Effects of Practices Related to Catch-and-Release Angling on Mortality and Viral Transmission in Juvenile Largemouth Bass Infected with Largemouth Bass Virus

—Largemouth bass virus (LMBV; family Iridoviridae) has recently emerged as a causative agent in fish kills of largemouth bass Micropterus salmoides. Little is known about how the virus is transmitted or what factors predispose fish to mortality subsequent to infection. Concern has nevertheless arisen that activities related to recreational angling may affect transmission dynamics and may alter the susceptibility of infected fish to clinical disease. This study examined the separate effects of two angling-related factors on the susceptibility of juvenile largemouth bass to mortality from LMBV infection and on the transmission of LMBV from infected to uninfected fish. The first factor was hook-and-line angling. Infected fish that underwent a simulated angling treatment did not experience higher mortality or have higher viral loads in their tissues than those that were not angled. The second factor was direct contact between infected and uninfected fish, as would occur in live wells and holding tanks. The LMBV was transmitted from infected to uninfected fish through water, even when direct contact was prevented. Transmission of LMBV between infected and uninfected fish separated by a fenestrated barrier was nearly as efficient as LMBV transmission between infected and uninfected fish that were allowed direct contact. These results imply that angling itself may have only minimal effects on the survival of largemouth bass infected with LMBV but that angling-related practices that place infected and uninfected fish together in a limited water volume may facilitate viral transmission. Partitioning or cooling of live wells and holding tanks, as well as limiting their use, could reduce LMBV-associated mortality and viral transmission. Largemouth bass virus (LMBV; family Iridoviridae; Plumb et al. 1996) is the only virus known to cause epidemic mortality in wild largemouth bass Micropterus salmoides (Grizzle and Brunner 2003). The LMBV has been associated with largescale fish kills in largemouth bass, particularly during warm seasons (Plumb et al. 1996; Hanson et al. 2001). While certain populations of infected * Corresponding author: [email protected]. Received September 8, 2004; accepted January 2, 2005 Published online August 24, 2005 largemouth bass have suffered fish kills, other infected populations suffer no discernible clinical signs, suggesting that key environmental factors may play a role in the pathogenesis of LMBV. Such factors may also play a role in the transmission of LMBV between fish and between bodies of water