Fin Ray Removal May Be Deleterious to Pallid Sturgeon

Abstract

AbstractCalcified fin structures are frequently used to gain an understanding of the age structure of fish populations. For Pallid Sturgeon Scaphirhynchus albus, fin rays have recently been used in microchemistry assessments to understand natal origin and interbasin movements. Although several published studies have shown minor to no ill effects from the removal of the first pectoral fin ray on other sturgeon species, it is unknown how fin ray removal affects Pallid Sturgeon over the long term in an altered river system. Therefore, our objectives were to compare recapture and survival rates of subadult (<800‐mm) and adult (≥800‐mm) Pallid Sturgeon in the lower Missouri River for fish with and without a fin ray section removed. Recapture efforts resulted in a higher recapture frequency for Pallid Sturgeon that did not have a fin ray section removed (26%) compared to those that had a fin ray section removed (11%). Subadult‐sized Pallid Sturgeon appeared to be more sensitive to fin ray removal: no subadults with a fin ray removed were recaptured, whereas recapture frequency was 22% for subadults with fin rays intact. An apparent survival estimate was not quantifiable for subadults with a section of fin ray removed, but the model estimated a 0.42 apparent survival rate for subadults with intact fin rays. Adult‐sized Pallid Sturgeon were recaptured at similar frequencies (fin ray removed: 23%; fin rays intact: 34%), and apparent survival estimates did not differ between the two groups of adults. Survival estimates are considered “apparent,” as the model could not differentiate between mortality and emigration. Our results represent a departure from previously published literature and suggest that fin ray removal may be deleterious to the survival and recovery of Pallid Sturgeon. The potential effects of fin ray removal must be thoroughly considered before initiation of future studies.