Effect of stocking density on growth and survival of the prawn Macrobrachium tenellum, cultured in a recirculating aquaculture system.
Research studies of M. tenellum stocking density have been carried out (Lopez-Uriostegui et al., 2014). However, the reported studies where performed in laboratory conditions or inside grow-out pond systems, and there is no information about the required stocking density to produce M. tenellum inside a recirculating aquaculture system (RAS). Available space for RAS is drastically reduced in comparison to traditional pond systems, and these recirculating systems usually present a minimum water exchange with a high flow rate (Ebeling & Timmons, 2012), conditions that could affect the optimum stocking density, since there have been reports that the water replacement rate could affect the growth of freshwater prawns (D'Abramo et al., 2000). This study aimed to evaluate the influence of different stocking densities on the growth performance, and survival of M. tenellum reared in a recirculating aquaculture system.
Berried females were captured and allowed to hatch in an aquaculture farm (Acuicola S.A. de C.V., Colima, Mexico) to obtain juveniles. Juveniles (0.78 [+ or -] 0.31 g) were transported to the experimental facility in a 500 L fiberglass tank with aerators. Upon arrival, individuals were held in a 20 [m.sup.3] tank and acclimated for 15 days to recirculating conditions. They were fed with marine shrimp commercial pelletized food (40% crude protein, Camaronina Purina, Mexico) with a 10% daily feed ratio. After acclimating time prawns were transferred to the experimental units in the required densities.
The experiment was performed within a 504 [m.sup.2] (18x28 m) polyethylene greenhouse in El Marques, Queretaro, Mexico (20[degrees]42'18"N, 100[degrees]15'36"W). The experimental system consisted of nine 500 L High-Density Polyethylene oval tanks (50x120x90 cm) connected to the same recirculating aquaculture system with a 1 [m.sup.3] reservoir, and an operating volume of 6 [m.sup.3] with a 2% daily water exchange. A canister biofilter with a UV light treatment was used to maintain the water conditions with full water filtration every 25 min. PVC pipes were provided as refuges for the prawns.
Water temperature ([degrees]C) was measured every 3 h during the experimental time using a Watchdog 100 datalogger (Spectrum Technologies Inc.). Dissolved oxygen (mg [L.sup.-1]) and pH were monitored daily using the multiparameter probe HQ40D by Brand Hach, USA (LDO101-05 sensor [O.sub.2]; PHC101-05 sensor pH). Every week analysis of ammonia (mg [L.sup.-1]), nitrates (mg [L.sup.-1]), and nitrites (mg [L.sup.-1]) in water was performed through spectrophotometric techniques using the spectrophotometer Hach DR/6000.
M. tenellum juveniles (n = 81; weight 1.71 [+ or -] 0.11 g) were randomly stocked in triplicate experimental tanks at densities of 10 ind [m.sup.-2] (T1), 6 individuals per tank; 15 ind [m.sup.-2] (T2), 9 individuals per tank; and 20 ind [m.sup.-2] (T3), 12 individuals per tank. The stocking densities used in this experiment were inside the range of a semi-intensive (10 ind [m.sup.-2]) to an intensive (20 ind [m.sup.-2]) culture systems (Lopez-Uriostegui et al., 2014). Parameters were obtained per area unit due to the benthic behavior of the species (D'Abramo et al., 2000), although the volumetric densities for this study are: T1 (12 ind [m.sup.-3]), T2 (18 ind [m.sup.-3]) and T3 (24 ind [m.sup.-3]).
The prawns were fed daily with a commercial shrimp diet (40% crude protein, 7% lipid, and 12% moisture; Nutripec Camaronina, Purina, Mexico). The daily feed ratio was determined based on 10% of wet weight and adjusted after each measurement (De los Santos-Romero et al., 2017). Survival was registered daily. The trial lasted 60 days. At days 0, 20, 40 and 60 all prawns were individually weighed ([+ or -]0.001 g, Sartorius AY303 Milligram Scale) and total length was measured by linear distance from the tip of the rostrum to the tip of the telson ([+ or -]0.01 mm, Truper Stainless Steel Vernier).
Average values of each experimental tank were used to determine the following parameters: average individual weight (AIW; g), average individual weight gain (AIWG; g), average individual daily growth rate (AIDGR; g [d.sup.-1]), biomass weight per area unit ([W.sub.t]; g [m.sup.-2]), biomass weight gain per area unit (BWG; g [m.sup.-2]), specific growth rate (SGR % [d.sup.-1]), food conversion ratio (FCR) and survival rate (SR, %) as stated previously (Garcia-Trejo et al., 2016; Pena-Herrejon et al., 2016; De los Santos-Romero et al., 2017).
The prawn performance parameters and water conditions were analyzed with one-way ANOVA to determine significant differences between treatments. Normality tests were performed (Kolmogorov-Smirnov test, [alpha] = 0.05). When differences were found, a test of the least significant differences (LSD, [alpha] = 0.05) was performed. All statistical analyses were performed with 95% reliability using Statgraphics routine Centurion XVI v16.1.11 software.
The water conditions (temperature, dissolved oxygen, pH, N[H.sub.4.sup.+], N[O.sub.2.sup.-] and N[O.sub.3.sup.-]) during the experimental period were not significantly different between treatments or tanks (P > 0.05), as expected since the tanks were connected to the same recirculating aquaculture system. The average values of all tanks are shown in Table 1. The minimum temperature was 26.2[degrees]C and the maximum 30.4[degrees]C.
Growth performance of M. tenellum is presented in Table 2. Initial AIW, initial length, final density, final length, final AIW, AIWG, SGR, and FCR showed no significant differences between treatments (P > 0.05). On day 20, individuals density had a significant difference (P < 0.05) between T1 and T3, without difference with T2, but on day 40 (T1, 7.77 [+ or -] 0.96 ind [m.sup.-2]; T2, 9.44 [+ or -] 0.96 ind [m.sup.-2]; T3, 10 [+ or -] 1.66 ind [m.sup.-2]) and day 60 (T1, 7.77 [+ or -] 0.96 ind [m.sup.-2]; T2, 8.88 [+ or -] 1.92 ind [m.sup.-2]; T3, 8.88 [+ or -] 0.96 ind [m.sup.-2]); there was no significant difference between densities (P > 0.05) (Fig. 1).
Final [W.sub.t], BWG; and SR data showed significant differences (P < 0.05) among densities. The SR decreased with density, obtaining a significant difference between T1 (77.77 [+ or -] 9.62%) and T3 (44.44 [+ or -] 4.81%), (T2 59.25 [+ or -] 12.83%) had no significant difference with the other densities.
[W.sub.t] had no significant differences on day 20 (T1 24.58 [+ or -] 1.32 g [m.sup.-2]; T2 28.78 [+ or -] 6.04 g [m.sup.-2]; T3 32.1 [+ or -] 4.7 g [m.sup.-2]). On day 40, T1 (26.78 [+ or -] 1.98 g [m.sup.-2]) and T3 (36.30 [+ or -] 3.23 g [m.sup.-2]) were significantly different among them, without a significant difference with T2 (31.37 [+ or -] 3.04 g [m.sup.-2]) (Fig. 2). On day 60 the significant difference was between T1 (37.84 [+ or -] 4.57 g [m.sup.-2]) and T2 (46.77 [+ or -] 4.79 g [m.sup.-2]), without a significant difference with T3 (45.39 [+ or -] 2.69 g [m.sup.-2]) (Fig. 3). The density-[W.sub.t] relationship produced a quadratic equation of the form (Fig. 3):
[W.sub.t] = -0.206([density.sup.2]) + 6.936(density) - 10.93 (1)
Equation (1) indicates that 16.83 ind [m.sup.-2] produces the maximum biomass at 60 days.
The maximum BWG of 20.75 [+ or -] 4.72 g [m.sup.-2] was obtained at T2 without a significant difference with T1 (20.70 [+ or -] 4.75 g [m.sup.-2]) and T3 (11.31 [+ or -] 3.65 g [m.sup.-2]), but there was a significant difference between T1 and T3 (P < 0.05).
Water temperature, dissolved oxygen, and N[H.sub.4.sup.+] were adequate for growing freshwater prawns (New et al., 2010; Ponce-Palafox et al., 2013); pH 9.36 [+ or -] 0.23 was above the maximum recommended value of 8.5 for M. tenellum (Ponce-Palafox et al., 2002). Therefore, pH could have influenced the prawn performance in this experiment. It has been reported that low and high pH negatively affects growth and survival in M. rosenbergii (Cheng et al., 2003; Kawamura et al., 2015). A high pH (8.81-9.88), as observed in this study, suppress the prawn's immune system (Cheng & Chen, 2000; Cheng et al., 2003). As a low concentration of N[H.sub.4] was maintained throughout the experimental period, it is considered that the pH effect was not critical (Cheng et al., 2003), since growth performance was similar to what was observed in other studies with M. tenellum (Vega-Villasante et al., 2011).
Densities differences have a tendency to decrease with time, obtaining no significant differences among treatments at the end of experimental time (Fig. 1), this trend is observed in previous stocking densities studies with M. tenellum in cage-pond systems (Lopez-Uriostegui et al., 2014) and with M. rosenbergii (Cuvin-Aralar et al, 2007; Sandifer & Smith, 2009). The SR exhibit an inverse relationship with density, as observed in other studies (Cuvin-Aralar et al., 2007; Yamasaki-Granados et al., 2013; Ponce-Palafox et al., 2014). The obtained SR for M. tenellum (T1, 77.77 [+ or -] 9.62%; T2, 59.25 [+ or -] 12.83%; T3, 44.44 [+ or -] 4.81%) are similar to the previously observed values for the same densities in cage pond systems (65.5 [+ or -] 0.9%; 55.5 [+ or -] 0.3%; 47.5 [+ or -] 0.6%) (Lopez-Uriostegui et al., 2014). Also, previous studies indicate that a survival higher than 50% is acceptable (New et al., 2010), what allows us to assume that this recirculating aquaculture system provides adequate conditions for the survival of M. tenellum.
Final AIW showed no difference between densities inside the current experimental recirculating aquaculture system in contradistinction to previous reports in pond systems, where a significant difference was observed between densities and their final AIW (Lopez-Uriostegui et al., 2014). Though in previous reports in M. rosenbergii there was no AIW difference between the higher (40 ind [m.sup.-2]) and lower (20 ind [m.sup.-2]) density, and also there was no difference between the higher and middle (30 ind [m.sup.-2]) density, close to what was observed here (Banu et al., 2016). The obtained final AIW in this experiment was lower than the previously observed values for M. tenellum at 60 days, which were of about 10 g (Vega-Villasante et al., 2011; Ponce-Palafox et al., 2013; Lopez-Uriostegui et al., 2014). The obtained AIW could have been influenced by the high flow rate of the system (a full water replacement in 25 minutes), since, as previously reported in M. rosenbergii, a high water replacement rate can diminish the beneficial effect of increasing the surface area (D'Abramo et al., 2000). More studies would be needed to determine if there is an effect on the growth rate of M. tenellum or not. Despite the lower final AIW, the AIDGR (T1, 0.054 [+ or -] 0.021; T2, 0.061 [+ or -] 0.018; T3, 0.057 [+ or -] 0.009) was inside the range of previous reports for M. tenellum, 0.007-0.135 g for 60 culture days (Vega-Villasante et al., 2011; De los Santos-Romero et al., 2017), thus, it would be necessary to conduct a study with a longer experimental time to clarity if the recirculating aquaculture system could obtain final AIW similar to traditional systems.
The observed final [W.sub.t] had no significant difference between T1 and T3, suggesting that the use of a high stocking density of prawns is not justified. T2 final [W.sub.t] showed a significant difference in comparison to T1 (Fig. 3). Since T2 presented a better [W.sub.t] than T1, it can be deduced that T2 was the density with the best production for the culture of M. tenellum in this experimental RAS. Data that does not correspond with what was observed in previous studies, were the highest densities reported the best [W.sub.t] for M. tenellum, M. americanum and M. rosenbergii (Garcia-Guerrero & Apun-Molina, 2008; Lopez-Uriostegui et al., 2014; Banu et al., 2016), possibly due to the difference in experimental times. The maximum estimated [W.sub.t] from equation (1) was obtained from estimated stocking density of 17 prawns [m.sup.-2] (Fig. 3), a value below what was reported in pond systems (24 ind [m.sup.-3]) (Lopez-Uriostegui et al., 2014). BWG at 60 days decreased with the increment of stocking density, due to the mortality of prawns which reduced the number of organisms in the higher initial stocking densities. This result does not correspond to what was observed previously in M. tenellum, where the higher densities increased their BWG (Lopez-Uriostegui et al., 2014), but in M. rosenbergii, it was reported that the net gain in biomass has a negative relation to stocking density (Paul et al., 2016), as seen in this study. SGR was inside the reported values for M. tenellum of about 1.3-1.5 (Ponce-Palafox et al., 2013; Lopez-Uriostegui et al., 2014) similar to what was observed in other species such as M. acanthurus 1.1-1.4, M. amazonicum 0.65-0.90 and M. rosenbergii 0.99-1.24 (Marques et al., 2012; Banu et al., 2016; Hernandez-Abad et al., 2018), suggesting that the organisms could reach the commercial weight with a longer culture time. The FCR previously reported for M. tenellum was of about 1.5-1.9 obtaining the commercial size (25 g) (Garcia-Ulloa et al., 2008; Ponce-Palafox et al., 2013; Lopez-Uriostegui et al., 2014), a lower FCR than the 4.335 [+ or -] 0.90 obtained in this study. This high FCR could be because the commercial weight was not allowed to be reached. But, also it need to take into account that the RAS did not allow the natural productivity of microalgae and associated detritus, unlike pond systems where microalgae and bacteria proliferation is allowed, condition that has been reported to impact on the growth of shrimp (Otoshi et al., 2003; Wasielesky et al., 2006). More tests are required to determine the exact reason for the high FCR; thus, further studies should focus on the effects of the recirculating aquaculture system in the complete culture time required to obtain the commercial weight.
Farming of M. tenellum inside a recirculating aquaculture system is feasible; the survival rates are adequate, with similar results to the traditional pond system and the cage-pond system (Ponce-Palafox et al., 2013; Lopez-Uriostegui et al., 2014). The results suggest that the use of a stocking density close to T2 could be adequate for this recirculating aquaculture system due to the higher [W.sub.t] and BWG; the traditional culture systems obtain greater productivity but, as stated in studies with shrimp, the RAS can have an effect on growth, through the lack of natural production (Otoshi et al., 2003; Wasielesky et al., 2006). Further researches should evaluate the correct feeding rate, considering whether the increased flow caused by the recirculating aquaculture system affects the food intake of M. tenellum. Future tests should be performed with longer experimental times to allow the organisms to reach the commercial sizes and observe the full effect of the culture conditions.
We want to thank all the participants of this study, especially to the members of the Bioengineering laboratories at Campus Amazcala and Campus Conca of the Universidad Autonoma de Queretaro. CONACYT partially financed this work for awarding the scholarship 401305 for Ph.D. studies.
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Guillermo Abraham Pena-Herrejon (1), Julieta Sanchez-Velazquez (1), Juan Fernando Garcia-Trejo (2) Genaro Martin Soto-Zarazua (3) & Enrique Rico-Garcia (4)
(1) Division de Estudios de Posgrado, Facultad de Ingenieria, Universidad Autonoma de Queretaro Queretaro, Mexico
(2) Cuerpo Academico Bioingenieria, Facultad de Ingenieria, Universidad Autonoma de Queretaro Queretaro, Mexico
(3) Cuerpo Academico Sistemas Embebidos y Aplicaciones, Facultad de Ingenieria Universidad Autonoma de Queretaro, Queretaro, Mexico
(4) Cuerpo Academico Ingenieria de Biosistemas, Facultad de Ingenieria Universidad Autonoma de Queretaro, Queretaro, Mexico
Corresponding author: Juan Fernando Garcia-Trejo (email@example.com)
Corresponding editor: Fernando Vega-Villasante
Received: 29 May 2018; Accepted: 29 August 2018
Table 1. Average water parameters of the Macrobrachium tenellum recirculating aquaculture system during the experimental time. Values are the mean [+ or -] standard deviation. Parameter Mean [+ or -] SD Water temperature ([degrees]C) 27.9 [+ or -] 1.1 Dissolved oxygen (mg [L.sup.-1]) 6.64 [+ or -] 0.67 pH 9.36 [+ or -] 0.23 N[H.sub.4.sup.+] (mg [L.sup.-1]) 0.04 [+ or -] 0.05 N[O.sub.2.sup.-] (mg [L.sup.-1]) 0.05 [+ or -] 0.01 N[O.sub.3.sup.-] (mg [L.sup.-1]) 1.24 [+ or -] 0.69 Table 2. Growth performance of Macrobrachium tenellum cultured at different stocking densities in a recirculating aquaculture system. Within a row, means accompanied by different lowercase letters are significantly different (P < 0.05). Values are the mean [+ or -] standard deviation. T1: 10 ind [m.sup.-2], T2: 15 ind [m.sup.-2], and T3: 20 ind [m.sup.-2]. AIW: average individual weight, AIWG: average individual weight gain, AIDGR: average individual daily growth rate, Wt: biomass weight per area unit, BWG: biomass weight gain per area unit, SGR: specific growth rate, FCR: food conversion ratio, and SR: survival rate. Experimental tank T1 T2 Initial density (ind [m.sup.-2]) 10.00 [+ or -] 0.00 15.00 [+ or -] 0.00 Final density (ind [m.sup.-2]) 7.77 [+ or -] 0.96 8.88 [+ or -] 1.92 Initial AIW (g) 1.71 [+ or -] 0.14 1.73 [+ or -] 0.10 Final AIW (g) 4.97 [+ or -] 1.28 5.41 [+ or -] 1.13 Initial length (mm) 43.98 [+ or -] 2.30 45.50 [+ or -] 1.06 Final length (mm) 74.95 [+ or -] 7.77 79.27 [+ or -] 10.22 AIWG (g) 3.25 [+ or -] 1.30 3.67 [+ or -] 1.10 AIDGR (g [day.sup.-1]) 0.054 [+ or -] 0.021 0.061 [+ or -] 0.018 Initial [W.sub.t] (g [m.sup.-2]) 17.13 [+ or -] 0.28 z 26.01 [+ or -] 0.47 y Final [W.sub.t] (g [m.sup.-2]) 37.83 [+ or -] 4.57 z 46.76 [+ or -] 4.70 y BWG (g [m.sup.-2]) 20.70 [+ or -] 4.75 z 20.75 [+ or -] 4.72 zy SGR (% [d.sup.-1]) 1.74 [+ or -] 0.42 1.87 [+ or -] 0.31 FCR 5.26 [+ or -] 1.81 4.33 [+ or -] 0.90 SR (%) 77.77 [+ or -] 9.62 z 59.25 [+ or -] 12.83 zy Experimental tank T3 Initial density (ind [m.sup.-2]) 20.00 [+ or -] 0.00 Final density (ind [m.sup.-2]) 8.88 [+ or -] 0.96 Initial AIW (g) 1.70 [+ or -] 0.11 Final AIW (g) 5.14 [+ or -] 0.55 Initial length (mm) 42.92 [+ or -] 1.83 Final length (mm) 78.71 [+ or -] 1.54 AIWG (g) 3.43 [+ or -] 0.56 AIDGR (g [day.sup.-1]) 0.057 [+ or -] 0.009 Initial [W.sub.t] (g [m.sup.-2]) 34.07 [+ or -] 0.97 x Final [W.sub.t] (g [m.sup.-2]) 45.39 [+ or -] 2.69 zy BWG (g [m.sup.-2]) 11.31 [+ or -] 3.65 y SGR (% [d.sup.-1]) 1.83 [+ or -] 0.19 FCR 4.71 [+ or -] 0.50 SR (%) 44.44 [+ or -] 4.81 y
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|Title Annotation:||Short Communication|
|Author:||Pena-Herrejon, Guillermo Abraham; Sanchez-Velazquez, Julieta; Garcia-Trejo, Juan Fernando; Soto-Zara|
|Publication:||Latin American Journal of Aquatic Research|
|Date:||May 1, 2019|
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