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  • 1
    Online Resource
    Online Resource
    Timecourse of oocyte development in saithe Pollachius virens
    Wiley ; 2017
    In:  Journal of Fish Biology Vol. 90, No. 1 ( 2017-01), p. 109-128
    Details
    In: Journal of Fish Biology, Wiley, Vol. 90, No. 1 ( 2017-01), p. 109-128
    Abstract: Wild caught North Sea saithe Pollachius virens were monitored for growth, sex steroid profiles and oocyte development pre‐spawning and measured for egg size and group fecundity during the spawning season in the laboratory. Vitellogenesis commenced in late October–early November, at a leading cohort size ( C L ) of c. 250 µm, after which oocytes grew rapidly in size until spawning started in February. Notably, a distinct cortical alveoli stage was virtually absent with yolk granules observed in developing oocytes at the very beginning of vitellogenesis. Little atresia was observed pre‐spawning, but atretic re‐absorption of remnant oocytes containing yolk granules was found in all females immediately post‐spawning. As expected, concentrations of sex steroids, oestradiol‐17β (females), testosterone (both sexes) and 11‐ketotestosterone (both sexes), increased pre‐spawning before dropping post‐spawning. The present experiment provides the first validation of sex steroid levels in P. virens . Post‐ovulatory follicles were visible in histological sections from female gonads 9–11 months post‐spawning, but then disappeared. Spawning commenced around a C L of c. 750 µm (700–800 µm). Hydrated oocytes (eggs) measured between 1·04 and 1·31 mm (mean = 1·18 mm) with decreasing sizes towards the end of spawning. The average estimated realized fecundity was c. 0·84 million eggs (median female total length, L T = 60 cm). Spawning lasted from 13 February to 29 March.
    Type of Medium: Online Resource
    ISSN: 0022-1112 , 1095-8649
    URL: Issue
    URL: Article
    DOI: 10.1111/jfb.2017.90.issue-1
    DOI: 10.1111/jfb.13161
    Language: English
    Publisher: Wiley
    Publication Date: 2017
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  • 2
    Online Resource
    Online Resource
    Potential Variability in the Paternal Contribution to Stock Reproductive Potential of Northeast Arctic Cod ( Gadus morhua )
    Northwest Atlantic Fisheries Organization (NAFO) ; 2008
    In:  Journal of Northwest Atlantic Fishery Science Vol. 41 ( 2008-08-18), p. 71-83
    Details
    In: Journal of Northwest Atlantic Fishery Science, Northwest Atlantic Fisheries Organization (NAFO), Vol. 41 ( 2008-08-18), p. 71-83
    Type of Medium: Online Resource
    ISSN: 0250-6408 , 1682-9786 , 1811-8224
    URL: Article
    DOI: 10.2960/J.v41.m619
    Language: English
    Publisher: Northwest Atlantic Fisheries Organization (NAFO)
    Publication Date: 2008
    detail.hit.zdb_id: 2114897-1
    detail.hit.zdb_id: 155652-6
    SSG: 21,3
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  • 3
    Online Resource
    Online Resource
    Ovulatory Rhythm and a Method to Determine the Stage of Spawning in Atlantic Cod ( Gadus morhua )
    Canadian Science Publishing ; 1990
    In:  Canadian Journal of Fisheries and Aquatic Sciences Vol. 47, No. 6 ( 1990-06-01), p. 1185-1193
    Details
    In: Canadian Journal of Fisheries and Aquatic Sciences, Canadian Science Publishing, Vol. 47, No. 6 ( 1990-06-01), p. 1185-1193
    Abstract: The size frequency distribution of the vitellogenic oocytes in Atlantic cod (Gadus morhua) changes in a predictable manner as spawning progresses. This change was studied by sampling successive batches of eggs from reared cod kept in the laboratory. The shape of the vitellogenic oocyte mode was described by measuring the diameter, standard deviation, and skewness and kurtosis. Linear regressions were derived which related the portion of the total number of eggs spawned per season (PES) to the number of vitellogenic oocytes per gram of the ovary and in relation to the standard deviation of the distribution. This method which allows the PES in a spawning fish to be estimated has the following applications. For fish stock assessment purposes fecundity estimates can be made on spawning rather than prespawning fish and residence times on spawning grounds can be calculated. In addition successive batches of eggs can be identified and studied. This is important in hormonal and larval studies. A detailed description is given of the oocyte growth during the ovulatory rhythm. The rhythm consists of four periods: arrest, final growth, hydration, and ovulation. It is suggested that the egg size is determined during the final growth period.
    Type of Medium: Online Resource
    ISSN: 0706-652X , 1205-7533
    URL: Article
    DOI: 10.1139/f90-138
    Language: English
    Publisher: Canadian Science Publishing
    Publication Date: 1990
    detail.hit.zdb_id: 7966-2
    detail.hit.zdb_id: 1473089-3
    SSG: 21,3
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  • 4
    Online Resource
    Online Resource
    Half a century of high-latitude fisheries oceanography research on the “recruitment problem” in Northeast Arctic cod ( Gadus morhua )
    Oxford University Press (OUP) ; 2023
    In:  ICES Journal of Marine Science Vol. 80, No. 5 ( 2023-06-29), p. 1179-1201
    Details
    In: ICES Journal of Marine Science, Oxford University Press (OUP), Vol. 80, No. 5 ( 2023-06-29), p. 1179-1201
    Abstract: Predicting recruitment in a reliable fashion is a great challenge within operational fisheries advice. Here, we consulted the unique but undercommunicated IMR Cod Larva Project (1975–1990), its spin-offs, placed in an international era of advancements over the last 50 years to glance into the future. Few initiatives of this kind have applied such extensive research approaches, spanning from laboratory, mesocosm, tank, and field studies to process modelling. The “critical period” concept appeared misleading, covering months rather than days of the early life history stages (ELHS) of Northeast Arctic cod. Larval feeding success was strongly modified by improved encounter rates from wind-induced turbulence. In addition, the following maternal effect studies evidenced that the dynamics of stock demography prior to spawning should be upheld to promote recruitment success. Although we now have lower-trophic level models as well as ELHS individual-based models, such models are still insufficiently reflecting the needed spatiotemporal resolution. The same problem applies to climate/circulation models. Nevertheless, this long-lasting research has significantly improved the mechanistic understanding of ELHS dynamics but also of the more predictable adult reproductive parameters. Based on a “to-list list,” we suggest research avenues that should be pursued to further improve our ability predicting recruitment strength in marine fish stocks.
    Type of Medium: Online Resource
    ISSN: 1054-3139 , 1095-9289
    URL: Article
    DOI: 10.1093/icesjms/fsad073
    Language: English
    Publisher: Oxford University Press (OUP)
    Publication Date: 2023
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    detail.hit.zdb_id: 1468003-8
    detail.hit.zdb_id: 29056-7
    SSG: 12
    SSG: 21,3
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  • 5
    Online Resource
    Online Resource
    Poleward spawning of Atlantic mackerel ( Scomber scombrus ) is facilitated by ocean warming but triggered by energetic constraints
    Oxford University Press (OUP) ; 2023
    In:  ICES Journal of Marine Science ( 2023-06-23)
    Details
    In: ICES Journal of Marine Science, Oxford University Press (OUP), ( 2023-06-23)
    Abstract: The Northeast Atlantic mackerel is an income breeder with indeterminate fecundity, spawning in multiple batches at optimal temperatures around 11°C in the upper water column during February–July along the continental shelf from 36–62°N. Based on macroscopic staging of gonads (N ∼62000) collected in 2004–2021, we detected an on-going extension of spawning activities into the Norwegian Sea feeding area (62–75°N), reaching stable levels around 2012 onwards. This poleward expansion increased as more fish entered the area, whilst the maximum proportions of spawners concurrently dropped from about 75 to 15% from May to July. Detailed histological examinations in 2018 confirmed the macroscopic results but clarified that 38% of the spawning-capable females in July terminated their spawning by atresia. We suggest that increased access to suitable spawning areas (≥10°C), following ocean warming from 2002 onwards, functions as a proximate cause behind the noticed expansion, whereas the ultimate trigger was the historic drop in body growth and condition about 10 years later. Driven by these energetic constraints, mackerel likely spawn in the direction of high prey concentrations to rebuild body resources and secure the future rather than current reproduction success. The ambient temperature that far north is considered suboptimal for egg and larval survival.
    Type of Medium: Online Resource
    ISSN: 1054-3139 , 1095-9289
    URL: Article
    DOI: 10.1093/icesjms/fsad098
    Language: English
    Publisher: Oxford University Press (OUP)
    Publication Date: 2023
    detail.hit.zdb_id: 2463178-4
    detail.hit.zdb_id: 1468003-8
    detail.hit.zdb_id: 29056-7
    SSG: 12
    SSG: 21,3
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  • 6
    Online Resource
    Online Resource
    Oocyte size and structure in relation to blood plasma steroid hormones in individually monitored, spawning Atlantic cod
    Wiley ; 1996
    In:  Journal of Fish Biology Vol. 49, No. 6 ( 1996-12), p. 1197-1215
    Details
    In: Journal of Fish Biology, Wiley, Vol. 49, No. 6 ( 1996-12), p. 1197-1215
    Type of Medium: Online Resource
    ISSN: 0022-1112 , 1095-8649
    URL: Issue
    URL: Article
    DOI: 10.1111/jfb.1996.49.issue-6
    DOI: 10.1111/j.1095-8649.1996.tb01789.x
    Language: English
    Publisher: Wiley
    Publication Date: 1996
    detail.hit.zdb_id: 410564-3
    detail.hit.zdb_id: 1471958-7
    SSG: 21,3
    SSG: 12
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  • 7
    Online Resource
    Online Resource
    Reproductive biology of horse mackerel Trachurus capensis and Trachurus trecae in Namibia and Angola
    National Inquiry Services Center (NISC) ; 2013
    In:  African Journal of Marine Science Vol. 35, No. 2 ( 2013-08), p. 141-150
    Details
    In: African Journal of Marine Science, National Inquiry Services Center (NISC), Vol. 35, No. 2 ( 2013-08), p. 141-150
    Type of Medium: Online Resource
    ISSN: 1814-232X , 1814-2338
    URL: Article
    DOI: 10.2989/1814232X.2013.805595
    Language: English
    Publisher: National Inquiry Services Center (NISC)
    Publication Date: 2013
    detail.hit.zdb_id: 2192754-6
    detail.hit.zdb_id: 2129388-0
    SSG: 12
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  • 8
    Online Resource
    Online Resource
    Variability of northeast Arctic cod (Gadus morhua) distribution on the main spawning grounds in relation to biophysical factors
    Oxford University Press (OUP) ; 2014
    In:  ICES Journal of Marine Science Vol. 71, No. 6 ( 2014-09-01), p. 1317-1331
    Details
    In: ICES Journal of Marine Science, Oxford University Press (OUP), Vol. 71, No. 6 ( 2014-09-01), p. 1317-1331
    Abstract: Early life stages may on average gain a survival benefit from the regular return of parent fish to the same spawning grounds. Such areas may have a considerable spatial extent, occupation of which varies between spawning seasons. Northeast Arctic cod (Gadus morhua) is an ideal candidate to pinpoint the most influential biophysical factors in these respects due to its data richness and apparently strong “homing” behaviour. Their main spawning grounds, off northern Norway, are split in two by the Lofoten archipelago, and in the previous decade strong spawning activity was observed on the seaward continental shelf (Yttersida), while in recent years spawning activity in the wide fjord (Vestfjorden), that separates the islands from the Norwegian mainland, has again increased. Time-series of egg distribution were available from the 1980s, 1990s, and 2004–2012. We used several fixed and random factors to construct a statistical model for the distribution of recently spawned eggs, and hence, spawning adults in either area. We show that the most relevant covariates for the spatial distribution of eggs in Vestfjorden are local temperature and bathymetry, while at Yttersida influence affecting the whole stock, like regional ocean climate and age structure appear more important. Therefore, spawning inside the fjord may be constrained by suboptimal environmental conditions. Yttersida may be occupied by fish which have been displaced out of Vestfjorden when preferred conditions there are of limited extent.
    Type of Medium: Online Resource
    ISSN: 1054-3139 , 1095-9289
    URL: Article
    DOI: 10.1093/icesjms/fsu126
    Language: English
    Publisher: Oxford University Press (OUP)
    Publication Date: 2014
    detail.hit.zdb_id: 2463178-4
    detail.hit.zdb_id: 1468003-8
    detail.hit.zdb_id: 29056-7
    SSG: 12
    SSG: 21,3
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  • 9
    Online Resource
    Online Resource
    Oocyte development in captive Atlantic horse mackerel Trachurus trachurus
    Oxford University Press (OUP) ; 2009
    In:  ICES Journal of Marine Science Vol. 66, No. 4 ( 2009-05-01), p. 623-630
    Details
    In: ICES Journal of Marine Science, Oxford University Press (OUP), Vol. 66, No. 4 ( 2009-05-01), p. 623-630
    Abstract: Ndjaula, H. O. N., Hansen, T., Krüger-Johnsen, M., and Kjesbu, O. S. 2009. Oocyte development in captive Atlantic horse mackerel Trachurus trachurus. – ICES Journal of Marine Science, 66: 623–630. This 13-month experimental study focused on developing oocyte production in 101 adult female Atlantic horse mackerel. In addition, proxies of energy patterns in relation to oocyte development were investigated. The fish were captured off western Norway and fed to satiation from October 2005 to November 2006 in two replicate adjacent circular tanks. Monthly histological examination of the ovaries indicated that vitellogenic oocytes were present at all times throughout the study period, but that oocyte development did not progress past the incipient migratory nucleus stage. The oocyte diameter (OD) threshold between pre-vitellogenic and vitellogenic oocytes and the mean OD of the leading cohort were investigated, and no hiatus was observed within the OD size distribution around the 185-µm pre-vitellogenic and vitellogenic threshold. Variation in gonadosomatic index, hepatosomatic index, condition factor, and fat content (as measured by the use of a Distell Fish Fatmeter) increased with oocyte development. The observed development of oocyte recruitment and the absence of a hiatus in the oocyte distribution are characteristics of an asynchronous spawner. The species seems to have a prolonged spawning season, judging from the advanced and variety of maturity stages throughout the study period.
    Type of Medium: Online Resource
    ISSN: 1095-9289 , 1054-3139
    URL: Article
    DOI: 10.1093/icesjms/fsp032
    Language: English
    Publisher: Oxford University Press (OUP)
    Publication Date: 2009
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    detail.hit.zdb_id: 1468003-8
    detail.hit.zdb_id: 29056-7
    SSG: 12
    SSG: 21,3
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  • 10
    Online Resource
    Online Resource
    Differences in growth performance between Arcto-Norwegian and Norwegian coastal cod reared under identical conditions
    Wiley ; 1996
    In:  Journal of Fish Biology Vol. 49, No. 1 ( 1996-07), p. 108-119
    Details
    In: Journal of Fish Biology, Wiley, Vol. 49, No. 1 ( 1996-07), p. 108-119
    Type of Medium: Online Resource
    ISSN: 0022-1112 , 1095-8649
    URL: Issue
    URL: Article
    DOI: 10.1111/jfb.1996.49.issue-1
    DOI: 10.1111/j.1095-8649.1996.tb00008.x
    Language: English
    Publisher: Wiley
    Publication Date: 1996
    detail.hit.zdb_id: 410564-3
    detail.hit.zdb_id: 1471958-7
    SSG: 21,3
    SSG: 12
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