi rst conservation measures adopted by CCAMLR. Fish biomass within a CCAMLR subarea or part of a subarea is commonly estimated from surveys that target a number of species, including N. rossii, at the same time. These surveys are conducted under the assumption that the target fi sh species are more or less evenly distributed over the area at the time of the survey. This assumption is violated in the case of N. rossii, which is non-randomly distributed such that a large proportion of the population tends to aggregate in small areas, leaving most of the survey area only thinly populated. In order to provide more accurate estimates of the abundance of the species, it is suggested that an acoustic survey combined with a number of identifi cation hauls might be the most promising approach to estimating the biomass of N. rossii. Résumé Notothenia rossii, première espèce visée par la pêche dans l'océan Austral, faisait déjà l'objet d'une exploitation intensive au début des années 1970. La fermeture de la pêche de cette espèce en 1985 faisait partie des premières mesures de conservation adoptées par la CCAMLR. En général, la biomasse de poisson dans une sous-zone de la CCAMLR, ou dans un secteur d'une telle sous-zone, est estimée au moyen de campagnes d'évaluation visant à la fois plusieurs espèces-dont N. rossii. Il est présumé que la répartition des espèces de poisson visées est plus ou moins uniforme dans toute la région à l'époque de la campagne. Dans le cas de N. rossii, dont la distribution est non aléatoire, au point qu'une grande proportion de la population tend à se concentrer dans des secteurs limités, laissant le reste de la zone d'étude très peu peuplé, cette hypothèse est démentie. Il est suggéré, afi n d'estimer avec davantage de précision l'abondance de N. rossii, de suivre l'approche la plus prometteuse, celle qui consiste à adjoindre à une campagne d'évaluation acoustique plusieurs traits d'identifi cation.
The vast frozen worlds of the Polar Regions are a major component of the Earth’s global climate s... more The vast frozen worlds of the Polar Regions are a major component of the Earth’s global climate system. The polar oceans are amongst the least understood environments on our planet. They respond to global temperature change; absorb heat and carbon from the atmosphere, including that produced by humans; they sustain millions of seabirds, whales and fish; and provide food for a hungry world. These oceans keep our planet cool and supply other oceans with nutrients. But, because of their remoteness and inhospitable nature, data coverage is extremely sparse. Understanding the polar oceans is absolutely key to understanding the big questions about our global environment. By working together scientists create observing systems to collect and interpret crucial scientific data that shapes policy, protects the environment and ultimately improves people’s lives. Recent technological advances mean that scientists can now combine high-quality land and ship-based observations with high-quality sa...
Exploitation is one of the major drivers of change in marine ecosystems. Following discovery in 1... more Exploitation is one of the major drivers of change in marine ecosystems. Following discovery in 1775, South Georgia saw sequential overexploitation of living resources, including seals, whales, and fish. Although exploitation is now tightly regulated, the ecosystem is still recovering. Marbled rockcod, Notothenia rossii (Richardson 1844), was the first fish species to be commercially exploited and high catches between 1967 and 1972 resulted in dramatic stock decline. Here, we use 30 years of trawl survey data to provide the first evidence of a sustained increase in the N. rossii population starting two decades after the prohibition of targeted fishing in 1985. The way species respond to change is mediated in part by trophic relationships with other organisms. We present the first multi-year, spatially-resolved comparison of adult N. rossii diet at South Georgia, highlighting a variable diet with less reliance on Antarctic krill than previously thought. Life history factors and possi...
This is an open access article under the terms of the Creative Commons Attribution License, which... more This is an open access article under the terms of the Creative Commons Attribution License, which permits use, distribution and reproduction in any medium, provided the original work is properly cited.
As the role of mercury is poorly known in Southern Ocean biota, the total mercury (T-Hg) concentr... more As the role of mercury is poorly known in Southern Ocean biota, the total mercury (T-Hg) concentrations were evaluated in upper/lower beaks, digestive gland, gills and mantle muscle of Adelieledone polymorpha and Pareledone turqueti, two of the most abundant octopod species around South Georgia. Beaks had the lowest T-Hg concentrations (A. polymorpha: [T-Hg] Upper = 27.2 ± 12.9 ng•g −1 and [T-Hg] Lower = 27.5 ± 20.0 ng•g −1 ; P. turqueti: [T-Hg] Upper = 34.6 ± 13.9 ng•g −1 and [T-Hg] Lower = 56.8 ± 42.0 ng•g −1), followed by gills and muscle. The highest values were recorded in the digestive gland (A. polymorpha: 251.6 ± 69.7 ng•g −1 ; P. turqueti: 347.0 ± 177.0 ng•g −1). Significant relationships were found between the concentrations of T-Hg in the beaks and muscle of A. polymorpha (T-Hg in muscle is 10 times higher than in beaks). This study shows that beaks can be used as proxy for T-Hg in muscle for some octopod species, and a helpful tool for estimating total Hg body burden from beaks.
AimMarine protected areas can serve to regulate harvesting and conserve biodiversity. Within larg... more AimMarine protected areas can serve to regulate harvesting and conserve biodiversity. Within large multi‐use MPAs, it is often unclear to what degree critical sites of biodiversity are afforded protection against commercial activities. Addressing this issue is a prerequisite if we are to appropriately assess sites against conservation targets. We evaluated whether the management regime of a large MPA conserved sites (Key Biodiversity Areas, KBAs) supporting the global persistence of top marine predators.LocationSouthwest Atlantic Ocean.MethodWe collated population and tracking data (1,418 tracks) from 14 marine predator species (Procellariiformes, Sphenisciformes, Pinnipedia) that breed at South Georgia and the South Sandwich Islands, and identified hotspots for their conservation under the recently developed KBA framework. We then evaluated the spatiotemporal overlap of these sites and the different management regimes of krill, demersal longline and pelagic trawl fisheries operatin...
The Antarctic is considered to be a pristine environment relative to other regions of the Earth, ... more The Antarctic is considered to be a pristine environment relative to other regions of the Earth, but it is increasingly vulnerable to invasions by marine, freshwater and terrestrial non‐native species. The Antarctic Peninsula region (APR), which encompasses the Antarctic Peninsula, South Shetland Islands and South Orkney Islands, is by far the most invaded part of the Antarctica continent. The risk of introduction of invasive non‐native species to the APR is likely to increase with predicted increases in the intensity, diversity and distribution of human activities. Parties that are signatories to the Antarctic Treaty have called for regional assessments of non‐native species risk. In response, taxonomic and Antarctic experts undertook a horizon scanning exercise using expert opinion and consensus approaches to identify the species that are likely to present the highest risk to biodiversity and ecosystems within the APR over the next 10 years. One hundred and three species, currentl...
In the marine environment, understanding the biophysical mechanisms that drive variability in lar... more In the marine environment, understanding the biophysical mechanisms that drive variability in larval dispersal and population connectivity is essential for estimating the potential impacts of climate change on the resilience and genetic structure of populations. Species whose populations are small, isolated and discontinuous in distribution will differ fundamentally in their response and resilience to environmental stress, compared with species that are broadly distributed, abundant and frequently exchange conspecifics. Here, we use an individual-based modelling approach, combined with a population genetics projection model, to consider the impacts of a warming climate on the population connectivity of two contrasting Antarctic fish species, and . Focussing on the Scotia Sea region, sea surface temperatures are predicted to increase significantly by the end of the 21st century, resulting in reduced planktonic duration and increased egg and larval mortality. With shorter planktonic d...
Myctophid fish play an important role in the Southern Ocean pelagic food web. The rhombic lantern... more Myctophid fish play an important role in the Southern Ocean pelagic food web. The rhombic lanternfish Krefftichthys anderssoni is one of the most common myctophids in the region, but its ecology is poorly known. This study examines spatial and temporal patterns in the species distribution of abundance, life cycle, population structure and diet using samples collected by mid-water trawl nets deployed in different seasons across the Scotia Sea. Virtually absent from the sea-ice zone, the species was most abundant in the northern Scotia Sea around the Georgia Basin at depths below 400 m associated with the Circumpolar Deep Water. The species migrates during night to the upper 400 m following their main preys: the copepods Rhincalanus gigas and Calanoides acutus, and euphausiids of genus Thysanoessa. Larvae length distribution and post-larvae length frequency analysis suggested a life cycle of ≈ 3 years with spawning and recruitment strongly connected with the APF and the South Georgia shelf. Spatial distribution, population structure and diet changed both seasonally and ontogenetically. To date, the present study is the most comprehensive for K. anderssoni
This research is the first to investigate deepwater demersal fish distribution and community stru... more This research is the first to investigate deepwater demersal fish distribution and community structure around South Georgia and Shag Rocks. Analysis of catch data from a trawl survey conducted in 2003 indicated that depth and location have a marked influence over demersal fish community structure in the region. Three distinct, depth stratified fish assemblages were observed. The demersal fish assemblage found on the shelf to depths of around 400m was dominated by nototheniids and was comprised largely of species endemic to the Southern Ocean and Scotia Sea. At the greatest depths sampled (>600m) the demersal fish community was dominated by gadiform fishes including members of the Macrouridae and Moridae, many of which are not endemic to the Southern Ocean. From 400-600m there was a transitional zone with demersal fish representatives of both the shelf and deeper slope communities. Clear geographic differences in the shelf community were apparent with differences observed in community structure between South Georgia and Shag Rocks to depths of around 400m. These data provide valuable baseline information to aid environmental management decisions and assess potential impacts of rapid ocean warming around South Georgia.
The Patagonian toothfish, Dissostichus eleginoides, is a valuable fishery species and has a disco... more The Patagonian toothfish, Dissostichus eleginoides, is a valuable fishery species and has a discontinuous distribution across the Southern Ocean. Identification of the genetic stock structure of toothfish would allow evaluation of the suitability of the spatial scale at which fisheries management operates. Genetic subdivision seems likely given the species distribution. Population genetics studies of this species have been performed; however, they have been limited by sample size, spatial coverage and/or the type of markers investigated. As a potential solution, we developed methods for extracting toothfish DNA from otoliths that are available in large numbers from collections held at several research institutes. Genetic differentiation between the three oceanic sectors was investigated. Four mitochondrial and four nuclear markers with multiple single nucleotide polymorphisms were sequenced by high throughput sequencing for samples from six locations. Genetic differentiation was fou...
<p><i>Paralomis anamerae</i> (A – Red circle), <i>Lithodes macquariae<... more <p><i>Paralomis anamerae</i> (A – Red circle), <i>Lithodes macquariae</i> (A – Blue square), <i>Kiwa sp</i>. (B – Red circle), <i>Paralomis elongata</i> (B – Blue square), <i>Thymopsis nilenta</i> (C), <i>Thymopides grobovi</i> (D – Green triangle), <i>Paralomis aculeata</i> (D – Blue squares) and <i>Neolithodes duhameli</i> (D – Red circle). Red line = Mean position of Polar Front (Moore et al., 1999).</p
Predatory interaction of marine mammals with longline fisheries is observed globally, leading to ... more Predatory interaction of marine mammals with longline fisheries is observed globally, leading to partial or complete loss of the catch and in some parts of the world to considerable financial loss. Depredation can also create additional unrecorded fishing mortality of a stock and has the potential to introduce bias to stock assessments. Here we aim to characterise depredation in the Patagonian toothfish (Dissostichus eleginoides) fishery around South Georgia focusing on the spatio-temporal component of these interactions. Antarctic fur seals (Arctocephalus gazella), sperm whales (Physeter macrocephalus), and orcas (Orcinus orca) frequently feed on fish hooked on longlines around South Georgia. A third of longlines encounter sperm whales, but loss of catch due to sperm whales is insignificant when compared to that due to orcas, which interact with only 5% of longlines but can take more than half of the catch in some cases. Orca depredation around South Georgia is spatially limited an...
Members of the anomuran crustacean family Lithodidae (commonly known as stone crabs or king crabs... more Members of the anomuran crustacean family Lithodidae (commonly known as stone crabs or king crabs) are distributed globally in the deep sea, with a few genera occurring inter-tidally at high latitudes in the northern hemisphere (Thatje et al., 2005; Hall and Thatje, 2009). Lithodids occupy predominantly cold water habitats and temperature is thought to be a constraining factor in their distribution. Lower and upper thermal limits of approximately 0.5°C and 15°C respectively govern their distribution (Thatje and Arntz, 2003; Hall and Thatje, 2011). Lithodids support important fisheries in higher-latitude regions of both the northern and southern hemisphere. Valuable fisheries, including the red king crab (Paralithodes camtschaticus) and golden king crab fisheries of the northern Pacific and the 'centolla' (Lithodes santolla) fisheries of southern South America, have developed in recent decades (Otto and MacIntosh, 1996). However, overfishing of lithodid resources has been widespread leading to a major decline in catches in many regions (Lovrich, 1997; Zaklan, 2002). Lithodids occur in both the Antarctic and sub-Antarctic regions but in the former their distribution is restricted to areas of warmer water
Notothenia rossii was the fi rst target species in Southern Ocean fi sheries. The species was alr... more Notothenia rossii was the fi rst target species in Southern Ocean fi sheries. The species was already heavily fi shed at the beginning of the 1970s. The closure of the fi shery for this species in 1985 was one of the fi rst conservation measures adopted by CCAMLR. Fish biomass within a CCAMLR subarea or part of a subarea is commonly estimated from surveys that target a number of species, including N. rossii, at the same time. These surveys are conducted under the assumption that the target fi sh species are more or less evenly distributed over the area at the time of the survey. This assumption is violated in the case of N. rossii, which is non-randomly distributed such that a large proportion of the population tends to aggregate in small areas, leaving most of the survey area only thinly populated. In order to provide more accurate estimates of the abundance of the species, it is suggested that an acoustic survey combined with a number of identifi cation hauls might be the most promising approach to estimating the biomass of N. rossii. Résumé Notothenia rossii, première espèce visée par la pêche dans l'océan Austral, faisait déjà l'objet d'une exploitation intensive au début des années 1970. La fermeture de la pêche de cette espèce en 1985 faisait partie des premières mesures de conservation adoptées par la CCAMLR. En général, la biomasse de poisson dans une sous-zone de la CCAMLR, ou dans un secteur d'une telle sous-zone, est estimée au moyen de campagnes d'évaluation visant à la fois plusieurs espèces-dont N. rossii. Il est présumé que la répartition des espèces de poisson visées est plus ou moins uniforme dans toute la région à l'époque de la campagne. Dans le cas de N. rossii, dont la distribution est non aléatoire, au point qu'une grande proportion de la population tend à se concentrer dans des secteurs limités, laissant le reste de la zone d'étude très peu peuplé, cette hypothèse est démentie. Il est suggéré, afi n d'estimer avec davantage de précision l'abondance de N. rossii, de suivre l'approche la plus prometteuse, celle qui consiste à adjoindre à une campagne d'évaluation acoustique plusieurs traits d'identifi cation.
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