Affine geometry is usually regarded as a framework in which metric notions such as distance and angle are absent. However, just as projective geometry produces various metric geometries by introducing additional structures on the line at infinity, affine geometry can also serve as a natural basis for an angular geometry once certain directions at infinity are fixed. In this paper we introduce an affine angle determined by two fixed directions on the line at infinity and defined via an area cross ratio. This quantity is invariant under affine transformations preserving the chosen directions. We show that the locus of points from which a fixed segment is seen under a constant affine angle is a hyperbola whose asymptotes are parallel to the chosen directions. This provides an affine analogue of the classical fact that in Euclidean geometry the isoptic curve of a segment is a circle. Furthermore, we establish that this angle arises as a parabolic degeneration of the Cayley--Klein angle, and that the same quantity naturally appears in a power theorem associated with hyperbolas. These results provide a unified perspective linking affine angles, isoptic hyperbolas, and hyperbolic power through the area cross ratio.
ABSTRACT Using histology to examine ovarian structures in Pacific capelin for the first time, we found biological evidence that captive, age‐1, female Pacific capelin Mallotus catervarius are capable of iteroparity (41% of mature females). Evidence of the potential to spawn over multiple years included more than one oocyte cohort, including primary growth and vitellogenic oocytes in maturing fish, or primary growth and post ovulatory follicles in spent fish.The data on iteroparity rates provide a better understanding of how fish might respond to variable or extreme environments, as a population with mixed or flexible parities may have more flexibility in spawning frequency, reproductive output, and survival.
In this work, we introduce a new geometry based on the difference angle, an angle defined as the difference of slopes of two lines, together with an axiomatic system for angles. This framework provides a constructive approach to the fundamental question ``What is an angle?'', and shows that an angle can be defined independently of circles or rotations, as a primary geometric notion. Within this geometry, one can define difference-angle triangles, norms, bisectors, perpendiculars, and inner products. Several characteristic properties not seen in existing geometries emerge, together with behaviors analogous to those in Euclidean geometry: the triangle inequality always holds with equality, the sum of the interior angles of any triangle is $0$, and a Miquel point exists even for parabolas. In particular, the concurrency of the parabolic Miquel configuration was suggested by Weiss and Odehnal, and our main theorem provides the first explicit and rigorous confirmation of this assertion. We also point out that many classical Euclidean configurations (including Brocard-type configurations) naturally reappear in the setting of difference-angle geometry. These results indicate that difference-angle geometry is a promising candidate for a ``Fourth Geometry'' following the Euclidean, hyperbolic, and elliptic geometries.
Petra Camilla Lindholm‐Lehto, Kalle Sinisalo, Jani Tapio Pulkkinen
et al.
ABSTRACT Partial recirculating aquaculture systems (PRASs) aim for combining the benefits of flow‐through systems (water use of approximately 50,000 L kg −1 feed) and recirculating aquaculture systems (RASs, 500–1000 L kg −1 feed). While water quality is usually excellent in flow‐through systems, large volumes of water of good quality are required. In RAS, investment and production costs can be high, and due to the microbial actions typically occurring in RAS, off‐flavours can occur and accumulate in fish flesh. Here, an evaluation between three water renewal rates (4000, 2000 and 1000 L kg −1 feed) of a PRAS was performed. In the experiment, rainbow trout Oncorhynchus mykiss was reared in similar PRASs. Fish growth and a variety of water quality parameters were monitored, including 14 off‐flavour compounds in the recirculating water, in the inlet water and in fish flesh. The results did not show statistical differences in feed conversion ratio (FCR), specific growth rate (SGR), and mortality between water renewal of 2000 and 4000 L kg −1 feed, while reduced growth was observed at 1000 L kg −1 feed. Additionally, total ammonia nitrogen (TAN) and nitrite–nitrogen (NO 2 ─N) increased at reduced water renewal rates of 1000 and 2000 L kg −1 feed ( p < 0.005). Concentrations of off‐flavours remained low in the circulating water, but in the circulating water and in fish flesh, they were above the known sensory thresholds at 1000 L kg −1 . Overall, the results suggest that 2000 L kg −1 feed offers good fish growth, feed use and low mortality without the unwanted off‐flavour accumulation.
Boke Christopher Magesi, Augustus Sammy Muluvi, Hillary Kiplangat Bett
ABSTRACTThe impact of climate change on aquaculture threatens global food security, disrupting fish productivity and sector sustainability. Climate‐smart aquaculture (CSAq) offers a viable strategy to mitigate these challenges, particularly during droughts, through practices such as adjusted fish stocking, dam lining, tanks, boreholes and pond covers. Despite their benefits, adoption among smallholder fish farmers in Kakamega County remains low. This study examines factors influencing CSAq adoption among 220 smallholder fish farmers, selected through a multistage sampling technique. A multivariate probit model was employed to analyse the data. Results indicate that farming experience, gender, education level, age, land ownership, household size, extension service frequency and access to CSAq training significantly influence the adoption of these practices. Farmers with more experience, higher education and greater access to training and extension services were more likely to implement CSAq techniques. The findings highlight the need for targeted interventions to enhance CSAq adoption. Policies promoting knowledge dissemination, improved farmer training and increased access to extension services are crucial for strengthening climate resilience in aquaculture. Investment in these areas will encourage smallholder farmers to adopt CSAq practices, ensuring sustainable fish production and long‐term sector stability amid climate change challenges.
Aquaculture provides an important and expanding source of protein rich and healthy food to the world. However, to minimize environmental harm from aquaculture, interactions with wild fish communities need to be thoroughly assessed. Here, we characterize the existing knowledge pertaining to such interactions, exemplified with Atlantic salmon (Salmo salar) farming in open net pens along the Norwegian coast and potential consequences for wild Atlantic cod (Gadus morhua) populations. Importantly, the wild cod fishery also provides a protein rich, high quality food source with high economic value. We identify seven risk sources that may affect behaviour, physiology, and survival in wild cod. Of particular importance is the large amount of waste feed that causes wild fish to aggregate around farms, thereby altering a multitude of ecological interactions including predation and disease transmission. Moreover, altered food quality in pellets may alter physiological processes and cause mortality to vulnerable life‐stages in wild cod. More research is needed on mechanisms and thresholds for harm. As the most important cod fisheries are found in northern Norway, where climate change also is rapid, we expect stronger and potentially more harmful interactions between fish farming and wild cod fisheries as aquaculture continues to expand. We hope that our analysis will inspire further research, on farmed salmon and wild cod interactions, but also on aquaculture and wild fish interactions in general. Such research is fundamental for the development of management systems that can reduce the impact of aquaculture on fisheries and the environment.
Aquaculture allows food production, bringing important social and economic benefits that result in high nutritional value and accessible costs for the population. Mexico has a great diversity of native species with great potential for this activity, such as the Mayan cichlid, Mayaheros urophthalmus. The present bibliographic review was carried out in Google Scholar, libraries and the institutional repository of the Universidad Juárez Autónoma de Tabasco on the advances in the knowledge of the biology, fishery and aquaculture potential of the mojarra castarrica. Among the results, it was found that 60% of them are focused on the biology and ecology of the species, highlighting that it is an omnivorous fish with a carnivorous tendency that normally feeds on fish and invertebrates, presents an important fecundity, reproducing several times during the warm months. The fishery status of the beaver is uncertain; at present, catches are reported as encompassing all cichlids, so there is no basis to indicate its status. However, fishermen report low catches. In aquaculture, there are advances in culture, nutrition and biotechnological aspects, with larval culture being identified as one of the critical phases of development. In the grow-out stage, it can be cultivated in cages, geomembranes or earthen ponds, using a feed containing between 32 and 45% protein. Progress has been made in nutrition, but there is still no feed specifically designed for this species. Many more studies are required to determine its fishing and aquaculture potential.
Dilip Kumar Maity, Christopher Wagstaff, Sandip Dighe
et al.
This research explores the modulation of Rayleigh-Plateau Instability (RPI) by adjusting the orientation angle and eccentricity of a wire within a nozzle. We demonstrate that both the angle and eccentricity significantly influence the RPI regimes. They both also influence characteristics, such as velocity, wavelength, and droplet volume. Notably, when wires are both angled and eccentric, the effect of angle prevails. Our approach includes an empirical scaling analysis, comparing gravity, surface tension, and viscosity forces on a single bead, yielding a unified empirical viscous force law, enhancing understanding of RP regime dynamics. This new framework enriches our understanding of the forces at play in RPI and provides practical insights into the manipulation of fluid dynamics in industrial applications.
Quantitative real-time polymerase chain reaction (qRT-PCR) is one of the most widely used molecular techniques, which allows the detection and quantification of gene expression due to its high sensitivity, specificity, and reproducibility. To increase the reliability of the experimental results, internal reference genes are used to normalize the data. However, previous studies have shown that the stability of internal reference genes is influenced by experimental conditions and interspecies variations, and no universal internal reference genes have been identified for all species. Therefore, suitable internal reference genes must be identified for each species. The Hong Kong catfish (Clarias fuscus) has strong adaptability, high nutritional value, and tender flesh, and it was first introduced to large-scale aquaculture in the Guangdong and Guangxi provinces in the early 1970s. Currently, it is a key aquaculture species in the Guangdong-Guangxi region and one of the freshwater economic fish cultured in southern China. Thus, fairly extensive molecular biology and genetics studies of C. fuscus have been conducted, which in turn has increased the demand for quantitative gene expression analysis by qRT-PCR in these animals. Consequently, there is a growing demand for quantitative gene expression analysis by qRT-PCR in C. fuscus for various molecular biology and genetics studies. However, few studies have evaluated the internal reference genes for this species. Therefore, we aimed to identify suitable internal reference genes in different tissues and different stages of gonadal development of males and females to provide the necessary tools to support subsequent gene expression pattern analysis.In this study, we examined the expression of 13 internal reference genes (actb1, actb2, ef1a, eef1b2, rpl13a, rpl13, ccdc124, cfl1, nm23, eif3g, rap1a, ikbkg, and ywhab) in different stages of gonadal development and different tissues of adult fish of C. fuscus. We used four software tools, namely BestKeeper, GeNorm, NormFinder, and RefFinder, to evaluate the expression stability of the internal reference genes. BestKeeper software evaluates the stability of internal reference genes by calculating the standard deviation (SD) and coefficient of variation (CV). The results showed that in different tissues of adult fish, the stability ranking of these genes was as follows: actb1 > actb2 =ef1a > rpl13 > ywhab > eef1b2 > rpl13a > nm23 > eif3g > ccdc124 > rap1a > cfl1 > ikbkg. In different stages of male and female gonadal development, the stability ranking of these genes was as follows: actb2 > rpl13 > ef1a > rpl13a > actb1 > ywhab > cfl1 > rap1a > eef1b2 > eif3g > ccdc124 > ikbkg > nm23. NormFinder suggested that the best stability ranking was as follows: actb2=rpl13 > actb1 > rpl13a > ywhab > nm23 > rap1a > cfl1 > eif3g > ef1a > ccdc124 > ikbkg > eef1b2 in different tissues of adult fish and actb2=actb1 > rpl13 > ef1a > rpl13a > cfl1 > ywhab > rap1a > nm23 > eif3g > ccdc124 > ikbkg > eef1b2 in different stages of male and female gonadal development. The geNorm screens for the most stable internal reference genes by comparing the stability value (M) of each internal reference gene. It indicated that the final stability ranking in different tissues was actb2=rpl13 > rpl13a > actb1 > ef1a > ccdc124 > ywhab > rap1a > eif3g > nm23 > eef1b2 > ikbkg > cfl1, and actb1=rpl13 > actb2 > ef1a > rpl13a > cfl1 > ywhab > ccdc124 > rap1a > eif3g > nm23 > eef1b2 > ikbkg in different stages of male and female gonadal development. Finally, RefFinder analysis integrated the results of the other three software tools and showed that the comprehensive stability ranking of each gene in different tissues was actb2 > rpl13 > cfl1 > rap1a > ef1a > rpl13a > ikbkg > eif3g > nm23 > actb1 > eef1b2 > ywhab > ccdc124. In different stages of male and female gonadal development, the comprehensive stability ranking was actb2 > rpl13 > actb1 > cfl1 > rap1a > ef1a > rpl13a > ikbkg > eif3g > nm23 > eef1b2 > ywhab > ccdc124. Given this, we can conclude that actb2 is the best internal reference gene for C. fuscus. To validate the accuracy of the results, we selected actb2 and rpl13 as internal reference genes and compared their expression levels with those of four genes (zp3, atp2b3, slc13a5 and parp8) from transcriptome RNA-seq data. The fold changes in the expression levels were closer to the transcriptome data when using actb2 than when using rpl13, indicating that actb2 is more stable than rpl13.This study demonstrated that actb2 showed good stability among the 13 internal reference genes and could be used as an internal reference gene for different stages of gonadal development and different tissues of adult fish in C. fuscus. The results can provide technical support for the subsequent research on the functional gene expression patterns of C. fuscus and are expected to be applicable to other catfish species.
The Pacific white shrimp (Litopenaeus vannamei) is the most commercially-farmed shrimp species globally and is of significant ecological and economic importance. Here we report a high-quality genome assembly of L. vannamei using PacBio reads and Hi-C data. The assembly spans 1.87 Gb with scaffold N50 of 39.7 Mb and 87% of estimated genome size is assigned to 44 pseudochromosomes. The genome contains 24,861 protein-coding genes and a high proportion of transposable elements (64.33%). Significant expansion of gene families was observed in the genome related to locomotion, vision, and neural transmission, including via expansion of actin, myosin, rhodopsin, and neurotransmitter-gated ion-channel ligand binding domain genes, potentially revealing mechanisms underlying their evolved benthic adaptations. The genome assembly of L. vannamei provides valuable resources for future genetic research, breeding, and improvement of aquaculture traits, and will facilitate the research of genetic changes during evolution.
Claudio A. Álvarez, Valentina Córdova-Alarcón, Natalia Godoy Alfaro
et al.
In the north of Chile, several projects propose to promote the diversification of national aquaculture with native fish species. However, one of the expected impacts of climate change on the Chilean coasts is an increase in the intensity and frequency of hypoxia events. Therefore, it can become one of the main problems for fish aquaculture in farming facilities. Two species of Chilean diversification programs are Seriola lalandi and Seriolella violacea, which have different habitats and may have different oxygen requirements. Thus, this work aimed to evaluate the variations in oxygen consumption rates in 10 month-old juveniles of both fish species and to determine the presence of tolerant and non-tolerant individuals at low dissolved oxygen (DO) availability. A simulation of an acute hypoxia event by loss-of-equilibrium (LOEhyp) experiments allowed us to classify tolerant and non-tolerant fish. Then, individual oxygen consumption rates were measured, and the resting metabolic rate (RMR) and the maximum metabolic rate (MMR) for hypoxia-tolerant and non-tolerant juveniles were obtained. The results reveal that S. lalandi juveniles have a higher oxygen demand than S. violacea, the first presenting a significantly higher metabolic rate and locomotor activity. Furthermore, the blood parameters suggest that triglyceride metabolism could be used as alternative energy sources by S. violacea during hypoxic-environments. The juveniles classified as tolerant from both species have a lower RMR than non-tolerant fish, which is associated with reduction in their locomotor activity evidenced by decreasing tail beat frequency. Furthermore, the hypoxia-tolerant juveniles also reached a significantly higher size than non-tolerant fish. This work provides valuable results for the future S. lalandi and S. violacea industries, considering the effects of low OD in the farms. Likewise, the first evidence of the hypoxia adaptive mechanism of native fish are presented, providing scientific support for their aquaculture in Chile.
In the brackish lagoons located in coastal inshore areas around the German island of Rügen, pike Esox lucius is a highly sought after target species for recreational fishers. Yet, the pike stock is currently in decline, and conflicts with other user groups (specifically commercial fishers) have emerged. To inform future fisheries management, an improved understanding of the human dimensions of recreational fishers, including their preferences for catch outcomes and regulations, is relevant. Our objective was to better understand how German recreational pike fishers react to different types of harvest regulations in trade-off with risky or ambiguous catch outcomes for pike and other predators in the lagoon fishery. We conducted an online survey including choice experiments for angling experiences that differed in seven attributes. Data were analyzed using a latent class model. We found four distinct angler types differentiating resident and tourists and dependency on pike. Specifically, we identified a highly involved pike tourist (42 % average probability), a consumptive, generalist tourist angler type (18 %), a highly specialized local trophy pike angler type that readily engaged in catch-and-release (12 %), and a local generalist angler that also benefitted from the catch of other predators than pike (18 %). Despite heterogeneity in preferences, all four angler types generally accepted more restrictive regulations for pike removals than currently in place, and dispreferred low catch probabilities compared to catch ambiguity. Most angler types also revealed diminishing marginal utility returns for catch rates, where the first three pike in a day provide utility, while the marginal benefits of catch rate decrease to zero for more than three pike per day. Angler types varied more in their preferences for trophy pike, the general attractiveness of the pike as a target and the utility derived from catching fish other than pike. Particularly the more specialized angler types focused on size rather than catch rate. Despite preference heterogeneity, focusing management attention on maintaining a sufficiently high catch rate and increasing the number of trophy pike in the stock seems to satisfy the expectations of most angler types. To achieve such outcomes, the anglers of all types would overwhelmingly support implementing harvest slots of 50 – 85 cm that allow both small and large fish to be released (rather than the current minimum-length limit of 50 cm), and accept reductions in the daily bag limit to 1 pike per day (relative to the current of 3 pike per day). Implementing these policy measures would unlikely generate substantial conflict with anglers represented in our survey.
Aquaculture and fisheries are salient flourishing sectors in the world but their sustainability is often afflicted by several pathogenic diseases. Among all the pathogenic diseases of fish, parasitic diseases are found to be a major cause of concern. Argulosis is one of the dominant parasitic problems encountered in Indian aquaculture practices. Argulus siamensis is the most prevalent argulid species harming the Indian major carp species including Labeo rohita. The major carps respond to parasitic infestation by elevating various immune relevant genes. The therapeutic chemicals, synthetic drugs and other plant extracts have made a progress in the fight against argulosis. However, there is no effective vaccine and drugs are available for this disease. Thus, designing efficient, cost-effective and eco-friendly control and treatment strategies for argulosis is presently needed. Keeping the aforementioned facts in mind, the current review elaborated the immunological interaction between A. siamensis and L. rohita, available combat tactics, highlighted the already identified vaccine candidates to design effective control measures and illustrated the use of omics technology in future to combat argulosis.
Rita N. Nairuti, S. N. Musyoka, Mourine J. Yegon
et al.
Aquaculture plays a major role in curbing malnutrition and food insecurity. Nonetheless, aquaculture sustainability is threatened by expensive fish feeds due to the overreliance on fish meal (FM) as the main source of protein. Fish meal is not only expensive but also scarce due to declining capture fisheries and competition from other animal feed producers. This has prompted research on potential FM replacers, amongst them the black soldier fly (BSF) larvae (Hermetia illucens). The BSF larvae can effectively convert organic wastes into a potential valuable feed source, and its high nutritional content (crude protein of up to 64% dry matter) is vital for fish feed formulation. Nevertheless, there are no documented studies on the complete replacement of FM in the diets of fish using BSF larvae. Therefore, the current study reviewed 107 research publications related to BSF larvae vis-a-visfish feeds production to build capacity for existing theories, identify gaps, and suggest new and further research directions, based on the previous studies available in the area of larvae production and utilization in aquaculture nutrition. The study results are expected to help farmers make an informed decision on how to reduce the cost of fish production, increase yields, thus promoting food security, livelihoods, and ecological balance.
Antibacterial activity of essential plant oils ex. orange, cinnamon, and ginger in normal nano-emulsion forms against potato bacterial wilt disease caused by Ralstonia solanacearum was screened in vitro and in vivo. All treatments revealed inhibitory effects in vitro on growth of R. solanacearum compared to the control treatment. In this respect, 0.05% ginger nano-emulsion oil (GIN-NE) increased the bacterial inhibition zone to 18.5 mm, followed by cinnamon essential oil ex. CIN-NE and CIN-EO (15.5 and 11.5 mm, respectively) while, the inhibition zone of bacterial growth recorded the greatest inhibition of 22.0 mm followed by 21.0 mm in reaction to 0.10% cinnamon nano-emulsion oil (CIN-NE) and ginger nano-emulsion (GIN- NE) oil comparing with control treatments. The bacterial inhibition zone of R. solanacearum was inhibited to 27.5, 25.8, and 21.5 mm in response to 0.20% GIN-NE, CIN-NE, and CIN-EO, respectively. Applying 0.20% concentration of each tested essential plant oil as foliar spray on Cara and Spunta cvs. reduced disease severity index % in comparison to control. All tested treatments decreased bacterial wilt disease assessment than control treatment. The treatment effect on the Spunta cultivar was more effective in decreasing disease severity index % of bacterial wilt disease than the Cara cultivar. All tested treatments increased potato yield. Relative expression profiles of Serine protease, glutathione S-transferase, catalase, and peroxidase genes in Cara and Spunta cultivars after inoculation with R. solanacearum showed positive transcriptome alterations in response to essential oils at 0.20% concentrations in normal and nano-emulsion form in comparison to the positive control.