Changes in body composition and morphology of young‐of‐the‐year gulf menhaden, Brevoortia patronus Goode, in Fourleague Bay, Louisiana

Abstract

Body composition (lipid, water, protein, energy content) and metamorphosis of young‐of‐the‐year gulf menhaden, Brevoortia patronus Goode, were examined over a yearly cycle in Fourleague Bay, Louisiana. Metamorphosis from larvae to juveniles, as indicated by the body depth to length ratio, was completed by 30 mm S.L. Analysis of the length/weight relationship indicated separate equations for larvae/postlarvae (< 30 mm S.L.) and juvenile/subadults (30–100 mm S.L.). Major body composition changes from larvae to subadult included an increase in lipid content, a corresponding increase in energy content, and a decrease in nitrogen content. Young‐of‐the‐year gulf menhaden did not exhibit the seasonal pattern of condition factors typical of adult clupeids. There may be a shift in energy allocation away from protein growth to lipid storage associated with attainment of a larger size. Initiation of emigration may be related to lipid storage and temperature change, with higher lipid content fish migrating first. End‐of‐year variations in fish size and lipid storage may be related to environmental conditions, such as water temperature and salinity.