Age, Growth, and Distributions of the Giant Snake Eel, Ophichthus Rex, in the Gulf of Mexico

Giant snake eels, Ophichthus rex, were collected from the northern Gulf of Mexico employing commercial long-lining techniques. Monthly samples of 30 eels were taken between March 1988 and February 1989 (except July, September, and November). Age and growth parameters were estimated using sectioned otoliths read under a compound microscope. Eels captured ranged in length from 83.0 to 212.0 cm, in weight from 0.75 to 19.0 kg, and in age from 4 to 30 yrs. Sex ratio was significantly skewed towards females (4:1). Total length-weight relationships were exponential and the resultant natural log transformed data exhibited a significant linear relationship; no significant differences were found between the sexes. Difficulty in reading ototliths due to multiple banding patterns and false annuli led to substantial variation in total length at age. Growth was modeled using the von Bertalanffy growth function and back-calculated lengths. Results indicated females grew faster and attained a greater asymptotic total length than males. Marginal increment analysis was used to evaluate periodicity of annuli formation and suggested rings were laid down in late winter (February–March). Instantaneous mortality rates were similar to those of other longer-living anguilliforms and suggested these animals may reside in relatively stable habitats.