Verification of Growth Dependent Survival in Early Life History of Pacific Saury Cololabis Saira Using Laboratory Experiment

To understand the survival processes in Pacific saury during the early life stages, growth histories were compared between individuals that died and those that survived under laboratory conditions. The morphology of Pacific saury drastically changed by 40 day after hatching (DAH) under 20°C, and during this period most individuals reached the juvenile stage (40 mm knob length (KnL)). From hatch to this period, high levels of mortality were observed. The back-calculated growth rates analyzed from otolith microstructure were compared among individuals that died and those that survived this period of metamorphosis. Growth rates of individuals that died were significantly lower since 1 DAH than surviving individuals. Factors contributing to mortality are considered to be the cumulative effects of their delayed growth and their less favorable body conditions (growth dependent survival). The body size (40 mm KnL) that is currently used to estimate the recruitment is concluded to be valid for evaluating the recruitment in the field.