In situ target strengths of Atlantic cod (Gadus morhua) and Atlantic mackerel (Scomber scombrus) in the Northwest Atlantic

1996 ◽  
Vol 53 (1) ◽  
pp. 87-98 ◽  
Author(s):  
Allen Clay ◽  
Martin Castonguay
Keyword(s):  
Gadus Morhua ◽  
Atlantic Cod ◽  
Northwest Atlantic ◽  
Atlantic Mackerel ◽  
Scomber Scombrus

Onshore Movements of Atlantic Mackerel (Scomber scombrus) in the Northern Gulf of St. Lawrence: Associations with Wind-Forced Advections of Warmed Surface Waters

1992 ◽  
Vol 49 (11) ◽  
pp. 2232-2241 ◽  
Author(s):  
Martin Castonguay ◽  
George A. Rose ◽  
William C. Leggett
Keyword(s):  
Surface Waters ◽  
Gadus Morhua ◽  
Atlantic Cod ◽  
Heated Surface ◽  
Atlantic Mackerel ◽  
Scomber Scombrus ◽  
Acoustic Techniques ◽  
Bottom Waters ◽  
Alongshore Wind Stress ◽  
Alongshore Wind

We employed fisheries acoustic techniques to assess the distribution and relative abundance of Atlantic mackerel (Scomber scombrus) at high resolution at Brador Bay in the northern Gulf of St. Lawrence in 1985 and 1986. These data were used to test the hypotheses that (1) onshore movements of mackerel are associated with wind-forced advections of heated surface waters and (2) mackerel are confined to waters having temperatures [Formula: see text]. Increased mackerel densities or "mackerel events" followed landward advections of heated surface waters in both 1985 and 1986. Landward advections of surface waters, and mackerel events, followed alongshore wind stress from the northeast. In our daytime observations, mackerel tended to concentrate in waters having temperatures of approximately 4 °C, near bottom, beneath warmer surface waters. However, the overall probability of mackerel occurrence inshore was much greater when near-bottom waters were warmer [Formula: see text]. Mackerel densities were not correlated with salinities, cross-shore winds, or currents but were negatively correlated with Atlantic cod (Gadus morhua) densities within the study site.

Pelagic fishes and the cod recruitment dilemma in the Northwest Atlantic

2000 ◽  
Vol 57 (7) ◽  
pp. 1321-1325 ◽  
Author(s):  
D P Swain ◽  
A F Sinclair
Keyword(s):  
Gadus Morhua ◽  
Atlantic Cod ◽  
Negative Relationship ◽  
Early Life History ◽  
Recruitment Rate ◽  
Clupea Harengus ◽  
Northwest Atlantic ◽  
Life History Stages ◽  
Pelagic Fishes ◽  
Predatory Fishes

Like most other stocks of Atlantic cod (Gadus morhua) in the Northwest Atlantic, cod in the southern Gulf of St. Lawrence declined to low abundance in the early 1990s. Recovery has been slow in contrast with the rapid recovery from similar levels of abundance in the mid-1970s. This difference reflects remarkably high prerecruit survival of cod in the earlier period of low abundance rather than unusually poor survival in the 1990s. The period of high prerecruit survival of cod coincided with the collapse of herring (Clupea harengus) and mackerel (Scomber scombrus) stocks resulting from overfishing. These pelagic fishes are potential predators or competitors of the early life history stages of cod. We report a strong negative relationship between the biomass of these pelagic fishes and recruitment rate of southern Gulf cod. This is consistent with the recent suggestion that the success of large predatory fishes may depend on "cultivation" effects in which the adults crop down forage fishes that are predators or competitors of their young. Our results also point to the possibility of a triangular food web involving cod, seals, and pelagic fishes, making it difficult to predict the effect of a proposed cull of seals on the recovery of cod.

Recruitment to Northwest Atlantic Cod (Gadus morhua) and Haddock (Melanogrammus aeglefinus) Stocks: Influence of Stock Size and Climate

1987 ◽  
Vol 44 (1) ◽  
pp. 26-39 ◽  
Author(s):  
J. Anthony Koslow ◽  
Keith R. Thompson ◽  
William Silvert
Keyword(s):  
Large Scale ◽  
Gadus Morhua ◽  
Reproductive Output ◽  
Atlantic Cod ◽  
Low Frequency ◽  
Melanogrammus Aeglefinus ◽  
Northwest Atlantic ◽  
Biological Variables ◽  
Low Frequency Variability ◽  
Haddock Melanogrammus Aeglefinus

Year-class success of both Atlantic cod (Gadus morhua) and haddock (Melanogrammus aeglefinus) stocks in the northwest Atlantic exhibits large-scale coherence and low-frequency variability with apparent periodicities of 10–20 yr. Several physical and biological variables in the region exhibit similar large-scale coherence and apparent periodicity. Multiple regression analysis indicates that year-class success in northwest Atlantic cod stocks tends to be associated with large-scale meteorological patterns and offshore winds. Recruitment to most haddock stocks from the Scotian Shelf to Georges Bank is negatively associated with abundance of 0-group mackerel, which may be due to predation over winter and/or to a combination of environmental features including sea-surface temperature, large-scale atmospheric pressure systems, and freshwater outflows. Statistical analyses often did not define a unique set of variables that best predicted fishery recruitment due to widespread intercorrelations among environmental processes and the likelihood that not all relevant processes entered directly into the analyses. There is little evidence that stock reproductive output during the study period was significantly related to year-class success.

scholarly journals Characterization of a novel alloherpesvirus from Atlantic cod (Gadus morhua)

2011 ◽  
Vol 24 (1) ◽  
pp. 65-73 ◽  
Author(s):  
Mar Marcos-Lopez ◽  
Thomas B. Waltzek ◽  
Ronald P. Hedrick ◽  
Dolores V. Baxa ◽  
Amber F. Garber ◽  
...  
Keyword(s):  
Gadus Morhua ◽  
Virus Isolation ◽  
Atlantic Cod ◽  
International Committee ◽  
Atpase Subunit ◽  
Transmission Electron ◽  
Viral Particles ◽  
Infected Cells

Alloherpesviruses affect freshwater and marine fish species. The aim of the current study was to characterize a novel alloherpesvirus in Atlantic cod ( Gadus morhua). Samples were processed for histopathology, transmission electron microscopy (TEM), virus isolation, molecular characterization, and in situ hybridization (ISH). Histopathology revealed that the infection was restricted to the gills and that it induced cytomegaly in infected cells. By TEM, numerous viral particles with morphology compatible with a herpesvirus were observed inside the cytomegalic cells. To characterize this new agent, polymerase chain reaction amplified regions of the ATPase subunit of the terminase, and DNA polymerase genes were sequenced. Phylogenetic analysis revealed strongest similarity with alloherpesviruses belonging to the genus Ictalurivirus and Salmonivirus. The ISH showed specific labeling of nuclear inclusions in the cytomegalic cells. While virus isolation was unsuccessful, the results obtained through different diagnostic tests in the present study confirm the discovery of a new alloherpesvirus affecting Atlantic cod. The authors propose the formal species designation Gadid herpesvirus 1 (GaHV-1) to be considered for approval by the International Committee on the Taxonomy of Viruses.

scholarly journals Acoustic backscatter by schools of adult Atlantic mackerel

2007 ◽  
Vol 64 (6) ◽  
pp. 1145-1151 ◽  
Author(s):  
Natalia Gorska ◽  
Rolf J. Korneliussen ◽  
Egil Ona
Keyword(s):  
Cross Sections ◽  
Relative Frequency ◽  
Acoustic Properties ◽  
Acoustic Backscatter ◽  
High Frequencies ◽  
Fish Size ◽  
Atlantic Mackerel ◽  
Scomber Scombrus ◽  
Scattering Spectra

Abstract Gorska, N., Korneliussen, R. J., and Ona, E. 2007. Acoustic backscatter by schools of adult Atlantic mackerel. – ICES Journal of Marine Science, 64: 1145–1151. The extent of acoustic backscatter by schools of adult Atlantic mackerel (Scomber scombrus) is investigated to improve biomass estimates. Previous studies involving modelled scattering from individual mackerel showed that backscattering at high frequencies is dominated by the contribution from the backbone. Accurate predictions of the scattering spectra require consideration of backscattering from the entire skeleton, including details of the bone shapes and their acoustic properties. Here, the backscattering cross-sections from mackerel flesh and backbone are estimated theoretically from 18 to 364 kHz and averaged over fish size and tilt angle, then compared with in situ measurements of volume backscattering from mackerel schools. Based on the comparisons, some gross features of the observed relative frequency response are explained, and recommendations for further studies suggested.

Taking the bait: in situ voluntary ingestion of acoustic transmitters by Atlantic cod (Gadus morhua)

2002 ◽  
pp. 287-292 ◽  
Author(s):  
Paul D. Winger ◽  
Barry R. McCallum ◽  
Stephen J. Walsh ◽  
Joseph A. Brown
Keyword(s):  
Gadus Morhua ◽  
Atlantic Cod

Usefulness of Fourier Analysis of Otolith Shape for Atlantic Mackerel (Scomber scombrus) Stock Discrimination

1991 ◽  
Vol 48 (2) ◽  
pp. 296-302 ◽  
Author(s):  
Martin Castonguay ◽  
Patrick Simard ◽  
Pierre Gagnon
Keyword(s):  
Stock Structure ◽  
Discriminant Functions ◽  
Position Effects ◽  
Northwest Atlantic ◽  
Otolith Shape ◽  
Atlantic Mackerel ◽  
Scomber Scombrus ◽  
The North ◽  
Stock Discrimination ◽  
The North Sea

We compared shapes of Atlantic mackerel (Scomber scombrus) sagittae between the two contingents (i.e. spawning groups) from the Northwest Atlantic and between the stocks from the Northwest Atlantic and the North Sea to evaluate whether otolith shape could differentiate between the two contingents in a mixed fishery. We quantified shapes with the Fourier series, an objective and rapid method which decomposes a shape's outline into a series of sinusoids. To determine a correct way to compare contingents/stocks, we first assessed four intracontingent effects on otolith shapes. Age and year-class effects were significant, while sex and bilateral position effects were not. This temporal instability in shapes indicates that confounding effects of age and year-class on otolith shapes need to be assessed carefully before drawing conclusions on stock structure. It also shows that comparative studies of otolith shapes with Fourier descriptors are not useful for mackerel contingent discrimination. The power of discriminant functions to correctly classify test mackerel samples separated by age and sampling year, on the basis of otolith shape, was better for comparisons between the stocks than for those between the contingents.

Time course of gametogenesis in Northwest Atlantic cod (Gadus morhua)

1997 ◽  
Vol 54 (S1) ◽  
pp. 122-131 ◽  
Author(s):  
M PM Burton ◽  
R M Penney ◽  
S Biddiscombe
Keyword(s):  
Time Course ◽  
Gadus Morhua ◽  
Atlantic Cod ◽  
Northwest Atlantic

Peculiarities in ovarian structure leading to multiple-year delays in oogenesis and possible senescence in Atlantic cod, Gadus morhua L.

2000 ◽  
Vol 78 (10) ◽  
pp. 1840-1844 ◽  
Author(s):  
Rick M Rideout ◽  
Margaret PM Burton
Keyword(s):  
Atlantic Ocean ◽  
Reproductive Cycle ◽  
Gadus Morhua ◽  
East Coast ◽  
Atlantic Cod ◽  
Spawning Season ◽  
Northwest Atlantic ◽  
Spawning Cycle ◽  
Ovarian Structure

Five specimens of female Atlantic cod, Gadus morhua L., four collected during regular surveys of the northwest Atlantic Ocean, had ovarian structures that suggested that multiple-year interruptions were occurring in the spawning cycle of these fish. One specimen was experiencing a minimal 2-year delay in its reproductive cycle because the ovary contained only oogonia, which would have had to mature before any spawning could occur. Two other specimens did not contain oogonia or perinucleolar-stage oocytes, suggesting that these ovaries were senescent. Another two ovaries, one removed from a broodstock female and one taken from a female collected off Newfoundland's east coast, contained large masses of resorbing hyaline oocytes, which would likely have impaired the normal release of hydrated oocytes in the next spawning season.

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