Conservation, Ecology, and Management of Catfish: The Second International Symposium

<em>Abstract</em>.—Natural chemical markers in otoliths and fin rays have proven useful for retrospectively describing environmental history of fishes in a variety of environments. However, no studies have applied this technique to catfishes or evaluated catfish pectoral spine chemistry as a nonlethal alternative to otolith chemistry. We characterized relationships between water, otolith, and pectoral spine (articulating process) chemistry for channel catfish <em>Ictalurus punctatus</em>, flathead catfish <em>Pylodictis olivaris</em>, and blue catfish <em>I. furcatus</em> and determined the accuracy with which fish could be classified to their environment of capture using otolith and pectoral spine chemical signatures. Fish and water samples were collected from nine sites during 2009. Otolith, spine, and water samples were analyzed for Sr:Ca and Ba:Ca; otolith δ¹⁸O and δ¹³C and water δ¹⁸O were also measured. Water, otolith, and spine Sr:Ca were highly correlated, as were water and otolith δ¹⁸O. Relationships between water, otolith, and spine chemistry did not differ among species. Otolith Sr:Ca, δ¹⁸O, and δ¹³C and spine Sr:Ca differed among sites, reflecting geographic differences in water chemistry. Neither otolith nor spine Ba:Ca differed among sites despite intersite differences in water Ba:Ca. Both otolith Sr:Ca, δ¹⁸O, and δ¹³C and fin spine Sr:Ca classified fish to their environment of capture with a high degree of accuracy, except in the middle and lower Mississippi River where many recent immigrants appeared to be present. Natural chemical signatures in otoliths or pectoral spines will likely be effective for reconstructing environmental history of catfishes when spatial differences in water chemistry are present, enabling investigations of stock mixing and recruitment sources for these species.