Age and growth of red tilefish Branchiostegus japonicus in two fishery grounds off the Kaetsu region, Niigata Prefecture, northern Sea of Japan

Abstract

The age and growth of red tilefish Branchiostegus japonicus in two fishery grounds off the Kaetsu region, Niigata Prefecture, northern Sea of Japan were examined using otolith cross-section and surface methods. Assuming annual formation of ring marks and a hatching date of 1 September, inferred on the basis of observed monthly changes in the proportion of mature females (gonadosomatic index ≥ 2.5), ages were assigned to individuals according to the number of ring marks. The von Bertalanffy growth equations for females and males in the coastal fishery ground off the Kaetsu region (KFG) and a relatively offshore fishery ground near Awashima Island (AWFG) were as follows: $L_{t} ({\text{mm}}) = 349 \left[ {1 - \exp \left\{ { - \,0.342 \left( {t\, + \,0.350} \right)} \right\}} \right]$ and $L_{t} ({\text{mm}}) = 489 \left[ {1 - \exp \left\{ { - \,0.237 \left( {t\, + \,0.396} \right)} \right\}} \right]$ for KFG, $L_{t} ({\text{mm}}) = 278 \left[ {1 - \exp \left\{ { - \,0.571 \left( {t - 0.372} \right)} \right\}} \right]$ and $L_{t} ({\text{mm}}) = 509 \left[ {1 - \exp \left\{ { - \,0.183 \left( {t\, + \,0.152} \right)} \right\}} \right]$ for AWFG, respectively. Estimated total length (TL) at each age for females and males from these equations was larger for KFG than for AWFG. Observed maximum age was 40 and 32 years for female and male from KFG, respectively, both being approximately twice the maximum age reported in other waters, including AWFG.