Search

Non-destructive sampling methods offer practical advantages to detection and monitoring of viral pathogens in economically important farmed fish and broodstock. Here, we investigated whether blood, mucus and fin can be used as non-lethal sample sources for detection of scale drop disease virus (SDDV) in farmed Asian sea bass, Lates calcarifer. Detection of SDDV was performed in parallel from three non-destructive and seven destructive sample types, collected from both clinically sick fish and subclinical fish obtained from an affected farm. The results showed that SDDV was detectable in all 10 sample types with the percentage ranging from 20% to 100%. Blood was the best non-destructive sample source exhibited by the fact that it yielded 100% SDDV-positive tests from both sick (n = 12, 95% CI: 69.9-99.2) and clinically healthy fish (n = 4, 95% CI: 39.6%-97.4%) and is considered a "sterile" sample. This study also revealed concurrent infection of SDDV and two ectoparasites Lernanthropus sp. and Diplectanum sp., in all affected fish (n = 8, 95% CI: 46.7-99.3) during the disease outbreak. These ectoparasites also tested positive for SDDV by PCR, indicating that they were potential sample sources for PCR-based detection of SDDV and possibly other viruses infecting Asian sea bass.

The search for suitable fish meal replacements in aqua-diets is a salient agenda in the constant effort of making aquaculture practices more sustainable. In this study, we tested four customised diets composed by systematic inclusion of pre-selected fish meal substitutes, lupin kernel meal, BSF meal, TH and PBM on growth, metabolism, cytokine profile, gut morphology and microbiota of juvenile Lates calcarifer. Five isoproteic and isoenergetic diets were prepared viz. FM100 as a control (without fish meal substitute), while FM75, FM50, FM25 and FM0 indicates replacement of fish meal (FM) at 25%, 50%, 75%, and 100%, respectively by a mixture of four different pre-selected non-fish meal (NFM) ingredients. Fish fed FM100, FM75, FM50, FM25 exhibited consistent growth and haematological response, while the fish fed no fishmeal (FM0) showed significant decline in final body weight (FBW) and specific growth rate (SGR). The poor growth performance was correlated with a decrease in villous width, microvilli height and goblet cells density. A significant shift in abundance profile of Psychrobacter in the gut microbial profile of fish fed FM50 was noticed compared to fish fed FM100. The results of qRT-PCR showed up-regulated expression of innate immune responsive genes in the FM50 group. The adverse impacts on growth performance and gut health of fish fed FM0 suggest that the complete substitution of fishmeal is not advisable and the inclusion range of these alternatives should be decided for a species only after examining their effect on maximal physiological performance.

This paper estimates neighborhood effects on adult labor market outcomes using the Moving to Opportunity (MTO) housing mobility experiment. We propose and implement a new strategy for identifying transition-specific effects that exploits identification of the unobserved component of a neighborhood choice model. Estimated local average treatment effects (LATEs) are large, result from moves between the first and second deciles of the national distribution of neighborhood quality, and pertain to a subpopulation of nine percent of program participants.

Aim: To evaluate the ability of to inhibit the growth of V. harveyi in in-vitro co-culture assay and confer protection towards Artemia nauplii and seabass larvae against V. harveyi in in-vivo assay. Methodology: Enterococcus hirae was co-cultured with V. harveyi for 96 hrs and the samples were taken every 6 hr interval to determine the growth of the pathogen in in-vitro assay. In the in-vivo assay, E. hirae at different concentrations were introduced to the Artemia nauplii and seabass larvae cultures. After 24-hr incubation period, V. harveyi 6 -1 at concentration 10 CFU ml were added into the respective experimental tanks. Mortality was observed and recorded daily, until 50% mortality was observed in negative control group which challenged with V. harveyi only. Results: E. hirae was able to reduce the numbers of V. harveyi after 12 hr of co-culture incubation. In addition, E. hirae was administered into the Artemia nauplii and conferred protection 6 against V. harveyi with the best survival rate at concentration of 10 -1 CFUmL (70±3.1%). The untreated group seabass larvae challenged with V. harveyi presented low survival of (16.7±3.3%), 6 -1 while fish treated with probiotic E. hirae at 10 CFUml showed significantly increased survival rates (68.3±0.9%) after challenged. The survival of healthy unchallenged fish treated with probiotic was not significantly different with the control group. The pathogen loaded also reduced in groups treated with E. hirae respectively Interpretation: E. hirae strain LAB3, a potential probiont was able to reduce the number of Vibrios and conferred protection to Artemia and seabass larvae.

Physical and chemical properties of Asian sea bass (Lates calcarifer) backbone subjected to high pressure heating (autoclaving, 121ºC) for different times (30 min; AT-30; 60 min; AT-60; 90 min; AT-90) were studied. As heating time augmented, the increases in protein, α-amino group and hydroxyproline contents in liquor were attained, while hardness was declined indicating that more organic compounds were leached out from the bone matrix. More pronounced XRD pattern was observed in backbone autoclaved for 90 min as a consequence of nano-hydroxyapatite crystals agglomeration. Extension of high-pressure heating time reduced the organic matters as elucidated by TGA and DTA data. Asian sea bass backbone heated at 121ºC for 90 min using autoclave had the lowered protein and lipid contents but increased ash content with highest calcium (29.65 ± 0.69%), phosphorus (15.80 ± 0.07%) and iron (15.10 ± 0.61 mg/kg) contents, compared to those with shorter heating time. Therefore, pre-heat treatment could reduce the organic compounds and decrease bone hardness for further process, especially for bio-calcium production.

BACKGROUND AND OBJECTIVE Meghna river estuary plays a major role in the national fish production and is being connected to other channels that might accelerate the magnification of heavy metals in human tissue through the food chain after fish consumption. Therefore present study aimed to elucidate possible human health risks should people consume fishes from this river. MATERIALS AND METHODS Total 5 heavy metals (Cu, Zn, Pb, Cd and Cr) in 6 being exported and highly consumed fish species (Lates calcarifer, Penaeous monodon, Encrasicholina heteroloba, Polynemus paradiseus, Sillaginopsis panijus and Ilisha megaloptera) from fish landing center during January 2016 to February 2017, near the Meghna river, Noakhali, Bangladesh were measured in the present study by using atomic absorption spectrometry (AAS). RESULTS The metal concentration (μg g-1) varied as Cu 4.63- 73.57, Zn 39.54-180.44, Pb 0.011-0.019, Cd .003-.122 and Cr 4.92-15.88 where Zn and Cr surpassed the different food safety guidelines. Estimation of daily dietary intake (EDI) of all the elements was measured from the national fish consumption data. Value

Length and weight data for three species of fish Oreochromis niloticus, Lates niloticus, and Sydontus victorianus was collected from three East African lakes, Lake Victoria, Lake Baringo and Lake Naivasha. Correlation were done on weight and length based on the fish species, the lake collected from, sex, and the age. Correlation was found not to be a good measure of evaluating length weight relationship. Models had to be applied. Linear models, random regression models, proportional hazard models and threshold models. Random regression model was found to capture most of the information though it excluded the age of the fish on mean sum of squares error. The challenge with this is that it’s a long-term model which accounts for hatching to last date of the fish life.

Freshwater farming of barramundi Lates calcarifer in Thailand is a growing sector in aquaculture, but mortalities due to infectious diseases are still a major threat to this industry. In 2018, an episode of severe mortality in juvenile barramundi was noted in a freshwater earth pond site. Fish presented with severe gill necrosis, as well as severe cutaneous hemorrhages, scale loss, and discoloration at the base of dorsal fin (saddleback lesions). Histopathology revealed extensive necrosis of skeletal muscle and gill filaments, as well as basophilic inclusion bodies and megalocytosis in muscle, gill, liver, and kidney. Scale drop disease virus (SDDV) infection was subsequently confirmed by virus-specific semi-nested PCR. Further, DNA sequences of the viral major capsid protein (MCP) and ATPase genes had a respective homology of 99.85 and 99.92% with sequences of SDDV infecting barramundi in saltwater culture. Gill necrosis and saddleback lesions are not typical lesions associated with scale drop syndrome. Their presence was explained by Flavobacterium columnare isolation from the gill, followed by positive F. columnare-specific PCR. To our knowledge, this is the first report of SDDV-associated mortality in freshwater-farmed barramundi. Furthermore, this mortality presented as a concurrent infection with SDDV and F. columnare, with typical lesions of both infections.

Barramundi ( Lates calcarifer ) is known as Sea bass with a selling price of Rp.75,000 - Rp.80,000/Kg consumption size. The purpose of this study was to determine the effect of the addition of bread yeast with different doses to feed on the growth of Lates calcarifer . This study uses an experimental method with a Completely Randomized Design (CRD). The treatments were P0=0% yeast, P1=0.5%, P2=0.10%, P3=0.15%, P4=0.20% yeast from the weight of the feed given. The results of the study are the bread yeast influences the growth of Lates calcarifer . The highest absolute weight gain in P4 treatment was 0.507 g. The highest absolute length increase in P4 treatment was 0.990 cm. The lowest FCR at perlakuan P1 yaitu 15,55. The highest survival rates are P2, P3, and P4 which is 100%. Erythrocytes with the highest total amount in P4 treatment 12,58x10 6 - 18,62x10 6 cells/mm 3 . Leukocytes with the highest total number in P2 treatment were 27,96x10 6 - 44,641x10 6 cells/mm 3 . Water quality parameter values in the maintenance media are in the range of requirements for Lates calcarifer cultivation. The conclusion of the study is the addition of bread yeast affects the growth of Lates calcarifer and the optimal dose that can increase the growth is 0,20%.

Trace elements contamination in the aquatic ecosystem is a current and major environmental concern due to their non-degradable nature and toxic effects on human health. Concentrations of arsenic (As), chromium (Cr), cadmium (Cd) and lead (Pb) in fish were estimated to evaluate contamination levels and health risks for Bangladeshi adults. A total of six demersal fish species namely Mystus vittatus, Polynemus paradiseus, Sillaginopsis panijus, Lates calcarifer, Cynoglossus arel and Pseudapocryptes elongates were collected in summer and winter season from the coastal Karnaphuli River, Bangladesh. The analyzed trace elements varied between different species of fish. The concentration of studied trace elements exceed Food and Agriculture Organization/World Health Organization maximum tolerable intake indicating risk to human body. The mean concentration of As, Cr, Cd and Pb were found 2.18, 9.1, 7.2 and 4.38 times higher than the recommended value. Health risks associated with these trace element intakes were evaluated in terms of dietary intake and target hazard quotients (THQs). The THQs value for individual fish species was more than one which was responsible for non-carcinogenic health hazard due to fish consumption. Target Carcinogenic Risk (TR) value for arsenic and lead was also higher than USEPA standard (10−4) indicated chronic cancer risk to human. From the health point of view, this study showed that the inhabitants who consume these fishes are exposed chronically to trace elements pollution with carcinogenic and non-carcinogenic consequences.

To understand the physiological response of estuarine fish to acidification, barramundi (Lates calcarifer) juveniles were exposed to acidified seawater in experimental conditions. The molecular response of barramundi to acidification stress was assessed by RNA-seq analysis. A total of 2188 genes were identified as differential expression genes. The gene ontology classification system and Kyoto Encyclopedia of Genes and Genomes database analysis showed that acidification caused differential expressions of genes and pathways in the gills of barramundi. Acidification had a great influence on the signal transduction pathway in cell process. Furthermore, we detected that numerous unigenes involved in the pathways associated with lipid metabolism, carbohydrate metabolism, amino acid metabolism, glycan biosynthesis and metabolism specific and non-specific immunity were changed. This study indicates that the physiological responses in barramundi especially the immune system and energy allocation correspond to the variation of environmental pH. This study reveals the necessity for assessment of the potential of estuarine fishes to cope with acidification of the environment and the need to develop strategies for fish conservation in coastal areas.

Cage culture of finfish is becoming a popular alternate source of livelihood in Vembanad Lake in Kerala, India. A study was conducted during November to December, 2016 to assess the socio-economic status of the farmers practicing cage culture in Kerala and the resultant economic benefits. Data on demographic features, farming activities, specific culture and farm management practices, economics and problems related to cage farming were collected from 36 active farmers of the Ernakulam District. Etroplus suratensis (Pearl spot), Lates calcarifer (Asian sea bass), and Genetically Improved Farm Tilapia (GIFT) were the major species cultured

Microplastics (MPs) are physical anthropogenic pollutants and their ability to act as contaminant vectors in biological matrices is of serious ecosystem and human health concern. In the present study, we have, for the first time, screened and detected MPs in the stomach of a select group of commonly consumed fish species from a municipal water supply lake (Eleyele) in Nigeria. A total of 109 fish samples consisting of eight (8) species: Coptodon zillii (CZ: n = 38), Oreochromis niloticus (ON: n = 43), Sarotheron melanotheron (SM: n = 19), Chrysicthys nigrodigitatus (CN: n = 3), Lates niloticus (LN: n = 3), Paranchanna obscura (PO: n = 1), Hemichromis fasiatus (HF: n = 1), and Hepsetus odoe (HO: n = 1) were collected between February–April, 2018. Fish stomach content was screened for the presence of MPs using the density gradient separation technique (NaCl hypersaline solution) and examined using a fluorescence microscope. MPs were present in all the species screened (except H. fasciatus) with a frequency of 69.7% positive individuals in the examined species. MP prevalence was highest in ON (34%) > CZ (32%) > SM (13%) > CN (6%) and 5% each, for PO HO, and LN. On average, 1–6 MPs with sizes ranging between 124 μm and 1.53 mm were detected per individual. However, the highest number (34) of MPs was detected in the stomach of SM. Principal coordinate analysis (PCA) identified ecological variables such as habitat, feeding mode, and trophic levels as critical factors that may determine and influence MP uptake in fish population. The PCA showed stronger association between fish habitat, feeding mode, and trophic level with MP size and number in the benthopelagic species (ON CZ and SM), compared to demersal species (PO CN HO and LN). Given that MPs can act as vectors for the transfer of pathogens and environmental contaminants (both legacy and emerging), in addition to direct health risks to aquatic organisms, our findings raise concerns on the potential human/wildlife health effects of MPs in these economically and ecologically important food fishes.

Changes in gelling properties of unwashed barramundi gels with 1% and 2% added salt, then pressurized at 300, 400, and 500 MPa at ≤10°C and 50°C for 10 min were studied. Pressure-induced unwashed b...

Lake Nasser, a large man-made tropical reservoir, is located in the southern part of Egypt. The lakes’ fisheries have undergone a steady decrease during the last 10 years obscuring its potential for sustainability. Fisheries assessment study based on the fishing activities is essential to attain reliable information for construction a management plan to achieve rational and sustainable exploitation. Spatial and landing site surveys were conducted during the period from 2016 to 2017. More than 300 random fishing boats were examined to investigate their fishing gears characteristics, species composition, mean trophic level and catch per unit effort. More than 13,000 fish specimens from the catch were sampled and investigated for the gear selectivity study. The results indicate that trammel nets, gill nets and long-lines are the main fishing methods used. Thirty-four fish species were recorded in the lake, 6 of them were dominant, namely; Oreochromis niloticus, Sarothrodon galilaeus, Coptodon zillii, Lates niloticus, Alestes baramoze and Hydrocynus vittitus. The lake exhibits spatial variations in its productivity as the southern part is more productive. The time series of size and CPUE showed a high exploitation rate for the most important commercial fish species in the lake by the fishing gears used. Measures for fishery management based on gear selectivity are suggested for sustainability. Keywords: Lake Nasser, Fisheries management, Gear selectivity

Outbreaks of diseases in farmed fish remain a recurring problem despite the development of vaccines and improved hygiene standards on aquaculture farms. One commonly observed bacterial disease in tropical aquaculture of the South-East Asian region is tenacibaculosis, which is attributed to members of the genus Tenacibaculum (family Flavobacteriaceae, phylum Bacteroidetes), most notably Tenacibaculum maritimum. The impact of tenacibaculosis on the fish microbiota remains poorly understood. In this study, we analysed the microbiota of different tissues of commercially reared Asian seabass (Lates calcarifer) that showed symptoms of tenacibaculosis and compared the microbial communities to those of healthy and experimentally infected fish that were exposed to diseased farmed fish. The relative abundance of Tenacibaculum species in experimentally infected fish was significantly lower than in commercially reared diseased fish and revealed a higher prevalence of different Tenacibaculum species. One isolated strain, TLL-A2T, shares 98.7% 16S rRNA gene identity with Tenacibaculum mesophilum DSM 13764T. The genome of strain TLL-A2T was sequenced and compared to that of T. mesophilum DSM 13764T. Analysis of average nucleotide identity and comparative genome analysis revealed only 92% identity between T. mesophilum DSM 13764T and strain TLL-A2T and differences between the two strains in predicted carbohydrate activating enzymes respectively. Phenotypic comparison between strain TLL-A2T and T. mesophilum DSM 13764T indicated additional differences, such as growth response at different salt concentrations. Based on molecular and phenotypic differences, strain TLL-A2T (=DSM 106434T, KCTC 62393T) is proposed as the type strain of Tenacibaculum singaporense sp. nov.

Background colour influences the growth performance and feed utilization of various fish species. In the current study, the effects of different aquarium backgrounds (transparent, white, black, red, green and blue) on growth performance, feed utilization, digestive enzyme activities, flesh quality, carcass composition and haematological parameters were investigated in Asian seabass (Lates calcarifer). The fish (16.17 ± 0.02 g initial body weight) were distributed into eighteen glass aquaria (6 treatments × 3 replications) with the various background colours and reared for 10 weeks. At the end of the experiment, positive growth performance and feed utilization were observed in fish reared against transparent, white, black or green backgrounds, while negative effects were noted for fish reared on the remaining treatments (p

Skin abrasions often occur in farmed fish following handling by labourers, injury by farm facilities, cannibalism and ectoparasites. Vibrio spp. are opportunistic pathogens that can invade host fish through damaged tissues and cause outbreaks of vibriosis. This study describes the effect of skin abrasions on the infectivity of V. harveyi using Asian seabass Lates calcarifer (Bloch, 1790) fingerlings as a case example and compares bacterial load and fish survival following immersion challenge with different doses. In total, 315 fish (6.67 ± 1.8 g) were divided into 3 treatments: skin abrasion followed by immersion infection, immersion infection only and an uninfected, uninjured control. Fish in the infection treatments were divided into 3 subgroups and exposed in triplicate to a 7 d immersion challenge with 106, 107 and 108 CFU ml-1 of live V. harveyi. No mortalities were observed in the control and immersion infection groups. However, fish in the skin abrasion treatment group that were infected with 108 CFU ml-1 of live V. harveyi showed signs of progressing disease throughout the experiment, which resulted in mortalities. Significantly higher bacterial loads (p < 0.05) were recorded in the intestine, liver and gills of the fish in this group. Fish in the skin abrasion treatment that were exposed to 107 and 108 CFU ml-1 of V. harveyi showed 100% mortality by Days 5 and 4, respectively. These findings confirm that skin injuries increase the susceptibility of seabass fingerlings to V. harveyi infection.

Lake Victoria, the second largest freshwater lake in the world, supports an enormous flora and fauna biomass, with a large human population around the Lake. The lake is a source of food (fish), water for domestic use and crop and livestock production, transportation and tourism, among other uses. As a result of these varied uses, human intervention within the lake and its catchment has resulted in several ecological changes in the lake in recent years, with profound effects on its fish resources. One of the most notable changes is the reduction and risk of extinction of some fish species, including the endemic tilapiine species (Oreochromis esculentus and Oreochromis variabilis), catfishes (Xenoclarias eupogon), haplochromines and cyprinids (Labeo victorianus and Barbus altinialis) in the lake. The reduced biodiversity, as well as extinctions within the lake, has been attributed to the introduction of alien fish species (e.g. Nile perch (Lates niloticus) and Nile tilapia (Oreochromis niloticus) into the lake, habitat loss and cultural eutrophication. If left unchecked, these changes will have devastating effects on the lake's resources, as well as to people living around the lake and beyond who depend on the lake fisheries for their livelihood. Thus, there is an urgent need for management measures based on sound scientific research to be implemented in order to curb the loss of ichthyodiversity within the lake, as well as to save the livelihoods of those stakeholders who are either directly or indirectly dependent on the lake.

Seabass, Lates calcarifer (Bloch 1790) is an euryhaline and a popular fish in south and southeast Asian countries due to its higher growth rate, giant size, excellent taste and higher market demand. It is locally known as Bhetki or Koral and available around the year in the estuarine and coastal regions of Bangladesh. In many countries (e.g. Australia, India, Malaysia, Philippines, Thailand etc.), the species is artificially propagated and commercially cultured. The breeding technology has not yet been developed in Bangladesh. Now a days Bangladesh is progressing day by day in freshwater aquaculture but it is far behind in case of coastal and mariculture. To get the mass seed production of fry/fingerlings of seabass, we need to develop the artificial breeding technology of the said species. There are only a few studies published on biology, aquaculture, brood development and artificial breeding activities of seabass in Bangladesh where investigators used live feed (Tilapia) and small indigenous fish species (SIFS) on brood development in captivity but none could adapt to formulated feed on seabass aquaculture. Some researchers made attempt to develop seabass broodstock for artificial breeding purpose, but none can success in captive condition in Bangladesh. Only one breeding trial conducted by stripping method using wild brood, but the development of the fertilized eggs ceased attaining up to the neurola stage, Res. Agric., Livest. Fish.6(3): 405-414, December 2019

Neobenedenia girellae is one of the most pathogenic parasites affecting marine fish in captivity conditions. The use of chemicals for parasite prevention and treatment have several benefits; however, they can cause various negative side-effects. In an effort to discover cost-effective and sustainable practices, our current study was aimed at investigating the efficiency of freshwater treatments on N. girellae. A challenge test was conducted to produce infected fish which became materials for the freshwater immersion experiments. The duration and reaction of the parasites at different development stages from eggs to adult parasites were examined. Our findings revealed that 100% of the adults and oncomiracidia of N. girellae were killed quickly in freshwater. The eggs of N. girellae, however, were highly resistant to freshwater with a hatching success rate of more than 95% in all the freshwater immersion treatments (2, 5, 10 and 30min). The eggs hatched mainly on day 7 and finished hatching on day 8. Thus, the freshwater immersion method can be applied to treat N. girellae at most stages excepted for the egg stage. The best practical treatment for this parasite is to perform a replicated immersion recommended 8 days following the first treatment.

The pelagic fishery of Lake Tanganyika, which is largely made up of the three species Lates stappersii, Limnothrissa miodon, and Stolothrissa tanganicae, has been in decline, and there is no clear understanding of the primary underlying causes. It has been suggested that climate change has altered the primary productivity of the system, but detailed knowledge of the system's food web is required to elucidate the effect on higher trophic levels. The aim of this study is to determine the diet of the three commercially important fish species. Muscle tissue samples for stable isotope analysis were taken from February through April 2017, supplemented with stomach samples from L. stappersii for use in stomach content analysis. The stomach analysis showed an ontogenetic change in the diet composition of L. stappersii, shifting from copepods to fish larvae, supplemented with shrimp, to whole fish prey as the fish grew larger. Stable carbon and nitrogen isotope values from fish muscle were consistent with this observation, and also seemed to indicate that fish of similar sizes had similar diets, irrespective of species. This suggests that the diet of the pelagic fish species might be better explained by size, rather than species. The isotope data revealed a short range of δ15N values from primary consumers to fish, which may help explain the high fisheries productivity of Lake Tanganyika, and the strong impact of primary productivity changes on fisheries yield.

Aerobic metabolic scope is a popular metric to estimate the capacity for temperature-dependent performance in aquatic animals. Despite this popularity, little is known of the role of temperature acclimation and variability in shaping the breadth and amplitude of the thermal performance curve for aerobic scope. If daily thermal experience can modify the characteristics of the thermal performance curve, interpretations of aerobic scope data from the literature may be misguided. Here, tropical barramundi (Lates calcarifer) were acclimated for ∼4 months to cold (23°C), optimal (29°C) or warm (35°C) conditions, or to a daily temperature cycle between 23 and 35°C (with a mean of 29°C). Measurements of aerobic scope were conducted every 3–4 weeks at three temperatures (23, 29 and 35°C), and growth rates were monitored. Acclimation to constant temperatures caused some changes in aerobic scope at the three measurement temperatures via adjustments in standard and maximum metabolic rates, and growth rates were lower in the 23°C-acclimated group than in all other groups. The metabolic parameters and growth rates of the thermally variable group remained similar to those of the 29°C-acclimated group. Thus, acclimation to a variable temperature regime did not broaden the thermal performance curve for aerobic scope. We propose that thermal performance curves for aerobic scope are more plastic in amplitude than in breadth, and that the metabolic phenotype of at least some fish may be more dependent on the mean daily temperature than on the daily temperature range.

The spotted sea bass (Lateolabrax maculatus) is an economically valuable cultured fish species in China. In this study, 20 novel polymorphic microsatellite loci of L. maculatus were isolated from genomic data and characterized using 40 wild individuals. The number of alleles and the effective number of alleles ranged from 2 to 12 (average of 5.1000) and from 1.180 to 8.000 (average of 3.3097). The observed and expected heterozygosities ranged from 0.083 to 0.875 (average of 0.4405) and from 0.153 to 0.875 (average of 0.5633), respectively. Deviation from the Hardy-Weinberg equilibrium was observed in 11 loci (P < 0.05). Polymorphism information content ranged from 0.141 to 0.862 (average of 0.5265) and most loci were heterozygous. Cross-amplification trials in two cryptic congeneric species, the largemouth bass, Micropterus salmoides, and the barramundi, Lates calcarifer, achieved successful amplification of 16 primers. The microsatellite markers developed in this study could be used for research on genetic breeding of L. maculatus and genetic relationships among tested taxa.

Hidayati D, Nurindra AR, Abdulgani N, Setiawan E, Maulidina N, Syahroni N, Mulyadi Y. 2021. Fish disease study of Asian seabass (Lates calcarifer) in a floating marine cage: Endoparasite and blood profile. Biodiversitas 22: 4505-4511. The Indonesian government has multiple targets and priority programs to increase aquaculture productivity in 2021. Hence, the development of mariculture commodities such as Asian seabass (Lates calcarifer) in one of the potential coastal areas, Sendang Biru, is strategic. However, sustainable productivity needs good management, including the health monitoring of fish. This study aimed to determine the condition of seabass under mariculture in a floating cage in Sendang Biru, Malang, Indonesia. Thirty seabass (Lates calcarifer) from 0 to 60 days after stocking age (ASE) were taken from a Sendang Biru floating cage. Blood and intestine samples were taken five times from day 0 to day 60 ASE. Blood samples were carried out through the caudal vein and observed using a hemocytometer. Endoparasite analysis was performed by fish intestine examination from the anterior intestine to the posterior rectum. Pseudoterranova and Diphyllobothrium were found with 10% and 3.33% prevalence, respectively. The intensity of Pseudoterranova was one individual/fish, and that of Diphyllobothrium was 2.33 individuals/fish. The highest mean of total erythrocyte count (TEC) found in 0 day ASE was at the level of 0.82±0.55×106 cells/mm3, and the lowest was found in 60 days ASE (0.51±0.24×106 cells/mm3). The highest mean of total leucocyte count (TLC) was 9.20±3.69x104 cells/mm3, at day 0, and leukocyte levels tended to decrease until day 60 ASE (7.74±3.43×104 cells/mm3). Overall, despite the TEC and TLC tending to decrease from 0 to 60 days ASE, in statistically indicated no significant differences in TLC at different ASEs (p > 0.05). The hematological profile indicated the health statuses of the cultured Asian seabass in the current study were in a condition of anemic and infected.

Fish fillets are very popular products that have been dominating the world fish market. Seafood industry is always looking for innovative processing technologies to improve the quality of raw fish fillets. Texture profile analysis is a modern technique to indicate the quality of fish muscle by measuring various parameters like hardness, cohesiveness, springiness, chewiness, resilience and adhesiveness. Texture of the fish muscle is dependent on its composition which can be treated in various ways to maintain and/or improve the quality throughout cold chain. Soluble protein injection is an alternative method to improve the fillet texture and quality. In this study, fish protein soluble (FPS) was recovered from seabass filleting waste and injected to fish fillets prepared from same fish species i.e. seabass (Lates calcarifer). FPS was injected in 4 different incorporation levels at 0, 5, 10 and 15% (v/w) and denoted as C, TI1, TI2, TI3 respectively. Texture profile of the samples was analysed during chilled storage and highest hardness values were obtained in TI2 samples (13451.67±27.45 g) and lowest in control (C). TI1 samples showed better adhesiveness (-1338.20±12.32 g/s) compared to other samples. Cohesiveness, gumminess, springiness, chewiness and resilience showed that the protein injection had significant effect (p

The purpose of this study was to determine the effect of adding honey to the feed for growth and the best dosage for the growth of white snapper seeds.The white snapper seeds used have an average weight of ± 2.5 g / fish.This study used an experimental method with a Completely Randomized Design (CRD).The experiment was carried out in 5 (five) treatments and each treatment had 3 (three) repetitions.The treatment consisted of adding honey to the feed with a treatment dose of (A) 0 ml / kg of feed, (B) 50 ml / kg of feed, (C) 100 ml / kg of feed, (D) 150 ml / kg of feed and (E) 200 ml / kg of feed.The results indicated that the addition of honey to the feed had a significant effect on the growth of white snapper seeds.The best dose of honey is at a dose of 200 ml / kg which has the best effect on fish growth.The condition of water quality during the study was in a suitable range for the life of white snapper seeds.

‘Big belly’ disease is a chronic, granulomatous bacterial enteritis and peritonitis, first reported in 3- to 4-week-old Asian seabass or barramundi, Lates calcarifer Bloch fry. Affected fry are emaciated and have a swollen abdomen, and the condition is referred to as ‘skinny pot-belly’ or ‘big belly’ disease. In this study, histopathological examinations of diseased fish from a batch of 2-month-old, 6- to 8-cm L. calcarifer fingerlings, kept in seawater recirculating aquaculture systems, showed pathology resembling ‘big belly’ disease. Ethanol-fixed tissues were tested positive using specific PCR primers based on 16S rRNA genes. In situ hybridization using dioxygenin-labelled positive PCR products on formalin-fixed paraffin-embedded tissues showed positive reactions with intralesional, clusters of the large, ‘big belly’ coccobacilli. A phylogenetic tree constructed based on analyses of these 16S rRNA gene PCR products from five positive fish suggests that the ‘big belly’ bacterium is most likely a novel Vibrio species.

Akoth AJ, Mahiri OS, Obiero K. 2019. Influence of climatic and non-climatic factors on fishing activities in Lake Victoria, Kisumu County, Kenya. Intl J Bonorowo Wetlands 11: 7-17. The aim of this study was to determine the impact of climatic factors like dry spells, rainfall, and wind strength, as well as non-climatic factors like overfishing, water hyacinth, and predators on fishing activities on the shores of Lake Victoria in Kisumu County. The research used a descriptive survey design. The study area comprised thirty-two beaches, of which eight were chosen to represent Kisumu County as a whole. The eight beaches were sampled using a systematic sampling technique. The data was collected using a sample size of 362 respondents. Fish landing data over the past ten years was collected at the beaches and at the Kenya Marine and Fisheries Research Institute (KEMFRI), while climate data was received from the Kisumu Airport Regional Meteorological Department. Primary data was collected from the beaches using questionnaires and interviews, whereas secondary data was collected from KEMFRI using document analysis guidance, books, and publications. The results were processed and analyzed with the help of the Statistical Package for Social Sciences (SPSS) application, which assisted in the calculation of frequencies, means, and percentages. The study discovered a linkage between climatic factors and fishing activity. Climatic factors and fishing activities have a substantial relationship, according to the study. The amount of rainfall had an effect on fish captures, albeit the effect differed by fish species; Orechromis (r =.260), Lates niloticus (r =.130), and Protopterus (r =.184) had positive correlations with rainfall, whereas Rastrinoebola argentea and Claras gariepinus had negative correlations. Overall, the findings showed a positive correlation coefficient (r =.079) between rainfall and total fish catch. Fish numbers in the lake have decreased due to a dry season accompanied by high temperatures. Strong wind had a negative impact on fishing activities, whereas mild to moderate wind favored fish catch. Non-climatic factors had a significant detrimental impact on fishing activity in Lake Victoria, according to the study. The researcher came to the following conclusions based on the findings: there was a relationship between climatic elements and fishing activities; non-climatic factors primarily influenced fishing activities negatively; however, fishermen implemented mitigation strategies to help address non-climatic factors. Policymakers should regulate fish harvesting as dictated by climatic and weather variations, assess the impact of non-climatic elements in fish production and recommend appropriate mitigation measures, and finally, regulations should be enhanced to save endangered fish species from extinction, according to the findings.

Sufardin, Sriwulan, Anshary H. 2021. Co-infection with Trichodina (Ciliophora: Trichodinidae) and Aeromonas caviae synergistically changes the hematology and histopathology of Asian seabass Lates calcarifer. Biodiversitas 22: 3371-3382. Consequential interaction contributed by parasitic and bacterial infections in fish has received little attention and impact of co-infection is mostly undescribed. This study identifies and describes notable damage arising from the co-infection of Trichodina and Aeromonas caviae infecting the seabass Lates calcarifer. A completely randomized experiment was performed with 4 infection treatments (healthy fish; fish naturally infected with Trichodina sp.; healthy fish injected with A. caviae; fish naturally infected with Trichodina sp. and injected with A. caviae) and 3 replicates. Fish were obtained from the Takalar Brackish Aquaculture Institute, South Sulawesi, Indonesia. The data were statistically tested using linear regression analysis. The results showed bacterial pathogenicity, lymphocyte percentage, and histopathological quantification were statistically different (P < 0.05). Meanwhile, the number of erythrocytes and leukocytes, the percentages of monocytes and neutrophils were not significantly different (P > 0.05) between treatments. The non-infected fish showed no cell inflammation and necrosis, very little hemorrhage (liver and gills), negligible hemorrhage and melano-macrophages (kidney). Kidneys and liver were the most damaged organs of co-infected fish, with a large number of inflammatory cells, hemorrhages, vacuoles, melano-macrophages, scar tissue, inflammation and necrosis. Infection with Trichodina sp. presented less damage than the co-infection of A. caviae and Trichodina sp. In conclusion, single infection showed a mild pathological impact, meanwhile, the co-infection of Trichodina sp and A. caviae contribute significantly to fish’s health.

A study was conducted in Lake Victoria to assess the occurrence, levels and risks of indicator polychlorinated biphenyls (PCBs) in four processed Lates niloticus (L.) products (salted-sundried, trims, smoked and deep-fried). Samples extractions were done using QuEChERS method while detection and quantification of congeners was done using a GC- ECD and GC- MS. Six PCBs (CB 28, CB 52, CB 118, CB 138, CB 153 and CB 180) were detected at measurable quantities in fish products. The PCBs; CB 138, CB 153 and CB 180 dominated the loading due to their structures and high degree of chlorination. However, the mean concentration of ΣPCBs in this study were below MRL of 75 µg/kg set for fish by European Commission, implying that the fish products were safe for human consumption in regard to indicator PCBs. Similarly, indicator PCBs, CB 138, CB 153 and CB 180 were more prevalent (20 to 80%) in all fish products than other congeners. For both adults and children the cancer risks were low-to-moderate (ranging from 2.0E-04 to 3.0E-04 for adults and 2.0E-04 to 1.0E-03 for children) while the non-cancer risks were insignificant as the Hazard Indices were less than one. Key words: Polychlorinated biphenyls (PCBs), kayabo, trims, smoked products, deep-fried products, extracting solvent.

One of the important components in aquatic ecosystems is fish diversity, which is a key factor in determining its functionality. The coral reef fish is one of the aquatic biotas susceptible to pollutants. Besides being able to influence the composition of fish diversity, it also has an impact on its biological factors, such as its length-weight and conditions. This study aims to examine the relationship of length-weight and condition factors of four dominant fishes caught, which are ecologically and economically important, namely Lates calcarifer, Parachaetodon ocellatus , Stephanolepis cirrhifer, and Chelmon rostractus. These fish species were dominantly caught using bubu trap. The results of the length-weight relationship were b

The global ornamental fish trade enables translocation of exotic aquatic pathogens. In many countries, health certification and visual inspection of imported fish are key components of biosecurity to prevent the introduction of aquatic diseases. However, infected fish do not always exhibit clinical or behavioural signs of disease, and alternatives to visual inspection must be validated. This study examined the use of environmental DNA (eDNA) to detect sub-clinical parasite infections at border control. We simulated the export process of live ornamental fish in which non-infected fish, infected fish, treated fish, and non-infected fish held in contaminated water were packaged and delivered in 48 h. Quantitative PCR (qPCR) was used to detect eDNA of an ectoparasitic monogenean, Neobenedenia girellae, infecting barramundi, Lates calcarifer. The qPCR assay did not reliably detect parasite eDNA under 2 copies/µL from fish with sub-clinical infections (mean parasite intensity = 6.80 ± 4.78 S.D.), suggesting parasite infection loads tested in this study may be too low for reliable detection within the timeframe used to export live ornamental fish. Quantitative PCR tests detected parasite eDNA in 50% of infected fish and 70% of non-infected fish in contaminated transport water. This indicated a high plausibility of false negative detections because of low eDNA concentrations in transport water and false positive detections of DNA from dead parasites in the water. Environmental DNA screening methods for border control biosecurity must overcome limitations posed by low eDNA concentrations in the water, limited timeframes for sample processing, and the essential differentiation between live parasite infections and dead, non-viable parasites.

Fish maw, or swim bladder, has long been used as food and medicine in Asia, particularly in southern China. Considering its history as luxury and nutritious seafood, surprisingly little information on volumes, values, source of maw or species composition involved in the trade is available. In 2015, Hong Kong, the global trade hub for maw, introduced a ‘maw’ commodity code enabling a first global look at its trade. This study finds that 3144–3882 t of dried fish maw was imported annually to Hong Kong from 2015 to 2018, coming from about 110 countries/territories, with a declared import value of 264–394 million USD. These volumes and values, similar to those of the better-known sea cucumber and shark fin trades, highlight the growing importance of maw. Prices can involve massive mark-ups, with investment speculation associated with the most valuable maw categories. Similar volumes to those imported are re-exported annually, mostly to Vietnam. By volume, 50% of maw came from Uganda, Brazil, Tanzania, India and Vietnam. Species composition was dominated by croakers (Sciaenidae), with Lates perch (Latidae), pufferfish (Tetraodontidae), various catfish (Siluriformes) and pike conger (Muraenesocidae) also traded, among other species. This lucrative trade has two components, high value maw and cheaper maw for regular consumption, and is expanding into new markets, such as shark fin substitution. There is loose association between trade category and species which can lead to confusion for consumers. Considering possible threats to biodiversity and evidence of illegal and secretive trade, management is called for to harness benefits and reduce risks.

Vibrio harveyi causes vibriosis in various marine aquaculture fish species, especially when they are young. The infection subsequently leads to significant economic losses for aquaculture farms. Vaccination is recommended to control this disease. This study describes the efficacy of a live attenuated V. harveyi strain MVh_vhs (LAVh) as a vaccine candidate in controlling infection by wild‐type V. harveyi (WTVh) in Lates calcarifer. A total of 240 fingerlings were divided into four groups. Group 1 was not vaccinated and was not challenged, Group 2 was vaccinated with a formalin‐killed V. harveyi (FKVh), Group 3 was vaccinated with the LAVh before challenge and Group 4 was not vaccinated and was challenged. Bath vaccination was employed for one hour before the LAVh distribution was determined in the fish mucus, gill, liver, gut, kidney and spleen. The gills, livers, kidneys and skins were also sampled for gene expression analysis. To challenge the fish, skin abrasion was conducted before the fish were challenged by immersion with WTVh. The results revealed an extensive distribution of the LAVh in the liver and kidneys of the fish in Group 3 for the first 12 hr, resulting in mild lesions compared with Group 1. Similarly, there were significantly (p

Biological hydroxyapatite (HA) can be obtained from fish bones. However, various fish species will provide HAs with different morphologies, porosities and purities. In this study, the properties of HAs prepared from four different fish bones, including catfish (Pangasius hypophthalmus), tilapia (Oreochoromis sp.), seabass (Lates calcarifer), and yellowfin tuna (Thunnus albacares), were characterized and compared. By using the same treatment conditions with a calcinating temperature of 700 °C for 2 h, HA prepared from seabass (Lates calcarifer) bones showed the most uniform and smallest size of ca. 50–70 nm. The HA powder obtained from tilapia (Oreochoromis sp.) bones presented the highest specific surface area of 32.83 m2 g−1. All HA products had a similar polycrystalline property and the Ca/P ratio of about 1.80. These findings are particularly useful to consider for further production and applications of HA powders prepared from fish bones.

Fish skin is a byproduct part and can be converted into value added product like gelatin. The objective of this research was to produce gelatin from two fresh-water fish skins i.e. Nile tilapia (Oreochromis niloticus) and Nile perch (Lates niloticus) and determine the physicochemical characteristics of the obtained gelatin. The physicochemical properties, free amino acids, protein content, pH, viscosity, colour, melting point, clarity, water holing capacity (WHC) and fat binding capacity (FBC), were studied and compared to the commercial bovine gelatin. Nile perch gelatin presented (87.24%) protein content which was resembles to bovine gelatin (88.18%). The viscosity (6.02 cP) of Nile tilapia extracted gelatin was also comparable to the bovine gelatin (6.77 cp). Results showed that the lightness of Nile tilapia gelatin (37.07) was greater than that of bovine gelatin (31.75). Regarding to the WHC, of Nile perch gelatin was higher by 3-fold (687.97%) than bovine gelatin (225.17%). While the Nile tilapia presented 1.4-fold (637.18%) higher than that found in bovine gelatin. Based on obtained results, it could be recomended that fish gelatin could be considered an excellent alternative to mammalian gelatin because of its functional properties similarity with commercial bovine gelatin.

Sea bass (Lates calcarifer) is a key aquaculture species in Malaysia, produced as part of a polyculture system in cages but predominantly as a single species in ponds. The production of sea bass in Malaysia has decreased substantially since 2015. Several studies suggest disease may be the main cause for such decline, but changing economic conditions may also have played a role in this decline. In this paper, we use Data Envelopment Analysis (DEA) to examine these issues as well as identify the key drivers of efficiency and capacity utilization in the grow-out finfish industry. Our results suggest that most farms are technically efficient, but many are operating at lower levels of capacity utilization. Socio-demographic factors appear to affect pond production but less so cage production. The results suggest that the reduced output of sea bass is largely in response to changed economic conditions (output and input prices).

Background and objective Circadian rhythm disorder was proved that may make a result of a wide variety of adverse health consequences, however, does circadian rhythm disorder always harm organisms in their whole life process? The aim of the present study was to evaluate the influence of circadian rhythm disorder on barramundi Lates calcarifer at different life stages. Materials and methods The growth and immune responses of larval and juvenile barramundi Lates calcarifer under various circadian rhythm disorder situation (13, 16, 19 and 24 h light time) were investigated in this experiment. Results The results showed that total length of larval and juvenile significantly increased comparing to the control group when the light time was extended to 16 h, but the length of fish in 24 h light time group showed significantly lower than the control. The cortisol level of larvae in 16 and 19 h light time groups significantly differed from other 2 groups. To juvenile, circadian rhythm disorder didn't make any influence on both T-SOD and ACP activity, the same result also appeared in cortisol concentration. The activity of three immune enzymes of larval from 16 and 19 h light time groups were all stimulated to increase by the homologous circadian rhythm disorder compared to the control. Conclusion In brief, lightly circadian rhythm disorder (prolonged 3 h light times) can benefit in fish growth. Although it brought some immune response to larvae which may cause adverse effects, all these negative effects would be eliminated when they grow up to juvenile.

Increased production of Seabass fish (Lates calcarifer) influences the stocking density used. The purpose of this study was to determine the growth and survival of Seabass (Lates calcarifer) at different densities of low salinity stocking. The study was conductedin May-June 2019 at the Laboratory of Fisheries, University of Muhammadiyah Malang. The material used in the study of Seabass fish (Lates calcarifer) as many as 550 fish with a size of 7 cm and fish feed in the form of B2 Stella. The method used was experimental with a completely randomized design (CRD) with 4 treatments and 3 replications, namely 1 fish/2 L as control (A); 2 fish/2 L (B); 3 fish/2 L (C); 4 fish/2 L (D). Data analysis used anova(P

Diadromy is a form of migration where aquatic organisms undergo regular movements between fresh and marine waters for the purposes of feeding and reproduction. Despite having arisen in independent lineages of fish, gastropod molluscs and crustaceans, the evolutionary drivers of diadromous migration remain contentious. We test a key aspect of the 'productivity hypothesis', which proposes that diadromy arises in response to primary productivity differentials between marine and freshwater habitats. Otolith chemistry and biochronology data are analysed in a facultatively catadromous tropical fish (barramundi, Lates calcarifer) to determine the effect of freshwater residence on growth rates. Individuals that accessed freshwater grew ~ 25% faster on average than estuarine residents in the year following migration, suggesting that catadromy provides a potential fitness advantage over non-catadromous (marine/estuarine) life histories, as predicted by the productivity hypothesis. Although diadromous barramundi exhibited faster growth than non-diadromous fish, we suggest that the relative reproductive success of diadromous and non-diadromous contingents is likely to be strongly influenced by local environmental variability such as temporal differences in river discharge, and that this may facilitate the persistence of diverse life history strategies within populations.

Heavy metals content in seafood, especially fish species has been of increasing concern to the human health. Nowadays, with increasing dependency towards farmed fish for sources of dietary protein and essential minerals, this heavy metals contamination in fishes are still questionable. This study aimed to investigate the accumulation of heavy metals in farmed fish, Lates calcarifer different organs from Setiu tropical coastal lagoon, Terengganu, Malaysia throughout its out-growing phase in the farm from the fingerling release up to their marketable size. Selected heavy metals namely Cu (Max:291.5±99.31), Zn (Max: 84.89±12.76), As (Max: 26.01±5.170), Cd (Max: 1.634±0.014), Hg (Max: 0.165±0.029) and Pb (Max: 0.634±0.550) in the fish was analyzed using ICP-MS after Teflon bomb closed digestion. The metal accumulation in each organ were generally found in the order of liver > gill > muscle. The concentrations of Cd and Zn in the liver were found to increase with fish size in each organ based on the association found in the principal component analysis (PCA). Meanwhile the overall findings observed negative correlation with L. calcarifer growth in fish size for all other heavy metals and organs. The amount of As in the fish muscle throughout its growth can be potentially harmful to humans with the highest averaged concentration at 3.29±0.65 mg/kg dw above the standard set by the Malaysian Food Regulation (1985) of more than 1 mg/kg. Meanwhile, all the other heavy metals were relatively safe and the concentrations well below the standard set by both national and international guidelines.

Background and objective Amyloodinium ocellatum infects the gills and skin of both marine and brackish water fishes. The aim of the present study was to examine pathogenesis, prevalence, trials for treatment and histopathological alterations of Amyloodinosis in naturally infested Asian Seabass Barramundi Lates calcarifer and Hamour Epinephelus polyphekadion in Ismailia Governorate, Egypt. Materials and methods A total number of 1447 Red Sea cultured Seabass (Lates calcarifer) broadstock and a total number of 53 Red Sea cultured Hamour, Epinephelus polyphekadion broadstock were collected and subjected for the study. Fishes showed symptoms of sudden death and respiratory distress besides Amyloodiniosis on gills and skin. All fishes were treated with various treatment protocols while gills of naturally infected fishes were examined histopathologically. Results The clinical signs of infested fishes were flashing, surfacing, off food and respiratory distress. The intensity of infestation of Amyloodiniosis was more sever in Asian Seabass than Epinephelus polyphekadion while treatment of choice was copper sulphate (prolonged bath), freshwater bath and formalin consequently. Conclusion Treatment of choice for Amyloodinium ocellatum infestation in Asian Seabass was copper sulphate (prolonged bath) followed by freshwater bath then formalin.