Aquarium Fish Research Articles

Winter leaves Alaskan blackfish breathless

Most fish breathe water with their gills, but a surprising number of fish can inhale air directly. Even common household pets such as Siamese fighting fish (betta fish, Betta splendens) breathe at the surface, so they can live in tiny bowls without filters or aeration. The Alaskan blackfish (Dallia pectoralis) shares this superpower. A modified esophagus lets them ‘surface breathe’, so they can get oxygen even in the stagnant and muddy waters that pepper the Arctic tundra. Most of the year, this ability gives blackfish a great advantage – they can live where most fish cannot, in a niche of their own. But in the winter, blackfish can no longer breathe air. The rough Alaskan winters bring ice and snow, which cover the water surface and lock out fresh air. Yet even after losing access to oxygen, blackfish remain active throughout the long winter season. For Gina Galli (University of Manchester, UK) and a team led by Jonathan Stecyk (University of Alaska Fairbanks, USA), this was a fascinating question. How can an animal survive for a whole season without air?To investigate, the team visited Palmer, Alaska, in the summer and caught blackfish with a minnow trap. Back in the lab, they housed the fish in aquaria and mimicked the conditions they would experience in the wild: over several weeks, they reduced the temperature to 5°C and reduced dissolved oxygen levels in the water. They also installed a grate just underneath the water surface to simulate the arrival of snow and stop the fish from breathing air. Then, they collected mitochondria – which are ideal to understand how oxygen is used, because they use oxygen to make energy – from the blackfish and analyzed how they were using oxygen. Do blackfish mitochondria work overtime to keep cells energized throughout the winter? It’s not unheard of, and Stecyk’s team noted that as many fish species acclimate to the cold, their mitochondria become more productive.But it turned out that cool temperatures did not energize blackfish. Their mitochondria didn’t fight any harder for oxygen. Likewise, they had the same appetite for a chemical needed to make energy (adenosine diphosphate, ADP), which means they weren’t making extra energy or working more efficiently. Unfazed, the blackfish mitochondria just chugged along at the same tempo.So, why don’t blackfish fight harder for oxygen? Stecyk’s team pointed out that although breathing sustains life, oxygen has a dark side. In any cell that consumes oxygen, a fraction of that oxygen creates toxic byproducts, called reactive oxygen species, which can damage mitochondria and kill cells. The researchers measured the reactive oxygen species produced by blackfish mitochondria using a fluorescent dye. In most species, cells produce more harmful reactive oxygen species when the temperature falls and oxygen is low – the exact conditions experienced by blackfish while breathless during Alaskan winters. Yet Stecyk’s team found the opposite: the blackfish produced fewer reactive oxygen species in the cold and fewer still when oxygen was low. This means the cold Alaskan winters prepare the blackfish to protect themselves from the damaging effects of low temperatures and oxygen levels, preconditioning them so they can hold their breath all season long.It’s fascinating enough that a fish can breathe air. But blackfish take it a step further: they hold their breath for an entire season. Many animals pant, gasp and struggle to get more oxygen when they can’t breathe, but blackfish don’t struggle. Their mitochondria maintain their pace, yet they work ‘cleaner’ to avoid polluting cells with toxic oxygen byproducts. In this way, they’re like a seasoned marathon runner: they don’t foolishly sprint when the race starts, they just maintain their pace and watch their form.

Occurrence of South American sucker armoured catfish (Pterygoplichthys pardalis) in the Gayathripuzha River, Palakkad, Kerala

An intensive survey was undertaken and reported the existence of an invasive armoured sailfin catfish Pterygoplichthys pardalis from the Bharathapuzha River, Palakkad, Kerala, India, and its invasion as one of the foremost threats to the endemic aquatic biodiversity of Kerala. It belongs to the Genus Pterygoplichthys (Siluriformes: Loricariidae) which is known as popular aquarium fish that constitutes one of the most successful aquatic freshwaters invasive taxa, having achieved global distribution. The invasion occurred through aquarium fish culture and trading and is intensified by the distribution through rainstorm flooding and irrigation canal. The fish were identified based on morphological tests, identified fishes ranged in length (9.50-31.75cm) and weight (8.16-129.80 g). Distribution leads to understanding the changes and disturbances in fish species composition and the negative impact on the riverine ecosystem.

Comparative assessment of the U.S. State of Florida’s Marine Life regulations for its commercial marine aquarium fish fishery

Governments in select locales around the world have recently either restricted or closed commercial marine aquarium fisheries, impacting the livelihoods of fishers, traders, and others who depend on them. This paper offers an objective assessment of Florida's commercial marine aquarium fish fishery and its regulatory landscape to inform and guide stakeholders about management strategies for the fishery moving forward, and to highlight successful regulations in place in Florida that merit consideration for adoption in other source locales around the world. The study discovered that the State has a strong regulatory structure for the commercial fishery operated by the Florida Fish and Wildlife Conservation Commission; practicing co-management with fishers, and utilizing license and permitting requirements, conventional fisheries management measures and technical actions to regulate fishing mortality, and rights-based management approaches. Additionally, both fisheries-independent and dependent surveys have been conducted in recent years to assess the fishery. Consequently, the vast majority of fish species collected commercially for the trade indicate stable or increasing catch trends in Florida waters over 10 + years. Moving forward, the fishery can benefit from an assessment of the economic impacts of the regulatory framework on its fishers, a statewide fisheries management plan specific for the fishery, the further development of a comprehensive program for fisheries data collection and analysis to address data gaps, an assessment of resources at hand and those needed to implement these recommendations, and the elevation of marine aquarium fisheries for support at the national level to support state-level management.

Slow-Release Lanthanum Effectively Reduces Phosphate in Eutrophic Ponds without Accumulating in Fish

Nutrient runoff is a major water quality issue affecting water resources. Excess nutrients such as nitrate (NO3−) and phosphate (PO43−) entering surface waters promote eutrophication. Recent research showed that floating treatment wetlands combined with slow-release lanthanum composites deployed through airlift pumps can reduce NO3− and PO43− concentrations, minimize algae and weeds, and increase dissolved oxygen concentrations. While water quality improves following this biological and chemical approach, questions remain about the toxicity and potential accumulation of lanthanum in lentic organisms. We addressed this concern by analyzing flesh and liver of fish exposed to the slow-release lanthanum following two years of treatment and compared results to fish harvested from a control, untreated pond. We also conducted an aquarium fish study that used higher lanthanum concentrations than those observed in the field. The field study confirmed that under the concentrations of lanthanum released to treat eutrophic ponds (109 µg L−1), no adverse effects were observed in harvested fish. We also observed no significant differences between lanthanum-exposed and -unexposed fish (α = 0.05) in our controlled tank study. Given the laboratory tank lanthanum concentrations were approximately nine times higher (916 µg L−1) than the observed field concentrations, we conclude the slow-release lanthanum composites used to treat eutrophic ponds are effective in improving water quality and do not lead to significant lanthanum accumulation in fish.

Use of sorption premixes in fish farming as a prevention of nutritional toxicosis

Climate change is a fact with serious implications that extend to pollution, seafood safety and global food security.The studies were carried out in 2022, on the basis of the FGBOU HE SPbGUVM. Guppy aquarium fish were taken as objects of exploratory research. In the amount of 45 pieces. All objects were placed in the same habitat conditions: 3 aquariums of 10 liters each, males were selected, 10 pcs each. Three groups were created: the first group was given acetate as a lead toxicant, at the rate of 1g/10l, which is 10 times higher than the MPC, which is 0.1g/l according to existing regulations. The second group was given a toxicant in an equivalent dose and a sorption complex (vermiculite, perlite and polyphepan) at the rate of 4% of the daily norm, the control group remained free of toxicants and premix.The toxicant was given once, the sorption complex for a month, crushed and mixed with the feed beforehand. Feeding was carried out with specialized Tetra food. After 30 days. guppy tissue and organ samples were sent to the laboratory of the Educational and Research Center for the Expertise of Food Products and Feed for Animals (FGBOU VO SPbGUVM, St. Petersburg). A study on the detection of lead in tissues and organs was carried out by atomic absorption spectrometry M 04-64-2017, using an atomic absorption spectrometer with electrical atomization MGA-915.According to our exploratory studies, the premix dose of 4% allowed to reduce the amount of toxins by almost three times under equal conditions. Thus, this complex of sorbents can be used as a prevention of altimentary toxicosis with lead acetate in aquarium fish, and also that a premix of sorbents can be recommended for use in fisheries after industrial testing.

Perspectives for Exploitation of Sabella spallanzanii’s Biomass as a New Integrated Multi-Trophic Aquaculture (IMTA) By-Product: Feeding Trial on Amphiprion ocellaris Using Sabella Meal

This paper is part of a series of studies aimed at understanding the potential exploitation of the biomass of the polychaete worm Sabella spallanzanii (Gmelin, 1791), which is obtained as a by-product of an innovative Integrated Multi-Trophic Aquaculture (IMTA) system. IMTA systems are designed according to an ecosystem approach with the aim to reduce marine monoculture impact while further increasing production via exploitation of valuable by-products. S. spallanzanii can remove large amounts of suspended matter by filtering large volumes of water per hour and performs well as an extractive organism under IMTA; however, it currently lacks any economic value, thus hindering its sustainable large-scale implementation. However, S. spallazanii has the potential to become competitive as a newcomer in fish bait, as an ornamental organism, and in fish feed markets. Notably, sabella meal has already been successfully tested as an attractant in an innovative fish feed. Here, we refer to the use of sabella meal as the main component (60%) in the formulation of a novel aquarium fish feed. Following the biochemical analysis of farmed sabella meal, the experimental feed was formulated by adding spirulina (25%) and dry garlic (15%) in such proportion as to be isoproteic and isoenergetic to the commercial control feed. After preliminary observations of the palatability of sabella meal for several tropical fish species, the novel experimental feed was tested on ocellaris clownfish, Amphiprion ocellaris (Cuvier, 1830), by evaluating their growth response in a 70-day feeding trial. The fish seemed to enjoy the experimental feed at least as much as the control, and both the control and treatment groups showed no significant differences in weight gain (p = 0.46), specific growth rate (p = 0.76), and feed conversion ratio (p = 0.48), reinforcing the suitability of S. spallanzanii as a viable source of animal proteins to be employed in the fish feed industry in a circular economy perspective.

Tilapia Nilotica Welfare in Relation to Economic and Managerial Culture

The aim of this study was to investigate the impact of different stocking populations of tilapia nilotica fish in their aquaculture on some maintenance behavior, performance, economic values and hormonal concentration levels. On this research, 300 tilapia nilotica fish were distributed into different densities (15, 20,25 and30 fish per aquaria 40*30*80cm) 3 replica for each population and distributed in 70 Litter water in aquaria. 30 fish kept as aspare. After 2 weeks from the start of the experiment and at the end of the experimental periods, blood samples were collected for serum cortisol and growth hormones assay. From the obtained results we found that, The feeding and foraging behavior time and frequency (94.00+3.55 & 144.00+9.79) were improved with stocking density (15 fish in aquaria) and the aggressive behavior was at high level with overcrowding. (26.80+1.83 & 105.00+4.68), on the other hand the surfacing, swimming and resting time were increased with higher stocking rate. The growth hormone was increased with decreased stocking density. The stress indicating hormone (cortisol) was increased with high stocking populations. The return and profit were significantly increase with decreased stocking density.

Primeiro registro da espécie exótica, plati Xiphophorus maculatus (Günther, 1866), na área de inundação urbana de um rio neotropical brasileiro

Abstract: Aim This work reports the first occurrence of the exotic species Xiphophorus maculatus (Günther, 1866) in the Sorocaba River Basin. The introduction of non-native fish species has become common and many species have been introduced mainly through sport fishing, aquaculture and aquarium keeping. In the case of the Poeciliidae, most of the introduced species that have been recorded come aquarium keeping. The environment where the specimens were captured had a large number of macrophytes due to anthropization and is located in a strictly urbanized area of the municipality. Methods The collection was done through a rectangular dip net, with measures of 70 cm x 60 cm and a mesh of 1 mm. The specimens were anesthetized in eugenol solution, fixed in 10% formalin solution and preserved in 70% alcohol. The specimens were later deposited in a scientific collection. Results The record includes two female specimens from an urban wetland on the Sorocaba River, São Paulo State, Brazil. Conclusions In the municipality of Sorocaba, 63 species of fish have already been identified, belonging to 7 orders and 19 families and 6 are exotic, such as the Xiphophorus maculatus. Urban floodplains are poorly studied environments, thus presenting great potential for the occurrence of species that have not yet been inventoried. The monitoring and inventory of exotic species must be carried out systematically so that mitigating measures can be proposed in relation to the control of these species, and this is one of the major causes of biodiversity loss. In addition, developing a program for returning unwanted fish to aquarium stores can be effective in preventing the introduction of new aquarium fish and displaying warnings informing of the negative ecological effects of releasing aquarium fish in all bags, fish plastics, and aquarium store websites.

Growing aquarium fish on organic food objects

The dependence of the cultivation of predatory aquarium fish on the use of live food in the diet as an organic food object in the aquaterrarium of the Roev Ruchey Park in the city of Krasnoyarsk was studied. When choosing an organic food object for growing ornamental fish, guppies and swordtail fish of the Pecilia family were considered. Their diet consisted of a combination food and meat mix for freshwater fish. Swordtails gave offspring more than guppies by almost 2 times, puberty came 1 week earlier, the life cycle is longer by 2 years. Brilliant cichlazomas of the studied groups received a combined feed in the diet, the fish of the control group were additionally fed a meat mixture for freshwater fish, in the experimental group this mixture and part of the combined feed were replaced with organic food objects - swordtails in the amount of 0.75 g/head per day.

Costs of parthenogenesis on growth and longevity in ex situ zebra sharks Stegostoma tigrinum

The zebra shark Stegostoma tigrinum, a popular aquarium fish, is an endangered species that is known to readily reproduce both sexually and through facultative parthenogenesis while in human care. Artificial insemination trials that took place between 2011 and 2013 resulted in the hatching of 2 sexually produced (herein heterozygotes) and 10 parthenogenetic sharks that allowed for a retrospective comparison of growth, feeding and longevity between offspring produced from 2 distinct reproductive modes. Parthenogenetic offspring were generally smaller at hatch than their heterozygous counterparts and, after the first several months post-hatch, failed to increase in mass and length at the same rate as heterozygotes. Parthenogenetic offspring exhibited non-normal swimming behaviors such as spiraling, spy hopping and head standing, which may have been correlated with a gradual decline in the ability of some sharks to properly suction feed. Median lifespan for the parthenotes was 1.05 yr (range: 0.27-6.64 yr); one of the heterozygotes lived to 2.37 yr of age, and the other was alive at the time of this writing in August 2022 and had reached reproductive maturity. By contrast, the 2 longest surviving parthenotes perished just prior to reaching sexual maturity (~5.5 and ~6.5 yr). Parthenogenesis has been documented among ex situ S. tigrinum maintained in aquariums across the globe, and this study demonstrates substantial negative costs to fitness in parthenogenetic offspring compared with their heterozygous siblings. The reduced fitness of parthenotes has implications for managing populations in human care as well as for in situ conservation efforts.

관상용 금붕어(Carassius auratus)의 비결핵항산균 감염증에 관한 고찰

In October 2021, goldfish (Carassius auratus) that reared in an aquarium continued to die and the cause analysis has begun. For diagnosis, biological, molecular and histopathological analysis were conducted, and samples are divided with symptomatic and asymptomatic objects. The 16s rRNA target region was identified from tissue (kidney+spleen) sample of asymptomatic fish, and the sequenced result shown 100% homology with Mycobacterium fortuitum. In histopathological studies, various size of granuloma and inflammatory regions are observed in kidney tissue of all tested fish, and acid-fast bacteria staining positive reactions are observed inside or outside the granuloma. In order to diagnose mycobacteriosis, accurate preparation is required along with various diagnostic methods, and more attention is needed in handling aquarium fish management to prevent mycobacteriosis.

Ocular pathology in aquarium fish with a focus on the Syngnathidae and Apogonidae families

This study catalogued ocular pathology in fish histopathology submissions to a specialist diagnostic service and investigated associations with species and systemic disease, with a focus on species of conservation interest. Cross-tabulations and Fisher's exact tests were used to identify associations among the variables and results are reported as prevalence ratios (PRs) with 95% confidence intervals (CI). Of 12,488 reports reviewed, ocular histology examination was available for 4,572 submissions, in which histopathological ocular lesions were identified in 18% (813/4572). Most diagnoses (701/813; 87%) were in marine fish. Inflammatory conditions were most common (608/813; 75%), with identification of a bacterial aetiology in 42% (255/608) and a parasitic aetiology in 30% (183/608). Most bacterial infections were due to mycobacteriosis (153/255; 60%) and most parasitic infections were due to scuticociliatosis (114/184; 62%). The Syngnathidae, Centriscidae and Cichlidae families were each more likely than all other families combined to be diagnosed with ocular manifestations of mycobacteriosis (PRs=2.6, 4.4 and 2.9, respectively, P<0.0001 for each). The Syngnathidae were also more likely to be diagnosed with ocular scuticociliatosis (PR=1.9, P<0.0001). Fifty-four percent (39/72) of ocular mycobacteriosis and 38% (9/24) of gas bubble disease cases affected threatened or near threatened Syngnathidae species. The Apogonidae were more likely than any other family to have ocular iridovirus (PR=10.3, 95% CI=5.5-19.4, P<0.0001) and neoplasia (PR=8.2, 95% CI=4.2-16.3, P<0.0001). The endangered Banggai cardinalfish (Pterapogon kauderni) accounted for 13/15 ocular iridovirus and 16/18 mycobacteriosis cases in this family. All cases of neoplasia in the Apogonidae occurred in pajama cardinalfish (Sphaeramia nematoptera). These results should inform clinical diagnosis of ocular disease in aquarium fish and influence training for aquarists, highlighting ocular pathology as a potential early warning of systemic disease. The findings also have direct/indirect consequences for the welfare and conservation of some of these popular flagship fish species.

Identification of sex-linked marker and candidate sex determination gene in ornamental fish, African scat (Scatophagus tetracanthus)

The aquarium industry greatly threatens biological diversity via biological invasion. Mono-sex culturing is an important technique to reduce the possible biological invasion introduced by the aquarium fish, which escape into their non-native environment. African scat (Scatophagus tetracanthus) is a valuable aquarium fish species worldwide. Herein, its sex-linked marker and candidate sex determination (SD) gene were identified through genome sequencing. The whole genome of the male African scat was sequenced using the next-generation sequencing technology. The assembled genome is 630.96 Mb with a scaffold N50 of 38,217 bp. Phylogenetic analysis revealed that African scat diverged from spotted scat (S. argus) approximately 10.5 million years ago. One sex-linked marker (Marker-1) was detected in African scat. Marker-1 amplified a single band of 873 bp in female African scat, and double bands of 873 bp and specific 772 bp in male African scat. Next, Marker-1 was validated in 60 cultured African scat with 100% consistency. Sequence analysis revealed that the 873 and 772 bp fragments were both Dmrt1 homologous sequences. These results imply that the African scat possesses the XY sex-determination system (XX females, XY males), with Dmrt1 as its sex-linked gene. Dmrt1 cDNA sequences on the X and Y chromosomes were also cloned and labeled as Dmrt1∆X and Dmrt1Y, respectively. The amino acid (aa) sequences coded by Dmrt1∆X and Dmrt1Y were 143 aa and 300 aa, respectively. Dmrt1Y mRNA was specifically expressed in the testis, with no expression in the ovary. Therefore, Dmrt1Y is male-specific and a candidate SD gene. The genome data and sex-linked marker of African scat will be helpful for its commercial management to prevent its biological invasion. Besides, the identification of its candidate SD gene contributes to the basic research of SD in vertebrates.

Characterizing the gastrointestinal development and digestive enzyme ontogeny of larval Amphiprion ocellaris

Clownfish (Amphiprion ocellaris) are the most recognizable and popular marine aquarium fish and are a key commodity for marine ornamental fish producers. Although these fish have been raised in captivity for decades, producers are still experiencing issues regarding larval survival, reliance on live feeds, and post-larval deformities. To improve the culture process, the ontogeny of larval development and digestive capacity should be elucidated. The morphological development, digestive enzyme ontogeny, and digestive tract development of A. ocellaris was examined in a 16-day trial. Standard microplate assays were conducted to quantify the activity of trypsin, lipase, and acid protease enzymes from 24 h before hatching to 15 days post hatch (DPH). Histology was used to visualize morphological changes in the digestive tract throughout the larval period. At hatching, A. ocellaris has functional eyes, an open mouth, and a coiled, differentiated digestive tract. Trypsin and lipase activities were detectable before hatching and increased significantly later in the larval period. Gastric gland formation was observed at 6 DPH, with stomach functionality occurring between 7 and 9 DPH, indicated by gastric gland proliferation and an increase in acid protease activity. The results from this study may be used to inform weaning protocols to maximize larval growth and survival while minimizing the use of costly live feeds.

Prevalence of fish lice, Argulus (Crustacea: Branchiura) in freshwater and two ornamental fishes of Iran

Farming and trading of aquarium fish has been considered a popular pastime in the world. Most of Iran's aquarium fish are imported from Asian countries including Indonesia, Malaysia, Thailand and Vietnam. Fish lice (Argulus) is known as one of the most important and common ectoparasites in ornamental fish. Reports indicate that these parasites have been observed in ornamental fish imported to Iran (e.g goldfish Carassius auratus and koi carp Cyprinus carpio). Today, due to mismanagement of some ornamental fish breeding centres in Iran, aquarium fish species such as goldfish may have escaped into the natural waters which increase the risk of transmitting pathogens to native fish. The present work was performed to investigate the outbreak of an ectoparasite Argulus in two ornamental fish of Iran and also to evaluate the possibility of transmission of Argulus to inland freshwater fishes of Iran.

Identification of candidate sex-specific genomic regions in male and female Asian arowana genomes.

BackgroundAsian arowana, Scleropages formosus, is one of the most expensive aquarium fish species worldwide. Its sex, however, cannot be distinguished clearly at any development stage, which impedes captive breeding and species protection for this endangered aquarium fish.ResultsTo discover molecular clues to the sex of Asian arowana, we sequenced 26.5 Gb of PacBio HiFi reads and 179.2 Gb of Hi-C reads for 1 male fish and also sequenced 106.5 Gb of Illumina reads, 36.0 Gb of PacBio Sequel reads, and 80.7 Gb of Hi-C reads for 1 female individual. The final male and female genome assemblies were approximately 756.8 Mb and 781.5 Mb in length and contained 25,262 and 25,328 protein-coding genes, respectively. We also resequenced the genomes of 15 male and 15 female individuals with approximately 722.1 Gb of Illumina reads. A genome-wide association study identified several potentially divergent regions between male and female individuals. In these regions, cd48 and cfap52 could be candidate genes for sex determination of Asian arowana. We also found some structural variations in few chromosomes between male and female individuals.ConclusionWe provided an improved reference genome assembly of female arowana and generated the first sequenced genome of 1 male individual. These valuable genetic resources and resequencing data may improve global aquarium fish research.

Simulating cyanide fishing: photosynthetic effects of short-term cyanide exposure in three different hermatypic coral species

ABSTRACT Since the 1960s the demand for ornamental aquarium fish has grown steadily and consequently cyanide fishing is still a popular fishing method despite its prohibition. This poses a severe threat to coral reefs in Southeast Asia. This study aimed to investigate the short-term stress reaction on photosynthetic yield in the tissues of three different hard coral colonies (branching growth forms Pocillopora damicornis and Seriatopora hystrix, and massive Porites lobata) to initially high and then decreasing cyanide exposure, mimicking cyanide fishing by fishermen. Experiments were performed both in situ in the coral reefs of the Marine Protected Area Pulau Pieh, West Sumatra, Indonesia, and in the aquaria facilities of ZMT in Germany. A Diving-PAM fluorometer was used for in vivo stress assessment of the holobiont. While in all species the photosynthetic efficiency was significantly reduced right after cyanide application, the massive species displayed much lower ΔF/Fm’ values. After three days in cyanide-free water all three coral species recovered to initial values of Fv/Fm, except for P. lobata. No bleaching or discolouration was detected by the conclusion of the experiment after 38 days. Especially Indonesian reefs with massive corals may be therefore more severely impacted by cyanide fishing since the retention time of the water in these reefs is longer than in reefs that consist primarily of branching corals. This might have implications for the management of different reef parts of the MPA.

Effect of anastrozole on masculinization in ornamental fish, dwarf gourami, &lt;em&gt;Trichogaster lalius&lt;/em&gt; (Hamilton, 1822)

In ornamental fishery, for commercialization and efficient propagation of fish species in demand, controlling their sex, male or female, plays an important role as it influences reproduction, growth and product quality. In one such common aquarium fish, dwarf gourami, Trichogaster lalius (Hamilton, 1822), males look more attractive and fetch better market price encouraging masculinization of this species. In the present study, we evaluated the effect of anastrozole on masculinization potential in T. lalius. The experiment consisted of two trials, in trial 1; anastrozole was incorporated into feed at 50, 100, 150 and 200 mg/kg and fed to first feeding fry for 50 days. In trial 2, immersion treatment of anastrozole was carried out at different doses of 250, 500, 750 and 1,000 μg/L for 3 h each on 3rd, 5th and 8th day of post-hatching. Oral administration of anastrozole resulted in 90.32% masculinization at 200 ppm and the immersion treatment of anastrozole produced 100% masculinization at 1000 μg/L. Histological sections indicated that the anastrozole treatments suppressed ovarian development, leading to the atretic oocytes. However, the testicular development was unaffected. Testosterone level increased whereas estradiol level decreased with increased dose of the chemical. Cortisol level also showed a significant increase in male with increased doses of anastrozole, indicating stress which in turn helped to synthesize the testosterone. The results show that the immersion treatment of anastrozole is more effective than oral administration in inducing masculinization in T. lalius.

MOLECULAR DETECTION OF MEGALOCYTIVIRUS GENOTYPE: INFECTIOUS SPLEEN AND KIDNEY NECROSIS VIRUS IN MALAYSIAN OVIPAROUS AQUARIUM FISH

The Malaysian ornamental fish industry’s recent production is recorded at RM350 million per annum. An Infectious Spleen and Kidney Necrosis Virus (ISKNV), one of the Megalocytivirus strains has been related to significant systemic infections that has ravaged ornamental fish stocks and had a severe financial impact on businesses in the sector. It is vital to identify Megalocytivirus host species among Malaysian oviparous ornamental fish as the virus can cripple the ornamental fish trade which is a major contributor to the country’s export trade. The purpose of this research is to determine the prevalence of Megalocytivirus, ISKNV strain in oviparous aquarium fish, Betta splendens, Danio rerio, Trichogaster lalius, Hyphessobrycon anisitsi and Puntigrus tetrazona in Malaysia. The DNA of the Megalocytivirus in the samples was detected using the nested polymerase chain reaction (PCR) method. Out of 239 samples collected in January 2019 and January 2020, six pooled samples (n=30) tested positive for ISKNV infections in D. rerio and T. lalius. Positive P. tetrazona samples in this study showed a distended abdomen as the only observable clinical sign whereas all other samples were asymptomatic. All the positive samples were similar to each other. In terms of the nucleotide identity of the ISKNV, which stood at between 98% and 100%. In conclusion, the positive samples can be categorised into Megalocytivirus genotype I.

The Effect of pH and Mineral Content of Fe, Ca, Mg, And Cl On The Growth of Koi Fish (Cyprinus carpio) in Aquariums with Water Sources of The Tuntungan River in Medan

The effect of pH and mineral content of Fe, Ca, Mg and Cl on the growth of koi fish (Cyprinus carpio) in an aquarium with water sources of the Tuntungan Medan river has been studied. Cultivate koi fish in the aquarium with water from the Tuntungan river had various pHs between 5 to 10. NaH2PO4 is used to reduce pH level, while NaHCO3 is used to elevate pH level. Before the fish was placed, the mineral content of Fe, Mg, Ca, and Cl in the water after pH arrangement was analyzed. The initial weight of the fish that will be incorporated into each aquarium was weighed. After ten days, the fish were weighed, and the mineral content of Ca, Mg, and Cl were determined by titration method, whereas Fe mineral was determined using the Visible Spectrophotometry method. The same thing is done on days 20, 30, 40, and 50. The results showed maximum growth at 120.50% of fish in the river water aquarium pH = 8.5 with high levels of iron (Fe) which fluctuated between 0.4343 mg / L - 0.6020 mg / L, the level of calcium (Ca) which fluctuated between 7.76 mg / L - 15.52 mg / L, the levels of magnesium (Mg) which fluctuated between 120.28 mg / L - 157.14 mg / L, and levels of chloride (Cl) which fluctuated between 27.99 mg / L - 32.48 mg / L. Minimum growth in amount of 88.02% found in the river water aquarium pH = 5.5 with the levels of iron (Fe) which fluctuated between 0.2246 mg / L - 0.5610 mg / L, the level of calcium (Ca) which fluctuate between 7.76 mg / L - 27.93 mg / L, the levels of magnesium (Mg) which fluctuated between 80.71 mg / L - 108.64 mg / L, and levels of chloride (Cl) which fluctuated between 17.99 mg / L - 39.98 mg / L. Water with pH = 9.5 is not suitable as a medium for the cultivation of koi fish.