Estuarine Use of Red Drum Inferred through Otolith Microchemistry

Red Drum (Sciaenops ocellatus) is a popular gamefish in the Gulf of Mexico and is known to use estuarine waters. However, little is known about the duration, extent, and degree of variability among fish in estuarine habitat use. Otolith microchemistry provides an ideal tool to investigate this because it can provide a temporal record of different water chemistries and therefore salinities, experienced by each fish. Lifetime Strontium (Sr) and Barium (Ba) concentrations of otoliths were analyzed using LA-ICPMS (n=47). Straight-line laser ablations were run parallel to the sulcal groove from the core to the edge. For both elements, concentration at each age class was treated as a response variable and four groups of fish were identified using cluster analysis and MDS plots based on Euclidean distance. SIMPER analysis demonstrated that group 1 had higher Ba at all ages, group 2 had low Sr at ages 2-7, and group 3 and 4 differed in Sr concentrations at age 8-10. These results demonstrate that Red Drum estuarine use varies not only spatially, but also in duration of time spent in estuarine waters. Our findings suggest that distinct contingents of Red Drum within Mobile Bay are highly probable.