Patagonian Toothfish Research Articles

On the presence of Distichoptilum gracile Verrill, 1882 (Octocorallia: Pennatulacea), in the southeastern Pacific

The two-lined sea pen Distichoptilum gracile Verrill, 1882, the type and only species that is considered valid in the genus Distichoptilum Verrill, 1882, is a rather large deep-water pennatulacean found in soft bottoms. Its deep red colonies are conspicuously long (1 m or more) and thin, with autozooids arranged alternately in simple rows on each side. This species has an almost cosmopolitan but fragmentary distribution, with sparse records from the Atlantic, Indian and Pacific Oceans. In the Pacific Ocean, its occurrence has been scarcely reported: from off Mexico, the Galapagos Archipelago and off New Zealand. The present record of this rare species is based on a collected colony that was entangled in a longline used in the fisheries of the Patagonian toothfish Dissostichus eleginoides Smitt, 1898, off Chanaral (26°S), Region de Atacama, along the continental margin of northern Chile. Distichoptilum gracile is the third species of the entire order Pennatulacea to be recorded in Chile, being also the first record of the family Protoptilidae Kolliker, 1872, and of the genus Distichoptilum Verrill, 1882 for Chile. The presence of this species confirms the need not only for further studies of the bycatch of commercial fisheries, but also for inventories to document the diversity of deep-water anthozoans in the southeastern Pacific.

Continued increase in the number of black-browed albatrosses (Thalassarche melanophris) at Diego Ramírez, Chile

Black-browed albatrosses (Thalassarche melanophris) are killed incidentally in commercial fishing operations. Aerial surveys in 2002 and 2011 revealed the number of black-browed albatrosses at the Diego Ramirez and Ildefonso islands, Chile, increased by 52 and 18 %, respectively. The increases were attributed to reduced mortality in the longline fishery for Patagonian toothfish (Dissostichus eleginoides) following fleet conversion to a new gear configuration with much higher average hook sink rates. A new survey in 2014 revealed the number of black-browed albatrosses at Ildefonso was about the same as in 2011, but the number at Diego Ramirez had increased by a further 29 % (8.8 %/year). The number of grey-headed albatrosses (Thalassarche chrysostoma) at Diego Ramirez also increased, by 23 %, in the same time period. In 2014, Ildefonso held an estimated 54,284 breeding pairs of black-browed albatrosses. The populations of black-browed albatrosses at two more northern sites, the Evangelistas and Leonard islets, stood at 4818 and 545 breeding pairs, respectively. The total number of breeding pairs of both albatross species at Diego could not be determined because not all islands in the archipelago were surveyed.

Using satellite altimetry to inform hypotheses of transport of early life stage of Patagonian toothfish on the Kerguelen Plateau

Understanding patterns of oceanic transport and their role in population connectivity, particularly for the early life stages of marine organisms, has important implications for population biology and management. Various approaches have been used to observe and model larval transport and recruitment in marine environments. In the Southern Ocean, these approaches are presented with particular challenges due to logistical difficulties in accessing and sampling remote, open water or deep-sea environments. In this study, we examine the use of remotely-sensed sea surface height data (AVISO) – which is now easily accessible and available for more than 20 years – to model transport and dispersion of eggs and early larval stages of Patagonian toothfish on the Kerguelen Plateau in the Indian Sector of the Southern Ocean. We compare simulated transport patterns from AVISO with those calculated from an ocean reanalysis product (Southern Ocean State Estimate; SOSE), and draw conclusions on likely patterns of connectivity between spawning regions and regions that offer suitable habitat for juvenile fish. The results of our study suggested regions with successful spawning that are consistent with those observed by the fishery and describe inter-annual differences in simulated connectivity between spawning and recruitment habitats.

Distribution and abundance of skates (Bathyraja spp.) on the Kerguelen Plateau through the lens of the toothfish fisheries

Three species of skate, Bathyraja eatonii, B. irrasa and B. murrayi, are commonly taken as incidental by-catch in Patagonian toothfish (Dissostichus eleginoides) longline and trawl fisheries, and the mackerel icefish (Champsocephalus gunnari) trawl fishery on the Kerguelen Plateau (KP) in the southern Indian Ocean. Data from fishery observations for 1997–2014 shows that the three skates were widely distributed across the Kerguelen Plateau, showing different spatial distributions, linked mainly with depth. Off Heard Island and McDonald Islands (HIMI), in the southern part of the KP, B. eatonii and B. irrasa were most abundant to the north and northwest of Heard Island, out to the edge of the Australian Exclusive Economic Zone (EEZ), and were caught down to depths of 1790m and 2059m respectively. The smallest species, B. murrayi, occurred mainly in the shallower waters down to 550m, and was most abundant to the north and northeast, close to Heard Island. Around Kerguelen Islands, in the northern part of the KP, skates were most abundant between the 500m and 1000m contours circling and extending from the islands.Catch rates were modelled using zero-inflated GAMs and GLMs. The catch rates of skates from the trawl fisheries in the Australian EEZ surrounding Heard Island and McDonald Islands have shown little evidence of depletion on the main trawl fishing grounds, although there is evidence of a decrease in the average total length of B. eatonii. The marine reserves and the conservation measures employed by the Commission for the Conservation of Antarctic Marine Living Resources in the HIMI fisheries, appear to provide effective protection for the skates, at least in the shallower waters where the trawl fisheries operate. B. irrasa taken in the deeper waters where longline fishing occurs have shown a slight decline in catch rate over the years of the HIMI fishery. Although all skates are returned to the water from this fishery, survival rates are unknown and careful monitoring should continue to assess the status of these stocks. There appears to be little change in the abundance of the skate species at Kerguelen in the time period.This study provides the first review of skate by-catch across both the HIMI and Kerguelen fisheries. Ongoing monitoring of species specific by-catch levels and further research to determine the important life history parameters of these species are required, particularly for B. irrasa which is taken in both trawl and longline fisheries.

Metazoan parasites of deep-sea fishes from the South Eastern Pacific: Exploring the role of ecology and host phylogeny

We studied the parasite fauna of five deep-sea fish species (>1000m depth), Three members of Macrouridae (Macrourus holotrachys, Coryphaenoides ariommus and Coelorhynchus sp.), the Morid Antimora rostrata and the Synaphobranchidae Diaptobranchus capensis caught as by-catch of the Patagonian toothfish (Dissostichus eleginoides) from central and northern Chile at depths between 1000 and 2000m. The parasite fauna of M. holotrachys was the most diverse, with 32 species (The higher reported for Macrourus spp.) and the lower occur in the basketwork eel D. capensis (one species). Trophically transmitted parasites, mainly Digenea and Nematoda explain 59.1% of the total number of species obtained (44 species) and the 81.1% of the 1020 specimens collected. Similarity analysis based on prevalence as well as a Correspondence analysis shows that higher similitude in parasite fauna occurs in members of Macrouridae. The importance of diet and phylogeny is discussed as forces behind the characteristics of the endoparasite and ectoparasite communities found in the studied fish species.

DNA barcoding reveals substitution of Sablefish (Anoplopoma fimbria) with Patagonian and Antarctic Toothfish (Dissostichus eleginoides and Dissostichus mawsoni) in online market in China: How mislabeling opens door to IUU fishing

China’s rapid economic development has determined profound changes in seafood consumption patterns, and nowadays besides the traditional luxury seafood, high-quality marine fish are consumed. Among these is Anoplopoma fimbria (Sablefish), a highly priced species on the Chinese market. A recent molecular survey on products sold online in China found that all the analyzed products sold as Yin Xue, used to indicate A. fimbria, were instead Dissostichus spp., a genus of fish extremely vulnerable to overfishing (Xiong et al., 2016). Considering this and the lack of a standardized naming system for seafood species in China, an initial search was conducted to identify all the possible Chinese names indicating A. fimbria. The aim of the present study was to assess the challenges of the online market with regards to frauds for fish species substitution. DNA barcoding was employed to verify the identity of 42 products sold on e-commerce platforms as Sablefish. Moreover, the information reported on the webpage and on the label was analyzed according to the Chinese regulation in force. All the PCR products gave readable sequences. By using the IDs analysis on BOLD and the BLAST analysis on GenBank all the samples were unambiguously identified at the species level. Of the 42 products sold as Sablefish, only 6 (14.3%) were molecularly identified as this species, while 32 (76.2%) were identified as Dissostichus eleginoides (Patagonian Toothfish) and 4 (9.5%) as Dissostichus mawsoni (Antarctic Toothfish), highlighting an alarming overall misrepresentation rate of 85.7% and implications for the management of these species’ fisheries. The combined analysis of all the information of the webpages and the labels allowed us to hypothesize unintentional and intentional mislabeling. Our findings suggest the possible existence of a trade pattern enabling IUU fishing operators to launder illegal catches of Toothfish through mislabeling.

Genetic structure of Patagonian toothfish populations from otolith DNA

AbstractThe 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 found between three sectors with nuclear markers. However, only the Pacific sector was differentiated from other sectors with mitochondrial markers. This study demonstrates the usefulness of otolith DNA as a means of increasing sample sizes for population genetics research of fish. Additionally, the combination of nuclear and mitochondrial markers may allow insight into how the observed differences in movements between male and female toothfish impact population structure.

Variation in the diet of killer whales Orcinus orca at Marion Island, Southern Ocean

MEPS Marine Ecology Progress Series Contact the journal Facebook Twitter RSS Mailing List Subscribe to our mailing list via Mailchimp HomeLatest VolumeAbout the JournalEditorsTheme Sections MEPS 549:263-274 (2016) - DOI: https://doi.org/10.3354/meps11676 Variation in the diet of killer whales Orcinus orca at Marion Island, Southern Ocean Ryan R. Reisinger1,5,*, Darren R. Gröcke2, Nico Lübcker1, Erin L. McClymont3, A. Rus Hoelzel4, P. J. Nico de Bruyn1 1Mammal Research Institute, Department of Zoology and Entomology, University of Pretoria, Private Bag X20, Hatfield 0028, Pretoria, South Africa 2Department of Earth Sciences, Durham University, South Road, Durham DH1 3LE, UK 3Department of Geography, Durham University, South Road, Durham DH1 3LE, UK 4School of Biological and Biomedical Sciences, Durham University, South Road, Durham DH1 3LE, UK 5Present address: Department of Zoology, Nelson Mandela Metropolitan University, PO Box 77000, Port Elizabeth 6031, South Africa *Corresponding author: ryan.r.reisinger@gmail.com ABSTRACT: Diet seems to be a key factor driving diversity and isolation among killer whale populations. Killer whales at Marion Island, Southern Ocean, have been observed preying on seals and penguins but are also know to depredate Patagonian toothfish from longline fishing vessels. However, their diet is poorly known especially when they occur offshore. We analysed carbon and nitrogen stable isotope ratios in 32 skin samples collected from 24 killer whales belonging to 8 social units. Adult males showed higher δ15N values than adult females or subadults, indicating that they occupy a higher relative trophic level. There were no significant differences in δ13C among social units, but δ15N differed significantly and 2 individuals from social units which have been observed depredating Patagonian toothfish had higher δ15N values. The inshore presence of killer whales at Marion Island was a significant predictor of δ13C values, but not of δ15N values. This suggests some foraging north of Marion Island, potentially on lower trophic level prey. We also analysed tissue samples from seal, penguin and Patagonian toothfish prey and used available values for Antarctic fur seals. Results show that killer whales around Marion Island are apex predators, but that they do not feed exclusively on other high trophic level predators such as elephant seals, fur seals, and Patagonian toothfish. Killer whales had δ15N values similar to those of Patagonian toothfish and adult male elephant seals, implying that the diet of killer whales at Marion Island includes some lower trophic level prey such as cephalopods or fishes. KEY WORDS: Predator · Stable isotopes · Carbon · δ13C · Nitrogen · δ15N · Foraging · Trophic level Full text in pdf format Supplementary material PreviousNextCite this article as: Reisinger RR, Gröcke DR, Lübcker N, McClymont EL, Hoelzel AR, de Bruyn PJN (2016) Variation in the diet of killer whales Orcinus orca at Marion Island, Southern Ocean. Mar Ecol Prog Ser 549:263-274. https://doi.org/10.3354/meps11676 Export citation RSS - Facebook - Tweet - linkedIn Cited by Published in MEPS Vol. 549. Online publication date: May 10, 2016 Print ISSN: 0171-8630; Online ISSN: 1616-1599 Copyright © 2016 Inter-Research.

Depredation of Patagonian toothfish (Dissostichus eleginoides) by two sympatrically occurring killer whale (Orcinus orca) ecotypes: Insights on the behavior of the rarely observed type D killer whales

AbstractSympatric forms of ecologically distinctive killer whales (Orcinus orca) have been documented worldwide. This study focused on a new case of such sympatric occurrence of the “Crozet” type and the recently described “type D” killer whales off the Crozet Islands. The two ecotypes are morphologically and genetically distinct, but they both depredate the same local longline fishery. We used observational, photo‐identification, and fishing data, collected between 2003 and 2015, to examine differences in their patterns of depredation. Of the 828 sets where ecotype could be confirmed, type D killer whales interacted with 82 (11%) of the sets, including 9 (1%) sets that were simultaneously depredated by both ecotypes. Associations between the two types were never observed. Type D killer whales typically occurred in larger groups and both ecotypes preferentially depredated Patagonian toothfish (Dissostichus eleginoides). GLMM modeling revealed that the probability of type D depredation significantly increased throughout the study period, especially in deep waters, and photo‐identification data suggested that a subset of all individuals were habituating to depredation. This study documents the partitioning of resources between two distinct ecotypes of killer whales and provides preliminary insight into the feeding ecology of the rare type D killer whale.

Coincident recruitment patterns of Southern Hemisphere fishes

Three dominant recruitment patterns were identified across 30 stocks from Australia, New Zealand, Chile, South Africa, and the Falkland Islands using data from 1980 to 2010. Cluster and dynamic factor analysis provided similar groupings. Stocks exhibited a detectable degree of synchrony among species, in particular the hakes and lings from Australia, New Zealand, Chile, and South Africa. We tested three climate indices, the Interdecadal Pacific Oscillation (IPO), Southern Annular Mode (SAM), and Southern Oscillation Index (SOI), to explore their relationship with fish stock recruitment patterns. The time series of IPO and SOI showed the strongest correlation with New Zealand hoki (blue grenadier, Macruronus novaezelandiae) and Australian jackass morwong (Nemadactylus macropterus) (r = 0.50 and r = –0.50), and SAM was positively related to Australian Macquarie Island Patagonian toothfish (Dissostichus eleginoides) (r = 0.49). Potential linkages in recruitment patterns at sub-basin, basin, and multibasin scales and regional and global climate indices do account for some of the variation, playing an important role for several key Southern Hemisphere species.

Interactions between ageing error and selectivity in statistical catch-at-age models: simulations and implications for assessment of the Chilean Patagonian toothfish fishery

Abstract In age-structured fisheries stock assessments, ageing errors within age composition data can lead to biased mortality rate and year-class strength estimates. These errors may be further compounded where fishery-dependent age composition data are influenced by temporal changes in fishery selectivity and selectivity misspecification. In this study, we investigated how ageing error within age composition data interacts with time-varying fishery selectivity and selectivity misspecification to affect estimates derived from a statistical catch-at-age (SCA) model that used fishery-dependent data. We tested three key model parameters: average unfished recruitment (R0), spawning stock depletion (Dfinal), and fishing mortality in the terminal year (Fterminal). The Patagonian toothfish (Dissostichus eleginoides) fishery in southern Chile was used as a case study. Age composition data used to assess this fishery were split into two sets based on scale (1989–2006) and otolith (2007–2012) readings, where the scale readings show clear age-truncation effects. We used a simulation-estimation approach to examine the bias and precision of parameter estimates under various combinations of ageing error, selectivity type (asymptotic or dome-shaped), selectivity misspecification, and variation in selectivity over time. Generally, ageing error led to overly optimistic perceptions of current fishery status relative to historical reference points. Ageing error generated imprecise and positively biased estimates of R0 (range 10 to >200%), Dfinal (range −20 to >100%), and Fterminal (range −15 to >150%). The bias in Dfinal and R0 was more severe when selectivity was dome-shaped. Time-varying selectivity (both asymptotic and dome-shaped) increased the bias in Dfinal and Fterminal, but decreased the bias in R0. The effect of ageing error was more severe, or was masked, with selectivity misspecification. Correcting the ageing error inside the SCA reduced bias and improved precision of estimated parameters .

The complete mitochondrial genome sequence and gene organization of Trematomus bernacchii (Perciformes: Nototheniidae) with phylogenetic consideration

In this study, the complete mitochondrial DNA sequence was obtained from Trematomus bernacchii. The full length of mitogenome was 16 018 bp, including 20 transfer RNA genes, a 16S ribosomal RNA genes and an incomplete 12S rRNA, 12 protein-coding genes and an incomplete ND6 protein-coding gene, and 2 non-coding regions: control region (D-loop) and origin of light-strand (L-strand) replication (OL). Most genes were located on the heavy-strand (H-strand), while ND6 and seven tRNA genes were located on the L-strand. T. bernacchii’s mitogenome was comprised of 24.52% for A, 25.44% for C, 20.38% for G and 29.66% for T, with a higher A + T content (54.18%). From the NJ phylogenetic tree, it revealed that T. bernacchii’s was genetically closest to species Dissostichus eleginoides among seven species within suborder Notothenioidei. This study could lay the foundation for the future studies in species identification, taxonomic status, molecular systematics, stock evaluation and conservation genetics for T. bernacchii’s.

Modelling spatial distribution of Patagonian toothfish through life-stages and sex and its implications for the fishery on the Kerguelen Plateau

Size and sex specific habitat preferences are common in animal populations and can have important implications for sound spatial management of harvested species. Patagonian toothfish (Dissostichus eleginoides) is a commercially exploited fish species characterised by its longevity (>50yo) and its extremely broad distribution in depths ranging from 10m to 2500m on most of the Plateaux, banks and seamounts of the Southern Ocean. As many bentho-pelagic fish species, Patagonian toothfish exhibits sexual dimorphism and ontogenetic habitat shift towards deeper waters as they grow. In this study, we modelled the spatial structure of Patagonian toothfish population (median total length and sex composition) in a data-rich area, the Kerguelen Plateau (Southern Indian Ocean), to better understand the ecological drivers of their distributional patterns and inform current and future fishery management strategies. We applied spatially-explicit statistical models to quantify and predict the effects of the complex topography of the Kerguelen Plateau in structuring the spatial distribution of Patagonian toothfish total length and sex ratio, while controlling for gear selectivity and season. Model predictions showed that juvenile toothfish live in shallow regions (shelf and banks) and move downward progressively up to 600m while they grow. Between 600m and 1200m, the downward movement stops and fish settle at their preferred depths. While in this depth range, fish are ∼75cm long and most vulnerable to fisheries. As they approach maturity large fish move downward to deep-sea habitats (from 1200m to >2300m) and head towards the spawning grounds on the western side of the plateau and around Skiff Bank. Importantly, the sex ratio was not evenly distributed across the Plateau; prediction maps revealed a higher proportion of females in the South whereas a strong male-bias sex ratio (70%) occurred in the North-West. Large-scale prediction maps derived from our models assisted in developing hypotheses regarding ecological drivers of Patagonian toothfish habitat-use and movement across different life stages and sex. Such hypotheses are crucial to inform management strategies of this multijurisdictional fishery (France and Australia) at the spatial and temporal scales over which natural processes and fishery extend.

New records of deep-sea sea spiders (Chelicerata: Pycnogonida) in the southeastern Pacific

New records of the very large sea spiders Colossendeis colossea, Colossendeis macerrima, and Colossendeis minor are presented based on specimens collected as bycatch from the deep water fisheries of the Patagonian toothfish during January–March 2015 off the port of Caldera (27° S), Region de Atacama, northern Chile. The specimens examined represent the deepest bathymetric record for C. colossea in the country, the northernmost record of C. macerrima for Chile, extending its previous record by about 2170 km, and the first record of C. minor in Chilean waters, which is also the southernmost record of C. minor for the Pacific Ocean. The presence of these species in northern Chile may give hints of a continuous distribution of this genus along the Chilean coasts, representing part of a hidden biodiversity of invertebrates thriving in deep waters in the southeastern Pacific.

Multiple independent reduction or loss of antifreeze trait in low Antarctic and sub-Antarctic notothenioid fishes

AbstractAntifreeze glycoprotein (AFGP) in Antarctic notothenioids presumably evolved once at the base of the notothenioid radiation in the Southern Ocean. Some species closely related to the endemic Antarctic notothenioids occur in non-freezing sub-Antarctic waters where antifreeze protection is unnecessary. We examined the antifreeze trait (phenotype and genotype) of these sub-Antarctic species to help infer their evolutionary history and origin. The status of the AFGP genotype (AFGP coding sequences in DNA) and/or phenotype (serum thermal hysteresis) varies widely, from being undetectable in Dissostichus eleginoides and Patagonotothen species from the Falkland Islands, minimal in Marion Island Paranotothenia magellanica and Lepidonotothen squamifrons from the South Sandwich and Bouvet islands, to considerable genotype in the Falkland Islands Champsocephalus esox and Marion Island Harpagifer georgianus. All low Antarctic notothenioid species examined show substantial AFGP trait. Mapping of the AFGP trait status onto ND2 phylogenetic trees of a large sampling of notothenioids revealed that AFGP trait reduction or loss occurred at least three independent times in different lineages.

Functional characterisation of the haemoglobins of the migratory notothenioid fish Dissostichus eleginoides

This study addresses the primary structure, the oxygen-binding properties and the CO-rebinding kinetics of the haemoglobins of the Patagonian toothfish Dissostichus eleginoides. D. eleginoides belongs to the family Nototheniidae, the most diversified of the suborder Notothenioidei, mostly exhibiting an Antarctic distribution. Some of its features are typical of Antarctic species, some are not. For instance, D. eleginoides appears not to have functional antifreeze glycoproteins (consistent with its non-Antarctic distribution). In contrast, it has a major and a minor haemoglobin (similar to many Antarctic notothenioids), and their very low oxygen affinity does not follow the trend of other non-Antarctic notothenioids and appears typical of cold-adapted species. Moreover, the amino-acid sequence reveals high identity with the globins of Antarctic notothenioids, arguing in favour of a common origin within notothenioids, and indicates that the primary structure of the major and minor haemoglobins has undergone modifications only to a limited extent. The ligand-rebinding kinetics of the major haemoglobin of D. eleginoides indicate a strong stabilisation of the quaternary T state at lower pH values.

Distribution, habitat and trophic ecology of Antarctic squid Kondakovia longimana and Moroteuthis knipovitchi: inferences from predators and stable isotopes

Cephalopods have a key role in the marine environment though knowledge of their distribution and trophic ecology is limited by a lack of observations. This is particularly true for Antarctic species. Toothfish species are key predators of cephalopods and may be viewed as ideal biological samplers of these species. A total of 256 cephalopod lower beaks were identified from the stomachs of Patagonian toothfish (Dissostichus eleginoides) and Antarctic toothfish (Dissostichus mawsoni), captured in fisheries of South Georgia and the South Sandwich Islands in the South Atlantic between March and April 2009. Long-armed octopus squid (Kondakovia longimana) and smooth-hooked squid (Moroteuthis knipovitchi) were the main cephalopod prey and both were predated upon wherever toothfish were captured, though this cephalopod species appear to inhabit deeper waters at the South Sandwich Islands than at South Georgia. Measurements of δ13C from beak material indicated a clear segregation of habitat use comparing adult and sub-adult sized K. longimana. Variation in δ15N with size indicated an ontogenetic shift in the diet of cephalopods and also suggested some trophic plasticity among years. This study provides new insights into the private life of some elusive Antarctic cephalopods in an underexplored region of the South Atlantic.

The impact of predation by marine mammals on patagonian toothfish longline fisheries.

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 and focused in areas of putative migration routes, and the impact is compounded as a result of the fishery also concentrating in those areas at those times. Understanding the seasonal behaviour of orcas and the spatial and temporal distribution of “depredation hot spots” can reduce marine mammal interactions, will improve assessment and management of the stock and contribute to increased operational efficiency of the fishery. Such information is valuable in the effort to resolve the human-mammal conflict for resources.

살오징어(Todarodes pacificus) 간유 및 비막치어(Dissostichus eleginoides) 근육지질이 흰쥐의 혈청지질 및 지방조직에 미치는 영향

This study investigated the effects of squid Todarodes pacificus liver oil on the serum lipids and adipose tissue weight of rats. The rats in the soybean oil (SO) group received a basic diet prepared according to the recommendations of the American Institute of Nutrition (AIN-93G), with 7% SO as lipid source. The rats in the Patagonian toothfish Dissostichus eleginoides muscle oil (PTFO) group received 5% PTFO and 2% SO as the lipid source, while the rats in the eco-friendly squid liver oil (EFSO) group received 5% EFSO and 2% SO. EFSO was prepared according to the method outlined in the author’s patent. PTFO was extracted from muscle using a physical method in the author’s laboratory. The prominent polyunsaturated fatty acids in the dietary oils were 18:2n-6 (54.3%) and 18:3n-3 (5.64%) in SO, DHA (6.77%) and EPA (3.61%) in PTFO, and DHA (26.2%) and EPA (9.94%) in EFSO. After feeding for 4 weeks, the serum lipid levels (e.g., triglyceride, total cholesterol, and low-density lipoprotein cholesterol) of the rats in the EFSO group were significantly reduced as compared with those in the SO group (P<0.05); those of the rats in the PTFO group were also reduced, albeit not significantly, compared with the SO group. On the other hand, the total white adipose tissue (visceral, epididymal, and perirenal) weight was significantly reduced in the EFSO and PTFO groups compared to the SO group. These results demonstrate that EFSO is an effective lipid modifying agent in rat blood, and that EFSO and PTFO have greater anti-obesity effects than SO.

Long-term studies of Crozet Island killer whales are fundamental to understanding the economic and demographic consequences of their depredation behaviour on the Patagonian toothfish fishery

AbstractThis paper provides a synthesis of results obtained as part of a long-term collaborative study involving biologists, fishers, and resource managers—centring on the occurrence of killer whales in the Crozet Archipelago before and after the implementation of a demersal longline fishery for Patagonian toothfish. Depredation behaviour was reported as soon as the fishery was initiated, with dramatic effects on both the demographic trajectories of the killer whales and on the amount of fish lost by the fishers. Killer whales interacting with the fishery exhibited very high mortality rates when illegal fishing took place, while killer whales not interacting were unaffected. However, after illegal fishing ended, killer whales interacting with the fishery exhibited both higher fecundity and survival rates compared with killer whales not interacting. Since whales typically removed fish entirely from the hooks, an adapted methodology that did not rely on determining the number of damaged fish was developed to estimate depredation rates. In the Crozet EEZ over a 10-year period, 33.9% of the total amount of Patagonian toothfish caught, representing a total of 28 million €, was estimated to be lost due to the combined effects of killer whale and sperm whale depredation. In an effort to reduce depredation losses, modifications to fishing methods, such as changing the fishing season, changing fishing areas when exposed to depredation and changing longline length and hauling speed were successfully tested. Acoustic deterrent devices were ineffective in deterring killer whales from depredating longlines. Alternative fishing gears, such as fish pots, were also tested. However, while providing encouraging results regarding the suppression of depredation and seabird bycatch, fish pots were not efficient enough to sustain an economically viable fishery. In conclusion, we discuss how the findings of this comprehensive study can be used elsewhere in fisheries confronted with depredation.