Mohd Azmi Ambak

A study on the optimal tank design and feed type to the growth of marble goby (Oxyeleotris marmorata Bleeker) and reduction of waste in a recirculating aquaponic system

AbstractMarble goby (Oxyeleotris marmorata Bleeker), a profitable aquaculture species, was cultured in partitioned tanks treated with a water recirculating aquaponic system (RAS). The influence of tank design (with partitions and PVC tubes of different sizes) and feed type (live food and minced fish) on the fish growth and waste production was investigated. The fish cultured in big partitions with PVC tubes showed higher growth (2.5 g/d) and feed intake (468 g/d) than other tank designs (growth: ⩽2.2 g/d; feed intake: ⩽433 g/d). The growth of fish fed with live tilapia (Oreochromis niloticus) (2.5 g/d) was significantly higher than that of fish fed with live carp (Cyprinus carpio) (1.9 g/d) and minced scads (Decapterus russellii) (1.6 g/d). Fish fed with minced scads showed the highest waste production (ammonia nitrogen (TAN): 262 mg/kg d; 5-d biochemical oxygen demand (BOD5): 434 mg DO/kg d; total suspended solid (TSS): 2.1 g/kg d) compared to those fed with live food (tilapia and carp) (TAN: ⩽208 mg/kg ...

Effect of Excoecaria agallocha on non-specific immune responses and disease resistance of Oreochromis niloticus against Streptococcus agalactiae

The current study was designed to evaluate the effects of Excoecaria agallocha leaf extracts on immune mechanisms and resistance of tilapia, Oreochromis niloticus, after challenge with Streptococcus agalactiae. Fish were divided into 6 groups; groups 1-5 fed with E. agallocha leaf extracts at 10, 20, 30, 40 and 50mgkg-1 level, respectively. Group 6 were fed without extract addition and acted as control. E. agallocha extracts were administered as feed supplement in fish diet for 28days and the hematological, immunological, and growth performance studies were conducted. Fish were infected with S. agalactiae at a dose of 15×105CFUmL-1 and the total white blood cell (WBC), phagocytosis and respiratory burst activities of leukocytes, serum bactericidal activity, lysozyme, total protein, albumin, and globulin levels were monitored and mortalities recorded for 15days post infection. Results revealed that feeding O. niloticus with 50mgkg-1 of E. agallocha enhanced WBC, phagocytic, respiratory burst, serum bactericidal and lysozyme activities on day 28 pre-challenge and on 3rd, 6th, 9th, 12th and 15th day post-challenge as compared to control. Total protein and albumin were not enhanced by E. agallocha diet. E. agallocha increased the survival of fish after challenge with S. agalactiae. The highest mortality rate (97%) was observed in control fish and the lowest mortality (27%) was observed with group fed with 50mgkg-1 extract. The results indicate that dietary intake of E. agallocha methanolic leaf extract in O. niloticus enhances the non-specific immunity and disease resistance against S. agalactiae pathogen.

Molecular identification and histopathological study of natural Streptococcus agalactiae infection in hybrid tilapia (Oreochromis niloticus)

Aim: The main objective of this study was to emphasize on histopathological examinations and molecular identification of Streptococcus agalactiae isolated from natural infections in hybrid tilapia (Oreochromis niloticus) in Temerloh Pahang, Malaysia, as well as to determine the susceptibility of the pathogen strains to various currently available antimicrobial agents. Materials and Methods: The diseased fishes were observed for variable clinical signs including fin hemorrhages, alterations in behavior associated with erratic swimming, exophthalmia, and mortality. Tissue samples from the eyes, brain, kidney, liver, and spleen were taken for bacterial isolation. Identification of S. agalactiae was screened by biochemical methods and confirmed by VITEK 2 and 16S rRNA gene sequencing. The antibiogram profiling of the isolate was tested against 18 standard antibiotics included nitrofurantoin, flumequine, florfenicol, amoxylin, doxycycline, oleandomycin, tetracycline, ampicillin, lincomycin, colistin sulfate, oxolinic acid, novobiocin, spiramycin, erythromycin, fosfomycin, neomycin, gentamycin, and polymyxin B. The histopathological analysis of eyes, brain, liver, kidney, and spleen was observed for abnormalities related to S. agalactiae infection. Results: The suspected colonies of S. agalactiae identified by biochemical methods was observed as Gram-positive chained cocci, β-hemolytic, and non-motile. The isolate was confirmed as S. agalactiae by VITEK 2 (99% similarity), reconfirmed by 16S rRNA gene sequencing (99% similarity) and deposited in GenBank with accession no. KT869025. The isolate was observed to be resistance to neomycin and gentamicin. The most consistent gross findings were marked hemorrhages, erosions of caudal fin, and exophthalmos. Microscopic examination confirmed the presence of marked congestion and infiltration of inflammatory cell in the eye, brain, kidney, liver, and spleen. Eye samples showed damage of the lens capsule, hyperemic and hemorrhagic choroid tissue, and retina hyperplasia accompanied with edema. Brain samples showed perivascular and pericellular edema and hemorrhages of the meninges. Kidney samples showed hemorrhage and thrombosis in the glomeruli and tubules along with atrophy in hematopoietic tissue. Liver samples showed congestion of the sinusoids and blood vessel, thrombosis of portal blood vessel, and vacuolar (fatty) degeneration of hepatocytes. Spleen samples showed large thrombus in the splenic blood vessel, multifocal hemosiderin deposition, congestion of blood vessels, and multifocal infiltration of macrophages. Conclusion: Therefore, it can be concluded that pathological changes in tissues and organs of fish occur proportionally to the pathogen invasion, and because of their high resistance, neomycin and gentamicin utilization in the prophylaxis or treatment of S. agalactiae infection should be avoided.

Evidence for sexual attraction pheromones released by male tropical donkey's ear abalone (Haliotis asinina), (L.)

Abstract The tropical donkeys ear abalone (Haliotis asinina) is routinely collected in many parts of the Indo-Pacific and has significant potential for commercial aquaculture. Although its reproductive cycle has been investigated, no studies have reported the use of chemical signals to coordinate reproduction and spawning. Using a bioassay designed with one caged individual, whilst the other is free to roam, we investigated the presence of attraction pheromones released from mature individuals. Only mature females were attracted to caged mature males with all other treatments showing no significant attraction. Those mature females also took significantly less time to reach the mature males than other pairings. Temperature influenced the response with the maximum number of positives occurring between 25 and 31°C, which coincides with the optimum physiological temperatures and the spawning times for this species. We have also shown that the attraction pheromone is present in mature male testes and induces stereotypical pre-spawning behaviours (sweeping epipodial and cephalic tentacles) as well as attracting females. Some individuals also moved towards the surface of the water, this may also be a pre-spawning behaviour. This is the first time that a sexual attraction pheromone has been reported for any haliotid species and is likely to have a critical function in the synchronization of spawning in the wild between sexes.

Effect of different diets on growth and survival rates of snakehead (channa striata bloch, 1797) larvae

A study was conducted to determine growth and survival rates of snakehead (Channa striata) larvae. Live foods such as Artemia salina naupiii, Moina micrura and bloodworm and artificial diet were given to larvae from 1–15 days after hatching as the 1st phase and from 15–30 days as the 2nd phase. In the 1st phase, the growth and survival rates of larvae fed with Artemia nauplii were significantly different from larvae fed with Moina (p<0.05) with values of 28.5 mg, 49% and 26.7 mg, 31%, respectively. Meanwhile, all larvae fed with bloodworm (Chironomus sp.) or artificial diet (49% protein) died within 10 days of experiment. For the 2nd phase, growth of the fry fed with Artemia or Moina differed significantly from that fed with bloodworm or pellet (200.1, 187.7, 109.6 and 8.2 mg, respectively). Specific growth rate (SGR) of larvae fed with Moina was higher than that of larvae fed with Artemia (17.9 and 17.4% day‐1 respectively) in the 1st phase. In the 2nd phase, SGRs of larvae fed with Artemia (12.7% day‐1) or Moina (11.5% day‐1) were significantly higher than those of larvae fed with bloodworm (8.3% day‐1) or dry diet (6.1% day‐1). Generally, Artemia and Moina were suitable food for snakehead larvae during the first month of their life, and artificial diet was much less acceptable and resulted in poor growth and survival.

Diversity and Abundance Fish Assemblages in the Setiu Wetlands, Terengganu, Malaysia

The sampling programme was conducted to determine the diversity and abundance in fish assemblages from June 2011 to July 2012 using gill and trawl nets and traps. A total of 13,132 individuals of fishes comprising 116 species and 50 families were recorded. Family Siganidae had the highest family abundance recorded with 43.0%. Siganus javus was determined as the most abundant species with a percentage value of 38.8%. Ninety species were caught and considered to be commercially valuable. Four species were recorded as vulnerable in the IUCN Red List, which were Hippocampus spinosissimus, Hippocampus trimaculatus , Himantura uarnak, and Pegasus laternarius; while Himantura walga, Favonigobius melanobranchus, Favonigobius rechei. Epinephelus coioides , and Epinephelus diachanthus were listed as near threatened. Overall values of diversity, richness and evenness indices were found to be 2.60, 12.12 and 0.55, respectively. Estimates from these indices were an indication of high fish species composition, richness, and evenness in the population of fishes in Setiu wetlands. It is recommended that government should gazette the Setiu Wetlands as a state park in Terengganu for future planning.

The hormone 17β-estradiol promotes feminization of juveniles protandrous hermaphrodite false clownfish (Amphiprion ocellaris)

Abstract The social structure of the false clownfish (Amphiprion ocellaris) typically consists of a pair of functional brooders within a population of individuals which remain as protandrous hermaphrodites usually incapable of breeding. This situation often hampers the commercial scale production of large numbers of clownfish offspring and broodstock. To enhance breeding outputs, protandrous hermaphrodites must be converted to functional brooders with a distinct sex prior to pairing and breeding. In this study, 17β-estradiol (E2) was used to feminize juveniles of A. ocellaris, with groups of fish incubated at 0.1, 0.2, and 0.4 mgL−1 E2 for 15 days. The gender was substantiated on the basis of gonad histological profiles after 15, 30, and 60 days, work that includes verification of the safety levels of this hormone used in this application. All the treatments employed induced feminization, as shown by histology profiles revealing degenerate male germ cells and testes tissues and several developed ovarian cells at different stages (oogonia, previtellogenic and vitellogenic) 30 days after E2 incubation. Conversely, gonad profiles of non-treated fish did not change. The gonads possessed both ovarian and testicular tissues, a typical characteristic indicating that the fish are still ambisexual. Although E2 was effective in promoting gonad maturation, incubation of fish in high concentrations adversely affected fish survival. Mortalities occurred when E2 exceeded 0.1 mgL−1. The latter concentration is considered the most appropriate level for inducing feminization and at the same time, maintaining the well-being of the organism.