Sharr Azni Harmin

Association of annual hormonal profile with gonad maturity of mahseer (Tor tambroides) in captivity.

Annual gonad hormonal profile of wild, matured mahseer (29 males and 23 female) averaging in weight between 0.95±0.26 and 1.19±0.23 kg for males and females, respectively, were investigated from November 2007 to November 2008 using enzyme-linked immunosorbent assay (ELISA) technique. Blood was collected from caudal vein, monthly and plasma separation by centrifugation was done to measure reproductive hormones: 17β-estradiol (E(2)), testosterone (T), and 11-keto-testosterone (11KT). Gonads were sampled for histology processing to observe their maturity. Highest T level in females and males was recorded at 0.22±0.016 and 0.88±0.014 ng/ml, respectively. The 11KT showed several peaks and the highest value was noted at 0.7±0.018 ng/ml in November 2008. The female E(2) initially was at 1.48±0.16 ng/ml and significantly increased (P<0.05) to 1.53±0.39 ng/ml in November 2008. Ovaries were laden with oocytes in several stages in all the samples while testes gonad showed a high level of spermatids throughout the year. Changes in plasma level of the gonadal hormones were correlated with the ovarian and testes maturities. In conclusion, the study suggests that mahseer can be categorized as asynchronized and multiple spawner. The information gathered is important for appropriate breeding and conservation programs of the Malaysian mahseer.

Ovarian development of a river catfish Hemibagrus nemurus (Valenciennes, 1840) in captivity.

Hemibagrus nemurus is a riverine catfish with high economic and nutritive values. Investigations on ovarian development of this fish were carried out to determine the mode of ovarian development and describe the oocyte developmental stages. Histological studies were done on ovaries using light microscopy and scanning electron microscopy. Fish were sampled monthly for a period of six months (August 2009 to January 2010). The mean oocyte diameter (OD) ranged from 871 ± 161.41 µm to 1,167 ± 26.77 µm and the highest OD was in November. Oocyte size-frequency distribution showed a polymodal distribution. The mean gonadosomatic index (GSI) ranged from 1.14 ± 0.87% to 7.06 ± 1.40% and highest GSI was in November. The ovaries exhibited three phases of oocyte growth, which were primary growth, secondary growth and maturation phases. Based on histological criteria, the oocyte developmental stages were divided into seven stages as chromatin nucleolar, early perinucleolar, late perinucleolar, cortical alveolar, vitellogenesis, mature oocyte and germinal vesicle migration stages. All the seven stages of oocyte development were observed in the ovaries. Oogonia were always present throughout the developmental stages. The ovaries had more than two stages of oocyte development. This is the first report on the mode of ovarian development of H. nemurus. These findings indicated that H. nemurus has asynchronous mode of ovarian development and is capable of spawning several times in a year under favourable conditions.

Dietary Lipid Levels Affect Growth and Fatty Acid Profiles of Malaysian Mahseer Tor tambroides

Abstract After protein, the second major essential macronutrient in fish diet is lipid. This study was conducted to determine the optimum level of dietary lipid for the best growth performance of juvenile Malaysian mahseer Tor tambroides. Four isonitrogenous diets containing 40% crude protein were formulated to contain different levels of lipid (5, 10, 15, or 20% on an as-fed basis). Cod liver oil was incorporated into the feed as the main dietary lipid source used to formulate the diets while residual oil coming from other ingredients contributed about 5% of dietary lipid. The experimental diets were labeled as L5, L10, L15, or L20 to denote the levels of dietary lipid. Fish were fed the experimental diets in triplicate groups for 63 d. Growth performance, survival rate, and daily feed intake by Malaysian mahseer significantly decreased when fed diets in which levels of dietary lipid increased from 5% to 20%. However, the growth performance did not vary significantly between fish fed the L5 and L10 diets...

Changes over time in muscle fatty acid composition of Malaysian mahseer, Tor tambroides , fed different dietary lipid percentage

The effects of four isonitrogenous diets containing different lipid levels on the muscle fatty acid profiles of Malaysian mahseer were evaluated over a period of six weeks from June to July, 2010. A general increase of monounsaturated fatty acid contents in the muscle of fish that were fed the test diets was detected after two weeks. Despite the high total content of long chain n-3 polyunsaturated fatty acid (PUFA) in the formulated diets, the levels of these fatty acids in the muscle did not increase and it may be speculated that the content of long chain n-3 PUFAs in this species was determined by desaturation and elongation of shorter chain fatty acids rather than direct absorption from the diet. Moreover, reduction of muscle n-3 PUFA content after six weeks of feeding showed that a diet containing high level of n-3 PUFA may not be able to provide all the essential fatty acid requirements of T. tambroides .