Growth of pacific cod <i>Gadus macrocephalus</i> in the first year of life

Abstract

Data of observations and published materials on linear and weight growth of pacific cod in the first year of life are analyzed for different habitats. The growth curve is approximated by logistic function. Monthly increments for the body length of larvae and fry are about 50 % in the first three months of life, when growth is the most intense. Absolute length increments increase in the first half of the year and reach the maximum of 25-30 mm per month in late summer — early autumn, then decrease in the rest of the year. Relative body length increments decrease in autumn and winter, too. The cod grow faster in southern areas. Weight growth patterns are different from the linear growth. The weight growth is the most intense in the first half of year, when relative weight increments exceed significantly the length increments — monthly weight increments decrease gradually form 142 % in the first month of life to 85 % in the sixth month. When the weight reaches app. 4 g, the relative weight increments decrease abruptly though the absolute increments continue to increase until the 7–9th months of life when they reach 8–10 g per month for fish with body length > 10 cm. The cod weight increases by 58 % in this short period of the highest growth. Time lag between the peaks of absolute increments of length (in the sixth month of life) and weight (in the eighth month) is about 2 months

Keywords

• pacific cod
• linear growth
• weight growth
• relative increment
• absolute increment
• logistic function
• habitat