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Background: Some diet additives have become alternatives to achieve higher yields within the productively sustainable, organic, and ecological margins. Hence, nutrients and microorganisms can be added to the diet for fish immunity improvements, by using the nutrients in the feed, which lead to a positive animal performance. Accordingly, the aim of this paper was to gather information related to the utilization of additives as immunostimulant in tilapia (Oreochromis ssp.), and their physiological performance in the body. Development: Many of these immunostimulants are microorganisms or habitual nutrients in the diet, such as polysaccharides, proteins or lipids, which at high concentrations are capable of creating a stimulating effect, speeding disease resistance through specific or unspecific mechanisms of immunological response, thus becoming primary prophylactic agents. Conclusions: The use of additives as immunostimulants helps prevent the occurrence of common diseases in tilapia culture, by modulating the intestinal system in the different species of genus Oreochromis, thus enhancing the unspecific immune response, and, in turn, some processes like individual growth, feeding efficiency, and stress tolerance can be favored. [ABSTRACT FROM AUTHOR]

Reproduction involves multiple complex behaviours, and the effects of familiarity on such social interactions are seldom described in fish. This is particularly true for sound production and communication within aggressive or non-aggressive context. This study explores the effects of a common garden rearing without parental care of two closely related cichlid species (Nile tilapia Oreochromis niloticus and blackchinned tilapia Sarotherodon melanotheron) on their sound production features and social interactions. After 9 months in common garden rearing, from embryonic stage to first maturity, sound production and associated behaviours were recorded on specimens of the two species in intraspecific and interspecific pairings. The authors found that fish were able to produce the same kind of sounds as those recorded in similar context for their parents. Drum sounds were associated to chasing, lateral attack and courtship in O. niloticus and only to fleeing or avoidance in S. melanotheron. Specific grunts were produced in chasing, after biting and in nest building by O. niloticus, and specific rolling sounds were associated to courtship in S. melanotheron. Sound production and behaviours were not correlated to sex steroid levels, but the number of sounds recorded in aggressive context was correlated to dominance in O. niloticus. The authors conclude that one generation of common garden rearing does not modify sound features, which remain specific and innate in the two cichlids. Despite the familiarity, O. niloticus remained dominant on S. melanotheron, but the aggressiveness between the two species decreased. [ABSTRACT FROM AUTHOR]

Fish species assemblage and selected environmental variables were monitored in Lake Volta from September 2014 to August 2016 to determine seasonal variability in species composition, catch and environmental variables that determine the structure of the fish community. A total of 1,557 individual fish belonging to 41 species, 25 genera and 13 families were recorded. The important fish species with respect to frequency of occurrence, abundance and weight, respectively, were as follows: Chrysichthys (100%; 43.03%; 17.93%), tilapias (100%; 28.97%; 17.86%), Alestes (100%; 14.13%; 32.10%) and Bagrus (91.67%; 5.65%; 12.80%) in that order. The composition of fish species and their temporal variation in experimental catches were similar to that of commercial catches. There were no significant differences (p > 0.05) in species abundance, weight and diversity indices between the dry and wet seasons. The modal class of length frequency distribution of the dominant species in the catch, Chrysichthys, reduced from 125 mm in 2006 to 95 mm in the current study indicating overfishing. Environmental variables considered showed little variation and within optimal ranges for fish survival and did not differ significantly between seasons. Canonical Correspondence Analysis showed that environmental variables explained 43.30% of the variation in species abundance with Lake water level, nitrite‐nitrogen and total dissolved solids being the main environmental factors influencing the structure of the fish community. [ABSTRACT FROM AUTHOR]

We have investigated gross pathology, physiological (steroid precursors) and toxicological responses (oxidative stress and phase II biotransformation) in relation to tissue contaminant burden in Tilapia species along the entire length (320 km) of Ogun River, Nigeria. The Ogun River is the longest and largest river in Southwestern Nigeria located along heavily industrialized cities and receives complex mixtures of effluents. A total of 1074 tilapias were collected from three sampling points (Abeokuta, Isheri and Ikorodu) and from an upstream control point (Igboho) and evaluated for gross pathological changes, hepatic transcript levels for oxidative stress and phase II biotransformation responses. Trace metal concentrations and POPs in muscle samples were analyzed using ICP-MS and GC-MS respectively. Evaluation of gross pathological changes showed a 50-, 33-, 17 and 0% prevalence of hepatic tumors at the Ikorodu, Abeokuta, Isheri and Igboho sites, respectively. Plasma concentrations of cholesterol and pregnenolone showed apparent significant decreases at downstream sites of the control point in both male and female fish (except for pregnenolone levels of male fish at Ikorodu). Inversely, gst, ugt -1, ZuCu-sod and sod significantly increased in fish collected from downstream sites, compared with the control site and these increases paralleled the significant increase in trace metal and POPs concentrations at these sites. PCA revealed a site related association between measured toxicological responses and contaminant burden, indicating a potential cause-and-effect relationship. Thus, the possible adaptation of Ogun River Tilapia species to contaminants may have significant consequences on cellular, physiological and biochemical processes regulating metabolism, growth, development and reproduction, and also have serious human health consequences, since the Ogun River is used for fisheries and domestic water supply for surrounding neighborhoods. [ABSTRACT FROM AUTHOR]

A major development in fishery science has been the Fulton's condition factor (CF) as a reliable physiological index of fish growth and health status (Fulton 1902). As a general rule, CF-value greater than 1 (> 1) should be regarded as an indicator for good growth and health. Therefore, exposure of fish to contaminants in the environment will be expected to produce a reduction in scope for growth, since energy for growth will be allocated to overcome stressful conditions. In the present study, we hypothesized that tilapia species from Ogun River (Nigeria) are experiencing severe contaminant-induced obesogen effects leading to high CF (≥ 2) in fish with pathological alterations. The environmental obesogen hypothesis has related the interaction between environmental pollutants and PPAR isoform activation In this respect, peroxisome proliferator-activated receptors (PPARs) and biotransformation responses in relation to contaminant burden were investigated in a total of 1074 specimens of Tilapias species ( Tilapia guineensis , Sarotherodon galileaus and Oreochromis niloticus ) collected from three areas with different degrees of anthropogenic contamination and from a putative control site along the Ogun River. Liver mRNA expression of cytochrome cyp1 isoforms (cyp1a, 1b and 1c) and PPAR isoforms ( ppar -α, β and γ) were analyzed using validated real-time PCR. Fish were also analyzed for CF and muscle contaminant burden (aliphatic and polycyclic aromatic hydrocarbons, organochlorine pesticides, and polychlorinated biphenyls). A significant increase in mRNA expression of cyp 1- and ppar isoforms was observed in fish from polluted areas, and these results paralleled data on PCBs and PAHs tissue concentrations. Further, cyp 1 isoforms showed clear sex-related differences, with higher mRNA expression in male fish than in females. Principal component analysis revealed a relationship between cyp 1 isoforms, ppar -α, β, PCBs and PAHs and these interactions may suggest a crosstalk between AhR- and PPARs mediated pathways on metabolic and energetic processes. The PCA biplot also highlighted a positive relationship between ppar -γ, body weight, total length and PAHs. The CF for fish from all the sites was ≥ 2 indicating that this parameter may not be a reliable index for evaluating fish growth and health condition, especially in wild fish population exposed to complex cocktails of environmental pollutants. [ABSTRACT FROM AUTHOR]

Edwardsiella tarda causes fish disease and great economic loss. However, metabolic strategy against the pathogen remains unexplored. In the present study, GC–MS based metabolomics was used to investigate the metabolic profile from tilapias infected by sublethal dose of E. tarda . The metabolic differences between the dying group and survival group allow the identification of key pathways and crucial metabolites during infections. More importantly, those metabolites may modulate the survival-related metabolome to enhance the anti-infective ability. Our data showed that tilapias generated two different strategies, survival-metabolome and death-metabolome, to encounter EIB202 infection, leading to differential outputs of the survival and dying. Glucose was the most crucial biomarker, which was upregulated and downregulated in the survival and dying groups, respectively. Exogenous glucose by injection or oral administration enhanced hosts' ability against EIB202 infection and increased the chances of survival. These findings highlight that host mounts the metabolic strategy to cope with bacterial infection, from which crucial biomarkers may be identified to enhance the metabolic strategy. [ABSTRACT FROM AUTHOR]

Cage culture of tilapia ( Oreochromis niloticus ) in large reservoirs is an emergent aquaculture practice in Brazil. Due to the availability of large amounts of suitable quality waters in hydroelectric dams, there is a large but still undetermined potential for cage aquaculture in the upper Paraná River basin. Sustainable aquaculture production should consider assessment of ecological carrying capacity for rational use of natural resources such as water bodies. The present survey estimates the ecological carrying capacity for tilapia cage culture in several sites on a large reservoir of “Ilha Solteira” upper Paraná River basin, Southeastern Brazil. Ecological carrying capacity was estimated based on the Dillon and Rigler (1975) mass balance model, considering limnological and farming field data to evaluate area-specific Phosphorus loads that can be assimilated in these environments. Using average farming data of feed composition, tilapia ( O. niloticus ) whole body composition and Feed Conversion Rate (FCR), the estimated emission of Phosphorus per ton of fish produced was 14.8 kg P ton −1 . Modeling provided evidence for the importance of feed Phosphorus content and availability for determination of total allowable production, as well as the relevance of proper inputs of limnological field data. When field data was collected, only two sites (Ponte Pensa and Dourados) had aquaculture activities; as aquaculture is expanding, limnological information provided in the present study is a registry of conditions found before the massive aquaculture development. Production estimated to the reservoir as a whole (156,000 ton) is more than fivefold the pooled production (30,000 ton) of the fifteen selected sites; if production estimated to the reservoir as a whole cluster around a few best sites, than effects on water quality is expected to be even more drastic. The limit of 1% occupancy by aquaculture posed by Brazilian government is not an effective safeguard against excessive eutrophication, and detailed limnological studies are demanded for each inlet assigned for cage aquaculture. The impact of cage fish farming on the aquatic environment by the release of nutrients that affect water quality can not only bring about conflict with multiple users, but also primarily exert a negative feedback effect in the cage operations themselves. [ABSTRACT FROM AUTHOR]

By using freshwater fish stocking information from the Mexican government, this work described the current situation of the national stocking and its associated fishery policy. There is a lack of effective freshwater stocking programmes as a result of limited fisheries management, unharmonized fisheries regulations and institutional performance. The fry production has decreased from 140 to 20 million in the past 11 years. [ABSTRACT FROM AUTHOR]

Asia dominates global aquaculture production accounting for over 80% of the total and the mainstay in Asian aquaculture is finfish. Over the years, Asia has experienced a number of inter-continental and intra-continental transfers/introductions/translocation of finfish species, between nations and watersheds, beyond their natural range of distribution, primarily for aquaculture development. In this article all such species are referred to as alien species. An attempt is made to evaluate the importance of the production of alien species in selected Asian nations, using statistics of the Food and Agriculture Organization. Also, negative effects, if any, based on literature surveys, of alien species in relation to displacement of indigenous species, and on biodiversity and/or genetic diversity together with associated pathogen transfers are evaluated. The major alien species, based on their significance to Asian inland aquaculture considered, are the tilapias, catfish, Chinese and Indian major carps and common carp. It is estimated that currently alien species account for nearly 12% of the cultured finfish production (2.6 million tonnes) in Asia, valued at US$ 2.59 billion, and the contribution exceeds 40% when Asian countries excluding China are taken into consideration. Inland finfish aquaculture in some Asian nations, such as Indonesia and the Philippines, is predominated by alien species, and in some others, e.g. Bangladesh and India, the contribution from alien species has been increasing steadily. It is suggested that overall alien finfish species have done little ecological harm to native flora and fauna. However, in the wake of increasing anthropogenic development taking place in watersheds the resulting environments are often made unconducive to indigenous species but not to some alien species, thereby potentially and indirectly making the latter invasive. [ABSTRACT FROM AUTHOR]

Abstract: Lipids extracted from three tilapia species (Oreochromis niloticus, O. macrochir and Tilapia rendalli) of mean weight 100–250 g collected in Itasy lake of Madagascar highlands during three seasons, were analyzed for their fatty acid compositions. The muscle fishes contained less than 1.4% lipid by weight. Gas chromatography (GC) and gas chromatography–mass spectrometry (GC–MS), allowed identification of more than 40 fatty acids and 30 of them were quantified in muscle tissue lipids of fishes. Among them, those occurring in the highest proportions were palmitic, stearic, oleic, palmitoleic and linoleic acids. The main polyunsaturated fatty acids were arachidonic acid, eicosa-5,8,11,14,17-pentaenoic acid (EPA) and docosa-4,7,10,13,16,19-hexaenoic acid (DHA). The relative amount of these acids changed significantly between species and season of collect, in particular DHA which decreased from 11.4% to 6.0% for O. macrochir during the spring to autumn period. For O. niloticus and T. rendalli, DHA decreased from 9.8% to 4.9% and to 10.1% to 4.4%, respectively during the same period. Therefore the ∑n−3/∑n−6 ratios vary, for each species according to season of collect, being lower in autumn (0.5–0.6) and raising up to 0.7–1.6 in winter. Multivariate statistical analyses, starting from the fatty acid composition, lipid percentage and biometric ratio (weight/size) data of 113 samples, reveals significative differences between species and season of collect. Furthermore differences in fatty acid profiles are higher within season than species. The results show that wild tilapias from tropical lakes of the Madagascar highlands possess beneficial properties and therefore contribute significantly of the n−3 fatty acids intake of the local population diet. [Copyright &y& Elsevier]

Within the tilapiines, a major African cichlid lineage, quite limited genetic informations are available on phylogenetic interrelationships and phylogeographical patterns at both macro- and micro-evolutionary scales. The present study examines the genetic diversity of the black-chinned tilapia complex from coastal areas in West Africa (Senegal to Congo-Brazzaville) based on mtDNA control region sequences. Phylogenetic inferences provide support for the monophyly of both taxa involved. It is suggested that Sarotherodon melanotheron and Sarotherodon nigripinnis have diverged probably since the early Pleistocene. The occurrence of the main intraspecific lineages could be dated back to about 500,000–900,000 years. Our data suggest that West African Pleistocene refuge zones may have strongly influenced the degree and level of genetic differentiation among populations and thus the observed phylogeographic patterns. The spatial distribution of mtDNA lineages and the centres of intrapopulational genetic diversity clearly correspond to proposed lowland refuge zones and core areas of Central Africa. Moreover, this study genetically supports the existence of Sarotherodon melanotheron leonensis for the first time and further confirms the validity of the most recently introduced subspecies, e.g., Sarotherodon nigripinnis dolloi. [Copyright &y& Elsevier]

Simple Summary: This study presents in silico models of neurokinin B receptor tiTac3Ra (tilapia Tachykinin 3 receptor a) and its potential binding sites, as well as docking native tilapia Neurokinin F (tiNKF) and tilapia Neurokinin B (tiNKB) to theses orthosteric binding sites. For a better understanding of the binding confirmation and interaction of the structures, we compared the conformation between peptide docking and induced fit docking results. We have tried to analyze the affinity of binding and binding site interactions parallel to in-vitro results of receptor activity. NKB antagonists inhibit male tilapia gonadal development and gonadotropin release. We further verified the in-vivo effect of the antagonists on gonadal development in males. Studying the receptor activity of variants with alanine mutations at Phe2516.44 and Met2897.43 respectively, we found that, while both variants completely underperformed, there was no direct interaction with the ligand in the binding process indicating their role in post binding receptor activation rather than the binding process itself. NKB (Neurokinin B) is already known to play a crucial role in fish reproduction, but little is known about the structure and function of NKB receptors. Based on an in silico model of the tilapia NKB receptor Tachykinin 3 receptor a (tiTac3Ra) found in the current study, we determined the key residues involved in binding to tilapia NKB and its functional homologue NKF (Neurokinin F). Despite studies in humans suggesting the crucial role of F2516.44 and M2897.43 in NKB binding, no direct peptide interaction was observed in tilapia homologs. In-silico, Ala mutations on residues F2516.44 and M2897.43 did not influence binding affinity, but significantly affected the stability of tiTac3Ra. Moreover, in vitro studies indicated them to be critical to tiNKB/tiNKF-induced receptor activity. The binding of NKB antagonists to tiTac3Ra both in-vitro and in vivo inhibits FSH (follicle stimulating hormone) and LH (luteinizing hormone) release and sperm production in mature tilapia males. Non-peptide NKB antagonist SB - 222200 had a strong inhibitory effect on the Tac3Ra activation. SB - 222200 also decreased LH plasma levels; two hours post intraperitoneal injection, changed sperm volume and the ratios of the different stages along the spermatogenesis in tilapia testes. [ABSTRACT FROM AUTHOR]

Abstract: We developed a high throughput DNA extraction protocol from tilapia fin tissue that enables the use of 96-well plates using a fluid micro-dispenser robot, thus effectively decreasing the time, cost and handling error of the DNA preparation stage. The method is based on the DNA salting out procedure and all fluid transfers are designed for use with a micro dispenser robot. The criterion of success was defined as extraction of at least 2 μg of DNA, which enables at least 100 PCR reactions. A total of 3163 samples met this criterion (98%). The cost of the proposed in-house protocol is approximately ten-fold lower than the commercial alternatives. The suggested high-throughput extraction protocol may be adjusted by slight modifications to handle other tissues. [Copyright &y& Elsevier]