Some aspects in early life stage of sand goby, Oxyeleotris marmoratus .

Larval sand goby were produced by controlled natural spawning. Fertilized eggs were incubated in an aquarium tank for hatching. Sampling of the newly-hatched larvae was done at 2-hour intervals, when 20 of them were randomly taken and preserved in 10% buffered formalin solution for later analysis to determine the time of final yolk absorption. Observation using a microscope revealed that newly hatched larvae were 2.39±0.12 mm in total length and had yolk sacs of 55.32±14.85 µm 3 volume. The yolk sacs were completely absorbed within 82 hr after hatching at a water temperature of 27.0-30.5 o C. Up until full mouth development (start of feeding), 2-hourly samplings of twenty newly hatched larvae were taken from the aquarium hatching tank for observation of the size of mouth opening. All the larvae had open mouths about 36 hr after hatching (2.86±0.97 mm TL), with the mouths measuring 332.29±17.76 µm in mouth height. The start-of-feeding experiments were carried out using a 15-liter aquarium (water volume 10 liters) containing 1000 larvae aged 1.5 days post-hatching (just before the mouth opened). They were fed with 1 Ph.D. (Aquaculture), Asst. Prof.

The complete mitochondrial genome of the snakeskin gourami, Trichopodus pectoralis (Regan 1910) (Teleostei: Osphronemidae)

We sequenced and assembled three whole mitogenome sequences of the commercially important snakeskin gourami Trichopodus pectoralis isolated from Malaysia (introduced), Viet Nam (native) and Thailand (native). The mitogenome length range from 16,397 to 16,420 bp. The final partitioned nucleotide alignment consists of 14,002 bp and supports the monophyly of the genus Trichopodus (95% ultrafast bootstrap support) with T. trichopterus forming a sister group with the members of T. pectoralis

Fish waste by-product in formulated diet for climbing perch, Anabas testudineus

An eight weeks experiment was conducted to investigate the effect of fish waste by-product (FWP) in formulated diet on growth, survival and feed utilization of climbing perch, Anabas testudineus. FWP composed mainly of visceral organ of fish, was hydrolyzed before testing in formulated diet. Three isoproteic (40%) and isolipidic (10%) diets, F0, F25 and F50, were tested: a control diet with 100% of fish meal (FM) and 0% FWP and two treatments formulated with 25% and 50% FWP inclusion, as a FM substitute. The experiment was conducted in a cemented tank where net cages were installed, each one stocked at 30 fish (initial body weight 0.86±0.10, mean±SD, n=270). Experimental diets were fed to fish in triplicate, twice daily, to apparent satiation. Fish fed with control F0 demonstrated significantly higher weight gain compared to other treatments (P0.05). Fatty acids content in fish fed with FWP showed no significant difference in saturated fatty acid (SFA), monounsaturated (MUFA) and polyunsaturated (PUFA) contents, compared with F0 (P>0.05). In conclusion, fish fed F0 demonstrated a higher growth performance. However, a FM replacement level up to 25% of FWP did not deteriorate the growth of A. testudineus and showed a specific growth rate similar to F0, demonstrating its potential as feed ingredient

Some reproductive biological aspects of gray-eel catfish, Plotosus canius Hamilton, 1822 spawner in Pattani Bay, Thailand

Reproductive biology of gray-eel catfish, Plotosus canius was studied at Pattani Bay by determining its year round changes of gonadosomatic index (GSI). Results show that the GSI was maximum in October (8.4 %), and minimum in April (0.24 %). The sampled size of sexually matured female fishes ranged from 40.9 to 60.5 cm in total length, and between 367.56 to 1,159.37 g in body weight. The average total length of the female fish is 51.9 cm, with an average body weight of 788.8 g. The average fecundity was 1,842.14 egg/fish. The average GSI was 10.87 % (n=14).The fish total length (TL) and body weight (BW) of the matured fish were linearly related, and could be represented by the linear regression as: BW = 32.295 TL – 887.52. The relationship between body weight (BW) and fecundity (Fe) could also be represented by the linear regression as Fe = 398.67+1.83BW. The eggs were adhesive demersal egg type, and rounded. The distribution of egg’s diameter could be categorized into five groups i.e. group1 (3.3%), group2 (6.9%), group3 (11.0%), group4 (54.1 %), and group5 (24.6 %), with values of 2.89± 0.19 mm, 3.44±0.36 mm, 4.65±0.28 mm, 5.65±0.26 mm, and 6.38±0.25 mm respectively. The spawning ground is made of silty clay soil, with sediment’s pH of 7.16±0.47and water salinity of 12.06 ± 0.78 ppt. We also found that the sperms activity was most active in the 0.9 % sodium chloride’s concentration level

Length-weight relationship and relative condition factor of the sultan fish, leptobarbus hoevenii broodstock farmed in earthen ponds

The present study was aimed to assess the general health condition of Sultan fish, Leptobarbus hoevenii broodstock through their length-weight relationship (LWR) and relative condition factor (RCF). This broodstock was poly-cultured with the other carp’s species in earthen ponds. Totally, 95 broodstock (35 females and 60 males) were examined in this study. The total length (cm) and body weight (g) ranges of the L. hoevenii broodstock were 32.8 – 43.0 cm and 460 – 1,400 g for the females, while 30.0 – 44.5 cm and 285 – 1,300 g for the males, respectively. The b value of the females was 3.10 (> 3.0), indicating that they have attained positive allometric growth. In opposite, the males and the overall populations have attained negative allometric growth as their b value was 2.66 and 2.92 (< 3.0), respectively. All of these LWRs were significant at α = 0.01 with their correlation coefficient (r) values at 0.88 - 0.90. However, the 95% confidence interval of these b values were in the range of 2.32 – 3.64; they included 3.0 and overlapped each other. This result showed that these b values were not significantly different, indicating that the fish has achieved ideal growth. In addition, the relative condition factors of both females and males have achieved more than 1 (1.04 and 1.01, respectively), indicating that they have achieved their expected weight. Further observation on the LWR of the male L. hoevenii broodstock from the wild is necessary to confirm its optimum b value. Overall, the b value of the broodstock was 2.92 (close to 3), and their RCF value was 0.98 (close to 1). Therefore, the broodstock can be considered in good health condition. However, the influence of poly-culture management on the LWR of this broodstock should be examined in future studies

Optimization of the cytogenetic protocol for Pangasianodon hypophthalmus (Sauvage, 1878) and Clarias gariepinus (Burchell, 1822)

To obtain well spread chromosomes, the cytogenetic protocol for Pangasianodon hypophthalmus and Clarias gariepinus were optimized. This includes, the colchicine concentration (0.01%, 0.025%, 0.05%)/exposure duration (1, 3, and 5 h), hypotonic solution (distilled water or 0.075M KCl solution)/exposure duration (30 min, 1, and 2 h), the time of cell suspension preparation (at hypotonic treatment or before slide preparation) and chromosome aging period (0, 3, and 7 days in Carnoy’s fixative). In addition, the type (i.e., fin, gill or kidney) and the amount of tissue (10, 50, 100 or 150 mg) were also investigated. Regardless of the species, the result obtained showed that well-spread chromosomes could be obtained using the following optimized protocol: Juveniles are injected with 0.05% colchicine (at one ml kg−1) and allowed to swim for 3 h. Then, 50 mg of gill tissue is made into cell suspension in 0.075M KCl for 1 h. The cell suspension is treated in Carnoy’s fixative (changed three times at 20 min interval) and then aged for 3 days. Finally, chromosome slides are made and stained with 10% Giemsa for 1 h

Observation on the embryonic development of Sultan fish, Leptobarbus hoevenii

Sultan fish, Leptobarbus hoevenii, is a popular freshwater fish species that is important to the aquaculture industry in some Southeast Asian countries, including Malaysia and Thailand. This study examined the embryonic development of L. hoevenii in order to fill in the biological knowledge gap and to provide a baseline information to fish farmers for the operations of mass seed production. The fertilized egg of L. hoevenii was obtained through natural spawning with the aid of hormones injection. Egg specimens were sampled randomly for the embryonic development examination. At a water temperature of about 28˚C, the egg fertilization ratio was 85.4%. The egg developed through the cleavage period, morula and gastrula stages, the segmentation periods, and the complete embryo formed at 18 hrs 11 minutes after fertilization (AF); some newly hatched were already seen at this stage. The egg hatching event completed at 22 hrs and 44 minutes AF, and the egg hatching ratio was 87%. Evaluation of the impacts of the water parameters (including temperature), ambient (e.g. water flow and lighting) and broodstock conditions (e.g. age and nutritional status) on the embryonic development duration in L. hoevenii is recommended for future studies

Vision-mediated feeding behaviour of early juvenile Sultan fish, Leptobarbus hoevenii

The Sultan fish, or ‘Jelawat’, Leptobarbus hoevenii is a cyprinid with a natural distribution in streams, rivers and lakes of some Southeast Asian countries, including Malaysia and Thailand (Mohsin & Ambak, 1983; Vidthayanon et al., 1997). It has value as a freshwater food fish (Mohsin & Ambak, 1983; Roberts, 1989), and its flesh is rich in protein, vitamin B and minerals (Tee et al., 1989). The Sultan fish has been introduced into several countries, including Taiwan and China, for aquaculture and as an ornamental species (Liao et al., 2001; Xiong et al., 2015). Captive breeding, seed production and farming techniques of this fish have been established (Liao et al., 2001; Meenakarn, 1986; Saidin et al., 1988; Truong et al., 2003), and there is information available about its feeding and nutritional requirements (Au et al., 2020). However, the major sensory modalities used by L. hoevenii at early life-history stages to detect prey are still unknown

Reproductive characteristics of the pond-farmed Sultan fish (Leptobarbus hoevenii)

Sultan fish (Leptobarbus hoevenii) is a high value freshwater fish, cultured in some Southeast Asian countries, including Malaysia and Thailand. However, information on its reproductive characteristics is very scarce. This study examined the gonadosomatic index (GSI), fecundity, egg diameter, and determined whether L. hoevenii is a single-or multiple-spawner. Twenty male and female pond-farmed L. hoevenii broodstock were obtained to measure their total length (TL), body weight (BW), and gonad weight to calculate the GSI. Ten females were randomly sampled from the 20 to determine their fecundity. A total of 1,500 eggs were sampled from each female. The egg diameter was measured then its frequency distribution was analyzed to detect the number of egg class group, and to determine whether L. hoevenii is a single-or multiple spawner. The female L. hoevenii examined were 32.2-47.1 cm and 350-1,200 g, while the males were 30.7-45.8 cm and 180-970 g in TL and BW, respectively. All female specimens contained gonads. The potentially smallest mature samples were recorded at 350 g (female) and 180 g (male). GSI for the female and male L. hoevenii were 1.81-12.28 % and 1.03-5.09 %, respectively. The fecundity was 35,467-128,067 eggs, while the highest fecundity was observed in a 1,000 g fish. The observed egg diameter ranged from 500 to 1,855 μm. Two to five groups of egg class were detected, indicating that L. hoevenii is a multiple spawner

Some aspects in early life stage of giant gourami, Osphronemus gouramy (Lacepede) larvae

Abstract The sexual maturity of female giant gourami, Osphronemus goramy was studied by determining fecundity and gonadosomatic index (GSI). It was found that the size at sexual maturity of female giant gourami was with 33.88±7.42 cm in total length and 968.75± 68.78 g in body weight. Fecundity was 5,508±1,547 ova/fish and gonadosomatic index (GSI) was 2.32±0.5%. Newly hatched larvae of giant gourami were produced by semi-control natural method. The hatching period, hatching out and hatching rate experiments were carried out in a 15-liter glass aquarium (water volume 10 liters) containing 300 eggs. It was found that the eggs were floating and rounded. The fertilized eggs had a diameter of 2.185±0.19 mm. The average hatching out was 26 hr 18 min, hatching period was 6 hr 13 min and hatching rate was 61.60% at water temperature of 28-30° C. The newly hatched larvae were 4.48±1.41 mm in total length with yolk sac of 7.768.72±1.205.83 µm 3 in volume. The yolk sacs were completely absorbed within 228 hr after hatching. All the larvae opened their mouth at about 50 hr after hatching (6.87±0.10 mm TL) with mouth measuring 324.30±144.60 µm in height. Feeding experiments was carried out in 15-liter glass aquarium with 10 liters of water containing 1000 larvae aged 1.5 days post-hatching (before mouth opening. Moina was fed to them at a density of 10 individual/ml. At 2-hourly intervals 20 larvae were collected randomly from the aquarium, preserved in 10% formalin and then dissected to determine Moina in the digestive tract. At 110 hr after hatching, the mouth size was measured to be 486.45±14.47 µm. The onset of feeding showed 0.27 individual Moina/ larvae