Size frequency, length-weight relationships, condition factor and relationships between fish size and otolith dimensions in the Pama croaker Otolithoides pama (Hamilton, 1822) from Lower Meghna River Estuary, Bangladesh

The relationships between fish size, weight and otolith morphometry are useful for fisheries management, predator–prey studies and feeding habits. Accordingly, the main purpose of the present study was to determine the relationships between body length, body weight and otolith dimensions, and to calculate the length-weight relationship and condition factor for a Sciaenid fish Pama croaker, Otolithoides pama (Hamilton, 1822) from the Lower Meghna estuary, Bangladesh. Field sampling was conducted from September 2019 to March 2020. The length, breadth and weight were measured for each pair of sagittae, as well as the total length (TL), standard length (SL) and body weight (BW) for each specimen. A total of 246 fish samples were collected. The TL and BW of collected individuals ranged from 14.40 to 27.40-cm and 21 to 175-g, respectively. The calculated growth coefficient (b = 3.018 for males; 3.052 for females) were >3, indicating the fish follow a positive allometric growth. The mean Fulton's condition (Kn) values ranged from 0.674 ± 0.06 to 0.776 ± 0.07, exhibiting similar trends for all size classes. The relationships for fish size and otolith morphometry were described by linear regression models as TL = 0.048OL – 0.308 (r² = 0.921); BW = 0.047OL + 6.252 (r² = 0.929); TL = 0.003OW – 0.414 (r² = 0.836); BW = 0.003OW + 0.039 (r² = 0.81). The otolith length and weight exhibited a strong correlation (0.929 > r² > 0.805) with total length and body weight, while the otolith breadth exhibited a weak correlation. No significant differences between left and right otolith were observed (p > .05). Because the results of the present study indicated fish length and otolith growth have a positive relationship, this finding can be a valuable tool to evaluate fish growth by back-calculating the length of a fish from its otolith characteristics.