Relative growth of larvae of Pacific pink shrimp Pandalus eous under laboratory conditions

The relative growth and swimming behavior of larval Pandalus eous were examined for reared individuals during the zoeal and postlarval stages. Larval rearing was conducted using a 20 U tank maintained at a mean temperature of 8.0degreesC, and larvae were fed with diatoms (Thalassiosira spp.) and Artemia nauplii. Larval development consisted of seven zoeal stages and metamorphosis to the first postlarval stage (decapodid stage) occurred after 54 days. Larval characteristics were examined based on morphological development, swimming behavior, and points of change in relative growth of body parts to carapace length expressed in terms of allometric equations. The first and second zoeal stages were a period of transition during which swimming behavior changed from passive to active. All body appendages appeared in the third zoeal stage and active swimming behavior was fully apparent in the fourth zoeal stage. Between the sixth and seventh zoeal stages, larval behavior changed gradually from pelagic to benthic. After metamorphosis to the first postlarval stage, larvae became fully benthic. The points of change in relative growth occurred at two molting periods, that between the second and third zoeal stages, and that between the fourth and fifth zoeal stages. These points coincided with the critical periods at which larval mass mortality ordinarily occurs during seed production.