Impacts of mycobacteriosis on the growth of striped bass (Morone saxatilis) in Chesapeake Bay

The striped bass (Morone saxatilis) is an economically and ecologically valuable finfish species that inhabits nearshore and estuarine waters of many states along the US Atlantic coast. Chesapeake Bay provides extensive nursery and foraging habitats for striped bass, yet fish in the bay exhibit high prevalence of disease caused by bacteria in the genus My- cobacterium. Detection of population-level impacts associated with mycobacteriosis has been difficult because the disease is chronic and synoptic biological and disease data have been limited. Here, we present modeling analyses of growth data for disease-positive and -negative striped bass in Chesapeake Bay. Three growth relationships were considered, and for each, a single model was parameterized to include several covariates, most notably disease status and severity. Our results indicate that disease-positive and -negative fish have differing growth patterns and that the estimated asymptotic sizes of disease- positive fish are considerably lower than those of disease-negative fish. Compromised growth along with documentation that striped bass in Chesapeake Bay are experiencing disease-associated mortality suggests that disease may be reducing the pro- ductivity of this species. Resume : Le bar raye (Morone saxatilis) est un poisson teleosteen de grande importance economique et ecologique qui ha- bite les eaux cotieres et estuariennes de plusieurs etats de la cote atlantique des E.-U. La baie de Chesapeake fournit d'im- portants habitats de nourricerie et d'alimentation au bar raye, bien que les bars dans la baie connaissent une forte prevalence de maladie causee par des bacteries du genre Mycobacterium. La detection des impacts de la mycobacteriose au niveau de la population est difficile, car la maladie est chronique et il existe peu de donnees synoptiques sur la biologie et la maladie. Nous fournissons ici des donnees de croissance dans la baie de Chesapeake chez des bars rayes presentant une reaction positive a la maladie et d'autres une reaction negative. Nous avons tenu compte de trois relations de croissance et, pour chacune, nous avons parametre un seul modele de maniere a inclure plusieurs covariables, en particulier le statut et la severite de la maladie. Les poissons a reaction positive et negative affichent des patrons de croissance differents et les tailles estimees a l'asymptote des poissons a reaction positive sont considerablement inferieures a celles des poissons a reaction ne- gative. La croissance restreinte, ainsi que l'evidence de mortalite associee a la maladie, laissent croire que la maladie est en train de reduire la productivite du bar raye dans la baie de Chesapeake. (Traduit par la Redaction)