Juvenile Production Research Articles

Production of tambaqui juveniles (Colossoma macropomum) and arugula microgreens (Eruca sativa) in small-scale aquaponic systems: technical and economic viability

Production of tambaqui juveniles (Colossoma macropomum) and arugula microgreens (Eruca sativa) in small-scale aquaponic systems: technical and economic viability

Ecotoxicity of bioinsecticide spinosad to soil organisms: Commercial formulation versus active ingredient

Spintor® (SPIT®) is a commercial formulation of a bioinsecticide with the active ingredient Spinosad (SPIN). Despite the efforts of regulatory agencies, there still is a lack of information regarding short- and long-term exposures to soil-dwellers, as well as effects at environmentally relevant concentrations. This work aimed to evaluate the effects of SPIT® and SPIN, on the oligochaete Eisenia fetida, and the arthropod Folsomia candida. For this, natural soil was spiked with environmentally relevant concentrations (0.00–1.49 mg of the active ingredient·kg−1 of dry soil) to assess avoidance behaviour in E. fetida and reproduction effects on both species. Further, in E. fetida adults exposed for 2- and 28-day biomarkers of oxidative stress, energetic reserves, neurotoxicity and genotoxicity were evaluated. A significant reduction in juvenile production for F. candida was observed for SPIT® at ≥0.66 mg kg−1 and SPIN at ≥0.13 mg kg−1, and although no effect was observed on E. fetida reproduction, the oligochaeta revealed a tendency to avoid soil spiked with SPIT® at 0.44, 0.66 and 1.49 mg kg−1. The sub-individual responses of E. fetida demonstrate genotoxicity upon exposure to SPIT® and SPIN for 2 days. The 2-day exposures of SPIT® and SPIN seem to induce defence mechanisms, and in general, SPIN exerted higher effects than SPIT® on the oligochaetes. Overall, the pro-oxidant performance and energy metabolism pathways were disrupted in both exposures to SPIT® and SPIN. The results suggest that spinosyns-based products can have an impact on soil arthropods F. candida and oligochaete's health, possibly affecting their essential functions in terrestrial ecosystems.

Reproductive performance of lumpfish (Cyclopterus lumpus, L. 1758) females: Effects of integrated photoperiod and temperature manipulations on sexual maturation and spawning.

A successful control of sexual maturation is crucial for year-round production of lumpfish juveniles destined as cleaner fish in Atlantic salmon aquaculture. This study investigated the combined effects of photoperiod and temperature manipulations on sexual maturation and spawning in lumpfish females. Lumpfish juveniles were exposed to simulated natural and nine-month compressed annual photoperiods, with subsequent temperature elevation. Body weight (BW), condition factor (K), gonadosomatic index (GSI), ovarian development, plasma levels of 17β-estradiol (E2), testosterone (T) and 11-ketotestosterone (11-KT), and spawning were assessed. Compressing the natural photoperiod caused a clear increase and decrease in GSI, T, 11-KT and E2 towards and during the spawning period. Before the temperature elevation, GSI, T, 11-KT, E2 and ovarian development were advanced in the compressed photoperiod. After the temperature elevation, GSI, T, 11-KT and E2 fluctuated more in the compressed photoperiod, while in the natural photoperiod, E2 declined, and GSI, T and 11-KT increased. Spawning was advanced by 1 month in the compressed photoperiod compared to the natural photoperiod. Temperature elevation led to higher levels, earlier peaks and declines of T, 11-KT or E2 in both photoperiods, and advanced spawning by 1.5 months in the compressed photoperiod compared to the natural photoperiod. Temperature elevation also led to increased ovulation recruitment and increased cumulative weight of spawned eggs in the natural photoperiod. Compressing the natural photoperiod and elevating temperature can thus advance sexual maturation and spawning in lumpfish females. Due to the lower amounts of spawned egg weights in the high temperature compressed photoperiod, further studies on effects of photoperiod and timing of temperature manipulations on spawning, fecundity and egg quality could optimize the photothermal manipulations on lumpfish broodstock.

REPRODUCCIÓN Y CULTIVO LARVARIO DEL PEZ PAYASO MARRÓN (Premnas biaculeatus) BAJO CONDICIONES CONTROLADAS

<p><strong>Background:</strong> Interest in ornamental marine fish, especially species associated with coral reefs, is rapidly growing. Most of the fish traded come from the wild, and collection methods harm coral reefs and cause massive mortalities in non-target species. To make the activity sustainable, it is necessary to develop aquaculture biotechnologies to reduce the collection of wild organisms and lessen the pressure on their natural environment. <strong>Objective:</strong> To develop protocols for the reproduction and larval rearing of the maroon clownfish (<em>Premnas biaculeatus</em>) for the sustained production of juveniles in captivity. <strong>Methodology:</strong> Two pairs of <em>P. biaculeatus</em> were placed in two aquariums of a recirculating system with filtered seawater. The obtained eggs were incubated in 100 L tanks. The larvae were fed with rotifers <em>Brachionus rotundiformis</em>, <em>Artemia</em> sp. nauplii, and weaned onto a commercial diet. The larvae were measured at hatching and every four days until weaning. <strong>Results:</strong> The clownfish pairs began spawning 4-5 months after being placed in the recirculating system and continued spawning every 15-20 days. The eggs hatched 6-7 days after fertilization (DAF), and the hatched larvae measured 3.4±0.06 mm in total length (TL). At 19 days after hatching (DAH), after completing weaning, they measured between 9.8 to 11.5 mm in TL; at 26 DAH, they measured between 10.8 to 13.1 mm. After one month, between 800 to 1,000 juveniles were obtained for commercialization. <strong>Implications:</strong> The reproduction and larval rearing protocols of the maroon clownfish <em>P. biaculeatus</em> described in this work can be used to obtain juveniles in captivity for commercialization; additionally, they can serve as a basis for developing other protocols for obtaining juveniles of other ornamental marine fish species for commercialization, contributing to the protection of their natural environment. <strong>Conclusion:</strong> The results obtained demonstrated the viability of maintaining <em>P. biaculeatus</em> breeders in captivity and achieving their natural reproduction, larval rearing, and mass production of juveniles throughout the year.</p>

Genetic Parameter Estimates for Growth of Hāpuku (Groper, Polyprion oxygeneios) in Land-Based Aquaculture Using Random Regression Models

Hāpuku (Polyprion oxygeneios) is a promising candidate for aquaculture production in New Zealand. Methods for spawning, juvenile production, and growout to harvest entirely on land, where water quality, pathogens, environmental impacts, and genetic “pollution” can be tightly controlled, have been developed, and genetic improvement to optimise land-based production is the obvious next step. However, estimates of genetic parameters are required to design a rigorous, disciplined, and effective selective breeding program. By using existing data consisting of irregularly spaced repeated measurements of fork length and live body weight collected on wild-collected founders and two generations of captively reared progeny, we evaluated the species’ genetic potential for improvement in growth. We first tested a range of univariate random regression models to identify the best-fitting models for these data. Subsequently, using a bivariate model, we estimated variance components for growth trajectories of fork length and whole body weight. With one to six records available per fish, the best-fitting univariate models included only a fixed effect for contemporary groups and fixed and random genetic third-order Legendre polynomials. More complex models that included full-sib family and/or permanent environmental effects produced unacceptable constrained and/or non-positive-definite solutions. Both traits are moderately heritable at all stages of the growout phase (~0.4–0.5), and the genetic correlation patterns between daily breeding values estimated via the covariance function are different for length and weight. Genetic correlations for length between all pairs of age-specific breeding values are positive and strong (>0.7) and change gradually and smoothly with increasing temporal separation. For weight, these correlations deteriorate more rapidly with increasing time lags between measurements and become negative for some age pairings. We conclude that random regression analyses are a valuable tool for extracting genetic information from irregularly spaced repeated measurements of fish size, speculate that emerging technologies for high-throughput genotyping and phenotyping will add to the value of this approach in the near future, and reason that a breeding strategy that rigorously takes into account the potentially unfavourable genetic correlations between breeding values for weight at some ages will further adapt hāpuku to land-based systems and enhance the profitability commercial-scale production.

Biological monitoring of soil pollution caused by two different zinc species using earthworms.

Zinc oxide nanoparticles (ZnO-NPs) are commonly used in both commercial and agricultural sectors. As a result, ZnO-NPs are extensively discharged into soil ecosystems, creating a significant environmental issue. Therefore, it is crucial to assess their influence on the soil ecology to ensure its secure and enduring utilization in the future. The exact degree of toxicity associated with ZnO-NPs and their ionic form is still uncertain. To address the challenges, the study used the soil bioindicator earthworm species Eudrilus eugeniae as an experimental model to evaluate the effects of two zinc species (ZnO-NPs and ZnCl2) at 100, 250, 500, and 750mgkg-1 and control (0mgkg-1) in garden soil over 28days. The investigation alsoexamined the impact ofexposure on survival, reproduction, neuro-biomarker, avoidance behavior, and accumulation. The highest avoidance rates were 27.5% for ZnO-NP and 37.5% for ZnCl2 at 750mgkg-1. ZnCl2 treatment reduced juvenile production by 3.73 ± 1.73, while ZnO-NPs showed 4.67 ± 1.15. At 750mgkg-1, soils with ZnCl2 (63.3%) demonstrated lower survival rates than those with ZnO-NPs (53.3%), likely because of higher Zn ion levels. After 28days of exposure, ZnCl2 (536.32 ± 11molmin-1) activated AChE enzymes more than ZnO-NPs (497.7 ± 59molmin-1) at the same dose, compared to control (145.88 ± 28 to 149.41 ± 23molmin-1). Nanoparticles and zinc ions bioaccumulated and reacted negatively with the neurotoxic marker AChE, affecting earthworm reproduction and behavior. However, earthworms exposed to ZnCl2 exhibited less intestinal Zn than those exposed to NPs. The present work contradicts the finding that ZnO-NPs have hazardous effects on soil organisms. The results indicate that earthworm E. eugeniae may significantly affect soil metal uptake from metallic nanoparticles (NPs). This may help design NP soil pollution mitigation strategies.The study offers valuable information for establishing a relationship between the environmental toxicity of ZnO-NPs and soil ecosystems.

Ecological aspects of three strains of entomopathogenic nematodes from the department of Lambayeque-Peru

BackgroundEntomopathogenic nematodes (EPN) are used as a biological control agent for different insect pests in agriculture. The genera Heterorhabditis and Steinernema are the most used commercially. For an EPN species to be used as a biological controller, it is necessary to know its ecological aspects, including reproductive potential, movement capacity, and mean lethal concentration (LC50). These aspects were evaluated in three EPN strains isolated in Galleria mellonella larvae collected in the Lambayeque-Peru region, to determine if they are promising as biological controllers. The strains of EPN studied are Heterorhabditis sp. (PC9 strain), H. bacteriophora Poinar (PM10 strain), and Steinernema diaprepesi Nguyen y Duncan (SV19 strain).ResultsHeterorhabditis sp. (PC9 strain) and H. bacteriophora (PM10 strain) had high production of infective juveniles (IJs): 217.750 and 186.800, respectively, while S. diaprepesi (SV19 strain) only reached 84.150 IJs. The movement capacity of Heterorhabditis sp. (PC9 strain) and H. bacteriophora (PM10 strain) reached a depth of 15 cm to parasitize G. mellonella larvae, while S. diaprepesi (SV19 strain) only reached 10 cm. In decreasing order, the LC50 value of S. diaprepesi (SV19 strain), Heterorhabditis sp. (PC9 strain) and H. bacteriophora (PM10 strain) were: 24.03, 13.74, and 8.19 IJs/ml, respectively.ConclusionsHeterorhabditis sp. PC9 and H. bacteriophora PM10 are promising a biological control agent because they present great production of IJs, great displacement capacity, and high pathogenicity against G. mellonella. Additionally, both strains present a mixed search strategy or seeker-hunter (seeker-browser).

Effectiveness study of the dual application of new Indigenous entomopathogenic nematode isolate Heterorhabditis taysearae and entomopathogenic fungi Beauveria bassiana against armyworm (Spodoptera frugiperda)

BackgroundThe fall armyworm, Spodoptera frugiperda (J. E. Smith) (Lepidoptera: Noctuidae), is a polyphagous insect pest species that travel great distances every summer to disperse. They mostly feed on maize and over 350 other crops. In this investigation, two entomopathogens: Beauveria bassiana and Heterorhabditis taysearae, were utilized to test the efficacy of each against S. frugiperda separately and then as a group by inoculating H. taysearae two days after fungal infection.ResultsEvaluations were done on mortality percentage, infective juvenile (IJ) production, and conidia production. The LT50 continually reduced with increases in nematode and fungus concentrations. For the LC50 value, the H. taysearae isolate was 289 IJs/larva after 96 h of treatment, while for B. bassiana isolate, it was 106 CFU/ml after 144 h of treatment. Dual infections with B. bassiana and H. taysearae had a beneficial effect on pest mortality, resulting in 83% mortality, and caused a significant increase in conidia production while utilizing the nematode or fungal separately caused decrease in mortality (63 and 73%, respectively).ConclusionsThe study’s findings indicated a quicker time to death and suggested that combining a moderately pathogenic fungal isolate with nematodes could raise the mortality rate. The mutually beneficial relationship between B. bassiana and H. taysearae controls S. frugiperda.

Reproduction, growth and oxidative stress in earthworm Eisenia andrei exposed to conventional and biodegradable mulching film microplastics

Plastic contamination in agricultural soils has become increasingly evident. Plastic mulching films are widely used in agricultural practices. However, the increased use of biodegradable plastics has, to some extent, replaced their non-degradable counterparts. The fragmentation of plastics generates microplastics (MPs), posing risk to soil functions and organisms. In this study the effects of low-density polyethylene microplastics (PE-MP) and polybutylene adipate terephthalate biodegradable microplastics (PBAT-BD-MP) originating from mulching films on the earthworm Eisenia andrei were studied. The earthworms were exposed to seven concentrations (0, 0.005, 0.05, 0.1, 0.5, 1, and 5 % w/w) based on environmentally relevant levels and worst-case scenarios on soil contamination. Survival, growth, reproduction, and biomarkers for oxidative stress [superoxide dismutase (SOD), catalase (CAT), glutathione reductase (GR), glutathione S-transferase (GST), glutathione (GSH), and lipid peroxidation (LPO)] were analysed. Additionally, the Integrated Biomarker Response Index (IBR) was calculated to assess the overall oxidative stress status of the earthworms. Results showed that PE-MP exposure slightly decreased the biomass of the earthworms towards higher concentrations, whereas PBAT-BD-MPs induced growth at lower concentrations. MPs did not have a significant effect on Eisenia andrei reproduction; however, a slight negative trend was observed in juvenile production with increasing PE-MP concentrations. Both PE-MP and PBAT-BD-MP affected antioxidant system, PE-MPs with changes in CAT and GR levels and PBAT-BD-MPs inducing effects on SOD and LPO levels. Additionally, both MPs exhibited effects on soil parameters, resulting in increased soil pH and water-holding capacity at 5 % concentration. Changes in soil parameters can further affect soil organisms such as earthworms. This study provides understanding of the ecotoxicological effects of conventional and biodegradable microplastics on the earthworm Eisenia andrei. It also shows that MP particles of both conventional and biodegradable mulching films induce oxidative stress, considered as an early-warning indicator for adverse ecological effects, in environmentally relevant concentrations.

Characterization of Springtail (Arrhopalites caecus) for Use in Soil Ecotoxicity Testing.

Springtails (subclass: Collembola) represent one of the most extensively studied invertebrate groups in soil ecotoxicology. This is because of their ease of laboratory culture, significant ecological role, and sensitivity to environmental contaminants. Folsomia candida (family: Isotomidae) is a globally widespread parthenogenetic species that is prevalent in laboratory toxicity testing with springtails. Conversely, Arrhopalites caecus (family: Arrhopalitidae), a parthenogenic globular springtail species, remains untested in soil ecotoxicology. This species is found in diverse habitats, including cave systems and forest leaf litter, and has a global distribution. The sensitivity of A. caecus to environmental contaminants, such as neonicotinoid insecticides, as well as its life history and optimal culturing conditions, are largely unknown. The present study describes the establishment of a pure A. caecus laboratory culture and characterization of its life cycle and culturing conditions. We assessed the sensitivity of A. caecus to various insecticides, including exposures to the neonicotinoid thiamethoxam in soil and through a novel feeding assay as well as to clothianidin and cyantraniliprole in spiked soil exposures. In 7- and 14-day exposures to thiamethoxam in agricultural soil, the 50% lethal concentration (LC50) values were determined to be 0.129 mg/kg dry weight and 0.010 mg/kg dry weight, respectively. The 14-day LC50 for exposure to thiamethoxam via spiked food was determined to be 0.307 mg/kg dry weight. In addition, the 28-day 50% effect concentration for inhibition of juvenile production from cyantraniliprole exposure in the same soil type was 0.055 mg/kg dry weight. Challenges encountered in using this species included susceptibility to mite infestation and low adult survival rates in the 28-day cyantraniliprole test. Environ Toxicol Chem 2024;43:1820-1835. © 2024 The Authors. Environmental Toxicology and Chemistry published by Wiley Periodicals LLC on behalf of SETAC.

A Review of Pacific Salmon Hatcheries in British Columbia, Canada, and Interactions With Natural Populations

Pacific salmon Oncorhynchus spp. hatcheries in British Columbia (BC) have been the major activity of the Salmonid Enhancement Program since 1977. However, the present diminished abundance of Pacific salmon and loss of fisheries in BC called for a review of hatchery effectiveness. The Pacific Salmon Foundation conducted a review resulting in 15 reports publicly available on the Pacific Salmon Foundation marine science website. The review includes evaluations of effectiveness of hatchery production, evidence of interactions with natural salmon populations (including rebuilding natural populations with hatchery‐produced salmon), and future opportunities via genomics. Beyond the estimation of juvenile production and contribution to catches and spawning escapements, the ability to assess effectiveness was limited. The assessments of interactions provided a few examples of positive outcomes, but most were negative. The lack of comparative assessments in purely wild populations seriously limits interpretations of hatchery–wild interactions. Future evaluations of the hatchery effectiveness require more quantitative and integrated assessments of hatchery and wild salmon, open data sharing for public review or research, and related studies could benefit from application of new genomic technologies. This paper presents recommendations to address these needs and calls for regularized reviews of the Salmonid Enhancement Program and its net value to sustainability of BC's Pacific salmon.

Reduced Freshwater Mussel Juvenile Production as a Result of Agricultural and Urban Contaminant Mixture Exposures.

Freshwater mussels provide invaluable ecological services but are threatened by habitat alteration, poor water quality, invasive species, climate change, and contaminants, including contaminants of emerging concern (CECs). Contaminants of emerging concerns are well documented in aquatic environments, including the Great Lakes Basin, but limited information is available on how environmentally relevant mixtures affect freshwater mussel biology throughout their varied life stages. Our main goal was to assess mussels' reproductive output in response to exposure to agricultural and urban CEC mixtures during glochidial development through juvenile transformation and excystment focusing on how exposure duration and treatment affect: (1) the number of glochidia prematurely released by brooding females, (2) glochidial transformation through host-fish excystment, and (3) the number of fully metamorphosed juveniles able to continue the lifecycle. Mussels and host fish were exposed to either a control water (CW), control ethanol (CE), agriculture CEC mixture (AM), or urban CEC mixture (UM) for 40 and 100 days. We found no effect from treatment or exposure duration on the number of glochidia prematurely released. Fewer partially and fully metamorphosed AM juveniles were observed during the 100-day exposure, compared with the 40-day. During the 40-day exposure, CW produced more fully metamorphosed individuals compared with CE and UM, but during the 100-day exposure AM produced more fully metamorphosed individuals compared with the CW. There was reduction in fully metamorphosed juveniles compared with partially metamorphosed for CE and UM during the 40-day exposure, as well as in the CW during the 100-day exposure. These results will be important for understanding how mussel populations are affected by CEC exposure. The experiments also yielded many insights for laboratory toxicology exposure studies. Environ Toxicol Chem 2024;43:1112-1125. © 2024 The Authors. Environmental Toxicology and Chemistry published by Wiley Periodicals LLC on behalf of SETAC. This article has been contributed to by U.S. Government employees and their work is in the public domain in the USA.

Optimizing release strategies for red king crab stock enhancement: Effects of release timing

Red king crab, Paralithodes camtschaticus, was commercially important around Kodiak, Alaska, USA, in the 1960s and 1970s; however, the stock crashed in the late 1970 s and has remained closed since 1983. The lack of recovery inspired consideration of stock enhancement through the release of hatchery-reared juveniles as a means to bolster the wild population. We examined the effects of release timing on in situ survival of hatchery-reared red king crab by releasing juveniles in June, August, and September 2015 in Trident Basin, Kodiak. We monitored densities inside and outside of release plots for six months using quadrat counts to determine loss and emigration rates. Relative predation risk was determined using tethering experiments performed after each release, and predator densities were quantified using quadrat counts and predator transect counts. Initial mortality over the first 24 h was approximately 53%, and subsequent mortality rates decreased with month-of-release, likely due to a combination of larger size-at-release and seasonal changes in predation. Although predator density was consistent over time, relative predation risk of tethered crabs decreased with season, suggesting later releases may be beneficial. However, the extended hatchery rearing period needed for later releases presents other challenges, including cannibalism, and the potential for developing maladaptive traits. Stock enhancement programs must balance these trade-offs to maximize overall success. Early releases of small juveniles immediately after settlement may be optimal if large-scale hatchery communal rearing results in significant juvenile production loss and/or hatchery conditioning is impractical.

Effects of pyroligneous acid on acute, chronic, and cyto-genotoxicity to earthworms (Eisenia fetida)

The pyroligneous acid (PA), or wood vinegar, is a byproduct of wood carbonization during the slow pyrolysis process. PA is recognized globally as a safe compound for agriculture due to its various beneficial properties, such as antioxidant, antibacterial, antifungal, and termiticidal properties. However, the impact of different PA concentrations on beneficial soil organisms, such as earthworms has not been investigated. The present study aims to understand the effects of different PA concentrations on earthworm Eisenia fetida. The earthworms were exposed to nine different concentrations of PA in soils, including their control. The acute toxicity assay was performed after 14 days of exposure, and the chronic toxicity assay was performed up to 8 weeks after exposure. The results from the acute toxicity assay demonstrated no significant effect on earthworm mortality. The chronic toxicity assay showed that lower PA concentrations (0.01–0.2% of weight/weight PA in soil) promoted cocoon and juvenile production in soils, whereas higher PA concentrations (0.5 and 1%) had a negative effect. These findings highlight the potential of PA to enhance soil fertility at lower concentrations, up to 0.2%, by stimulating worm activity and subsequent manure production. The outcomes of this study have significant implications for the careful management of PA concentrations within agricultural operations.

Juvenile production technology for tiger shrimp, Penaeus monodon, through different stocking density using a recirculation system

AbstractAquaculture recirculation technology has evolved in recent years, as it can save water use and maintain good water quality during tiger shrimp fry rearing and ultimately increase juvenile production. The recirculation technology in this experiment is expected to be adopted by small‐scale tiger shrimp seed farmers. This study aims to develop the technology for producing a juvenile tiger shrimp recirculation system to support shrimp cultivation in ponds. The recirculation system container comprises a biofiltration tank filled with oysters, seaweed, and tilapia. Containers to keep tiger shrimp larvae alive in the recirculation system use a round‐shaped container with a volume of 2 m3. Tiger shrimp larvae were cared for at; A. density of 2000 individuals/m2; B. density of 1500 individuals/m2; and C. density of 1000 individuals/m2. This study found that the survival rate of tiger shrimp in treatments C and B were high, reaching 96.800b ± 2.716% and 91.62b ± 3.432%, respectively, while survival in treatment A was the lowest, at 81.700a ± 4.715%.

The Australian red-clawed crayfish (Cherax quadicarinatus Von Martens 1868) is a promising aquaculture object for the south of the Russian Federation

The paper presents information about a promising aquaculture object for the south of the Russian Federation - the Australian red-clawed crayfish Cherax quadicarinatus Von Martens 1868. A brief description of its biological characteristics, which are the main factor in the development of specific biotechnologies for its commercial cultivation, is given. The main limiting factor in the artificial cultivation of this species is water temperature. The article indicates that for Russian conditions, three possible directions for growing Australian crayfish can be distinguished: in ponds in the southern regions of Russia in natural climatic conditions (summer); in ponds, cages and pools on warm waters of energy facilities in the summer; in closed water supply installations – year-round. A technology has been proposed for combined cultivation of crayfish, in which the production of juveniles is carried out in controlled basin conditions, and the cultivation of commercial products in earthen ponds in warm seasons, when the water temperature corresponds to the biological needs of the species.

Reproductive performance of Zebra Fish (Danio rerio) exposed to palm oil mill eflluent in chronic toxicity

Palm Oil Mill Effluent (POME) is potentially harmful to the aquatic environment. POME contains high organic material including COD (Chemical Oxygen Demand), BOD (Biochemical Oxygen Demand) TTS (Total Suspended Solid) and various type of heavy metals. of zebra fish (Danio rerio). Reproductin has an important role in producing new individuals which directly affect the population. Impaired reproductive performance potentially impairs juvenile production optimization. The present study investigated how sub-chronic toxicity of POME impact the reproductive performance used Completely randomized Design (CRD) in three treatments and four replicates based on value of LC50-96 hours (5.156 ml/l): Control (0 ml/L), treatment A 10% POME (0,5 ml/L), treatment B 20 % POME (1 ml/L). The fecundity, relative fecundity, GSI, and egg diameter were analyzed. Data was analyzed with Analysis of Variance (ANOVA) and followed with Least Significance Difference (LSD) test. Results showed that fecundity in treatment A (149 ± 38.70) and treatment B (85± 11.35) were significantly decreased compared to the control (219 ± 42.38) (P<0.05). While relative fecundity significantly decreased in treatment B (0.33 ± 0.13) rather than control (0,87 ± 0,14). Significantly decline is also observed on GSI in tretment A (4.79 ± 2.55%) and treatment B (2.55 ± 0.21%) compared to control (6.96 ± 1.70%). While the egg diameter only shows a significantly decline in treatment B (0.57 ± 0.18 mm) compared to control (0.71 ± 0.27 mm).

Thermal stress-stimulated ZnO toxicity inhibits reproduction of freshwater crustacean Daphnia magna

Elevated temperatures due to climate change pose a variety of environmental risks to the freshwater ecosystem. At the same time, zinc oxide (ZnO) has become widely used and has entered the freshwater environment. As thermal stress may potentially impact the physicochemical properties of ZnO, its toxicity to freshwater organisms in the face of global warming is poorly understood. The potential effects on reproductive performances, including oogenesis, are of particular concern. In this study, we investigate the reproductive performances and related mRNA abundance of the zooplankton Daphnia magna under conditions of ZnO exposure and heat stress. The results revealed that ZnO and elevated temperature delayed maturity and juvenile production of D. magna. Histological observations indicated that oogenesis was inhibited, and the number and size of oocytes were reduced in the condition of ZnO exposure under heat stress. Eventual offspring in the same treatment exhibited decreased numbers, size, and quality. Congenital juvenile anomalies were increased, such as deformed eye, and impaired antenna and tail spine. Moreover, both ZnO and elevated temperature treatments inhibited expression levels of reproduction-related genes (vtg, EcR and VMO1) and induced the dmrt93b gene involved in the production of male offspring. Furthermore, we found that D. magna tried to cope with ZnO and thermal stress by upregulating hsp90, HIF-1α and HIF-1β. ZnO and heat stress inhibited the reproductive capacity of D. magna, produced deleterious effects on reproduction-associated physiological pathways, and damaged reproductive outcomes.

Effect of feeding semi-moist diet as a practical strategy to reduce feed costs in tilapia juvenile production

Tilapia (Oreochromis niloticus) is one of the species with the greatest increase in production worldwide. However, the continuous increase in the price of ingredients, and consequently in the diet costs may limit the expansion of the sector. Several alternatives to reduce feed costs are currently under study, as the use of practical press-pellet semi-moist diet that can be manufactured on farm. This study evaluates five levels of replacement (0, 25, 50, 75, and 100%) of a commercial diet by a practical (press-pellet semi-moist) diet and its effect on zootechnical performance, carcass proximate composition, as well as somatic and economic indexes in tilapia juveniles (9.48 g). After 56 days, survival and condition factor did not differ significantly between treatments. Final weight, daily weight gain, feed conversion, and specific growth rate had a negative linear effect as the practical diet increased, while carcass yield had a positive linear effect. Carcass crude protein content was higher in fish fed with 100% practical diet, while crude lipid had the lowest content in this same treatment. As for economic indexes, the estimated cost of feeding decreased as a function of the practical diet inclusion, with a final saving of US$ 8.68 per thousand of juveniles produced (100% replacement).

Spatial patterns of resource subsidies in Great Lakes tributaries from migratory fishes

Migratory fish can influence the stream ecosystems where they spawn by depositing large amounts of energy rich eggs, carcasses, and excrement which can increase primary and secondary productivity. Past research in the Great Lakes has focused on individual tributaries; accordingly, there is a poor understanding of how wide-spread resource subsidies are amongst tributaries. To determine which Great Lake tributaries received subsidies, we compared carbon stable isotope values (δ13C) of resident stream fishes above and below 54 barriers (e.g., low-head lamprey weirs, natural waterfalls) in 31 tributaries. Subsidies, as indicated by the difference in δ13C values above and below barriers, were common. The magnitude of the subsidy varied among Great Lakes with Lake Superior having significantly larger subsidies than the other three lakes. Barrier type (complete, partial) was not related to subsidy magnitude; however, the classification of barrier type was imperfect. Correspondence analysis of regional and local environmental factors showed that large subsidies were associated with oligotrophic streams with steep channels on the Canadian Shield with little agricultural land. The association between subsidies and canopy cover and substrate size were poor. Migratory fish supply resource subsidies to rivers across the Great Lakes basin, though their magnitude is contextually dependent. The presence of barriers are likely limiting the production of migratory fishes that depend on streams for juvenile production. The importance of resource subsidies should be considered when decisions are made about the fate of existing, and the construction of new, barriers that may reduce stream productive capacity.