International Journal of Aquaculture, 2024, Vol.14, No.1, 9-19 http://www.aquapublisher.com/index.php/ija 9 Research Article Open Access The Effect of Density and Temperature on Survival and Fatty Acid Profiles of Copepods (Thermocyclopsp.) Gerald Kwikiriza 1,2,3, Ronald Semyalo 3 , Gladys Bwanika 3, Alex Barekye 2, Justus Kwetegyeka 4, Andrew Arinaitwe Izaara 5, IvanAbaho6 1 Institute of Integrative Nature Conservation Research, Department of Integrative Biology and Biodiversity Research, University of Natural Resources and Life Sciences, Gregor Mendel Str., 331080, Vienna, Austria 2 Kachwekano Zonal Agricultural Research and Development Institute, National Agricultural Research Organization (NARO), P. O. Box 421, Kabale, Uganda 3 Department of Zoology, Entomology and Fisheries Sciences, College of Natural Sciences, Makerere University, P. O Box 7062, Kampala, Uganda 4 Department of Chemistry, Faculty of Science, Kyambogo University, P.O. Box 1, Kyambogo, Uganda 5 Mukono Zonal Agricultural Research and Development Institute, National Agricultural Research Organization (NARO), P.O. Box 164, Mukono, Uganda 6 Bulindi Zonal Agricultural Research and Development Institute, National Agricultural Research Organization (NARO), P.O Box 101, Hoima, Uganda Corresponding author: ronald.semyalo@mak.ac.ug International Journal of Aquaculture, 2024, Vol.14, No.1 doi: 10.5376/ija.2024.14.0002 Received: 18 Sep., 2023 Accepted: 30 Oct., 2023 Published: 10 Jan., 2024 Copyright © 2024 Kwikiriza 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: Kwikiriza G., Semyalo R., Bwanika G., Barekye A., Kwetegyeka J., Izaara A.A., and Abaho I., 2024, The effect of density and temperature on survival and fatty acid profiles of copepods (Thermocyclop sp.), International Journal of Aquaculture, 14(1): 9-19 (doi: 10.5376/ija.2024.14.0002) Abstract Cyclopoid copepods (Thermocyclopsp.) have the nutritional attributes of an ideal diet for fish larvae. However, long-term production and availability of copepods for feeding larval fish in hatcheries remain a challenge. The present study investigated the effect of density and temperature on survival and fatty acid profiles of Thermocyclop sp. at densities: 1 000, 3 000, and 5 000 individuals/L and temperatures: 4 °C, 8 °C, and 12 °C. A log-rank test showed a significant difference between the percentage survival of Thermocyclop sp. at 12 °C and 4 °C (P<0.001) and a significantly higher survival at 1 000 than at 5 000 individuals/L (P<0.001). Generally, saturated fatty acids (SFAs) were dominant compared to monounsaturated fatty acids (MUFAs) and polyunsaturated fatty acids (PUFAs). For essential fatty acids, no significant differences were observed between storage temperatures on the 7th and 14th days of the experiment. The results demonstrated that at least a 50% survival rate is obtained when these organisms are stored at 12 °C with a density of 1 000 individuals/L for 14 days, with no significant changes in fatty acid profiles. Further studies are necessary to determine the effect of increased storage conditions, perhaps with aeration, on storage time. Keywords Thermocyclopsp.; Density; Temperature; Survival; Fatty acids Over the last decades, climate change, illegal, unregulated, and unreported (IUU) fishing, and pollution have led to the depletion of fisheries resources (Nakiyende et al., 2023). For example, overfishing results in the removal of a large number of fish from the population. This leads to a decline in the overall size and abundance of the targeted fish species, making it difficult for the population to sustain itself (Kwikiriza et al., 2023a). Presently, there is an increased global investment in aquaculture, seen as an alternative for enhancing fish production to meet the demand-supply gap arising from the continual decline in capture fisheries (Abaho et al., 2016; FAO, 2022). By 2021, the leading African countries contributing to aquaculture production were Egypt (72.20%), followed by Nigeria (12.60%), and Uganda (6.33%) (FAO, 2022). Even though global aquaculture continues to increase, the African contribution remains low, estimated at 2.7% (Adeleke et al., 2020; FAO, 2022), and this is attributed to many factors, majorly; lack of access to quality and affordable feeds (Izaara et al., 2020) and poor-quality seed among others (Kwikiriza et al., 2023b). Poor-quality fish seed results in lower survival rates in fish farms, thus increasing financial losses for farmers who invest in fingerling production. To boost aquaculture, there is a need to invest in raising quality fish seed, and one way to achieve this is by enhancing larval nutrition. Larval nutrition poses a major bottleneck in aquaculture hatcheries worldwide, impeding the full commercialization of most domesticated fish species (Abate et al., 2016). Developing larvae are very small, fragile, and have poorly developed physiological systems, which limits their ability to efficiently utilize formulated feeds, resulting in poor growth and survival rates (Kimmerling et al., 2018). Presently, aquaculture production relies on live food organisms like Brine shrimp (Artemia sp.), rotifers, and copepods to meet the nutritional requirements of these small larvae (Olivotto et al., 2010; Kimmerling et al., 2018). The availability of live starter organisms like Brine
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