Effects of different feeding rate on growth and condition factor of Chitala lopis

Chitala lopis, also known as giant featherback , is a fully protected fish species on Indonesian official list due to the susceptibility to exploitation. Several studies showed that the conservation of aquatic resources, such as giant featherback


Introduction
The Notopteridae family consists of the genera Chitala, Notopterus, Papyrocranus, and Xenomystus, with distribution across South Asia, Southeast Asia, and Africa (Maneechot et al., 2015).Furthermore, three Chitala species, including Chitala lopis (giant featherback), Chitala borneensis, and Chitala hypselonotus, have been reported to be native to Indonesia and are primarily found in Java, Sumatra, and Kalimantan (Nugroho et al., 2019).According to the Indonesian government regulation (Decree of the Minister of Marine Affairs and Fisheries no.1 of 2021), these species are fully protected along with Notopterus notopterus, thereby prohibiting the use except for study and development.Despite the protective measures, the exploitation of these Chitala species, locally known as belida, has persisted for decades due to the economic value (relatively expensive) (Khairul et al., 2020).To meet consumption demands, belida consumers have heavily relied on catches by inland fishermen, leading to a significant decrease in population (Mustafa et al., 2015).This decline can primarily be attributed to massive fishing and environmental gradation (Nugroho et al., 2020;Haniffa et al., 2017).Giant featherback is a superior fish commodity in several regions of Indonesia, including Jambi and South Sumatra (Anjarsari, 2020).Several studies also reported its usage as an indigenous fauna mascot, particularly in South Sumatra.
The abundance of fish in both natural and aquaculture environments significantly depends on the availability of food resources (Sukendi et al., 2019).In the initial stages of domestication program, growth and survival of captive-bred species often depend on live feed (Melanie et al., 2023).The provision of feed has been reported to play a significant role in achieving optimal levels of production (Yanuar, 2017).Wibowo (2011) stated that the dietary composition of giant featherback in the natural habitat primarily consisted of small fish and prawns.The giant featherback is a nocturnal species, which actively hunts for preys at night (Sunarno et al., 2015).Several studies showed that successful fish cultivation faced challenges related to appropriate feeding management, considering feed nutritional preference and feeding rate (Bassey and Ajah, 2010;Simanjuntak et al., 2017).The optimal feeding rate is an essential factor in the culture of freshwater fishes to reduce excessive expenses, with variations observed across species and different life stages (Md Mizanur et al., 2014).Although captive giant featherback has been predominantly fed with bay-caught fish and live shrimp, there is a lack of information regarding the optimal feeding rate in the management.Therefore, this study aims to evaluate the optimal feeding rate of live feed on growth, survival rate, and condition factor of the firstgeneration experiment (G1) of giant featherback.

Experimental design
This study was conducted from May-July 2023 at the small-scale fish cultivation group (Pokdakan) Ulam Jaya, Banyuasin Regency, South Sumatra.Furthermore, the first generation of fish was collected from the natural reproduction of broodstock in the earthen ponds, and the broodstock of belida was obtained from South Sumatra.Belida progeny used comprised 27 individuals with a length and weight of 22.18±0.42cm and 41±3.85 g, respectively.A complete randomized design consisting of two different treatments and one control was used.Fish was randomly selected into three different groups replicated three times and reared in nine net cages with dimensions of 1 x 1 x 1.2 m, which were installed in a 10 x 10 x 2 m earthen pond.The stocking density of the samples in each group was three fish per cage.The first group was fed with bycatch of approximately 5% of the total weight used as control (T0).The two other groups were fed with freshwater shrimp (Caridina sp.) with two different feeding rates of 5% (T1) and 7% (T2).Fish was fed twice a day at 8:00 and 16:00., and the daily consumption of feed ability was estimated to be between 3-10% of the total body weight (Sunarto and Sabariah, 2009).

Observations and measurements of fish
Fiant featherback in each cage net (3 fish/cage) was sampled every 14 days and transferred to a plastic basin containing aerated freshwater.To avoid stress caused by handling, the samples were anesthetized using an anesthetic solution (Stabilizer, dose of 1 ml per 3 L of water) based on product protocol.Subsequently, fish size (total body length) was measured using a ruler (accuracy of 0.1 mm), and the total body weight was measured using a digital scale (Joil) with an accuracy of 0.1 mg.After measurement, all samples were returned to the cage nets and no mortality was observed during sampling activities.The observation of survival rate was carried out every day until the end of the study procedures.

Data calculation
Effects of different feeds on growth and survival performances of giant featherback were examined by calculating the following parameters.
Growth rate was calculated using absolute growth (g) and relative growth (%) was based on the formula proposed by Lugert et al. (2014).The formula for absolute growth (g) is presented below: The formula for calculating relative growth rate in percentage terms is as follows: Where: RGR = Relative growth rate (%) Wt = Final weight (g) Wi = Initial weight (g) The formula representing the survival rate follows Mustafa et al.,(2019): Where: SR = Survival rate (%) Nt = The quantity of fish that has been harvested No = The quantity of fish that has been stocked Growth pattern was predicted by length-weight relationship formula proposed by Khairul et al., (2020): W= aLᵇ Where: W = Total weight (g) L = Total length (cm) a = Intercept b = Slope Growth pattern followed the specified criteria: -If b = 3, hence, both length and weight growth is balanced (isometric).-If b < 3, hence, length growth is more dominant weight growth (negative allometric).-If b> 3, hence, weight growth is more dominant than length growth (positive allometric).
Condition factor analysis was carried out to assess the health and growth of organisms, which was influenced by the carrying capacity of the environment (Muslimin et al., 2022).The condition factor was calculated using the formula of Jonsson et al. (2012): Where: CF = Conditional factor W = Body weight (g) L = Total length (cm)

Data analysis
Statistical analysis was carried out to compare effects of different feed on absolute growth, relative growth, length-weight relationship, condition factor, and survival rate using Analysis of Variance (ANOVA), followed by Duncan tests.Furthermore, statistical regression tests were used to calculate data on growth pattern, and all analyses were performed using the IBM SPSS version 23.0.

Growth rate
Fish growth during the study period is presented in Table 1.T1 had the highest average absolute growth and survival and was not significantly different (29.9 ±6.38 g and 78 ±11%).However, the highest relative growth rate value in T1 differed significantly (76.28 ± 18.61%) from others.The lowest absolute growth, relative growth rate, and survival rate parameters were recorded in T2 (12.1±2.05g, 8.66±0.88,and 33±0).To, T1, and T2 values were different because T0 was the control value using fish feed with a concentration of 5%, while T1 and T2 used 5% and 7% shrimp feed, respectively.

Growth pattern
Figure 1 shows growth pattern and regression between weight and length at the beginning and end of the study.Growth pattern at the beginning of the study showed a slope value (b) (0.54) and the R 2 value was low (0.03).Meanwhile, at the end of the study, the slope increased (4.17) with a moderate R 2 value (0.66).

Conditional factor
Figure 2 shows a graph of conditional factors at the beginning and end of the study.The results showed that T2 had the highest value at the beginning of the study (0.51), while the lowest value was recorded in T1 (0.37), with no significant difference.At the end of the procedure, the highest and lowest conditional factor were found T2 (0.78) and T0 (0.51), respectively, with a significant difference.

Discussion
The biological conditions of fish, such as growth, health, and reproduction were influenced by the nutrient content of the food.Energy, anabolism, essential amino acids, and growth were often supported by feed nutrients (Halver and Hardy, 2003;Bertucci et al., 2019).Furthermore, the treatment used in this study comprised freshwater shrimp (Caridina sp) and food, namely Seluang fish (Rasbora sp).In this experiment, live feed consisting of 5% freshwater shrimp (Caridina sp.) relative to fish weight showed better growth compared to other treatments.The protein content of Caridina sp was estimated at approximately 56% (Mugo-Bundi et al., 2013), while Rasbora sp contained approximately 15.29% protein (Munthe et al., 2016).This was in line with Nafidza and Djumanto (2019) in Rawa Pening Semarang, where the highest preference for belida was freshwater shrimp due to the high protein content compared to others.Giant featherback fed with a protein content of 35% exhibited significantly higher growth (Hien et al., 2022).The protein value of featherback meat was 25-40% (Hien et al., 2022), showing that the samples fed with Caridina sp. in T1 and T2 had higher levels compared to Rasbora sp.Therefore, Chitala sp fed with the shrimp had more optimal growth due to the fulfillment of protein requirement.The difference in protein content could cause varying weight values, particularly in relative growth, which had a significantly effect, as shown in Table 1.Effect of differences in the protein content of treatment on fish growth had also been reported in other studies, particularly among Chitala chitala and Oreochromis niloticus (Hien et al., 2022;Mugo-Bundi et al., 2013).According to Nafidza and Djumanto (2019), crustaceans were the main feed for the other species of featherback Notopterus notopterus, as shown by the presence of shrimp (31%) and small fish (26%) in the digestive system.However, this composition could vary based on the level of feed availability in the environment.Sunarto and Sabariah (2009), the daily consumption of carnivorous fish ranged between 5 and 10% of the total fish weight.Feeding rate of 5-7% of shrimp on featherback could be tolerated in this study and a 5% composition treatment provided a positive impact on growth.However, further studies were required to determine an optimal daily feeding range.
Fish growth pattern was changes in size and the relationship between the weight and length of the samples at a particular time.In this study, growth pattern showed different trends at the beginning (negative allometric) and end of the experiment (positive allometric) (Figure 1).According to Mitra et  Sarkar et al. (2008), pattern in Chitala sp. was tentative.Growth phase of Chitala sp. could be divided into four stages (Mitra et al., 2014), including yolksac (age 1-8 days with a total length of 10.2-13.2mm), preflexion (age 9-12 days with a total length of 13.81-16.9mm), flexion (age 13-20 days with a length of 17.89-25.25mm), and post flexion (age 20-30 days with a total length of 21-30 mm).Growth pattern in all was positive except isometric in the postflexion phase.This study showed that similar growth pattern could be caused by factors, such as feed availability, population density, age, maturity, and genetics (Muslimin et al., 2022).
The condition factor, also known as the condition coefficient or length-weight factor, delineated the biotic and abiotic carrying capacity of the environment, influencing the phenotype of fish (Fafioye and Ayodele, 2018).Despite the generally positive allometric growth pattern observed in this study, the condition factor had a relatively low value of <1.Previous studies on Chitala in natural inland waters reported varying condition factors, such as 0.7 and 0.9 (Chandran et al., 2020).This diminished parameter could contribute to the flat and elongated shape exhibited by Chitala.

Conclusion
In conclusion, the consumption of freshwater shrimp (concentration 5% of weight) had a more optimal effect on growth factors (weight gain) and survival compared to other feed treatments.Furthermore, growth pattern and condition factor showed a positive trend during the cultivation process.

Figure 1 .
Figure 1.Growth pattern at the beginning (A) and end of the study (B).b is growth pattern and R2 is the regression value between length and weight.

Figure 2 .
Figure 2. Conditional factors at the beginning of the study (blue) and at the conclusion (yellow) of the study.The superscript shows significance (p<0.05).

Table 1 .
The average and standard error of Chitala sp growth rate during the study (T0, T1 and T2).