Largemouth bass virus in Texas: distribution and management issues.

In response to fish kills at prominent fishing sites for largemouth bass Micropterus salmoides, such as Lake Fork and Sam Rayburn Reservoir, the Texas Parks and Wildlife Department began a systematic evaluation of state waters for the presence of largemouth bass virus (LMBV). The survey comprised 49 water bodies and 13 river basins, and a total of 2,876 adult bass were collected by electrofishing and angling during the summer and fall of 2000. The virus was initially detected by means of cell culture and its presence subsequently confirmed by polymerase chain reaction. Fourteen reservoirs in eight river basins in eastern and central Texas tested positive for LMBV. Lake Fork was also tested to determine the prevalence of infection following a 1999 LMBV fish kill. The overall prevalence was low in all of the water bodies tested (1.50 +/- 2.82% [mean +/- SD]) as well as those determined to contain LMBV (5.00 +/- 3.02%). Largemouth bass testing positive for LMBV had a significantly higher prevalence of swim bladder anomalies, but this condition was not a good indicator of LMBV infection. No significant relationships were found between LMBV-positive fish and other factors investigated, including the presence or absence of grossly visible injury, hook marks, external parasites, known water quality problems, gender, allozyme-phenotype, method of capture, length, weight, body condition (relative weight), or age. This survey provided a means of gathering scientific information about LMBV, including its distribution in Texas. From the information gained by this survey, prior fish kills, and previous sampling efforts, a total of 19 water bodies within 9 of the 13 major river basins in the state were found to contain the virus. These results were used to guide a statewide fish stocking strategy aimed at preventing the spread of LMBV in Texas and to contribute to a nationwide effort to understand this virus and its effects on largemouth bass fisheries.