Age and Growth of Flathead Catfish from Pools 12 and 13 of the Upper Mississippi River
Michael J. Steuck and Caleb C. Schnitzler
Abstract.—Characterizing dynamics of a fish population requires accurate age estimation for individual fish, and few studies have collected basic age and growth information for flathead catfish in the upper Mississippi River (UMR). Multiple methods were used to calculate age and growth of flathead catfish from the UMR. Length at age was determined using sectioned otoliths and pectoral spines cut on the articulating process. Most research has shown that otoliths provide the most accurate age when compared to other structures. Otoliths require sacrifice of many fish, including very large fish (i.e.: >762 mm). Otoliths and pectoral spines were collected from commercially harvested flathead catfish from Pools 12 and 13 (river kilometer [rkm] 841.0–938.3), UMR, aged and compared. Growth was similar between genders, and there was little difference in growth predicted by the two aging structures. Spine articulating processes and otoliths both showed high variability in growth starting at age 1. When we compared the two structures, the spine articulating process accurately aged fish up to 17 years old (mean total length = 907 mm) before loss of annuli occurred. Aging flathead catfish with the spine articulating process provides an accurate, reliable, affordable, nonlethal aging technique that may be preferable in many situations as opposed to otoliths. Annual and seasonal growth was calculated from flathead catfish captured from Pool 13 (rkm 841.0–895.9), UMR, tagged with a visual implant tag and subsequently recaptured. Actual growth over the summer was estimated to be 0.25 mm/d, and growth from year to year was estimated to be 32 mm/year. The actual annual growth (31.9 mm/year) calculated from tag returns validates estimates of annual growth derived from otolith (30.2 mm/year) and spine articulating process (31.0 mm/ year) aging techniques.