Nursery of sand lobster, Panulirus homarus (Linnaeus 1758) in rearing tanks with some shelter combinations

. (cid:3) The addition of the right combination of shelters to lobster farming can reduce cannibalism and increase survival rates. This study aims to find a suitable shelter combination for Scalloped spiny lobster reared in a fiberglass tank. The study was conducted in 12 fiberglass tanks 1 m 3 in volume, with an initial lobster puerulus weight of 0.26 ± 0.024 g and a density of 100 /tanks. The combination of shelters tested is roster brick (A); shading net (B); roster brick and seaweed Gracillaria sp. (C); and shading net and seaweed (D). The parameters observed were survival rate, body length, body weight and hemocytes. Results showed that the best survival rate at treatment C (36.3 ± 10.54%), followed by A (33.3 ± 5.77%), D (25.0 ± 5.57), and lowest at B (14,3 ± 4,04%) (P<0.05). The final body weight and total length did not significantly different (p>0.05). The highest total hemocytes at treatment C (616.5±67.254 cell/ml), followed by A (583.4± 59.434 cell/ml), D (572.6±56.324 cell/ml), and lowest at B (459.6±45.344 cell/ml). The shelter combination of roster brick and seaweed ( Gracillaria sp.) is better than another treatment because it can produce a better survival rate.


Introduction
The world market demand for spiny lobster continues to increase yearly.The high market demand for scalloped spiny lobsters will pressure the preservation of their stocks in the wild [1].Overfishing pressure is indicated by the decrease in the number of catches [3] and the smaller size of lobsters caught in some locations in Indonesia [4].As a result, the latest data shows that the lobster production trends in some areas are static [5].Hence, it is necessary to develop lobster aquaculture farming in Indonesia to solve the problem.Scalloped spiny lobster has the potential to be developed into a marine aquaculture commodity because it is supported by the potential for abundant sources of wild seeds [2].
One of the challenges in lobster farming is the high mortality rate due to cannibalism [6].The highest levels of lobster cannibalism occur in post-puerulus stadia up to 30 g in weight because lobsters will molt every 10-20 days in this phase.The occurrence of cannibalism because when molting lobsters, the condition is very weak and easily preyed upon by other lobsters [7].Mortality rates and cannibalism can be reduced by providing shelters for lobster culture [8].For rearing spiny lobster puerulus in floating net cages, net shelter is generally used [9], and for rearing in the tank PVC pipe shelter [10].Increasing the number of shelters to the optimal number has been shown to improve the survival of raised lobsters; shelter types of PVC pipe, bricks, cement sacks, or nets have been covered [11] [6]; shading net shelters of various sizes were tested [8].
Adding the right combination of shelters to lobster farming can reduce cannibalism and increase survival rates [10].Therefore, researchers are interested in observing the survival and growth of scalloped spiny lobsters against the provision of different shelters.This study aims to get a good shelter combination for sand lobster nurseries at the rearing tank.

Material and methods
The 12 fiberglass tanks with a volume of 1 m 3 were used in this study.The tanks were equipped with an aeration system and water circulation of as much as 100-200% of the total volume of water per day.Puerulus phase spiny lobsters weighing 0.26 ± 0.024 g were stocked with a density of 100 individuals per tank.The treatment was the difference in the shelter, namely roster brick (A); PE shading net at the size of 1 time of bottom area (B); roster brick and seaweed (Gracillaria sp) (C); and shading net and seaweed (D) (Figure .1).The study used a complete randomized design with three replicates, and collected data was analyzed using ANOVA.Lobsters were fed with a combination of dry pellets, particularly for spiny lobster feed, with a protein content of 46.5% at a dose of 2% biomass in the morning and fresh feed (fish and mussel 3:1) of 7.5% biomass in the evening.Fish and mussels used for feed are only taken meat cut into pieces of 2-3 mm given at once.
The parameters observed were survival rate, body length, body weight, and water quality by sampling every two weeks, while the total hemocyte count and brix in the last sampling.The survival rate is calculated from the number of lobsters still alive.Body length measurement using a digital caliper and body weight using a digital scale with an accuracy of .01g.The total hemocyte count and brix index were measured from hemolymph samples taken from the posterior of the 5th foot using a syringe volume of 1 ml 0.5 ml and added anticoagulant solution.The total hemocyte count is calculated using a hemocytometer under a microscope.Brix measurement uses a brix refractometer with an accuracy of 1%.Observation of the total number of hemocytes and blood sugar to determine the condition of their resistance is carried out at the end of the study.As supporting data, water quality parameters are measured by salinity, temperature, pH, ammonia, nitrates, and phosphates.

Results and discussion
Results of observations of the puerulus survival rate on sand lobsters on each shelter treatment tested for 14 weeks are presented in  The highest survival rate resulted in treatment C, roster brick and seaweed (36.3 ± 10.54%), followed by treatment A, roster brick shelter (33.3 ± 5.77%), then treatment D, shading net and seaweed (25.0 ± 5.57) and lowest B, shading net shelter (14.3 ± 4.04%).These results show that roster brick shelters or roster brick combined with seaweed are better for lobster puerulus than shading net only and a combination of shadowing net and seaweed shelter.The research of [12] show that using shelters in fiberglass tank can improve the survival of baby pearl spiny lobsters Panulirus ornatus and reduce the cannibalism of newly molted lobsters, but have no significant effect on growth.[12] reported low survival in P. homarus rearing in the tank without shelter but no significant growth differences.It was seen that 75% of lobsters were found occupying shelters during the day.[13] observed the crowding of Panulirus homarus lobsters inside PVC pipe shelters, which can reduce feed consumption, oxygen consumption, metabolism, and lobster growth.Shelters can use PVC pipes, brick breezeblocks, or nets.In the rearing of lobsters in the tank with an initial body weight of 2 grams for 70 days rearing period, the shelters of PVC pipes can increase the survival rate by 25%, while with roster brick can be increased by 20%, and nets increase 12% compared to without shelters [14].
The ratio of shelters also affects the survival of lobster rearing; the use of shelters of 4:5 is better than the ratio of lower or higher [15].The use of shelters in lobster farming can reduce cannibalism; however, the size and material of the shelter greatly influenced the final survival rate ( [16] [17]).Most shelters use artificial materials, such as cement, plastic, PVC pipes, or wood ( [18] [17]).[19] reported that P. argus would change favourability for the type and size of the shelter as it grew as it related to its level of comfort.[19]  The advantage of the seaweed shelter is that it can grow quickly and does not need to be supplemented.Seaweed, commonly used in polyculture or integrated multi-trophic level aquaculture (IMTA) systems, is common and has a positive effect on water quality.[10] the use of seaweed for water quality control.Sumbing et al. (2016) used Kappaphycus alvarezii seaweed (red algae) in the nursery of pearl lobster of P. ornatus for the IMTA system.They produced a survival rate of P. ornatus as high as 90% during a 10-week trial.[20] culturing Kappaphycus alvarezii and P. ornatus in different tanks; K. alvarezii used for water quality control in the systems.[21] reports that seaweed has the potential as a biological filter for reduction from eutrophication.
In Table 1 and Figures 3, 4, and 5, it can be seen that the growth of the total length, carapace length, and body weight of the lobster did not significantly differ (p<0.05) between treatments.The highest increase in length and weight in treatment B, where at the end of the study reached the size of the carapace length, total length, and body weight of 26.5 ± 1.63 mm; 55 ± 5.37 mm and 6.28 ± 1.673 g; followed by treatment C (26 ± 1.4 mm, 54 ± 4.91 mm, and 6.16 ± 1.306 g), treatment A (26 ± 1.62 mm, 53 ± 5.18 mm and 5.79 ± 1.473g) and lowest in treatment D (23.0 ± 1.1 mm, 52 ± 4.90 mm and 6.14 ± 1.257 g).Some studies have shown that seaweed can provide an additional feed source for lobsters; [17] reports that P cygnus feeds on red algae.[22] [23] found that P. homarus can eat some algae.[24] reports that post-larvae chemical sensing of P. argus is interested in algae.Seaweed shelters are relatively flexible for different sizes of lobsters, while artificial shelters have limitations for different size ranges.Lobsters prefer darker and solitary; typically, lobsters in young stadia spend more time hiding in shelters than adult lobsters.Adding shelters to lobster farming will increase the life ratio and reduce cannibalism [25].Adding shelters in lobster rearing aims to decrease predation, but a combination and type of shelter can reduce predation; with increasing size, lobsters will differ in preference for shelters [17].Most lobsters prefer artificial shelters made of cut cement, clay, pipes, or bamboo [26] [17].
The research results [27] showed that the use of shelters in lobster rearing in the tank has no significant effect on growth; it also reported that the rearing of P. homarus in the tank with differences in shelter use did not result in significant growth differences.This study used a density of 100 ind.per tank, which is still the optimal density.On rearing in the tank, the research results of [28] at P polyphagus rearing gained an optimum density of 50-100 heads/m 2 .The research of [29] on P. ornatus at densities of 14, 29, and 43/m 2 , showing no significant difference [16], suggests obtaining good growth in the post-puerulus nursery of P. cygnus with a 100/m 2 density.[16] suggested that the rearing of P. cygnus from puerulus with an initial density of 50 ind./m 2 be further gradually reduced to 25 ind./m 2 after the first year and 20 ind./m 2 the following year.Jones et al. (2001) also reported on the rearing of P. The results of the examination of the total number of hemocytes or total hemocyte count (THC) of lobsters (Table 2) can be seen that the highest in the treatment C (roster brick and seaweed) [(616.5±67.25)x 10 4 cells/ml] followed later on A (shelter roster brick) [(583.4±59.43) x 10 4 cells/ml], D (combination shading net net and seaweed) [(572.6±56.32)x 10 4 cell/ml] and the lowest at B (shading net) [(459.6±45.34)x; 10 4 cells/ml] but statistically not significantly different (p>0.05).This indicates that lobsters' stress levels and health conditions in all treatments are not entirely different.The total number of hemocytes or the total hemocyte count (THC) and brix index are considered indicators for monitoring stress/health conditions in lobsters (Lorenzon et al., 2001).Three types of hemocytes are commonly reported in crustaceans: hyaline cells, semigranulocytes, and granulocytes [30][31][14] [32].Environmental parameters such as temperature, salinity, oxygen, ammonia content, and pH significantly affect the immune system of lobsters [33].A significant decrease in THC was reported in P. homarus exposed to lower salinity (20 ppt) and higher salinity (45 ppt) as well as too low pH (pH 5) or high (pH 9.5) which significantly reduced THC and opportunistic pathogen (PO) values at lower and higher salinity and pH or under pressure, and susceptibility to opportunistic pathogens is likely high at extreme salinity levels [34].Reduction of THC in lobsters exposed to high ammonia levels will likely decrease the potential for phagocytosis and other antimicrobial abilities.Haemocyte counts below 4x10 6 cells/ml have been reported to indicate poor health in lobsters [35].Hunger for three weeks resulted in a significant decrease in THC in P. homarus, suggesting a direct relationship between hemocyte count and the nutritional status of lobsters ([36] [34].Direct transportation over long distances significantly decreases THC in P. homarus, indicating a decrease in immunity status.The results of observations of water quality of maintenance media (Table 3) found that the quality of water (ammonia, nitrite, phosphate, pH, Do, temperature, salinity) in the four treatments was almost the same, where ammonia 0.0442-0.0904 mg / L; nitrite <0.0087 mg / L, phosphate 0.0110 -. 0.0526 mg/L, pH 7.9-8.2;Do 5.1-5.9,Temperature 28.8 -29.7 o C and salinity 33-34 ppt.The quality of such water is still considered a worthy value for the growth of scalloped spiny lobsters.The research results of [37] show that sand lobsters can live well in water conditions at 25.5-29.5 o C, pH 7.5-8.5, and salinity of 25-35 ppt.The research results of [26] [8] show that the optimum salinity for the life and growth of scalloped spiny lobsters is 30-35 ppt.According to [38], cultivating sand lobster in a cage system can do well in the seasonal salinity range between 25-35 ppt.
From the value of the lobster hemolymph brix index (Table 2) it can be seen that the highest in treatment C (shelter roster brick and seaweed) (18.56±3.13%) followed by A (shelter roster brick) (18.2±3.65 %), D (combination of shading net and seaweed) (17.54±2.24%) and the lowest in B (shading) (16.43±2.6%);but statistically it does not significantly different (p>0.05).In the lobster industry, the Brix index is routinely measured from hemolymph to select the health of global lobsters produced.Index brix is a biomarker more representative than some other hemolymph parameters in terms of describing the energetic conditions of spiny lobster [36].Indeed, brix index values are highly correlated with total hemolymph protein triglycerides, cholesterol, calcium, phosphorus concentrations, and lipase activity.Index brix is generally associated with several hemophilic biochemical factors such as cholesterol, calcium, phosphor, and lipase [39].To measure the lobster's health status, various physiological changes can be assessed by assaying total blood proteins with the Brix index [40].The brix index is also used to determine other parameters, such as suspected infected conditions or exposure to hazardous materials.Still, in general, it can be said that the brix index can be used to determine the quality of lobsters [41].

Conclusion
The difference in the combination of shelters in the lobster nursery in the fiberglass tank provides a significant difference in survival but not growth.The best is a combination of roster bricks and seaweed.The use of roster brick shelters gives better results than shading net shelters.Adding a combination with a seaweed shelter can increase spiny lobster production.From the results of this study, it can be recommended that in lobster nurseries, fiberglass tanks use a combination of roster brick and seaweed.

Fig. 1 .
Fig. 1.The lobster Panulirus homarus puerulus rearing fiberglass tank is equipped with a combination of shelters roster brick (A), shading net (B), roster brick and seaweed Gracillaria sp.(C); and shading net and seaweed (D).

Fig. 3 .
Fig. 3. Growth of total length of sand lobster on each treatment in 14 weeks rearing period (A: roster brick; B: shading net; C: roster brick and seaweed (Gracillaria sp.); and D: shading net and seaweed).

Fig. 4 .
Fig. 4. Carapace length growth on sand lobster of each treatment on rearing period in 14 weeks (A: roster brick; B: shading net; C: roster brick and seaweed (Gracillaria sp.); and D: shading net and seaweed).

Fig. 5 .
Fig. 5. Body weight growth on sand lobster of each treatment on rearing period in 14 weeks (A: roster brick; B: shading net; C: roster brick and seaweed (Gracillaria sp); and D: shading net and seaweed).

Table 1 .
reported that P. argus would change favourability for the type and size of the shelter as it grew because it The biological aspects and feed conversion ratio on a sand lobster nursery in rearing tanks with differences of shelter combination for 14 weeks.

Table 2 .
Total hemocyte and brix hemolymph of scalloped spiny lobster P. homarus on each treatment on maintenance for 14 weeks

Table 3 .
Water quality in Sand Lobster Nursery on each treatment on rearing period in 14 weeks