Growth of sand whiff Citharichthys arenaceus and bay whiff Citharichthys spilopterus (pleuronectiformes: bothidae) in Puerto Rico (greater antilles) and North Carolina (USA), with comments on growth rate comparisons

Sagittal otoliths from two bothid flatfish species (Citharichthys arenaceus and C. spilopterus) collected in Puerto Rico were microstructurally examined and periodic increments counted. C. arenaceus length-at-age (33 to 246 days) data were best fitted by a Gompertz growth model whose parameters were estimated to be SL_∞ = 170 mm and K = 0.0166. Adult size is reached in less than one year. The peak period of hatching occurred in late spring, and settlement took place 39 days later. Due to a smaller age range (71 to 150 days), growth of C. spilopterus was described by a linear relationship with slope = 0.693 and intercept = −15.1 days. Hatching occurred in winter and spring. These two species showed no significant difference in age at settlement. After settlement, growth of C. spilopterus (0.69 mm·d⁻¹ at 71 to 113 days old) was significantly slower than that of C. arenaceus (1.00 mm·d⁻¹ at 71 to 113 days) possibly due to poorer environmental (abiotic or food-related) conditions during the dry, cool season (December–April). C. spilopterus from North Carolina, hatched in the same period, settled about two weeks older than in Puerto Rico. Growth after settlement was significantly slower in North Carolina (0.44 mm·d⁻¹ at 71 to 113 days) than in Puerto Rico. Environmental conditions (including temperature), distance between spawning areas and settlement grounds, and/or food availability, might explain the dissimilarity in growth observed between the two geographic areas. We recommend absolute field growth to be compared by using growth rates obtained by deriving the growth curve formula.