Abundance of juvenile Atlantic cod (Gadus morhua) in the shallow rocky subtidal and the relationship to winter seawater temperature

2004 ◽  
Vol 84 (2) ◽  
pp. 439-442 ◽  
Author(s):  
S.H. Magill ◽  
M.D.J. Sayer
Keyword(s):  
West Coast ◽  
Gadus Morhua ◽  
Atlantic Cod ◽  
Seawater Temperature ◽  
The West ◽  
Maximum Abundance ◽  
Rocky Subtidal ◽  
Juvenile Abundance ◽  
Winter Temperatures ◽  
The Relationship

Two inshore rocky subtidal sites on the west coast of Scotland (Saulmore Point, Firth of Lorn, 056°27′N 005°24′W and Davy's Rock, Firth of Clyde, 055°46′N 004°53′W) were surveyed for the presence of juvenile (0+) Atlantic cod, Gadus morhua between September 1995 and November 2001. A total of 951 juveniles were recorded at Saulmore Point and 34 at Davy's Rock. At Saulmore Point the abundance was highly seasonal, being observed between June and December only. Juveniles were present in only three out of six survey years, with a maximum abundance of 0·89 individuals m−2 recorded in 1996. Maximum abundance of juveniles at Saulmore Point was negatively correlated with winter seawater temperature, indicating that winter temperatures may be a useful indicator of subsequent juvenile abundance levels in inshore habitats.

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.

Rocky subtidal assemblages on the west coast of Ireland

Hydrobiologia ◽  
1986 ◽  
Vol 142 (1) ◽  
pp. 97-111
Author(s):  
John Costelloe ◽  
Brendan F. Keegan ◽  
Gerd F. Könnecker
Keyword(s):  
West Coast ◽  
The West ◽  
Rocky Subtidal

scholarly journals Local cod (Gadus morhua) revealed by egg surveys and population genetic analysis after longstanding depletion on the Swedish Skagerrak coast

2018 ◽  
Vol 76 (2) ◽  
pp. 418-429 ◽  
Author(s):  
Henrik Svedäng ◽  
Julia M I Barth ◽  
Anders Svenson ◽  
Patrik Jonsson ◽  
Sissel Jentoft ◽  
...  
Keyword(s):  
North Sea ◽  
West Coast ◽  
Population Genetic ◽  
Gadus Morhua ◽  
Atlantic Cod ◽  
Early Stage ◽  
Population Genetic Analysis ◽  
Swedish West Coast ◽  
The North ◽  
Spawning Areas

Abstract Dramatic and persistent reductions in Atlantic cod (Gadus morhua) are common in many coastal areas. While offshore cod stocks still were abundant and productive, the Swedish west coast showed signs of diminishing adult cod abundance at the beginning of the 1980s, where the local cod component was considered to be extirpated. To survey the present cod spawning activity and stock composition, we initiated egg trawling over two consecutive years (203 hauls in total) in combination with population genetic analyses (425 individually genotyped eggs). Here, we provide evidence of cod spawning at the Swedish Skagerrak coast, suggesting recolonization or that local cod has recovered from a nearly depleted state. Early stage eggs were found inside fjords too far to have been transported by oceanic drift from offshore spawning areas. The cod eggs were genetically similar in early to late life-stages and cluster mainly with the local adult cod, indicating that eggs and adults belong to the same genetic unit. The cod eggs were genetically differentiated from adult North Sea cod, and, to a lesser degree, also from the Kattegat and Öresund cod, i.e. indicating a possible recovery of local coastal stock. The patterns of the genetic structure in the inshore areas are, however, difficult to fully disentangle, as Atlantic cod in the North Sea-Skagerrak area seem to be a mixture of co-existing forms: local cod completing their entire life cycle in fjords and sheltered areas, and oceanic populations showing homing behaviours. The egg abundances are considerably lower compared with what is found in similar studies along the Norwegian Skagerrak coast. Nevertheless, the discovery of locally spawning cod along the Swedish west coast—although at low biomasses—is an encouraging finding that highlights the needs for endurance in protective measures and of detailed surveys to secure intraspecific biodiversity and ecosystem services.

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.

Time series bias in the estimation of density-dependent mortality in stock-recruitment models

1995 ◽  
Vol 52 (1) ◽  
pp. 223-232 ◽  
Author(s):  
Ransom A. Myers ◽  
N. J. Barrowman
Keyword(s):  
Time Series ◽  
Gadus Morhua ◽  
Large Time ◽  
Atlantic Cod ◽  
Model Misspecification ◽  
Parameter Estimates ◽  
Density Dependent Mortality ◽  
Stock Recruitment ◽  
Iteroparous Species ◽  
The Relationship

Large biases can occur in parameter estimates for stock–recruitment models because the stock sizes are not chosen independently, being correlated with variability in recruitment. We examine the importance of this "time series bias" by a comprehensive analysis of available stock–recruitment data and the use of simulations. For semelparous species, i.e., species that reproduce only once, time series bias is important for all populations for which we had data. For iteroparous species, i.e., species that reproduce more than once, large biases occur if the populations are exploited at close to the maximum that is biologically possible. Notably, when there is autocorrelation in natural mortality, for univoltine species, the direction of bias is reversed due to model misspecification. Given moderate sample sizes and moderate levels of exploitation, time series bias is small for species such as Atlantic cod (Gadus morhua), for which α, the slope of the relationship between recruitment and number of spawners as the number of spawners goes to zero, is large. Time series bias will usually be important in species such as hakes (Merluccius) for which α appears to be relatively small.

Improving the catch efficiency of the West Coast rock lobster, Jasus lalandii

2000 ◽  
Vol 51 (6) ◽  
pp. 613 ◽  
Author(s):  
D. Loewenthal ◽  
S. Mayfield ◽  
G. M. Branch
Keyword(s):  
Weight Loss ◽  
South African ◽  
West Coast ◽  
Capture Rate ◽  
Catch Rate ◽  
Rock Lobster ◽  
The South ◽  
The West ◽  
The Relationship

The South African commercial rock-lobster industry employs an average soak time of 22 h for traps. Experiments were undertaken to test (1) the rate of bait loss with soak time and the effect that protection of the bait has on bait loss, (2) the relationship between catch rate (numbers per trap) and soak time for traps with either protected or unprotected bait, and (3) the effect of two bait types (whole maasbanker and hake heads) on the catch of rock lobsters. There were substantial losses of unprotected bait within 6 h; substantially less weight loss was observed from protected bait even after a 48-h soak time. The numbers of rock lobsters caught in traps with unprotected bait were low relative to the capture rate with protected bait. The highest capture rate occurred after 6 h for unprotected bait and 6–12 h for protected bait. There was no significant effect of bait type (maasbanker v. hake heads) on the number or size of rock lobsters. To optimize catch efficiency, the commercial industry should use protected bait and soak times as short as 6–12 h.

Rocky subtidal assemblages on the west coast of Ireland

1987 ◽  
pp. 97-111
Author(s):  
John Costelloe ◽  
Brendan F. Keegan ◽  
Gerd F. Könnecker
Keyword(s):  
West Coast ◽  
The West ◽  
Rocky Subtidal

Théophilus Conneau: The Saga of a Tale

1979 ◽  
Vol 6 ◽  
pp. 97-107 ◽  
Author(s):  
Bruce L. Mouser
Keyword(s):  
United States ◽  
Latin America ◽  
Motion Picture ◽  
West Coast ◽  
Life Story ◽  
The United States ◽  
The West ◽  
The Subject ◽  
The Relationship

Rare has been the book on Africa that has acquired a history and become the subject of study in its own right. One such is the autobiography of Théophilus Conneau, a slave dealer of French and Italian background, who lived on the west coast of Africa during the 1830s and 1840s. Various accounts of Conneau's experiences in Guinea and Liberia have been translated into four languages, and were even incorporated into a successful novel in 1933, on which was based a motion picture. The latest version of Conneau's life story (and the occasion for this paper) was published as recently as 1976.Conneau's story first came to press in 1854 through the editorial assistance and skill of Brantz Mayer, a lecturer, author, and journalist of the Baltimore area, known principally for his writings about Latin America. Having obtained experience and contacts with publishers by editing manuscripts and letters, Mayer was a valuable asset to a new author in 1853. Recently discovered letters from Conneau to Mayer and Mayer's own account of the relationship between them suggest an interesting beginning for this literary enterprise. Conneau found himself in 1853 in Baltimore where he met James Hall, whom he had known previously in Liberia. Hall had been an enthusiastic supporter of the Maryland settlement for freed Blacks at Cape Palmas and had served as that settlement's first governor from 1833 to 1836. Concluding that Conneau's story of a repentant slave trader would be of value to the cause of anti-slavery and black emigration from the United States to Africa, Hall suggested that Conneau write his memoirs and introduced him to Mayer.

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