posted on November 01, 1981 00:22
J. L. Paton Chair of Marine Biology and Fisheries
Memorial University of Newfoundland
St. John's, Newfoundland, Canada
Source - Journal of Northwest Atlantic Fishery Science, Volume 2: 21-45
A total of 416 cod vertebral samples collected from the Newfoundland and adjacent areas during 1947-71, are analyzed in relation to their use for delineating the cod stocks of the region. Differences greater than two vertebrae were found between the highest and lowest vertebral means for different stocks. The overall vertebral mean for females exceeded that for males by 0.10.
The main portion of the Labrador-East Newfoundland stock (Div. 2G to 3K) was well separated from the southern Grand Bank stock (Div. 3N and 3O) by the presence in the northern area of high vertebral means and of higher percentages of high vertebral numbers and the lack of low vertebral numbers. This contrasted with vertebral means about one to two vertebrae lower in the southern Grand Bank stock, with higher percentages of low vertebral numbers and a lack of high vertebral numbers. Cod from the offshore area in Div. 2G to 3K had somewhat higher vertebral numbers than those of the inshore area. The high vertebral-count cod of the Labrador-East Newfoundland stock also extended to the northern slopes of Grand Bank and around the Avalon Peninsula (Div. 3L), but in this area they usually intermingled with cod of the Avalon stock complex and with some migrants from southern Grand Bank as indicated by vertebral means intermediate between the northern and southern extremes. In the Labrador-East Newfoundland stock, vertebral means were slightly lower in 1961-71 than in 1947-60. Vertebral means for cod off West Greenland were considerably lower than those for Labrador cod and similar to those for the southern Grand Bank stock. On St. Pierre Bank (Subdiv. 3Ps), some samples had as low vertebral means as those on Grand Bank whereas other samples had intermediate vertebral means similar to those in the adjacent coastal area. The northern Gulf and southern Gulf stocks, north and south of the Laurentian Channel in the Gulf of St. Lawrence (Div. 4RST), had low vertebral means, except for evidence of the intrusion of some cod with high vertebral numbers in and near the Strait of Belle Isle. Vertebral means declined from north to south on the Scotian Shelf (Div. 4VWX) and to Georges Bank (Div. 5Z).
Spawning times of cod in various parts of the Northwest Atlantic are reviewed, and vertebral numbers for the different areas and stocks are related to the surface temperatures and current drifts following spawning. The lowest surface temperatures during egg and early larval development were associated with the longest period of egg and larval drift, the highest vertebral means, and the largest, most-widely distributed stock.
Language - English
Publisher - Northwest Atlantic Fisheries Organization (NAFO), Dartmouth, N.S., Canada
Publication Date - October 1981
Publication Type - Journal Article
Descriptors - Atlantic cod, morphology, Newfoundland area, stock