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International Journal of Aquaculture 2026, Vol.16, No.1 http://www.aquapublisher.com/index.php/ija © 2026 AquaPublisher, registered at the publishing platform that is operated by Sophia Publishing Group, founded in British Columbia of Canada. All Rights Reserved. Publisher Aqua Publisher Edited by Editorial Team of International Journal of Aquaculture Email: edit@ija.aquapublisher.com Website: http://www.aquapublisher.com/index.php/ija Address: 11388 Stevenston Hwy, PO Box 96016, Richmond, V7A 5J5, British Columbia Canada International Journal of Aquaculture (ISSN 1927-5773) is an open access, peer reviewed journal published online by AquaPublisher. The journal publishes all the latest and outstanding research articles, letters and reviews in all working and studying within varied areas of aquaculture, containing the latest developments and techniques for practice in aquaculture; information about the entire area of applied aquaculture, including breeding and genetics, physiology, aquaculture-environment, hatchery design and management, utilization of primary and secondary resources in aquaculture, production and harvest, the biology and culture of aquaculturally important and emerging species. All the articles published in International Journal of Aquaculture are Open Access, and are distributed under the terms of the Creative Commons Attribution License, which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited. AquaPublisher uses CrossCheck service to identify academic plagiarism through the world’s leading plagiarism prevention tool, iParadigms, and to protect the original authors' copyrights. Aqua Publisher is an international Open Access publisher specializing in the field of marine science and aquaculture registered at the publishing platform that is operated by Sophia Publishing Group (SPG), founded in British Columbia of Canada.
International Journal of Aquaculture (online), 2026, Vol. 16, No. 1 ISSN 1927-6648 http://aquapublisher.com/index.php/ija © 2026 AquaPublisher, registered at the publishing platform that is operated by Sophia Publishing Group, founded in British Columbia of Canada. All Rights Reserved. Latest Content Growth Performance of Clarias gariepinus (Burchell, 1822) fed with Local Feed without Fish Meal S.M.A. Djissou, M.N.A. Fagbémi, L.B. Badji, D. Konaté, Y. Bangoura, G. Djidohokpin, R. Adandé, M.A. Baldé International Journal of Aquaculture, 2026, Vol. 16, No. 1, 1-7 A Review on Pearl Farming: the Rising Trend in India Tanisha, Asma Fayaz International Journal of Aquaculture, 2026, Vol. 16, No. 1, 8-17 The Future of Aquaculture: Sustainable Development, Economic Growth, and Environmental Protection Ninawe A.S., Shakir C., Subhash S.K., John R. International Journal of Aquaculture, 2026, Vol. 16, No. 1, 18-31 Smart Technologies in Fisheries: Innovations in Monitoring, Management, and Sustainability Yanhong Liu, Rudi Mai International Journal of Aquaculture, 2026, Vol. 16, No. 1, 32-45 Management and Mitigation Strategies for Harmful Algal Blooms: Current Approaches and Future Prospects Manman Li, Xianming Li International Journal of Aquaculture, 2026, Vol. 16, No. 1, 46-60
International Journal of Aquaculture, 2026, Vol.16, No.1, 1-7 http://www.aquapublisher.com/index.php/ija 1 Research Article Open Access Growth Performance of Clarias gariepinus (Burchell, 1822) fed with Local Feed without Fish Meal S.M.A. Djissou 1 , M.N.A. Fagbémi 1, L.B. Badji 1, D. Konaté 1, Y. Bangoura 1, G. Djidohokpin2, R. Adandé 2, M.A. Baldé 1 1 Department of Fisheries and Aquaculture, Institut Supérieur des Sciences et de Médecine Vétérinaire de Dalaba, Dalaba, Guinea 2 Department of Natural Resource Management, Faculty of Environmental Sciences, University of N'Zérékoré, N'Zérékoré, Guinea Corresponding email: arnauldb52@gmail.com International Journal of Aquaculture, 2026, Vol.16, No.1 doi: 10.5376/ija.2026.16.0001 Received: 11 Nov., 2025 Accepted: 01 Jan., 2026 Published: 24 Jan., 2026 Copyright © 2026 Djissou et al., This is an open access article published under the terms of the Creative Commons Attribution License, which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited. Preferred citation for this article: Djissou S.M.A., Fagbémi M.N.A., Badji L.B., Konaté D., Bangoura Y., Djidohokpin G., Adandé R., and Baldé M.A., 2026, Growth performance of Clarias gariepinus (Burchell, 1822) fed with local feed without fish meal, International Journal of Aquaculture, 16(1): 1-7 (doi: 10.5376/ija.2026.16.0001) Abstract In fish farming, feed accounts for a large proportion of production costs because of the use of fish meal and fish oil. The aim of this study was to develop a local feed from available local resources. To this end, a local feed balanced in essential amino acids and based on maggots (Musca domestica), earthworms (Eisenia fetida) and brewer's yeast as a total replacement for fishmeal was tested onClarias gariepinus fry of average initial weight Pmi= 4.39± 0.01g for 90 days. Tested with three replicates, the feeds (control feedT0 - imported (Gouessant) and local feed T1) were used to feed fry distributed in tanks (volume 0.5m3 each) with a density of 100 individuals / tank. Results showed that no significant differences were found in final weight and weight gain (p>0.05), whereas survival and protein intake differed significantly (p<0.05) between T0 and T1. Feed utilisation parameters showed better utilisation of the T1 local feed, with a consumption index of 1.01 and a protein efficiency coefficient of 1.9. Economic analysis showed that local feed T1 was about half the cost of commercial feed T0. Nevertheless, further investigations are required to determine the impact of using this local feed on the organoleptic quality and reproductive capacity of the products obtained. Keywords Clarias gariepinus; Total replacement; Local feed; Reproductive capacity 1 Introduction Demographic pressure and rising global fish consumption have encouraged intensive, and often irresponsible, fishing. This overfishing has endangered many wild fish species. Biodiversity is also under serious threat from pollution of the natural environment and overfishing with prohibited gear, leading to the disappearance of certain aquatic species (Welly et al., 2020) In this context, aquaculture, and in particular fish farming, appears to be the answer to reducing overfishing and satisfying the growing consumption of fish. In many African countries, like Guinea, aquaculture is being developed (FAO, 2024). Despite Guinea's considerable potential, fish farming is practised extensively, seasonally in ponds, puddles and reservoirs (MPAEM, 2015). Furthermore, the development of aquaculture in Guinea is coming up against a number of problems, including a lack of high-performance feed on the local market at prices that fish farmers can afford. The main activity of rural Guinean populations is agriculture, which plays an unprecedented economic and social role (MPAEM, 2015). In West Africa, maggots or black soldier fly (Hermetia illucens) and housefly (Musca domestica) larvae are increasingly used in fish feed (Djissou et al., 2020; Gangbazo Kpogue et al., 2024). Known for their high nutritional quality (protein and essential amino acid content in particular), maggot meal is increasingly used in the manufacture of fish feed because of its short production cycle and affordable price. Maggots are also biodegraders of organic waste, the management of which is a major environmental concern in Africa (Odjo et al., 2018). The economic interest of aquaculture is highly dependent on the availability and cost of feed (Djissou et al., 2016). Reducing feed costs, and consequently controlling the production cost of farmed fish, is therefore one of the priorities in aquaculture (Djissou et al., 2020). In fact, fish meal is an essential and practically unavoidable
International Journal of Aquaculture, 2026, Vol.16, No.1, 1-7 http://www.aquapublisher.com/index.php/ija 2 ingredient in aquaculture feeds due to its richness in Essential Amino Acids (EAA), the profile of which corresponds remarkably well to the needs of fish (Médale et al., 2013). However, according to Vodounnou et al (2025), the high cost of fish meal, coupled with its unavailability and variable quality on the local market, does little to improve the economic profitability of aquaculture. There is therefore an urgent need to find alternatives to fish meal for use in aquaculture. Increasingly, both plant and animal protein sources are being used as partial or total substitutes for fish meal (Médale et al. 2013; Djissou et al., 2020). The use of animal protein sources (termites, maggots and earthworms) and plant sources (peanut, sunflower and soybean cakes, bean meal and brewer's yeast) in aquaculture as substitutes for fish meal has thus been initiated (Gougbédji et al., 2020; Atchamouet al., 2024; Djissou et al., 2016) in several species, including Clarias gariepinus, with variable performance. Clarias gariepinus is an omnivorous species with carnivorous tendencies and a high growth and economic potential. In Guinea, this species of great piscicultural interest is one of the species that fish farmers are most familiar with. Nevertheless, its production faces a number of difficulties, including the high cost and quality of the feed used, which is crucial to the development of the industry. In replacement of the fish meal, the proteinic sources must bring the ten essential amino acids (EAA) required for fishes (Médale et al., 2013). To satisfy the essential amino acids requirements for Clarias gariepinus fingerlings, the experimental diets without fish meal based on a mixture of earthworm and maggots (proteinic sources) were tested on Clarias gariepinus (Djissou et al., 2016; 2025) and Oreochromis niloticus (Djissou et al., 2020) with good performances of growth and feed utilization for the pre-growing of fingerlings in Benin. This study was therefore initiated with the aim of promoting fish farming by developing a high-performance local feed that is free of fish meal and fish oil, and at a lower cost for the growth of fingerlings in Guinea. 2 Methodology 2.1 Experimental set-up The experiment was carried out in an open circuit in six (06) circular above-ground concrete tanks, completely randomized, with a total volume of 0.5 m3 each with of water supplied by borehole and a compressor (FIAC, axair 100L 2CV 10B 230 V) at a flow rate of 3 L min-1. Half of the surface of each tank was covered with a screen to prevent direct sunlight penetration and, above all, the development of chlorophyll algae under the effect of solar radiation. A total of 600 Clarias gariepinus fingerlings, with an average initial weight of 4.39±0.07 g, were placed in the tanks at a stocking density of 100 fingerlings per tank. The fingerlings (tested with three replicates) were acclimatized for one week before starting the trial. 2.2 Obtaining the protein sources used to replace fish meal The rearing of alternative animal protein sources was conducted at the experimental site. Earthworms (Eisenia foetida) were reared for 90 days (one production cycle) on a pig-manure substrate following the method described by Vodounnou et al. (2016). Maggots (Musca domestica) were reared on a substrate composed of soybean meal and chicken viscera, according to Odjo et al. (2018). Earthworm and maggot meals were processed in the same manner as the chicken viscera: the biomass was washed, drained, and gently cooked over low heat, then dried and ground into flour. The resulting meals were sealed in airtight plastic bags and stored under refrigeration until use. 2.3 Bromatological analysis Diet T1 was analyzed according to AOAC (2005) procedures. Amino acids from diet were analyzed with a Waters HPLC method. These amino acid analyses were carried out using the method previously described by Bosh et al. (2006). Aminobutyric acid was added as an internal standard prior to hydrolysis. After experimentation, proteins, lipids and ash of 20 homogenized carcasses of fish taken randomly after 3 days from experiment in each diet. Crude protein (%N X 6.25) was determined by the Kjedahl method, fat by the hot method (Soxhlet type) and ash after incineration of the samples in a muffle furnace at 550 °C for 12 hours. 2 . 4 Feed formulation, manufacture and feeding frequency The batches of C. gariepinus were fed two different diets during this experiment. The control diet T0 (Gouessant) is
International Journal of Aquaculture, 2026, Vol.16, No.1, 1-7 http://www.aquapublisher.com/index.php/ija 3 an imported commercial feed. The experimental diet is made up of ingredients including earthworms, maggots and brewer's yeast used as a source of protein that completely replaces fish meal (Table 1). With a feeding frequency of 4 times a day, the fish were fed for 90 days at a ration rate of 5% with the tested feeds. Table 1 Feed composition of the imported feed (T0) and the local feed (T1) developed Ingredients T0 (%) T1 (%) Rice bran - 5 Soy flour - 25 Brewer's yeast - 5 Cotton cake - 15 Earthworm meal - 12 Maggot flour - 30.5 Palmoil - 3 Vitamin - 1 Minerals - 1 Starch - 2 Methionine - 0.5 Crude protein 42 40 Fats and oils 11 12.9 Total ash 7.9 6.5 To make the food, the ground ingredients were weighed and mixed until a homogeneous powder was obtained, to which palm oil was added. Water was then added to obtain a malleable paste. A pelletiser with a mesh size of 1.5 and 2 mm was used to produce the pellets, depending on the development of the fish. The manufactured feeds were dried in the sun before being stored in boxes for conservation (-4 °C) before distribution (Table 2). Table 2 Composition in essential amino acids (EAA) of the local feed developed (g.kg-1 of feed) Essential amino acids T1 EAA requirements of C. gariepinus* Threonine 8 5-5.6 Valine 7 7.1-8.4 Methionine 9 6-6.4 Isoleucine 11 6-7.3 Leucine 19 8-9.8 Phenylalanine 13 12-14 Histidine 9 4-4.2 Tryptophan 6 1.2-1.4 Lysine 14 12-14.3 Arginine 20 10-12 Table caption: : * NRC (2011) 2.5 Water physico-chemistry and biological monitoring Water quality was monitored every 3 days by determining (twice a day) physico-chemical parameters such as temperature, dissolved oxygen, pH, conductivity and TDS using a multiparameter (ORCHIDIS SN-ODEOA-2138). Control fishing took place every two weeks, followed by emptying and cleaning of the tanks. The number and biomass of fish in each tank were determined by counting and using a centesimal- precision scale (TANITA KD-192). 2.6 Zootechnical and economic parameters Growth, feed utilization and economic performances were determined by the average final weight (AFW), the Percentage Weight Gain (PWG), the Specific Growth Rate (SGR), the Survival Rate (SR), the Consumption Index (CI), the Protein Intake (PI), the Protein Efficiency Coefficient (PEC), the cost of manufacturing one kilogram of
International Journal of Aquaculture, 2026, Vol.16, No.1, 1-7 http://www.aquapublisher.com/index.php/ija 4 experimental local feed, the costs associated with manufacturing one kilogram of feed, the total production cost per kilogram of fish and the profit per kilogram of fish. The following formulas were used: Pmf= Final biomass (g) / Final number of fish. PGP= 100 x (Final average weight (g) - Initial average weight (g)) / Initial average weight IC = Quantity of feed ingested(g) / Weight gain(g) PI= Ration distributed x Crude protein / Final number of fish. CEP= Weight gain(g) / Protein intake(g) TCS (in %/d) = [Ln (Mf) - Ln (Mi) / t(d)] x 100 TS (in %) = (Number of final individuals / Number of initial individuals) x 100. Cost per kilogram of feed from usual by-products =∑ (unit price of raw materials x proportions used) Cost of manufacturing one kilogram of feed =∑ (cost of substrates+ milling price) x 100 / Rd with Rd the ration distributed Total cost of a kilogram of feed= cost of a kilogram of feed from the usual sub-products + costs associated with manufacturing a kilogram of feed. Total production cost per kilogram of fish= Total production cost per kilogram of feed x IC Profit= Selling price per kilogram of fish - total production cost per kilogram of fish 2.7 Statistical analysis Statistical analysis was carried out according to standard one-criterion analysis of variance (ANOVA) methods using Statistica version 6 software with a significance level of 5%. The Fisher LSD test was used for paired comparisons of means. 3 Results and Discussion 3.1 Farm water quality Throughout the trial period, mean temperature values of around 28.4±0.6°C and 29.3±0.4°C were recorded at the T0 and T1 regime ponds, respectively. These measured temperatures are within the range (26 °C~30 °C) recommended by (Ipungu et al., 2019) for good growth of Clarias gariepinus. With regard to dissolved oxygen, the values recorded during the experiment were 4.22±0.9 mg·L-1for regime T1 and 5.80±0.29 mg.L for regime T0. These recorded values are higher than the 3 mg/L reported by Ipungu et al. (2019) and are favourable for the growth of C. gariepinus. For pH, values of 5.38±0.42 and 5.68±0.31 respectively for T1 and T0 farm waters. The pH values indicate a slight acidity in the rearing water. However, they are likely to allow good growth of C. gariepinus (Ipungu et al., 2019). The values recorded for conductivity were 62.7±2.19 for the T0 regime and 72.6±1.26 µs/cm for the T1 regime, in contrast to TDS, where the values recorded were 42.9±1.11 and 49.2±1.37 ppm for the T0 and T1 regimes respectively. 3.2 Zootechnical and economic parameters The zootechnical and economic performances obtained with the feeds tested after 90 days are presented in Table 3. Growth parameters such as Pmf, TCS, PGP reveal that there is no significant difference (p>0.05) in performance obtained between the local feed T1 and the imported feed (control - T0) with the exception of TCS. These results corroborate the work of Djissou et al. (2016) who used maggots and earthworms as a total replacement for fish meal to feed C. gariepinus fingerlings with similar growth performance (Table 3).
International Journal of Aquaculture, 2026, Vol.16, No.1, 1-7 http://www.aquapublisher.com/index.php/ija 5 Table 3 Zootechnical and economic parameters obtained with the experimental systems Zootechnical parameters Experimental regimes T0 T1 Pmi (g) 4.40± 0.01a 4.39± 0.01a Pmf (g) 140.30± 5.71a 139.68± 1.26a TS (%) 98.33± 3.11a 93.00± 0.66b IC 1.11± 0.04a 1.01± 0.02b CEP 1.01± 0.24a 1.9±0.05b TCS (%/d) 4.23± 0.02a 4.10± 0.01a PGP (%) 3091.14± 131.61a 3081.70± 23.85a PI 50.99± 2.11b 61.18± 0.84a Economic parameters Cost per kg (GNF/Kg) - 5 265 Manufacturing costs per kg of feed (GNF/Kg) - 2 860 Total cost per kg of feed (GNF/Kg) 15 052 8 125 Total production cost per kg of fish (GNF/Kg) 16 708 8 206 Selling price per kg of fish (GNF/Kg) 22 578 22 578 Profit (GNF/Kg)* 5 875 14 373 Table caption: T0= Control food, T1= Local food. Values with the same letters on the same line are not significantly different (p>0.05). Values are expressed as mean± standard deviation. * Prices are in GNF and are based on exchange rates in November 2025. Labour and processing costs were included by adding 20% to the ingredient costs (Azaza et al., 2006). As for nutritional requirements, the crude protein content of the diet tested in this study (40%) is within the range of optimal requirements for catfish (Clarias gariepinus, Heterobranchus bidorsalis and Heteroclarias), which is between 40% and 42.5% (Monebi and Ugwumba, 2013). Several studies have shown that total replacement of fish meal by maggot or earthworm meal reduced the growth rate of fish such as Heterobranchus longifilis (Sogbesan et al., 2007), Heteroclarias (Monebi and Ugwumba, 2013) and Clarias gariepinus (Djissou et al., 2016). The results of these studies contradict our results, which show good use of the local feed with a better consumption index (1.01) and ingested protein (61.18), in addition to the good growth performance obtained. Meeting the essential amino acid requirements of C. gariepinus also contributed to this performance. In fact, when formulating fish feed, meeting the growth requirements of fish depends not only on the quantity of protein provided by the feed, but also on its quality, i.e. the nature of the amino acids provided, particularly the essential ones. In our work, the results obtained are therefore explained by the quality of the feed (protein and essential amino acids) which satisfies the needs of C. gariepinus for good growth. Furthermore, Djissou et al. (2016; 2017) showed that fish meal can be completely replaced by a combination of Azolla filiculoides, brewer's yeast, maggot and Dialium guineense leaf in the diet of Oreochromis niloticus with good growth performance. However, when the essential amino acid composition of the feed does not meet the needs of the fish, this influences the net energy value of the proteins and increases the metabolism of the fish, as well as polluting the environment with nitrogenous waste (Medale and Kaushik, 2009). It should be noted that the biological value of the protein source depends on its essential amino acid profile (Table 2) as well as its digestibility. The values of CEP and PGP (Table 3) recorded with the test feed are due not only to the protein sources used as total replacements for fish meal (earthworm, maggot and brewer's yeast), which are rich in EAA (Adesina, 2012), but also to the diet of C. gariepinus. The PER obtained are generally lower than those obtained by Nyinawamwiza (2007), who completely replaced fish meal with groundnut, soybean and groundnut meal in the diet of C. gariepinus. Nevertheless, the local feed would be well digestible for the fish in view of the feed utilisation parameters obtained. An optimal profile of essential amino acids is a prerequisite for fish growth (Medale et al., 2013). The feed tested in this study is of high quality in protein value because it contains all the EAAs with higher values with the exception of methionine (Djissou et al., 2020). In fact, lysine and methionine are the first limiting EFAs in many fish feeds,
International Journal of Aquaculture, 2026, Vol.16, No.1, 1-7 http://www.aquapublisher.com/index.php/ija 6 mainly in those based on unusual protein sources. In addition, lysine is one of the amino acids involved in growth processes and is known to act together with arginine to increase the activity of the latter (Furuya et al., 2023). Its normal level in the local feed clearly explains the better growth rates recorded. Similarly, the better growth recorded with the tested feed can also be justified by the optimal level of phenylalanine, which is within the recommended range (NRC, 2011), an amino acid capable of increasing the growth rate of catfish (Furuya et al., 2023). The results indicate that C. gariepinus fingerlings efficiently utilized the local feed tested with total replacement of fish meal by the combination of earthworm, maggot and brewer's yeast meal. Feed is the most expensive input in fish farming, accounting for up to 60% of total production costs (Gangbazo Kpogue et al., 2024). Analysis of the economic parameters showed that the cost of producing one kilogram of fish was 8206 GNF for the local feed, compared with 16708 GNF for the imported control feed. The profit obtained with the local feed was 14373 GNF per kilogram of fish produced, compared with 5875 GNF for the imported commercial feed. This shows the profitability of feeding C. gariepinus local feed without fish meal made from local by-products. Nevertheless, for industrial production of local feed T1, electricity, various taxes and transport must be taken into account in determining the production cost per kilogram of feed. The use of these proteins in fish feed helps to recover animal and industrial waste and to clean up the environment by recycling animal and industrial production waste. The observed difference in survival could be attributed to the digestibility of feed T1, which was formulated using ingredients such as soybean and cottonseed meal. These ingredients contain antinutritional factors, such as gossypol, fibre and tannins (Imorou Toko et al., 2008). These factors lead to poor nutrient absorption or mortality related to digestive disorders. 4 Conclusion Profitable fish farming requires the use of protein sources other than fish meal. However, large quantities of plant and animal proteins exist that are not used in human food and could partially, or even totally, replace fish meal in fish farming. Here, the results show that the use of local sources of protein (maggots, earthworms and brewer's yeast) as a total replacement for fish meal in the diet of C. gariepinus makes it possible to obtain good growth performance and feed utilization with improved profitability. These results are of great interest because they allow us to conclude that feed formulas based on local by-products can be developed without fish meal and fish oil with good performance. Nevertheless, further investigations are required to ascertain the impact of using this local feed on the organoleptic quality of the muscle of the fish produced, as well as the impact of this feed on the reproductive capacity of adult C. gariepinus, i.e. on the quality of the gonads of broodstock fed with this local feed. References Adesina A.J., 2012, Comparability of the proximate and amino acids composition of maggot meal, Earthworm meal and soybean meal for use as feedstuffs and feed formulations, Elixir Applied Biology, 51: 10693-10699 AOAC, 2005, Official Methods of Analysis, 18th ed. Washington DC. 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International Journal of Aquaculture, 2026, Vol.16, No.1, 8-17 http://www.aquapublisher.com/index.php/ija 8 Research Article Open Access A Review on Pearl Farming: the Rising Trend in India Tanisha 1, Asma Fayaz 2 1 Chandigarh University, Punjab, India 2 Faculty of Agriculture, Chandigarh University, Punjab, India Corresponding email: asma.e9423@cumail.in International Journal of Aquaculture, 2026, Vol.16, No.1 doi: 10.5376/ija.2026.16.0002 Received: 28 Oct., 2025 Accepted: 03 Jan., 2026 Published: 30 Jan., 2026 Copyright © 2026 Tanisha and Fayaz, This is an open access article published under the terms of the Creative Commons Attribution License, which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited. Preferred citation for this article: Tanisha and Fayaz A., 2026, A review on pearl farming: the rising trend in India, International Journal of Aquaculture, 16(1): 8-17 (doi: 10.5376/ija.2026.16.0002) Abstract Pearl farming, the ideal blend of production of gems and water. It is being considered as a practice that has sustainability and innovation that is not only economically but ecologically helpful too. China is the most prominent producer by fresh water pearl cultures in large scale. Behind Japan, there are Akoya pearls- high quality pearls and the exotic black pearls of French Polynesia. These two countries have jointly established a multibillion-dollar pearl industry in the world. Pearl farming continues to be in its nascent stage in India with the initiatives that were taken by the CMFRI (Central Marine Fisheries Research Institute) in starting of 1970. Despite demonstrations that have shown that it is practical through successful experiences with Pinctada fucata and freshwater mussels such as Lamellidens marginalis, the uptake is low. Nevertheless, the prospects are in satisfying the increasing demand of the global and domestic market of ornamental pearl, diversification of aquaculture and the creation of jobs in the rural areas. The pearl farming business in India is facing major challenges such as the technical expertise in surgical nucleation, inadequate infrastructure and high start-up capital despite the potential of the industry being enormous. India can transform this sector by concentrating on research, skill building and by coming up with favourable government policies. This would not only tie in sustainable aquaculture with economic growth but also make the country one of the key international markets in terms of pearl. Keywords Pearls; Aquaculture; Lamellidens spp.; Oysters; Sustainable marine farming 1 Introduction A Pearl is naturally produced gem, or gemstone that is produced within the soft tissues of some mollusc species such as oysters in the sea waters and mussels in the freshwater environments. This gem is highly lustrous, or has an assortment of colours, and is often a perfect round. It consists of 85% calcium carbonate, 12 percent organic matrix and water. The primary constituent is calcium carbonate that may have the form of aragonite or calcite. It surrounds all foreign particles or irritants that might have entered and lodged within the interior of the shell of the mollusc. The pearl has hardness value between 3.5 and 4.5 and specific gravity 2.7. Any mollusc may produce any form of pearl; but the finest pearls are those produced by those which have nacre on the outer shell. Pearls are grouped into three categories of natural pearls, cultured pearls and artificial pearls (Alagarswami, 1974). Pearl farming/pearl culture is a subdivision of aquaculture which denotes the cultivation of pearls in a controlled or semi-controlled environment through the rearing of pearl oysters or freshwater mussels. To make a pearl, a nucleus and mantle tissue transplantation is surgically inserted into the mollusc that then secretes shells of nacre (calcium carbonate and organic matrix) around the implant. There are several processes involved in pearl farming which requires 12~24 months to produce the first pearls. 2 Global History of Pearl Farming The earliest, free and round man-made/cultured pearl of India was produced at Pearl Culture Laboratory, a division of the Central Marine Fisheries Research Institute, at Veppalodai, near Tuticorin in July 1973. It was prepared by using Indian pearl oyster Pinctada fucata. Cultural technology has now produced pearls of different sizes and colour. Pearls began to be cultivated first in Japan in 1893 when half-pearls on shells were produced, and then in 1907 with the successful breeding of spherical ones. It has since been dominated in the production, marketing and technology of cultured pearls, in the world. In 1956, Australia began to farm pearls with Japan, and
International Journal of Aquaculture, 2026, Vol.16, No.1, 8-17 http://www.aquapublisher.com/index.php/ija 9 Philippines and Burma also joined in such partnerships. In Hong Kong, Palau, Celebes and some other South-West Pacific islands, limited-scale production has been taken up. In the majority of joint ventures, Japan exports technical knowledge and does marketing, whereas the host country contributes primarily to the creation and maintenance of farms. Past studies have identified the Japanese approaches and pointed out the possible potential of India in the cultured pearl (Nagai, 2013). 3 History of Pearl Farming in India In the Gulf of Kutch and Gulf of Mannar, India has a history of pearl fishing of natural pearls. But there are ups and downs in oyster production in these regions, and between productive fisheries, there are some seasons when the oysters are barren. Since 1900 the Gulf of Mannar has had only 12 seasons of fishing, the seven-year grand series of 1955 to 1961. India has ceased pearl fishing in Gulf of Mannar (after 1961) and in Gulf of Kutch (1966-1967). Oysters were collected in the pearl banks of Tuticorin by means of diving and using SCUBA, and then transported to the farm where they were cleansed and measured. They were outlawed in rafts and placed in sandwich-like frame nets with repeat laboratory tests on purity and growth checks. Even though the oysters were fairly healthy, barnacle infestation became an issue of serious concern and resulted in certain mortality. The vigorous of shell margin indicates that the sea of Veppalodai is an appropriate location where oysters can grow. The Kallar River contributed to freshwater inflow during the northeast monsoon which reduced the salinity marginally but did not have any adverse effects. Light penetration was poor, in the 4-meter-deep farm field (approximately 1.5 meters) and total water clarity was poor (Alagarswami, 1974). 4 Major Species and Regions The main species of pearl production that is cultivated in freshwater systems are the Indian pond mussel (Lamellidens marginalis). Its adaptability to the conditions of the Indian environment and the possibility to grow high-quality pearls under conditions characterized as controlled habitats (pond, tank, integrated multi-trophic aquaculture systems, etc.) contribute to its popularity (Saurabh et al., 2022). There are approximately 3,270 molluscan species that inhabit India, 1 100 of which are bivalves. These include 625 species of marine bivalves of which 88 are endemics. Approximately, 52 mussel species have been reported in freshwater ecosystems and these are found in both stagnant and low-moving water bodies. Large-scale pearl production in India, despite such diversity, is temperately reliant upon three freshwater mussel species that belong to the Unionidae family -Lamellidens marginalis, Lamellidens corrianus, andParreysia. CIFA (Central Institute of Freshwater Aquaculture), Bhubaneswar, has been a leader in establishing and distributing freshwater pearl culture technologies in India (Saurabh et al., 2022). Marine pearl farming is instead based on the Indian pearl oyster (Pinctada fucata), especially in coastal states (such as Tamil Nadu, Kerala, and Andhra Pradesh). In India, freshwater pearl mussels and marine pearl-producing oysters are very prolific. Pinctada margeretifera in Andaman and Nicobar Islands and Pinctada fucata in the Gulf of Mannar, Palk Bay, and the Gulf of Kutch are pearl-producing oysters (Sharma, 2005). 5 Classification of Pearls 5.1 Natural pearls In a case of swallowing a foreign particle by a pearl oyster without any human intervention the natural pearl is formed. The natural pearls consist of nacre crystallized into pearls of greater thickness. It is unevenly shaped and comparatively smaller. The reason for its uneven shape is edge formation of covering crystals of aragonite (Birunagi et al., 2024). 5.2 Cultivated pearls It is alike naturally occurring pearls but, the nucleus is surgically implanted into the mussel instead of natural swallowing of any foreign particle. This culturing technique of making natural pearls can yield the required size, shape, colour and lustre of the pearl. They can be spherical, semi-spherical or designer pearls depending on the size and shape of the nucleus (Alexander and Kumar Verma, 2023).
International Journal of Aquaculture, 2026, Vol.16, No.1, 8-17 http://www.aquapublisher.com/index.php/ija 10 5.3 Imitation or artificial pearls To replace actual or cultured pearls, imitation pearls are prepared by applying tough, round bases, with materials that mimic the qualities of pearls. The coating may show a difference in response to inexpensive glittering paints, imitated pearl essences crafted of fish scales, and so on. The artificial pearls leave a trace on their smooth surface when pressed against a sharp object in contrast to natural or cultivated pearls (Alexander and Kumar Verma, 2023) (Figure 1). Figure 1 Classification of pearls 6 Biological and Technological Aspects The pearls are formed by placing an irritant, usually a tiny bead or tissue lining, surgically into the mollusc into which the nacre is embedded to form the pearl in a few months to years (Saurabh et al., 2022). It is of paramount importance to maintain optimal water quality because physiological stress caused by such factors as ammonia may negatively influence the state of mussels and the quality of pearls. As an example, high levels of ammonia may disrupt important enzyme functions and antioxidation defences in Lamellidens marginalis, proving that the quality of water is reviewed and managed to ensure sustainable pearl culture (Chhandaprajnadarsini et al., 2025). In order to facilitate operational efficiency, smart monitoring systems adoptions, including the use of IoT-enabled water quality sensors, application of machine learning models to predict the environment, etc. have become increasingly prevalent. Such technologies are able to forecast variations in such parameters as dissolved oxygen and pH to allow farmers to make appropriate interventions in time (Singh et al., 2022). As part of its survival mechanisms, the marine oysters (particularly, Pinctada spp.) rely on their in-built immunity or an immune system to counter the environmental pressures like changes in temperature, salinity, the presence of pathogens and pollutants, etc. Antimicrobial peptides, lectins, heat shock proteins, and antioxidant enzymes are activated within them to sustain the cellular homeostasis. The pearl oyster can survive in unpredictable marine conditions with this capability. However, severe stress system may undermine the immunity of oysters and quality of pearls (Adzigbli et al., 2020). 7 Freshwater Pearl Culture Pearl faming in freshwater involves the following steps sequentially: 7.1 Collection of mussels The freshwater bodies have the mussels cleared manually and then transported to farm where they are harvested in a healthy manner. The habitats are primarily submerged in shallow peripheral regions and are primarily concealed
International Journal of Aquaculture, 2026, Vol.16, No.1, 8-17 http://www.aquapublisher.com/index.php/ija 11 by mud or sand. Habitats are in form of immobile stationary ponds, tanks, lakes, rivers, and reservations. Harvested pearl mussels on the natural bed are not always reliable because of their irregular harvest and contaminated water. The mussels seed grown in the hatcheries are much superior regarding the right supply of the pearls mussels to keep up the yearlong production. The mussels are grafted after growing such seed, according to weight, age, the degree to which they have sexual maturation and health in general (Ali and Rawat, 2023). 7.2 Pre-operative conditioning The native pearl mussel species which were collected as freshwater are then subjected to the two-day pre-operative conditioning. They are kept in 200-liter ferro-cement tanks where the stocking density of the mussel is one mussel per litre. The pre-operative conditioning takes proper care of the relaxation of adductor muscles before surgery. This is important considering the low application of narcotizing methods that are used in the marine pearl production activities (Misra et al., 2009). 7.3 Selection and conditioning for surgery Oysters that are 20 grams and above, are used to perform operational surgery with a goal of producing good outcome. They should be healthy and non-infected from borers. Oysters with maturing or mature gonads would be inappropriate because the gametes leak out during surgery and obscure the implantation site. Gametes may flow rapidly along the channel and the resultant graft tissue and nucleus may remain in place. Consequently, the selection of the oysters ought to be made of just oysters that are either at the initial stages of gametogenesis or recovering after spawning. The soft areas should be free of shells of sponge borers, polychaete blisters and trematode infections. The oysters should be stripped off all foul organisms. The oysters are chemically conditioned to operate. Menthol crystals are added into the seawater in troughs of the oysters that are carefully selected. The oysters narcotize within 45~60 minutes and at this stage the valves are open because of adductor muscle’s loosening. Once each oyster is stripped, a wooden peg is placed between the valves and rinsed in sea water. The use of such narcotized oysters in the procedure should be as immediate as possible. When the oysters are put in pure seawater after surgery they will heal in 30~45 minutes (Victor et al., 1995). 7.4 Surgical implantation Surgical implantations can take place in three sections of the mussel, which are of three different kinds depending on the kind of pearl being aimed at. A particular type of implantation is undertaken with each mussel. The mantle cavity insertion method is simple. The mussels of the weight and shell length required are collected prior to operation. They are appropriately opened with a 0.5 cm broad speculum that does not damage the soft tissues and adductor muscle of the mussels. An aperture the size and shape of a planned pearl, say 1 cm is cautiously inserted into the mantle cavity after a small section of the anterior side of the mantle has been detached, with care, at the top shell valve. Then it is driven in deep to avoid being rejected. One mussel may be implanted with the foreign organism that is desired in both of its valves. Before surgery in the mantle tissue procedure, the mussels that are to be operated upon (the recipient mussels) and those sacrificed (the donor mussels) are separated into two categories. The pallial mantle ribbon of the living donor mussels is excised, clipped to grafts of the appropriate size and c alone or together with a small nucleus (2 mm in diameter). This kind of grafting is performed on both of the mantle lobes. There can be two to eight implantations depending on the size and thickness of the mantle of the recipient mussel. In preparing the live graft parts to be implanted through the gonadal procedure, the recipient mussels are opened carefully to a depth of about 0.5 cm with a shell opener. Another end of the graft needle has a specialized knife that makes a tiny, precisely calibrated slit when he is making the incision beneath the outer membrane of the gonad. Caution should be observed that one does not make deep cuts into the gonadal tissue in order to avoid injuries to the intestinal coils. Only one implantation per oyster is to be done (Misra et al., 2009).
International Journal of Aquaculture, 2026, Vol.16, No.1, 8-17 http://www.aquapublisher.com/index.php/ija 12 Precautions: 1) Wash the instruments properly, before and after use. 2) Avoid the use of mature oysters for nucleus implantation. 3) Avoid harming the stomach, heart, or intestine. 4) Make the incision or cut according to nucleus size. 7.5 Post-operative care and culture Oysters are maintained in a flow-through system after operation until they are narcotized, or frequent water changes are done where flow-through system is not accessible. They spend three to four days in the lab in order to reduce stress by being observed in filtered clean water. Once they have been stabilized, they are taken to the farm and kept in fitting cages. Oysters are kept to low densities, suspended at lower levels and are treated sparingly to avoid stress during the post-operative stage. The period of culture on the nuclei with size in the range 2-5 mm takes 3-12 months in Indian conditions. The last harvest period is based on the harvests that are experimental and monthly observed (Victor et al., 1995). 7.6 Pearl formation 7.6.1 Natural pearl formation Pearl formation in pearl oysters begins with organic or inorganic nucleus (e.g. sand grains, parasites, molluscan eggs, plant debris, epithelium cells of same animal etc.). These particles invade the oyster during feeding or breathing and sink in between shell and mantle. As an answer, mantle epithelium invaginate the foreign body and create a pearl-sac surrounding it. Pearls only form after a pearl-sac has been formed, which is formed out of the interior or exterior epithelium of the mantle or gill plate. The secreted nacre of the epithelial cells of the pearl-sac increasingly coats the foreign object to form a pearl. There are seldom natural pearls between the mantle and shell, in the mantle, or in other soft tissues; these pearls tend to be small and irregular-shaped. Large pearls of round shape are very rare. When the irritant is stuck on the shell, forming a blister pearl is possible that only reflects the irritant on the exposed surface (Victor et al., 1995). 7.6.2 Cultured pearl formation Their creation is anthropogenic. In any form of pearl development two things are indispensable, the outer epithelium of mantle lobe and a nucleus. The human made nucleus is gently inserted into the oyster tissue through appropriate surgery procedure. Grafted oysters are returned to the water in order to keep growing. As the inner epithelium and connective tissue of the mantle is absorbed, the outer cells of the graft tissues divide and form a pearl-sac around the nucleus. The pearl-sac cells produce a nacre (mother-of-pearl) in concentric micro-layers over the nucleus and get nourished by the adjacent tissues. Nacre is made up of aragonite (0.29 0.60 mm thick) and conchiolin, an organic mucopolysaccharide binding layer that is alternately and interchangeably composed of these components. Farmed pearls recreate the same process as nacre deposition and creation of pearls. A covering a few of the nuclei upon the inner of the shell gives half-pearls, the mantle epithelium forming a pearl-sac upon the top of the bare nucleus (Victor et al., 1995). 7.7 Harvest of pearls The pearl culture period is short in tropical India in comparison with temperate locations. It may take up to 12 months in pond culture, each pond varying in the duration of time according to the size and number of nuclei, the well-being of the mussels and the conditions of the pond. The pearls that are formed as a result of gonadal implantation or grafting of mantle tissue are affected by the mother mussel and the donor mantle graft, and have a colour of silvery white to golden yellow and deep pink. The harvesting involves either killing of the mussel or extracting of the pearls in live mussels at the end of the culture period (12~14 months). Even though the freshwater mussels can produce pearls of gem quality, the size, shape, and colour may change because of natural variation. Pearls that are harvested are often washed, whitened, or dyed to ensure uniformity and value addition (Victor et al., 1995).
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