Reproductive performance, salinity tolerance, growth and production performance of a cryptic species Penaeus (Marsupenaeus) japonicus

Abstract

Kuruma shrimp Penaeus (Marsupenaeus) japonicus is a high-value penaeid shrimp in Japanese live fish markets owing to its characteristic colour and flavour. Although this species was believed to be the single species of subgenus Marsupenaeus, the exist-ence of two morphotypes (Form I and Form II) have been confirmed recently. Recent studies classified the native stock from Indian coast as Form II. Four different experi-ments were carried out to study the reproductive performance, larval survival, salinity tolerance and growout performance of P. japonicus Form II. The reproductive per-formance experiment was conducted using two treatment groups comprising female shrimp differentiated by the maturity stages (T1–Early maturing and T2–Immature). Female shrimp were unilaterally eyestalk ablated to accelerate the reproductive maturation. Although no significant differences (p > 0.05) were found in fecundity, spawning frequency, number of nauplii and hatching percentage between the treat-ments, early maturing shrimp had significantly lower (p < 0.05) latency period than the immature group (T1–14 ± 1.37 days vs., T2–25 ± 2.20 days). Additionally, larvae produced from the early maturing group (T1) had significantly higher (p < 0.05) sur-vival rate (37.7 ± 2.7%) at PL (post larvae) stage compared to the immature group (T2– 26.82 ± 2.38%). In the salinity tolerance study, PL reared at low salinities (5, 10 g/L) demonstrated similar (p > 0.05) mean body weight (BW) and survival (1.31–1.39 g, 63.3%) compared to shrimp reared at 25 g/L (1.46 g, 79.9%) at the end of 60 days. The 167 days farming trial at stocking density of 50 PL/m2 resulted in productivity of 0.55 kg/m2, with a mean BW of 20.48 ± 0.68 g and 55% survival. Low salinity produc-tion performance observed in this study indicates that the native P. japonicus Form II may be physiologically distinct from the other forms/stock elsewhere. The study also concludes the suitability of the species for brackishwater aquaculture