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Christophe Guinet - One of the best experts on this subject based on the ideXlab platform.
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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
Marine Mammal Science, 2016Co-Authors: Paul Tixier, Guy Duhamel, Nicolas Gasco, Christophe GuinetAbstract:Sympatric 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.
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observations of a distinctive morphotype of killer whale orcinus orca type d from subantarctic waters
Polar Biology, 2011Co-Authors: Robert L. Pitman, John W Durban, Michael Greenfelder, Morton Jorgensen, Paula A Olson, Jordi Plana, Paul Tixier, Christophe Guinet, Jared R. TowersAbstract:Studies have shown that killer whale (Orcinus orca) communities in high latitudes regularly comprise assemblages of sympatric ‘ecotypes’—forms that differ in morphology, behavior, and prey preferences. Although they can appear superficially similar, recent genetic evidence suggests that breeding is assortative among ecotypes within individual communities, and species-level divergences are inferred in some cases. Here, we provide information on a recently recognized ‘type D’ killer whale based on photographs of a 1955 mass stranding in New Zealand and our own six at-sea sightings since 2004. It is the most distinctive-looking form of killer whale that we know of, immediately recognizable by its extremely small white eye patch. Its geographic range appears to be circumglobal in subantarctic waters between latitudes 40°S and 60°S. School sizes are relatively large (mean 17.6; range 9–35; n = 7), and although nothing is known about the type D diet, it is suspected to include fish because groups have been photographed around longline vessels where they reportedly depredate Patagonian toothfish (Dissostichus eleginoides).
Alberto Reyes - One of the best experts on this subject based on the ideXlab platform.
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vitellogenesis in the patagonian toothfish Dissostichus eleginoides conditioned to a recirculating aquaculture system
General and Comparative Endocrinology, 2021Co-Authors: Rodolfo Amthauer, Alberto Reyes, Rodrigo Vidal, Francisca Cardenas, Ariel Valenzuela, Patricio Dantagnan, Luis VargaschacoffAbstract:Abstract The Patagonian toothfish (Dissostichus eleginoides) is a new promising fish species for diversifying the aquaculture industry in Chile because of its high economic value and high international demand. However, when attempting to start aquaculture of a new species, one of the major challenges is successfully achieving conditions to reproduce them. This is particularly difficult when the information on the biology and physiology of the reproduction process of the species in question is scarce, as is the case with D. eleginoides. Additionally, female reproductive dysfunction is more prevalent under culture conditions and it is very important to have tools to evaluate the progress of oocyte maturation. Therefore, evaluation of the vitellogenesis process in addition to measuring gonadosomatic index (GSI) and oocyte diameter is an important parameter for allowing the monitoring of females from a broodstock that will spawn in the reproductive season. This study aimed to develop an enzyme-linked immunosorbent assay (ELISA) specific for the Patagonian toothfish (D. eleginoides) vitellogenine (Vtg) and quantify the plasma level in the fishes, maintained in a recirculation aquaculture system (RAS), throughout their reproductive cycle. A polyclonal antibody was prepared using the isolated major egg protein as antigen. This antibody was specific to the major plasma phosphoprotein identified as Vtg and was used to develop and standardize an indirect ELISA assay. The assay standard curve was linear from 0.1 to 1 µg/ml purified egg yolk protein and the average r2 was 0.995. We corroborated our ELISA assay by demonstrating a strong correlation between high levels of plasma Vtg obtained by the assay and the intensity of the corresponding bands in both SDS-PAGE coomassie stained gels and Western Blot. During the two reproductive seasons analyzed, the highest Vtg plasma level was obtained in the majority of the females in the last three months before spawning (December-January). This differs from the wild population in which the spawning occurs during the austral winter (June-September). Therefore, the RAS condition established to maintain in captivity the D. eleginoides allows females to develop mature oocytes normally, as was evidenced by picks of Vtg plasma levels.
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novel microsatellite markers discovery in patagonian toothfish Dissostichus eleginoides using high throughput sequencing
Molecular Biology Reports, 2019Co-Authors: Killen Ko Garcia, Jorge Touma, Scarleth Bravo, Francisco Leiva, Luis Vargaschacoff, Rodolfo Amthauer, Ariel Valenzuela, Patricio Datagnan, Alberto ReyesAbstract:Patagonian toohfish (Dissostichus eleginoides), is a sub Antartic notothenioid fish key in the marine ecosystem that sustains fishery of higher commercial value in the world. However, there are a scarce knowledge or information about its population genetic background, product of the almost null information of molecular markers available for this species. Here, we use high-throughput sequencing technology (Illumina platform) to develop 1071 microsatellite loci, of which 22 loci were selected to evaluation. Polymorphism and genetic diversity of each locus was assessed in two locations distant by 2370 km. Considering both locations, a mean PIC value of 0.748 was estimated. Selected microsatellite loci showed among two to seventeen alleles by locus in the first location and two to twelve in the second. The observed heterozygosity varied from 0.18 to 0.91 and from 0.12 to 0.87 for the first and second location, respectively. While, the expected heterozygosity ranged from 0.15 to 0.92 and from 0.11 to 0.90. Three loci were monomorphic in only one location. Microsatellite markers developed here will be useful in future studies on conservation, fishery and population genetics of this species.
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Captura y mantención de Dissostichus eleginoides para conformar un plantel de reproductores Capture and maintenance of Dissostichus eleginoides to establish a broodstock group
Escuela de Ciencias del Mar Facultad de Recursos Naturales Pontificia Universidad Católica de Valparaíso, 2012Co-Authors: Alberto Reyes, Roberto Kido, Carlos A MorenoAbstract:Se reportan resultados en la captura, transporte y mantención de ejemplares vivos de bacalao de profundidad (Dissostichus eleginoides Smitt, 1898), para conformar un plantel de reproductores, destinados a emprender el cultivo experimental de este importante pez marino. Se enfatiza las causas de mortalidad y tasas de sobrevivencia post-captura en el mar. En tres años de experiencia se obtuvo una sobrevivencia general de 13% en promedio, de tres campanas de captura, y un período de tres años de mantención de los peces en estanques de 30 m³ en tierra, en un sistema de agua de mar circulante con control de factores ambientales. La mortalidad en los tanques ocurrió principalmente en el periodo inicial hasta lograr la adaptación en el hábitat artificial.We report results in the capture, transport and maintenance of live toothfish (Dissostichus eleginoides Smitt, 1898), to form a broodstock, for undertaking the experimental cultivation of this valuable marine fish. Emphasis is made in the causes of mortality and survival rates post capture at sea. In three years of experience was obtained an overall survival of 13% on the average, in three campaigns of capture, and a three-year maintenance of fish in 30 m³ ponds on land, in an environmental factors controlled circulating seawater system. The tanks mortality occurred mainly in the initial period to achieve adaptation in artificial habitats
Guy Duhamel - One of the best experts on this subject based on the ideXlab platform.
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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
Marine Mammal Science, 2016Co-Authors: Paul Tixier, Guy Duhamel, Nicolas Gasco, Christophe GuinetAbstract:Sympatric 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.
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Interactions between Cetacean and Fisheries in the Southern Ocean
Polar Biology, 2006Co-Authors: Karl-hermann Kock, Martin G Purves, Guy DuhamelAbstract:Soon after longlining on Patagonian toothfish ( Dissostichus eleginoides ) started in the Southern Ocean in the second half of the 1980s, interactions of cetaceans with these fisheries became apparent. The two species primarily involved were orcas (killer whales) ( Orcinus orca ) and male sperm whales ( Physeter macrocephalus ). Both species took substantial number of fish from the line primarily during day light hours. Catch rates of longliners declined to less than 50% when orcas occurred close to longline vessels while the loss to sperm whales was much less obvious. They were seen diving close to the line down to 400 m where they apparently took fish. Their impact on catch rates was much less notable. Sperm whales became frequently entangled in the line and part of the line was lost in a number of cases. Other cetaceans were rarely seen in the vicinity of longline vessels. They became entangled in the line only occasionally and one whale (presumably a minke whale) died.
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interactions between longline vessels and seabirds in kerguelen waters and a method to reduce seabird mortality
Biological Conservation, 1996Co-Authors: Yves Cherel, Henri Weimerskirch, Guy DuhamelAbstract:Abstract A longline fishery for Dissostichus eleginoides has recently developed in the vicinity of South Georgia and Kerguelen islands, two internationally important breeding areas for procellariiform birds. The number of hooked birds and a method to reduce mortality were investigated during 13 days of fishing activity in Kerguelen waters in February 1994. Between 100 and 600 seabirds were always observed behind the longline vessel during daytime. The main ship-following species were the white-chinned petrel Procellaria aequinoctialis (67% of counts), giant petrels Macronectes spp. (8%) and the wandering albatross Diomedea exulans (11%), black-browed albatross D. melanophris (6%) and grey-headed albatross D. chrysostoma (2%). Only diving species were caught on the lines, i.e. the white-chinned petrel (n = 36) and the grey-headed albatross (n = 2). Marked differences in the mortality rate were observed between day and night (1·00 versus 0·38 birds per 1000 hooks), and at night when the decklights were on or off (0·59 versus 0·15 birds per 1000 hooks). Dumping of homogenized offal during line settings greatly reduced incidental capture of seabirds, mainly because birds were more attracted by offal than by hooked baits. We therefore propose that the dumping of offal during line settings should be included in the regulations of the longline fishery for Dissostichus in order to minimize seabird mortality.
Peter L Horn - One of the best experts on this subject based on the ideXlab platform.
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the antarctic toothfish Dissostichus mawsoni biology ecology and life history in the ross sea region
Hydrobiologia, 2015Co-Authors: Stuart Hanchet, Peter L Horn, Darren W Stevens, Alistair Dunn, Steven J Parker, Sophie MormedeAbstract:The Antarctic toothfish (Dissostichus mawsoni, Norman) is a large notothenioid fish that supports valuable fisheries around the Antarctic continent. The Ross Sea fishery, which started in 1997, is managed by the Commission for the Conservation of Antarctic Marine Living Resources (CCAMLR). Whilst a large amount of research into the biology of this species has been carried out over the past decade, much of this work has been presented in CCAMLR working group papers and has not been published in the primary literature. In this paper, we bring together and summarise the extensive published and unpublished literature on the biology and ecology of Antarctic toothfish in the Ross Sea region including distribution, stock structure, reproduction, age and growth, and trophic ecology in a single document for the first time. We also review and further develop testable hypotheses surrounding its life cycle and identify gaps in our knowledge including spawning behaviour and early life history which need to be addressed.
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age and growth of patagonian toothfish Dissostichus eleginoides and antarctic toothfish d mawsoni in waters from the new zealand subantarctic to the ross sea antarctica
Fisheries Research, 2002Co-Authors: Peter L HornAbstract:Abstract The margins of otoliths of Patagonian toothfish ( Dissostichus eleginoides ) from several samples collected throughout the year were classified as either opaque or translucent. The margins were generally opaque in summer and translucent in winter. Thus, this species appears to deposit one translucent zone in its otoliths each year, and counts of these zones are probably a valid method to determine fish age. Comparisons of readings of D. eleginoides otoliths by workers from various institutions indicated a reasonable between-reader consistency, but still suggested that the otoliths were difficult to read. Von Bertalanffy growth parameters were calculated from the author’s readings only, separately by sex, for D. eleginoides caught from waters south of New Zealand to the Ross Sea, Antarctica, by longline and trawl fisheries. D. eleginoides appear to be moderately fast growing, at least to about age 10, and reasonably long-lived, reaching at least 50 years. Females grow at a faster rate and reach a larger size than males, but both sexes exhibit comparable maximum ages. Von Bertalanffy growth parameters were also calculated, separately by sex, for Antarctic toothfish ( Dissostichus mawsoni ) caught by the longline fishery in the northern Ross Sea. Otoliths of this species were interpreted similarly to those of D. eleginoides , but this method of ageing D. mawsoni is invalidated. D. mawsoni appears to be moderately fast growing, at least to about age 10, and can live for at least 35 years. This species probably grows at a slightly faster rate, and reaches a larger size than D. eleginoides .
Paul Tixier - One of the best experts on this subject based on the ideXlab platform.
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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
Marine Mammal Science, 2016Co-Authors: Paul Tixier, Guy Duhamel, Nicolas Gasco, Christophe GuinetAbstract:Sympatric 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.
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observations of a distinctive morphotype of killer whale orcinus orca type d from subantarctic waters
Polar Biology, 2011Co-Authors: Robert L. Pitman, John W Durban, Michael Greenfelder, Morton Jorgensen, Paula A Olson, Jordi Plana, Paul Tixier, Christophe Guinet, Jared R. TowersAbstract:Studies have shown that killer whale (Orcinus orca) communities in high latitudes regularly comprise assemblages of sympatric ‘ecotypes’—forms that differ in morphology, behavior, and prey preferences. Although they can appear superficially similar, recent genetic evidence suggests that breeding is assortative among ecotypes within individual communities, and species-level divergences are inferred in some cases. Here, we provide information on a recently recognized ‘type D’ killer whale based on photographs of a 1955 mass stranding in New Zealand and our own six at-sea sightings since 2004. It is the most distinctive-looking form of killer whale that we know of, immediately recognizable by its extremely small white eye patch. Its geographic range appears to be circumglobal in subantarctic waters between latitudes 40°S and 60°S. School sizes are relatively large (mean 17.6; range 9–35; n = 7), and although nothing is known about the type D diet, it is suspected to include fish because groups have been photographed around longline vessels where they reportedly depredate Patagonian toothfish (Dissostichus eleginoides).