Cultured sand sea cucumber growth with different water exchange systems Pertumbuhan teripang pasir yang dibudidayakan dengan sistem pergantian

Sand sea cucumber ( Holothuria scabra ) is a high economic value as a food source. Sea cucumbers contain beneficial bioactive compounds for health. This study determined the sea cucumber growth cultured in an integrated multitrophic aquaculture (IMTA) with different water exchange systems in Lifuleo waters from October to December, 2020. This study was performed in an experimental method with three different exchange system treatments and three replications, namely once every 2 days (tank A), every day (tank B), and water circulation every day (tank C). Briefly, sand sea cucumbers with 116.72 ± 117.91 g body weight and 11.06 ± 11.83 cm length were maintained for 45 days with different water exchange systems and fed with Eucheuma cottonii . The results showed that the best water exchange systems to increase sand sea cucumber production was tank A with 100% survival rate, 1.84 ± 0.06%/day specific growth rate, and 1714.96 ± 34.13 μm length growth rate. The water quality parameters were also optimal during the sand sea cucumber with the integrated system.


INTRODUCTION
Sand sea cucumber (Holothuria scabra) is one of the sea cucumbers with high economical value and exploited commercially in tropical area, including Indonesia (Jasmadi, 2018). The sea cucumber distribution is extremely wide in several waters with 1-40 m depth (Matrutty et al., 2021). This sea cucumber lives in a shallow or an intertidal water habitat, besides in a deeper water with sea grass, sandy, and muddy substrates (Al Rashdi et al., 2012;Hamel et al., 2013;Purcell, 2012). Sea cucumbers have high protein content and are sold among Rp 400.000.00-1.200.000.00/ kg as dried product (Tomatala et al., 2018a). In addition, sea cucumbers are one of the bioactive compound sources that can be beneficial for health (Albuntana et al., 2011).
Sea cucumbers that are relatively easy to find in a shallow water area cause these organisms are highly exploited in nature without noticing the size and age (overfishing). Moreover, the Echinodermata species such as sea cucumbers are a food source with various important nutrient values (Satria et al., 2014). Good stock management absence impacts on the low population in nature around the world that causes these species are included as endangered species in the IUCN Red-List of Threatened Species (Hamel et al., 2013). This condition encourages the culture activity with technological approach as an effort to support the population recovery and supply sea cucumbers with good quality and sustainability (Juinio-Menez et al., 2012).
Sand sea cucumber is a tropical sea cucumber type that can commonly be cultured (Purcell et al., 2014b). The culture system has many been developed, namely pen, pond, and floating-net cage cultures. Several countries have developed the sea cucumber culture, such as Australia, Philippines, Vietnam, Madagascar, Fiji, and Indonesia with various scales (Bowman, 2012;Duy, 2012;Firdaus et al., 2017;Hair et al., 2016;Juinio-Menez et al., 2012;Lavitra et al., 2010;Olavides et al., 2011). A good location site selection determines the culture activity success. Furthermore, the seed and feed supplies are key factors to support the culture development system and production.
IMTA system is an integrated-system that combines two or three culture commodities, whereas nutrient/feed waste from the high-level animal is consumed by the low-level animal to improve the growth rate. The IMTA system is applied to answer challenges about the culture activity issue on the aquatic environment that contains sedimentation and aquatic nutrient enrichment (Erlania & Radiarta, 2015;Alexander et al., 2016). The IMTA culture system is aimed to balance the ecosystem by rearing various species with different trophic levels that can improve the economic-added value and reduce the culture waste (Chopin et al., 2010;Yuniarsih et al., 2014). Studies regarding the IMTA system application have many been performed, namely: (1) nutrient utilization aspect from several culture commodities (Lander et al., 2013;Tang et al., 2015;Irisarri et al., 2015), (2) commodity productivity aspect (Neori et al., 2000;Erlania & Radiarta, 2015), and (3) social and economy aspects (Martinez-Espineira et al., 2015;Alexander et al., 2016).

Location and Period
The study was conducted on October-December, 2020 for 45 days. This study was performed on a floating net cage system in Lifuleo waters, Kupang Barat Sub-district, Kupang District, East Nusa Tenggara.

Experimental design
This study was an experimental field with a completely randomized design with three different water exchange systems and three replications, namely: Tank A: Sea cucumbers reared with water exchange once every 2 days Tank B: Sea cucumbers reared with water exchange everyday Tank C: Sea cucumbers reared with water circulation everyday

Equipment and Materials
The culture media used a floating-net cage equipped with wood block, board, plastic drum, nylon rope, drum-knotting rope, anchor rope, webbing, nail, saw, wood, wooden chisel, silicon glue, bolt, ring, carbide, anchor drum, threaded iron, anchor-welding, cement, sewing-needle, sewing-net, blinkers, battery, epoxy glue. For materials, sand sea cucumbers were used.

Seed stocking
The sea cucumber seeds as experimental organisms were obtained from the fishermen around Lifuleo waters. The sea cucumber seeds had 116.72 ± 117.91 g weight and 11.06 ± 11.83 cm length. Total number of seeds used was 225 sea cucumbers with the assumption that the pond carrying capacity for cucumber culture was 250 g/m 2 , thus the stocking density was applied at 1 sea cucumber/m 2 (Agudo, 2012).

Sample collection
Sea cucumber seed sampling was performed once every 15 days. The samples were taken at 10 seeds from each treatment for length and weight measurements.

Water quality measurement
Water physical and chemical parameters observed during the experiment period included temperature, pH, and turbidity level. The measurement was performed every 7 days and accumulated every 15 days.

Parameters
Parameters observed contained survival rate (SR), specific growth rate (SGR), and length growth rate (LGR).

Survival rate
The survival rate was calculated with the following formula (Effendie, 1997):

Specific growth rate
The specific growth rate was an individual weight growth in percentage that could be calculated using (Huisman, 1987): Note: SGR = Specific growth rate (%/day) Wo = Sea cucumber weight on initial rearing (g) Wt = Sea cucumber on t-rearing period (g) t = Rearing period

Length growth rate (LGR)
The length growth rate during rearing period was calculated using the formula (Allen et al., 2006): length growth rate data were analyzed with an analysis of variance at 95% confidence level. If there was a significant different found among the data, the data were then analyzed using the Tukey test.

Survival rate
The survival rate calculation results in sand sea cucumber (H. scabra) from three water exchange treatments with IMTA system for 45 days is presented in Figure 3.
Based on Figure 3, the survival rate data present the ideal condition in all treatments by reaching the value at 100%. Factors affecting the survival rate value are determined by feed quality and environmental condition (Purcell et al., 2012).

Specific growth rate (SGR)
Growth is length and weight increase in a certain period due to mitotic cell division (Spikadhara et al., 2012). The specific growth rate results in sand sea cucumbers from three water exchange treatments with IMTA system for 45 days of rearing period is presented in Figure 4.

Data analysis
The data collected in this study contained primary and secondary data. Primary data were collected through survey and direct measurement in the field. Survival rate, specific growth rate,  Different water exchange treatments showed a significant different value on the specific growth of sand sea cucumbers (p<0.05). The highest specific growth rate value was obtained from the tank A at 1.84 ± 0.06%, while the lowest value was found in the tank C at 0.63 ± 0.05%. Soil substrate or texture is an extremely important component for organisms (Altamirano et al., 2017). Different specific growth rates on sand sea cucumbers were thought due to rare water circulation, which caused a higher substrate deposition on the tank base and promoted a higher growth rate in sea cucumbers.

Length growth rate (LGR)
Sea cucumber is one of the biota that lives spreading around the waters. This organism relatively lives on stagnant and clear waters. The habitat types that are mostly preferred by sea cucumbers are sandy mud, sea grass, and coral reef habitat (Kritsanapuntu et al., 2014). For fulfilling the culture management of sea cucumbers well, an aspect that should be noticed in culture activity is land suitability, before being used as a culture location. Also, the sea cucumber culture location should be free from pollution and fulfill the water quality standard for the cultured organisms.
Based on Figure 3, the calculation results of length growth rate obtained a significant different value (p<0.05). These results were similar to Kaenda et al. (2016). The highest length growth rate value was found in the tank A at 1714.96 ± 34.13 µm/day, while the lowest value was obtained from the tank C at 615.70 ± 5.71 µm/day. Low sea cucumber growth in tank C treatment (daily water circulation) was thought due to sediment condition that caused the sea cucumber stress.

Water quality
One of the aspects that should be noticed in performing the culture activities is land suitability for culture site, whereas sea cucumber culture should be free from pollution and fulfill the water quality standard for culture organisms. Temperature is a physical parameter that has a role in controlling the water ecological condition (Sithisak et al., 2013). Temperature fluctuation is highly determined by several factors, namely area height, rainfall, feed, and competitors or predators (Hartati et al., 2017). Temperature changes can commonly affect physical, chemical, and biological process occurred in the water column. Optimum water temperature range for sea cucumber seed rearing is 29-30°C with the salinity of 32-35 mg/l, and pH of 6.9-8.5 (Indriana et al., 2016;Indriana et al., 2017). Table  1 presents the temperature range in Lifuleo waters among 27.5-30.0°C, which were tolerable for sea cucumbers (Mazlan & Hashim, 2015). pH indicates the acid and base condition  balance (Nurussalam et al., 2017). pH < 7 (acid) can cause low dissolved oxygen consumption, while pH >7 (base) can cause increased ammonia (NH3) level toxic for cultured organisms. Optimum pH range for sea cucumber seed rearing is 6.9-8.5 (Indriana et al., 2016;Indriana et al., 2017). The average measurement results of water pH level during the experiment period were 7.3-7.8. Sea cucumber can live in water with the pH of 6.5-8.2 (Mazlan & Hashim, 2015). Turbidity describes the water optical characteristic that can be determined based on the amount of light absorbance and refraction by materials in the water. Turbidity occurs due to the existence of suspended and diluted organic and inorganic materials, such as mud and sand. The results showed the turbidity level in the three treatments were 1.80-3.10 NTU.

CONCLUSION
The development of sand sea cucumber (H. scabra) culture is highly possible in Lifuleo waters. Different water exchange treatments for sand sea cucumber culture with IMTA system provides a significant different on survival rate, specific growth rate, and length growth rate of the sea cucumbers.