Robert G. Howells

Grass Carp Reproduction in the Lower Trinity River,Texas

Reports of grass carp (Ctenopharyngodon idella) from the lower Trinity River and Trinity-Galveston Bay of southeastern Texas prompted concerns that this introduced fish may be successfully spawning and recruiting in local waters. To examine these possibilities, Texas Parks and Wildlife Department (TPWD) personnel conducted icthyoplankton sampling from April through July 1992 and 1993 and electron shed during July and August 1993 in the lower Trinity River. Additionally, fish-kill records from the Trinity-Galveston Bay area were examined. Icthyoplanton samples taken in 1992 and 1993...


Age Estimation and Length Back-calculation for Known-age Largemouth Bass

Scales and otoliths from largemouth bass (Micropterus salmoides) of known ages (age 6, 7, and 8) were prepared and examined by 3 experienced readers who were uninformed of specimen age or length. Results indicated limited agreement between readers and numerous inaccurate age estimations. Among 97 scale samples read, all 3 readers only agreed on the age of a single specimen which was older than estimated; using otoliths, readers agreed on 4 specimens which were correctly aged. Percentage of correctly-aged fish ranged from 10% to 30% with scales and 39% to 47% with otoliths. Percent of fish...