Competitive interactions under experimental conditions affect diel feeding of two common aquaculture fish species Labeo calbasu (Hamilton, 1822) and Cirrhinus cirrhosus (Bloch, 1795) of southern Asia

The effects of interspecific competition on grazing between two important aquaculture species, mrigal carp Cirrhinus cirrhosis and orangefin labeo Labeo calbasu, in single and in dual combinations were observed in experimental tanks. This study demonstrated that the presence of a competitor did not cause C. cirrhosis to shift its diel feeding patterns. That said, both total food intake and food preference were negatively affected in C. cirrhosis by the presence of a superior competitor, L. calbasu. The feeding patterns of L. calbasu became diurnal in the presence of C. cirrhosus, suggesting highly complex competitive interactions between the two species. That L. calbasu was specifically able to shift circadian feeding patterns to maximize energy intake in the presence of a competitor would suggest that it would be a suitable species to stock in a mixed species aquaculture system

Common carp (Cyprinus carpio L.) alters its feeding niche in response to changing food resources: direct observations in simulated ponds

We used customized fish tanks as model fish ponds to observe grazing, swimming, and conspecific social behavior of common carp (Cyprinus carpio) under variable food-resource conditions to assess alterations in feeding niche. Different food and feeding situations were created by using only pond water or pond water plus pond bottom sediment or pond water plus pond bottom sediment and artificial feeding. All tanks were fertilized twice, prior to stocking and 2 weeks later after starting the experiment to stimulate natural food production. Common carp preferred artificial feed over benthic macroinvertebrates, followed by zooplankton. Common carp did not prefer any group of phytoplankton in any treatment. Common carp was mainly benthic in habitat choice, feeding on benthic macroinvertebrates when only plankton and benthic macroinvertebrates were available in the system. In the absence of benthic macroinvertebrates, their feeding niche shifted from near the bottom of the tanks to the water column where they spent 85% of the total time and fed principally on zooplankton. Common carp readily switched to artificial feed when available, which led to better growth. Common carp preferred to graze individually. Behavioral observations of common carp in tanks yielded new information that assists our understanding of their ecological niche. This knowledge could be potentially used to further the development of common carp aquaculture

Influences of environmental parameters and phytoplankton productivity on benthic invertebrates in a tropical oligotrophic lake, northern Malaysia

Studies that associate environmental parameters with aquatic organisms in man-made lakes remain limited by accessibility and interest particularly in many Asian countries.Withmissed opportunities to monitor environmental transitions at Lake Kenyir, our knowledge of lake transition is restricted to the non-mixing shallow waters only. Triplicate monthly benthic invertebrate samples were collected concurrentlywith various environmental parameters at three locations (zonesA–C) of Kenyir Lake,Malaysia. Our results affirmed that the northeast part of Lake Kenyir is oligotrophic. Abundance of phytoplankton, total suspended solids, phosphate, nitrite and nitrate drive the abundance of various groups of benthic invertebrates. All of these extrinsic variables (except phosphate) negatively influenced the density of Trichoptera and positively influenced (P<0.05) the densities of Polychaeta, Oligochaeta, Bivalvia, Gastropod, Isopoda and Copepod in all zones. Phosphate negatively influenced the density of Trichoptera and positively influenced (P<0.05) the densities of Oligochaeta, Bivalvia and Copepod. Its influences on the Polychaeta, Gastropod and Isopoda densities were zone-specific. Overall, seasons equally influenced the relationships between extrinsic and response variables in all zones. The results of this study are useful to evaluate the lake’s environmental quality, in conservation and in similar projects involving environmental handling, monitoring and recovery

Convalescent plasma in patients admitted to hospital with COVID-19 (RECOVERY): a randomised controlled, open-label, platform trial

SummaryBackground Azithromycin has been proposed as a treatment for COVID-19 on the basis of its immunomodulatoryactions. We aimed to evaluate the safety and efficacy of azithromycin in patients admitted to hospital with COVID-19.Methods In this randomised, controlled, open-label, adaptive platform trial (Randomised Evaluation of COVID-19Therapy [RECOVERY]), several possible treatments were compared with usual care in patients admitted to hospitalwith COVID-19 in the UK. The trial is underway at 176 hospitals in the UK. Eligible and consenting patients wererandomly allocated to either usual standard of care alone or usual standard of care plus azithromycin 500 mg once perday by mouth or intravenously for 10 days or until discharge (or allocation to one of the other RECOVERY treatmentgroups). Patients were assigned via web-based simple (unstratified) randomisation with allocation concealment andwere twice as likely to be randomly assigned to usual care than to any of the active treatment groups. Participants andlocal study staff were not masked to the allocated treatment, but all others involved in the trial were masked to theoutcome data during the trial. The primary outcome was 28-day all-cause mortality, assessed in the intention-to-treatpopulation. The trial is registered with ISRCTN, 50189673, and ClinicalTrials.gov, NCT04381936.Findings Between April 7 and Nov 27, 2020, of 16 442 patients enrolled in the RECOVERY trial, 9433 (57%) wereeligible and 7763 were included in the assessment of azithromycin. The mean age of these study participants was65·3 years (SD 15·7) and approximately a third were women (2944 [38%] of 7763). 2582 patients were randomlyallocated to receive azithromycin and 5181 patients were randomly allocated to usual care alone. Overall,561 (22%) patients allocated to azithromycin and 1162 (22%) patients allocated to usual care died within 28 days(rate ratio 0·97, 95% CI 0·87–1·07; p=0·50). No significant difference was seen in duration of hospital stay (median10 days [IQR 5 to >28] vs 11 days [5 to >28]) or the proportion of patients discharged from hospital alive within 28 days(rate ratio 1·04, 95% CI 0·98–1·10; p=0·19). Among those not on invasive mechanical ventilation at baseline, nosignificant difference was seen in the proportion meeting the composite endpoint of invasive mechanical ventilationor death (risk ratio 0·95, 95% CI 0·87–1·03; p=0·24).Interpretation In patients admitted to hospital with COVID-19, azithromycin did not improve survival or otherprespecified clinical outcomes. Azithromycin use in patients admitted to hospital with COVID-19 should be restrictedto patients in whom there is a clear antimicrobial indication

Biology of common carp in natural and farmed habitats from a global perspective

Common carp (Cyprinus carpio L.) is an important food fish in many Asian and European countries, where it is considered as an important aquaculture species. Common carp account for approximately 4.1% of the total global aquaculture production and 9% of the global freshwater aquaculture production. The bulk of world’s common carp production (97%) comes from aquaculture. It is the most cultured fish species in Central and Eastern Europe, with production levels reaching more than 80% of total fish production in some countries. Aquaculture of this species is not observed in North America, New Zealand and Australia, where it is considered as a potential invasive and noxious aquatic species. Common carp belongs to the largest family (Cyprinidae) of freshwater fishes in the world. Their high adaptive capacity in a wide range of conditions and habitats accounts for their widespread distribution in most countries of the world. Presently, two subspecies exist in the world: the Asian (C. carpio haematopterus) and the European subspecies (C. carpio carpio). Common carp live in lakes, ponds, reservoirs, natural depressions and rivers. They are bottom dwellers, generally prefering to live near the soft vegetated sediments. They prefer benthic organisms particularly chironomids, oligochaetes, gastropods and other larval insects available in and on the benthos of natural habitats. When preferred foods become depleted, they shift their food habits, feeding niche and behaviour. The behaviour of common carp is consistent with classical optimal foraging theory. They redily adapt when inter and intra–specific competition are pronounced. Common carp significantly influence the behavior of other species (e.g. Labeo rorita) without showing any aggressive interactions. This article reviews the origin, habitats, distribution, growth, production, food habit, spawning, maturation, fecundity and behaviour of common carp focusing through a global lens

Diseases of common carp and their control measures

Common carp (Cyprinus carpio L.) contribute significantly to global freshwater fish production but it may also play a significant role in the expansion of various parasitic fish diseases around the globe as many parasites were dispersed locally and internationally due to common carp trade. The production of common carp in natural habitats and in aquaculture farms often become threatened due to various factors including disease outbreaks. Disease increases the management costs as well as decreasing fish production. To prevent and control various diseases, it is important to understand the mechanism of disease outbreak, which generally involves a complex interaction among fish, pathogens and the environment. High stocking density, poor management practices and various environmental problems result in exposure of fishes to stress that often leads to disease. The disease can also be initiated by various biological agents, which can be prevented and controlled by effective management practises. Due to the preference of soft vegetated sediments as habitat, common carp is also susceptible to many pathogens (e.g., viruses, bacteria, fungi, parasites, etc.), which cause various diseases. A severe pathogenic infection may cause high mortality of fish. This paper reviews various diseases of common carp and their control measures