Nursery System Research Articles

Influence of glacial flour on the primary and secondary production of sockeye salmon nursery lakes: a comparative modern and paleolimnological study

The increasing rate of glacier retreat and turbid glacial runoff can have a strong influence on freshwater ecosystems. Seton and Anderson lakes (British Columbia, Canada) are sockeye salmon (Oncorhynchus nerka) nursery systems. Since the 1940s, the Bridge River Diversion (BRD) introduced glacially turbid water into Seton Lake. To assess the impact of the BRD on the production of Seton Lake, we combined data from limnological surveys with the analysis of subfossil cladocerans and diatoms from sediment cores, using Anderson Lake as a reference. The modern data indicate that the euphotic zone is 14 m shallower and the cladoceran density and biomass are significantly lower in Seton Lake in comparison with Anderson Lake. The paleo-data indicate that following the BRD, the sedimentary fluxes of cladoceran and diatom declined 2- to 10-fold in Seton Lake and remained low thereafter. Together, our data support declines in primary and secondary producers following the BRD, likely due to changes in light penetration and (or) other indirect influence, and provides insights into the impact of turbid meltwater on the biological production of downstream lakes.

Assessment of economic loss due to fish diseases in Assam, India and implications of farming practices

Extensive surveys were conducted in 60 fish farms in Cachar and Nagaon districts of Assam, India to assess economic loss due to aquatic animal diseases and the contribution of fish farming practices therein. Epizootic Ulcerative Syndrome (EUS), also known as mycotic granulomatosis or red spot disease, was the most common disease that affected most fish species during winter months. Other disease conditions reported were dropsy, fin/tail rot and Argulus infestation. Overall disease prevalence was less in Cachar district compared to that in Nagaon district. Estimated loss of fish production (as percentage of total production) and total economic loss (in INR) were estimated to be 10.8% & 67,500.0 per farm (30,770.0 per ha) in Cachar and 5% & 55,300.0 per farm (14,900.0 per ha) in Nagaon district.The average farm area, water area and the number of ponds (per farmer) were less in Cachar compared to that in Nagaon district. Average fish production was also lower (1870 kg ha-1) in Cachar compared to Nagaon (2470 kg ha-1). The majority of fish farms in Cachar (60%) operated as a nursery (N) and grow-out (G) systems whereas those in Nagaon operated as nurseryfingerling-growout (N-F-G) system (63.33%). An overwhelming majority of farmers (93.33%) in Cachar practiced polyculture, but 30% of farmers practiced integrated farming in Nagaon district. N-F-G farming system and integrated culture practice adopted by the majority of Nagaon farmers led to higher fish productivity and lesser economic loss. Poor pre-stocking management of fish ponds was found to be the main contributory factor for higher disease prevalence in Nagaon compared to that in Cachar district. However, the farmers in Nagaon district were more aware of disease control measures that resulted in moderate economic loss. Key words Aquaculture practices, Fish diseases, Economic loss, Assam

Afforestation and agroforestry enhance soil nutrient status and carbon sequestration capacity in eastern China

AbstractAfforestation and agroforestry both sequester atmospheric carbon (C) and store C in the soil. However, the response of soil nutrients and soil organic carbon (SOC) to these practices has not been fully examined, especially in deep soil layers. We therefore investigated the effects of afforestation and agroforestry on the nutrient contents and organic carbon (OC) stocks within a 100‐cm depth in eastern China. The soil nutrient contents and stoichiometry as well as the SOC contents and stocks exhibited different vertical patterns and varied among the five planting systems. The total nitrogen (TN), total phosphorus (TP), and SOC contents decreased dramatically at a 20‐cm depth, and the total potassium (TK) content exhibited a different pattern. Compared with adjacent croplands and nurseries, the forest plantation and agroforestry systems had higher SOC stocks, ranging from 42.9 to 111.6 t·hm−2 in the whole soil profile. The SOC distribution among the depth gradient varied among planting systems, and the topsoil SOC stocks played crucial roles in total SOC storage within a depth of 100 cm in the cropland and nursery systems. The soil pH and bulk density (BD) were negatively correlated with the SOC content, and a significant positive linear relationship occurred between the TN and SOC contents and between the TP and SOC contents. We recommend that combinations of nitrogen (N) and phosphorus (P) fertilizers would benefit SOC storage and improve stabilization in agroforestry and plantation systems.

Improving scallop (Pecten maximus and Placopecten magellanicus) spat production by initial larvae size and hydrodynamic cues used in nursery system

There are several factors affecting scallops during the metamorphosis process that could explain the relatively low post-larvae yield observed in hatcheries. Competent bivalve larvae respond to different settlement cues to undergo metamorphosis and without adequate cues, larvae delay their metamorphosis. The objective of this study is to improve the settlement ratio of the two scallop species, Placopecten magellanicus and Pecten maximus by physical cues associated with hydrodynamic conditions, stocking density in settlement units and larval size at time of transfer to settling units. For each treatment, physiological condition was determined by fatty acid analysis to determine the energetic reserves and structural lipids. We observed similar results for the two important commercial pectinid species and validate the hypothesis on the positive effect of increased flow rate and larval size after transfer to settlement systems on settlement success. Increasing flow rate also affects positively the physiological condition of settled post-larvae by a higher accumulation of total fatty acids in neutral lipid fractions. Furthermore, no effect of larval stocking density until 90 larvae cm−2 in the downwelling sieves was observed. To our knowledge this study is the first to characterize the effect of seawater flow rate on settlement success of different pectinid species cultured under similar conditions. The experiments were performed in a close to commercial scale and thus are relevant to industry situations.

Fasilitas, Aksesibilitas Dan Daya Tarik Wisata Terhadap Kepuasan Wisatawan

Bangka Belitung is an archipelago province that has various tourist destinations, one of which is Bangka Botanical Garden (BBG) which is an agro tourism area that not only promotes nursery systems, but also other fields such as education, research, sports and tourism. This study aims to determine the effect of facility, accessibility and tourist attractiveness on tourist satisfaction visiting the Bangka Botanical Garden (BBG) Pangkalpinang. This Study uses a quantitative approach with a total sample of 260 respondents, while sampling techniques is non-probability sampling techniques using accidental sampling method. The independent variable in this study consists of facitily, accessibility, and tourist attractiveness, while the dependent variable is tourist satisfaction. Data processing uses multiple linear regression analysis with T test, F and R 2 test. The results showed that testing the hypotheses, both partially and simultaneously on facility variables, accessibilities and tourist attractiveness had a positive and significant effect on tourist satisfaction visiting Bangka Botanical Garden (BBG) Pangkalpinang. This indicated that the better the facilities, accessibilities and tourist attractiveness available in the Bangka Botanical Garden (BBG) tourism area of Pangkalpinang, the more tourist satisfaction increase. The coefficient of determination (R 2 ) was 62.7%, which means that the variables of tourist satisfaction can be explained by variable facilities, accessibility and tourist attractiveness .

EXPERIENCE IN PRESERVING THE GENETIC DIVERSITY OF STONE FRUITS USING THE BORDER HEDGING TECHNOLOGY

Conservation of the world’s plant genetic resources is one of the most significant and relevant problems of mankind. At Krymsk Experimental Breeding Station of VIR, where the largest stone fruit plant genetic diversity in Russia is assembled (more than 5 thousand genotypes: cultivars and species, wild forms, distant hybrids and polyploids), a collection maintenance technology of ‘border hedging’ has been developed and successfully used. This method makes it quite economical (in terms of space reduction, simplification of the system of care for the storage garden, and decreasing the use of chemical protection agents) to maintain a large number of live accessions ex situ. The border hedging technology is based on a propagule nursery system that enables plants to grow longer than in conventional gardens, constantly keeping them in a state of active growth. The basic elements of this technology are dense arrangement of plants (intervals for high-growing plants: 4.0–5.0 m between rows, and 1.0–1.5 m in a row; for low-growing ones: 2.5 m between rows, and 0.5–1.0 m in a row) and annual pruning of shoots at a height of 1.0–1.2 m. Years of experience in using a denser planting pattern for collection garden maintenance helped to identify a number of most significant factors in this system, which make up the scientific basis of the technology for optimally efficient preservation of genotypes and their genetic compliance (representativeness). Among them are biological features of the in situ plant growth habit, including vigor, selection of rootstock or decision on own-root cultivation, layout of the plot, and maintenance system. If it is necessary to study the accessions in the garden where they are preserved in order to make their initial evaluation (approbation, morphological description, study of crop structure, biochemical or biotechnological assessment, analysis of resistance to biotic and abiotic stressors), the plants should not be pruned for 1–2 years. Upon completion of these works, the trees are coppiced again.

Feasibility of omega bench grafting in guava tree (Psidium guajava L.) propagated via herbaceous stem cutting

ABSTRACTRoot-knot nematode Meloidogyne mayaguensis Rammah & Hirschmann is a limiting factor in guava tree (Psidium guajava L.) production around the world. An alternative to address this problem is the use of resistant root-knot nematode rootstocks. However, the guava nursery system which is based on herbaceous stem cutting propagation needs to be modified as a rootstock produced via cutting must be grafted with nematode susceptible commercial cultivars. Thus, the objective of this study was to verify the feasibility of omega bench grafting in guava tree propagated by herbaceous stem cutting. Root-knot nematode tolerant ‘Tailandesa’ herbaceous stem cuttings was used as rootstock and ‘Paluma’ and ‘Pedro Sato’ as commercial cultivar grafts. It was observed 100% rooting, cutting survival, and leaf retention on rootstocks grafted with ‘Paluma’ and ‘Pedro Sato’. However, grafting take was not successful as the tissues presented fast oxidation, dehydration and graft death in both commercial cultivars. However, the immersion of the grafts into a solution containing 2.0% citric acid and 1.0% ascorbic acid controlled the oxidation process and resulted in 28.6% and 37.5% successful grafting in the combinations ‘Paluma’/‘Tailandesa’ and ‘Pedro Sato’/’Tailandesa’, respectively.

Effects of shading on periphyton characteristics and performance of sandfish, Holothuria scabra Jaeger 1833, juveniles

Mass production of sea cucumber (sandfish; Holothuria scabra) juveniles is carried out in periphyton-based ocean nursery systems. However, detailed studies on the importance of periphyton as a food source for post-settled juveniles, and on factors influencing biofilm development and composition are scarce. Such information is critical in the optimization of both culture systems and husbandry procedures, and to improve production of juveniles. In this study, the effects of relative food abundance and shading on the feeding activity of the juveniles (~5 mm) under laboratory conditions were determined. The effects of shading (ambient vs. shaded) on periphyton development, and on the growth performance of post-settled juveniles, were also determined in a 30-day field experiment. Food consumption in the ‘high’ food and ambient light treatment was significantly higher (2.4 ± 0.1 mg day−1) than that of juveniles reared in other treatments, including ‘low’ food and shaded culture vessels. Juveniles reared in low food conditions covered significantly greater areas when feeding (2.3 ± 0.28 cm2 day−1) than juveniles reared in high food conditions (0.41 ± 0.20 cm2 day−1). Average length and absolute growth rate (AGR) of juveniles in the shaded treatment were significantly higher by day 15, but differences between light treatments were not significant by day 30. Interestingly, juvenile survival was significantly higher in the shaded (56.9 ± 20.7%) treatment compared to the ambient light (34.4 ± 22.9%) treatment. The chlorophyll a content of periphyton was significantly higher by day 30 than at day 5 in both treatments. Total periphyton biomass (AFDW) was higher in the ambient light treatment than in the shaded treatment, but both generally decreased overtime. Results suggest that food quality is better during the early colonization of periphyton as indicated by the higher absolute growth rates of juveniles during the first 15 days of the experiment. This study generated new information on factors influencing the success of hapa net-based nursery culture of sandfish juveniles and provides a basis for improved use and management of such systems.

Periphyton characteristics influence the growth and survival of Holothuria scabra early juveniles in an ocean nursery system

Floating hapas (fine mesh net enclosures) are a cost-effective ocean nursery system to culture post-metamorphic Holothuria scabra to release size. The growth of periphyton biofilm on hapas is a natural food source for early juveniles. This study investigated the effects of periphyton quality (i.e. chlorophyll-a, phaeopigment, total biomass, autotrophic index or AI), water quality (nutrients, chlorophyll-a) and environmental parameters (temperature, rainfall) on the temporal variation in the growth and survival of early juvenile (~3 mm) H. scabra reared in floating hapas. Five trials where the juveniles were reared for 60 days each in the eutrophic coastal waters of Bolinao, the Philippines were conducted during different months over 2 years. Significant differences in the growth and survival of juveniles among trials were found. Absolute growth rates (AGR) ranged widely (0.01–0.09 g/day). Trials with high AGR of juveniles (0.07–0.09 g/day) during the first 30 days of rearing had significantly higher chlorophyll-a (chl-a) in biofilm (15.9–27.5 mg/m2) and lower AI. Conversely, during the subsequent 30 days, trials with high AGR of juveniles (0.06–0.11 g/day) had significantly lower chl-a and higher AI. Multivariate analyses showed that chl-a in biofilm, AI and nutrients in the water column are good indicators of periphyton quality and juvenile growth rates in floating hapas. Further, this study validates the expansion of the feeding mode of juveniles from primarily grazing on microalgae, to feeding on detritus and heterotrophs as they grow. These results are important in optimizing ocean nursery systems.

Development of the Soviet Nursery System in 1930–1940 yy.

The results of historical and medical research of development of nursery system in 1930–1940 in the Soviet Union are presented in this publication. Large-scale involvement of women to creation of socialist society has demanded to get rid of house work, care of their own child, and as a result creation of network of maternal and child health institutions. The nurseries have become the most common. Thanks to dynamic building and construction work of child care facilities in 1932–1933 yy up to 80% of children had places in nurseries in large industrial centres, and up to 66% of children had places in seasonal nurseries in collective farms. The increase of nursery capacity in the USSR in1938 for previous two years was 30.5%. Despite massive success in the field of nursery network creation, there were some mistakes during construction and some drawbacks in health services for ill and healthy children were revealed. For instance: irrational nursery space planning, inability to isolate one group from another during quarantine in case of childhood infection, massive morbidity with childhood infection in nurseries, incompetence of medical staff, insufficient nurseries capacity management in case of high necessity of nursery care. High importance was given to creation of nursery isolation hospitals for patients and children on a quarantine for solving these problems.

Economic Value of Mangrove Forest in Pannikiang Island, Barru District, South Sulawesi, Indonesia

Mangrove forest area is a very important area in Pannikiang. Mangrove forests in this area are used by the community as a livelihood. This study wants to learn about the economic valuation of mangrove forests on Pannikiang Island, Makassar. A total of 60 respondents were interviewed in depth. Benefit value, calculated using the value of Direct Use, Indirect Use Value, Option Value, Existence Value, and Total Economic Value. The total economic value of mangrove forests on the Pannikiang Island Rp. 16,155,904,158/year or Rp. 183,007,523,300/ha/year. The patterns and manner of utilization, resource mangrove ecosystem is using gear nets, traps, hooks iron in catching shrimp and crab, develop nursery mangrove system with scraped or directly from the fruit, using gear nets, traps, using an iron hook and set traps crab (rakkang) in catch crabs, catch the bat, found in the mangrove forest, using the net, made bridge length, and the middle of the mangrove forest tower area so that the end could be resting and go up to the tower to see the entire expanse of the forest mangrove Pannikiang Island, wanamina cultivation, which combines farming of fish/shrimp with mangroves.

Using poly-β-hydroxybutyric as an additional carbohydrate for biofloc in a shrimp Litopenaeus vannamei bioflocs nursery system with brackish water

Biofloc technology involves manipulation of the C/N ratio to convert toxic nitrogenous wastes into useful microbial protein and helps improve the water quality in a closed system. Poly-β-hydroxybutyric (PHB) has been demonstrated to have positive effects on aquatic animals in an aquaculture system. A 40-day lab scale trial was carried out to investigate the potential of PHB as an additional carbohydrate for a shrimp Litopenaeus vannamei bioflocs nursery in brackish water. Three methods of carbohydrate supplementation were investigated. The first method was the addition of glucose daily at a percentage of 75% of the feed (GLU-group). The second method was the addition of PHB plus glucose; when the total ammonia nitrogen (TAN) level above 2 mg L−1 was observed, glucose was added, 6 g C to 1 g TAN (PHB + GLU-group). The third method was the addition of PHB only (PHB-group). During the 40-d trial, most of the ratios of dissolved organic carbon to total ammonium nitrogen (DOC/TAN) were maintained at 20 in the three groups. The average concentration of TAN in the PHB + GLU-group (0.23 ± 0.19 mg L−1) was significantly lower than those of the GLU-group (0.28 ± 0.26 mg L−1) and the PHB-group (0.30 ± 0.33 mg L−1) (P < .05). The average concentration of nitrite nitrogen in the PHB-group (0.16 ± 0.24) was significantly lower than those of the GLU-group and the PHB-group (P < .05). The concentrations of TAN and nitrite nitrogen from the PHB + GLU-group were more stable than those from the PHB-group and GLU-group. Nitrate nitrogen accumulated, as expected, in the three groups, and no significant differences were observed (P > .05). The survival rate and final weight in the PHB + GLU group were significantly higher than those of the other groups (P < .05). The food conversion ratio of the PHB group (1.52 ± 0.23) was significantly lower than those of the other groups. Taken together, our results showed that PHB is a favorable and convenient additional carbohydrate for shrimp Litopenaeus vannamei biofloc nurseries in brackish water. PHB + GLU was the best carbohydrate supplementation method.

Restoring forests: regeneration and ecosystem function for the future

Conventions and policies for biodiversity conservation and climate change mitigation state the need for increased protection, restoration and climate change adaptation of forests. Much degraded land may be targeted for large-scale forest restoration, yet challenges include costs, a shortage of regeneration material and the need for restored forests to serve as a resource for communities. To ensure ecosystem function for the future, forest restoration programs must: (1) learn from the past; (2) integrate ecological knowledge; (3) advance regeneration techniques and systems; (4) overcome biotic and abiotic disturbances and (5) adapt for future forest landscapes. Historical forest conditions, while site-specific, may help to identify the processes that leave long-term legacies in current forests and to understand tree migration biology/population dynamics and their relationship with climate change. Ecological theory around plant–plant interactions has shown the importance of negative (competition) and positive (facilitation) interactions for restoration, which will become more relevant with increasing drought due to climate change. Selective animal browsing influences plant–plant interactions and challenges restoration efforts to establish species-rich forests; an integrated approach is needed to simultaneously manage ungulate populations, landscape carrying capacity and browse-tolerant regeneration. A deeper understanding of limiting factors that affect plant establishment will facilitate nursery and site preparation systems to overcome inherent restoration challenges. Severe anthropogenic disturbances connected to global change have created unprecedented pressure on forests, necessitating novel ecological engineering, genetic conservation of tree species and landscape-level approaches that focus on creating functional ecosystems in a cost-effective manner.

Nursery and Grow‐Out Strategy Optimization in Bay Scallop Argopecten irradians Aquaculture

AbstractThe northeastern United States once had a robust and profitable wild bay scallop Argopecten irradians commercial fishery that generated revenue for fishermen and quality seafood for regional consumption. Since the 1980s, bay scallop landings have been declining due to overfishing, habitat loss, and coastal water quality degradation. There is potential for bay scallop aquaculture to fill the void left by the decline of the wild fishery. However, further investigation into optimizing growth and survival in the nursery, grow‐out, and overwintering phases is needed. Growth and survival as related to stocking density were investigated during the nursery phase using a floating downweller system. Over the 6‐week nursery period, survival, growth, and food availability were documented in relation to flow rates and initial stocking densities. Initial bay scallop stocking density largely predicted mean bay scallop growth rates (mm/d) over the 6‐week observation period but had little impact on survival. At the end of the observation period, bay scallops were moved out of the nursery system to three different grow‐out locations on Cape Cod. At each location, bay scallops were stocked into three surface gear types (floating bags of two different mesh sizes [6 or 9 mm] or hanging trays) and bottom cages to investigate grow‐out phase strategies. In exposed, high‐energy environments, the surface gear was susceptible to damage, and bay scallop growth rates and survival were impacted. In low‐energy environments, growth rates and survival were similar between surface and bottom gear. In both low‐ and high‐energy environments, bay scallop growth rates (mm/d) declined significantly once temperatures dropped below 15°C. Observed growth rates and survival in the configurations examined in this study indicate that bay scallop farming on New England shellfish farms is viable.

Advances in citrus propagation in Brazil

Abstract Citriculture is an important agricultural activity worldwide, occupying a relevant position in Brazil among fruit tree production for both the fresh fruit market and the processing industry for concentrated orange juice export. Recent advances in the country’s citrus nursery tree production system have been essential to guarantee the efficiency and competitiveness of Brazilian citriculture. The implementation of strict laws and regulations to produce trees in protected environments and improvements in production techniques for basic citrus propagation materials and nursery trees in São Paulo state has excluded the insect vectors of destructive diseases such as citrus variegated chlorosis and huanglongbing, making this an innovative reference system for citrus propagation around the globe. The main aspects of these advances are presented and discussed in this review, including advances in propagation techniques, scion and rootstock selection, genetic characterization and certification, tree size standards, cultural practices such as irrigation and fertilization for the production of citrus propagation materials and nursery trees, and nursery management tools.

Raising the Mexican Tetra Astyanax mexicanus for Analysis of Post-larval Phenotypes and Whole-mount Immunohistochemistry.

River and cave-adapted populations of Astyanax mexicanus show differences in morphology, physiology, and behavior. Research focused on comparing adult forms has revealed the genetic basis of some of these differences. Less is known about how the populations differ at post-larval stages (at the onset of feeding). Such studies may provide insight into how cavefish survive through adulthood in their natural environment. Methods for comparing post-larval development in the laboratory require standardized aquaculture and feeding regimes. Here we describe how to raise fish on a diet of nutrient-rich rotifers in non-recirculating water for up to two-weeks post fertilization. We demonstrate how to collect post-larval fish from this nursery system and perform whole-mount immunostaining. Immunostaining is an attractive alternative to transgene expression analysis for investigating development and gene function in A. mexicanus. The nursery method can also be used as a standard protocol for establishing density-matched populations for growth into adults.

Effects of Fertilizer on Media Chemistry and Red-flowering Currant Seedling Growth Using a Subirrigation System

Water conservation in nursery systems is an ever-increasing focus, yet there is relatively little guidance for growers producing seedlings intended for restoration regarding how practices such as subirrigation influence plant growth in the nursery and after outplanting. Our study investigated red-flowering currant (Ribes sanguineum Pursh) seedling development and early field performance using different fertilizer treatments under a subirrigation regime. Plants were fertilized with 1) incorporated organic fertilizer, 2) incorporated controlled-release fertilizer, 3) top-dressed controlled-release fertilizer, or 4) water-soluble fertilizer. We found that seedlings grown with organic fertilizer used significantly less water than all other treatments. Media electrical conductivity (EC) levels were significantly greater in the organic fertilizer treatment, and EC values in the top portion of the media were significantly greater than the middle or bottom portions for all fertilizer treatments. The remaining subirrigation water at the end of 22 weeks held 17% of applied nitrogen (N) from the water-soluble fertilizer treatment and less than 1% of applied N from the other fertilizer treatments. We observed no differences in plant morphology among fertilizer treatments. Seedlings were subsequently out-planted into low- and high-competition treatments, where myriad factors indicated reduced growth among high-competition compared with low-competition plots, highlighting that competition for soil water limited seedling performance. These results indicate that a variety of fertilizers can be used to grow red-flowering currant under subirrigation and that postplanting growth is enhanced with control of competing vegetation.

Predicting Influenza Outbreak in One Nursery and in the Community Using the Nursery and School Absenteeism Surveillance System

Predicting Influenza Outbreak in One Nursery and in the Community Using the Nursery and School Absenteeism Surveillance System

Effects of sediment enrichment with macroalgae, Sargassum spp., on the behavior, growth, and survival of juvenile sandfish, Holothuria scabra

To scale-up culture production of the sea cucumber Holothuria scabra using ocean grow-out systems, bottlenecks in enhancing the growth and survival of juveniles need to be addressed. As the selection of release sites is fraught with uncertainty, organic enrichment of sediment using dried Sargassum spp. to increase food abundance (i.e., microalgae and bacteria) may be a viable option to optimize ocean nursery systems. The effects of sediment enriched with dried Sargassum spp. on the diel burying behavior, growth, and survival of juvenile (>3 g) sandfish were investigated in the field for 60 days using sea pens (2.25 m2) with a stocking biomass of 66 g m−2, and in glass tanks (0.045 m2) with the same stocking biomass (∼3 g individual tank-1) in the laboratory for 30 days. Enrichment with Sargassum markedly changed sediment characteristics. Although diurnal burying behavior did not vary significantly between treatments, a greater percentage of juveniles in enriched pens and tanks remained buried during the daytime compared to unenriched pens. Without protection from predators in the wild, all juveniles from enriched pens survived compared to those from unenriched pens (85 ± 10%) after 7 days. After 30 days, absolute growth rates (AGR) of juveniles in enriched pens (0.51 ± 0.06 g day-1) and tanks (0.82 ± 0.27 g day-1) were significantly higher compared to unenriched pens (0.13 ± 0.04 g day-1) and tanks (0.49 ± 0.19 g day-1). Results showed that mean sediment chlorophyll-a content of ∼4 μg g-1 in sea pens enriched with Sargassum spp. could hasten the growth of ∼3 g juveniles to >20 g in 30 days. This study demonstrated that the organic enrichment of sediment is a viable option to optimize the growth of sandfish in an advanced ocean nursery system that may significantly improve survival prior to release for grow-out.

The Nigerian catfish (Clarias gariepinus) pisciculture systems: reservoirs of multidrug-resistant bacteria.

Control of operations of catfish farmers still lacks in Nigeria due to the absence of catfish inspection programmes by relevant regulatory agencies. Thus, this study aimed at performing comprehensive surveillance of Nigerian catfish pisciculture systems so as to provide empirical evidence on the extent of contamination with multidrug-resistant bacteria due to potential abuse of standard operational procedures by catfish farmers. One-way analysis of variance was performed on pond water and catfish samples which were randomized with the Wei's-Urn randomization modelling technique. Ceftriaxone-selected bacterial colonies isolated from catfish and pond water samples collected from nursery and grow-out pond systems were tested for multidrug resistance. Haemocytotoxigenic and Shiga toxigenic virulence traits in multidrug-resistant colonies, as well as detection of hyper-Ambler class C-(AmpC) beta-lactamase and carbapenemase production, were also performed using phenotypic/molecular methods. Of the 648 ceftriaxone-selected bacterial isolates examined in this study, 515 isolates were found to be multidrug-resistant bacteria, of which 366 isolates were characterized as pathogenic multidrug-resistant bacteria. Both nursery and grow-out ponds had high frequencies of bacterial resistance to ampicillin (86-93%), cotrimoxazole (47-87%) and chloramphenicol (95-100%). However, high frequencies of bacterial resistance to amoxicillin/clavulanic acid (75-83%) were only observed in the grow-out ponds. Also, hyper-AmpC beta-lactamase-producing multidrug-resistant bacteria were only seen in the grow-out ponds. Isolated multidrug-resistant bacteria were confirmed as Enterobacter cloacae, Citrobacter freundii, Bacillus cereus, Pseudomonas aeruginosa, Escherichia coli and Enterococcus faecalis. The findings in this study corroborate the urgent need for some form of international mediation to urge the Nigerian government and her regulatory agencies to commence monitoring of catfish pisciculture operations since multidrug-resistant bacteria could be transmitted to humans. Our study provided empirical evidence that revealed the misuse/abuse of antibiotics during pisciculture operations in Nigeria; thus, constituting these pisciculture systems into reservoirs of multidrug-resistant bacteria.