Simple SummaryNorthern river terrapins can adapt physiologically or behaviorally across a salinity gradient, so that they can move between freshwater habitats and brackish water or estuaries. However, there is no available information on the optimal salinity of this species for supporting captive husbandry programs before release to natural habitat. In the current study, the optimal salinity for the terrapins was investigated to serve the well-being of turtles. At the end of the rearing period, various observed parameters related to growth, feed utilization, and health indicated that optimal salinity for rearing the terrapins is about 4 ppt, while rearing in freshwater (0 ppt) or other brackish (8 and 12 ppt) water conditions had negative effects on some key parameters that reflect well-being. A polynomial regression fit to terrapin weight gain as function of salinity predicts the optimal salinity as 4.35 ppt. Findings from the current study could be directly used in ex situ conservation programs of northern river terrapins before release to natural habitat. Additionally, concurrent conservation and restoration of the wild habitats with preferred salinity is essential for flourishing terrapin population.AbstractNorthern river terrapins (Batagur baska Gray, 1831) are Asia’s largest turtles living in both freshwater and brackish water. In the current study, the optimal salinity for head-starting programs of this critically endangered species was investigated in order to serve the well-being of turtles before release to natural habitat. Forty-eight terrapins (54.64 ± 0.18 g initial body weight) were randomly distributed to four salinity levels (0, 4, 8, and 12 ppt) and reared for eight weeks, using three replicates with four terrapins each. At the end of rearing trial, growth performance and feed utilization parameters were superior in terrapins reared at 4 ppt, followed by 8 ppt in the rank order of treatments. Negative stress responses were observed in terrapins reared at 12 ppt, as the fecal activity of amylase-to-trypsin ratio was changed significantly, but not that of proteolytic enzymes. The fecal thermal transition properties indicated an abundance of nutrients in the post-absorptive phase for terrapins reared at 4 ppt, followed by the 8 ppt treatment group. The preferred 4 ppt salinity had no negative effects on the health status of the terrapins in terms of carapace elemental composition or hematological parameters. Second-order polynomial regression suggests 4.35 ppt as the optimal salinity for maximal weight gain. Findings from the current study could be directly used in ex situ conservation programs of northern river terrapins before release to natural habitat.

The rearing of green turtles (Chelonia mydas Linnaeus, 1758) before their release to natural habitats has been practiced in several countries, whereas little information is available for inferring optimal husbandry protocols. This study aimed to improve the growth performance and feed utilization of posthatching green turtles by varying the water depth (15 or 30 cm) and feed pellet type (sinking or floating pellets). The 20-day-old turtles (23.49 ± 0.02 g initial body weight) were subjected to a 2 Â 2 factorial experiment (3 replications with 5 animals per tank) over a two-month duration. Growth, feed utilization, fecal digestive enzymes and hematological parameters were recorded to evaluate the effects of different treatments. No mortality was observed in any treatment group. Turtles reared in 15 cm water depth and fed with floating pellets exhibited superior growth (specific growth rate 2.76% body weight day À1 ) and feed utilization (feeding rate 1.42% body weight day À1 , feed conversion ratio 0.61 g feed g gain À1 , protein efficiency ratio 3.76 g gain g protein À1 ), relative to the other treatments. This treatment improved the utilization of nutrients by modulating trypsin specific activity but had no negative effects on hematological characteristics. Overall these findings indicate that the rearing program of post-hatching green turtles should be run with about 15 cm water depth and the preferred type of feed is floating pellets. These preferred conditions can also be applied in public displays, such as zoos or aquaria.

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Bigfin reef squid (Sepioteuthis lessoniana) is an economically important exported aquatic animal in Thailand, but little is known about its husbandry, which needs to be clarified. In this study, the ontogenic development of the main digestive enzymes (pepsin, trypsin, chymotrypsin, lipase and amylase) was investigated within 30 days after hatching (DAH). Fertilized eggs of the wild cuttlefish were hatched and then distributed into four replicate aquaria assigned to varying collection times (0, 5, 10, 15, 20, 25 and 30 DAH). The development of pepsin suggests acidic digestion functionality at 5 DAH, and its specific activity was maintained over the studied period. Specific activities of the serine proteases, trypsin and chymotrypsin, fluctuated significantly with similar pattern, and appear to be the key enzymes contributing ontogenic changes in protein catabolism. The specific activity of lipase was relatively high at 0 DAH, dramatically increased by 5 DAH, and then appeared constant until the end of observations, suggesting important role in utilizing the lipid from yolk at hatching, as well as probably in sparing protein utilization. Dramatic increase in amylase specific activity occurred by 10 DAH after which the activity was constant until 30 DAH, suggesting the utilization of carbohydrate as energy evolves comparatively late. Findings from the current study could be used to manage nutritional protocols according to the digestive enzyme patterns, as well as to develop artificial diets for rearing S. lessoniana.

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