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  • 1
    Electronic Resource
    Electronic Resource
    Oxford, UK : Blackwell Publishing Ltd
    Aquaculture research 24 (1993), S. 0 
    ISSN: 1365-2109
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition
    Notes: High resolution ultrasound scanning was tested as a non-invasive technique for monitoring oocyte maturation and ovulalion in the Atlantic halibut Hippoglossus hippoglossus (L.). Female broodstock halibut were examined using a 7.5-Mhz linear ultrasound transducer, prior to and during spawning. Representative images of halibut ovaries are presented and discussed. Individual oocytes of spawning females were discernible during oocyte final maturation, due to the large increase in volume caused by water uptake. The yolky (vitellogenic) cocytes of pre-spawning fish were more reflective to ultrasound than hydrating oocytes. The resulting differences in depth of ultrasound penetration permitted easy distinction of pre-spawning from spawning females. In addition, short-term changes in the depth of ultrasound penetration were observed during repeated scanning of a spawning female, owing to progressive hydration of the oocyte batch destined for ovulation. Although of similar diameter, hydrating oocytes in the ovarian tissue could be discerned from eggs in the ovarian lumen because of the different acoustic properties of the surrounding media. The findings of the present study are considered promising for the future routine use of ultrasonography in halibut broodstock management.
    Type of Medium: Electronic Resource
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  • 2
    Electronic Resource
    Electronic Resource
    Oxford, UK : Blackwell Publishing Ltd
    Aquaculture research 29 (1998), S. 0 
    ISSN: 1365-2109
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition
    Notes: The first attempts to rear Atlantic halibut, Hippoglossus hippoglossus L., larvae were carried out in Norway in the period from 1974 to 1980, when ripe adult specimens of Atlantic halibut were net-caught, and stripped for eggs and milt. Both incubation of yolk-sac larvae and first-feeding were carried out in large submerged plastic bags and the larval food consisted of natural zooplankton collected from surrounding lagoon water. This semi-extensive production method was further developed and led to the establishment of several commercial production trials by the end of the 1980s. During recent years, research has been focused on intensive methods for first-feeding and the combined effort of several research institutes has resulted in a reliable production method. During the late 1980s and early 1990s, the main research activity was focused on the biology of and rearing techniques for eggs and yolk-sac larvae. These techniques provided satisfactory yields for several years. However, during the past few years, a certain decrease in survival through the yolk-sac stage has been experienced at several hatcheries. Since the early 1990s, the first-feeding period has represented the bottleneck in the development of a reliable rearing method. The main effort has been concentrated on system configuration and on improving live prey quality. In the future, new feeding strategies including further improvement of live prey (i.e. Artemia), the use of copepods and early weaning onto a formulated diets should be emphasized. Further research on hygiene and technological improvements is needed to increase growth and survival through metamorphosis.
    Type of Medium: Electronic Resource
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  • 3
    Electronic Resource
    Electronic Resource
    Oxford, UK : Blackwell Publishing Ltd
    Aquaculture research 29 (1998), S. 0 
    ISSN: 1365-2109
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition
    Notes: Atlantic halibut, Hippoglossus hippoglossus L., larvae were reared under four different Artemia feeding regimes for 40 days from day 20 post first feeding. Three Artemia enrichments were used: Super Selco™ (SS), AlgaMac 2000™ (AM) and a particulate mix of AlgaMac 2000™ with tuna orbital oil (TOO/AM). The SS and AM Artemia were tested in three different combinations: (1) a 1:1 ratio continuously to day 60 (AM/SS); (2) a 1:1 ratio to day 41, then AM only (AM/SS-41): and (3) AM only to day 41, then a 1:1 ratio (AM-41). The fourth treatment comprised TOO/AM Artemia, which was fed continuously. At day 60 post first feeding, measurements were made of survival and growth rates, postmetamorphic characteristics (i.e. eye migration and pigment distribution), and lipid composition. The mean survival rates ranged from 65.1% to 84.5%. Specific growth rates varied from 7.64 to 8.13. The eye migration indices were between 2.3 and 2.6. These parameters did not differ significantly among treatments (P 0.05). A significantly greater proportion of fry (P〈0.05) exhibited‘perfect metamorphosis’(correct pigment distribution and complete eye migration) in the AM/ SS-41 and AM-41 treatments (59.8 ± 3.03% and 54.6 ± 1.08%, respectively) compared to the AM/SS and TOO/AM treatments (35.9 ± 4.02% and 39.9 ± 6.43%, respectively). The fatty acid compositions of livers and eyes varied according to feeding regime, but did not correspond to the metamorphosis characteristics of the fry.
    Type of Medium: Electronic Resource
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  • 4
    Electronic Resource
    Electronic Resource
    Oxford, UK : Blackwell Publishing Ltd
    Aquaculture research 28 (1997), S. 0 
    ISSN: 1365-2109
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition
    Notes: The karyotype of the Atlantic halibut, Hippoglossus hippoglossus, (Linnaeus, 1758) consists of 24 pairs of chromosomes (2n= 48) all of which are subtelocentric or acrocentric. The number and morphology of the chromosomes of the Atlantic halibut is therefore similar to most other pleuronectid fish studied.
    Type of Medium: Electronic Resource
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  • 5
    ISSN: 1365-2109
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition
    Notes: Abstract. Lipid class and fatty acid analyses were carried out on eight batches of pre-fertilized eggs of Atlantic halibut, Hippoglossus hippoglossus (L.). These batches were classified as ‘viable’ or ‘non-viable’ according to fertilization rate, blastomere symmetry and incubation success. The lipid class and fatty acid compositions were very similar between egg categories with exception of cholesterol which was shown to be significantly greater in the ‘non-viable’ eggs. Polar lipid classes predominated (67·1% and 67·0% of the total lipid for ‘viable’ and ‘non-viable’ egg batches respectively), with phosphatidylcholine (PC) being the major class (43·2% and 43·5%) and triacylglycerol (TAG) the main neutral lipid class (18·8% and 17·8%). Gas liquid chromatography of fatty acid methyl esters from the total lipid revealed no significant differences in fatty acid composition. The fatty acid profiles of viable egg batches showed five major fatty acids 16:0 (17·3%), 18:0 (4·8%), 18:1n-9 (9%), 20:5n-3 (119%) and 22:6n-3 (25·9%). The results are discussed in terms of the potential role of lipids as egg quality determinants in fish.
    Type of Medium: Electronic Resource
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