Hatch date and 0-group growth rate comparisons for cod (Gadus morhua) in Newfoundland waters: support for the match hypothesis

Pinsent, David L. (1995) Hatch date and 0-group growth rate comparisons for cod (Gadus morhua) in Newfoundland waters: support for the match hypothesis. Masters thesis, Memorial University of Newfoundland.

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Abstract

Lapillus otoliths of 0-group cod (Gadus morhua) were used to determine the day of hatching and length at age of individuals collected along the northeast coast of Newfoundland and on the southern Grand Bank in 1989 and 1991. Spatial pattern in the distribution of hatch dates was examined for latitudinal trends analogous to those of the spawning times in the area. Length at age analysis allowed the identification of specific areas and times where 0-group growth was greatest. -- Geographic distribution of cod hatching dates is neither consistently synchronous nor sequential in Newfoundland waters. A homogeneous pattern of hatch date distributions existed from the northeast coast of Newfoundland to southern Grand Bank in 1989, a year with average spring and summer water temperatures. In contrast, hatching dates during 1991, a year with below average spring and summer temperatures, exhibited a latitudinal progression from south to north. Hatching in the early part of a site-specific distribution resulted in first-feeding-larvae emerging at the onset of Calanus peak abundance. These larvae were characterized by a prolonged period of relatively slow growth. Those which began feeding later maintained rapid instantaneous growth for a short period. The result was that slower-growing, early larvae were actually larger than faster growing, later feeding larvae, by the end of their first year. Consequently, those that hatch early achieve a larger size at the end of one year.

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