Suitable formulation of moist diet for newly hatched bigfin reef squid (Sepioteuthis lessoniana)

The bigfin reef squid (Sepioteuthis lessoniana) is a cephalopod with significant potential as a farmed species. However, uncertainty surrounds the optimal feed formulation and feed strategy for S. lessoniana, especially for the early stages. This study aimed to develop a suitable moist diet formulation to improve growth performance and feed utilization of young squid. Initially, eight moist meat-based diet formulations were screened using an in vitro digestibility technique. Four formulations were considered suitable: the meat of Indian mackerel (IM), the conventional ration of whiteleg shrimp (WS), Indian mackerel and trash fish (IT), and Indian mackerel, striped catfish and trash fish (IST). An in vivo feeding trial was conducted, using a completely randomized design with triplicate groups of eight-day-old squid (39.0 ± 0.1 mg initial weight) for two weeks. Newly hatched squid fed the IST diet showed significantly higher growth than other groups, followed by squid fed the IT diet (P < 0.05). The IST group showed the lowest feed conversion ratio but moderate protein efficiency ratio. Feed intake and survival rate, however, did not vary significantly across the groups. Proteinase-specific activity was higher in the IST group, and levels of mantle myosin and its sum with actin were significantly elevated compared to other groups. There were no significant differences in mantle RNA concentration, protein concentration, and RNA/protein ratio between IT and IST groups and the WS group. These findings suggest that a well-formulated artificial diet for newly hatched bigfin reef squid can improve their growth and feed efficiency.