The Effects of Different Protein Sources on the Survival of Grass Shrimp, Penaeus Monodon (Fabricius, 1798) Larvae from Zoea to Postlarva (Decapoda, Natantia)

THE EFFECTS OF DIFFERENT PROTEIN SOURCES ON THE SURVIVAL OF GRASS SHRIMP, PENAEUS MONODON (FABRICIUS, 1798) LARVAE FROM ZOEA TO POSTLARVA (DECAPODA, NATANTIA)

S. S. SHEEN and H. T. HUANG Department of Aquaculture, National Taiwan Ocean University, Keelung, Taiwan 202, Republic of China

ABSTRACT

Two feeding trials were carried out with Penaeus monodon larvae in a small-scale system at a density of 100 individuals l-1 from zoea I to postlarva V in order to determine the effects of dietary protein quality (white fish meal, krill meal, and soybean meal) on survival, digestive enzyme activities, and protein digestibility in vitro. Zocae fed diet C, containing 41.5% krill meal, and 20% soybean meal, had a higher survival than those fed diet A, containing 45% fish meal and 26.5% krill meal, and diet B, containing 15% fish meal, 26.5% krill meal, and 20% soybean meal. In mysid larvae, however, diet A gave the highest survival. In order to set up the feeding regime for P. monodon larvae, diets A, B, and C were used alternatively to feed zoeae and mysids. Zoeac fed diet C and mysids fed diet A had the highest survival. Using whole zoeae, mysids, and postlarvae tissue as the reference protein, there were no signif- icant differences in essential amino acid index (EAAI) of the three experimental diets containing different protein sources. The digestive enzyme extracted from zoeac had a higher in vitro protein digestibility than those extracted from mysids. The activity of total protease was low during the nauplius stage and peaked at zoea II and mysis II. Also, the activity of α-amylase was low during the nauplius stage and peaked at zoea III and mysis II.

RÉSUMÉ

Deux expériences d'alimentation ont été effectuées avec des larves de Penaeus monodon dans un système réduit, à la densité de 100 individus l-1 de la zoé I à la postlarve V afin de déterminer les effets de la qualité du régime protéinique (farines de poisson blanc, de krill, de soja) sur la survie, les activités enzymatiques digestives, et la digestibilité des protéines in vitro. Les zoés nourries avec le régime C, contenant 41,5% de farine de poisson et 20% de farine de soja, avaient un taux de survie plus élevé que ceux nourris avec le régime A, contenant 45% de farine de poisson et 26,5% de farine de krill, ou qu'avec le régime B, contenant 15% de farine de poisson, 26,5% de farine de krill et 20% de farine de soja. Chez les larves mysis cependant, le regime A donnait le taux de survie le plus élevé. 910

Afin d'établir un régime d'alimentation pour les larves de P. monodon, les régimes, A, B et C ont été utilisés alternativement pour nourrir zoés et mysis. Les zoés nourries avec le régime C et les mysis nourries avec le régime A avaient le taux de survie le plus élevé. En utilisant le tissu de l'ensemble des zoés, mysis et postlarves comme protéine de référence, il n'y avait pas de différences significatives dans l' "essential amino acid index" (EAAI) des trois régimes expérimentaux contenant différentes sources de protéine. Les enzyme digestives extraites des zoés avaient une plus haute digestibilité des protéines in vitro que celles provenant des mysis. L'activité de la protéase totale était basse pendant le stade nauplius et culminait à la zoé II et à la mysis II. De même, l'activité de l'α-amylase était basse pendant le stade nauplius et culminait à la zoé III et à la mysis II.

INTRODUCTION

Penaeu.s monodon Fabricius, 1798, is considered a good crustacean to be cul- tured in Taiwan. Liao et al. (1969) paved the way for a P iiionodoti larviculture in Taiwan and established this species' larval rearing worldwide. Since then, mass production of P !11onodon larvae in hatcheries, and application of high quality formulated feed, made large-scale production of P monodon possible. In recent years, successful propagation of penaeid larvae was reported as a complete or partial replacement of artificial diets with live food. Therefore, it is necessary to know the nutritional requirements of penaeid larvae. Hatchery techniques for P. monodon are well established. P. monodon larvae develop through three herbivorous filter-feeding zoea stages (Z-I to Z-III) followed by three carnivorous feeding mysis stages (M-I to M-III) prior to metamorphosis to postlarvae (PL). In practice, microalgal feeds are supplied at least until the end of the mysis stages, with the addition of zooplankton, usually Artemia sp. nauplii, between Z-III and M-III (Jones et al., 1987; Liao, 1992). Raptorial feeding on zooplankton usually begins at the M-I, with a gradual de- cline in filter-feeding until the completion of the carnivorous stage (Rodriguez et al., 1994). Successful larviculture therefore, is known to depend predomi- nantly on live foods (Liao et al., 1983) which require tedious, labor intensive maintenance (Persoone & Claus, 1980), are expensive, and, furthermore, are of variable nutritional quality (Watanabe et al., 1983). Existing artificial alternatives such as frozen or freeze-dried natural products or microencapsulated diets have been developed. Since the artificial diets for penaeid larvae are available on the market, partial or complete replacement of living diets is now a routine in commercial hatcheries (Ottogalli, 1991). There- fore, this practice is in need of additional information on nutritional requirements for different stages of larvae. The larvae, which during metamorphosis survive on phytoplankton and zooplankton, must have a high degree of flexibility in their digestive physiology to