Aquarium Research Articles

Fine‐tuning the performance of abundance estimation based on environmental DNA (eDNA) focusing on eDNA particle size and marker length

AbstractReliable abundance estimation is a primary challenge in environmental DNA (eDNA) analysis, which has been addressed by considering the effects of eDNA transport and degradation. However, these eDNA spatial dynamics depend on the cellular and molecular structure of eDNA, with its persistence state (particle size and DNA fragment length) being essential for improved abundance estimation. To address the issue, we used datasets obtained from two types of aquarium experiments (targeting zebrafish [Danio rerio] and Japanese jack mackerel [Trachurus japonicus]) and compared the relationships between eDNA concentration and species abundance among different eDNA size fractions and target marker lengths. We reared the fish in experimental tanks with different individual numbers or biomass densities, filtered rearing water using different pore size filters, and quantified eDNA concentrations targeting different fragment lengths or genetic regions. Consequently, both experiments showed that the accuracy and sensitivity in abundance estimation were improved (i.e., R2 values and slopes of linear regressions increased) when targeting eDNA at the 3‐ to 10 μm size fraction. On the contrary, targeting eDNA at the >10 μm size fraction yielded a lower R2 value. This result indicates that the relationship between eDNA concentration and species abundance can be worsened when extremely larger size fractions are targeted. Conversely, the target marker length negatively affected the R2 value. This study proposes that the relationship between eDNA concentration and species abundance relies on the complex interactions between the particle size, persistence, and spatial heterogeneity of eDNA in water.

Development and Acceptability of Math Based Reading Module for Enhancing Mathematical Vocabulary of Grade VI Pupils: Inputs in the Brigada Pag-Basa Reading Program 2022

The study focused on determining the acceptability of the Reading Module in Mathematics: in enhancing the Mathematical Vocabulary for Grade Six Pupils of Kapalaran Elementary School during the conduct of BE Brigada Pag-basa School year 2022. The study's respondents were the thirty (30) selected Grade Six pupils in Mathematics subject of Kapalaran Elementary School using simple random sampling utilizing the fish bowl technique, and twenty (20) selected teacher respondents using stratified sampling technique. More so, the researchers used quasi-experimental and descriptive method of research. The level of acceptability of the developed reading module was assessed in terms of its content, clarity, appeal to the target user, originality, knowledge questions, applicability, and format using the descriptive method of research. The study found out that there is an increase in the posttest means score of the grade six pupils at after being exposed to the Reading Module which means that the respondents gained more Vocabulary Understanding and their performance in will be improved. Then, the null hypothesis was rejected for the significant difference on the level of Vocabulary Understanding of grade six pupils at before and after exposure to the reading module in mathematic VI as revealed by the pretest and posttest with respect to the different topics. Finally, the Reading Module in Mathematics were found ‘Much Acceptable. The study concluded that the pupils obtained a high performance in the post-test as revealed by the respondents with the used of the Reading Module in Mathematics VI. Lastly, the Reading Module in Mathematics VI is an effective tool for reading intervention and in elevating the progress of vocabulary and understanding on the part of the pupils.

Flow patterns in circular fish tanks and its relations with flow rate and nozzle features

The main aim of this research is to study the effect of flow rate, diameter and number of nozzles on the rotational velocity, impulse force and average velocity of water in circular fish tanks. The results indicated that, the rotational velocity increases with increasing flow rates from 5 to 75 m3 h−1 by using 10 and 15 mm nozzles diameter with nozzles number of 5, 10, 15, 20, 25 and 30. The same results were also obtained when 20 and 25 mm nozzle diameter with nozzles number of 3, 6, 9, 12 and 15 were used. The impulse force of water decreases with increasing nozzle diameter from 10.0 to 15.0 mm with 5, 10, 15, 20, 25 and 30 nozzles and from 20.0 to 25.0 mm with 3, 6, 9, 12 and 15 nozzles. When the nozzle diameter increased from 10 to 25 mm the impulse force of water decreased with 15 nozzles. The average velocity of water decreases with increasing nozzles diameter from 10.0 to 15.0 mm with 5, 10, 15, 20, 25 and 30 nozzles and from 20.0 to 25.0 mm with 3, 6, 9, 12 and 15 nozzles. When the nozzle diameter increased from 10 to 25 mm, the average velocity ranged from 1.07 to 48.76 cm s−1 for all treatments under study.

Analysis of the Persistence and Particle Size Distributional Shift of Sperm-Derived Environmental DNA to Monitor Jack Mackerel Spawning Activity.

Environmental DNA (eDNA) analysis holds great promise as an efficient and noninvasive method to monitor not only the distribution of organisms but also their spawning activity. In eDNA analysis-based monitoring of spawning activity, the detection of sperm-derived eDNA is a key point; however, its characteristics and dynamics are completely unknown. The present study focuses on the persistence and particle size distribution (PSD) of eDNA derived from the sperm of Japanese jack mackerel. First, we investigated the time-dependent degradation and the PSD of sperm-derived eDNA by artificially adding sperm to seawater. Next, we kept fish in tanks and examined the changes in eDNA concentration and PSD before and after spawning. The results of two experiments showed that the degradation of sperm-derived eDNA proceeded rapidly, with PSD shifting to a smaller size regardless of the DNA region (Cyt b or ITS1). Additionally, it was shown that the nuclei and mitochondria released from sperm through degradation had a size distribution that was not simply dependent on each organelle size. These results will contribute to elucidating the characteristics and dynamics of eDNA specifically during the spawning season and to further developing eDNA analysis as a powerful tool for the monitoring of spawning activity.

Conteo automático de larvas de peces utilizando visión por computadora basado en redes neuronales

Fish larvae counting is a technique applied in aquaculture to determine the efficiency of the induction stage and to know the number of fertilized larvae. For this reason, the research aims to improve the count of larvae under 3 fundamental pillars: precision, error and time. For this, we carried out an experimental investigation under a completely randomized design with two counting systems: traditional and artificial vision; each one with 10 repetitions, with 2000 larvae; Later, we carried out the count by means of artificial vision using a camera that captured images of a fish tank with moving fish. The results show that the proposed method is feasible for counting larvae, with 92.65% accuracy, 7.41% error and an average time of 61 seconds per repetition in relation to the traditional counting system: accuracy 64.44%, error 35.61% and time 2009.3 s. The developed system can be replicated in the aquaculture sector due to its effectiveness and cost.

Hormone profiles from Cook Inlet, Bristol Bay and aquarium beluga whales

Beluga whales (Delphinapterus leucas) from Cook Inlet (CI), Alaska, are listed as “endangered” because of dramatic declines in abundance, with no indications of population recovery. Serum samples from this population are exceedingly rare. Longitudinal samples from aquarium (AQ) belugas can potentially provide health assessment reference ranges for free-ranging beluga, including reproductive and metabolic hormones. We analysed serum hormone concentrations from CI (n = 6, three females and three males) and Bristol Bay (Alaska; BB; n = 5, four males and one female), alongside AQ (n = 3, two females and one male) belugas, to conduct physiological comparisons of reproductive hormones (progesterone, testosterone and total oestrogens) and metabolic hormones (total thyroxine, triiodothyronine and cortisol) in beluga serum. Oestrogen and progesterone profiles from January through May from two AQ female beluga were typical of non-pregnant, cycling females. CI and BB sex steroid concentrations were within AQ hormone ranges, with the exception of elevated progesterone concentrations in four potentially pregnant females. Both CI and BB belugas had elevated metabolic hormones, which may indicate greater metabolic effort required in the wild environment or capture response. Because sample collection from CI belugas is rare, analysis of even the few samples that we analysed may contribute to the conservation of the small and declining population of genetically distinct CI beluga whales. It is important that each sample collected from free-range CI belugas provides the maximum biological information possible. Continued comparison of hormones in AQ and free-ranging beluga will enhance the interpretation of health data in both groups.

Development and Acceptability of Math Based Reading Module for Enhancing Mathematical Vocabulary of Grade VI Pupils: Inputs in the Brigada Pag-Basa Reading Program 2022

The study focused on determining the acceptability of the Reading Module in Mathematics: in enhancing the Mathematical Vocabulary for Grade Six Pupils of Kapalaran Elementary School during the conduct of BE Brigada Pag-basa School year 2022. The study's respondents were the thirty (30) selected Grade Six pupils in Mathematics subject of Kapalaran Elementary School using simple random sampling utilizing the fish bowl technique, and twenty (20) selected teacher respondents using stratified sampling technique. More so, the researchers used quasi-experimental and descriptive method of research. The level of acceptability of the developed reading module was assessed in terms of its content, clarity, appeal to the target user, originality, knowledge questions, applicability, and format using the descriptive method of research. The study found out that there is an increase in the posttest means score of the grade six pupils at after being exposed to the Reading Module which means that the respondents gained more Vocabulary Understanding and their performance in will be improved. Then, the null hypothesis was rejected for the significant difference on the level of Vocabulary Understanding of grade six pupils at before and after exposure to the reading module in mathematic VI as revealed by the pretest and posttest with respect to the different topics. Finally, the Reading Module in Mathematics were found ‘Much Acceptable. The study concluded that the pupils obtained a high performance in the post-test as revealed by the respondents with the used of the Reading Module in Mathematics VI. Lastly, the Reading Module in Mathematics VI is an effective tool for reading intervention and in elevating the progress of vocabulary and understanding on the part of the pupils.

Effect of potassium supplementation on osmoregulatory and stress response of Pangasianodon hypophthalmus (Sauvage, 1878) with Spinacia oleracea L. in aquaponics.

This study evaluated the effect of different potassium supplementation dosages on the physiological responses of Pangasianodon hypophthalmus reared in an aquaponic system with Spinacia oleracea L. for 60 days. The system comprised of a rectangular fish tank of 168 l capacity (water volume=100 l) with nutrient film technique (NFT)-based hydroponic component with fish to plant ratio of 2.8kg m-3 : 28 plants m-2 in all the treatments. The osmoregulatory and stress parameters of P. hypophthalmus at four different potassium dosages of T1 (90 mg l-1 ), T2 (120 mg l-1 ), T3 (150 mg l-1 ) and T4 (180 mg l-1 ) were compared with C (control, 0mg l-1 ) to examine the potassium level to be applied to aquaponics. The water quality parameters and fish production were found to have no adverse impact due to potassium supplementation. The spinach yield during two harvests, i.e., before and after potassium supplementation, revealed that the yield was significantly higher (P < 0.05) after supplementation with the highest yield in T3 and T4. The osmoregulatory parameters such as plasma osmolality, Na+ , K+ ATPase activity in gill and plasma ionic profile (Cl- , Ca2+ and Na+ ) showed an insignificant variation (P > 0.05) between control and treatments except for higher plasma potassium concentration (1.98 ± 0.19 mmol l-1 ) in T4. The stress and antioxidant enzyme analysis exhibited significantly higher plasma glucose and superoxide dismutase (SOD) activity in gill and liver in T4, whereas cortisol and catalase showed an insignificant difference (P > 0.05). The experimental findings demonstrated that the potassium dosage up to 150 mg l-1 could be suggested as optimum for P. hypophthalmus and spinach aquaponics without impairing the health and oxidative status of P. hypophthalmus.

Behavioral Response of Multiple Rainbow Trout to Vertically Suspended Environmental Enrichment

Vertically suspended environmental enrichment improves the rearing performance of fish during aquaculture production, but the reason for this improvement is unclear. This study documented the behavior of groups of rainbow trout (Oncorhynchus mykiss), as indicated by their in-tank location preferences, in response to vertically suspended structure. The location of both experienced and naïve fish (with or without prior exposure to vertically suspended enrichment) in both barren and enriched tanks was recorded. In-tank locations were significantly different for experienced fish in both barren and enriched tanks but were similar for naïve fish. When observations were combined for both the presence and absence of enrichment, naïve fish locations were significantly different from experienced fish. Locations were also significantly different for all fish in enriched compared to barren tanks. These results indicate that trout location is influenced by the presence of vertically suspended environmental enrichment and that learning from prior experience with enrichment occurs.

Crowded House (Don't Dream It's Over), and: Remembering Our Birds

Crowded House (Don't Dream It's Over), and: Remembering Our Birds Safia Jama (bio) Crowded House (Don't Dream It's Over) Nonsensical beauty. All the plateshe broke on accident rememberhappier days. Honey, it's overbut let's still dream of the early days. That first Christmas in Ireland.That was something. Tinsel walls,hors d'oeuvres I would somedaymake at parties our friends would come to miss. Reminiscentof 1966. My parents' dream kitchen.Pots and pans float and fade. Moreplates explode. One, you broke on purpose, and I now whisper intothe drummer's ear: "Cameras arerolling. Smile." Near the end,Darrell filmed in our living room. Still together, still hanging on,though oatmeal stood hardeningon the stove. Future rocks we'dthrow at one another. 1986 was a good year, maybe the lastgood year for some time. Nowthe lead singer is vacuumingand soon the bassist will play [End Page 137] an organ solo wearing his matadorjacket. Mix and match like thrift storesand flea markets and you and me.Crowded House has not forgotten a single detail, poring over photoalbums. A candelabra lights a corner.I watched this video every night for days—then weeks, until, at last, I walked across greengrass did greet me. Remembering Our Birds I watch sunrise on square windowsthat remind me of those reflective aviator glassespeople sometimes wear— I bought a pair that first spring you visited me,and I wore them without irony,just as I used to wear everything. I left my wardrobe at our old apartmentyou kept like a museum, not moving a singlepillow for a year. Your main design contribution, two Australian zebra finches, purchased that April,our first big rumble. I left, and you replaced my absencewith caged birds. When I returned in the fall, I learned to accept our new pets, the vestige of my leaving, the symbolof our ongoing troubles. When we fought, the birds fought. When we loved, the birds preened and on the afternoonI packed to go to my mother's, you picked a newly [End Page 138] hatched chick off the kitchen floor and placed itin the palm of my hand. You have to keep it warm or it will die!My heart had fled the coup, I didn't care,only I didn't want that warmth to leave,and we named the chick Baby. I went to my mother's for a week, and Baby grew bigger,and the parents raised Baby until she became full grownand belligerent. I had no idea what it meant to save a lifethat would eventually turn around and attack,but then again, I'm not a parent. This morning, I watched the sun rise across the windowswhere I have been nesting here these nine days. Olive, the finch that I chose from the pet store, died last year.You said when you looked into her eyes, she looked backand called in tears when Olive was ill. You took that $15bird to the vet and spent $400. She didn't make it,but I was glad you tried, and so were you. That's when you found Emily, the small white birdmeant to replace Olive. Pip never took to Emily, though,so you kept her in a studio apartment nearby and you told meshe enjoys her solitude and spends her timecontemplating poetry. Last Thanksgiving, our second year apart,you were out all night, and when you came home,Emily had drowned herself in the fish tank,her white feathers bobbing among the Amazon weeds,Sir Claude, your prized fish, looking on perplexed. I said it was a very literary death, and felt disturbed and sorryand fascinated. We were out walking in the snow and youwere trying hard to be kind. [End Page 139] I felt something new,something akin to the frozen snow—the winter sun burning the bare treestouched a pain I needed to feel, to knowthat I am still here and alive. Those first birds, the vestiges of our...

Nora Okja Keller’s Fox Girl: Biopolitics, Necropolitics and a State of Exception

This essay aims to discuss the effects of the Korean government’s hygiene policies on the lives of prostitutes and their families in a U. S. military base village, or kijichon in Nora Okja Kelle’s Fox Girl from the viewpoints of Achille Mbembe’s necropolitics and Michel Foucault’s biopolitics. When it comes to prostitution, it can be said that kijichons were in a state of exception, from Georgio Agamben’s perspective. Using sexually transmitted diseases testing (STD testing) as an example, Fox Gil shows how the hygiene policy pushes ex-Japanese comfort woman and kijichon prostitute Duk Hee into a worse life condition, as a prostitute in a show window, “a fish tank,” while also leading her daughter Sookie into prostitution. Because the policy was unconcerned with the test subjects and their families as a biopolitical attempt to ensure the health of the U. S. soldiers, all of the damage goes to them. The biggest problem is that the completely biased policy was implemented, even though state-regulated prostitution in Korea was abolished in 1948, and the Anti-Prostitution Law was enacted in 1961. The terrible result of the government’s policies was that such policies turned kijichons places where women cannot normally live, as we can see when Hyun Jin Kong, another victim of Korean blood- related culture, runs away to America with Sookie’s daughter Myu Myu. (Chosum University)

Epidermal Mucus of Anabas testudineus as a Promising Source of Antibacterial and Anticancer Agents

Anabas testudineus is a sturdy freshwater fish that can live in a polluted environment due to the epidermal mucus (EM) that protects the fish from pathogens or germs. This study explored the functional properties of the EM as a potential antimicrobial and anticancer agent. Inactive Pseudomonas aeruginosa was introduced into fish tanks to stimulate the production of EM. This stimulus significantly increased EM production by more than 100% after 10 days of stimulation, indicating that EM production was influenced by environmental biotic stress. In vitro antibacterial activity tests showed that EM has significant antibacterial activity against Escherichia coli (12 ± 0.23 mm) and P. aeruginosa (10 ± 0.13 mm) at the tested concentration of 1000 μg/mL. Further characterisation against cells showed that EM has a cytotoxic effect against human breast cancer (MCF7) and human melanoma (A375.S2) producing an IC50 value of 4.97 ± 0.25 and 6.27 ± 0.17 mg/mL, respectively. In contrast, no cytotoxicity against normal fibroblast skin cells (HS27) was observed. In addition, apoptosis analysis showed that EM could cause DNA fragmentation of cancer cells, while no effect on normal cells was observed. These findings indicated that EM from A. testudineus could be further studied and explored as an anticancer agent.

Smart Automation Aquaponics Monitoring System

Modern agriculture, such as aquaponics, has become a well-known solution nowadays for farming, especially in Asia countries. It provides an alternative to support food demands and maintain environmental sustainability. However, it requires manpower and time to maintain and monitor the system. This research proposes a smart automation aquaponic monitoring system that helps users maintain and monitor the system through smartphone applications. The system uses DHT11 to record temperature and humidity, HC-SR04 for water level, and FC-28 to maintain soil moisture. The sensors are integrated with WeMos D1 Wi-Fi Uno based ESP8266 microcontroller to process the data. The data collected is stored in the cloud and retrieved via the Blynk application, which also performs as an actuator and allows users to control the parameters involved. The application helps to monitor the humidity, temperature, and water level in the fish tank and control the actuator for feeding fish. The system also sends a notification to the user for any activities performed, such as watering plants, feeding fish, and abnormality of temperature in the surroundings. The performance of the system was evaluated using regression modeling. The result indicates positive growth for both plants and fish during the monitoring duration, suggesting the proposed system's effectiveness. Overall, this solution helps to reduce manpower and operation costs as well as alternatives for food demand and stabilize environmental sustainability, especially in the urban residency.

Ultrasonic monitoring of early larval development of fish in tanks. Case study: Gilthead seabream (Sparus aurata)

Swimbladder inflation is a significant matter in intensive fish farming, since it is related to larval survival rate and the morphological quality of individuals. In this work, we propose a non-invasive acoustic technique using ultrasound to monitor the swimbladder development of gilthead seabream (Sparus aurata) in tanks. The fundamental hypothesis is that, due to the high acoustic contrast of gas, the swimbladder’s inflation process can be detected by measuring the larvae’s target strength during their early development. Backscatter numerical models using the finite element method, developed from biological measurement data, were applied to evaluate the feasibility of the proposed method. The acoustic measurements were obtained using an EK60 Simrad echosounder working at 200 kHz. The target strength values were evidenced with and without the presence of a developed swimbladder, showing a statistically significant relationship with the swimbladder’s standard length, area and the percentage of larvae with a swimbladder. The experiments were carried out in the Spanish Institute of Oceanography (IEO)’s marine aquaculture plant at Mazarrón (Murcia, Spain).

Evaluating Stress-Mediated Microbial Pathogenesis in Golden Shiners, Notemigonus crysoleucas.

Flavobacterium covae (columnaris) is a microbial pathogen of the Golden Shiner (Notemigonus crysoleucas), a principal bait species. We investigated the effects of density and water temperature on the survival of fish subjected to a columnaris challenge and whether flow cytometry (FCM) could be a fast and reliable method to distinguish and enumerate F. covae populations from water and fish in experimental tanks. Juvenile Golden Shiners averaging 2.62 (±0.78 S.D.) g (negative for F. covae) were used in simultaneous trials at 22°C and 28°C in two ultra-low flow-through systems: each consisting of four treatments and five replicates per treatment. Treatments were fish stocked at either 600 fish/m3 or 2,400 fish/m3 and either challenged with F. covae or not; survival was observed for 48 h after challenge. Samples of water and fish tissue were obtained for FCM enumerations and validation by qPCR. No significant differences in survival were recorded between density treatments; however, high temperature and columnaris challenge treatments showed significantly higher mortality. Bacterial enumeration (number/mL) by FCM highly correlated with bacterial counts r = 0.81 (p = 0.001) in the water samples. Higher water temperatures may have increased columnaris infections and mortality in Golden Shiners. Flow cytometry is a reliable method of enumerating F. covae from experimental tank water samples.

An Overview of Ammonia Poisoning in Aquariums

Ammonia poisoning is a common problem in fish tanks but is not a disease and is one of the deadliest causes of aquarium fish mortality. This happens more in newly launched aquariums. Ammonia poisoning can occur immediately or within a few days. Initially, fish may be seen breathing on the surface of the water to breathe. The worst factor in ammonia poisoning is that excess ammonia is not visible in water, although its effects are visible.

Dietary carbohydrate-to-protein ratio influences growth performance, hepatic health and dynamic of gut microbiota in atlantic salmon (Salmo salar)

Atlantic salmon (Salmo salar) fed a carbohydrate-rich diet exhibit suboptimal growth performance, along with other metabolic disturbances. It is well known that gut microbes play a pivotal role in influencing metabolism of the host, and these microbes can be modified by the diet. The main goal of the present study was to determine the effect of feeding graded levels of digestible carbohydrates to Atlantic salmon on the distal intestine digesta microbiota at 3 sampling times (i.e., weeks 4, 8 and 12), during a 12-week trial. A low carbohydrate-to-high protein diet (LC/HP, 0% wheat starch), a medium carbohydrate-to-medium protein diet (MC/MP, 15% wheat starch) or a high carbohydrate-to-low protein diet (HC/LP, 30% wheat starch) was fed to triplicate fish tanks (27 to 28 fish per tank). We performed an in-depth characterization of the distal intestine digesta microbiota. Further, growth parameters, liver histology and the expression of genes involved in hepatic neolipogenesis in fish were measured. Fish fed a HC/LP diet showed greater hepatosomatic and viscerosomatic indexes (P = 0.026 and P = 0.018, respectively), lower final weight (P = 0.005), weight gain (P = 0.003), feed efficiency (P = 0.033) and growth rate (P = 0.003) compared with fish fed the LC/HP diet. Further, feeding salmon a high digestible carbohydrate diet caused greater lipid vacuolization, steatosis index (P = 0.007) and expression of fatty acid synthase (fas) and delta-6 fatty acyl desaturase (d6fad) (P = 0.001 and P = 0.001, respectively) in the liver compared with fish fed the LC/HP diet. Although, the major impact of feeding a carbohydrate-rich diet to Atlantic salmon in beta diversity of distal intestine digesta microbiota was observed at week 4 (HC/LP vs MC/MP and HC/LP vs LC/HP; P = 0.007 and P = 0.008, respectively) and week 8 (HC/LP vs MC/MP; P = 0.04), no differences between experimental groups were detected after 12 weeks of feeding. Finally, at the end of the trial, there was a negative correlation between lactic acid bacteria (LAB) members, including Leuconostoc and Lactobacillus, with hepatic steatosis level, the hepatosomatic and viscerosomatic indexes as well as the expression of fas and d6fad. Weissella showed negative correlation with hepatic steatosis level and the hepatosomatic index. Finally, further research to explore the potential use of LAB as probiotics to improve liver health in carnivorous fish fed fatty liver-induced diet is warranted.

Carbon dynamics and energy recovery in a novel near-zero waste aquaponics system with onsite anaerobic treatment

Aquaponics is gaining renewed interest to enhance food security. This study aimed to investigate the performance of a novel off-grid aquaponics system with near-zero water and waste discharge, focusing on the carbon cycle and energy recovery that was achieved by the addition of onsite anaerobic treatment of the solid waste streams. Following a stabilization stage, the system was closely monitored for four months. Fish tank water was recirculated via solid and nitrification reactors, from which 66% was recycled to the fish tank directly and 34% indirectly through the hydroponically grown plants. Fish solid waste was anaerobically treated, energy was recovered, and the nutrient-rich supernatant was recycled to the plants to enhance production. Plant waste was also digested anaerobically for further recovery of energy and nutrients. Fish stocking density was 15.3 and over time reached approximately 40 kg/m3 where it was maintained. Feed (45% protein content) was applied daily at 2% of body weight. Typical fish performance was observed with a survival rate >97% and feed conversion ratio of 1.33. Lettuce production was up to 5.65 kg/m2, significantly higher than previous reports, largely because of high nutrients reuse efficiency from the anaerobic supernatant that contained 130 and 34 mg/L N and P, respectively. Of the feed carbon, 24.5% was taken up by fish biomass. Fish solid wastes contained 38.2% carbon, of which 91.9% was recovered as biogas (74.5% CH4). Biogas production was 0.84 m3/kg for fish sludge and 0.67 m3/kg for dry plant material. CO2 sequestration was 1.4 higher than the feed carbon, which reduced the system's carbon footprint by 64%. This study is the first to demonstrate highly efficient fish and plant production with near-zero water and waste discharge and with energy recovery that can potentially supply the system's energy demand.

The Amazing Diversity of Cichlid Fishes

Imagine swimming through warm, clear-blue water where, all around you, you see brightly colored fishes of all shapes and sizes. Does this sound like a tropical coral reef? Maybe so, but it could also be a tropical freshwater lake, with hundreds of different types of cichlid fishes. Cichlids live only in freshwater and are found in lots of different lakes and rivers across the world. Their bright colors and interesting behaviors mean that they are popular to keep as pets in fish tanks, but they also are incredibly interesting to scientists and are a valuable food source. Scientists study cichlids because they want to understand how different types of cichlids have evolved to suit their different environments. Cichlids are important for food in many countries, both through fishing of wild populations and fish farming (aquaculture), in specially built ponds or tanks.

Dietary treatment of Nile tilapia (Oreochromis niloticus) with aquatic fern (Azolla caroliniana) improves growth performance, immunological response, and disease resistance against Streptococcus agalactiae cultured in bio-floc system

The present study was performed to examine the effects of aquatic fern (Azolla caroliniana) (AQF) on growth performance, skin mucus and serum immunities, and disease resistance of Nile tilapia reared in a biofloc system. Three hundred Nile tilapia fingerlings (average 10.48 ± 0.56 g fish-1) were distributed into 15 glass tanks (150 liters tank−1) at a concentration of 20 fish tank−1. A completely randomized design was used in triplicates, where the control group was fed 0 g kg−1 AQF (AQF1), while AQF2, AQF3, AQF4, and AQF5 were fed 25, 50, 100, and 200 g kg−1 AQF, respectively. Growth and immunological specimens were collected every 4 weeks, while disease resistance was conducted after 8 weeks post-feeding. The results showed that dietary administration of AQF significantly promoted the growth rate and feed efficiency of Nile tilapia, with the maximum level noticed in fish fed 100 g kg−1 AQF. However, no significant differences were observed between the AQF1 and AQF5 diets. Similarly, incorporation of AQF resulted in significantly higher skin mucus and serum immunities than the control, except for AQF5. The highest values were observed in fish fed the AQF5 diet. The challenge test showed that in contrast to the control (26.67%), the AQF administrated diets led to significantly higher survivability by 60% (AQF2), 66.67% (AQF3), 83.33% (AQF4), and 53.33 for AQF5. The relative percent survival (RPS) was 45.45%, 54.55%, 77.27%, and 36.36% in AQF2, AQF3, AQF4, and AQF5, respectively. The highest RPS against S. agalactiae was noted in the AQF4 diet. In conclusion, dietary supplementation of 100 g kg−1 AQF can be potentially used as a growth promoter and immunostimulant in Nile tilapia aquaculture.