Spawning

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Olav Sigurd Kjesbu - One of the best experts on this subject based on the ideXlab platform.

  • Evaluation of the frequency of skipped Spawning in Norwegian spring-Spawning herring
    Journal of Sea Research, 2011
    Co-Authors: James Kennedy, Aril Slotte, Jon Egil Skjæraasen, Richard D.m. Nash, Audrey J. Geffen, Olav Sigurd Kjesbu
    Abstract:

    Based upon an under-representation of second time spawners on the Spawning grounds between 1935 and 1973, researchers have suggested that Norwegian spring-Spawning (NSS) herring (Clupea harengus) frequently skip their second Spawning event. In order to evaluate this claim with direct evidence, herring were collected over a period of three years from statutory surveys and commercial catches over a wide area covering the feeding, over-wintering and Spawning grounds. The development stage of the ovaries was assessed and the intensity of atresia quantified. Only a negligible number of the analysed herring caught were considered likely to skip Spawning, thus this phenomenon does not appear to be a common feature of the NSS herring stock at present. In addition, considering the reproductive strategy of herring, it seems doubtful that skipping the second Spawning event has ever frequently occurred in this stock.

  • fecundity atresia and Spawning strategies of atlantic herring clupea harengus
    Canadian Journal of Fisheries and Aquatic Sciences, 2009
    Co-Authors: Cindy J G Van Damme, Mark Dickeycollas, Adriaan D. Rijnsdorp, Olav Sigurd Kjesbu
    Abstract:

    Atlantic herring (Clupea harengus) have contrasting Spawning strategies, with apparently genetically similar fish “choosing” different Spawning seasons, different egg sizes, and different Spawning areas. In the North Sea, both autumn- and winter-Spawning herring share the same summer feeding area but have different Spawning areas. Females of both Spawning types start their oocyte development in April–May. Oocyte development is influenced by the body energy content; during the maturation cycle, fecundity is down-regulated through atresia in relation to the actual body condition. Hence, fecundity estimates must account for the relative time of sampling. The down-regulation over the whole maturation period is approximately 20% in autumn- and 50% in winter-Spawning herring. The development of the oocytes is the same for both Spawning strategies until autumn when autumn spawners spawn a larger number of small eggs. In winter spawners, oocyte development and down-regulation of fecundity continues, resulting in ...

  • Effects of fish size on Spawning time in Norwegian spring‐Spawning herring
    Journal of Fish Biology, 2000
    Co-Authors: Aril Slotte, Arne Johannessen, Olav Sigurd Kjesbu
    Abstract:

    During October January in a northern Norwegian fjord system and in February- March at the main western Norway Spawning grounds, an index I G of gonad weight of spring-Spawning herring Clupea harengus in percentage of expected gonad weight at full maturity for a given total length L T tended to increase with L T in the range 27-31 cm as the proportion of recruit spawners decreased Insignificant differences in I G were found between L I groups in the range 32-37 cm (repeat spawners). This is contrary to that suggested in other studies and signifies that generally the stock spawns in only two waves, repeat spawners first and the recruit spawners second. I G also increased with somatic and total condition factor, which signifies that Spawning time may be influenced by summer feeding conditions.

Timothy Loher - One of the best experts on this subject based on the ideXlab platform.

  • analysis of match mismatch between commercial fishing periods and Spawning ecology of pacific halibut hippoglossus stenolepis based on winter surveys and behavioural data from electronic archival tags
    Ices Journal of Marine Science, 2011
    Co-Authors: Timothy Loher
    Abstract:

    The fishery for halibut (Hippoglossus stenolepis) in the eastern Pacific is closed during the boreal winter, roughly corresponding to the seasonal Spawning of the species. Opening and closing dates for each season are stipulated annually based on economics and biology. Historical surveys and data from electronic tags are analysed to assess the extent to which recent closures have encompassed the annual Spawning cycle of the species, as defined by migration to offshore Spawning sites, active Spawning, and return to feeding areas. These were assessed by calculating mean maximum daily depth profiles for fish exhibiting seasonal migration, calculating the date-specific proportions of the tagged population either migrating to or resident on their feeding or Spawning grounds, and examining the temporal distribution of spent and running fish in historical surveys along with evidence of Spawning contained in high-resolution tag data. The data indicate that fishery closures over the past 20 years have been consistently too short to protect the entirety of a migration period that begins as early as September and is not substantially completed until May. Additionally, some recent season openings have encroached on the active Spawning season. Failure to fully protect Spawning migrations may allow seasonal interception fisheries, and the selective removal of early and late spawners could cause changes in stock demographics, restrict effective Spawning, and influence long-term stock productivity, especially in the face of environmental variability.

  • characterization of active Spawning season and depth for eastern pacific halibut hippoglossus stenolepis and evidence of probable skipped Spawning
    Journal of Northwest Atlantic Fishery Science, 2008
    Co-Authors: Timothy Loher, Andrew C Seitz
    Abstract:

    The eastern Pacific halibut (Hippoglossus stenolepis ) fishery is prosecuted over a nine-month season with a provision to cease harvests if stock declines to historically-observed minimum Spawning biomass. The industry has requested to extend fishing into winter, but little information exists regarding potential impacts on Spawning aggregations or effective Spawning biomass. A strictly annual Spawning cycle is presumed, but some adults fail to undertake the offshore migration associated with continental slope Spawning. We examined depth records of halibut tagged with Pop-up Archival Transmitting (PAT) tags for evidence of offshore seasonal migration (n = 72). For tags that were physically recovered (n = 16) we identified the occurrence of abrupt (~100 m) mid-winter ascents, believed to be egg release. The active Spawning season, defined by occurrence of these rises, lasted from 27 December–8 March, at bottom depths of 278–594 m. Eighteen percent of tagged halibut remained onshore. Thirty-one percent of fish with detailed archival records did not exhibit Spawning rises, including all fish that remained onshore. Correcting for the possibility that some were likely immature, the data suggest that ~10% of the mature fish do not participate in the Spawning migration and 10–15% that migrate to deep water may not actively spawn. The data suggest that opening the commercial fishery in early spring would likely subject actively Spawning fish to fishing mortality, and could truncate the effective Spawning period. Natural rates of skip-Spawning and fisheries-induced reduction of the Spawning period relative to suitable larval rearing conditions could introduce temporal and regional variance into levels of effective Spawning biomass and warrant further investigation.

George A. Rose - One of the best experts on this subject based on the ideXlab platform.

  • atlantic cod gadus morhua feed during Spawning off newfoundland and labrador
    Ices Journal of Marine Science, 2012
    Co-Authors: Kyle J Krumsick, George A. Rose
    Abstract:

    We test a current assumption that Atlantic cod (Gadus morhua) off Newfoundland and Labrador, Canada, do not feed during the protracted Spawning season (March–September). Stomach contents were analysed from 10 473 cod from four Northwest Atlantic Fisheries Organization regions (2J, 3K, 3L, and 3Ps) over 9 years from which gonads were also analysed to determine sex and maturity status. Adult cod in Spawning condition did feed in all regions, usually at rates equivalent to or even greater than non-Spawning fish and juveniles. Both sexes fed during Spawning, though females consumed lesser amounts. Regional differences were evident. The total fullness index was greater in the northern (2J) than the southern (3Ps) region, with no consistent differences between spawners and non-spawners. The most southerly region (3Ps) exhibited the greatest prey diversity, the northern region (2J) the least. Shrimp was the major diet item in the northern regions. Capelin, zooplankton, crab, and other fish increased in importance to the south. Differences in prey items between non-Spawning and Spawning individuals of both sexes were possibly related to Spawning behaviour. Models using consumption rates should not assume that cod do not feed during the protracted Spawning season in these waters.

  • Do cod form Spawning leks? Evidence from a Newfoundland Spawning ground
    Marine Biology, 2006
    Co-Authors: Matthew J. S. Windle, George A. Rose
    Abstract:

    Catch and acoustic telemetry data were used to test three predictions of lekking behaviour in Atlantic cod (Gadus morhua L.) at a small-scale Spawning ground (∼25 km2) in Placentia Bay, Newfoundland: (1) that cod form male-skewed aggregations during Spawning; (2) Spawning arenas occur at consistent sites; and (3) on the arenas, there will be higher proportions of Spawning fish. Forty-two fishing sets from 1998 to 2003 indicated male-skewed sets early in the Spawning season (April) in 5 of 6 survey years. Male-skewed sets were consistently distributed at depths < 50 m and mostly in one part of the ground. The proportions of Spawning females and spent males were significantly higher in male-skewed sets, whereas sets with equal sex ratios had significantly higher proportions of immature males and spent females. In addition, cod of both sexes were significantly larger in male-skewed sets. Telemetric tracking of 25 cod in 2002 and 2003 (12 males, 13 females) indicated that both males and females were highly mobile while present on the Spawning ground. Overall, our results add support to the hypothesis that cod employ a lekking mating system.

  • skipped Spawning in female iteroparous fishes
    Fish and Fisheries, 2005
    Co-Authors: Rick M Rideout, George A. Rose, Margaret P M Burton
    Abstract:

    It is often assumed that iteroparous fishes spawn annually once reaching sexual maturity, but this is not always the case. This paper reviews available information on skipped Spawning in female teleost fishes. All instances of non-annual Spawning are described as one of three types (retaining, reabsorbing, resting), depending on where in the normal Spawning cycle development has been interrupted. Retaining ripe eggs is caused by conditions experienced during the Spawning season (fish density, mate availability, pollution), whereas failure to start vitellogenesis (resting) or the breakdown of all oocytes that enter into vitellogenesis (reabsorbing) is caused by factors experienced prior to the Spawning season (primarily temperature and poor nutrition). It is speculated that the relative shortage of data on non-annual Spawning may be because of difficulties in identifying non-reproductive individuals. In an attempt to rectify this situation, the criteria needed to identify females undergoing the three forms of Spawning omission are presented in terms of external appearance of gonads, gonad indices, and histological analysis. The energy saved by not Spawning in a poor year may lead to increased survival and the probability of Spawning in subsequent years. As the cumulative number of progeny gained by surviving to spawn in multiple subsequent years outweighs the number of progeny lost by not Spawning in a given single year, occasional omission of Spawning may constitute an adaptive trait in long-lived iteroparous fishes.

Adriaan D. Rijnsdorp - One of the best experts on this subject based on the ideXlab platform.

  • Effects of fishing during the Spawning period: implications for sustainable management
    Reviews in Fish Biology and Fisheries, 2015
    Co-Authors: Harriët M. J. Overzee, Adriaan D. Rijnsdorp
    Abstract:

    While fishery closures during the Spawning season are commonplace, direct evidence for their benefit is mainly restricted to species forming large Spawning aggregations. This paper analyses the conditions under which Spawning closures could contribute to sustainable fisheries management by reviewing how fishing during Spawning may affect the physiology, behaviour and ecology of individuals and how this may influence the dynamics and the genetics of the population. We distinguish between the effects of fishing activities in relation to mortality, disturbance of Spawning activity, and impact on Spawning habitat. Spawning closures may be of benefit it they: (1) reduce the fishing mortality of the large and older spawners; (2) avoid negative effects on Spawning habitats; (3) reduce the risk of over-exploitation in species which form large Spawning aggregations; (4) reduce the evolutionary effects on maturation and reproductive investment; and (5) reduce the risk of over-exploitation of specific Spawning components. The contribution of Spawning closures to sustainable fisheries will differ among species and depends on the complexity of the Spawning system, the level of aggregation during Spawning and the vulnerability of the Spawning habitat. The importance of these closures depends on the degree of population depletion but does not cease when populations are ‘healthy’ (i.e. no sign that recruitment is impaired).

  • fecundity atresia and Spawning strategies of atlantic herring clupea harengus
    Canadian Journal of Fisheries and Aquatic Sciences, 2009
    Co-Authors: Cindy J G Van Damme, Mark Dickeycollas, Adriaan D. Rijnsdorp, Olav Sigurd Kjesbu
    Abstract:

    Atlantic herring (Clupea harengus) have contrasting Spawning strategies, with apparently genetically similar fish “choosing” different Spawning seasons, different egg sizes, and different Spawning areas. In the North Sea, both autumn- and winter-Spawning herring share the same summer feeding area but have different Spawning areas. Females of both Spawning types start their oocyte development in April–May. Oocyte development is influenced by the body energy content; during the maturation cycle, fecundity is down-regulated through atresia in relation to the actual body condition. Hence, fecundity estimates must account for the relative time of sampling. The down-regulation over the whole maturation period is approximately 20% in autumn- and 50% in winter-Spawning herring. The development of the oocytes is the same for both Spawning strategies until autumn when autumn spawners spawn a larger number of small eggs. In winter spawners, oocyte development and down-regulation of fecundity continues, resulting in ...

Ulf Dieckmann - One of the best experts on this subject based on the ideXlab platform.

  • the logic of skipped Spawning in fish
    Canadian Journal of Fisheries and Aquatic Sciences, 2006
    Co-Authors: Christian Jorgensen, Øyvind Fiksen, Bruno Ernande, Ulf Dieckmann
    Abstract:

    That sexually mature fish skip reproduction, especially in response to poor condition, has been documented in many species. We present results from an energy-allocation life history model that shed light on the underlying logic of skipped Spawning, based on the Northeast Arctic stock of Atlantic cod (Gadus morhua). The model predicts that skipped Spawning is a regular phenomenon, with up to 30% of the sexually mature biomass skipping Spawning. Spawning should be skipped if the expected future gain in reproductive output, discounted by survival, more than bal- ances the expected reproductive success the current year. Skipped Spawning was most common (i) among potential second-time spawners and (ii) early in life, (iii) when fishing mortality at the Spawning grounds was high, (iv) when fishing mortality at the feeding grounds was low, (v) when natural mortality was low, and (vi) when the energetic and mortality costs associated with migration and Spawning were high. Cod skipped Spawning more often when food avail- ability was both increased (opportunities for better growth) and decreased (too little energy for gonad development), and this pattern interacted with mortality rate. We conclude that skipped Spawning may be more widespread than appreciated and highlight potential consequences for the understanding of stock-recruitment relationships.