Abstract

The red snapper is the most economically important reef fish species in the Gulf of Mexico (GOM). The GOM stock is currently considered overfished and undergoing overfishing. Accurate age information is critical in calculating growth rate, mortality and productivity. These variables are necessary to monitor year-class strength, conduct stock assessments, and document population recovery. Sectioned otoliths are considered the most reliable method for ageing red snapper but are difficult to read. Interpretation of the putative first annulus in particular has been a major source of disagreement between readers, owing to a diffuse appearance and varying position relative to the otolith core. In an effort to validate timing of first annulus formation, sixteen juvenile red snapper were collected from research trawls and transferred to circular holding tanks at the Louisiana Universities Marine Consortium on October 28, 2005. The fish were given two weeks to recover and were then immersed in small tanks of seawater with 100 mg/L of alizarin complexone for two hours. Fish then then placed back into holding tanks and held through late spring of 2006 (the time of year when red snapper have been shown to deposit opaque annuli on their otoliths). In mid-July 2006 the red snapper were sacrificed and otoliths removed and examined under ultraviolet light. Otolith sections exhibited a diffuse opaque ring between the fluorescent calcein ring and the otolith margin indicating that the diffuse opaque region is the first opaque annulus.

PDF Preview