Studied were the length-weight relationships (LWRs) and condition factors of two threatened species, Rasbora tawarensis and Poropuntius tawarensis, endemic to Lake Laut Tawar. The objective of the present study was to establish baseline data on LWRs of the two endemic fishes. The growth pattern for both species was predicted using a Linear Allometric Model (LAM) of length-weight relationship and FultonÕs condition factor (K TL ) as well as Relative Weight (W r ). The b value of R. tawarensis was relatively similar between females and males, while the b value of female P. tawarensis was slightly higher than in males. Nevertheless, both R. tawarensis and P. tawarensis showed an allometric negative growth pattern. The average K TL value of R. tawarensis was 1.85 and 1.73 for females and males, respectively, while P. tawarensis had values of 2.44 and 2.41 for females and males, respectively. In addition, the average W r values of R. tawarensis were 98.9 and 100.45 for females and males respectively, while 102.30 for female and 102.96 for male P. tawarensis, indicating that the condition factors of P. tawarensis were higher than in R. tawarensis.

Toxicity is a major limitation to successful spermatozoa cryopreservation of fish. Due to this problem, it is critical to find potential cryoprotectants which are more environmental-friendly, non-toxic, easily prepared, and available at affordable prices. Hence, the objective of the present study was to investigate several natural cryoprotectants for optimal cryopreservation of the African catfish, Clarias gariepinus, Burchell 1822 (Pisces: Clariidae) spermatozoa. Three natural cryoprotectants were tested -egg yolk, glucose, and honey, while DMSO was used as a control at different concentrations (5, 10, and 15%). Sperms were diluted with coconut water at a dilution level of 1 : 20 sperm to extender (v/v). Diluted sperms were kept at 4°C for 5 min, then at 0, -4, and -79°C for 5 min respectively, and stored in liquid nitrogen (-196°C) for 45 days. The cryopreserved sperms were thawed in a water bath (37°C) for 5 min and evaluated for fertilization and hatching rates. The data were subjected to analysis of variance (ANOVA), followed by comparison of means using Duncan's Multiple Range Test. The fertilization and hatching rates of African catfish in all cryoprotectants improved with concentration increasing from 5 to 10% but then decreased when concentration was increased to 15%. The ANOVA test showed that the differences in cryoprotectants used significantly affected fertilization and hatching rates of African catfish. Overall, the fertilization and hatching rates were higher in DMSO for all concentrations compared to other cryoprotectants. However, 10% egg yolk resulted in higher fertilization and hatching rates compared to other natural cryoprotectants. It was concluded that 10% egg yolk was the most suitable concentration for African catfish spermatozoa cryopreservation compared to other natural cryoprotectants tested.

BackgroundRasbora tawarensis is an endemic freshwater fish in Lake Laut Tawar, Aceh Province, Indonesia. Unfortunately, its status is regarded as critical endangered with populations decreasing in recent years. To date no information on the spawning activities of the fish are available. Therefore, this study provides a contribution to the knowledge on reproductive biology of R. tawarensis especially on spawning seasons as well as basic information for conservation of the species.MethodsMonthly sampling was conducted from April 2008 to March 2009 by using selective gillnets. The gonadosomatic index, size composition and sex ratio were assessed. The gonadal development was evaluated based on macroscopic and microscopic examinations of the gonads.ResultsThe gonadosomatic index (GSI) varied between 6.65 to 18.16 in female and 4.94 to 8.56 for male. GSI of the female R. tawarensis was higher in March, September and December indicating the onset of reproductive seasons, the GSI and oocyte size being directly correlated with gonadal development stages. Although, a greater proportion of mature male than female was detected during the study, the sex ratio showed that the overall number of female was higher than male. The ovaries had multiple oocyte size classes at every stage of gonadal development, thus R. tawarensis can be classified as a group synchronous spawner or a fractional multiple spawner.ConclusionThe spawning seasons of R. tawarensis were three times a year and September being the peak of the reproductive season and the female was the predominant sex. This species is classified as a group synchronous spawner.

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The objective of the present study was to describe the aspects of feeding habit and lengthweight relationship of keureling fish Tor tambra, this information is crucial to plan a conservation startegy for this species. A series of samples were taken between June and September 2012 and February 2014 in the two main rivers of western Aceh i.e. the Sikundo and Nagan Rivers. A total of 48 and 38 fish were caught during the study in Nagan and Sikundo Rivers, respectively. Stomach content analysis suggested that freshwater green algae and earthworms were the main food items for T. tambra, indicating an omnivorous feeding habit. In addition, the length-weight relationship revealed that T. tambra has an allometric negative growth pattern from all populations, and the condition factors indicate the rivers are still in good condition and support fish life.

The objective of the present study was to determine the optimum dosage of vitamin E (alpha-tocopherol) in the diet of keureling, Tor tambra (Val.) fingerlings for optimal growth performance and feed utilization. Five doses of vitamin E were tested: 0 mg kg−1 feed (control); 150 mg kg−1 feed; 300 mg kg−1 feed; 450 mg kg−1 feed; 600 mg kg−1. The feed ratio was 5% body weight, which was delivered twice daily at 08:00 and 17:00 for 60 days. The results showed that higher growth performance, feeding conversion ratios, feed efficiency, protein retention, and protein digestibility were obtained at 600 mg kg−1 feed, but the value was not significantly different from the other doses. The optimal dose in terms of the hepatosomatic index and survival rate was 300 mg kg−1. Hence, it was concluded that the optimum, most economical dose of vitamin E supplement for keureling (T. tambra) was 150 mg kg−1 feed, because this value was not significantly different from the doses of 300 and 600 mg kg−1 feed.

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Background The objective of the present study was to evaluate the growth performance and feed utilization of African catfish Clarias gariepinus fed a commercial diet and reared in the biofloc system enhanced with probiotic. Methods The treatment was the frequency of probiotic application into the cultured system, namely, 5-day interval, 10-day interval, and 15-day interval for 60 days of experiment. Biofloc culture was grown in an experiment tank (vol. 2000 L) by mixing the probiotic ( Bacillus sp.) 10 mL and molasses 200 mL per liter of water.  The fish was stocked into the biofloc system 7 days after cultured at stocking density of 1000 fish tank -1.  The fish was fed a commercial diet that contains 38% crude protein, twice a day at satiation. The application of probiotic was reperformed after 5 days, 10 days, and 15 days after stocking. Results The study showed that the growth performance, survival, and feed utilization of African catfish were higher in the treatment at 5-day intervals over 60 days. The ANOVA test showed that the application frequency of probiotic into biofloc system of cultured media had the significant effect on the growth performance, survival rate, and feed utilization of African catfish. Conclusion The best growth performance and feed utilization were  found at the application of probiotic into biofloc system at 5-day intervals over 60 days.