The global importance of mesopelagic fish is increasingly recognised, but they remain poorly studied. This is particularly true in the Southern Ocean, where mesopelagic fishes are both key predators and prey, but where the remote environment makes sampling challenging. Despite this, multiple national Antarctic research programs have undertaken regional sampling of mesopelagic fish over several decades. However, data are dispersed, and sampling methodologies often differ precluding comparisons and limiting synthetic analyses. We identified potential data holders by compiling a metadata catalogue of existing survey data for Southern Ocean mesopelagic fishes. Data holders contributed 17,491 occurrence and 11,190 abundance records from 4780 net hauls from 72 different research cruises. Data span across 37 years from 1991 to 2019 and include trait-based information (length, weight, maturity). The final dataset underwent quality control processes and detailed metadata was provided for each sampling event. This dataset can be accessed through Zenodo. Myctobase will enhance research capacity by providing the broadscale baseline data necessary for observing and modelling mesopelagic fishes.

Abstract While there is now strong evidence that many factors can shape dispersal, the mechanisms influencing connectivity patterns are species‐specific and remain largely unknown for many species with a high dispersal potential. The rock lobsters Jasus tristani and Jasus paulensis have a long pelagic larval duration (up to 20 months) and inhabit seamounts and islands in the southern Atlantic and Indian Oceans, respectively. We used a multidisciplinary approach to assess the genetic relationships between J. tristani and J. paulensis, investigate historic and contemporary gene flow, and inform fisheries management. Using 17,256 neutral single nucleotide polymorphisms we found low but significant genetic differentiation. We show that patterns of connectivity changed over time in accordance with climatic fluctuations. Historic migration estimates showed stronger connectivity from the Indian to the Atlantic Ocean (influenced by the Agulhas Leakage). In contrast, the individual‐based model coupled with contemporary migration estimates inferred from genetic data showed stronger inter‐ocean connectivity in the opposite direction from the Atlantic to the Indian Ocean driven by the Subtropical Front. We suggest that the J. tristani and J. paulensis historical distribution might have extended further north (when water temperatures were lower) resulting in larval dispersal between the ocean basis being more influenced by the Agulhas Leakage than the Subtropical Front. As water temperatures in the region increase in accordance with anthropogenic climate change, a southern shift in the distribution range of J. tristani and J. paulensis could further reduce larval transport from the Indian to the Atlantic Ocean, adding complexity to fisheries management.

The scientific monitoring of the Southern Ocean French fishing industry is based on the use the Pecheker database. Pecheker is dedicated to the digital curation of the data collected on field by scientific observers and which analysis allows the scientists of the Muséum national d’Histoire naturelle institution to provide guidelines and advice for the regulation of the fishing activity, the protection of the fish stocks and the protection of the marine ecosystems. The template of Pecheker has been developed to make the database adapted to the ecosystem-based management concept. Considering the global context of biodiversity erosion, this modern approach of management aims to take account of the environmental background of the fisheries to ensure their sustainable development. Completeness and high quality of the raw data is a key element for an ecosystem-based management database such as Pecheker. Here, we present the development of this database as a case study of fisheries data curation to be shared with the readers. Full code to deploy a database based on the Pecheker template is provided in supplementary materials. Considering the success factors we could identify, we propose a discussion about how the community could build a global fisheries information system based on a network of small databases including interoperability standards.

Investigating historical gene flow in species complexes can indicate how environmental and reproductive barriers shape genome divergence during speciation. The processes influencing species diversification under environmental change remain one of the central focal points of evolutionary biology, particularly for marine organisms with high dispersal potential. We investigated genome-wide divergence, introgression patterns and inferred demographic history between species pairs of all six extant rock lobster species (Jasus spp.), which have a long larval duration of up to two years and have populated continental shelf and seamount habitats around the globe at approximately 40o S. Genetic differentiation patterns reflected geographic isolation and the environment (i.e. habitat structure). Eastern Pacific species (J. caveorum and J. frontalis) were geographically more distant and genetically more differentiated from the remaining four species. Species associated with continental shelf habitats shared a common ancestry, but are geographically distant from one another. Similarly, species associated with island/seamount habitats in the Atlantic and Indian Oceans shared a common ancestry, but are also geographically distant. Benthic temperature was the environmental variable that explained most of the genetic differentiation (FST ), while controlling for the effects of geographic distance. Eastern Pacific species retained a signal of strict isolation following ancient migration, whereas species pairs from Australia and Africa, and seamounts in the Indian and Atlantic oceans, included events of introgression after secondary contact. Our results reveal important effects of habitat and demographic processes on the recent divergence of species within the genus Jasus, providing one of the first empirical studies of genome-wide drivers of diversification that incorporates all extant species in a marine genus with long pelagic larval duration.

Marine predators feeding on fisheries catches directly on the fishing gear, a behaviour termed “depredation”, has emerged as a major human-wildlife conflict globally, often resulting in substantial socio-economic and ecological impacts. This study investigated the extent of this conflict in commercial Patagonian toothfish (Dissostichus eleginoides) fisheries across subantarctic waters where both killer whales (Orcinus orca) and sperm whales (Physeter macrocephalus) feed on toothfish caught on longline hooks. Using long-term datasets from six major fishing areas, from southern Chile to the Indian Ocean sector of the Southern Ocean, statistical models were developed to quantify the catch removals due to whale depredation interactions. The results indicated that these removals were large, totalling more than 6600 t of toothfish between 2009 and 2016 with an annual mean of 837 t [95% CI 480–1195 t], comprised of 317 t [232–403 t] and 518 t [247–790 t] removed by killer whales and sperm whales, respectively. Catch removals greatly varied between areas, with the largest estimates found at Crozet, where on average 279 t [179–379 t] of toothfish per year, equivalent to 30% [21–37%] of the total catches. Together, these findings provide metrics to assess the impacts of depredation interactions on the fishing industry, whale populations, fish stocks and associated ecosystems. With an estimated $15 M USD worth of fish depredated every year, this study highlights the large geographic scale and economic significance of the depredation issue and its potential to compromise the viability of some toothfish fisheries which are the primary socio-economic activity in subantarctic regions.

The scales of the grey notothen, Lepidonotothen squamifrons (Gunther, 1880), show the classical organization of ctenoid scales: an external acellular ornamented bony layer bordered by posterior spines, the ctenii, and overlaying an incompletely mineralized basal plate. The basal plate is constituted by a number of collagenous layers that form an orthogonal plywood-like organization. The mineralization of the basal plate progresses due to the formation of ovoid Mandl's corpuscles that progressively fused to each other. The morphology and the histology of scales of the grey notothen are similar to the scales of numerous Perciformes, such as the Percidae and the Cichlidae for example.

The emergence of longline fishing for Patagonian toothfish (Dissostichus eleginoides) on the Kerguelen Plateau over the past two decades is concomitant with the development of depredation-type interactions by sperm whales (Physeter macrocephalus). Through a unique collaboration between the French and the Australian fisheries operating respectively around Kerguelen, and Heard Island and McDonald Islands (HIMI), this study preliminarily investigated the spatio–temporal variations of the rate of occurrence of sperm whale depredation on the Kerguelen Plateau. Between 2011 and 2016, sperm whales depredated toothfish on 29.1% of all longline sets and over 49.4% of the fished area. The probability of vessels to experience depredation decreased with the latitude and decreased in winter. Vessels operating in Kerguelen experienced significantly higher rates of occurrence of sperm whale depredation (33.2 ± 4.5% of sets; 48.2 ± 7.2% of the area) than vessels operating in HIMI (3.1 ± 1.2% of sets; 5.4 ± 2.0% of the area) over the 2011–2016 period, but also during any season of the year. The results suggested that heterogeneity in the distribution of sperm whales is likely a key driver of depredation. The Kerguelen Plateau fisheries represent a unique opportunity to investigate the spatial factors influencing this distribution, and therefore to predict the occurrence of depredation.

Data collected by fishery observers on board French fishing vessels targeting Patagonian toothfish (Dissostichus eleginoides), were examined to quantify and describe shark by-catch within the Kerguelen exclusive economic zone (EEZ). From 2006 to 2016, the fishing crews of longline vessels reported the total catches of the line and observers were asked to identify and count fish by-catch on 25% of the total fishing effort. A total of 26 203 longline hauls and more than 55 million hooks were checked by observers reporting 29 500 individual sharks caught as by-catch. Four shark species were identified (traveller lantern shark – Etmopterus viator, southern sleeper shark – Somniosus antarcticus, Portuguese dogfish – Centroscymnus coelolepis and porbeagle shark – Lamna nasus) among which E. viator was numerically largely dominant (99%). Relative abundance (number of shark per 1 000 hooks observed) calculated for sets with sharks present, was used to show bathymetric and geographical distributions and biological data were analysed. There were marked differences between distributions of the shark by-catch species and their relative abundance. This study is a major contribution to the ecological knowledge of E. viator with a detailed description of its distribution, the deepest record for the species (1 951 m) and the updated length at first maturity for female (48.5 cm). Length-frequency distribution (LFD) for E. viator showed a bimodal distribution typical for long-lived species and a sexual dimorphism with females significantly longer than males. Although the stability of LFD through years seems to rule out the possibility of E. viator to be at risk in the Kerguelen EEZ, further studies must be conducted to assess population size and mitigate shark by-catch in the French longline fisheries. Prises accessoires de requins observées dans la pêcherie palangrière de fond au large des îles Kerguelen en 2006–2016, avec une attention particulière pour le sagre long nez (Etmopterus viator)

A new cryptic species of spotted barracudina, Arctozenus australis sp. nov., is described from the Kerguelen Islands, in the Indian Ocean sector of the Southern Ocean. It differs from the only congener, Arctozenus risso (Bonaparte, 1840), in the reduction of pigments on body, a more slender body, and longer head, snout and jaws. A neotype is designated for Paralepis risso Bonaparte, 1840 and Paralepis borealis Krøyer in Gaimard (1847). Note on synonymy of Paralepis risso is provided. Observation of adults of Notolepis annulata, Magnosudis prionosa and Paralepis coregonoides found loss of teeth on jaws and gill arches, suggesting more species in the subfamily Paralepidinae may commonly possess this character in adults.

The emergence of longline fishing around the world has been concomitant with an increase in depredation-interactions by odontocete whales (removal of fish caught on hooks), resulting in substantial socio-economic and ecological impacts. The extent, trends and underlying mechanisms driving these interactions remain poorly known. Using long-term (2003–2017) datasets from seven major Patagonian toothfish ( Dissostichus eleginoides ) longline fisheries, this study assessed the levels and inter-annual trends of sperm whale ( Physeter macrocephalus ) and/or killer whale ( Orcinus orca ) interactions as proportions of fishing time (days) and fishing area (spatial cells). The role of fishing patterns in explaining between-fisheries variations of probabilities of odontocete interactions was investigated. While interaction levels remained globally stable since the early 2000s, they varied greatly between fisheries from 0 to >50% of the fishing days and area. Interaction probabilities were influenced by the seasonal concentration of fishing effort, size of fishing areas, density of vessels, their mobility and the depth at which they operated. The results suggest that between-fisheries variations of interaction probabilities are largely explained by the extent to which vessels provide whales with opportunities for interactions. Determining the natural distribution of whales will, therefore, allow fishers to implement better strategies of spatio-temporal avoidance of depredation.

This document is a short extraction from the article “Benthic ecoregionalisation and conservation issues in the French Exclusive Economic Zone of Kerguelen” submitted the 16/05/2018 to the journal CCAMLR Science. Original article includes full benthic ecoregionalisation modelling results. In this document, a methodological focus is made to highlight the relevance of using the CCAMLR’s Vulnerable Marine Ecosystems bioindicator taxa to build benthic ecoregionalisation models, which constitutes a secondary result of the original study. Recommendations (working papers only) This document is to be discussed within the PAEWG-01 and during the PAEWG-01 physical meeting. CCAMLR’S VULNERABLE MARINE ECOSYSTEMS BIOINDICATOR TAXA: A RELEVENT TOOL FOR BENTHIC ECOREGIONALISATION Alexis Martin* (1), Emmanuelle Trouslard (1), Mélyne Hautecoeur (1), Jonathan Blettery (1), Camille Moreau (2), Thomas Saucède (3), Nadia Améziane (4), Guy Duhamel (1), Marc Eléaume (4) * Corresponding author: Alexis Martin, alexis.martin@mnhn.fr (1) Département Adaptations du Vivant, Muséum national d’Histoire naturelle, UMR BOREA 7208, 57 rue Cuvier, 75231 Paris Cedex 05, France (2) Laboratoire de Biologie Marine, Université Libre de Bruxelles, Avenue FD Roosevelt 50, CP 160/15, 1150 Bruxelles, Belgique (3) UMR 6282 Biogéosciences, Université Bourgogne Franche-Comté, CNRS, 6 bd Gabriel F-21000 Dijon, France (4) Département Origine et Évolution, Muséum national d’Histoire naturelle, UMR ISYEB 7205, 57 rue Cuvier, 75231 Paris Cedex 05, France

Small mesopelagic fish are ubiquitous in the ocean, representing an important trophic link between zooplankton and tertiary consumers such as larger fish, marine mammals and birds. Lanternfishes (Myctophidae) are common worldwide as well as in the Southern Ocean. However, only 17 of the approximately 250 myctophid species occur exclusively in sub-Antarctic or Antarctic waters. It is unclear whether they colonized these latitudes once and diversified from there, or whether multiple colonization events took place in which multiple ancestral phenotypes entered the Southern Ocean at various times. Phylogeographic patterns have been investigated for individual myctophid species, but so far no study has compared species across the Southern Ocean. Here, we present a dataset with previously unpublished cytochrome c oxidase I (COI; n = 299) and rhodopsin (rh1; n = 87) gene sequences from specimens collected at various locations in the Southern Ocean. Our data extend the DNA barcode library of Antarctic mesopelagic fish substantially. Combined morphological and molecular taxonomy lead to confident species level identification in 271 out of 299 cases, providing a robust reference dataset for specimen identification, independently of incomplete morphological characters. This is highly topical in light of prospective ecological metabarcoding studies. Unambiguous sequences were subsequently combined with publicly available sequences of the global DNA barcode library yielding a dataset of over 1,000 individuals for phylogenetic and phylogeographic inference. Maximum likelihood trees were compared with results of recent studies and with the geographical origin of the samples. As expected for these markers, deep phylogenetic relationships remain partially unclear. However, COI offers unmatched sample and taxon coverage and our results at the subfamily to genus level concur to a large extent with other studies. Southern Ocean myctophids are from at least three distant subfamilies suggesting that colonization has occurred repeatedly. Overall, spatial divergence of myctophids is rare, potentially due to their enormous abundance and the homogenizing force of ocean currents. However, we highlight potential (pseudo-)cryptic or unrecognized species in Gymnoscopelus bolini, Lampanyctus achirus, and the non-myctophid genus Bathylagus.

This report provides a presentation of the protocol and first preliminary results

Age and sex dependent spatial segregation has resulted in limited knowledge of the ecology and demography of sperm whale adult males feeding seasonally in high latitudes. This study focused on adult males interacting with the Patagonian toothfish (Dissostichus eleginoides) fishery operating off the Kerguelen and Crozet Archipelagos. Demographic parameters were estimated using a 10-yr-long photoidentification data set paired with multistate closed robust design capture-markrecapture models. The examination of a set of 29,078 photographs taken from fishing vessels during sperm whale depredation events resulted in identification of 295 individuals with nine visiting both study areas. Dispersal between both study regions was estimated to be 1% per year. The mean annual number of interacting sperm whales was estimated to n = 82 (95% CI 58 141) in Crozet and n = 106 (95% CI 76-174) in Kerguelen. Transient proportions were 13% in Crozet and 26% in Kerguelen. Corrected for transience, apparent survival estimates were 0.953 (95% CI 0.890-0.993) in Crozet, and 0.911 (95% CI 0.804-0.986) in Kerguelen. These survival and population size estimates are the first for depredating adult males in high latitudes, and can be used in evaluating the current conservation status of this historically harvested stock and to investigate depredation trends in 35 both Crozet and Kerguelen Islands.

In this paper, we report on fish by-catch during exploratory fishing activities undertaken in Divisions 58.4.1 and 58.4.2 during the 2012 to 2018 seasons. Fish by-catch comprised 14 species or groups of species. In 2018, by-catch represented 12% of the total catch (43 tonnes over 307 tonnes of Dissostichus spp.) in Divisions 58.4.1 and 58.4.2. 98% of the biomass was represented by 2 families: Macrouridae and Channichthyidae. The others most common by-catch species or families were Muraenolepis spp., Antimora rostrata and Artedidraconidae. Raja and Bathyraja were rarely caught. Species composition varied between research blocks except for Macrourus spp. which dominated by-catch composition everywhere. The ratio by-catch to target catch was higher in the eastern part of Division 58.4.1. The ratio Macrourus to Dissostichus increased in every research blocks during the study period, particularly in the eastern blocks where Macrourus CPUE also increased in the last 3 years. Macrourus CPUE was 23kg/1000 hooks in average with relatively little spatial variations except in the east were it could reach 180kg/1000 hooks locally. As found in others areas of the Convention, Macrourus CPUE was 2 times higher for autolines than Spanish lines and trotlines, and it peaked at depths between 900 and 1300m. CPUE distribution of the others by-catch species were much lower and highly heterogeneous in space. Macrourus catch was dominated by females in all research blocks and length frequency distribution did not reveal any temporal changes within research blocks. Length at 50% maturity was estimated for the two most common species of Macrourus (Macrourus whitoni and Macrourus caml) and for Chionobathyscus dewitti. 95% of the Muraenolepis sp. and Antimora rostrata were females in every research blocks with spatial variations in total length frequency distribution.

The grey notothen (Lepidonotothen squamifrons) and the mackerel icefish (Champsocephalus gunnari) (Notothenioidei; Perciformes; Teleostei) are two Southern Ocean acellular boned fishes whose bones show cyclical growth marks. The degree of mineralization of their bony tissues, respectively 1.06 to 1.39 gHA/cm(3) and 1.04 to 1.33 gHA/cm(3), is close to the values of better known acellular boned fishes like the wolffish, the anglerfish or the horse mackerel. The histological characteristics of bony tissues are not fundamentally different from those observed in other marine acellular boned fishes.