Otolith micro-structure analysis of rainbow trout alevins (Oncorhynchus mykiss) under rearing conditions

otolith microstructure (mo) analysis was used to back-calculate growth patterns from hatching to the yolk-sac absorption in rainbow trout alevins (oncorhynchus mykiss), under experimental conditions, from winter to spring in central-chile. mo showed the following main features: (i) occurrences of multiple primordia in the central region of otolith (mp); (ii) several increments (22 ± 3 rings) before a prominent hatch check surrounding mp and (iii) existence of a very distinctive check associated to yolk-sac absorption. further findings were the validation of daily periodicity of micro-increments and a significant linear relationship (p < 0.001; r2 = 0.91) between the maximum otolith length (mol) and total length (tl) of alevins. the linear mol-tl relationship validated the use of the biological intercept method to back-calculate daily growth rates. growth rates profiles followed a decreasing trend from hatching to the end of yolk-sac period (16 ± 1 days), ranging from 0.34 mm d-1 to 0.22 mm d-1 (0.30 ± 0.037). mo analysis demonstrated to be a powerful tool in back-calculating growth patterns of alevins once they had absorbed their yolk-sac.