Laboratory survival, growth, and digestive gland histologic features of squids reared on living and non-living fish diets.

The effects of non-living diets on the survival, growth, and digestive gland histologic features of the bigfin reef squid (Sepioteuthis lessoniana Lesson, 1830) cultured in the laboratory were evaluated during one-half of their life cycle (95 days). Two groups of squids (n = 16 per group) were held in closed seawater systems with similar water volume, temperature, salinity, water filtration, and water flow velocities. Food for the control group consisted of live, freely swimming fish (Cyprinodon variagatus); the test group was trained to grab freshly dead fish (days 1 to 45) and then thawed, frozen fish (days 46 to 95). The two groups were evaluated for differences in (1) food intake, (2) survival, (3) growth (wet weight, mantle length, instantaneous growth rate), (4) morphologic (mantle thickness in four locations, digestive gland weight), and (5) digestive gland histologic features (indices for nuclear density and relative vacuolar density). Unexpectedly, no significant differences were found between the two groups. Mean wet weight increased from 32.1 g to 342.9 g for the control group and from 58.6 g to 372.0 g for the group fed dead food. The results demonstrate that laboratory-cultured squids can survive and grow when fed dead fish (fresh or frozen) as well as live fish without adverse effects on growth, survival, or digestive gland histologic features.