Structure and Interannual Variability of the Plankton and its Environment off Southwest Nova Scotia in Late Spring and Early Summer

1989 ◽  
Vol 46 (S1) ◽  
pp. s44-s54 ◽  
Author(s):  
J. Anthony Koslow ◽  
R. Ian Perry ◽  
Peter C. F. Hurley ◽  
Robert O. Fournier
Keyword(s):  
Nova Scotia ◽  
Chlorophyll A ◽  
North Atlantic ◽  
Atmospheric Pressure ◽  
Gadus Morhua ◽  
Atlantic Cod ◽  
Early Summer ◽  
Tidal Mixing ◽  
Secondary Importance ◽  
The North

Consistent alongshore and/or onshore–offshore gradients in temperature, salinity, and inorganic nutrient were observed off southwest Nova Scotia in June/July, 1981–85. The distributions were established primarily by mixing of relatively warm, high-salinity, nutrient-rich Slope Water with the cold, low-salinity, nutrient-poor water of the Nova Scotia Current. Tidal mixing and frontal dynamics were of secondary importance. Consistent with the distribution of nutrient and the earlier onset of stratification offshore, chlorophyll a concentrations were generally highest offshore and lowest inshore, and the distributions of Zooplankton displacement volume and of dominant copepod species were similar. Salinity, nutrient, and chlorophyll a concentrations and the abundance of zoo-plankton were all generally higher throughout the spring of 1985 than in 1983–84. In 1985, there was greater upwelling and Slope Water influence and decreased flow of the shelf current. This was associated with a reversal of the North Atlantic atmospheric pressure anomaly field, which led to predominantly offshore and southwest alongshore winds in winter and spring, 1985. Correlations of recruitment to northwest Atlantic cod (Gadus morhua) stocks with wind and North Atlantic atmospheric pressure anomalies (Koslow et al. 1987) may be based upon the wind's influence on nutrient availability and plankton abundance.

Influence of climatic changes on the parasites of Atlantic cod Gadus morhua off coastal Labrador, Canada

2006 ◽  
Vol 80 (2) ◽  
pp. 193-197 ◽  
Author(s):  
R.A. Khan ◽  
C.V. Chandra
Keyword(s):  
North Atlantic ◽  
Gadus Morhua ◽  
Atlantic Cod ◽  
Age Groups ◽  
Climatic Conditions ◽  
Otter Trawl ◽  
Commercial Fishery ◽  
Metazoan Parasites ◽  
Mean Values ◽  
The North

AbstractA study was conducted in 2000 and 2003, following the collapse of the commercial fishery in 1990, to compare metazoan parasites of Atlantic cod Gadus morhua, captured off coastal Labrador, with samples taken in 1980 and 1986. Fish were captured by otter trawl offshore in the North Atlantic Fish Organisation subarea 2J. Parasites were removed from the digestive tract, stained, identified and compared between the different groups. Both the prevalence and mean abundance of trematodes, larval nematodes and E. gadi were significantly lower in fish taken in 2000 and 2003 than in 1980. While mean values of trematodes and nematodes declined in 1986, those of Echinorhynchus gadi remained unchanged in 1986 and 1990. Four-year-old cod sampled in 1990 harboured significantly fewer E. gadi than older age groups. The most commonly occurring trematodes included Podocotylereflexa, Lepidapedon elongatum, Derogenes varicus and Hemiurus levinseni while the larval nematode, Anisakis sp. was predominant. Comparison of offshore samples taken in 2000 and 2003 with others taken in previous years suggests an overall decline of parasites coincident with a change in climatic conditions, the absence of a major food source, namely capelin Mallotus villosus, of cod and ultimately the decline of the Labrador population.

Temperature and the recruitment of Atlantic cod (Gadus morhua)

1999 ◽  
Vol 56 (11) ◽  
pp. 2069-2077 ◽  
Author(s):  
B Planque ◽  
T Frédou
Keyword(s):  
North Atlantic ◽  
Gadus Morhua ◽  
Cold Water ◽  
Atlantic Cod ◽  
The Other ◽  
Warm Water ◽  
The North ◽  
The North Atlantic ◽  
Interannual Fluctuations ◽  
The Relationship

Variability in the recruitment of fish has been attributed to either changes in the environment or variations in the size of reproductive stocks. Disentangling the effects of environment and stock has proven to be problematic and has resulted in recurrent controversy between studies supporting either hypothesis. In the present study, we examine the relationship between interannual changes in temperature and variation in recruitment for nine Atlantic cod (Gadus morhua) stocks in the North Atlantic. We show that for individual stocks, the relationship often appears weak and statistically not significant. On the other hand, by combining in a single metaanalysis the results from individual stocks, we demonstrate that recruitment of Atlantic cod is linked to interannual fluctuations in temperature in such a way that for stocks located in warm water the relationship is negative, for stocks located in cold water the relationship is positive, and there is no relationship for stocks located in the middle of the temperature range.

scholarly journals Recolonization history and large-scale dispersal in the open sea: the case study of the North Atlantic cod, Gadus morhua L.

2008 ◽  
Vol 94 (2) ◽  
pp. 315-329 ◽  
Author(s):  
CHRISTOPHE PAMPOULIE ◽  
MAGNÚS ÖRN STEFÁNSSON ◽  
THÓRA DÖGG JÖRUNDSDÓTTIR ◽  
BRET S. DANILOWICZ ◽  
ANNA KRISTÍN DANÍELSDÓTTIR
Keyword(s):  
North Atlantic ◽  
Large Scale ◽  
Gadus Morhua ◽  
Atlantic Cod ◽  
The North ◽  
Open Sea ◽  
The North Atlantic

Effect of the North Atlantic Oscillation on recruitment of Atlantic cod (Gadus morhua)

2004 ◽  
Vol 61 (9) ◽  
pp. 1558-1564 ◽  
Author(s):  
K Brander ◽  
R Mohn
Keyword(s):  
North Atlantic Oscillation ◽  
North Sea ◽  
North Atlantic ◽  
Gadus Morhua ◽  
Atlantic Cod ◽  
The North ◽  
Nao Index ◽  
The North Sea ◽  
The North Atlantic ◽  
The North Atlantic Oscillation

We examine the effect of introducing an environmental factor — the North Atlantic Oscillation (NAO) index — into a stock–recruit relationship fitted to 13 North Atlantic cod (Gadus morhua) stocks and discuss the implications for management. The NAO has a significant effect on recruitment of four of the stocks (positive effect on recruitment in the North Sea, Baltic Sea, and Irish Sea; negative effect on recruitment at Iceland), and the pattern of positive and negative effects on all stocks is consistent with the geographic influence of the NAO on environmental variables. Observed variability in the NAO should be taken into account in interpreting the causes of past changes in cod stocks. The NAO index for the previous winter is available by April and thus may provide an early indication of the likely range of cod recruitment in the current year. In areas, such as the North Sea, where the effect is strong, medium- and long-term assessments of recruitment and yield of the cod stocks should consider likely future states of the NAO. The NAO can be used to represent environmental variability in stock projections and thereby provide a better basis for the estimation of risk.

Spatial Comparison of Recent Growth in Postlarval Atlantic Cod (Gadus morhua) off Southwestern Nova Scotia: Inferior Growth in a Presumed Nursery Area

1989 ◽  
Vol 46 (S1) ◽  
pp. s113-s124 ◽  
Author(s):  
Iain M. Suthers ◽  
Kenneth T. Frank ◽  
Steven E. Campana
Keyword(s):  
Nova Scotia ◽  
Gadus Morhua ◽  
Atlantic Cod ◽  
Zooplankton Biomass ◽  
Early Summer ◽  
Sampling Area ◽  
Common Environment ◽  
Sea Temperature ◽  
Recent Growth ◽  
Otolith Increment

Spatial variation in distribution, age, and recent growth of postlarval cod (Gadus morhua) were examined off southwestern Nova Scotia during the early summer of 1985 and 1986. Ages ranged between 40–120 d posthatch throughout the sampling area, from the spawning grounds on Browns Bank, to nearshore (<55 m depth) and offshore regions 150 km north. The hatch-date distributions during 1986 between cruises 3 wk apart were significantly different in the nearshore, contrary to the age structure on the Bank which appeared more stable. These observations are consistent with retention of cod in the Browns Bank gyre, coupled with episodic leakage and northerly advection in the residual current. Recent growth determined from otolith increment widths was significantly less for those cod sampled at nearshore stations than for cod offshore and on the Bank. Recent growth was significantly correlated with Zooplankton biomass in a size range suitable for postlarval cod, while sea temperature was correlated in only one cruise. Nearshore areas had on average 25% of the Zooplankton biomass found on the Bank. Recent growth indices of the third and fourth week precapture were not significantly different between the nearshore and offshore, implying that the cod had shared a common environment, and common origin such as Browns Bank.

Metazoan parasites of cod, Gadus morhua L., in Canadian Atlantic waters

1982 ◽  
Vol 60 (7) ◽  
pp. 1573-1579 ◽  
Author(s):  
R. G. Appy ◽  
M. D. B. Burt
Keyword(s):  
North Atlantic ◽  
Gadus Morhua ◽  
Atlantic Cod ◽  
Parasite Fauna ◽  
Marine Fishes ◽  
Metazoan Parasites ◽  
The North ◽  
Wide Range ◽  
Enteric Parasites ◽  
The North Atlantic

From July to September 1975, 739+ Atlantic cod, Gadus morhua L., were collected in the Bay of Fundy, Nova Scotia shelf, and southern Gulf of St. Lawrence and were examined for metazoan paraties. Of 49 parasites recorded, 10 were considered more or less specific to cod or related gadid hosts, 9 were considered accidental infections, and the remaining majority of parasites were apparently capable of infecting a wide range of unrelated marine fishes. The general lack of strict host specificity of enteric parasites of northern marine fishes results in a very diverse parasite fauna in fish such as cod which have very broad feeding habits.Metazoan parasites recorded from cod were mostly arctic–boreal transatlantic and amphiboreal species. No species endemic to the northwestern Atlantic were found. However, among all metazoan parasites which are restricted to gadid hosts, there are more endemic species in the North Atlantic, particularly the northwestern Atlantic than present in the North Pacific. This distribution surely reflects the large number of endemic gadid genera and species in the North Atlantic and the probable Atlantic–Arctic origin of the Gadidae.

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