Optimal-rearing density for head-starting green turtles (Chelonia mydasLinnaeus, 1758)

Abstract

While ex situ conservation programs of juvenile green turtles (Chelonia mydas Linnaeus, 1758), before release to natural habitats, have been conducted in several countries, the optimal-stocking density for husbandry has not yet been reported. The optimization of stocking density was the main purpose of this study. The 15-day-old post-hatching turtles (29.30 ± 0.05 g body weight) were reared in round fiberglass tanks at various stocking densities including 20 turtles/m (20TM), 40 turtles/m (40TM), 60 turtles/m (60TM), and 80 turtles/m (80TM), over an 8-week trial. Water quality, survival, growth performance, feed utilization, aggressive behavior, fecal digestive enzymes, and hematological parameters were compared between the treatments, and were used as indicators of a successful captive rearing program. The water quality across the four treatments was in the standard range, but a high-stocking density reduced the quality significantly. No mortality was observed in any treatment group. Superior growth and feed utilization were only observed with the 40TM treatment, relative to the others (P < 0.05). The turtles in this group had no aggressive behavior, as indicated by observing hind limb biting. This treatment manipulated the level of proteolytic activity of pepsin and trypsin in response to density stressor, but not amylase, lipase, and chymotrypsin. The 40TM treatment also maintained the hematological characteristics, indicating no negative effects on health status. Overall, the findings indicate that the captivity program of post-hatching turtles at 40 turtles/m is the preferred option in their head-started propagation, as well as in public displays in zoos or aquaria. Zoo Biol. 35:454-461, 2016. © Wiley Periodicals, Inc.

Optimal Background Color for Head-Starting Northern River Terrapins (Batagur baska Gray, 1831)

“…However, this kind of comparative study can be performed with other non-endangered model turtle species, such as soft-shelled turtles (Pelodiscus sinensis), to collect more evidence prior to application in endangered species. Recently, the specific activities of gastric and pancreatic enzymes in fecal samples have been used as indicators for monitoring feed utilization in green turtles [18][19][20]26,33]. In the current study, the effects of background color on the specific activities of these digestive enzymes were clearly observed.…”

“…The determination of digestive enzyme activities in order to assess feed utilization is a reasonable approach [16,17]. For endangered species, investigations of specific activity of gastric and pancreatic enzymes in fecal samples and fecal thermal properties have been demonstrated to provide information about available nutrients in feces [18][19][20]. These approaches are non-lethal, non-invasive, and not in conflict with ethical standards.…”

5334000-53340000Optimal Salinity for Head-Starting Northern River Terrapins (Batagur baska Gray, 1831)

“…Physiological changes reflecting feed utilization were assessed via the thermal properties of feces in the current study. This technique has been used in our previous studies on endangered animals, as a non-invasive method is needed [14,15,33]. Comparative differences between rearing terrapins in fresh or brackish water were clearly observed, along with the four peaks indicating remaining available nutrients (low temperature, peaks 1 and 2) and unavailable nutrients (high temperature, peaks 3 and 4) present in the feces.…”

Optimal Feeding Frequency for Captive Hawksbill Sea Turtle (Eretmochelys imbricata)

“…Significant changes in digestive enzyme activities relate with fecal thermal properties, since the thermogram from DSC reflects the native amount of nutrients present in feces after digestion and absorption [ 9 , 18 , 21 , 49 ]. Generally, the low temperature peaks (peaks 1 and 2) detect available nutrients, mainly protein, nitrogen-free extract, and lipid, while the high temperature peaks (peaks 3 and 4) refer to unavailable composition, probably crude fiber [ 40 ].…”