Determination of Length-At-Age Relationship of Oversized Red Drum from the Northwestern Gulf of Mexico

The fish length-otolith length relationship is assumed to be linear in traditional length-at-age back-calculation methods. However, slow-growing fish such as red drum (Sciaenops ocellatus) are typically larger and heavier than fast-growing fish of the same size, thus traditional length-at-age back-calculation methods underestimate previous lengths at age. The purpose of this research was to determine the most accurate back-calculation method of length-at-age for oversized red drum in the northwestern Gulf of Mexico. We collected 81 oversized red drum from the nearshore waters in the vicinity of Corpus Christi, Texas between November 2010 and December 2011 using a variety of methods. Sagittal otoliths were extracted and marginal increment analysis was performed to determine age and yearly growth rate for each individual in the sample. Length-at-age was determined using both the Fraser-Lee method and the biological intercept method. The mean length of the red drum analyzed was 692.21 mm (SD=133.33). Preliminary results indicate that back-calculations of length-at-age for oversized red drum from the northwestern Gulf of Mexico are more accurate using the biological intercept method. The results of this study will contribute to development and/or modification of length-at-age keys for red drum by providing fishery managers with accurate back-calculated data for oversized red drum.