Borneo Journal of Marine Science and Aquaculture Volume: 04 | Dec 2020, 57 - 61 57 Effect of temperature on population growth of copepod, Euterpina acutifrons Marlena Amatus, Najamuddin Abdul Basri, Rossita Shapawi & Sitti Raehanah Muhamad Shaleh* 1 Borneo Marine Research Institute, Universiti Malaysia Sabah, Jalan UMS, 88400 Kota Kinabalu, Sabah, Malaysia * Corresponding author: sittirae@ums.edu.my Abstract This study was aimed at determining the optimum temperature for culturing the copepod, Euterpina acutifrons. The trial was conducted for 10 days in chambers at temperatures of 25⁰C, 27⁰C, 29⁰C and 31⁰C. Ten adult individuals of the copepod were randomly collected and placed into three replicate experimental flasks for each treatment. Throughout the trial, the salinity, light intensity, and photoperiod were maintained at 30 ±2psu, 100molm -2 s -1 and 12:12 light-dark cycle, respectively. The copepods were fed with 80,000cell/ml Isochrysis sp. daily. At the end of the trial, the total numbers of E. acutifrons nauplii, copepodites and adults were determined and counted using Sedgwick-Rafter. The highest population was found at 27⁰C with mean total population of 800±100 individuals from an initial of 10 individuals. This was followed by those reared at 25⁰C and 29⁰C where the population counts were 700±100 individuals and 367±115 individuals, respectively. At the 31⁰C, all the copepod specimens were found dead on day 5 th . Statistical analysis showed that the temperature had a significant effect (P<0.05) on the population growth of the copepod. The population of nauplii was higher in lower temperature (25⁰C) set compared to the one at higher temperature (29⁰C). However, the copepodite number was greater at 27⁰C. Growth of the copepod was highest at 27⁰C (0.438K) followed by sets at 25⁰C (0.425K) and 29⁰C (0.361K). Based on the results of thi s analysis, it is suggested to culture copepod at temperature 25⁰C for nauplii production and 27⁰C for producing more copepodites. Keywords: Aquaculture, Live Feed, Copepod, Temperature, Population growth ----------------------------------------------------------------------------------------------------------------------------------------------- Introduction A major concern in successful larval rearing of commercial fish is about the appropriate type of live feed at the first feeding phase (Ohs et al., 2009). It is the most critical period in the larviculture that determines the survival of the fish and success of the culture system (Agh and Sorgeloos, 2005). During this phase the marine fish larvae require a live feed of suitable nutritional value and size range (Ohs et al., 2009). In South East Asia, aquaculture of most species involves capturing young or immature wild stocks and culturing them to marketable sizes. This is an unsustainable practice that contributes to depletion of wild stocks. The viable alternative is establishing the full cycle culture in the hatchery and producing seeds to support aquaculture development. However, the larviculture of most of the species remains a major bottleneck in this effort. Larval mortality is high due to gap in knowledge of nutritional requirement of the larvae and difficulty in producing the required feed suitable for the first feeding (Sorgeloos and Leger, 1992). At first feeding, the mouth gap of most larvae is small which limits the size of food the larva can capture to survive (Chesney, 2005). Formulated feed, though nutritionally adequate, have been able to replace live feed due to problems pertaining to their digestibility and palatability (Kolkovsky, 2001). The use of rotifer as live feed has revolutionized the development of full cycle culture of many species. The brine shrimp, Artemia, is also used as food for many marine fish larvae due to its commercial availability. However, it has been reported that some species of marine fish do not survive on rotifers and Artemia (McKinnon et al., 2003; Chesney, 2005; O’Bryen and Lee, 2005). These species include Epinephelus sp. (Knuckey et al., 2000; McKinnon et al., 2003; Toledo et al., 2005), Pagrus sp. (Payne, 2000) and Lutjanus sp. (Ogle et al., 2005; Phelps et al., 2005; Su et al., 2005). Comparatively, the copepod provides good results (Stottrup, 2000; Lee, 2003). The advantages of copepods over rotifers and Artemia include size range at the naupliar, copepodite or adult stages. Any of these can be chosen according to the mouth size of the larvae (Chen et al., 2006). Their nutritional content should match the requirements of marine fish larvae (Stottrup, 2000; Evjemo et al., 2003; McKinnon et al., 2003) especially in the amounts of DHA and EPA (Bell et al., 2003). Moreover, their swimming behaviour can stimulate a stronger foraging response in fish larvae (Stottrup, 2000). Several species of copepods have shown potential in aquaculture particularly in rearing marine fish larvae. The preferred species belong to the genera Acartia, Centropages, Eurytemora, Euterpina, Tigriopus, Tisbe, Oithona and Apocyclops (Stottrup, 2003). The benefits of using copepods as live feed are well known, but reliable supply of copepods remains as a challenge for aquaculture due to technical constraints and it still remains a work in progress (Stottrup, 2000, Hagiwara et al., 2001). The major drawback of copepods as live feeds for larviculture compared to Artemia