Growth patterns of saffron cod <i>Eleginus gracilis</i> Tilesius (Gadidae) in the first year of life

Abstract

Patterns of linear and weight growth of saffron cod in the first year of life are considered on the data of measurements and cited materials for different habitats of this species. The growth curve is approximated by logistic function. Monthly increments for the body length of larvae and fry are about 50–60 % in the first four months of life with the highest growth rate. Then the relative growth decreases significantly in fall-winter and does not exceed 1–4 % to the end of the first year of life. The absolute length increments increase during the first half of the year up to the maximum value of 25–30 mm/month in late summer – early autumn. Saffron cod grow faster in the southern areas of their habitat. The weight growth patterns are different from the linear growth. The weight growth is higher in the first five months of life, with gradual decreasing of the monthly weight increments form 156 % to 105 %. The relative weight increments exceed significantly the length increments in this period. When the body weight reaches app. 5 g, the relative weight increments decrease abruptly, though the absolute increments continue to increase until the 6–8th months of life when they reach 5–6 g per month for fish with body length > 86 mm. The body weight increases by 60 % in this short period of the highest weight growth. Time lag between the peaks of absolute linear growth (in July-September) and weight growth (in September-November) is about 2 months.

Keywords

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