Life History and Ecology of American Plaice (Hippoglossoides platessoides F.) in the Magdalen Shallows

1965 ◽  
Vol 22 (2) ◽  
pp. 565-598 ◽  
Author(s):  
P. M. Powles
Keyword(s):  
Sexual Maturity ◽  
Atlantic Cod ◽  
General Distribution ◽  
Commercial Fishing ◽  
Bottom Temperature ◽  
Cape Breton ◽  
Inshore Waters ◽  
Food Competitor ◽  
Marketable Size ◽  
Hippoglossoides Platessoides

Males reach marketable size (32 cm) at age 10, and females at age 8. Sexual maturity is attained at 25 cm (age 6) for males and 41 cm (age 10) for females, and maximum spawning occurs annually from mid April to mid May. Commercial fishing has reduced the number of year-classes in the fishery from about 26 in 1957 to 17 in 1961, but has not affected the rate of growth.The main summer fishery occurs in the Chaleur Bay, Shippegan Gully, and North Bay regions in depths of 40–100 m. In winter, American plaice were most abundant in depths of 180–460 m (bottom temperature 3–6 °C), although a few immatures remained in the cold inshore waters. In spring (April), plaice were taken mostly from 75 to 150 m depths (−1.0 to 5.0 °C).Adult plaice feed mainly on molluscs and echinoderms, and young plaice on polychaetes and small Crustacea. Feeding ceases almost completely during January–March. The main food competitor of plaice in the Magdalen Shallows is the Atlantic cod, which has the same general distribution during the summer. Atlantic cod, particularly those over 78 cm long, are also the main predators of small plaice, but mortality due to cod grazing has decreased in recent years because of declining numbers of large cod.Tagging and meristic studies indicate that Magdalen Shallows plaice are a discrete stock made up of two main groups. The groups are maintained by the tendency of plaice (excluding very old individuals) to return to the same areas each summer. The northern or "Miscou–Magdalen" group includes fish of Chaleur Bay, Shippegan Gully, and Orphan Bank regions. The southern or "Cape Breton" group occurs from George Bay to St. Paul Island.

Sexual Maturity and Spawning of the American Plaice, Hippoglossoides platessoides (Fabricius), from Newfoundland and Grand Bank Areas

1966 ◽  
Vol 23 (5) ◽  
pp. 651-672 ◽  
Author(s):  
T. K. Pitt
Keyword(s):  
Deep Water ◽  
Sexual Maturity ◽  
Bottom Temperature ◽  
Spawning Period ◽  
The North ◽  
Spawning Areas ◽  
Northern Half ◽  
Surrounding Areas ◽  
Hippoglossoides Platessoides

The peak spawning period of American plaice was the first part of April for Flemish Cap and ranged from the end of April for the Grand Bank and surrounding areas to the first part of June for Labrador–Northeast Newfoundland Shelf. Average bottom temperatures during spawning ranged from about 3.5 C for Flemish Cap and the deep spawning areas to the north, to about −1.3 C for St. Mary's Bay and the northern half of the Grand Bank. For the Southeast Grand Bank, Southwest Grand Bank, and St. Pierre Bank average spawning temperatures were 1.1, 2.8, and 2.7 C, respectively.There was evidence that some older, larger fish spawned first and also that plaice in deep water spawned later than those from shallower depths. At the latter depths light was a possible factor.According to samples from St. Mary's Bay the development of the sex products for spring spawning was apparently controlled by water temperatures during the previous fall and late summer.Fifty per cent of the females from Flemish Cap were mature at 7.8 years, the bottom temperature being almost constant at 3.5 C. For other areas the number of years ranged from 12.2 for the Southwest Grand Bank, with prevalent temperatures 0–3, to 15.2 C for St. Mary's Bay where temperatures were −1 to 1.0 C. For males the range was from 5.3 years for the Southeast Grand Bank to 7.5 years for St. Pierre Bank, no data being available for Flemish Cap.

Chapter 3 Effects of Climate Change and Commercial Fishing on Atlantic Cod Gadus morhua

2009 ◽  
pp. 213-273 ◽  
Author(s):  
Nova Mieszkowska ◽  
Martin J. Genner ◽  
Stephen J. Hawkins ◽  
David W. Sims
Keyword(s):  
Climate Change ◽  
Gadus Morhua ◽  
Atlantic Cod ◽  
Commercial Fishing

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.

Experiments with the Harbour Seal, Phoca vitulina, a Definitive Host of a Marine Nematode, Porrocaecum decipiens

1953 ◽  
Vol 10 (8) ◽  
pp. 539-547 ◽  
Author(s):  
D. M. Scott
Keyword(s):  
Definitive Host ◽  
Atlantic Cod ◽  
Phoca Vitulina ◽  
Harbour Seal ◽  
Osmerus Mordax ◽  
Marine Nematode ◽  
The Third ◽  
Males And Females ◽  
Distinct Increase ◽  
Hippoglossoides Platessoides

Infestation experiments carried out in 1947 and 1948 showed that the harbour seal (Phoca vitulina) was a definitive host of a larval nematode found in the flesh of the Atlantic cod (Gadus callarias), smelt (Osmerus mordax), Canadian plaice (Hippoglossoides platessoides) and eelpout (Macrozoarces americanus). Adult worms recovered from experimentally infested seals were identified as Porrocaecum decipiens. Some larval Porrocaecum in the four species of fishes studied were P. decipiens.The worms lost their larval characteristics by moulting between the third and sixth day following introduction into the seal. Sexual maturation proceeded rapidly after the eleventh day and some males and females matured before the twentieth day. Maturation was accompanied by a distinct increase in size.

COD MOVEMENTS ON THE CANADIAN ATLANTIC COAST

1933 ◽  
Vol 8 (1) ◽  
pp. 433-458 ◽  
Author(s):  
R. A. McKENZIE
Keyword(s):  
Nova Scotia ◽  
Prince Edward Island ◽  
Cold Water ◽  
Atlantic Coast ◽  
Summer Season ◽  
Warm Water ◽  
Early Winter ◽  
Cape Breton ◽  
Inshore Waters ◽  
Glace Bay

From 1925 to 1933 inclusive, during the summer season, 8,774 cod were tagged at eight points along the coasts of Nova Scotia and Prince Edward Island and eight per cent were recaptured during the following years, none after the sixth.Cod performing a restricted migration (less than 40 kilometres) were found to be in the majority off Halifax from July to September and off Shelburne in June and August in certain areas.Near Seal island in June, off Shelburne in July and September, and off Glace Bay in July and August, the majority of the cod were found to show orderly extended migrations. In the first two instances this movement was shoreward in the summer and seaward to about 130 metres in the early winter. The Glace Bay cod moved from the offshore banks just west of the Laurentian channel to the Cape Breton vicinity in the summer, returning early in the winter.A small percentage of the various stocks of cod performed roving migrations.The complete forsaking of the Cape Breton district for the offshore banks in the winter is attributed to the unfavourable ice cold water, while south-westward of Canso the movement off shore is thought to be caused by the very warm water inshore in the autumn and continued through the influence of the cold inshore waters several months later.As they grow older, the Shelburne cod remain progressively a little farther off shore when they move to shoal water each summer.

Seasonal variation in the habitat associations of Atlantic cod (Gadus morhua) and American plaice (Hippoglossoides platessoides) from the southern Gulf of St. Lawrence

1998 ◽  
Vol 55 (12) ◽  
pp. 2548-2561 ◽  
Author(s):  
D P Swain ◽  
G A Chouinard ◽  
R Morin ◽  
K F Drinkwater
Keyword(s):  
Seasonal Variation ◽  
Habitat Selection ◽  
Gadus Morhua ◽  
Atlantic Cod ◽  
Statistical Significance ◽  
Habitat Associations ◽  
Practical Implications ◽  
Hippoglossoides Platessoides ◽  
Trawl Surveys ◽  
Selection Of

We compared habitat associations of southern Gulf of St. Lawrence Atlantic cod (Gadus morhua) and American plaice (Hippoglossoides platessoides) between the summer feeding season on the Magdalen Shallows and the overwintering period in the Cabot Strait. Data were from bottom trawl surveys conducted in September 1993, 1994, and 1995 and January 1994, 1995, and 1996. Both species occupied much deeper, warmer water in winter than in summer. The effect of cod age on temperature distribution reversed between the two seasons, with younger cod occupying warmer water than older cod in summer and colder water in winter. Selection of both depth and temperature by cod tended to be more significant in September than in January. The reduced statistical significance of habitat selection by cod in winter was associated with a more aggregated distribution in this season. The contrast between seasons in habitat associations was particularly strong for plaice. The median habitats occupied by plaice were 58-67 m and -0.1 to 0.3°C in September and 374-426 m and 5.2-5.4°C in January. Habitat selection by plaice was significant in both seasons, but significance tended to be greater in January. Degree of aggregation in plaice distribution was similar between the two seasons. Female plaice occupied significantly warmer water than males in September but not in January. The ecological and practical implications of this striking seasonal variation in habitat associations are discussed.

Protein Instability in Minced Flesh from Fillets and Frames of Several Commercial Atlantic Fishes During Storage at −5 C

1975 ◽  
Vol 32 (6) ◽  
pp. 775-783 ◽  
Author(s):  
J. R. Dingle ◽  
J. A. Hines
Keyword(s):  
Gadus Morhua ◽  
Atlantic Cod ◽  
Protein Solubility ◽  
Kidney Tissue ◽  
Rapid Loss ◽  
Atlantic Mackerel ◽  
Trimethylamine Oxide ◽  
Minced Fish ◽  
Protein Instability ◽  
Hippoglossoides Platessoides

Minced flesh of Atlantic cod (Gadus morhua) and pollock (Pollachius virens), recovered by means of meat-separator machines from frames left after filleting operations, suffered a rapid loss of protein solubility during storage at −5 C. This was due to the presence of kidney tissue which caused the formation of dimethylamine and formaldehyde from the trimethylamine oxide of the muscle. The minced flesh of witch flounder (Glyptocephalus cynoglossus), American plaice (Hippoglossoides platessoides), and Atlantic mackerel (Scomber scombrus) was relatively stable when mixed with homogenates of their own kidney tissue, but cod kidney caused the same changes in gray sole as it did in minced cod flesh. The exclusion of gadoid kidney and blood from minced fish preparations is recommended.

Overwintering of Adult Northern Atlantic Cod (Gadus morhua) in Cold Inshore Waters as Evidenced by Plasma Antifreeze Glycoprotein Levels

1994 ◽  
Vol 51 (12) ◽  
pp. 2834-2842 ◽  
Author(s):  
Sally V. Goddard ◽  
J. S. Wroblewski ◽  
C. T. Taggart ◽  
K. A. Howse ◽  
W. L. Bailey ◽  
...  
Keyword(s):  
Gadus Morhua ◽  
Atlantic Cod ◽  
Antifreeze Glycoproteins ◽  
Cold Temperatures ◽  
Antifreeze Glycoprotein ◽  
Trap Fishery ◽  
In The Wild ◽  
History Of ◽  
Inshore Waters ◽  
Trinity Bay

Adult Atlantic cod (Gadus morhua) are known to produce antifreeze glycoproteins in response to cold temperatures. Our laboratory studies demonstrated that blood plasma levels in adult cod were positively correlated with the number of days they spent in subzero water. Between April 1991 and June 1993, we monitored concentrations of antifreeze glycoproteins in the plasma of late juvenile and adult cod in Trinity Bay, Newfoundland, and used the results to estimate how long cod had been exposed to low water temperatures. A consideration of these data in conjunction with detailed temperature profiles of the area taken over the course of the study allowed us to deduce the distribution of cod in relation to the temperature field. This study provides evidence that (1) blood antifreeze glycoprotein levels can be used to deduce the recent thermal history of cod in the wild and (2) after their inshore summer feeding period, considerable numbers of adult cod overwintered inshore in Trinity Bay in subzero water, producing antifreeze glycoproteins as temperatures fell below 0 °C. From May onwards, "cold-adapted" cod moved into warming surface waters, where they became available to an early inshore trap fishery.

Dynamics of the Recovery of the Western Lake Erie Walleye (Stizostedion vitreum vitreum) Stock

1987 ◽  
Vol 44 (S2) ◽  
pp. s15-s22 ◽  
Author(s):  
Richard W. Hatch ◽  
Stephen J. Nepszy ◽  
Kenneth M. Muth ◽  
Carl T. Baker
Keyword(s):  
Sexual Maturity ◽  
Lake Erie ◽  
Standing Stock ◽  
Management Plan ◽  
Commercial Fishing ◽  
Stizostedion Vitreum ◽  
Central Basin ◽  
Western Lake ◽  
Quota Management ◽  
Western Lake Erie

After its 1957 collapse under intensive fishing and environmental stresses, the walleye (Stizostedion vitreum vitreum) stock of western Lake Erie remained low throughout the 1960s. A moratorium on both sport and commercial fishing, resulting from the 1970 discovery of mercury concentrations in walleye flesh, provided an opportunity for the development of an international interagency management plan. The quota management plan developed depended on sequential projection of the fishable stock on the basis of estimated annual recruitment and reports of total withdrawals from the stock. The fishery reopened gradually and quota management (including allocation among jurisdictions) was implemented in 1976. The stock, which had been gradually increasing as a result of relatively strong year-classes produced in 1970, 1972, and 1974, responded well to limited exploitation and produced a record year-class in 1977. Quotas were exceeded in 1978–80, but the stock continued to improve to the extent that the recommended rate of exploitation was increased in 1980 and again in 1981. As the population expanded, growth began to decline; the decline became apparent in young-of-the-year in the early 1970s and in older walleyes in the late 1970s. This trend toward progressively slower growth, which continued in the 1977 and subsequent year-classes, was accompanied by an increase in length at sexual maturity and a decrease in the percentage of female walleyes reaching sexual maturity at age III. As a net result of these changes, the proportion of mature females in the stock (an index of stock fecundity) decreased slightly during the interval 1975–84, while the estimated biomass of the standing stock rose from 9 000 to nearly 26 000 t. Both sport and commercial catches increased markedly after 1980 in Lake Erie's central basin.

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