Aquaculture International

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  • Ruoming LiRuoming Li
  • Teng ChiTeng Chi
  • Qing XuQing Xu
  • [...]
  • Guiqin WangGuiqin Wang
Probiotics have been documented to promote growth, immunity, and disease resistance in farmed fish. In the present study, we aimed to evaluate single or conjoint effects of some lactic acid bacteria (LAB), namely, Lactococcus lactis, Lactobacillus rhamnosus, and Enterococcus faecalis on the growth performance, immune response, and disease resistance of Carassius auratus. Fish were fed a basal diet supplemented with L. lactis (group B), L. rhamnosus (group C), E. faecalis (group D), L. lactis + L. rhamnosus (group E), L. rhamnosus + E. faecalis (group F), L. lactis + E. faecalis (group G), and L. lactis + L. rhamnosus + E. faecalis (group H) at 5.0 × 10⁸ CFU/g diet for 34 days. After feeding, the final body weight (FBW), weight gain (WG), specific growth rate (SGR), and survival had significantly increased (p < 0.05) for group E. The results indicated that single or conjoint administration of LAB induced high levels of IgM, LZM, AKP, and SOD activity in serum, which may effectively induce humoral immunity, and group E induced even higher levels. At the same time, when compared to the basal diet (group A), the results of qPCR showed that probiotic administration significantly upregulated (p < 0.05) the expression of IL-10, IL-1β, TNF-α, and IFN-γ in the spleen, kidney, liver, and intestine of C. auratus. After challenge with the Aeromonas hydrophila, the survival rates in all probiotic-fed groups were significantly higher (p < 0.05) than those of group A, and the relative protection rates of groups B, C, D, E, F, G, and H were 27%, 30.7%, 40.94%, 42.32%, 39.38%, 33.61%, and 37.5%, respectively. Our data indicated that probiotics could promote growth, enhance immune indicators, and enhance immune capacity. In summary, combined administration of probiotics had a better effect on C. auratus. This experiment could provide a reference for the optimal combination of probiotic additives for aquatic animals.
 
Death of O. niloticus during the experimental period. 0 h: time of arrival of the transported fish to the laboratory. G1: farm water, G2: MS-222 only, G3: MS-222 + iodine, G4: iodine only. The initial number of fish in each group: 30. TNDF, total number of dead fish during 14 days
Cumulative mortality rate (CMR) of O. niloticus during the experimental period. G1: farm water, G2: MS-222 only, G3: MS-222 + iodine, G4: iodine only. The initial number of fish in each group: 30
Mortality rate (MR) % in different groups challenged with A. hydrophila
Fish transportation is a regular farming and experimental practice that mainly results in stress conditions that may extend to induce a high mortality rate. In the present experimental simulation, Oreochromis niloticus were transported for 2 h and maintained for another 6 h in transportation containers to assess the effect of tranquilization with tricaine methanesulfonate (MS-222) and/or the addition of iodine on mortality rate and restoring the normal physiological functions. Experimental fish were divided into four groups: group 1 (control) was transported in farm water without MS-222 or iodine, group (2) was transported in farm water supplemented with 40 mg/L of MS-222, fish in group (3) were transported in farm water supplemented with 40 mg/L of MS-222 + 10 ppm iodine, and fish in group (4) were transported in farm water containing 10 ppm iodine. Blood samples were collected for the determination of serum cortisol and glucose, while skin mucus was collected for assaying lysozyme, peroxidase and antibacterial activity; cumulative mortality rate; and food reflexes which were assessed at 0 h, 1 h, 6 h, 48 h, 7 days and 14 days post 2 h transportation. The results indicated that fish tranquilization with MS-222 and/or treatment with iodine mitigated the stress condition associated with transportation and accelerate restoration of the normal physiological and immunological status. So, it was recommended to use the MS-222 as a tranquillizer together with iodine as an antiseptic during transportation of O. niloticus.
 
Acrossocheilus fasciatus is an economically valuable freshwater fish species that inhabits streams. Female A. fasciatus grow faster and taste better than males, while male show dramatic color and mainly be considered ornamental fish. Numerous farms are trying to breeding an all-female or all-male pedigree. However, little research has been reported on sex determination and gonadal development in A. fasciatus. Genetic and genomic information on its reproduction is also lacking, greatly limiting its breeding and genetic manipulation. To define its genetic background and determine whether there are unique mechanisms in A. fasciatus gonadal development, we utilized transcriptome information from A. fasciatus to recognize genes possibly included in sex determination and gonadal development. Ten sex determining genes significantly up- or downregulated were filtered through the DEGs data: ATP-binding cassette sub-family E member 1 (abce1); nucleolar MIF4G domain-containing protein 1-like (nom1); protein kinase membrane associated tyrosine/threonine 1 (pkmyt1); prostacyclin receptor-like (ptgir); homo box protein six (six1); small nuclear ribonucleoprotein A-like (snpra); Wnt family member 4 (wnt4); double sex- and mab-3-related transcription factor 3a (dmrt3); E2-alpha-like (e2a); and winged helix/forkhead transcription factor L2 (foxl2). The expression patterns of these genes have been checked by way of qRT-PCR during different stages of gonad development. dmrt3 was significantly upregulated in males all through the gonad development stages and might play key positions in testis development. Foxl2 expression was not significantly higher in females, whereas nom1, abce1, and pkmyt1 were continuously highly expressed. Our results indicate that some of the crucial sex determination genes show unique expression patterns in A. fasciatus. These findings may enable the manipulation of sex determination genes and the cultivation of new varieties, as well as the exploration of evolutionary processes of fish sex determination mechanisms.
 
Black rockfish (Sebastes schlegelii) is a marine fish with high financial value; however, the frequent occurrence of bacterial diseases has caused a production decline and economic losses. This study found that hyperemia, hemorrhage, and ascites were common in S. schlegelii during the V. parahaemolyticus infection. Inflammation, degeneration, and necrosis in the liver could be observed. The epithelial mucosal integrity, the intestine epidermis thickness, the villus heights, and the number of mucous cells in the intestine were decreased after infection. Apparent differences in most of the hematological parameters between the two groups were observed, such as the corpuscular volume (CV) and NaCl concentrations of the beginning hemolysis were decreased remarkably (P < 0.01) after infecting with V. parahaemolyticus. However, the white blood cell count (WBC), lysozyme (LZM), malondialdehyde (MDA), K⁺, Cl⁻, and Ca²⁺ were increased significantly (P < 0.01) after infection. In addition, the mRNA expressions in four tissues (gills, liver, blood, spleen) of eleven immune-related genes were investigated. The results showed that C1r, C1s, and C1inh expression varied considerably among tissues. Caspase 10 expression was reduced in four tissues after infection, but MyD88, TNF receptor, TNF-α, BAFF, IL-1β, IL-8, and IL-10 showed increased expression profiles within 24 h after infection. In particular, IL-1β expression in the liver and spleen increased 123.67 and 104.94-fold at 6 hpi, respectively. Therefore, in addition to pathology, the hematological detection and gene expression profiles could be used in the evaluation of healthy status in fish, and this study provided a preliminary basis for the diagnosis of S. schlegelii infecting with V. parahaemolyticus.
 
WorldFish Silver Carp Genetic Improvement Program cohorts. Founders were sourced as adult fish from 17 Bangladeshi hatcheries that were assigned to genetic groups—Sagor-Mukteshary-Jashore-BRAC (SMJB); Joyda, Raipur, Akram-Puthia (AP), and Rajshahi-Parbatipur-Nimgachi (RPN). The number of full-sibling families are shown in boxes, and the number of parents used to generate families are shown adjacent to arrows
Genetic group means for each trait. Trait means for the genetic group with the greatest value are indicated. Difference between populations were not statistically significant for any trait, according to likelihood ratio tests
In 2017, the base population of a family-based silver carp (Hypophthalmichthys molitrix) genetic improvement program was spawned in Bangladesh. This program aims to improve the growth rate of silver carp under polyculture production systems, through direct selection on the primary trait of harvest-age weight. The objective of this study was to quantify genetic variation in, and genetic correlations between, harvest-age weight (assessed on 8012 fish from 184 families) and a set of secondary traits (assessed on 1603 fish from 175 families). Secondary traits examined included feeding and digestive system traits (i.e. gill raker sponginess and gut length as a ratio of standard length), a morphometric trait (i.e. extent of overlap of pectoral and pelvic fins) and health traits (i.e. presence of Lernaea and prevalence of red spots — sites of inflammation/haemorrhaging). Despite not being under direct selection, genetic change in secondary traits is possible across generations in closed genetic improvement populations as a result of a correlated response to selection for the primary trait (i.e. indirect selection), adaptation to culture conditions, inbreeding and/or genetic drift. It was found that the additive genetic variance within genetic groups was significantly different from zero for all but the studied health traits. Heritability estimates for harvest-age weight and pectoral/pelvic fin overlap were moderate (0.24 and 0.22, respectively) but were low for gill raker score and relative gut length (0.12 and 0.09, respectively). Genetic correlations between harvest-age weight and secondary traits were not significantly different from zero, indicating that selection for harvest-age weight will not result in a correlated response to selection in the studied secondary traits.
 
This study aimed to investigate the presence of Sarcotaces sp. in Epinephelus epilistictus (the dotted grouper) in Saudi Arabia. So, during our routine clinical examination of fish health conditions at Jubail province in the eastern region of Saudi Arabia (Arabian Gulf), nine grouper fish species were examined for Sarcotaces sp. (Copepoda: Phylichthyidae). Only the dotted grouper ( Epinephelus epilistictus ) harbored parasitic Sarcotaces spp. with an incidence of 9.06% of 1600 clinically examined fish samples. The collected Sarcotaces sp. was Sarcotaces arcticus ( S. arcticus ). The copepods were completely encapsulated cysts with a pyriform or pear-like shape, small to large, white-grayish, fluid-filled with thick black ink beneath the skin, or fully embedded in the muscular layer. The cysts present in the lateral aspect of trunk muscles, flank, caudal peduncle, near the anal opening, or pelvic and pectoral fin with an infestation rate (1–6 cysts) per fish. The cyst histopathology reveals the capsular layer of the cyst consisting of fibrous connective with pressure atrophy of the adjacent muscles associated with dilated blood vessels. The absence of infestation in other kinds of grouper fish species from the water of the Arabian Gulf in Jubail province may indicate parasitic host specificity and geographic locality distribution.
 
Cherax destructor, a native Australian freshwater crayfish, has been extensively studied for its aquaculture potential, but its growth and immune responses at different temperatures remain unclear. In this study, after 8 weeks of culture at 10 °C, 15 °C, 20 °C, 25 °C, and 30 °C, the effects of temperature on growth parameters, hepatopancreas histology, antioxidant, and immune indexes in C. destructor were evaluated. The results revealed that the specific growth rate was decreased in the 10 °C and 15 °C groups. Compared to the 20 °C and 25 °C groups, the activities of the hepatopancreas damage indicators, aspartate aminotransferase, and alanine aminotransferase (ALT) were both increased in the 30 °C group, and the ALT activity was increased in the 10 °C and 15 °C groups. The activity of antioxidant and immune enzymes showed a decreasing trend, while their corresponding gene expression first increased and then decreased as the temperature decreased. In addition, malondialdehyde content was increased in the 30 °C group compared to the 25 °C group. These results indicated that the optimal growth temperature of C. destructor was 20–25 °C. High temperature may induce oxidative stress which in turn damages the hepatopancreas function of crayfish, thereby reducing antioxidant and immune ability. Low temperature may inhibit the development of the hepatopancreas, thereby affecting its function, resulting in decreased immune defenses and ultimately growth inhibition.
 
Effective utilization of service vessels in sea-based fish farming requires that the vessels are suited to the operating environments at the fish farms. This paper presents a methodology for assessing service vessel fleet performance when serving a network of farms with different metocean conditions. Fleet performance is defined as the ability to perform operations requested by the fish farms, in due time. An optimization for simulation approach is employed, implementing a routing and scheduling heuristic developed for aquaculture service vessels. A case study was performed assessing the performance of two different fleets serving a set of 21 fish farms. The variation in local metocean conditions between the farms, and how weather changes in time, challenges the operability of the aquaculture infrastructure and the effective routing and scheduling of the vessels. Hence, the results show that proper fleet composition in this context improves fleet performance. Fleet performance is substantially higher when fleet composition, routing, and scheduling is based on the specific weather conditions.
 
Dynamics of total settleable solids (TSS, ml l⁻¹) in culture water during the rearing of L. vannamei in a biofloc-based system. Shrimp were fed a practical feed (100:0) or fermented grain pellets (0:100) alone and a combination of both at different percentages (50:50, 75:25, and 25:75). Different letters indicate statistically significant difference according to the Tukey’s HSD test at α = 0.05. Each data point represents the mean of five rearing tanks
Apparent shrimp feed intake (%)fed under different proportions of feed to fermented grain pellets in feeding trays. Asterisks indicate statistically significant differences according to the Student’s t-test (P < 0.05). Each column represents the mean (± standard error) of 50 observations of feed intake (5 tanks × 5 days of observations × 2 feedings per day)
Digestive enzyme activity of protease, lipase, and amylase in the hepatopancreas of L. vannamei fed a practical feed (100:0) or fermented grain pellets (0:100) alone and a combination of both at different proportions (50:50, 75:25, and 25:75). Different letters indicate a statistically significant differences according to the Tukey’s HSD test at α = 0.05
This study investigated the dietary contribution of fermented grain pellets (FGP) to the growth of juvenile Litopenaeus vannamei raised in a biofloc-based system. Grain pellets made of agricultural plant by-products were fermented with distilled water containing dehydrated live probiotic yeast, Saccharomyces cerevisiae. Shrimp were fed a feed with 396.8 g kg⁻¹ crude protein (CP) under the following proportions: 100:0 (percentage of feed and FGP to the total daily ration, respectively), 75:25, 50:50, 25:75, and 0:100. Juvenile shrimp of 1.15 ± 0.12 g were stocked under 133 animals m⁻² and reared for 77 days in thirty-five 1-m³ outdoor tanks. Final shrimp survival reached 89.3 ± 5.7% and was unaffected by dietary treatment. Shrimp body weight decreased significantly from 12.68 ± 1.48 (100:0) and 11.71 ± 0.67 g (75:25) to a low of 5.23 ± 0.40 g (0:100). No differences were found in weekly shrimp growth between shrimp fed under 100:0 (1.06 ± 0.14 g) and 75:25 (0.97 ± 0.06 g). Feed replacement at 25% caused no loss in yield (1,290 ± 87 g m⁻²) compared to no feed replacement at all (1,365 ± 148 g m⁻²). The 75:25 proportion of feed to FGP was able to partially spare feed inputs leading to 0.08 USD kg⁻¹ savings in feeding costs. Results indicated that a feed replacement of 25% compensated by an equivalent amount of FGP as part of the daily ration led to no detriment in shrimp growth performance in a biofloc-based system.
 
The brown meagre, Sciaena umbra, is a Sciaenid fish of patrimonial and fisheries interest in the Mediterranean and North East Atlantic. Sciaenids species are new to aquaculture and present high potential for aquaculture, demonstrating fast growth and an efficient feed conversion. Hence, this study documents early ontogeny from fertilized eggs to 40 days post-hatching (DPH) in order to assess the culture potential of brown meagre. Eggs were collected from spontaneous spawning of captive broodstocks and incubated at 18.5 ± 0.5 °C and 38 ppt of salinity for about 42 h post fertilization (hpf). Fertilized eggs were pelagic, transparent, and spherical, measuring 1.254 ± 0.026 mm. The eggs were characterized by a narrow perivitelline space, smooth and thin chorion and carried a non-segmented yolk with a single lipid globule. Embryonic development consisted of four consecutive periods: the cleavage period (0–2:38 hpf), the blastula period (2:38–3:52 hpf), the gastrulation period (3:52–17:20 hpf), and the segmentation period (17:20–41:20 hpf). Thereafter, the eggs hatched (41:20–43:20 hpf) into yolk sac larvae, measuring from 3.139 ± 0.132 mm (total length, TL). Larval development of brown meagre was divided into four periods: yolk sac until complete absorption (0–3 DPH, TL3DPH = 3.649 ± 0.119 mm), pre-flexion (4–14 DPH, TL14DPH = 4.996 ± 0.300 mm), flexion (15–17 DPH, TL17DPH = 5.387 ± 0.381 mm), and post-flexion (18–35 DPH, TL35DPH = 16.450 ± 1.012 mm). After 35 DPH, the larval metamorphosis was complete as larvae were transformed into juveniles. Our results emphasize the high potential of brown meagre for aquaculture either in restocking programs or mariculture projects.
 
Spatial distribution of fish school is a critical indicator that exhibits behaviour changes such as stress, feeding, and other special behaviours in intensive aquaculture. However, it is challenging for spatial distribution quantification due to the large-scale variations, the similarity between different categories, and occlusion, resulting in false or missed detection. To address these problems, we propose a method, named SE_YOLOV5_DGhost, to achieve superior performance on fish detection and quantify the spatial distribution of fish school. Specifically, we improve the backbone structure and design a lightweight bottleneck of the neck, enhancing the feature extraction ability of the network. Comprehensive experimental results demonstrate that the proposed method can achieve higher detection performance with lower computational cost (e.g. 4.63 M Params, 5.92G FLOPs, and 9.6 M model size) on underwater fish dataset compared with YOLOV5s (e.g. 93.2% mean average precision). Indeed, our proposed method can be effectively applied to quantify the spatial distribution of fish school in intensive aquaculture.
 
Variation of major ions Ca²⁺, Mg²⁺, and K+ during a Penaeus vannamei grow out using a synbiotic system with different ionic composition in low-salinity water
The aim of the present study was to evaluate the efect of diferent ionic compositions in low-salinity water on the growth and proximate composition of Penaeus vannamei reared in the synbiotic system. A 56-day trial (300 shrimp m-3) was conducted in 60-L units with a completely randomized experimental design involving three treatments (each with three repetitions): Control — seawater diluted to salinity ~2.7 g L−1; T1 — seawater diluted to salinity~2.7 g L−1 with Ca:Mg:K ratio adjustment (1:3:1); and T2 — seawater diluted to salinity ~2.7 g L−1 with Mg2+ adjustment. The shrimp survival rate varied from 53.7 to 81.48%, shrimp (initial weight=0.42±0.1 g) reached a fnal weight ranging from 3.70±0.07 to 4.72±0.09 g and an average yield ranging from 0.61±0.14 to 1.22±0.06 kg m−3, with signifcant diferences among the treatments. The best overall growth was found in the T2 treatment. The T1 treatment had the signifcantly lowest results, which may have been due to reduction in the Na:K ratio (Control=27.39; T2=29.03; T1=19.55) due to K+ corrections. Low concentrations of nitrogen compounds were found due to the synbiotic fertilization and substrate composed of Anomalocardia brasiliana shells that work as substrate for bacteria and a source of calcium carbonate. No signifcant diferences in proximate composition were found among the treatments. A diference in the ash content of the microbial focs was found among treatments, with a higher percentage in the T1 treatment compared to the Control and T2 treatments. The present results indicate that total alkalinity close to 90 mg CaCO3 L−1 and the Na:K ratio close to 28:1 produced conditions that did not limit the growth of P. vannamei in low-salinity water with a synbiotic system.
 
Given the growth and change in Canadian salmon aquaculture in the last several years, there is a need to understand consumer habits on salmon consumption and knowledge and perception of salmon production in Canada. The objective of this study is to better understand current salmon consumption trends and consumer views and opinions on salmon farming production in Canada. Canadian participants completed a survey separated into two different sections: (1) consumption habits and preferences and (2) knowledge and perception of production methods. Quantitative descriptive data was collected through a cross-sectional consumer survey in Canada, which included 30 questions. Total sample size was 10,009 respondents (48% female, 52% male). Participants were randomly selected from the representative of the Caddle omni access panel. A total of 79% of Canadians do eat salmon, of which 10% eat salmon weekly. Baby Boomers (born in 1946–1964) have the highest consumption rate at 84%, while Millennials (born in 1981–1996) have the lowest, at 72%. A total of 49% of Canadians prefer wild salmon but 42% have no preference. A total of 62% want to eat a product produced in a natural habitat. Of those surveyed, 37% believe wild salmon presents a lower risk of contamination, and 29% believe wild salmon to be more nutritious. A total of 21% of Canadians prefer to eat farmed salmon that has been raised on a land-based farm; however, a total of 39% prefer an ocean farm as a method of production. While 38% of Canadians prefer Atlantic salmon, 33% prefer Pacific salmon (Sockeye, Pink, Chinook, and Chum species) and 29% do not have a preference. Only 26% of Canadians were aware that organic salmon existed. A total of 55% of Canadians would be more inclined to buy farmed salmon if it were fed a diet that is environmentally sustainable and nutritious. A total of 54% believe that aquaculture is a sustainable way to harvest salmon in Canada. Canadians appear to support the sustainable nature of ocean farm production. Nonetheless, our results suggest that 50% of respondents appear to misunderstand what land-based and ocean farm means. Overall, Canadians enjoy salmon, but results indicate consumers are misinformed about method of production and species type indicating a need for improved information accessibility to the public on salmon production and consumption.
 
Biofloc technology (BFT) has achieved sustainable aquaculture production, intensifica-tion, and profitable food-producing activity. The colonization process in floating substrates is elemental for BFT proliferation and biomass increase. Organic substrates are feasible nucleators for the nutrient richness required by heterotrophic bacteria. This study evaluated the effect of vegetal-derived substrates on biofloc bacterial diversity generated in a 36-day hyper-intensive white shrimp (Litopenaeus vannamei) culture. The treatments were established according to the presence of vegetal-derived substrates for biofloc production, including wheat bran, amaranth seeds, oat bran, and a control (without substrate). Shrimp cultured in treatments using floating substrates registered better productive responses. Water quality results indicated that bioflocs were at the beginning of the nitrification phase, suggesting that bioflocs were entering the mature stage. Similar taxonomic profile structures throughout treatments were also observed and at least 26 bacterial phyla were detected in each treatment but only nine represented ~ 98% of the relative abundance in each treatment: Proteobacteria (35.9-49.5-1.2%). Beta diversity analyses also revealed no significant differences between treatments. Permutational multivariate analysis of variance showed no statistical differences either by estimating Bray-Curtis or Weighted Unifrac distances. In conclusion, agricultural-derived floating substrates used at the beginning of culture to boost biofloc production do not modify the bacterial taxonomic profile, which seems to be mainly driven by the prevailing environmental conditions established for biofloc formation.
 
Map of Lake Donuzlav and the sampling site location
Distribution of the gonadal maturation stages in M. galloprovincialis cultivated on the mollusk farm in 2019–2020: (a) males, (b) females
The mussel M. galloprovincialis is a bivalve that is extensively cultivated in coastal waters of the Temperate Northern Atlantic, South Africa, and China. In the present study, the variations of allometric indices, sex ratio, and occurrences of the black and brown shell coloration and gonadal ripening stages in this bivalve were studied over a 20-month period in a mussel population from a mollusk farm in the northwestern part of the Black Sea. The allometric indices were applied as the measures of the overall environmental status for the mussel development, with the elongation index (H/L) being the most sensitive one. The obtained allometric index values (H/L = 0.52 ± 0.02, D/L = 0.38 ± 0.01) were comparable with those observed in clean waters of the Black Sea. The noted biases in the mussel sex ratio towards males (♀:♂ = 1:2.8) on farm collectors and towards females (♀:♂ = 1.6:1) on the seafloor under the farm were attributed to changing environmental conditions. The mean ratios of the number of mussels with brown and black shell coloration varied from 1:3.2 on the collectors to 1:1.8 on the seafloor. The mass spawning was found to start earlier in mussel males than in females. The biological characteristics in question are applicable for assessing the impact on mussel settlements and for long-term monitoring of marine environment in other water bodies of the World Ocean.
 
Concentration of 20-hydroxyecdysone in different parts of Diplazium esculentum (Mean ± SD)
In aquaculture, high mortality in crustacean larvae during the moulting process restricts the larviculture's productivity. This study aimed to determine the bioactive components in the methanolic extract of fiddlehead ferns, Diplazium esculentum, and their effects on the growth of Microbrachium rosenbergii postlarvae (PL). Hormonal analysis revealed a high level of 20-hydroxyecdysteroid (20E) hormone in both leaves and shoot parts (4733 pg/ ml) with the presence of phenols, tannins, saponins, flavonoids, terpenoids, alkaloids, and steroids during the phytochemical screening. GC-MS analysis discovered the presence of thirty-two bioactive compounds, including 1-(2,6-dichlorobenzoyl)-2,5-dimethylpyr-role, decyl sulfide, beta-amyrin, and cyclotetrasiloxane, octamethyl-with the peak area of 12.60%, 10.81%, 10.46%, and 8.48%, respectively. During a pilot study, prawn PL were fed diets containing D. esculentum extracts, namely diet 1-diet 5, with concentrations of 0.5, 1.0, 2.0, 4.0, and 10.0 gkg −1 , respectively. Results showed high survival in PL fed with diet 4 and diet 5 (75.56% and 77.22%, respectively; p = 0.049). Next, a 60-day feeding trial was conducted to determine the moulting and growth performance of PL fed with 0 gkg −1 (control), 4.0 gkg −1 (diet 4), and 10.0 gkg −1 (diet 5) fern extracts. Results showed that prawns fed with diet 5 significantly showed the highest moulting frequency (112 ± 1.32 moults) and moulting rate (2.04 ± 0.02 moults per prawn). The findings demonstrated that a higher concentration of 20E with the highest inclusion of D. esculentum in diets could have enhanced the moulting performance in M. rosenbergii. We suggest an experiment on nutrient-dose response to determining the optimum level for growth performance in M. rosenbergii.
 
A 61-day growth experiment was carried out to evaluate the potential of a poultry-based protein (PBP) comprising of feather meal (FeM) and poultry meat and bone meal (PMBM), as a fishmeal (FM) substitute in diets of juvenile pikeperch (Sander lucioperca, L.). Pikeperch (initial body weight 113.12 g) were randomly distributed in groups of 250 fish in twelve 1.8 m3 circular recirculating aquaculture system (RAS) tanks, and fed four isonitrogenous (52% crude protein), isolipidic (17% crude lipid), and isocaloric (21.80 KJ/g energy) experimental diets. The feeds contained FM as the primary protein source (PBP0) or PBP replacing 20 (PBP20), 40 (PBP40), or 60% (PBP60) of the FM. Based on appetite and calculated uneaten feed, the feeding rate was initially set at 1.5% and subsequently reduced to 1% of the total tank biomass towards the end of the study. At the end of the experiment, the average feed intake ranged from 1.93 to 2.00 g/fish/day (p > 0.05). No adverse effects on growth and feed efficiency were observed in fish fed diets PBP0, PBP20, and PBP40. Particularly, the final body weight (FBW) (248.73, 240.11 g), feed conversion ratio (FCR) (0.86, 0.91), specific growth rate (SGR) (1.29, 1.35%/day), and protein efficiency ratio (PER) (2.20, 2.12) of fish fed PBP20 and PBP40 were not significantly different from the control PBP0 whose values ranged from 248.11 g, 0.89, 1.27%/day, and 2.18, respectively (p > 0.05). In all treatments, the condition factor (k) (1.31 to 1.33), hepatosomatic index (HSI) (2.35 to 2.70%), visceral somatic index (VSI) (6.87 to 7.19%), and whole-body composition of crude protein (57.77–58.28%) and crude lipid (23.85–26.85%) were not significantly influenced by the dietary PBP inclusion level (p > 0.05). However, whole-body ash content was significantly higher in PBP60 (14.66%) compared to the other treatments (12.57–14.43%) (p < 0.05). Based on the results from this study, up to 40% of FM can be replaced by PBP in diets for pikeperch juveniles without compromising growth performance and feed utilization.
 
Locations of the study area in Bangladesh map
Coastal shrimp farming calendar in Bangladesh. Legend: J to D—each month of the year is represented with a capital letter.
Source—Alam and Phillips (2004)
Quality attributes evaluated before harvesting by locations
Duration of harvested shrimp in ice by locations
Actions taken by farmers to quality concerns
This study used a random selection of 150 extensive shrimp farms in three areas in Bangladesh (Paikgacha, Dacope, and Chokoria) and questionnaires to examine the quality, hygiene, and sanitation practices that farmers used to satisfy national and international concerns. The majority (95.67%) of farmers in all three sites did not examine the quality of the hatchery-bred post larvae (PL) and felt that the hatchery used chemicals or antibiotics in producing PL and supplied under-aged PL (below PL 15 ), resulting in significant mortality when released onto the farms. The majority of farmers (83.3%) performed a visual inspection, examining shrimp size, weight, and disease symptoms before harvesting. Farmers in Chokoria were better aware of the need of inspecting quality features (growth, disease, weight, and shell) before harvesting than farmers in Dacope and Paikgacha. Farmers frequently neglected the icing of caught shrimp at the request of the buyer. To reduce losses, they took action when collected shrimp exhibited indicators of low quality, such as the presence of spots (43.3%), fragile shells (37.3%), and accidental debris (88.7%). Shrimp producers also enhanced their quality standards by using 100% plastic crates to transport shrimp and by improving working surfaces (92%) to wash, sort, and sell the collected shrimp, and building sanitary restrooms (100%) at a safe distance from the farms. Farmers believed that new laws had forced them to enhance safety, hygiene, and sanitation standards in order to decrease the poor quality image of Bangladesh shrimp held by international buyers, despite higher operating expenses and lower profitability.
 
Boxplots represent water quality parameters during the 8-week experiment: pH (a), DO (b), conductivity (c), turbidity (d), total alkalinity (e), hardness (f), TAN (g), nitrite (h), and nitrate (i). The fish were reared in various concentrations of T. catappa leaf extract, and measurements were taken two times a week. DO, dissolved oxygen; NTU, nephelometric turbidity units; TAN, total ammonia nitrogen
Characteristics (a), frequency (b), and area (c) of bubble nest formation by male Siamese fighting fish reared in various concentrations of T. catappa leaf extract. The data on frequency and area were recorded from all fish three times weekly from week 6 to 8. Differences between means were tested with Duncan’s multiple range test. Different superscripts indicate a significant difference (P < 0.05) between treatments
Specific activities of digestive enzymes were analyzed in male Siamese fighting fish reared in various concentrations of T. catappa leaf extract: pepsin (a), trypsin (b), chymotrypsin (c), lipase (d), amylase (e), and amylase to trypsin ratio (f). The observed parameters were recorded at the end of the 8-week experiment. Data are expressed as tank means ± SEM (n = 5 per treatment). Differences between means were tested with Duncan’s multiple range test. Different superscripts indicate a significant difference (P < 0.05) between treatments
Breeders and keepers of Siamese fighting fish (Betta splendens) often add Indian almond (Terminalia catappa) leaf extract to the water in the aquarium, but there is little information available about the effects of extract concentration on water quality and fish performance. In the current study, the effects of T. catappa extract on water quality, growth performance, feed utilization, skin coloration, bubble nest formation, digestive enzyme activity, muscle quality, whole-body composition, and hematological parameters of B. splendens were investigated. Seventy-five juvenile male fish (2-month-old, 0.80 − 0.95 g initial weight) were individually reared in 350-mL cylindrical plastic containers (8.3 cm diameter × 12.5 cm height). The fish were reared for 8 weeks in four concentrations of T. catappa leaf extract (0.125, 0.25, 0.5, and 1 g L⁻¹) and a control group was reared in water without the extract. The fish received an excess of a commercial floating feed (39.4% crude protein) for fighting fish twice daily (08.00 and 17.00 h). A leaf extract concentration of 0.25 g L⁻¹ showed no significant effect on growth (specific growth rate = 1.62% body weight day⁻¹), feed utilization (feed conversion ratio = 1.21 g feed g gain⁻¹), viscerosomatic index, muscle quality, whole-body composition, and hematological parameters of reared fish (P > 0.05), but did show effects on some of the other metrics that were monitored. Water quality significantly improved during the experiment (P < 0.05). Increased skin lightness (L*) was observed in all experimental groups, but only fish reared in 0.125 g L⁻¹ leaf extract increased skin redness/greenness (a*), hue (h*), and chroma (C*) (P < 0.05). Relative to the control, increments in bubble nest formation frequency (1.70-fold on average) and bubble nest size (1.52-fold on average) were correlated with the concentration of T. catappa leaf extract (P < 0.05). Specific activities of protein- and lipid-digesting enzymes were not negatively affected but some modulations were observed in treatments containing leaf extract at 0.125, 0.25, and 1 g L⁻¹. Fish reared in the 0.25 g L⁻¹ treatment exhibited a sparing effect of carbohydrate utilization indicated by decreased amylase specific activity, increased lipase specific activity, and stable amylase/trypsin ratios. The results suggest that 0.25 g L⁻¹ of T. catappa leaf extract is a suitable concentration of the additive during the growing phase of male Siamese fighting fish.
 
The dietary impacts of turmeric, curcumin, and nanomicelle curcumin on the digestive enzyme activities, intestinal histology, and gut microbiota of the Pacific white shrimp, Litopenaeus vannamei, were assessed. The shrimps (2.96 ± 0.10 g) were fed with different dosages (g kg−1 diet) of turmeric (TUR 2.5, TUR 5, and TUR 10), curcumin (CUR 0.075, CUR 0.150, and CUR 0.300), nanomicelle curcumin (NMC 0.075, NMC 0.150, and NMC 0.300) and a control diet with no feed additives. Experimental treatments improved the intestinal amylase, protease, and lipase enzyme activities compared with the control group. The intestine enzymes recorded the highest activities in shrimp groups fed with NMC 0.150 (P < 0.05). TUR, CUR, and NMC treatments also increased the intestinal muscle thickness, villus height, and villus width in comparison to the control group. The intestine histomorphological indices were the highest in feeding with NMC 0.150 among all the treatments (P < 0.05). The study of the intestinal microbiota indicated that the total bacterial counts (TBC) and total Vibrio sp. counts decreased significantly when the shrimps were fed with experimental feed additives. Of interest, NMC treatments showed lower TBC and Vibrio sp. counts compared with CUR and TUR treatments (P < 0.05). TBC and total Vibrio sp. counts of the intestine were the highest in the control group (P < 0.05). To conclude, the application of nanomicellar carriers was proven promising as nanomicelle curcumin promoted the activities of digestive enzymes, gut microbiota, and intestinal health of L. vannamei through more efficient delivery of dietary immunostimulants.
 
Agarose gel electrophoresis of the PCR product (127 bp) of 16 s RNA gene for DNA extracted from 13 isolates of A. hydrophila (Lanes 2–14). Lane 1: 100 bp DNA ladder (SinaClon Biosciences, Iran). lane 15: positive control (ATCC = 7966); lane 16: negative control
Agarose gel electrophoresis of PCR reaction for aopB (A; 1044 bp) and ascV (B; 2143 bp) gene products for DNA samples of A. hydrophila isolates. M: molecular size marker (100–1500 bp), and L: molecular size marker (250 bp-10Kbp). Lane 1, 2, 3, 5, 6 and 7: isolated A. hydrophila. lane 4 and 8: positive control (ATCC no. = 7966)
Expression of aopB gene in A. hydrophila after 6-, 12-, and 24-h exposure with 1000 and 1800 mg ml⁻¹ PCA
Expression of ascV gene in A. hydrophila after 6-, 12-, and 24-h exposure with 1000 and 1800 mg ml⁻¹ PCA
Cumulative mortality percentage in experimental groups treated with PCA and oxytetracycline after challenged with virulence A. hydrophila
In this study, the antibacterial effects of para-coumaric acid (PCA), as an intermediate product in the phenylpropanoid biosynthesis pathway, on the virulence of Aeromonas hydrophila in both in vivo and in vitro conditions were assayed. First, the minimum inhibitory concentration (MIC) of PCA against A. hydrophila was determined. The existence of ascV and aopB virulence genes as essential components of the Type III secretion system (T3SS) of A. hydrophila was determined using RT-PCR analysis. Then, the effect of sub-MIC concentrations of PCA on the expression of ascV and aopB genes of bacteria was investigated using qRT-PCR. In the in vivo phase of the study, 135 juvenile common carp (weighing 30.2 ± 4.53 g) were equally divided into three groups in triplicates. Group 1 was fed with un-supplemented food, whereas groups 2 and 3 were fed with food supplemented with PCA or oxytetracycline (OTC), respectively, for 5 days. Following that, all groups were challenged with A. hydrophila, and mortality rates, the presence of A. hydrophila in surviving fish, and the expression of the ascV and aopB genes in the fish head kidney were assessed. Our results revealed that the expression of ascV and aopB genes was significantly suppressed after exposure to sub-MICs of PCA compared to control in both in vivo and in vitro assays (p < 0.05). Although the PCA-treated group showed higher mortality (= 36.7%) compared to the OTC group following bacterial challenge (= 23.3%), the expression of ascV and aopB genes in isolated bacteria in the PCA group was significantly lower than that in the OTC and control groups (p < 0.05). This is the first report of the in vitro and in vivo effects of PCA on decreasing the virulence properties of A. hydrophila in fish. It can be concluded that PCA has an inhibitory effect on the virulence and pathogenicity of A. hydrophila and may be effective in the control of Aeromonas infections in fish farms.
 
Aquaculture wastewater is suitable for algal growth especially due to its ammonium and nitrate content. Therefore, the wastewater can be utilized after a few amendments for algal biomass production for the recovery of valuable pigments. In the present study, aquaculture wastewater discharged from the Pangasius culture system was utilized for the production of a commercially valuable cyanobacterium Spirulina (Arthrospira) platensis with an aim to extract economically important pigments (phycocyanin and carotenoids). The aquaculture wastewater was amended with nutrients and used as a culture medium for S. platensis. The removal of nutrients from the effluent-based medium during the culture period was also monitored. A significant increase in growth rate (0.21 day⁻¹), biomass productivity (23.65 mg g⁻¹ day⁻¹), and the lowest doubling time (3.37 days) was noticed in decontaminated and amended aquaculture wastewater. The biomass produced in the wastewater showed phycocyanin content (132.45 mg g⁻¹ DW), total carotenoids (1.26 mg g⁻¹ DW), and protein (630 mg g⁻¹ DW). S. platensis in aquaculture wastewater showed nutrient removal up to 97.34% NH⁺4-N, 71.93% NO⁻3-N, 95.90% NO⁻2-N, and 93.39% PO4³⁻-P. The present report provides a piece of convincing evidence that S. platensis is a suitable candidate species for aquaculture wastewater utilization for cost-effective biomass production and improvement in the quality of wastewater through phycoremediation. Graphical abstract
 
Superoxide dismutase activity (U/mg protein) in liver and gill tissue of striped catfish fingerlings reared in different experimental units groups at the end of the 90 days experiment. The bars with the same superscript didn’t differ significantly (p > 0.05)
Catalase activity (U/mg protein) in liver and gill tissue of striped catfish fingerlings reared in different experimental units at the end of the 90 days experiment. The bars with the same superscript didn’t differ significantly (p > 0.05)
A study was conducted to investigate the effects of different stocking densities on growth, haematological, non-specific immune, and antioxidant defence parameters of striped catfish (Pangasianodon hypophthalmus) fingerlings reared in a finger millet-based biofloc system. Striped catfish fingerlings with a mean initial weight of 7.34 ± 0.06 g were randomly stocked in triplicate at six different treatment groups, which included 150/m3 (T1), 180/m3 (T2), 210/m3 (T3), 240/m3 (T4), and 270/m3 (T5) in biofloc-based units, and 150/m3 (C) with clear water in plastic crates (capacity 160 L) and reared for 90 days. Finger millet flour was used as an organic carbon source with a 15:1 C:N ratio. After 90 days of rearing, significantly (p < 0.05) higher, percentage weight gain (298.21 ± 9.92%) and daily growth index (0.24 ± 0.01) were obtained in T1 (150/m3) and lower values were recorded in T5 (270/m3). The antioxidant defence response, SOD, and CAT activity of liver and gill tissues were significantly (p < 0.05) lower in the T5 (270/m3) experimental unit and higher in the T1 (150/m3) experimental unit. Blood indices, haemoglobin, total erythrocyte, leucocyte count, packed cell volume, and mean corpuscular volume improved significantly (p < 0.05) in BFT units with stocking densities (150, 180, and 210/m3) compared to other experimental units. Stress enzyme responses, serum glucose (74.88 ± 4.48 and 77.15 ± 4.67 mg/dl), and serum cortisol (59.64 ± 4.62 and 60.65 ± 3.11 ng/ml) values were significantly (p < 0.05) reduced in BFT units (150, 180/m3) when compared to other experimental units. Non-specific immunity responses such as nitro blue tetrazolium activity (0.41 ± 0.02 OD at 540 nm), serum myeloperoxidase (1.08 ± 0.05 OD at 450 nm), and serum lysozyme activity (51.40 ± 2.02 U/ml) were significantly (p < 0.05) reduced in T5 (270/m3). From the results of the present study, it may be concluded that a stocking density of 240/m3 (T4) is ideal for overall individual growth, better immune, and stress responses of striped catfish culture in BFT system.
 
Complex coastal currents control early-stage larval dispersal from intertidal populations, and late-stage settlement patterns, but are often poorly resolved in larval dispersal models. Generally, there is high uncertainty in the timing of larval spawning, which markedly affects larval dispersal. In this study, we describe the physical parameters that induce spawning events in the blue mussel, Mytilus edulis, using a variation of the Condition Index (which relates the mass of meat to the mass of the shell) as a proxy. We developed a high-resolution Eulerian coastal hydrodynamic model, coupled with a Lagrangian particle tracking model, to quantify the potential dispersal of early-stage mussel larvae based on differing spawning dates obtained from field data. Our results showed that (1) the timings of larval spawning cannot be explained solely by ‘thermal shocks’ in the sea or air temperatures (i.e. fluctuations in temperature causing stress); (2) larger spawning events generally occurred during neap tides; (3) the simulated larval dispersal was largely but not always predicted by averaged current pathways (calculated over two weeks period); and (4) simulated self-recruitment was low at sites associated with strong tidal currents. These results have important implications for shellfisheries stock management and sustainability. Specific to this study, simulated mussels from shellfishery beds off North Wales dispersed more than 25 km in one week and so could feasibly contribute to the wider population throughout the northern part of the Irish Sea.
 
Theoretical representation of an IMTA assemblage, with triangles representing the different trophic compartments and arrows representing the different flows (blue for inorganic, black for feed, brown for organic)—illustrations from lapecheenligne.com, ©N.Neaud-Masson, shutterstock.com and Manuel d’actinologie ou de zoophytologie Paris; F.G. Levrault, 1834–1836
Experimental land-based IMTA (Ifremer, Palavas) with three compartments: (A) fish tanks operating with water recirculation; (B) outdoor microalgal raceways receiving fish effluent from A; (C) oyster ponds receiving microalgae from lagoons in B. Total surface area = 150 m.²
Temporal Chla concentrations (in mg L.⁻¹) during the experiment in the three IMTA-microalgae replicates: L1, L2 and L3
Pseudo-nitzschia (A and B) and Cylindrotheca closterium (C) identified in the three IMTA-microalgae replicates (photos
© Elise Caillard)
Inspired by agroecology, ecological aquaculture proposes an alternative model that uses ecology as a paradigm to develop innovative, more eco-friendly aquaculture with environmental, economic and social benefits. Integrated multi-trophic aquaculture (IMTA) is one application of this principle. Inspired by the natural trophic chain, it associates primary producers with primary or secondary consumers, providing a new source of biomass without requiring supplementary feed by recycling inorganic and organic wastes. Of these systems, land-based IMTA demonstrate several advantages, especially easier control of nutrient flows, contaminants and/or predators. This study focused on a land-based marine IMTA, combining a recirculating aquaculture system for fish consecutively with a natural marine polyculture of microalgae and oyster cultivation. The objective was to assess the ability of the microalgal polyculture both to bioremediate fish nutrients and to sustain oyster growth. For the first time in a Mediterranean climate, we confirmed the feasibility of developing a microalgae community of interest for oysters maintained by fish effluent. Despite strong variability in microalgae production, this IMTA system resulted in significant oyster growth over the experimental period of 1 month, with growth results of the same order of magnitude as natural juvenile growth. In the conditions tested, this IMTA with reduced human intervention allowed a gain in recoverable biomass of 3.7 g of oyster produced per killogramme of fish feed distributed. By transforming waste into additional biomass, IMTA offer a more promising, ecological avenue for aquaculture, based on a circular economy, which may in turn increase the social acceptability of fish farming.
 
Water quality parameters (mean ± SD) recorded in different treatments
Activity of digestive enzymes (µ moles of product liberated/h/mg protein at 25 °C) in the hepatopancreas of L. fimbriatus and C. catla at harvest
Activity of digestive enzymes (µ moles of product liberated/h/mg protein at 25 °C) in the intestine of L. fimbriatus and C. catla at harvest
Total pigment content (A), biomass (dry matter) of periphyton (B), and biomass (dry matter) of free plankton (C) (mean ± SD) recorded in different treatments
A 90-day experiment with 2 × 2 factorial design—2 levels of substrate (with and without) and 2 levels of feeding (with and without)—was carried out in 16-m² outdoor cement tanks having 5-cm soil base, to evaluate the performance of Labeo fimbriatus in polyculture with Catla catla in periphyton-based culture system with sugarcane bagasse as the substrate. Advanced fingerlings of L. fimbriatus (av. length 19.1 cm and weight 16.81 g) and C. catla (av. length 20.5 cm and weight 11.70 g) were stocked in tanks at a density of 10,000 no./ha in 6:4 ratio. Treatments included no feed, no substrate (NFNS); substrate (S); feed (F); and substrate + feed (S + F) treatments, each tried in triplicates. Sugarcane bagasse was hung vertically at 2 t/ha in S and S + F tanks. Fish in the treatments F and S + F only were fed daily a formulated pelleted feed (25% crude protein and 6% fat) at 5% of fish biomass. Estimation of periphyton biomass and total pigment content was done once in 15 days. Representative fish samples were analyzed for carcass biochemical composition and activity of gut digestive enzyme—total protease, trypsin, chymotrypsin, carboxypeptidase A and B, amylase, lipase, and cellulase—at the end of the growth trial. The weight gains of L. fimbriatus in F (65.05 g) and substrate added tanks (62.75 g in S and 76.48 g in S + F), at the end of the rearing period, was comparable. The weight gain of catla was similar in NFNS (69.17 g) and S treatments (75.25 g) and lower compared to F (100.63 g) and S + F tanks (100 g). While higher moisture and lower crude protein content were observed in the carcass of L. fimbriatus (estimated at harvest) under NFNS treatment, these parameters remained similar with other treatments. In C. catla, S + F recorded the highest crude protein content, with similar values under other treatments. Excepting cellulase in hepatopancreas, the activity of all other enzymes in C. catla showed a pattern corroborating the growth trend, with lower values in NFNS treatment. While the activity of enzymes was higher in fed C. catla compared to the unfed ones, in L. fimbriatus, the activities in all the three treatments were comparable and higher than that recorded in fish under NFNS treatment. The growth performance of L. fimbriatus in polyculture with C. catla in periphyton-enhanced culture system was comparable with those maintained under supplementary feeding, indicating the utility of periphyton enhancement in polyculture.
 
Digestive enzymes were collected from striped catfish given experimental diets containing different grade levels of food waste for 8 weeks. Enzyme activity was determined for amylase (a), cellulase (b), pepsin (c), trypsin (d), chymotrypsin (e), lipase (f), and the ratio of amylase to trypsin was also calculated (g). Data are expressed as tank means ± SEM (n = 3 per treatment). Differences between means were tested with Duncan’s multiple range test. Different superscripts indicate a significant difference (P < 0.05) between treatments
Food waste (FW) is a source of inexpensive and readily available nutrients that can be used as animal feed. However, the use of FW in fish feed is limited. In this study of juvenile striped catfish (Pangasianodon hypophthalmus), commercial feed (CD, 34.1% protein and 4.69% lipid based on dry weight) was replaced with graded levels (25, 50, 75, and 100%) of FW (20.3% protein and 14.9% lipid based on dry weight). The dry weight dietary contents of crude protein (32.8 to 19.9%), crude fiber (4.62 to 1.06%), and ash (9.00 to 3.32%) decreased with FW replacement levels, whereas contents of crude lipid (4.69 to 14.5%) and nitrogen-free extract (48.9 to 61.2%) increased. Fish (3.40 ± 0.01 g body weight) were assigned to five treatments, each comprising three tanks (60 cm width × 80 cm length × 45 cm height, 100 L water) containing 15 fish each. They received the experimental diets twice daily (09.00 and 16.00 h) at 3% of body weight over an 8-week feeding trial. At the end of the feeding trial, growth performance, feed utilization, digestive enzyme activities, fillet qualities, carcass composition, and hematological parameters, along with an economic analysis, were used as assessment criteria for a suitable diet. The gradual reduction in growth performance was observed as the proportion of FW increased (P < 0.05), and only the fish that received a diet containing 25% FW showed similar specific growth rates (1.60% body weight day⁻¹) and feed conversion ratios (1.37 g feed g gain⁻¹) to fish that received a diet without FW (P > 0.05). Higher replacement levels had negative effects on these parameters and increased dry matter apparent digestibility coefficients (from 74.0 to 82.2%), while reducing the protein digestibility coefficients (from 85.8 to 67.9%, P < 0.05). Activities of amylase, cellulase, pepsin, trypsin, chymotrypsin, lipase, and the amylase to trypsin ratio were modulated differently across the dietary treatments. The diet containing 25% FW showed no adverse effects on fillet qualities, carcass composition, and hematological parameters. The cost of a diet containing 25% FW (0.71 USD kg⁻¹) was lower than the cost of the commercial feed (0.94 USD kg⁻¹), albeit not statistically significant (P > 0.05). These findings indicate that replacing 25% of commercial feed with FW could reduce feed costs and mitigate the environmental difficulties of FW disposal.
 
Households’ confidence in the quality of fish (in general) versus wastewater fish by source
Relative importance of different wastewater fish attributes
Variation in WTP based on different perception indicators
This paper explores the potential market opportunities and challenges facing the commercialization of wastewater aquaculture systems in Peru. Peru produces large volumes of wastewater that can be reused to produce fish. However, the long-term sustainability of wastewater aquaculture value chains requires an understanding of consumer preferences and perceptions about product, market and institutional factors. We focus on the role of consumers in wastewater fish value chains and their preferences for different quality and regulatory attributes. The study utilizes data from a field survey conducted in Lima, Peru. A multi-stage stratified sampling technique was used to interview 443 households. A choice experiment was conducted as part of the data collection. Fish attributes analyzed included price, certification, and source. Data on households’ health and environmental perceptions, and trust in regulatory institutions were also collected. The empirical results indicate that household perceptions about the quality of wastewater fish differs by marketing source. We find a strong preference for direct marketing channels. We also find that concerns about the safety of wastewater fish is at the forefront of household considerations. Willingness to pay for wastewater fish was positive but lower than wild and freshwater fish.
 
Difference between coupled and decoupled aquaponic system
Three main types of hydroponic setups used in aquaponics
Aquaponics, a combination of aquaculture and hydroponics, is a potential solution for the consequences of global warming and eventual food meagreness. Aquaponics is known to be an efficient method to deal with the wastewater problem associated with aquaculture and nutrient management issues in the hydroponic discipline. However, optimizing the process condition for aquaponics is frequently ambiguous and is often not economically feasible. Farmers face many constraints in maintaining the process. The main reason for this could be the limited scientific knowledge of various aspects of aquaponics. Through this review, we would like to put a limelight on various critical concerns that could be problematic to beginners in aquaponic farming. These could be from choosing the appropriate design of the system to thriving plants free of diseases. Henceforth, we identified research opportunities that have the potential to fill scientific gaps in this field. Our findings suggest that aquaponics could emerge as the future of agriculture if the discussed challenges are addressed appropriately.
 
Ontogenic changes in shell length of dog conch during the first 20 days after hatching. Data are expressed as means ± SEM, and each data point was calculated from twenty specimens. The small panels show the evolving morphological appearance of dog conch observed under a light microscope. The numbers in the bottom right corner of the panels indicate the days after hatching
Ontogenic changes occurred in protein-digesting enzymes in dog conch during the first 20 days after hatching: pepsin (a), trypsin (b), and chymotrypsin (c) specific activities are presented. Data are expressed as tank means ± SEM (n = 4). Differences between means were tested with Duncan’s multiple range test. Different superscripts indicate a significant difference (P < 0.05) between times
Ontogenic changes in specific activities of lipase (a) and amylase (b) and amylase/trypsin ratio (c) are shown that occurred in dog conch during the first 20 days after hatching. Data are expressed as tank means ± SEM (n = 4). Differences between means were tested with Duncan’s multiple range test. Different superscripts indicate a significant difference (P < 0.05) between times
The ontogenic development of the main digestive enzymes was investigated in veliger larvae of the dog conch (Laevistrombus canarium). The shell length of larvae (y) increased with days after hatching (DAH, x), showing a relationship to x that could be modeled as an exponential equation where y = 634.93e0.0248x (r2 = 0.975, n = 44, P < 0.01). The specific activities of all observed enzymes were significantly influenced by DAH (P < 0.05), and they were prominent at 0DAH before larvae commenced exogenous feeding on day 1. The specific activities of protein-digesting enzymes played an important role at 4 to 6DAH. Their importance declined thereafter, eventually returning to the baseline observed at 0DAH. The response of trypsin and chymotrypsin-specific activities to DAH followed similar trends across all 20DAH. The activities of protein-digesting enzymes were abruptly superseded in the later stages of veliger development by the activities of lipase and amylase, and an increase was observed in the amylase/trypsin ratio, showing the change in energy usage. Since feeding regimens at specific stages of growth were fixed, the variation of digestive enzyme activity is possibly developmentally or genetically programmed. Findings from the current study can be used as reference for feed management for veliger stages of dog conch.
 
Larval morphometrics including body width (BW) and body length (BL) used to calculate body size (calculated as area). (A) Larvae at 3 DPF and (B) larvae at 30 DPF
Larval body size (area; µm² × 10³) and density (larvae mL⁻¹) presented for experiment 1 (a and b), experiment 2 (c and d), experiment 3 (e and f), experiment 4 (g and h), and experiment 5 (i and j) over time. Lower case alphabetical letters adjacent to size and density curves denote significant differences between treatments. Data points are presented as means ± standard error. Microalgae species included Tisochrysis lutea, Chaetoceros muelleri, Chaetoceros gracilis, and Rhodomonas lens
Slow or nonexistent natural recovery of the Caribbean long-spined sea urchin (Diadema antillarum) following a mass mortality event in 1983-1984 has prompted interest in hatchery-origin production and restocking to aid coral-reef restoration. A critical first step is the ability to propagate D. antillarum from gametes, at scale. However, a unique larval biology and difficult and lengthy culture period of ~ 40 days has resulted in inconsistent success over the past 20-plus years. The purpose of this study was to develop protocols for rearing D. antillarum within a novel 1800-L recirculating aquaculture system capable of scaled production. Five separate experiments investigated larval development in response to diet quantity, diet composition, and initial stocking density within 40-L replicate culture tanks. The initial experiment was used to develop a microalgae reference diet consisting of Tisochrysis lutea and Chaetoceros sp. and revealed similar growth and survival between high quantity (40.0 × 10 3 cells mL −1) and low quantity (10.0 × 10 3 cells mL −1) treatments at 21 days post-fertilization (DPF). Experiments 2-4 examined diet quality by comparing carbon-equivalent microalgae compositions. Mixed diets containing Rhodomonas lens outperformed the reference diet in multiple experiments and a tripartite diet containing all three species resulted in significantly higher survival at 42 DPF. The highest growth overall occurred from a monoalgal R. lens diet, which indicated that this species is critically important. Further observations of density-dependent growth dynamics revealed that initial stocking densities > 1 larvae mL −1 significantly reduced growth over 28 DPF. Data generated were used to establish fundamental larviculture protocols that have since led to the production of over 1000 juveniles.
 
Antioxidant indexes in hemolymph of E. sinensis after PVP-I treatment for 3 days and after A. hydrophila infection within 24 h. (A) Superoxide dismutase (SOD) activity; (B) peroxidase (POD) activity; (C) total antioxidant capacity (T-AOC); (D) malondialdehyde (MDA) content. The values are expressed as the means ± SD (n = 6). Different letters above the column represent the significant differences with the same group at different time points (p < 0.05). “Asterisk” denotes significant differences between the control and PVP-I groups at the same time point (“*” p < 0.05; “**”p < 0.01)
The total hemocyte counts (THC) of E. sinensis after PVP-I treatment for 3 days and after A. hydrophila infection within 24 h. The values are expressed as means ± SD (n = 6). Different letters above the column represent the significant differences with the same group at different time points (p < 0.05). “Asterisk” denotes significant differences between the control and PVP-I groups at the same time point (“*” p < 0.05; “**”p < 0.01)
Hemocyanin content in hemolymph of E. Sinensis after PVP-I treatment for 3 days and after A. hydrophila infection within 24 h. The values are expressed as means ± SD (n = 6). Different letters above the column represent the significant differences with the same group at different time points (p < 0.05). “Asterisk” denotes significant differences between the control and PVP-I groups at the same time point (“*” p < 0.05)
Immune enzyme activity in hemolymph of E. sinensis after PVP-I treatment for 3 days and after A. hydrophila infection within 24 h. (A) Alkaline phosphatase (AKP); (B) acid phosphatase (ACP); (C) lysozyme (LZM). The values are expressed as means ± SD (n = 6). Different letters above the column represent the significant differences with the same group at different time points (p < 0.05). “Asterisk” denotes significant differences between the control and PVP-I groups at the same time point (“*” p < 0.05; “**” p < 0.01)
The relative mRNA expression of immune-related genes in hemocytes of E. sinensis after PVP-I treatment for 3 days and after A. hydrophila infection within 24 h. (A) Crustin; (B) prophenoloxidase (ProPO). The values are expressed as means ± SD (n = 6). Different letters above the column represent the significant differences with the same group at different time points (p < 0.05). “Asterisk” denotes significant differences between the control and PVP-I groups at the same time point (“*” p < 0.05; “**” p < 0.01)
The bacterial disease is a major constraint to the aquaculture industry of the Chinese mitten crab (Eriocheir sinensis). Povidone-iodine (PVP-I) is a broad-spectrum chemical microbicide with fungicidal activities against pathogens. In this study, E. sinensis were soaked with PVP-I (4.38 mg/l, safe concentration) for 3 days and then infected by Aeromonas hydrophila (4 × 10⁵ CFU/ml, 90 μl). The antioxidant capacity and immunity of E. sinensis were evaluated after being treated by PVP-I for 3 days and then infected by A. hydrophila for 3 h, 12 h, and 24 h. The results demonstrated that antioxidant capacity and immunity of E. sinensis were improved after PVP-I treatment for 3 days, and the activities of superoxide dismutase (SOD), alkaline phosphatase (AKP), and lysozyme (LZM) in hemolymph, the total hemocyte count (THC), and mRNA expression levels of Crustin in hemocytes were significantly higher than the control group. After A. hydrophila infection, E. sinensis in the PVP-I group exhibited strong antioxidant capacity. At all time points post-infection, the activities of SOD and total antioxidant capacity (T-AOC) of hemolymph in the PVP-I group were higher, and the contents of malondialdehyde (MDA) were significantly lower than in the control group. PVP-I group showed better immune performance, and the contents of THC and hemocyanin, the activities of AKP and LZM in hemolymph, and the mRNA expression of Crustin in hemocytes were usually significantly higher than the control group after infection. Therefore, short-term treatment by PVP-I can increase E. sinensis’ antioxidant capacity and immunity and improve resistance to A. hydrophila.
 
Fluctuation of pH (mean ± standard deviation) during the synbiotic preparation process. abc*Different letters between columns represent significant differences (p < 0.05) between treatments by Conover’s multiple test with Holm-Bonferroni correction. T24|24 = 24 h anaerobic and 24 h aerobic; T12|24 = 12 h anaerobic and 24 h aerobic. SB = sodium bicarbonate; CA = dolomitic limestone; LT = Lithothamnium
Concentrations of nitrogen compounds during the preparation process of bioreactors with a synbiotic system over 5 weeks. T12|12 = 12 h anaerobic and 12 h aerobic; T12|24 = 12 h anaerobic and 24 h aerobic; T24|0 = 24 h anaerobic; T24|12 = 24 h anaerobic and 12 h aerobic; T24|24 = 24 h anaerobic and 24 h aerobic. TAN, total ammonia nitrogen
Values of variables TAN (A), N-NO2 (B), N-NO3 (C), and settleable solids—SS (D) throughout the experimental period. Treatment 24|24 = 24 h anaerobic and 24 h aerobic; treatment 12|24 = 12 h anaerobic and 24 h aerobic; treatment 24|12 = 24 h anaerobic and 12 h aerobic; treatment 24|0 = 24 h anaerobic; treatment 12|12 = 12 h anaerobic and 12 h aerobic
The prawn Macrobrachium rosenbergii post larvae (10.01 ± 2.00 mg) were evaluated using a synbiotic system with different fermentation (anaerobic) and microbial respiration (aerobic) strategies after 35 days. Rice bran, a mix of probiotic microorganisms, alkalizing agents, and water were used in the preparation of the synbiotic. There were five treatments in quadruplicate, consisting of the following: T12|12 = 12 h anaerobic and 12 h aerobic; T12|24 = 12 h anaerobic and 24 h aerobic; T24|0 = 24 h anaerobic; T24|12 = 24 h anaero-bic and 12 h aerobic; T24|24 = 24 h anaerobic and 24 h aerobic. The prawns were fed four times a day (40% crude protein) and the main variables of water quality and prawn growth were evaluated. The synbiotic preparation strategies used did not influence the stabilization time of nitrogen compounds in water. There were no differences in the survival and the water quality variables, which remained adequate for the species. For the variables final average weight (mg) and yield (gm −3), treatments T24|24 (221.3 ± 22.0 and 195.4 ± 14.6) and T12|24 (218.2 ± 27.6 and 196.2 ± 33.4) were higher than 24|00 (176.1 ± 24.5 and 151.3 ± 21.6). Thus, it is concluded that a longer preparation time of the fertilizer, especially contemplating the anaerobic and aerobic stages, can promote greater performance of the reared prawns.
 
Mean net revenue, costs, income, and benefit–cost ratio (B/C) as a function of rearing time for the alternative seeding-harvesting schedules under the pre-pandemic (17–19) and pandemic (20) scenarios
Probability distributions of net revenue for the alternative seeding-harvesting schedules under the pre-pandemic (17–19) and pandemic (20) scenarios. The values corresponding to the dashed lines indicate the 95% probability intervals. Different letters indicate significant differences among the scenarios for each schedule separately. SD standard deviation, CV coefficient of variation, LP loss probability
This study uses a stochastic bioeconomic approach to estimate the COVID-19 pandemic economic impact on shrimp farming in Mexico. Seeding-harvesting schedules — March–June, May–August, and August–November — were analyzed using shrimp prices and production costs corresponding to 2017–2019 (pre-pandemic) and 2020 (pandemic). The analyses estimated net revenue varied within 597.97–2758.88 USD$ ha⁻¹ and 1262.40–1701.32 USD$ ha⁻¹ under the pre-pandemic and pandemic scenarios, respectively. Significant decreases (38%) were estimated in net revenue values in March–June and May–August under the pandemic scenario. However, probability distributions estimated that uncertainty on the expected net revenues was not affected by the pandemic conditions, and the probability of losing was null or negligible in all the cases. Unfavorable conditions under the pandemic also required significantly higher break-even production for March–June (25.7%) and May–August (28.5%) schedules. The cost of post-larvae was the most important economic factor influencing net revenue. To conclude, although the operating conditions during the pandemic were conducive to worsening the economic outcome, no evidence still exists that uncertainty and economic risk increased compared with pre-pandemic conditions.
 
Evaluation of total immunoglobulin (total Ig) and lysozyme activity (Lyz) values in goldfish fed with acidifier-supplemented diets. Data represent means ± SD. Bars assigned with the same superscripts are not significantly different (p > 0.05); values are presented as the mean ± SD (n = 9). SB1, sodium butyrate 0.1%; SP1, sodium propionate 0.1%; SB2, sodium butyrate 0.2%; SP2, sodium propionate 0.2%; SB1SP1, sodium butyrate 0.1% + sodium propionate 0.1%; SB2SP2, 0.2% sodium butyrate + 0.2% sodium propionate
Gene relative expression of tumor necrosis alpha (TNF-α), interleukin1-β (IL-1β), interleukin-8 (IL-8), and lysozyme (LYZ) in goldfish fed with acidifier-supplemented diets. Bars assigned with the same superscripts are not significantly different (n = 9; p > 0.05). SB1, sodium butyrate 0.1%; SP1, sodium propionate 0.1%; SB2, sodium butyrate 0.2%; SP2, sodium propionate 0.2%; SB1SP1, sodium butyrate 0.1% + sodium propionate 0.1%; SB2SP2, 0.2% sodium butyrate + 0.2% sodium propionate. The reference gene (β-actin) was used for normalization
This research was designed to appraise the single or combined effects of dietary sodium butyrate (SB) and sodium propionate (SP) on growth, serum biochemical parameters, serum and skin mucus immune responses, and expression of immune-related genes in goldfish fry. To design seven experimental groups in triplicates, the fry (n = 315; 5.6 ± 0.1 g) were randomly stocked in 21 tanks (150 L) with a density of 15 fish per tank. In this study, a basal diet (36.81% crude protein, 11.33% lipid, and 3.5% ash) was considered as the control diet and the other experimental diets were formulated by adding SB 0.1% (SB1), SP 0.1% (SP1), SB 0.2% (SB2), SP 0.2% (SP2), SB 0.1% + SP 0.1% (SB1SP1), and 0.2% SB + 0.2% SP (SB2SP2) into the basal diet. The fish were fed ad libitum with the corresponding diets three times per day for 56 days. The current study was measured the serum biochemical and immune parameters, mucus immunity, and the expression of immune-related genes using the blood, mucus, and head kidney samples, respectively. After 56 days, the highest growth rate (2.85 ± 0.04%/day) and the lowest feed conversion ratio (1.65 ± 0.06) were recorded in SB2SP2 treatment (p < 0.05). The serum lysozyme activity enhanced 1.76 folds in the fish fed with SB2SP2 diet compared to the control group (p < 0.05). Moreover, the highest skin mucus lysozyme activity (17.52 ± 1.40 U/mL) was observed in B2SP2 treatment, which showed a 1.69-fold increase compared to the control groups (p < 0.05). Total immunoglobulin levels in the serum and mucus samples of the blended acidifier-supplemented diets were significantly higher than the control group (p < 0.05). The levels of serum alanine aminotransferase, aspartate aminotransferase, glucose, and cortisol significantly decreased in all treated fish compared to the control fish (p < 0.05). The relative transcription levels of tumor necrosis-α, lysozyme, interleukin-1β, and interleukin-8 genes were significantly upregulated in SP2SB2 group compared to the control group. The results of the present study revealed the beneficial synergistic effects of dietary SB and SP, especially at 0.2%, on the growth performance, physiological responses, and immunity of goldfish.
 
A seasonal comparison of the nutritional profile of sea lettuce (Ulva lactuca) produced in a land-based integrated multi-trophic aquaculture (IMTA) system in Florida was conducted quarterly (March, June, September, December) over the course of an annual production cycle. Nutritional parameters evaluated included proximate analysis, mineral and total carotenoid content, and amino acid profile. Water quality parameters evaluated included temperature, salinity, pH, light availability, and nitrogenous compounds. No significant differences with respect to seasonality were seen with regard to proximate analysis. In contrast, significant differences were noted in mineral concentrations for potassium (highest spring, lowest fall), copper (highest spring, lowest winter), and iron (highest fall, lowest summer). Levels of arsenic, cadmium, and lead were below European Union (EU) recommended threshold levels, and no mercury was detected. Seasonal variation was seen in arsenic (highest in fall) and cadmium (highest in spring). The percent of non-essential amino acids was higher than that of essential amino acids, with high concentrations of aspartic acid, glutamic acid, and alanine noted in all seasons. Carotene concentrations ranged from 114 to 229 mg/kg. In general, the nutritional profile of U. lactuca produced in a sub-tropical IMTA system is seasonally consistent, allowing harvested product to be utilized year-round without concern for nutritional loss.
 
The aim of the present study was to study the effect of different dietary phospholipid sources derived from krill (KPL) and soybean lecithin (SBL) with different levels of phosphatidylcholine (PC) and n-3 HUFA on the performance and histological changes in intestine and liver of seabream larvae. Larvae (16 dph) were fed for 1 month five formulated microdiets (control, 7KPL, 9KPL, 7SBL, and 9SBL). The larvae fed dietary KPL rich in phosphatidylcholine and n-3 PUFA showed better performance in terms of survival and growth than those fed SBL. The inclusion of KPL up to 7% PL (3.8% PC and 7.7% n-3HUFA) in diet was sufficient enough to improve significantly the larval survival and growth compared to the highest dietary 9% PL of SBL (2.5% PC and 5.6% n-3HUFA); in addition, the larvae fed KPL showed higher content of n-3HUFA specially EPA and DHA. The larval survival and total length were positively correlated to dietary PC and n-3HUFA contents. But, inclusion of SBL was associated with a high relative accumulation of lipid droplets in the supranuclear zone of the enterocytes and in hepatocytes compared to larvae fed dietary KPL. The intestinal and hepatic steatosis was negatively correlated to dietary PC content. In conclusion, dietary 7% KPL (3.8% PC and 7.7% n-3 HUFA) improved significantly the larval survival and growth and decreased significantly the intestinal and hepatic steatosis compared to SBL, denoting better dietary lipid absorption, transportation, and energetic utilization.
 
The light conditions of the natural photoperiod treatment during the experiment. a Light intensity (at 12:00 pm) and photophase. b Daily light intensity fluctuations for a typically sunny and rainy day
The staged survival rate of P. trituberculatus under different photoperiods (mean ± SD, n = 4). a Zoea I, b Zoea II, c Zoea III, d Zoea IV, e Megalopa. Different letter indicates significant difference (P < 0.05)
The cumulative survival rate of P. trituberculatus under different photoperiods (mean ± SD, n = 4). a Zoea I, b Zoea II, c Zoea III, d Zoea IV, e Megalopa. Different letter indicates significant difference (P < 0.05)
The cumulative development duration (days) of larvae in different photoperiods (mean ± SD, n = 4). a Zoea I, b Zoea II, c Zoea III, d Zoea IV, e Megalopa. Different letter indicates significant difference (P < 0.05)
Photoperiod is a crucial environmental factor affecting the survival and development of crustacean larvae. The full-spectrum light-emitting diodes (LEDs) were used as light sources to investigate the effect of five photoperiods, i.e., 0 L:24D (constant darkness), 6 L:18D (6 h photophase), 12 L:12D (12 h photophase), 18 L:6D (18 h photophase), and 24 L:0D (constant light) on the survival and development of the swimming crab Portunus trituberculatus larvae (from zoea I to juvenile crab). Natural photoperiod (ambient) was used as a control group. Each treatment had four replicates (n = 4, 100 larvae per replicate). The experiment lasted 20 days when all the larvae died or metamorphosed into juvenile crabs. The results revealed that the P. trituberculatus could not metamorphose into juvenile crab under constant darkness, 6 h photophase, and constant light, and all the larvae died in zoeal III, zoeal IV, and zoeal IV stage, respectively. The highest survival and the shortest developmental duration of larvae were found in the 12 h photophase group (1.75%, 16.80 d) but were not statistically different from those reared in the 18 h photophase group (0.75%, 17.00 d) and natural photoperiod (0.25%, 18.90 d). The above results indicated that full-spectrum LEDs could be a considerable alternation for natural light, and the optimal photoperiod for P. trituberculatus larvae is 12–18 h photophase.
 
Total length, standard length, caudal fin ray elements (CFRE), and morphological characteristics of developmental stages of Nile tilapia (Oreochromis niloticus). Photographs: A 2 DPH, 38.8 × ; B 4 DPH, 38.8 × ; C 6 DPH, 31 × ; D 13 DPH, 24.8 × ; E 20 DPH, 21.7 × . DPH days post-hatching. (n = 10)
Acid (a) and alkaline (b) specific peptidase activity of Nile tilapia (Oreochromis niloticus) in different development stages. Different letters indicate significant different (P < 0.05) (n = 4 of 7 pooled individuals)
Zymogram of alkaline enzyme extracts and their mixture. (*) Nile tilapia (Oreochromis niloticus) activity bands. (o) Exogenous enzymes activity bands; 2, 3, and 6: enzyme extract of tilapia of 2, 3, and 6 DPH respectively; shrimp (Pleoticus muelleri) cephalothorax enzyme extract. DPH days post-hatching. Some bands appear weak due to the low activity of the Nile tilapia extracts and the impossibility of adding more extract to the gel lane
During the early ontogeny, the transition from endogenous (yolk protein) to exogenous feeding (artificial diets) represents a critical period linked to the undifferentiated digestive system, with low digestibility of food protein. The objectives of this work were to characterize the morphology of the early Nile tilapia (Oreochromis niloticus) developmental stages and determine the activity of alkaline and acid peptidase enzymes during the ontogenesis from hatching to 20 days post-hatching (DPH). Also, the in vitro effect that exogenous enzymes from Argentine red shrimp (Pleoticus muelleri) waste have on the alkaline peptidases of larvae from 6 to 20 DPH (which correspond to the age at which fish eat exogenous food) was studied. Both acid and alkaline peptidase activities varied throughout early ontogeny development (from 0.1 to 1, and from 0.1 to 7.1 UE mg protein⁻¹, respectively). The patterns of both enzyme activity variation would be related with changes in endogenous, mixed and exogenous feeding. Our studies show that the additions of the enzyme extract of shrimp have a synergistic effect (from 3 to 6 times) on endogenous in vitro activity. Moreover, the zymogram analysis demonstrates that the bands corresponding to the activity of each species (tilapia and red shrimp) remain active when they are mixed. The increase in peptidase digestive capacity by addition of exogenous enzymes would maximize the assimilation of nutrients from artificial food during early development.
 
Overview of the larviculture recirculation system. Larval culture tanks (1); microalgae container (2); sump (3) for components of the filtration system; heat exchanger (4); dosing pump (5); UV filter (6); protein skimmer (7); flow meter (8); seawater distribution manifold (9); heat exchange pump (10); UV filter and return to system pump (11); skimmer pump (12). Recirculated water from each larval tank delivered via the collection gutter (13; white gutter) to the sump; the filtered water is carried (brown lines) from the sump (3) to the cultivation units. The flow directions of air, waste water and filtered water are represented by arrows (red) (blue line, white gutter and brown lines, respectively). Software: Solidwork. Drawing: Caique Sales de M. Gomes.
Details of the larviculture recirculation system. A Line of microalgae silicone tubing (1); collection gutter (2); dosing pump (3); flow meter (4) and larval culture tanks (5). Details of larval culture tank. B Larval culture tank (1); tank float valve (2) seawater and algal inflow connector to avoid larvae escapement if tank seawater exceeded desired levels; seawater overflow (3); banjo (4); and air inflow silicone tubing (5). The flow directions of air and water are represented by arrows (red). Software: Solidwork. Drawing: Caique Sales de M. Gomes.
Percentage of larval yield (A) and competent larvae (B) in the initial stocking densities of 80 (D80), 160 (D160) and 320 (D320) larvae mL⁻¹ and flow of water of 100 (F100), 200 (F200) and 300 (F300) mL min⁻¹. Averages followed by different letters are statistically different (p < 0.05) between levels of the main effects (stocking densities and flow of water). Data indicate mean ± standard deviation (n = 9). Lowercase letters indicate different between stocking densities and higher case letters indicate difference between the effects of flow.
Percentage of larval yield (A) and competent larvae (B) in the initial stocking densities of 80 (D80), 160 (D160) and 320 (D320) larvae mL⁻¹ and flow of water of 100 (F100), 200 (F200) and 300 (F300) mL min⁻¹. Averages followed by different letters are statistically different (p < 0.05) within main effects (slice of the interactions). Data indicate mean ± standard deviation (n = 3). Lowercase letters indicate different between flow within of stocking densities and higher case letters indicate difference between the stocking densities within of flow.
Mean time required for the first larvae to reach competency in the initial stocking densities of 80 (D80), 160 (D160) and 320 (D320) larvae mL⁻¹ and flow of water of 100 (F100), 200 (F200) and 300 (F300) mL min⁻¹. Averages followed by different letters are statistically different (p < 0.05) by Tukey test. Data indicate mean ± standard deviation (n = 9). Lowercase letters represent the effects of different stocking densities, and higher case letters represent the effects of different flows.
The present study evaluated the effect of initial stocking density and water recirculation rate on larval yield (percent of initially stocked larvae alive at the end of the experiment) and production of competent larvae (percent of initially stocked larvae alive at the end of the experiment retained on a sieve with mesh size 239 μm) of Crassostrea gigas in a recirculation aquaculture system (RAS). Different initial larval stocking densities (80, 160 and 320 larvae mL⁻¹) and water flow rates (100, 200 and 300 mL min⁻¹, totalling renewal rates of 60, 120 and 180 times day⁻¹ of water volume in culture tanks, respectively) were evaluated in 2.4-L tanks using a completely randomized design in a factorial scheme. The physicochemical parameters of the water (temperature, salinity, pH, dissolved oxygen and conductivity) were stable in all treatments during the experimental period. Our results demonstrated that the production of C. gigas larvae was feasible at the proposed densities. However, the water renewal rate affected both yield and competent larvae in the recirculation aquaculture system. Oyster cultures with densities of 160 larvae mL⁻¹ and flow of water of 300 mL min⁻¹ showed the best yield (89.34 ± 18.43%) and rate of competent larvae (84.09 ± 16.38%) and are therefore recommended with the aim of optimizing larvae cultivation.
 
The main objective of intensive whiteleg shrimp Penaeus vannamei cultivation is to obtain high productivity to meet market needs. One of the efforts to boost production is to provide optimal feeding to increase the shrimp growth rate. This study analyzes the productivity of an intensive shrimp farm using Powersim simulations based on specific growth rates (SGR) and average daily growth (ADG) to determine the resulting production criteria. The cultivation lasted for 90 days by stocking 16 grow-out ponds with post-larvae (PL10) at a density of 80 PL per m2. Shrimp samples were weighed every 10 days after day-30 of culture until harvest. The average productivity obtained from this study was 8.86 t/ha/crop. According to our criteria, this productivity level was low, presumably, due to the low growth rate that may have resulted from low-quality larvae, sublethal nitrite concentrations, low survival rate, and high feed conversion ratio. The SGR-based and ADG-based simulations using Powersim Studio 10 Express confirm the low production, which does not meet the criteria for intensive farming. However, ADG-based simulation shows that the prolonged culture to 126 days results in higher shrimp production and productivity that fall into the lower level of the intensive system. This study also proposes production criteria and productivity ranges for whiteleg shrimp farming.
 
Some physicochemical changes in the water of aquaponic system using Nile tilapia (Oreochromis niloticus) and saffron plant (Crocus sativus) were measured every 20 days. Each bar represents the mean value ± SD (n = 9). Bars assigned with different superscripts are significantly different in each treatment on different days (P ≤ 0.05)
Effects of different concentrations of ascorbic acid (vitamin C) in culture water, on the intestinal (proximal intestine (PI), mid-intestine (MI), and distal intestine (DI)) digestive enzyme activity such as A trypsin (change in absorbance per minute per gram of tissue), B chymotrypsin (change in absorbance per minute per gram of tissue), C lipase (µmol of fatty acids released per minute per gram of tissue), and D amylase (µmol of maltose released per minute per gram of tissue) of O. niloticus, in an aquaponic system using saffron plant. Each bar represents the mean value ± SD (n = 6). Bars assigned with different superscripts indicate a significant difference in enzyme levels in each part of the intestine (P ≤ 0.05)
The aim of this study was to investigate the possibility of improving the growth and physiological indices of plant and fish by adding different levels of ascorbic acid (vitamin C) to water in the aquaponic system using Nile tilapia (Oreochromis niloticus) and saffron plant (Crocus sativus). 240# fish (12.5 ± 0.21 gr) and 120# saffron corms (2.8 ± 0.12 gr) were randomly assigned to 15 experimental units and underwent treatments of adding 0 (control), 2, 4, 6, and 8 mg L⁻¹ ascorbic acid to water, every 6 days, for 8 weeks. The fish final weight and subsequently other growth performance indices increased in the treatment of 4 mg L⁻¹ vitamin C compared to other treatments (P ≤ 0.05). Some growth performances of saffron plants such as saffron production, in treatment of 6 mg L⁻¹, were significantly higher than the control group and reached from 17.34 ± 0.27 mg flower⁻¹ in the control group to 25.4 ± 1.61 mg flower⁻¹ in treatment of 6 mg L⁻¹. Measuring the serum biochemical parameters of the fish showed that, in the treatment of 8 mg/L ascorbic acid, the cortisol content in the blood reached its maximum (21.49 ± 2.42 µg dL⁻¹). The trypsin activity in proximal intestine and mid-intestine significantly increased in treatments of 2, 4, and 6 mg L⁻¹, respectively. The current experiment showed that, by adding 4–6 mg/L ascorbic acid to the aquaponic system water (every 6 days), the optimal levels of Nile tilapia and saffron plant growth performances would occur.
 
HPLC of pyocyanin: a pyocyanin extract from P. aeruginosa and b pyocyanin standard (M/s Color Your Enzyme, Canada)
Pyocyanin cytotoxicity on PmLyO-Sf9 using MTT assay. The different alphabets denote significantly different values (Tukey, p < 0.05)
Twenty-four-hour post-exposure of pyocyanin to PmLyO-Sf9. White arrows indicate morphological changes induced: a cell enlargement and b vacuole formation
Seventy-two-hour post-exposure of pyocyanin to PmLyO-Sf9. White arrows indicate morphological changes induced: a vacuole formation, b change in cell shape, c cell lysis and d disruption of the cell monolayer
Diseases are one of the most critical limiting factors in aquaculture. Recirculating aquaculture systems (RAS) are one of the most functionally viable sustainable aquaculture production systems adopted world over. In the event of any eventuality caused by bacterial pathogens, antibiotics or other antibacterial agents cannot be applied due to the vulnerability of biological filters which form an integral part of the RAS. Because of this, newer drugs are required for the effective control of diseases in RAS which would not interfere with the activity of nitrifying bacteria used in the biological filters. The antagonistic activity of pyocyanin, a bioactive compound produced by Pseudomonas aeruginosa, against vibrios is well established. The purpose of this study was to prove the effectiveness of pyocyanin as an aquaculture drug for application in RAS by employing a pilot-scale shrimp culture under RAS. It was noted that at the concentration of 5 mg L⁻¹, pyocyanin could significantly bring down the population of Vibrio spp. in RAS without affecting noticeably the other natural heterotrophic bacteria. Also, pyocyanin at this concentration did not inhibit the activity of nitrifying bacterial consortia used in the SBSBR (stringed bed suspended bioreactor) of RAS. The reared shrimp (Penaeus monodon) showed 100% survival after the application of pyocyanin, besides exhibiting normal health signs. Pyocyanin was non-toxic to the shrimp hybrid cell line (PmLyO-Sf9) at the concentration required for its application in disease management (IC50 = 419.26 mg L⁻¹). The present study has demonstrated that pyocyanin is effective as an environment-friendly and safe aquaculture drug for the application in RAS-based shrimp culture to control Vibrio spp. without impeding nitrification established through the deployment of nitrifying bioreactors.
 
Bacteriophage infecting V. harveyi which isolated from shrimp farm effluent against shrimp bacterial pathogens
Lytic activity performed by spectrophotometric assessment of phage-treated cultures of V. harveyi at different time intervals. Bars with different lowercase letters are statistically different from each other (n = 3) (one-way ANOVA, P < 0.05, and subsequent post hoc multiple comparisons with SNK test)
a Heat sensitivity of bacteriophage treated with different temperature incubation. Bars with different lowercase letters are statistically different from each other (n = 3) (one-way ANOVA, P < 0.001, and subsequent post hoc multiple comparisons with SNK test). b pH sensitivity of bacteriophage treated with different temperature incubation. Bars with different lowercase letters are statistically different from each other (n = 3) (one-way ANOVA, P < 0.001 and subsequent post hoc multiple comparisons with SNK test)
Positive correlation observed between burst time and burst size with reference to one-step growth curve. Values are the mean of three determinations ± SEM (P < 0.05) (n = 3)
Bacteriophage isolated from the semi-intensive culture of Pacific white leg shrimp Litopenaeus vannamei infects the luminous bacteria Vibrio harveyi. Lytic activity and lytic spectrum results revealed that the isolated phage had strong lytic activity in V. harveyi, V. parahaemolyticus, and V. vulnificus. Biofilm inhibition activity was performed against different pathogenic vibrios on high-density polyethylene (HDPE) template and the result revealed that the phage effectively inhibited the biofilm formation in V. harveyi. Spectrophotometric assay performed for lytic activity of the isolated phage in V. harveyi liquid culture showed that the phage significantly decreased the V. harveyi cell densities at different time intervals (P < 0.05). To study the stability of phage at different temperature and pH revealed that the phage withstands the temperature ranged between 40 and 70 °C and the pH of 4 and 9 at a significant level (P < 0.001). One-step growth curve depicted that the burst size gradually increased to a significant level and reached the maximum of 90% at 180 min (P < 0.05). This study concluded that the isolated phage had specific activity against pathogenic V. harveyi infections.
 
Gross lesions in monosex Nile tilapia Oreochromis niloticus fries exposed to varying concentrations of oxytetracycline during the experimental period. [A] Untreated control; [B] mouth wide open at 2100 mg/L (3X group); [C] opercular flaring at 3500 mg/L (5X group); [D] burst belly at 7000 mg/L (10X group)
Histopathological alterations in the kidney of monosex Oreochromis niloticus fries exposed to varying concentrations of oxytetracycline on day 30. [A] Untreated control at × 200; [B] 350 mg/L (0.5X group) at × 200; and [C] 2100 mg/L (3X group) at × 400, and on day 15 post-exposure [D] 0.5X group at × 400 and [E] 3X group at × 200 showing disintegration of the nephritic tubule (D), necrosis (N), glomerulopathy (G), degeneration of epithelial lining (DE), hypertrophied nephritic tubular cells (H), widened lumen (W), inflamed nephritic tubule (IN), and vacuolation in the nephritic tubule (V); H&E staining
Histopathological alterations in the liver of monosex Oreochromis niloticus fries exposed to varying concentrations of oxytetracycline on day 30. [A] Untreated control at × 200; [B] 350 mg/L (0.5X group) at × 400; [C] 700 mg/L (1X group) at × 400; and [D] 2100 mg/L (3X group) at × 400; and on day 15 post-exposure [E] 0.5X group at × 200; [F] 1X group at × 200; and [G] 3X group at × 200 showing fatty changes in the hepatic tissue (F), necrotized hepatic tissue (N), vacuolation in the pancreas (V), loosely packed hepatic parenchyma (LPH), densely packed hepatic parenchyma (DPH), and erythrocyte infiltration into blood sinusoids (EI); H&E staining
Histopathological alterations in the gills of monosex Oreochromis niloticus fries exposed to varying concentrations of oxytetracycline on day 30. [A] Untreated control at × 200; [B] 350 mg/L (0.5X group) at × 200; [C] 700 mg/L (1X group) at × 200; and [D] 2100 mg/L (3X group) at × 200; and on day 15 post-exposure [E] 0.5X group at × 200; [F] 1X group at × 400; and [G] 3X group at × 200 showing desquamation of secondary lamellar epithelium (DS), epithelial lifting (LE), shortening of secondary lamellae (SHL), inflammation of secondary lamellar tip (I), inflamed cartilaginous core (ICC), epithelial detachment (ED), lamellar fusion (LF), necrotized primary lamellae (N), curling of secondary lamella (C), and non-nucleated pillar cells (NNP); H&E staining
Histopathological alterations in the intestine of monosex Oreochromis niloticus fries exposed to varying concentrations of oxytetracycline on day 30. [A] Untreated control at × 200; [B] 350 mg/L (0.5X group) at × 200; [C] 2100 mg/L (3X group) at × 200; and on day 15 post-exposure [D] 1X group at × 200; and [E] 3X group at × 400 showing deeply stained mucoid epithelial cells and disintegrated muscularis mucosae (DM), altered integrity of the gut mucosa with degeneration of the muscularis mucosae (D) and necrosis (N), and degeneration of the epithelial lining (DE); H&E staining
The current study evaluated the biosafety of oxytetracycline (OTC) exposure for 30 days in monosex Oreochromis niloticus fries. The fries were exposed to OTC for 3 h/day for 30 days at 350 (0.5X), 700 (1X), 2100 (3X), 3500 (5X), and 7000 (10X) mg/L and com- pared with control (0X). The OTC exposure at 5X and 10X concentrations caused 100% mortality within 4 days and 5 min, respectively. The mortalities recorded in 0.5X, 1X, and 3X groups were 3.33±1.15%, 14.67±1.15%, and 47.33±11.37% on day 30, respectively. The feed intake was decreased up to 23.33% in the 3X group during the exposure period. The OTC residue levels on 30-day exposure were 216.53±14.71, 450.56±44.31, and 1141.26±63.64 μg/kg, which reduced to 40.40±3.25, 76.68±2.77, and 95.61±5.13 μg/ kg after 15 days of termination of exposure in the 0.5X, 1X, and 3X groups, respectively. The histopathological changes observed in the 1X group were epithelial detachment, des- quamation of secondary lamellar epithelium, lamellar fusion, and infamed cartilaginous core in the gills, alteration in the integrity of gut mucosa, degeneration of muscularis mucosae and necrosis in the intestine, the disintegration of the nephritic tubule, necrosis, and glomerulopathy in the kidney, and dilated vascular duct, necrotized hepatic tissue, dif- fused hepatic parenchyma, vacuolation, and fatty changes in the liver. The OTC exposure induced marked tissue changes histologically in a dose- and time-dependent manner, which undoubtedly reduced the growth of tilapia.
 
Biofloc technology (BFT) is an environmentally friendly aquaculture technology and has been demonstrated to improve water quality and promote the growth, immunity, disease resistance, and reproduction of some cultured animals. The lined seahorse (Hippocampus erectus) has been cultured in China for more than 10 years; however, there are still some major problems in large-scale culture, one of which is that juveniles are prone to enteritis. In this study, to test the feasibility of BFT for H. erectus juvenile, the effects of different carbon sources (glucose, sucrose, or corn starch) and carbon–nitrogen ratios (C/N, 16:1 or 20:1) on the water quality, survival, growth, and intestinal biochemical parameters of juveniles cultured under zero-water exchange conditions were investigated. The results show that different combinations of carbon source and C/N had different effects. Some combinations had significant positive effects, while others had no or even negative effects. The best positive effects appeared in combinations of glucose and C/N 16:1, and sucrose and C/N 16:1, which were mainly reflected in the reduction of ammonia and nitrite in water, the promotion of bacterial proliferation and community diversity in water; and the improvement in intestinal microflora, digestion, immunity and survival of the juveniles. In conclusion, adding extra organic carbons to water is promising to improve the culture of H. erectus juveniles, as long as the carbon source type and C/N are properly combined (e.g., glucose or sucrose at C/N 16:1). This study may provide a new potential method for seahorse enteritis.
 
Aquaculture research has focused on polysaccharides as they are among the most promising new-generation immunostimulant used to control aquatic diseases. The aim of this study was to investigate the immunomodulatory effects of fermented wheat bran polysaccharides (FWBPs) on juvenile common carp (Cyprinus carpio). Carps were fed different FWBP amounts (0%, 0.1%, 0.2%, and 0.4%) for 8 weeks and then their skin mucus and serum immune parameters, hepatopancreas antioxidant indicators, and immune-related gene expression in the intestines, kidneys, and spleen were measured. The skin mucus IgM levels significantly increased in 0.1% FWBP group, but decreased in 0.4% FWBP group. The skin mucus protease and the serum alkaline phosphatase activities increased significantly in the 0.2%, 0.1%, and 0.4% FWBP groups, respectively. The serum total Ig levels increased noticeably in the 0.1% and 0.2% FWBP groups. The highest and lowest serum lysozyme activities were observed in the 0.1% and 0.4% FWBP groups, respectively. The hepatopancreatic total superoxide dismutase activity was higher in the 0.1% FWBP group than in the control. The malondialdehyde levels decreased significantly in the 0.2% and 0.4% groups. The intestinal mRNA levels of the LZM-C and IL-10 genes were significantly higher in the 0.2% than in the 0.4% FWBP group; TNF-α was significantly upregulated in the 0.1% group. The gene expression in the kidneys did not differ significantly among the treatments, except for a significant increase in the IL-10 expression in the 0.1% treatment. Significantly elevated expression of LZM-C in 0.2% group and IL-10 in 0.1% group was observed in the spleens. TNF-α and IL-1β were significantly downregulated in the 0.4% group. These results suggest that FWBPs could be used as immunostimulant feed additives in common carp cultures.
 
Top-cited authors
Vishwanath Patil
Gjermund Vogt
  • Eurofins Food & Feed Testing Norway AS
Hans R. Gislerød
  • Norwegian University of Life Sciences (NMBU)
Torsten Källqvist
  • Norwegian Institute for Water Research
Stefan Denev
  • Trakia University