Development of culture techniques for the Bornean giant freshwater crab (Isolapotamon bauense NG, 1987)
This thesis documents research on important aspects of the basic reproductive biology and culture of the Bornean giant freshwater crab Isolapotamon bauense encompassing inducement for spawning, fecundity, hatching rate, embryonic development, dietary protein requirements and optimum stocking densiti...
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| Format: | Thesis |
| Language: | English |
| Published: |
2022
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| Online Access: | http://ethesis.upm.edu.my/id/eprint/18082/1/t%20FSPH%202022%202.pdf |
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| Summary: | This thesis documents research on important aspects of the basic reproductive biology and culture of the Bornean giant freshwater crab Isolapotamon bauense encompassing inducement for spawning, fecundity, hatching rate, embryonic development, dietary protein requirements and optimum stocking densities. Isolapotamon bauense is a narrowly endemic freshwater Brachyuran species known only from the Bau region of Kuching, Sarawak. It is the largest true freshwater Potamid crab in Southeast Asia and is listed under the IUCN redlist of endangered species as Vulnearable. The current study represents the first scientific study into the reproductive biology, nutritional and stocking densitiy requirements of this species which have never been reported thus far. From the first study, the use of methyl farnesoate delivered via intramuscular injection was found to increase the probability of spawning in mature and mated female crabs. Crabs produced large macrolecithal eggs (diameter 3.7-4.1mm) with a low mean fecundity of 46.3 eggs per spawning and a mean hatching rate of 30.4%. The gestation period from spawning till hatching of eggs took between 36-45 days with embryonic development typical of other primary freshwater crabs. Evaluation of different levels of dietary protein (D.P) on the growth performance of Isolapotamon bauense, three diets were formulated with 30% D.P, 35% D.P and 40% D.P respectively., Diet containing 40% D.P performed the best in terms of specific growth rate (SGR) (1.19 ±0.220%) BW.day−1, feed efficiency ratio (FER) (0.42 ±0.032 %), feed conversion ratio (FCR) (2.21±0.167) g/biomass, weight gain (WG) (1.84±0.178) g and molting frequency (MF) (4.13±1.458%) molts. Crabs fed with diet containing 40% D.P were found to have a significantly higher protein content compared to the other treatments. The final experiment details the influence of three different stocking densities (treatment 1=5 crabs/m2, treatment 2=10 crabs/m2 and treatment 3=15 crabs/m2) on the survival rate (%), cannibalism rate (%), carapace width (CW) increment (%) and molting frequency (MF) on Isolapotamon bauense juveniles in a 90 day trial. The results showed that the lowest stocking density used in the experiment, at 5 crabs/m2 returned the most promising results. The stocking density of 5 crabs/m2 had the highest survival rate (100% for the duration of the trial), lowest cannibalism rate (0% for the duration of the trial), highest carapace width (CW) increment (13.9% for the duration of the trial) and highest molting frequency (2.44 times per animal for the duration of the trial). In general this research sheds important light on basic biological, nutritional and stocking density aspects of the giant mountain crab I. Bauense. |
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