Commercial Aquaculture Research Articles

Germ cell-less hybrid fish: ideal recipient for spermatogonial transplantation for the rapid production of donor-derived sperm†.

An interspecific hybrid marine fish that developed a testis-like gonad without any germ cells, i.e., a germ cell-less gonad, was produced by hybridizing a female blue drum Nibea mitsukurii with a male white croaker Pennahia argentata. In this study, we evaluated the suitability of the germ cell-less fish as a recipient by transplanting donor testicular cells directly into the gonads through the urogenital papilla. The donor testicular cells were collected from hemizygous transgenic, green fluorescent protein (gfp) (+/-) blue drum, and transplanted into the germ cell-less gonads of the 6-month-old adult hybrid croakers. Fluorescent and histological observations showed the colonization, proliferation, and differentiation of transplanted spermatogonial cells in the gonads of hybrid croakers. The earliest production of spermatozoa in a hybrid recipient was observed at 7 weeks post-transplantation (pt), and 10% of the transplanted recipients produced donor-derived gfp-positive spermatozoa by 25 weeks pt. Sperm from the hybrid recipients were used to fertilize eggs from wild-type blue drums, and approximately 50% of the resulting offspring were gfp-positive, suggesting that all offspring originated from donor-derived sperm that were produced in the transplanted gfp (+/-) germ cells. To the best of our knowledge, this is the first report of successful spermatogonial transplantation using a germ cell-less adult fish as a recipient. This transplantation system has considerable advantages, such as the use of comparatively simple equipment and procedures, and rapid generation of donor-derived spermatogenesis and offspring, and presents numerous applications in commercial aquaculture.

Growth and survival of silver pompano Trachinotus blochii (Lacepede, 1801) at different salinities in inland saline ground water

Inland saline ground water (ISGW) has attracted great interest for commercial aquaculture of marine species in Haryana and Punjab. The silver pompano (Trachinotus blochii), a candidate for mariculture, was investigated for its potential to survive in inland saline water at ICAR-CIFE, Regional Centre, Rohtak, Haryana during 2015–16. The experimental set up comprised ISGW without potassium amendment, ISGW with potassium amendment and artificial sea water of 5 ppt, 10 ppt and 15 ppt salinity. In ISGW without potassium amendment, 100% mortality was observed at 12 h (5 ppt), 24 h (10 ppt) and 48 h (15 ppt). In the second experiment, three treatments (ISW5, ISW10 and ISW15) of ISGW with potassium amendment equivalent to sea water were prepared. A 100% survival was observed at all salinities in ISGW with potassium amendment, similar to the artificial seawater at the end of 90 days. Significantly higher weight gain, specific growth rate (SGR) and average daily growth (ADG) were observed at ISW10 and ISW15 than at ISW5. The plasma osmolality of silver pompano in ISW10 and ISW15 indicated that silver pompano regulates isosmotic condition to maintain the homeostasis of body. The present results indicate that silver pompano can be reared at 10 ppt to 15 ppt salinity with optimum growth and survival in potassium amended ISGW.

Occurrence, virulence, and antimicrobial resistance of Vibrio parahaemolyticus isolated from bivalve shellfish farms along the southern coast of Korea.

Vibrio parahaemolyticus is the most common pathogen causing seafood-borne illnesses in Korea. The present study evaluated the occurrence, virulence, and antimicrobial resistance of V. parahaemolyticus in seawater and bivalves obtained in 2016 from the southern coast of Korea, an important region for commercial aquaculture industries, especially the Korean raw seafood culture. V. parahaemolyticus was detected in 87 of 160 (54.4%) bivalve samples and in 32 of 130 (24.5%) seawater samples. Especially high levels were detected during summer to early autumn. All the seawater and bivalves contained less than 2 and 5% of the tdh and trh genes of the isolates, respectively, and seawater isolates possessed two fewer genes than the bivalve isolates. Of 23 antimicrobials tested, three agents (ofloxacin, norfloxacin, and trimethoprim/sulfamethoxazole) effectively treated V. parahaemolyticus illness due to the sensitivity of the isolates. The isolates were highly resistant to ampicillin, however, excluding it as a treatment option. More than half of the isolates exhibited resistance to at least three antimicrobials. These findings indicate the importance of an integrated monitoring and surveillance program noting the occurrence, virulence, and antimicrobial resistance patterns of V. parahaemolyticus in various aquatic sources for preventing human health risks from seafood consumption.

Antioxidant and antitumor potential of wild and IMTA-cultivated Osmundea pinnatifida

Osmundea pinnatifida is a red edible seaweed known as pepper dulse. O. pinnatifida was cultivated in the farm of ALGAplus (Ilhavo, Portugal). This farm is integrated with a seabream and seabass commercial aquaculture and uses the nutrient-enriched water resultant from the fish production as its cultivation medium in the integrated multi-trophic aquaculture (IMTA) manner. Wild and IMTA-cultivated samples of O. pinnatifida were screened for antioxidant and antitumor activities. The antioxidant capacity of solvent extracts from wild and IMTA cultivated samples was assessed in two methods (2,2-diphenyl-1-picrylhydrazyl (DPPH) and oxygen radical absorbance capacity (ORAC)), and their total phenolic contents (TPC) were estimated. Antitumor activity was evaluated in three different tumor cell lines (HepG-2, MCF-7, and SH-SY5Y) through 3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide (MTT) assay. Among the solvents used for extraction, dichloromethane was the most effective to extract phenolic compounds and presented higher ORAC. A significant correlation was found between TPC and ORAC, which was also sustained by the principal components analysis (PCA). Dichloromethane extracts induced a cytostatic effect on MCF-7 cells and showed weak cytotoxicity to SH-SY5Y cells and weak impact on cell proliferation. Overall, there were no statistically significant differences in the biological activities shown by the wild and IMTA-cultivated samples. Hence, O. pinnatifida can be obtained in an economical and environmentally sustainable way through IMTA, maintaining bioactive properties in a high potential for further nutraceutical purposes.

Water temperature and salinity synergistically affect embryonic and larval development of the tropical black-lip rock oyster Saccostrea echinata

Poor larval survival is a bottleneck to commercial hatchery production of the tropical black-lip rock oyster, Saccostrea echinata. This study investigated the synergistic effects of water temperature and salinity on embryonic and larval development across each major larval life stage. Results showed that water temperature and salinity have a significant effect on embryonic development of S. echinata and that embryos did not develop below 17 °C and 14 psu. Survival was high (55–100%) across all treatments and larval stages, and shell size was used primarily to determine larval response to treatments. Larval shell size increased as water temperature and salinity increased, reaching optima at 32 °C and 23 psu for D-veligers (mean DVM 78.18± 0.85 μm), at 32 °C and 26 psu for umbonate larvae (mean DVM 183.40± 2.60 μm), and at 32 °C and 29 psu for eyed larvae (mean DVM 249.64± 3.22 μm). It is recommended that S. echinata embryos and larvae are cultured within 28–32 °C and at salinity optima for each larval stage: embryo development at 32 psu, D-veligers and umbonate larvae between 23 and 26 psu, and eyed larvae between 28 and 30 psu. This is the first investigation of the combined effects of water temperature and salinity on S. echinata and provides valuable information to accelerate commercial aquaculture of this tropical species.

Environmental Health Assessment Using Sentinel Species near Placencia Lagoon, Belize

Unexplained bird deaths discovered around Placencia Lagoon, Belize over a 2-year period sparked an investigation into the environmental health of the lagoon and two of its major tributaries. In this study, conducted from January 23 to February 28, 2018, we assessed avian health within two commercial aquaculture facilities, each with a substantial outflow into the lagoon; a shrimp farm and a tilapia farm. Birds were chosen as our study subjects not only because of previous bird deaths, but also as sentinel species to assess overall possible contamination. Both facilities had previously been affected by die-offs of their cultivated product. The variety of sampled bird species, both year-round and winter residents, fed on small fish, airborne insects, mud-dwelling invertebrates and/or plant material, i.e. seeds and fruits, thereby sampling air, soil and water as possible bioaccumulation vectors. We trapped birds in, or nearby outflow containment ponds which emptied into the lagoon. Additionally, we assessed avian health at two reference locations on Placencia Penninsula, not known for avian health problems. Birds from multiple families representing different ecological niches were captured using two net types. We conducted standard ornithological assessments, measured hematocrit, made an evaluation of ectoparasite load and types, and for shorebirds, examined fecal swabs for parasites. Measured values were compared to published data and a previously established database from data collected elsewhere in the Caribbean. For each of the major sites, an extensive period of evaluation was later followed with a shorter, second evaluation at each location. Except for a single, second-year, Brown Pelican (Pelicanus occidentalis) evaluated one day at the close of the study, 257 birds were found to be healthy on all parameters including hematocrit and parasite load. We observed that the pelican had not been present previously and inferred that its health problems were acquired at another site. This conclusion was corroborated by the concurrent discovery of dead or dying pelicans along the Belize coast near the end of this investigation.

Improvements in larviculture of Crangon crangon as a step towards its commercial aquaculture

The European brown shrimp, Crangon crangon, is a highly valued commercial species in Europe. These shrimp fisheries are characterized by strong seasonal variations in average landings. Attempts to ‘catch and hold’ wild adults in land-based rearing systems have been proven to be very difficult, due to inadequate feed, slow growth and high mortality. In this study, we have optimized design and operation procedures of a small-scale static larval rearing system for the culture of C. crangon larvae. Focus was on optimizing larval survival via water temperature, feed selection, feeding regime and density. This is the first report that shows that C. crangon larvae can be reared at high densities of 300 larvae L-1 with high survival of 73.5 (± 5.4)% under laboratory conditions. In these systems, larvae can be fed exclusively Artemia nauplii according to a feeding regime which is adjusted based on major moulting events. Addition of microalgae may further increase survival by 10%. The information gathered during this research can be applied to further optimize larval development in either flow-through or recirculation systems.

Monsoonally Driven Reproduction in the Tropical Black-Lip Rock Oyster Saccostrea echinata (Quoy & Gaimard, 1835) in Northern Australia

The reproductive cycle of the tropical black-lip rock oyster Saccostrea echinata was determined at three locations in the Northern Territory, Australia. Wild oysters were collected every 4–6 wk (n = 13–23) from January 2016 until June 2017. Biometric and condition index data were collected, and tissues were histologically examined to determine gonad index (GI) and gender ratios. Seawater and air temperature were monitored by intertidally deployed data loggers, and daily rainfall data were obtained from local weather stations. A total of 527 oysters were sampled across all sites, of which 34.2% were females, 47.4% were males, 0.4% were hermaphrodites, and 18.0% were of indeterminate gender. The GI presented a clear annual cycle; values fluctuated but remained high (1.94–3.94) from October through April and were low (>1.50) from May through September, across both years. Across all sites, the GI had a strong, positive correlation with temperature (r = 0.783; df = 26; P <0.001) and a moderate, positive correlation with rainfall (r = 0.496; df = 31; P <0.05). Synchronization in spawning patterns occurred between sites, and gender ratios suggest that S. echinata is a dioecious species with low levels of functional hermaphroditism. The major finding of this study is that S. echinata spawns semicontinuously throughout the monsoon season (October–April) and has an extended resting phase throughout the dry season (May–September). The information generated in this study has a number of potential applications relating to the timing of broodstock collection and hatchery production, and it provides a broader basis for further developing S. echinata as a commercial aquaculture species.

Computational characterization of epitopic region within the outer membrane protein candidate in Flavobacterium columnare for vaccine development

Gram-negative bacteria is the main causative agents for columnaris disease outbreak to finfishes. The outer membrane proteins (OMPs) candidate of Flavobacterium columnare bacterial cell served a critical component for cellular invasion targeted to the eukaryotic cell and survival inside the macrophages. Therefore, OMPs considered as the supreme element for the development of promising vaccine against F. columnare. Implies advanced in silico approaches, the predicted 3-D model of targeted OMPs were characterized by the Swiss model server and validated through Procheck programs and Protein Structure Analysis (ProSA) web server. The protein sequences having B-cell binding sites were preferred from sequence alignment; afterwards the B cell epitopes prediction was prepared using the BCPred and amino acid pairs (AAP) prediction algorithms modules of BCPreds. Consequently, the selected antigenic amino acids sequences (B-cell epitopic regions) were analyzed for T-cell epitopes determination (MHC I and MHC II alleles binding sequence) performing the ProPred 1 and ProPred server respectively. The epitopes (9 mer: IKKYEPAPV, YGPNYKWKF and YRGLNVGTS) within the OMPs binds to both of the MHC classes (MHC I and MHC II) and covered highest number of MHC alleles are characterized. OMPs of F. columnare being conserved across serotypes and highly immunogenic for their exposed epitopes on the cell surface as a potent candidate focus to vaccine development for combating the disease problems in commercial aquaculture. The portrayed epitopes might be beneficial for practical designing of abundant peptide-based vaccine development against the columnaris through boosting up the advantageous immune responses.Communicated by Ramaswamy H. Sarma

Piscine orthoreovirus sequences in escaped farmed Atlantic salmon in Washington and British Columbia

BackgroundPiscine orthoreovirus (PRV) is an emergent virus in salmon aquaculture belonging to the family Reoviridae. PRV is associated with a growing list of pathological conditions including heart and skeletal inflammation (HSMI) of farmed Atlantic salmon. Despite widespread PRV infection in commercially farmed Atlantic salmon, information on PRV prevalence and on the genetic sequence variation of PRV in Atlantic salmon on the north Pacific Coast is limited.MethodsFeral Atlantic salmon caught in Washington State and British Columbia following a large containment failure at a farm in northern Puget Sound were sampled. Fish tissues were tested for PRV by RT-qPCR assay for segment L1 and conventional RT-PCR for PRV segment S1. The PCR products were sequenced and their relationship to PRV strains in GenBank was determined using phylogenetic analysis and nucleotide and amino acid homology comparisons.ResultsFollowing the escape of 253,000 Atlantic salmon from a salmon farm in Washington State, USA, 72/73 tissue samples from 27 Atlantic salmon captured shortly after the escape tested PRV-positive. We estimate PRV-prevalence in the source farm population at 95% or greater. The PRV found in the fish was identified as PRV sub-genotype Ia and very similar to PRV from farmed Atlantic salmon in Iceland. This correlates with the source of the fish in the farm. Eggs of infected fish were positive for PRV indicating the possibility of vertical transfer and spread with fish egg transports.ConclusionsPRV prevalence was close to 100% in farmed Atlantic salmon that were caught in Washington State and British Columbia following a large containment failure at a farm in northern Puget Sound. The PRV strains present in the escaped Atlantic salmon were very similar to the PRV strain reported in farmed Atlantic salmon from the source hatchery in Iceland that was used to stock commercial aquaculture sites in Washington State. This study emphasizes the need to screen Atlantic salmon broodstock for PRV, particularly where used to supply eggs to the global Atlantic salmon farming industry thereby improving our understanding of PRV epidemiology.

Optimal spawning conditions of Phyllospora comosa (Phaeophyceae, Fucales) for mariculture

The fucoid Phyllospora comosa has sparked interest from the industry as a potential commercial aquaculture species. However, information on the feasibility of culturing this species, including maximising spawning and fertilisation, remains limited. This study aimed to identify optimal conditions for spawning and early development of P. comosa under laboratory conditions. We tested spawning and germination success across lunar phase (new moon vs full moon), temperature (15 °C, 18 °C, 21 °C), light (35 μmol photons m−2 s−1 vs 0 μmol photons m−2 s−1) and exposure (desiccated vs submerged). Lunar cycles were compared over three consecutive months. Fifty fertile P. comosa male and female thalli were collected from Port Fairy, Victoria, Australia, every 2 weeks to coincide with full and new moon phases from February to April 2017. Spawning of eggs and sperm was achieved in all treatment combinations. However, there was no consistent effect of lunar phase, light, temperature or exposure, with high temporal variability amongst treatment groups. Percentage germination after 24 h in static culture varied between 35 and 90%, and overall embryo mortality was high (> 65%) after 7 days, but did not differ amongst spawning cue treatments. The high mortality observed at day 7 did not appear to be linked to insufficient egg or sperm densities nor excess sperm (polyspermy). Overall results indicate flexibility in spawning conditions which is advantageous for integration into aquaculture.

Increased pCO2 changes the lipid production in important aquacultural feedstock algae Isochrysis galbana, but not in Tetraselmis suecica

Increased anthropogenic CO2 emissions are leading to an increase in CO2 uptake by the world's oceans and seas, resulting in ocean acidification with a decrease in global ocean water pH by as much as 0.3–0.4 units by the year 2100. The direct effects of changing pCO2 on important microalgal feedstocks are not as well understood. Few studies have focused on lipid composition changes in specific algal species in response to ocean acidification and yet microalgae are an indispensable food source for various marine species, including juvenile shellfish. Isochrysis galbana and Tetraselmis suecica are widely used in aquaculture as feeds for mussels and other shellfish. The total lipid contents and concentrations of I. galbana and T. suecica were investigated when grown under present day (400 ppm) and ocean acidification conditions (1000 ppm) to elucidate the impact of increasing pCO2 on an important algae feedstock. Total lipids, long-chain alkenones (LCAs) and alkenoates decreased at 1000 ppm in I. galbana. I. galbana produces higher lipids than T. suecica, and is perhaps as a result more impacted by the change in carbon available for lipid production under higher pCO2.I. galbana is an important feedstock, more easily assimilated for growth in juvenile shellfish and reductions in lipid composition may prove problematic for the growth of future shellfish aquaculture. Our findings suggest that higher pCO2 impacts on algal lipid growth are species specific and warrant further study. It is therefore vital to examine the impact of high CO2 on algal lipid production, especially those commercial shellfish feed varieties to predict future impacts on commercial aquaculture.

A comparison of methods for determining ploidy in white sturgeon (Acipenser transmontanus)

Release of sturgeon with abnormal ploidy into the wild may result in reduced fitness due to lowered fertility in the F2 and subsequent generations. Further, there is evidence that ploidy affects reproductive development and caviar yield. Therefore, the ability to accurately characterize the ploidy of white sturgeon (Acipenser transmontanus) is essential for both commercial and conservation aquaculture. This study compares nuclear volume and whole erythrocyte long-axis lengths obtained using Coulter counter and blood smears, respectively, from captive white sturgeon from populations originating in California and Idaho. We examine which method provides the most accurate, time efficient and cost-effective characterization of ploidy in this species. Results from Coulter counter and blood smears were compared to results from flow cytometry, the gold standard for genome size analysis. Previous work suggests that blood smears can distinguish between 8N (diploid) and 12N (triploid) sturgeon, but further analysis is required to see if this method can also be used to identify 10N fish and to provide robust evidence of its utility in 8N and 12N fish across populations. In this study, we demonstrated that the Coulter counter had 100% agreement with flow cytometry in ploidy assignment, while blood smears vary in their accuracy based on population. Blood smears showed a high degree of overlap in erythrocyte long-axis length between 8N and 10N individuals as well as some overlap between 10N and 12N individuals in the California fish, and a high degree of overlap between 8N and 12N individuals in the Idaho fish. Although blood smears are time-intensive and vary in their ploidy assignment accuracy, they are a low-cost technique and as such may have some utility for caviar farms attempting to identify 12N individuals in a small number of broodstock. By comparing the accuracy, efficiency and cost of these three methods, sturgeon farmers and conservation hatcheries will be able to choose the best method for their needs in determining the ploidy of their fish. We determined that Coulter counter is equally accurate to flow cytometry and is also the most time efficient method for ploidy determination in white sturgeon.

Theoretical and practical analysis of waste heat recovery system in off-season rainbow trout production

The supply of heat for fish farms, especially during off-season production, is necessary for the establishment of commercial aquaculture. For this purpose, research was carried out on the supply of heating ener to a rainbow trout farm (cold water fish) using a waste heat recovery system in the city of Meshgin in Ardabil province. The study area has 20 indoor pools and 14 unguarded pools. The 14 pools that are in the indoor area, are used for this study. Seven pools of these 14 pools were at high altitude and other 7 pools were at low altitude. After collection of the temperature data for waste water ponds that had provided optimum temperature conditions in the off-season using geothermal fluid, three modes for waste heat recovery were designed according to the thermal, flow and physicochemical properties of the waste pond. In the first mode, the output of the first seven pools and the second seven pools were combined and the fluid flow rate reached to 24.92 L/sec. In the second mode, the output of the second seven pools (8.15 L/sec) was used to recover heat, and in the third case, the output of the first seven pools (at high-altitude pools and with the flow rate of 16.77 L/sec) was used to recover heat. After obtaining technical approval and determining the economic value of each component of the waste heat recovery circuit from specialized companies in Iran, the proposed systems were analyzed theoretically with COMSOL software. Because there was no equal rate of flow, velocity or geometry for comparison between the optimum state in the theoretical conditions of practice, the temperature differences between the input hot water and output cold water were used for all three modes of heat recovery. Technically, the results indicate that the second mode is best in both the theoretical and practical modes of the waste heat recovery circuit. The first mode recovery system had the smallest temperature difference between the hot water inlet and cold water outlet. Economically, the minimum cost of establishing a heat recovery system was for the second mode, with a decrease of 60.65% and 38.83% compared to the third and first modes, respectively. Considering technical and economic factors, the waste heat recovery system of the second mode was the most appropriate choice for the trout farm, both theoretically and practically. The first and third modes ranked next, respectively.

Hitch-hikers of the sea: concurrent morphological and molecular identification of Symplegma brakenhielmi (Tunicata: Ascidiacea) in the western Mediterranean Sea

We report here one of the first records of the non-indigenous colonial ascidian Symplegma brakenhielmi (Michaelsen, 1904) in the western Mediterranean Sea. Colonies of this invasive species have been collected in 2014 and 2018 along North-eastern Sardinia coasts (Olbia, Italy). Further colonies have been observed in 2016 in the Mar Piccolo basin (Gulf of Taranto, Italy). Both areas are strongly influenced by anthropogenic activities such as commercial shipping and aquaculture, suggesting these human-mediated pathways the most likely vectors of introduction. In both areas, the colonies present two different color phenotypes, the yellow and the red type, with the yellow coloration never found before in the Mediterranean Sea. Morphological and DNA barcode analyses of the collected specimens show that both these color types belong to the same species. Phylogenetic and species delimitation analyses based on the DNA barcode confirm our identification as S. brakenhielmi, but also indicate a surprisingly high similarity with published sequences of other two species, including the co-generic species Symplegma rubra Monniot, 1972. Morphological and molecular examination of a large number of samples of these species would be need in the near future to clarify this issue.

The Protein-Protein Interaction Network of Litopenaeus vannamei Haemocytes.

Protein–protein interaction networks (PINs) have been constructed in various organisms and utilized to conduct evolutionary analyses and functional predictions. Litopenaeus vannamei is a high-valued commercial aquaculture species with an uncharacterized interactome. With the development of RNA-seq techniques and systems biology, it is possible to obtain genome-wide transcriptional information for L. vannamei and construct a systematic network based on these data. In this work, based on the RNA-seq of haemocytes we constructed the first L. vannamei PIN including 4,858 proteins and 104,187 interactions. The PIN constructed here is the first large-scale PIN for shrimp. The confidence scores of interactions in the PIN were evaluated on the basis of sequence homology and genetic relationships. The immune-specific sub-network was extracted from global PIN, and more than a third of proteins were found in signaling pathways in the sub-network, which indicates an inseparable relationship between signaling processes and immune mechanisms. Six selected signaling pathways were constructed at different age groups based on evolutionary analyses. Furthermore, we showed that the functions of the pathways’ proteins were associated with their evolutionary history based on the evolutionary analyses combining with protein functional analyses. In addition, the functions of 1,955 unclassified proteins which were associated with 3,191 unigenes were assigned using the PIN, which account for approximately 70.3 and 44.9% of the previously unclassified proteins and unigenes in the network, respectively. The annotation of unclassified proteins and unigenes based on the PIN provides new candidates for further functional studies. The immune-specific sub-network and the pathways extracted from the PIN provide a novel information source for studying of immune mechanisms and disease resistances in shrimp.

Transcriptome Analysis of Male and Female Mature Gonads of Silver Sillago (Sillago sihama).

Silver sillago (Sillago sihama) is an emerging commercial marine aquaculture species in China. To date, fundamental information on S. sihama, such as genomic information, is lacking, and no data are available on the gonad transcriptome of S. sihama. Here, the first gonadal transcriptomes of S. sihama have been constructed and genes potentially involved in gonadal development and reproduction identified. Illumina sequencing generated 60.18 million clean reads for the testis and 59.10 million for the ovary. All reads were assembled into 74,038 unigenes with a mean length of 1,004 bp and N50 value of 2,190 bp. Among all the predictable unigenes, a total of 34,104 unigenes (46%) were searched against multiple databases, including 33,244 unigenes annotated in the RefSeq Non- Redundant database at NCBI, and 28,924 in Swiss-Prot. By comparing the ovary and testis, 35,367 unigenes were identified as being differentially expressed between males and females, of which 29,127 were upregulated in the testis and 6,240 were upregulated in the ovary. Numerous differentially expressed genes (DEGs) known to be involved in gonadal development and gametogenesis were identified, including amh, dmrt1, gsdf, cyp19a1a, gnrhr, and zps. Using gene ontology (GO) and Kyoto Encyclopedia of Genes and Genomes (KEGG) enrichment analyses, the top 20 KEGG pathways with highest number of DEGs were found to be involved in regulating gonadal development and gametogenesis in S. sihama. Moreover, 22,666 simple sequence repeats (SSRs) were identified in 14,577 SSR-containing sequences. The findings provide a valuable dataset for future functional analyses of sex-associated genes and molecular marker assisted selection in S. sihama.

First detection of Erysipelothrix sp. infection in western mosquitofish Gambusia affinis inhabiting catfish aquaculture ponds in Mississippi, USA.

Native and introduced fish can serve as reservoirs for pathogens of cultured fish species. In the current study, 351 archived western mosquitofish Gambusia affinis collected from experimental catfish production ponds in Mississippi, USA, were surveyed histologically to evaluate their potential as vectors for fish pathogens. In addition to epitheliocystis and multiple metazoan parasites, 8 fish had widespread basophilic colonies of small Gram-positive rods associated primarily with stroma supporting the skeletal muscle and bone, as well as connective tissue components of other tissues and organ systems, such as perivascular adventitia and basement membranes. These findings were consistent with spaC-type Erysipelothrix sp. infections in ornamental fish cultured in the USA. The 16S rRNA, gyrase B (gyrB), and surface protective antigen (spa) genes were amplified and sequenced from bacterial colonies excised from paraffin-embedded tissue sections using laser capture microdissection. Molecular data confirmed the identity of a spaC-type Erysipelothrix sp., which grouped phylogenetically with spaC-type Erysipelothrix sp. from diseased ornamental fish. Given the significance of commercial catfish aquaculture in the southeastern USA and the widespread distribution of mosquitofish in catfish ponds throughout the region, infectivity trials with channel catfish Ictalurus punctatus were conducted. Catfish fingerlings were exposed to a spaC-type Erysipelothrix sp. isolate by intracoelomic injection and gavage. No mortality was observed in catfish exposed by either route, and surviving fish demonstrated no significant histopathologic lesions, suggesting channel catfish have low susceptibility to the bacteria. Further research is warranted to investigate the susceptibility of other cultured fish species to this emergent fish pathogen.

Fish response to hypoxia stress: growth, physiological, and immunological biomarkers.

Water quality encompasses the water physical, biological, and chemical parameters. It generally affects the fish growth and welfare. Thus, the success of a commercial aquaculture project depends on supplying the optimum water quality for prompt fish growth at the minimum cost of resources. Although the aquaculture environment is a complicated system, depending on various water quality variables, only less of them have a critical role. One of these vital parameters is dissolved oxygen (DO) level, which requires continuous oversight in aquaculture systems. In addition, the processes of natural stream refinement require suitable DO levels in order to extend for aerobic life forms. The depletion of DO concentration (called hypoxia) in pond water causes great stress on fish where DO levels that remain below 1-2mg/L for a few hours can adversely affect fish growth resulting in fish death. Furthermore, hypoxia has substantial effects on fish physiological and immune responses, making them more susceptible to diseases. Therefore, to avoid disease outbreak in modern aquaculture production systems where fish are intensified and more crowded, increasing attention should be taken into account on DO levels.

Ethical considerations and unanticipated consequences associated with ecological forecasting for marine resources

Forecasts of marine environmental and ecosystem conditions are now possible at a range of time scales, from nowcasts to forecasts over seasonal and longer time frames. Delivery of these products offers resource managers and users relevant insight into ecosystem patterns and future conditions to support decisions these stakeholders face associated with a range of objectives. The pace of progress in forecast development is so rapid that the scientific community may not be considering fully the impacts on stakeholders and their incentives. Delivery of information, particularly about future conditions and the uncertainties associated with it, involves a range of judgements, or “ethical” considerations, including treatment of forecast failure, inequity in stakeholder response options, and winners and losers in commercial markets. Here, we explore these often unanticipated considerations via a set of case studies spanning commercial fishing, recreational fishing, aquaculture, and conservation applications. We suggest that consideration of ethical issues by scientists and their research partners is needed to maintain scientific integrity and fairness to end users. Based on these case studies and our experience, we suggest a set of ten principles that might be considered by developers and users of ecological forecasts to avoid these ethical pitfalls. Overall, an interdisciplinary approach, and co-production with end users will provide insurance against many unanticipated consequences.