According to the UN Food and Agriculture Organization, aquaculture is growing more rapidly than all other animal food-production sectors (www.fao.org). Its contribution to global supplies of several species of fish, crustaceans and mollusks increased from 3.9% of total production by weight in 1970 to 33% in 2005. It has been estimated that fisheries and aquaculture supplied the world with about 110 million metric tons of food fish per year (FAO, State of World Fisheries and Aquaculture 2010.), providing a per capita supply of 16.7 kg (live weight equivalent). Of this supply, 47% is derived from aquaculture production. However, this production is hampered by unpredictable mortalities that may be due to negative interactions between fish and pathogenic bacteria. To solve this problem, farmers frequently use antibiotic compounds to treat bacterial diseases (Cabello 2006).
ABSTRACT Water hyacinth (hereafter, WH) is known as ‘the green devil' and becomes a threat to the fishing community whose livelihood solely relies on fishing activities. Although there are immense assessment studies related to WH, the real causal impact of this invasive weed on the fishing community has not yet been properly quantified. In filling this gap, the present study aimed to estimate the causal effect of WH on the net fishing income, technical efficiency level, income poverty and poverty gap around Lake Tana, Ethiopia. In addressing these, the study used about 593 randomly drawn fishers from both infested and non‐infested areas. Propensity score matching (PSM) and the ‘doubly robust' inverse probability‐weighted regression adjustment (IPWRA) methods were employed to estimate the average treatment effects of WH. In addition, heterogeneous treatment effect analysis was conducted to identify fishers who are most impacted by WH, given observable characteristics. The study provides adequate evidence that WH has a significant and negative impact on the welfare of fishers. However, the degree of causal effects on the outcomes of interest is not homogenous among fishers from infested areas. The results from the treatment heterogeneity reveal that the impact of WH is higher for artisanal and less experienced fishers than for their counterparts. These findings suggest that eradication (if possible) or control of WH in the study area could significantly contribute to the poverty reduction endeavours within the fishing community.
Global trade in marine and aquaculture fishery products reached $186 billion by 2022, reflecting a 63% increase over the past decade and contributing to economic growth and supporting Sustainable Development Goals 1, 2 and 14. Tanzania's exports of processed small pelagic products surged to $3.9 million in 2023–2024, driven by rising demand in African markets, while exports of crustacean products to the global north reached $11.8 million. Despite the sector's contribution to economic growth and livelihoods, the influence of marine trade on microeconomic development and income distribution among actors remains underexplored. This study fills this gap by examining the distribution of trade benefits and associated inequality in Tanzania's seafood trade. The study was conducted at four landing sites in three coastal districts of Tanzania. The net income distribution approach, Lorenz concentration curve and Gini coefficient were used to analyse income distribution and inequality in seafood trade. Findings showed a significant gap in income and costs across actors in the small pelagic and crustacean value chains, with traders earning higher income than other actors. The Gini coefficients for the small pelagic and crustacean chains were 0.58 and 0.44, respectively, signifying greater income inequality among traders (aggregators and wholesalers), processors and fishers in both chains. The study recommends improving market infrastructure and institutionalising pre‐trade agreements to ensure a fair distribution of benefits within the sector.
This study evaluated the impacts of dietary Alpinia oxyphylla extract (AO) on growth, muscle composition, antioxidant status, immunity, and ammonia resistance of juvenile ivory shell (Babylonia areolata). Six experimental diets (AO1, AO2, AO3, AO4, AO5, and AO6) with varying AO levels (0, 1, 2, 4, 6, and 10 g/kg diet) were fed to the ivory shell for 8 weeks. The weight gain rate and specific growth rate were higher in AO3 and AO4 groups. Muscle crude protein content was significantly higher in AO4 and AO5 groups, while crude lipid content significantly decreased in AO4 group compared to the control group. Superoxide dismutase (SOD) activity was increased in AO-fed B. areolata, with the highest values in the AO3 group. Catalase (CAT) activity was significantly increased in AO3, AO4, AO5, and AO6 groups. Total antioxidant capacity (T-AOC) was significantly higher and malondialdehyde (MDA) content was significantly lower, in AO3 and AO4 groups compared to the control group. The highest acid phosphatase (ACP) value was recorded in AO3, AO4, and AO5 groups, while alkaline phosphatase (AKP) activity was significantly higher in AO4, AO5, and AO6 groups compared to the control group. AO significantly induced the expression of SOD, GST, CYP450, ACP, and CYC in hepatopancreas. After ammonia stress, B. areolata fed with 2–4 g/kg AO showed a higher survival rate compared to the control group. These results suggest that dietary AO supplementation at 2.26 g/kg AO improves growth, muscle composition, immunity, and ammonia resistance in B. areolata.
Mojtaba Zabayeh Najafabadi, Hamid Mohammadiazarm, Mansour Torfi Mozanzadeh
et al.
A 135-day study was conducted to investigate the effects of dietary vitamin E on the reproductive performance of Arabian yellowfin seabream (Acanthopagrus arabicus) broodstock. The experimental design utilized a basal diet containing 50 % crude protein and 18 % crude fat, supplemented with different concentrations of vitamin E (0, 25, 50, 100, 250, 500, and 1000 mg/kg). A total of 294 broodstock were distributed in twenty-one cylindrical polyethylene tanks (1.5 m³ each), maintaining a balanced sex ratio (1:1) and a salinity level of 40.2 ± 0.22 g/l. The fish were fed the experimental diets twice daily before and during the spawning period. The results indicated that dietary vitamin E did not significantly influence growth parameters. However, higher levels of vitamin E were observed in the liver, gonadal tissue, and larvae as a result of increased dietary intake. Notably, supplementation with 250 mg/kg of vitamin E significantly enhanced relative fecundity, spawning frequency, fertilization rate, egg production, and larval survival rate. Furthermore, lipid peroxidation was reduced at this concentration. These findings suggest that dietary supplementation of 250 mg/kg vitamin E is optimal for improving the reproductive performance of Arabian yellowfin seabream.
Marta Caballero‐Huertas, Marc Canonne, Domoina Rakotomanana
et al.
Abstract One of the primary objectives in freshwater aquaculture is the search for sustainable systems based on agroecological intensification. In this context, the cultivation of local species is decisive, although requiring the identification of new candidates. Malagasy aquaculture is an example of the development of such an approach. We aimed to deepen the knowledge of the biology of the Paratilapia sp., specifically, their reproductive traits and zootechnical aspects, with special emphasis on the juvenile stages. The information provided has interest for its commercial production and the species conservation, as populations are subjected to overexploitation and habitat degradation. This study is a consolidated report on morphological characteristics, sexual dimorphism, reproductive biology, and early developmental ontogeny. The main results suggested a marked sexual dimorphism, as well as greater growth of males compared with females. Aggressive behavior between males was observed before pair formation. Generally, female and males provided protection until fry are independent. Females produced 2756 ± 598 eggs per spawn on average (gonadosomatic index = 4.6%), with a reproductive frequency of one to two spawns. Despite the need to improve breeding protocols, this work represents a breakthrough in producing a local freshwater species of potential interest.
Prathap Kumar Jharapla, Nicolas Leconte, Zhiren He
et al.
We demonstrate a finite twist-angle stabilization mechanism in lattice-mismatched 2D heterobilayers, which results from the geometric alignment between the flake edges and its moire pattern. Using atomistic simulations of graphene on hexagonal boron nitride flakes with diameters of up to $\sim 2500$Å, we identify robust metastable angles at $\sim 0.61^\circ$ for armchair and $\sim1.89^\circ$ for zigzag-edged flakes, tunable via in-plane heterostrain. This locking mechanism, which relies on energy barriers that are an order of magnitude larger than those of nearby metastable twist angles, provides a geometric route to precision twist-angle control of two-dimensional heterostructures and to understand the self-orientation of macroscopic flakes.
The immense production of fishmeal and fish oil is dramatically intensifying the severe state of pelagic fisheries overexploitation. The latter in conjunction with the increasing demand for low‐cost protein‐rich food supply prompt aquaculture to employ new practice. Several novel dietary ingredients are currently under evaluation for potential incorporation in aquafeeds in an effort to shift the aquaculture sector toward a more sustainable and economic production. The present review aims to summarize the existing findings regarding the effects of studied alternatives to fishmeal and fish oil on the most valuable and commercially produced marine (Sparus aurata and Dicentrarchus labrax) and freshwater (Salmo salar and Oncorhynchus mykiss) finfish species in European aquaculture. Alternative protein sources, including macroalage (marine plants), krill (marine fishery), insects (terrestrial), terrestrial animal by‐products (processed/rendered), and single cell ingredient (biotechnology), are discussed for their efficiency in promoting the growth and the welfare of both fry and adult cultured finfish species. Applicability of these ingredients is reviewed in terms of nutrient composition, dietary inclusion level, performance output, digestibility, and health benefits. In addition, a meta‐analysis was conducted based on data from peer‐reviewed scientific publications in order to assess whether novel ingredients meet the dietary protein (amino acid) and lipid requirements of finfishes. Aquafeed reformulation strategies should ensure the recommended daily nutritional requirements and additionally indicate the meta‐analysis alternatives, such as microalgae, which are deficient in essential amino acids. The sustainable expansion of aquaculture is on the horizon, but which novel ingredients may be regarded as the key drivers to its establishment?
Constructed-wetlands, biofilms, and sedimentation are among biological filters used in mariculture wastewater treatments, however, their impacts on the distribution of benthic microbial community and inorganic-nutrient fluxes have not been fully explored. This study applied 16 S rRNA high-throughput sequencing technology to investigate the microbial community distribution and their impacts on nutrient fluxes in mariculture biofilters system. Results showed that bacterial community compositions were significantly different in the constructed-wetland and biofilm treatments (p < 0.05) relative to sedimentation. The composition of the 16 S rRNA genes among the treatments were enriched with Proteobacteria (73%), Bacteroidetes (69%), Firmicutes (62%), and Flavobacteria (61%) in Biofilm compared to Proteobacteria (53%), Bacteroidetes (39%), Firmicutes (32%), and Flavobacteria (21%) in constructed wetlands. NMDS analysis showed that bacterial composition in constructed-wetland and biofilms clustered separately compared to sedimentation treatment. Functional-Annotation-of-Prokaryotic-Taxa analysis indicated that the proportions of sediment-microbial-functional groups (aerobic-chemoheterotrophy, chemoheterotrophy, and nitrate-ammonification) were 47% in the constructed-wetland, 32% in biofilm and 13% in sedimentation system. Benthic-nutrient fluxes for phosphate, ammonium, nitrite, nitrate and sediment oxygen consumption differed markedly among the treatments (p < 0.05). Canonical correspondence analysis indicated constructed-wetland had the strongest association between biogeochemical contents and the bacterial community relative to other treatments. This study suggests that the mariculture wastewater biofilters promoted microbial community distributions, sediment bacterial functional-groups including chemoheterotrophy, aerobic-chemoheterotrophy, denitrification, and nitrification and interactions with nutrient fluxes which was more pronounced in the constructed-wetland system.
In this note, we improve Nikulin's inequality in the case of right-angled hyperbolic polyhedra. The new inequality allows to give much shorter proofs of the known dimension bounds. We also improve Nonaka's lower bound on the number of ideal vertices for right-angled hyperbolic polyhedra.
In this article, we discuss the equality of two inner products on a vector space. Particularly, we look at some geometric properties that are given to a vector space by an inner product namely, length and angle, and we ask under what conditions on these geometric properties do two inner products coincide. Some parts of this article can be found as exercise problems in various books on geometry. We give a slight generalization to these exercises and exposit the rigid nature of angles in an inner product space.
Nguyễn Ngọc Quyến, Getachew Worku Alebachew, Balázs Kucska
et al.
In this study, the inseminated sperm method (sperm injection into the ovarian lobe in externally fertilised fish species) combined with hormonal induction was conducted as a novel method to produce hybrid catfish by induced/tank spawning. In the treated group, four Clarias gariepinus ♀ were inseminated equally with Heterobranchus longifilis sperm in the ovaries at a dosage of 1 mL/fish and then introduced into four spawning cages together with four C. gariepinus ♂. Ovulation was induced by extracted carp pituitary (CPE) hormonal administration (♀; 5 mg CPE/BW kg). The hybridization rate was determined on the basis of morphological markers to distinguish between pure African catfish and hybrid in juvenile stage. A control experiment was also designed to determine this and to explore possible interactions between the two genotypes. In the control group, in vitro fertilisation (IVF) was used to produce pure progeny of C. gariepinus and the hybrid progeny between C. gariepinus ♀ × H. longifilis ♂. Exogenously fed larvae from each treatment were raised and compared after 28 days in four replications; the mixed group contained 50 C. gariepinus and 50 hybrids from IVF grown together, while every 100 larvae from each cage spawning pair were grown separately. The hybridisation rate determined based on morphological traits was 98.11 ± 1.59 (mean ± S.D.) for 28-day-old reared offspring. There were no significant differences (P > 0.05) in survival rate (%) between C. gariepinus (45.79 ± 6.82 %) and the hybrid (54.21 ± 6.82 %) in the control treatment; therefore, neither genotype had a negative effect on the other during the rearing period. From this result, we supposed that the hybridisation rate was also over 95 % at the moment of fertilisation. This approach could be an alternative method for producing hybrid catfish or other fish species without in vitro fertilisation.
A universal group is a subgroup of the group of type preserving automorphisms of a right-angled building and hence associated to this building. A question is then if this universal group can act chamber-transitively and with compact open stabilisers on a different right-angled building of the same type. We answer this question and define two universal groups associated to different right-angled buildings which are isomorphic as topological groups.
Planar/flat configurations of fixed-angle chains and trees are well studied in the context of polymer science, molecular biology, and puzzles. In this paper, we focus on a simple type of fixed-angle linkage: every edge has unit length (equilateral), and each joint has a fixed angle of $90^\circ$ (orthogonal) or $180^\circ$ (straight). When the linkage forms a path (open chain), it always has a planar configuration, namely the zig-zag which alternating the $90^\circ$ angles between left and right turns. But when the linkage forms a cycle (closed chain), or is forced to lie in a box of fixed size, we prove that the flattening problem -- deciding whether there is a planar noncrossing configuration -- is strongly NP-complete. Back to open chains, we turn to the Hydrophobic-Hydrophilic (HP) model of protein folding, where each vertex is labeled H or P, and the goal is to find a folding that maximizes the number of H-H adjacencies. In the well-studied HP model, the joint angles are not fixed. We introduce and analyze the fixed-angle HP model, which is motivated by real-world proteins. We prove strong NP-completeness of finding a planar noncrossing configuration of a fixed-angle orthogonal equilateral open chain with the most H--H adjacencies, even if the chain has only two H vertices. (Effectively, this lets us force the chain to be closed.)
The determinations of the Cabibbo angle from kaon, pion, $D$ and tau decays disagree with the one from super-allowed beta decays. The resulting $\approx 3\,σ$ deficit in first row (but also first column) CKM unitarity is known as the Cabibbo angle anomaly (CAA). Determining $V_{ud}$ from beta decays requires knowledge of the Fermi constant $G_F$, usually extracted from muon decay. However, because new physics might also affect muon decay, and thus the determination of the Fermi constant, an interesting interplay with the global electroweak fit arises where $G_F$ is a crucial input. In these proceedings we review the CAA and its different interpretations in terms of physics beyond the SM, first discussing the corresponding effect in the effective field theory and then using (simplified) models.
Domenico Fiorini, Miguel Alfonso Mendez, Alessia Simonini
et al.
The contact angle between a gas-liquid interface and a solid surface is a function of the dynamic conditions of the contact line. Classic steady correlations link the contact angle to the contact line velocity. However, it is not clear whether they hold in presence of inertia and in the case of perfect wetting fluids. We analyze the shape of a liquid interface and the corresponding contact angle in accelerating conditions for two different fluids, i.e. HFE7200 (perfect wetting) and demineralized water. The set-up consists of a U-shaped quasi-capillary tube in which the liquid column oscillates in response to a pressure step on one of the two sides. We obtained the evolution of the interface shape from high-speed back-light visualization, and we fit interface models to the experimental data to estimate the contributions of all the governing forces and the contact angle. Traditional interface models fail to predict the interface shape and its contact angle at large interface and contact line accelerations. We propose a new model to account for the acceleration, and we discuss its impact on the measurement of the transient contact angle.
California halibut (CH; Paralichthys californicus ) is a highly valued species that supports a commercial and recreational fishery along the Pacific coast of the United States. This species is considered a promising aquaculture candidate in California, with interest for both food production and stock replenish-ment. Culture of CH has been done on a small scale, showing that it is technologically feasible to rear this species commercially. Broodstock maturation and egg production can be accomplished without hormone therapy. Survival from egg to juvenile (~50 dph) can be as high as 30%. Juvenile growout to market size has been done on a limited basis, and it takes 3 years to reach a market size of 1 kg. There is a live market for CH in California and it is currently being supplemented by the importation of Paralichthys olivaceus . The known disease agents affecting CH are ectoparasites (i.e., Trichodina sp ), endoparasites (i.e., Anisakis sp .), and bacterial agents (i.e., Pseudomonas sp .). While culture of this species is technologically feasible, research still needs to be done in certain areas in order to realize commercial readiness. These areas include: nutrition, selective breeding, of all female populations; improved pigmentation; and developing methods for disease prevention and control.