scholarly journals Feeding by grey seals on endangered stocks of Atlantic cod and white hake

2014 ◽  
Vol 71 (6) ◽  
pp. 1332-1341 ◽  
Author(s):  
M.O. Hammill ◽  
G.B. Stenson ◽  
D.P. Swain ◽  
H.P. Benoît
Keyword(s):  
High Mortality ◽  
West Coast ◽  
Atlantic Cod ◽  
Stomach Contents ◽  
Natural Mortality ◽  
The West ◽  
Cape Breton Island ◽  
Cape Breton ◽  
The Mean ◽  
Overwintering Area

High natural mortality is preventing the recovery of collapsed stocks of Atlantic cod and white hake in the southern Gulf of St Lawrence, Canada. Predation by grey seals has been proposed as an important cause of this high mortality. We determined the contribution of cod and hake to the diet of grey seals collected along the west coast of Cape Breton Island and in the Cabot Strait, an area where overwintering cod aggregate. Along the coast of Cape Breton Island, the contribution of hake and cod to the diet was 30 and 17%, respectively, by weight using stomach contents and 13 and 9%, respectively, based on intestine contents. In the Cabot Strait, when overwintering aggregations of cod were present, cod accounted for 68% (range 57–80%) of the male diet from stomachs, and 46% (range: 31–64%) of the diet determined from intestines. Among females, cod represented 14% (range: 0–34%) and 9% (range: 3–54%) of the diet from stomachs and intestines, respectively. In Cabot Strait, white hake accounted for up to 17% of the diet by weight from stomachs, and up to 6% of the diet determined from intestines. The mean length of cod consumed by seals was 28 cm (SD = 8.6) along the coast of Cape Breton Island, and 39 cm (SD = 5.7) in Cabot Strait. The mean length of hake consumed by seals was 29 cm (SD = 7.0) along the coast of Cape Breton Island, and 35 cm (SD = 5.6) in Cabot Strait. Cod and hake are more important to the diet of males than that of females. The contribution of cod to the diet of grey seals foraging in the cod overwintering area is much greater than has been reported elsewhere.

scholarly journals A review of factors limiting recovery of Pacific herring stocks in Canada

2010 ◽  
Vol 67 (9) ◽  
pp. 1903-1913 ◽  
Author(s):  
Jacob F. Schweigert ◽  
Jennifer L. Boldt ◽  
Linnea Flostrand ◽  
Jaclyn S. Cleary
Keyword(s):  
West Coast ◽  
Positive Relationship ◽  
Pacific Herring ◽  
Zooplankton Abundance ◽  
Natural Mortality ◽  
Population Recovery ◽  
The West ◽  
Clupea Pallasi ◽  
Adequate Food ◽  
Forage Species

AbstractSchweigert, J. F., Boldt, J. L., Flostrand, L., and Cleary, J. S. 2010. A review of factors limiting recovery of Pacific herring stocks in Canada. – ICES Journal of Marine Science, 67: 1903–1913. On the west coast of Canada, Pacific herring (Clupea pallasi) supported an intensive reduction fishery from the early 1930s until the collapse of all five major stocks in the late 1960s, which then recovered rapidly following a fishery closure. Despite conservative harvests, abundance has declined again recently, with little evidence of recovery. We investigated the effect of bottom-up forcing by zooplankton abundance, top-down forcing by fish and mammal predators, and the effects of sardine abundance as potential competitors on the natural mortality of the herring stock on the west coast of Vancouver Island. Herring mortality was positively related to Thysanoessa spinifera and southern chaetognaths and negatively to pteropod abundance. Estimated predation on herring decreased significantly during the years 1973–2008, with the main consumers changing from fish to mammals. However, the correlation with herring mortality was negative, whereas there was a significant positive relationship with sardine abundance. Population recovery is expected to be facilitated by a combination of factors, including adequate food supply, limited or reduced predation (including fishing), and limited competition particularly for wasp–waist systems, where different forage species may occupy similar niches.

Relative abundances and size compositions of champagne crabs, Hypothalassia acerba, on two coasts and in different water depths and seasons

2004 ◽  
Vol 55 (7) ◽  
pp. 653 ◽  
Author(s):  
Kim D. Smith ◽  
Norman G. Hall ◽  
Ian C. Potter
Keyword(s):  
West Coast ◽  
Carapace Length ◽  
South Coast ◽  
The South ◽  
The West ◽  
Spatial Partitioning ◽  
Invertebrate Predators ◽  
The Mean ◽  
The Difference ◽  
Catch Rates

Hypothalassia acerba was sampled seasonally using traps at depths of 35, 90, 145, 200, 255, 310 and 365 m on the west and south coasts of Western Australia. Catch rates peaked at depths of 200 m on the west coast and 145 m on the south coast but at similar temperatures of 16.1–17.1°C. The west and south coast catches contained 69% and 84% males respectively. The carapace length of H. acerba declined significantly by 4 mm for each 100 m increase in depth. The maximum carapace length of males was greater than females on the west coast (135 v. 113 mm) and south coast (138 v. 120 mm). Furthermore, after adjustment to a depth of 200 m, the mean carapace lengths of males were greater than females on both the west coast (96.6 v. 94.6 mm) and south coast (101.5 v. 91.4 mm), with the difference on the south coast being significant (P < 0.001). Thus, in summary, (1) distribution was related to depth and temperature; (2) body size was inversely related to water depth; and (3) males grew larger and were caught in greater numbers than females. There was also evidence that the distribution changed slightly with season and of spatial partitioning by H. acerba and other large deep-water invertebrate predators.

Infection of Lumpfish (Cyclopterus lumpus) with Larvae and of Atlantic cod (Gadus morhua) with Adults of the Copepod, Lernaeocera branchialis, in and adjacent to the Newfoundland area, and Inferences Therefrom on Inshore–Offshore Migrations of Cod

1976 ◽  
Vol 33 (4) ◽  
pp. 711-731 ◽  
Author(s):  
Wilfred Templeman ◽  
V. M. Hodder ◽  
A. M. Fleming
Keyword(s):  
Intermediate Host ◽  
West Coast ◽  
Gadus Morhua ◽  
East Coast ◽  
Atlantic Cod ◽  
Adult Parasite ◽  
Infection Rates ◽  
The West ◽  
Cyclopterus Lumpus ◽  
Branchial Arches

The lumpfish, Cyclopterus lumpus, was found to be a common intermediate host of the larvae of the copepod, Lernaeocera branchialis, in the Newfoundland and neighboring areas. Large numbers of these larvae occurred on the gills of lumpfish from inshore Newfoundland areas from the latter half of June to the first half of August, whereas only minor infection was found in any month in offshore areas. Some larvae of the year reached the final or seventh stage on the intermediate host in May on the west coast of Newfoundland and in June on the east coast. By July on the west coast and early August on the east coast, this was by far the most numerous stage present. The larvae were attached mainly near the tips of the gill filaments. Most larvae were attached to the gills of the first two branchial arches, less to those of the third, and much less to those of the fourth. There were more larvae on the right than on the left gills. Infection of the final host Atlantic cod (Gadus morhua), by stage-7 female L. branchialis was apparently mainly inshore.Adult L. branchialis on Atlantic cod, typically located near the anterior ventral apex of the branchial arches, were numerous throughout the year in the areas of high infection. Infection rates of cod with the adult parasite were usually considerably higher near the coast than farther offshore, the rates declining with distance from the coast. Rates of infection with the adult parasite usually increased from the smaller to intermediate cod lengths and declined rapidly at greater lengths. Infection rates were found useful as evidence of inshore and offshore migrations of cod. Infection with the copepod apparently delayed sexual maturity in cod. Most infected cod (86%) had one adult copepod and declining numbers (12–0.05%) possessed two to five adult copepods. The Greenland cod, G. ogac, was the only other fish of the area found to be highly infected with adult L. branchialis.

Effects of Oceanic Variations and the West Greenland Fishery on Age at Maturity of Icelandic West Coast Stocks of Atlantic Salmon (Salmo salar)

1989 ◽  
Vol 46 (1) ◽  
pp. 16-27 ◽  
Author(s):  
Dennis L. Scarnecchia ◽  
Árni Ísaksson ◽  
S. E. White
Keyword(s):  
Time Series ◽  
Atlantic Salmon ◽  
Salmo Salar ◽  
West Coast ◽  
Strongly Correlated ◽  
The West ◽  
West Greenland ◽  
Atlantic Salmon Salmo Salar ◽  
The Mean ◽  
Salmon Fishery

Investigations were conducted on the effects of oceanic variations (as measured by sea temperatures) and catches by the West Greenland salmon fishery on the sea age composition of Atlantic salmon (Salmo salar) stocks from 21 Icelandic west coast rivers. Annual ratios of grilse to two-sea-winter (2SW) salmon were strongly correlated among the 21 rivers. All eight rivers with time series extending back before the expansion of the West Greenland fishery showed lower ratios during the earlier period. Only 2 of the 21 rivers, however, had significantly declining ratios over their time series. In addition, for only one river was West Greenland catch significantly related to the ratios (P < 0.05), and for only one river did ratios increase when the expanded West Greenland fishery was active. Overall, the effects of the fishery on stock composition are evidently minimal. The mean April–May temperature when the smolts were to migrate out of rivers was significantly and positively related to subsequent ratios for five of the rivers, which, along with correlations among the ratios, indicated that more rapid growth of smolts in their first summer may have increased the ratios of grilse to 2SW salmon on several rivers.

Hooded Seal (Cystophora cristata) Pup Production in the Gulf of St. Lawrence

1992 ◽  
Vol 49 (12) ◽  
pp. 2546-2550 ◽  
Author(s):  
M. O. Hammill ◽  
G. B. Stenson ◽  
R. A. Myers
Keyword(s):  
Prince Edward Island ◽  
The West ◽  
Hooded Seal ◽  
Cape Breton Island ◽  
Small Patch ◽  
Cape Breton ◽  
Cystophora Cristata ◽  
Aerial Surveys ◽  
Production Estimate ◽  
Magdalen Islands

Systematic visual aerial surveys were flown in the southern Gulf of St. Lawrence during March 1990 and 1991 to estimate hooded seal (Cystophora cristata) pup production. In 1990, the main whelping patch, occupying an area of 264 km2, was located near Cape Breton Island. One hundred and five pups were counted on 17 transects, resulting in a mean density of 1.74 pups∙kim−2 and an estimated pup production of 1638 (SE = 466). In 1991, a large whelping patch was located to the west of the Magdalen Islands, a second off the coast of Prince Edward Island, and a small patch was later found south of the Magdalen Islands. The two major patches were surveyed, resulting in a pup production estimate of 1564 (SE = 101). During the 1991 surveys, an estimated 71–93% of the pups were on the ice. Correcting for the distribution of births results in a minimum 1991 pup production estimate of 2006 (SE = 190) for the Gulf of St. Lawrence.

2. On the Temperature of the Sea around the Coasts of Scotland during the years 1857 and 1858; and the bearing of the facts on the Gulf-stream Theory

1862 ◽  
Vol 4 ◽  
pp. 154-156
Author(s):  
James Stark
Keyword(s):  
West Coast ◽  
Gulf Stream ◽  
The West ◽  
Mean Temperature ◽  
The Mean

By a reference to observations made on the temperature of the air, of the sea, and the solid land, the author showed that the mean temperature of each of these in and around Scotland were within the fraction of a degree of each other. From observations made on the temperature of the air and of the sea at stations on the west coast, he showed that not only did the air and sea attain their respective minima and maxima at the same time, but that even in their fluctuations of temperature they bore a distinct accord with each other. He then pointed out that such fluctuations in the temperature of the sea were quite fatal to the theory of the mild winters of Britain being dependent on the influence of the Gulf-stream, as such fluctuations could not occur were the temperature of the sea dependent on the heated waters of the Gulf-stream.

The Mean Pressure of the Atmosphere, and the Prevailing Winds for the Months and for the Year. Part II

1869 ◽  
Vol 6 ◽  
pp. 523-524
Author(s):  
Alexander Buchan
Keyword(s):  
New Zealand ◽  
North America ◽  
South America ◽  
West Coast ◽  
The West ◽  
Additional Information ◽  
Mean Pressure ◽  
The Mean

In Part I., read 16th March 1868, in which was discussed the Mean Pressure of the Atmosphere over the Globe for July, January, and the year, the method by which the Isobaric Charts were constructed was detailed at length. Since March 1868, valuable additional information has been obtained from Australia, New Zealand, Tasmania, Africa, South America, the west coast of North America, Iceland, and from a few isolated stations in Europe and Asia. The period for the British Islands has been extended so as to include the eleven years from 1857 to 1867.

Submersible observations on the daytime vertical distribution of Aequorea ?forskalea off the west coast of southern Africa

2005 ◽  
Vol 85 (3) ◽  
pp. 519-522 ◽  
Author(s):  
Conrad Sparks ◽  
Andrew S. Brierley ◽  
Emmanuelle Buecher ◽  
Dave Boyer ◽  
Bjøern Axelsen ◽  
...  
Keyword(s):  
Vertical Distribution ◽  
Surface Temperature ◽  
Sea Surface Temperature ◽  
Southern Africa ◽  
West Coast ◽  
Sea Surface ◽  
The West ◽  
Spatial Overlap ◽  
The Mean ◽  
The Vertical Distribution

The vertical distribution of the hydromedusa Aequorea ?forskalea was investigated using observations from the research submersible ‘Jago’ collected during 36 dives off the west coast of southern Africa during November 1997 and April 1999. The mean population depth of Aequorea ?forskalea deepened with increasing sea surface temperature. We suggest that this behaviour enables individuals to avoid offshore advection, to minimize spatial overlap with other large medusae and to maintain their position over the middle of the shelf.

2. On the Mean Monthly Rainfall of Scotland

1872 ◽  
Vol 7 ◽  
pp. 665-666
Author(s):  
Alexander Buchan
Keyword(s):  
West Coast ◽  
East Coast ◽  
Monthly Rainfall ◽  
The South ◽  
The West ◽  
South West ◽  
Westerly Winds ◽  
South Shore ◽  
The Mean ◽  
Firth Of Forth

So far as regards the annual amounts of the rainfall of Scotland, deduced from observations made at 296 different places, the chief point brought out is the enormous difference between the rainfall of the west and that of the east; the stations along the west coast showing such figures as 40, 45, and 54 inches, as compared with 24, 27, and 30 inches at stations on the east coast, not situated in the immediate neighbourhood of hills. When it is considered that the source of the rainfall is the prevailing south-westerly winds, it is evident that the comparative dryness of such districts as the south shore of the Firth of Forth is due to high land lying to the south-west, which drains the winds of a large portion of their moisture in their passage across them.

scholarly journals Abstract of Paper on the Frost of 1895 in Scotland

1902 ◽  
Vol 42 ◽  
pp. 532-534
Author(s):  
R. C. Mossman
Keyword(s):  
West Coast ◽  
The South ◽  
The West ◽  
North East ◽  
The North ◽  
Mean Temperature ◽  
The Mean

This great frost commenced on 28th December 1894 and terminated in its intense form on 20th February 1895, thus lasting 54 days. The greatest cold occurred from the 6th to the 20th of February. During this latter period pressure was higher in the north than in the south of Scotland, and the winds were consequently easterly or north-easterly, but light in force. Taking the two months, January and February, together, the mean temperature was more than 10° below the average at many inland places, but on the west coast it was only about 5° lower than usual. There are records of temperature in the north-east of Scotland, at either Inverness, Gordon Castle or Aberdeen for the last 132 years, and in all this time there was no winter with two such cold months as January and February 1895 at these places.

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