Condition Dynamics of Juvenile Fishes throughout Virginia Estuaries

Indices of relative abundance of juvenile fish are typically used to assess year-class strength, however, purportedly strong year classes may not always produce subsequent recruits to the fishery.  The condition of individuals in a year class may contribute to recruitment variability due to differential survival of poor- and well-conditioned fish.  Lipid and energy content are standard measures of condition, and are important for promoting survival during periods of food scarcity or environmental stress.  We hypothesize that variation in condition of juvenile Summer Flounder and Atlantic Croaker reflects inter-annual environmental changes, and differential suitability of nursery areas.  Condition of individual fish was assessed monthly from June 2011 to January 2014 using non-lethal metrics that correlated strongly with lipid and energy content for these species: Fulton’s condition factor for Summer Flounder and lipid estimates from the Distell fish fatmeter for Atlantic Croaker.  Mean condition differed among years for both Summer Flounder (n=2,357) and Atlantic Croaker (n=3,762); seasonal patterns in mean condition were apparent for both species.  The heterogeneous environment in Virginia estuaries resulted in notably different spatial patterns in condition of each species.  Yet, most of the variability in condition occurred among individuals, suggesting individual traits ultimately determine survival and recruitment.