Mortality In Marine Fish Research Articles

Opportunities to Improve the Ecological Competence of Students in the Secondary School Physics Course

This article shows ways to improve environmental competence with an elective physics course. Climate and other impacts of human activity on a planetary scale have now led us to understand the need to manage resource use on a global scale. Including ecosystem-linked greenhouse gases, carbon dioxide, methane, ozone depletion, near-surface temperatures, ocean acidification, mortality of marine fish, oxygen depletion from the discharge of reactive nitrogen into coastal waters, deforestation, conversion of natural ecosystems to agriculture and loss of terrestrial biodiversity. And the study of the physical, chemical, biological factors of these phenomena is within the competence of the natural sciences. On the basis of research, various directions for improving environmental education of students are still proposed, as well as few calls for environmental protection through the teaching of natural science subjects, including physics. Basically, the study of the main problems of technology in accordance with modern scientific and technological progress is carried out through this subject of physics, and students need to know what impact these technological processes have on human health from the point of view of the subject of physics, that is, how harmful they are. The purpose of this study is to provide the content and methodology of the elective course for the scientific and theoretical justification of environmental education of students through the teaching of physics in secondary school, as well as to increase environmental competence in the educational process organized on the subject “Physics”. Due to the limited number of hours devoted to teaching the subject, it is necessary to consider ways to develop environmental knowledge and ideas of students in extracurricular activities. One of them is an elective course. The proposed elective course helps students to increase their activity in environmental work, independent research, the desire to protect the environment and the worldview of the natural environment. The elective course offers thematic planning, teaching methods and various forms of conducting lessons on electrodynamics. In addition, this elective course provides great opportunities for the development of students' creative abilities, the formation of a personality that is well versed in physical and technical principles and environmental issues of the electric power industry. The article will be of interest to scientists, methodologists and everyone involved in the modernization of society.

Development of a Propidium Monoazide-Based Viability Quantitative PCR Assay for Red Sea Bream Iridovirus Detection

Red sea bream iridovirus (RSIV) is an important aquatic virus that causes high mortality in marine fish. RSIV infection mainly spreads through horizontal transmission via seawater, and its early detection could help prevent disease outbreaks. Although quantitative PCR (qPCR) is a sensitive and rapid method for detecting RSIV, it cannot differentiate between infectious and inactive viruses. Here, we aimed to develop a viability qPCR assay based on propidium monoazide (PMAxx), which is a photoactive dye that penetrates damaged viral particles and binds to viral DNA to prevent qPCR amplification, to distinguish between infectious and inactive viruses effectively. Our results demonstrated that PMAxx at 75 μM effectively inhibited the amplification of heat-inactivated RSIV in viability qPCR, allowing the discrimination of inactive and infectious RSIV. Furthermore, the PMAxx-based viability qPCR assay selectively detected the infectious RSIV in seawater more efficiently than the conventional qPCR and cell culture methods. The reported viability qPCR method will help prevent the overestimation of red sea bream iridoviral disease caused by RSIV. Furthermore, this non-invasive method will aid in establishing a disease prediction system and in epidemiological analysis using seawater.

Characterization of a virulent ranavirus isolated from marine ornamental fish in India.

A viral agent implicated in the mortality of marine ornamental "Similar Damselfish" (Pomacentrus similis Allen, 1991) was isolated and characterized. The virus grew well in marine and freshwater fish cell lines from seabass and snakehead. The virus was sensitive to chloroform, acidic pH (3.0) and heat treatment at 56°C. Biochemical characterisation indicated that the virus had double stranded DNA genome. Transmission electron microscopic analysis of ultrathin sections of infected cell pellets showed iridovirus-like icosahedral virus particles of 120-130nm. Purified virus had six structural protein bands that ranged from of 44 to 132kDa. PCR analysis confirmed the presence of viral DNA in infected cell cultures and sequence analysis of the major capsid protein gene showed an identity of 99.82% to that of largemouth bass virus. Serum neutralization studies involving the viral agent and koi ranavirus (KIRV) indicated partial homogeneity between the two isolates. Experimental infection of seabass (Lates calcarifer) and similar damselfish (P. similis) fingerlings with the similar damselfish virus showed cumulative mortalities of 68.75 and 93.33%. The biophysical and biochemical properties of the viral agent isolated, serological characteristics, size of major capsid proteins and the sequence similarity of the MCP gene proved that the virus belongs to the genus Ranavirus of the family Iridoviridae. Ability of the virus to grow in marine and freshwater fish cell lines and its pathogenicity to one of the cultivable marine fish shows the wide host range of the virus. This is the first report of ranavirus induced mortality in marine fish in India.

THE EFFECTS OF CRUDE RECOMBINANT VIRAL PROTEIN VACCINES AGAINST GROUPER SLEEPY DISEASE IRIDOVIRUS (GSDIV) ON HUMPBACK GROUPER (Cromileptes altivelis)

Infection of Megalocytivirus cause serious mass mortality in marine fish in South East Asian countries. The aim of this study was to produce recombinant of GSDIV capsid protein and its protection to humpback grouper Cromileptes altivelis against grouper sleepy disease iridovirus (GSDIV). A major capsid protein (MCP) was selected for use as a crude subunit vaccines. This gene target (MCP) was inserted to the protein expression system vector of pET SUMO and cloned in cells bacteria Escherichia coli strain BL-21. The MCP was succeded to be induced using 1 mM of IPTG. Results of protein analysis using MALDI TOF-TOF indicated that the MCP has measurement of 49.566 kDa with PI index of 6.00, and contained 453 amino acids. BLAST homology analysis exhibited that the amino acid sequence of the MCP showed high similarity with MCP of Red Sea Bream Iridovirus (RSIV). E. coli expressing MCP protein was inactivated using 0.03% formalin overnight and washed using PBS. The inactivated E. coli as a crude subunit vaccine was then injected intramuscularly to humpback grouper juveniles. Subsequently, the juveniles were challenged tested with GSDIV. The juveniles vaccinated with the MCP recombinant bacteria showed significantly higher survival rates than control those vaccinated with PBS. Thus, the MCP fusion protein is considered as a potential vaccine against GSDIV infections in grouper.

Diagnosis of nervous necrosis virus in orange-spotted grouper, Epinephelus coioides, by a rapid and convenient RT-PCR method

Viral nervous necrosis (VNN) causes high mortality in marine fish, especially in the grouper, worldwide and in China. Since there is no effective vaccine or drug to deal with VNN, early detection and prevention is important to block its outbreak. In this study, a reverse transcription-polymerase chain reaction (RT-PCR) was developed for the rapid, convenient, and sensitive detection of the VNN pathogen, nervous necrosis virus (NNV), in the grouper. The whole process was completed within 3.5 h from the RNA extraction to PCR product visualization. The detection limit of this method was 200 copies of NNV RNA standard, which corresponded to 200 copies of virus particles. This RT-PCR method was specific to the NNV detection with no cross-reactivity to other fish viral disease pathogens, such as infectious pancreatic necrosis virus (IPNV), infectious hematopoietic necrosis virus (IHNV), spring viraemia of carp virus (SVCV), epizootic haematopoietic necrosis virus (EHNV), and large yellow croaker iridovirus (LYCIV). With this method, the orange-spotted grouper (Epinephelus coioides) fry from hatcheries with or without incidence of the VNN epidemic in Fujian Province were detected. The results showed that all or 93% of the fry from the two hatcheries with incidence of the epidemic were diagnosed as positive, while 40% or 25% of fry from the two hatcheries without the VNN epidemic were also detected as NNV positive, indicating that this RT-PCR method can be used for rapid, sensitive detection of NNV infection and applied in the VNN epidemic alert.

Characteristics of survivors: growth and nutritional condition of early stages of the hake species Merluccius paradoxus and M. capensis in the southern Benguela ecosystem

Abstract Grote, B., Ekau, W., Stenevik, E. K., Clemmesen, C., Verheye, H. M., Lipinski, M. R., and Hagen, W. 2012. Characteristics of survivors: growth and nutritional condition of early stages of the hake species Merluccius paradoxus and M. capensis in the southern Benguela ecosystem. – ICES Journal of Marine Science, 69: 553–562. Larval mortality in marine fish is strongly linked to characteristic traits such as growth and condition, but the variability in these traits is poorly understood. We tried to identify the variability in growth in relation to conditions leading to greater survival chances for early stages of Cape hake, Merluccius paradoxus and M. capensis, in the Benguela upwelling ecosystem. During two cruises in 2007 and one cruise in 2008, hake larvae and juveniles were caught. Otolith microstructures revealed a larval age ranging from 2 to 29 days post-hatching (dph), whereas juvenile age was 67–152 dph. RNA:DNA ratios, used to evaluate nutritional condition, were above the relevant threshold level for growth. No strong coupling between growth and condition was detected, indicating a complex relationship between these factors in the southern Benguela ecosystem. Merluccius paradoxus juveniles caught in 2007 (the surviving larvae of 2006) had significantly higher larval growth rates than larvae hatched in 2007 and 2008, possibly indicating selection for fast growth in 2006. High selection pressure on growth could be linked to predation avoidance, including cannibalism.

Reef fish mass mortality event in an isolated island off Brazil, with notes on recent similar events at Ascension, St Helena and Maldives

Events of mass mortality of marine fish have been reported to occur world wide, mainly in coastal regions of continental shelves. Here we report an event at Trindade Island, located 1160 km from the Brazilian coast. Melichthys niger was the species most commonly seen affected. Twenty-four other species were found washed ashore. Victims were demersal (72% of species), pelagic (20%) and benthonic species (8%), comprising eight trophic categories. There is evidence that fish kills have occurred at Trindade since at least the 1990s. Mortality events mainly involving primarily Balistidae (Trindade, Maldives and Ascension), Chaetodontidae (St Helena) and Serranidae (Ascension) have been reported for other isolated oceanic localities with low human occupation. It is possible that blooms of toxic algae, under certain conditions cause cascading intoxication along the trophic web. A second hypothesis is that seasonal upwelling events of anoxic or hypoxic waters may be implicated.

Protection of red sea bream Pagrus major against red sea bream iridovirus infection by vaccination with a recombinant viral protein

Megalocytivirus infections cause serious mass mortality in marine fish in East and Southeast Asian countries. In this study the immunogenicity of crude subunit vaccines against infection by the Megalocytivirus RSIV was investigated. Three capsid proteins, 18R, 351R and a major capsid protein, were selected for use as crude subunit vaccines. High homology among Megalocytivirus types was found in the initial sequence examined, the 351R region. Red sea bream (Pagrus major) juveniles were vaccinated by intraperitoneal injection of recombinant formalin-killed Escherichia coli cells expressing these three capsid proteins. After challenge infection with RSIV, fish vaccinated with the 351R-recombinant bacteria showed significantly greater survival than those vaccinated with control bacteria. The 351R protein was co-expressed with GAPDH from the bacterium Edwardsiella tarda in E. coli; this also protected against viral challenge. A remarkable accumulation of RSIV was observed in the blood of vaccinated fish, with less accumulation in the gills and spleen tissues. Thus, the 351R-GAPDH fusion protein is a potential vaccine against Megalocytivirus infection in red sea bream.

Maternal and paternal effects determine size, growth and performance in larvae of a tropical reef fish

Larval mortality in marine fishes is strongly linked to individual life history traits such as size and growth, but the processes that influence variability in these traits are poorly understood. We explore the relative importance of maternal and paternal influences and water temperature on the larval growth and performance characteristics of the tropical clownfish Amphiprion melanopus (Pomacentridae). Larvae were reared from an incomplete 4 male × 4 female diallel breeding cross at 2 temperatures (25 and 28°C). Paternity interacted with maternity and affected traits immediately prior to and after hatching. Size of larvae at metamorphosis was primarily affected by maternal and paternal influences, but not by rearing temperature. Paternity explained 52% of the variance in growth rates to metamorphosis, while the combination of paternity, maternity and temperature explained 30%. This strong paternal influence may be due to the extensive role males play in nest-tending coupled with the relatively long embryonic duration of the species. A negative relationship between larval growth rate and mortality within a tank emphasised the importance of these parental effects to larval survival and also provides support for the ‘bigger is better’ hypothesis.

Injury and Mortality Induced by Four Hook Types on Bluegill and Pumpkinseed

Tackle manufacturers have responded to concerns regarding hooking injury and mortality by attempting to design and market hooks that are less damaging to fish (e.g., circle hooks). To date, studies investigating circle hooks have been primarily restricted to large marine species. We compared the injury and short-term (72-h) mortality of bluegills Lepomis macrochirus and pumpkinseeds L. gibbosus angled using number-6 circle hooks and three other conventional hook types (aberdeen, wide-gap, and baitholder) across three water temperatures (18, 22, and 26°C). Unlike other hook types, circle hooks were never lodged in the gullet, but they were frequently lodged in the eye. Some fish captured on conventional hooks were hooked deeply in the gullet, necessitating line cutting for release. Incidences of bleeding were low using all hook types, and when not lodged in the gullet, all hooks were generally easy to remove. Anatomical hooking locations differed among small (<145-mm) and large (>145-mm) bluegills for all hook types but not among pumpkinseeds. Hooking depth differed between small and large fish of both species captured on circle hooks; smaller fish were hooked more deeply. Mortality in both species was negligible at all water temperatures except for bluegills at 26°C (3% mortality). Bluegills that died were smaller than those that survived. Our results confirm the supposition that circle hooks are less susceptible to deeply hooking fish in the gullet. However, circle hooks permanently impaired vision of up to 22% of the fish, much more than for other hooks types. Although efficient at minimizing injury and mortality in marine fish, our study suggests that circle hooks perform similarly to more conventional hook types in fisheries for small sunfish.

Hypothermal Mortality in Marine Fishes of South-Central Florida, January, 1977

Comparable climatic conditions on both coasts of central Florida resulted in cold induced fish mortalities from 19 January to 13 February 1977. Lethal temperatures, the species killed and their relative numbers killed are compared for the Indian River lagoon, Tampa Bay and Sanibel Island estuarine systems. Fifty-six species were killed in the Indian River area, 36 in the Tampa Bay area, while 19 died at Sanibel Island. The higher species mortality in the Indian River lagoon may be attributed to local hydrological and topographical conditions-and a richer ichthyofauna. Cold-induced mortality was noted in both juvenile and adult tropical fishes. Some tropical species appear to be more eurythermic than others as lethal minimum temperatures ranged from 6 to 13 C. Hypothermal stress and mortality were observed in offshore reef fishes.

Larval mortality in marine fishes and the critical period concept

Larval mortality in marine fishes and the critical period concept