Effect of Sanitizers on Planktonic Edwardsiella tarda Isolated from Asian Stinging Catfish Heteropneustes fossilis (Bloch 1794)

Incidence of Edwardsiella tarda in Asian stinging catfish, Heteropneustes fossilis (Bloch), and its sensitivity to antibiotics and sanitizers was studied. Five out of 10 representative lots of H. fossilis were positive for E. tarda. The minimum bactericidal concentration (MBC) of sanitizers (hydrogen peroxide, glutaraldehyde, benzalkonium chloride, sodium hypochlorite, and iodophor) on planktonic E. tarda varied with strains, suspending media (distilled water, physiological saline, pond water, and tryptic soy broth), and combination of factors. The time taken by the sanitizers to achieve 5-log reductions varied greatly between 1 min and 180 min at X and 2X MBCs of sanitizers. Benzalkonium chloride, glutaraldehyde, and sodium hypochlorite were effective in reducing the planktonic E. tarda at concentrations ranging from 3.13 ppm for glutaraldehyde to 25 ppm for sodium hypochlorite. Edwardsiella tarda strains were highly sensitive to ciprofloxacin and exhibited varying degrees of resistance to other antibiotics.     

Exposure to salinity stress cause ovarian disruption in a stenohaline freshwater teleost,Heteropneustes fossilis (Bloch, 1794)

Stenohaline freshwater fish with narrow salinity tolerance are susceptible to saline stress from global climate change and anthropogenic activities. The present study elucidated that saline exposure during the sensitive window of preparatory phase of oocyte maturation significantly affected gonadosomatic index, ovarian histology and morphometric features of oocytes in a stenohaline freshwater catfish, Heteropneustes fossilis (Bloch, 1794) in a dose (2 ppt, 5 ppt)—and duration (8, 24 days)‐dependent manner. The gonads of H. fossilis show annual maturation cycle. Loss of integrity of ovigerous lamellae, disruption of ovarian stroma, disrupted oolemma, ooplasmic vacuolization, damaged germinal vesicles and altered morphometry of previtellogenic oocytes, such as chromatin‐nucleolus, early perinucleolar and late perinucleolar, elucidated consistent effects of saline exposure except at 8 days exposure to 2 ppt of saline. Increased salinity might have affected the transmembrane ion/water transport and disrupted the osmotic balance in ovary that eventually led to impairment in growth of ovary and oocyte maturation. The susceptibility of ovary to comparatively less concentrations of saline exposure might be due to sensitiveness of ovary/oocytes during the early phase of growth. Fluctuating salinity along with other stressors can affect metabolic and growth rates, fecundity and ultimately survival of fish.     

Smalltooth sawfish (Pristis pectinata Latham, 1794) in the Casamance River,Senegal: A historical perspective

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Insights into population genetics,connectivity and demographic history of the longnosed skate Dipturus oxyrinchus (Linnaeus, 1758) in the western Mediterranean Sea

1. Genetic information is crucial for the conservation of Dipturus oxyrinchus (Linnaeus, 1758), a threatened large skate with declining populations over most of its geographical range. The main aim of the present study was to investigate the genetic structure, connectivity and demographic history of the longnosed skate in Sardinia (western Mediterranean Sea).
2. Patterns of population structure were assessed in 175 specimens from six sampling sites. Variation in two mitochondrial genes (cytochrome c oxidase subunit I (COI) and control region) highlighted high genetic diversity and low but significant genetic differentiation among sites, which clustered into three groups corresponding to the north‐west, north‐east and south Sardinian coasts.
3. The observed genetic structuring could presumably depend on a combination of past geological events, contemporary restrictions to dispersal and biological characteristics of the species (e.g. site‐fidelity, no pelagic larval stage, limited dispersal of juveniles and/or adults).
4. Demographic analyses showed signs of past population expansion, but substantial current stability of Sardinian populations. From a conservation perspective, these results are encouraging, and indicate that Sardinian populations are still large and stable, and seem not to have suffered negative side‐effects from the ever‐growing fishing pressure in the region.
5. The occurrence of genetic structuring strongly supported the close monitoring of populations to identify any erosion of their gene pool, and high genetic variability of the Sardinian D. oxyrinchus populations could thus represent priority populations for conservation purposes, providing potential sources for recolonization in cases of local extinctions in other areas of the distribution range of the species.
6. When the sequences from Sardinia were compared with those available from other areas, the data seem to exclude the possibility that the Atlantic and Mediterranean host totally isolated populations or even different species, as recently suggested. However, additional markers and a larger sampling sites are needed to confirm these findings.

     

Effect of Marcela Extract (Achyroclines satureiodes) on the Shelf Life of Minced Tilapia (Oreochromis niloticus) Sausages

The effect of marcela extract (ME) on the shelf life of minced tilapia sausages was evaluated in this study. The level of phenolic compounds in the ME was 114.1 ± 2.9 mg GAE/g extract, and the DPPH free radical scavenging activity was 94.95 ± 1.34%. The ME protected the samples from color changes during storage. The addition of 0.5 and 0.75% ME significantly decreased lipid oxidation and microbial growth. The ME did not impact the sausages’ sensory quality, and the addition of 0.75% prevented sensory rejection during storage.     

The Effect of K-Lactate Salt and Liquid Smoke on Bacterial Growth in a Model System

The effects of a commercial lactate salt formulation—containing potassium lactate (KL) and potassium acetate (KA)—and liquid smoke (LS) on the growth of selected lactic acid bacteria (LAB; Carnobacterium maltaromaticum, Carnobacterium inhibens, Lactococcus lactis, Lactobacillus curvatus, and Enterococcus faecalis), fish spoilage bacteria (Photobacterium phosphoreum, Pseudomonas putida, and Vibrio vulnificus), and Listeria innocua, were examined in a tryptic soy broth model system at 20ºC based on BioScreen data. The most pronounced inhibition effect on growth of bacteria was seen in the presence of 6% KL + 0.4% KA, used either combined with LS or alone. Only a minor inhibition effect on growth was found in the presence of LS alone. The only exception was Lactobacillus curvatus, which grew quite well in the presence of LS compared to control medium. The growth of Vibrio vulnificus was prevented in 6% KL + 0.4% KA, and significantly inhibited in the presence of 3% KL + 0.2% KA. When V. vulnificus was grown in NaCl, KA, and KL + KA, it was observed that KL + KA had a better inhibition effect than sodium salt within the same concentration range.     

Genetic differentiation between and within ecotypes of pike (Esox lucius) in the Baltic Sea

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东海细点圆趾蟹数量分布的研究

本文依据1998年5月(春)、8月(夏)、11月(秋)和1999年2月(冬)在东海26°00’-33°00’N,127°00’E以西海域的蟹类资源调查资料,分析了东海细点圆趾蟹(Ovalipes punctatus)数量分布特征。结果表明:春、夏、秋和冬季调查海域细点圆趾蟹平均资源密度重量和个体数分别为65.00 kg·km-2、2076 ind·km-2,43.71 kg·km-2、395 ind·km-2,26.27 kg·km-2、643 ind·km-2和0.36 kg·km-2、7 ind·km-2。冬春季,东海北部近海细点圆趾蟹重量占蟹类总重量的一半以上,出现率和优势度远远高于其它水域,以产卵群体为主,是目前细点圆趾蟹最大的生产渔场。东海南部近海80-120m水深和北部外海80 m以深海域,各有一个细点圆趾蟹的高数量分布区。细点圆趾蟹的生产旺汛在春季的3-6月。夏季由于该种渔获个体规格和经济价值较高,加上有一定的资源密度,也是较好的捕捞季节。该种虽然能够适应广泛的温度和盐度,但具有明显的温水种特征,在东海北部近海又具有较低盐度的分布趋向性。     

Effects of light and artificial fish shelter (PVC pipe) on some phenotypic traits of stinging catfish (Heteropneustes fossilis Bloch, 1794)

Light and shelter are very important ecological factors that can affect many traits of fish. Therefore, a study was conducted to explore the effect of light and shelter on some phenotypic traits of stinging catfish (Heteropneustes fossilis Bloch, 1794). During experiment, equal‐sized juveniles (mean ± SE: 9.04 ± 0.09 cm) were collected and reared in aquariums dividing into four treatment groups, such as T₁ (0L:24D without pipe), T₂ (0L:24D with pipe), T₃ (12L:12D without pipe) and T₄ (12L:12D with pipe). Each treatment had 36 fish, which were randomly distributed into three replications. The fish were kept up to 120 days, and then, the growth performance and skin colour were analysed. The results showed that both lighting and shelter conditions as well as their interactions had significant effects on some traits expression. The analyses revealed that lighting condition significantly influenced body area, head width and skin coloration, while shelter condition significantly affected total and standard length, body area, and their interaction showed significant effects on body area, head width and anal fin length. Thus, this study indicates that stinging catfish show better growth performance and colour patterns especially in dark and sheltered conditions which could be recommended for the successive production of this highly priced fish species.     

Effect of Liquid Smoke Dipping and Packaging Method on the Keeping Quality of Raw and Cooked Chub Mackerel (Scomber japonicus) Fillets

Changes in biochemical and sensory attributes of chub mackerel (Scomber japonicus) fillets during storage treated by immersion in a 12% NaCl brine with or without 0.2% liquid smoke were investigated. Brine-treated chub mackerel fillets were packaged in modified atmosphere or under vacuum and were stored at 4°C. The brined fillets were stored and evaluated raw and after heat treatment as cooked samples. Fish fillets were assessed organoleptically to determine acceptability and by measuring the pH, oxidation levels (TBARS test), and total volatile basic nitrogen (TVBN). Fillets treated in brine with liquid smoke exhibited similar pH and significantly lower TBARS and TVBN values (p < 0.05). The combination of the use of brines containing liquid smoke and subsequent vacuum packaging produced the lowest TBARS and TVBN values and resulted in extended acceptability.     

Hazardous effect of ZnS nanoparticles on the feeding behaviour,growth and maturation process of the Asian striped catfish,Mystus vittatus (Bloch, 1794)

The Asian striped catfish Mystus vittatus (Bloch) are exposed to ZnS nanoparticles of different concentrations and its impact on feeding behaviour, growth and maturity of the fish is studied. The study reveals the fact that under nanoparticle exposure, the feeding behaviour, growth and maturation stages depart from that of the controlled conditions. The growth is found to be restricted with increasing nanoparticle concentration. Gonadal maturity has also found to be constrained with increasing nanoparticle concentrations up to a certain level. These effects are found to be more pronounced for nanoparticles of smaller sizes. The observations are explained on the basis of the enhanced photo-oxidation property of the ZnS nanoparticles.     

Combined Effect of Ozonized Water Pretreatment and Ozonized Flake Ice on Maintaining Quality of Japanese Sea Bass (Lateolabrax japonicus)

The effect of the combined application of ozonized water pretreatment and ozonized flake ice (O+OIce) as compared with traditional flake ice (CK), ozonized flake ice (OIce), and ozonized water pretreatment and traditional flake ice (O) was investigated for the storage of Japanese sea bass. Microbiological, chemical, and sensory analysis and moisture content were carried out throughout a storage period of 18 days. A slower increase of total viable mesophilic count (TVC), total volatile base nitrogen (TVB-N), and thiobarbituric acid reactive substances (TBARS) was observed for O+OIce as compared with OIce, O, and CK. Treatment of O+OIce also allowed a better control of pH as compared with OIce, O, and CK. None of the treatments resulted in a significant difference in myofibrillar protein extractability and moisture content. The shelf life of Japanese sea bass treated with CK, OIce, O, and O+OIce, determined by sensory evaluation, was 9, 15, 12, and more than 18 days, respectively. Principal component analysis results showed that the treatments significantly affected the fish quality during storage, and the sensory attributes had a significant correlation with TVB-N, TVC, and TBARS. In conclusion, the combined application of ozonized water and ozonized flake ice had the best effect on fish quality maintenance.     

Non-stationary effects of multiple drivers on the dynamics of Japanese sardine (Sardinops melanostictus,Clupeidae)

Non-stationary driver-response relationships are increasingly being recognized by scientists, underlining that a paradigm shift out of conventional stationary relationships is crucial. Japanese sardine (Sardinops melanostictus, Clupeidae) is a typical small pelagic fish in the northwestern Pacific with considerable fluctuations in productivity, bringing about great economic and ecological concerns. Numerous studies suggest that the population dynamics of Japanese sardine is an integrated process affected by multiple density-dependent, fishing and climatic drivers. However, little has hitherto been done to incorporate the non-stationary effects of multiple drivers, impeding progresses in understanding the population dynamics and in developing management strategies. In this study, we adopted variable coefficients generalized additive models to reveal the non-stationary effects of density dependence, fishing pressure and climatic conditions on the population dynamics of Japanese sardine. Results suggest that the dynamics of Japanese sardine from 1976 to 2018 could be divided into four periods: the 1980s when suitable climatic conditions from strong Siberian High pressure system sustained high abundance; the 1990s when negative density-dependent effects and degrading climatic conditions due to temperature increase led to population collapse; the 2000s when negative triple effects, particularly high fishing pressure, restricted the population increase; and the 2010s when favourable climatic conditions with re-strengthening Siberian High pressure system accompanied by low fishing pressure contributed to the population recovery. The study highlights that precise identifications of population status and climatic conditions are helpful to achieve good trade-offs between resource exploitation and protection and to facilitate ecosystem-based management for Japanese sardine fisheries.     

Influence of Electronarcosis on Behavioral Responses,Blood Markers,and Fillet Properties of Silver Catfish (Rhamdia quelen)

Behavioral responses, blood markers, and fillet properties were investigated after silver catfish exposure to different electric field strengths, frequency, and duration of electric current in the preslaughter stunning. All combinations of electric fields and frequencies were able to stun fish. Longer apparent stun was obtained at the intermediate electrical frequencies. High electric field strength detracted the texture of fillets. At least 5 s was required to stun fish, and longer exposure to electrical current did not prolong the apparent stun or damage fillet properties. Results indicate that silver catfish are relatively resistant to electronarcosis.     

Biochemical impacts of salinity on the catfish,Heteropneustes fossilis (Bloch, 1794), and possibility of their farming at low saline water

Although a stenohaline freshwater fish, the stinging catfish Heteropneustes fossilis, is also available in the freshwater fringes of the coastal areas of Bangladesh, the tolerance of this species to variable environmental salinity has not been thoroughly investigated. Based on median lethal salinity (MLS‐50 96 h), three sublethal salinity levels (3 ppt, 6 ppt and 9 ppt) and a control (0 ppt), each with three replications were selected to observe the effects of mildly brackish conditions on the fish for a period of 90‐day exposure. Better growth and survival were found up to 6 ppt compared with control. Salinity more than 6 ppt appeared unsuitable for H. fossilis fingerling due to increased mortality and reduced growth. To determine biochemical alterations, a few important physiological parameters were observed after 90 days of exposure. Glycogen level of liver and muscle in the fish reared at 9 ppt salinity decreased significantly (P < 0.05) as compared to the control. Glucose level in blood and liver was also found to be increased in fish with increase in salinity. ALP and ATPase activities were reduced significantly in both muscle and liver tissues at higher salinity, indicating the stress mitigation effect. However, all the biochemical parameters were found in normal condition up to 6 ppt compared with control. This evidence suggests that H. fossilis can sustain and grow well below 6 ppt and can be a potential candidate for culture in coastal areas after heavy downpour when the salinities level falls to 6 ppt or lower.     

Determinants of adoption behaviour of the fish farmers of Pabda fish culture (Ompok bimaculatus Bloch, 1794) in Tripura,Northeast India

Aquaculture International - Most of the adoption studies in catfish culture were restricted to feeding habits, growth rate and morphological studies, neglecting the social factors and adoption of...     

A review of sawfishes (Pristidae) in the Arabian region: diversity,distribution, and functional extinction of large and historically abundant marine vertebrates

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Feed Formulation Using Linear Programming for Fry of Catfish,Milkfish, Tilapia,Asian Sea Bass,and Grouper in India

Nutritional profiles of 25 feed ingredients available in India were selected and compiled. Their costs were ascertained from Cochin (SW), Tuticorin (SE), and Bhubaneswar (NW), where fish/shrimp farming is traditionally practiced. Least-cost feed formulations (using the linprog toolbox in Matlab software) were attempted for catfish, milkfish, tilapia, and grouper fry specifying levels of four critical limits: Ca/P ratio, digestible energy (DE), 10 amino acid levels (where data was available), and 10 ingredients, totaling 26 constraining limits to the model. Feeds formulated for catfish fry cost US$0.066 kg^?1 at Bhubaneswar, US$0.117 kg^?1 at Tuticorin, and US$0.153 kg^?1 at Cochin, with poultry by-product meal and hydrolyzed feather meal as the major ingredients; limiting amino acids in these feeds were methionine and phenylalanine. Feeds formulated for milkfish fry cost US$0.110 kg^?1 at Cochin, US$0.108 kg^?1 at Tuticorin, and US$0.072 kg^?1 at Bhubaneswar; the limiting amino acids in this case were histidine and threonine. The cost of feeds for tilapia fry was US$0.207 kg^?1 at Cochin, US$0.369 kg^?1 at Tuticorin, and US$ 0.114 kg^?1 at Bhubaneswar; the limiting amino acid was methionine. Feed formulae for fry of Asian sea bass had an LP solution containing only five ingredients for all three places. The feed formula was the same for Cochin and Bhubaneswar market prices, and the total cost of ingredients was US$0.274 kg^?1 and US$0.142 kg^?1, respectively. At Tuticorin market prices, the feed formula cost was US$0.397 kg^?1. The feed formulae for grouper fry at Bhubaneswar and Tuticorin market prices had the same three ingredients costing US$0.114 kg^?1 and US$0.321 kg^?1, respectively, whereas feed formula for Cochin market price consisted of four ingredients costing US$0.280 kg^?1.