Individual growth history of larval Atlantic mackerel is reflected in daily condition indices

We tested the hypothesis that faster-growing Atlantic mackerel (Scomber scombrus) larvae generally achieve better feeding success than their slower-growing counterparts. Feeding success and growth were derived from the analysis of gut content and otolith microstructure of larvae from four cohorts (1997–2000) from the southern Gulf of St Lawrence. We observed a high degree of serial correlation in otolith growth (OG) from hatching, suggesting that events occurring early in life have long-standing effects on future growth potential. The diet of fast-growing individuals was dominated by large prey, such as cladocerans and fish larvae (including conspecifics), while slow-growing larvae foraged primarily on smaller copepod naupliar stages. Both feeding success (stomach content) and an index of condition (body depth) were positively correlated with OG, and these relationships explained approximately three times more variance in mackerel than in larval radiated shanny (Ulvaria subbifurcata) of similar size. Relationships linking age-dependent scores of body depth to feeding success and growth were ∼3.5–4 times stronger than those based on length-dependent indices, suggesting that differences in energy allocation during early ontogeny may play a significant role in determining an individual's capacity to cope with variations in feeding conditions.