Bacterial population in intestines of white shrimp,Litopenaeus vannamei fed a synbiotic containing Lactobacillus plantarum and galactooligosaccharide

The aims of this study were to unravel the intestinal microbiota of Litopenaeus vannamei after being fed a diet without (control) or with the synbiotic (SYN) for 60 days using next‐generation sequencing technology to see if changes in the intestinal microbiota were involved in the improved growth performance and health status of the shrimp. Next‐generation sequencing data showed that six phyla, 11 classes, 19 orders, 30 families, 58 genera and 73 species with taxonomic names assigned were detected. The majority of the operational taxonomic units (OTUs) was shared between the SYN and control shrimp and comprised 37 OTUs. However, intestinal biodiversity analyses revealed that SYN‐fed shrimp had a higher species richness, evenness and Shannon–Weaver index than did shrimp fed the control diet, but without reaching statistical significance. Interestingly, shrimp fed the SYN diet exhibited improved colonization of Lactobacillus plantarum and reduced prevalences of Vibrio harveyi and Photobacterium damselae in the intestines. These findings indicate that the SYN was able to modulate the intestinal bacterial community of shrimp and could be used to control vibriosis in shrimp.     

Aeromonas salmonicida infection levels in pre‐ and post‐stocked cleaner fish assessed by culture and an amended qPCR assay

Due to increasing resistance to chemical therapeutants, the use of ‘cleaner fish’ (primarily wrasse, Labridae, species) has become popular in European salmon farming for biocontrol of the salmon louse, Lepeophtheirus salmonis (Krøyer). While being efficient de‐licers, cleaner fish mortality levels in salmon cages are commonly high, and systemic bacterial infections constitute a major problem. Atypical furunculosis, caused by Aeromonas salmonicida A‐layer types V and VI, is among the most common diagnoses reached in clinical investigations. A previously described real‐time PCR (qPCR), targeting the A. salmonicida A‐layer gene (vapA), was modified and validated for specific and sensitive detection of all presently recognized A‐layer types of this bacterium. Before stocking and during episodes of increased mortality in salmon cages, cleaner fish (primarily wild‐caught wrasse) were sampled and screened for A. salmonicida by qPCR and culture. Culture indicated that systemic bacterial infections are mainly contracted after salmon farm stocking, and qPCR revealed A. salmonicida prevalences of approximately 4% and 68% in pre‐ and post‐stocked cleaner fish, respectively. This underpins A. salmonicida's relevance as a contributing factor to cleaner fish mortality and emphasizes the need for implementation of preventive measures (e.g. vaccination) if current levels of cleaner fish use are to be continued or expanded.     

Intestinal microbiota of white shrimp,Litopenaeus vannamei,fed diets containing Bacillus subtilis E20‐fermented soybean meal (FSBM) or an antimicrobial peptide derived from B. subtilis E20‐FSBM

The purpose of the present study is to profile the microfloral structure in the intestines of the white shrimp, Litopenaeus vannamei, after being fed a control diet, in comparison with the diets containing Bacillus subtilis E20‐fermented soybean meal (FSBM) or an antimicrobial peptide (AMP) isolated from B. subtilis E20‐FSBM (diets designated FSBMD and AMPD, respectively) for 60 days. Metagenomic data showed detection of eight phyla, 20 classes, 40 orders, 68 families and 96 genera. Despite no statistically significant difference, an evaluation of microbial diversity recorded higher species richness, Shannon–Weaver diversity index and evenness in the AMPD and FSBMD groups, compared to the control diet group. Venn diagrams showed that 58 of the operational taxonomic units (OTUs) were shared among the control, FSBMD and AMPD groups, but additional beneficial microbes were only found in the FSBMD and AMPD groups. In addition to the augmentation of beneficial bacteria in the FSBMD and AMPD groups, the abundance of potential pathogens, Vibrio and Flavobacterium, was lower in the gut of shrimp fed the FSBMD and AMPD. The results clearly suggest that the FSBMD and AMPD have the capability to change the microfloral structure of shrimp intestines and could be used for disease prevention in shrimp aquaculture.     

Inbreeding and disease in tropical shrimp aquaculture: a reappraisal and caution

The disease crisis facing shrimp aquaculture may be propelled, in part, by an interaction between management practices that cause inbreeding, and the amplification by inbreeding of susceptibility to disease and environmental stresses. The study describes and numerically simulates gene flow from Penaeus (Litopenaeus) vannamei hatcheries that employ a ‘Breeder Lock’ to discourage use of their PL as breeders, through ‘copy hatcheries’ that breed the locked PL, to inbred shrimp in farm ponds. Re‐analysis of published data shows that inbreeding depression under stress is exceptionally strong in shrimp. Inbreeding is currently overlooked as a problem because: (1) procedures recommended for well‐managed hatcheries do not consider their implications for the copy hatcheries that supply most farmed shrimp (estimated 70%), (2) inbreeding in hatcheries is often reported as zero even though zero is the mathematical expectation of the usual estimator (Fis, fixation index) whatever the true genealogy of the broodstock. Simulation shows, however, that inbreeding can be estimated with Wang's trioML estimator, that Fis can differentiate Breeder Locked from copy PL and that simple tests can verify the lock status of PL. The importance of inbreeding should be re‐evaluated in the context of disease and environmental stress. Unrecognized inbreeding may increase the incidence, prevalence and lethality of WSSV, IHHNV, EMS (AHPND) and other diseases.     

Gut bacterial community profile in Pacific white shrimp Litopenaeus vannamei following 5‐aminolevulinic acid supplementation

Changes in the diet have been previously reported to alter the gut bacterial profile in several organisms, including shrimp. These shifts in microbial structure either promote beneficial effects to the host or cause diseases. Supplementation of 5‐aminolevulinic acid (5‐ALA), the precursor of tetrapyrroles, has been previously reported to enhance shrimp's immune response. To know whether 5‐ALA has effects on the gut bacterial structure in Pacific white shrimp (Litopenaeus vannamei), we investigated the bacterial communities in the intestine and stomach of L. vannamei using high‐throughput Illumina sequencing of 16S rRNA gene libraries. One week of 5‐ALA supplementation altered the bacterial community structure (beta diversity) in both tissues, as shown by the results of multi‐dimensional scaling (MDS) plots and analysis of similarities (ANOSIM). DESeq2 analysis revealed enrichment of differentially abundant taxa in the 5‐ALA group (e.g. Enhydrobacter and Oceaniovalibus) and control group (e.g. Tenacibaculum and Mycobacterium). Metagenomic predictions suggested that the control group had more KEGG pathways associated with ‘metabolism’ than the 5‐ALA group. This study suggests that 5‐ALA supplementation potentially promotes the formation of a beneficial bacterial community structure in shrimp. This is the first report on the effect of 5‐ALA supplementation on the bacterial community profile in any organism.     

A cost‐effectiveness analysis of live feeds in juvenile turbot Scophthalmus maximus (Linnaeus, 1758) farming: copepods versus Artemia

The biological benefits of copepods as live feed for marine finfish larvae have already been well established in the literature. Copepods have better biochemical compositions that improve growth, reduce malpigmentations and allow successful farming of ‘new’ marine finfish species. However, their current usage is quite limited. One of the reasons has been lack of economic knowledge concerning the cost‐effectiveness of copepod application compared to other commonly used feed items such as the brine shrimp Artemia. In this study, a cost‐effectiveness analysis is made on two alternative live feed items (copepods and Artemia) in juvenile turbot farming. Unit cost of production and profit are compared between the two feeding regimes using a unique data set from an existing turbot fry production facility in Denmark. The result reveals that copepods are not only biochemically superior but they are also economically a cost‐effective alternative. Thus, a commercial use of copepods will significantly reduce the production costs for turbot. Furthermore, the unexploited economic potential can be utilized for the successful farming of other high‐valued marine finfish species such as tuna, flounders, cod, sole and halibut. Generally, the biochemical superiority coupled with economic benefits can lead to the commercial utilization of copepods as complementary live feed in the short run and in some situations as a substitute in the long run.     

Can barber goby Elacatinus figaro control Neobedenia melleni infections on dusky grouper Epinephelus marginatus?

The interaction between cultured barber goby Elacatinus figaro (cleaner fish) and the dusky grouper Epinephelus marginatus, and the efficiency of the cleaner fish in removing ectoparasites were evaluated. When the interaction between these two species was observed, cleaner fish showed a preference for the largest groupers. In a second trial, treatments: TWC (Control) – two groupers without a cleaner fish, T1C – two groupers with one cleaner fish, T3C – two groupers with three cleaner fish and T6C – two groupers with six cleaner fish were tested in four replicates. After 8 days, monogeneans were removed and identified as Neobenedenia melleni. The highest mean abundance of parasites was found on the groupers in the TWC group (37 parasites per host) and the lowest on those in the T6C group (4.1 parasites per host). By increasing the number of cleaner fish, a higher cleaning efficiency was obtained, as observed in T6C, where almost 90% of the parasites were removed. Possibly, this removal would have been complete if the number of cleaners had not been reduced in the treatments due to the mortalities observed. This study demonstrates the possibility of using gobies to remove monogeneans and in improving grouper health.     

Influence of stocking density on the behaviour of juvenile Litopenaeus vannamei (Boone, 1931)

Applied ethology can help to improve Litopenaeus vannamei aquaculture. Our purpose was to demonstrate an influence of stocking density on behaviour. The shrimp were first distributed in aquaria and observed via an ad libitum observational method to construct an ethogram of social and feeding behavioural categories. The resulting ethogram consisted of retreat, cannibalism, getting to the feeding tray, occupying the feeding tray and getting feed. We then kept shrimp in aquaria at densities of 50, 75 and 100 animals m^?2 and observed them via a behavioural sampling method using our ethogram as well as focal animal sampling of behaviours derived from the literature. These literature‐derived behaviours consisted of inactivity, feeding, crawling, exploration, burying, swimming and cleaning. We found that stocking density affects the behaviour of the shrimp. Optimal searching and feeding and a low frequency of crawling and swimming occurred at a density of 50 animals m^?2, indicating a higher potential for growth and welfare at this density.     

Data quality and quantity for invasive species: A case study of the lionfishes

Predicting invasion risk involves inherent uncertainty when data on biological and ecological characteristics are lacking. To combat data gaps, assessors are required to use information from secondary sources, further reducing predictive accuracy. Lionfish in the subfamily Pteroinae have invasion history in the Western Atlantic Ocean and Mediterranean Sea, raising concern that other species of globally traded lionfish may pose risks similar to the invasive complex comprised of the red lionfish (Pterois volitans, Scorpaenidae) and devil firefish (Pterois miles, Scorpaenidae). We conducted a standardized literature review of 18 species in the genera Pterois, Dendrochirus, and Parapterois to (a) characterize the volume and composition of literature addressing the invasive complex pre‐establishment and pre‐spread, and compare it to the body of literature that has been generated post‐spread and impact, (b) compare the volume and composition of literature addressing other members of Pteroinae to the invasive complex, and (c) evaluate data quality addressing the Pteroinae by characterizing literature used to generate biological profile reports during a risk screening protocol. Little data were available for the invasive complex prior to introduction and focused primarily on the composition or effects of venom. Following introduction, there was a considerable time lag in research effort. Post‐spread, research effort increased rapidly. We identify similar data deficiencies for other species of lionfish that have not been reported outside of their native ranges. While proactive management is gaining support as an effective framework, it is important to understand data limitations and their resulting uncertainties, which leads to more informed proactive management.     

Piscirickettsia salmonis infection in cultured lumpfish (Cyclopterus lumpus L.)

A Piscirickettsia salmonis infection was diagnosed in lumpfish (Cyclopterus lumpus L.) juveniles held in a marine research facility on the west coast of Ireland. The main clinical signs and pathology included marked ascites, severe multifocal liver necrosis and severe diffuse inflammation and necrosis of the exocrine pancreas and peri‐pancreatic adipose tissue. Numerous Piscirickettsia‐like organisms were observed by histopathology in the affected organs, and the bacterial species was characterized by molecular analysis. Sequencing of the partial 16S rDNA gene and internal transcribed spacer region showed the lumpfish sequences to be closely related to previously identified Atlantic salmon (Salmo salar L.) sequences from Ireland. To the authors’ knowledge, this is the first detection of P. salmonis in lumpfish worldwide. The infection is considered potentially significant in terms of lumpfish health and biosecurity.     

Revealing the compositions of the intestinal microbiota of three Anguillid eel species using 16S rDNA sequencing

Anguilla japonica, A. marmorata and A. bicolor pacifica are important eel species for aquaculture in Taiwan. In the past, seldom studies focused on the intestinal microbiome of them or the probiotics used in their cultivation. Probiotics are microbes that can improve the health of organisms, and the microbes isolated from the intestines of organisms might be the potential probiotics. Therefore, the aim of this study was to collect the intestinal mucus samples of these three eel species for investigating the autochthonous microbiome using 16S rDNA sequencing. The diversity, abundance of the intestinal microbiome and compositions of all the libraries were identified. Moreover, the composition of intestinal microbiome of eel was suggested that it would be affected by the waters and the characteristics of different eel species. Furthermore, most of the identified predominant genera of the intestinal microbiome of these three eel species, such as Cetobacterium, Clostridium, Shewanella, Acinetobacter and Bacteroides, seemed to have great potential as the probiotics. In the future, more studies shall be conducted to promote the practical application of these candidate probiotics for improving the techniques of eel farming.     

Effect of green and clear water and lipid source on survival, growth and biochemical composition of Pacific white shrimp Litopenaeus vannamei

Despite the shrimp ability to obtain additional nutrients from food organisms endogenously produced within the ‘green water’ system has been suggested as one of the causes for the better performance of Pacific white shrimp reared in ‘green water’ in comparison with ‘clear water’, the nutritional components responsible for these effects have yet to be determined. The present study aims to understand the importance of natural food organisms in zero‐water exchange systems as source of essential fatty acids for the Pacific white shrimp Litopenaeus vannamei. Five treatments were tested: two conducted in mesocosms systems with shrimp‐fed diets containing either fish oil (FO) or olive oil, and another three conducted in clear water with shrimp‐fed diets containing either olive oil, a docosahexaenoic acid (DHA)‐rich oil or an arachidonic acid (ARA)‐rich oil. The presence of higher levels of fatty acids 16:1n‐7, 17:1, 20:4n‐6, 20:3n‐3 and 22:5n‐6, characteristic of floc lipids, in shrimp reared in mesocosms denoted their assimilation from the floc. Substitution of FO by olive oil in diets for shrimp reared in mesocosms did not affect growth or survival. Survival and growth of shrimp reared in mesocosms was better than those reared in clear water and fed an olive oil diet, whereas DHA or ARA enrichment of non‐fish oil (NFO) diet improved survival of shrimp reared in clear water. Higher survival rate, triglyceride and DHA content in whole body and eyes of shrimp fed a DHA‐rich diet suggests that under these conditions, in clear water, it is necessary to include at least 4.8 g kg^?1 DHA in diet dry weight. ARA enrichment seemed to negatively affect growth. The nutritional contribution of the floc to shrimp in mesocosm culture reduces or eliminates the need for a dietary source of FO and illustrates the importance of DHA and ARA to enhance shrimp survival in clear water conditions.     

Detection and molecular characterization of infectious spleen and kidney necrosis virus from major ornamental fish breeding states in Peninsular Malaysia

‘Gold standard’ OIE reference PCR assay was utilized to detect the presence of infectious spleen and kidney necrosis virus (ISKNV) in freshwater ornamental fish from Malaysia. From total of 210 ornamental fish samples representing 14 species, ISKNV was detected in 36 samples representing 5 fish species. All positive cases did not show any clinical signs of ISKNV. Three restriction enzymes analyses showed that the fish were infected by identical strains of the same virus species within Megalocytivirus genus. Major capsid protein (MCP) genes of 10 ISKNV strains were sequenced and compared with 9 other reference nucleotide sequences acquired from GenBank. Sequence analysis of MCP gene showed that all strains detected in this study were closely related to the reference ISKNV with nucleotide sequence identity that was ranging from 99.8% to 100%. In addition, phylogenetic analysis of MCP gene revealed that viruses from genus Megalocytivirus can be divided into three genotypes: genotype 1 include reference ISKNV and all other strains that were detected in this study, genotype 2 include viruses closely related to red sea bream iridovirus (RSIV), and genotype 3 include viruses closely related turbot reddish body iridovirus (TRBIV).     

Post‐hatching development of the ornamental ‘Red Cherry Shrimp’ Neocaridina davidi (Bouvier, 1904) (Crustacea,Caridea, Atyidae) under laboratorial conditions

The ‘Red Cherry shrimp’, Neocaridina davidi is a small freshwater caridean shrimp living, originally, in various kinds of inland water bodies around Asian countries. This shrimp has reached several countries for ornamental use; however, basic information on the biology of the species is still scarce in the literature. Its early post embryonic development morphology has not yet been described. This paper focused on the production and the development of early post‐hatching stages of N. davidi, its male secondary sexual features, observation of the gonads and the presence of females with embryos. The larval development of N. davidi was almost suppressed as noted by the presence of relatively large‐sized eggs, first stage hatching as a decapodid; and the tail fans were present only from the 2nd post‐hatching stage. A biological important consequence of the presence of this Red Cherry shrimp species in the Neotropics is its potential release into nature, which could cause its rapid dispersion affecting populations of other indigenous caridean freshwater shrimps.     

Effects of dietary supplementation of Astragalus membranaceus,Codonopsis pilosula,and Glycyrrhiza uralensis extract mixture on growth performance,haematological parameters and hepatopancreatic performance in juvenile Pacific white shrimp (Litopenaeus vannamei)

Pacific white shrimp is the major farmed shrimp species in the world. It is known to be very sensitive to the environmental and management changes such as intensification, which is one of the primary necessities to increase shrimp production, but represents a stressful condition, and needs to be managed properly to diminish its negative effects in aquaculture. In this study, juvenile Pacific white shrimp were fed diets supplementing with equal quantities of Astragalus membranaceus, Codonopsis pilosula and Glycyrrhiza uralensis extracts in different concentrations (0, 1.0, 2.0 and 3.0 g/kg) for 8 weeks. We subsequently estimated the effects of supplemented diets on growth performance, haematological parameters, and histological changes of hepatopancreas. Results revealed that the supplemented mixture had no benefits on growth and survival rate, but had favourable effects on haemocyte count, number of granulocytes, and hemocyanin concentration in the haemolymph (p > 0.05). We observed that R cells and B cells were increased in hepatopancreatic tubules of shrimps fed on supplemented diets. Besides, a diet containing 2.0 g/kg of extract mixture maintained the decreased levels of alanine aminotransferase (p < 0.05) and aspartate aminotransferase (p > 0.05). Among the used concentrations, 2.0 g/kg seemed to be the most suitable concentration.     

Seasonal patterns in the community of gill monogeneans on wild versus cultured orange‐spotted grouper,Epinephelus coioides Hamilton, 1822 in Daya Bay,South China Sea

Epinephelus is among the most important fish genera in the Southeast Asian Pacific coastal systems. In Chinese coast, the orange‐spotted grouper Epinephelus coioides is one of the most significant species based on culture volume, and it is consumed all over the world. Very little information exists on this species’ parasitofauna. Composition and temporal variation in the community structure of the gill monogeneans on wild versus cultured E. coioides from Daya Bay (23°25′N, 117°2′E), South China Sea were determined using seasonal samples taken between April 2008 and January 2009. Eight species of monogeneans of three families and four genera on the gills of E. coioides were found: Neobenedenia melleni, Haliotrema cromileptis, Diplectanum grouperi, Pseudorhabdosynochus justinei, P. lantauensis, P. coioidesis, P. serrani and P. shenzhenensis. Eight of the monogenean species exhibited seasonal variation in their infection dynamics associated with environmental changes during seasons. The variations in the infection dynamics generated changes in the community structure during the sampling periods. Moreover, in the three different host living environments (wild, monocultured and polycultured), the monogenean communities exhibited the different seasonal patterns.     

Reliance on lakes by salmon,trout and charr (Oncorhynchus,Salmo and Salvelinus): An evaluation of spawning habitats,rearing strategies and trophic polymorphisms

Salmonid fishes may reside within or migrate between stream and lake habitats, or undergo anadromous migrations between freshwater and the ocean. While the degree of anadromy of salmonids has been thoroughly compared, no analogous review has examined the degree of lake use. To assess the extent of reliance on lake habitat in this family, we considered 16 species of salmon, trout and charr from the genera Oncorhynchus, Salmo and Salvelinus, comparing their (a) use of lakes as spawning habitat, (b) rearing strategies in lakes, and (c) occurrence and diversity of lacustrine trophic polymorphism. In identifying the primary life‐history patterns of each species and exploring the lesser‐known lacustrine behaviours, we found that the extent of reliance on lakes exhibits a negative association with the degree of anadromy. Oncorhynchus rely least on lakes, Salmo to an intermediate level and Salvelinus the most, opposite of the general prevalence of anadromy among these genera. Lakes are critical to adfluvial and lake‐resident salmonids, but they also support anadromous and fluvial life histories by providing spawning, rearing, overwintering and/or summer refuge habitat. Adfluviality, although a non‐anadromous life history, consists of similar migration‐related traits and behaviours as anadromy, including the parr–smolt transformation, sex‐biased patterns of migration and residency, and the presence of precocious males. Lakes support life‐history variants, reproductive ecotypes and trophic morphs unique to lacustrine habitat. Therefore, conservation of salmonids is dependent on maintaining the diversity and quality of their habitats, including lakes.     

Assessing connectivity patterns among management units of the Newfoundland and Labrador shrimp population

The Eastern Canadian northern shrimp population, representing one of the most important fisheries in the region, decreased dramatically since the mid‐2000s to a historical low in 2017, but changes were not spatially uniform. Applying a biophysical model within Newfoundland and Labrador (NL) management areas, we investigated connectivity processes during the long pelagic larval phase (2–3 months) of Pandalus borealis and key drivers of larval dispersal in different environmental conditions. We selected 3 years representative of contrasting North Atlantic Oscillation (NAO) phases to assess potential larval dispersal patterns of the northern shrimp population in NL, and hierarchically assessed the impact of the timing of release (yearly and daily), release location, and vertical migration behaviour on shrimp larval dispersal. Overall, we found that populations located on the northern Newfoundland and Labrador shelf supplied potential settlers to southern populations because of the dominant Labrador Current. Ocean circulation and current velocities during the NAO positive year differed from other years, generating contrasting settlement spatial patterns. Larval release location and vertical migration behaviour were the two most important influences on the strength of larval supply and settlement patterns. Inclusion of diel and ontogenic swimming behaviour increased settlement success of larvae released from inshore areas, regardless of study years. Our study improves understanding of northern shrimp stock‐recruitment relationships, their sensitivity to changing environmental conditions, and spatially non‐homogeneous population decline for bentho‐pelagic species with a long larval phase, which could potentially help improve management strategies.     

Lumpfish (Cyclopterus lumpus,Linnaeus) is susceptible to viral nervous necrosis: Result of an experimental infection with different genotypes of Betanodavirus

In recent years, the use of cleaner fish for biological control of sea lice has increased considerably. Along with this, a number of infectious diseases have emerged. The aim of this study was to investigate the susceptibility of lumpfish (Cyclopterus lumpus) to Betanodavirus since it was detected in asymptomatic wild wrasses in Norway and Sweden. Three betanodaviruses were used to challenge lumpfish: one RGNNV genotype and two BFNNV genotypes. Fish were injected and monitored for 4 weeks. Brain samples from clinically affected specimens, from weekly randomly selected fish and survivors were subjected to molecular testing, viral isolation, histopathology and immunohistochemistry. Reduced survival was observed but was attributed to tail‐biting behaviour, since no nervous signs were observed throughout the study. Betanodavirus RNA was detected in all samples, additionally suggesting an active replication of the virus in the brain. Viral isolation confirmed molecular biology results and revealed a high viral titre in BFNNV‐infected groups associated with typical lesions in brains and eyes of survivor fish. We concluded that lumpfish are susceptible to Betanodavirus, as proven by the high viral titre and brain lesions detected, but further studies are necessary to understand if Betanodavirus can cause clinical disease in this species.