Performance of a Temperate-Zone Channel Catfish Biofloc Technology Production System During Winter

Channel catfish (Ictalurus punctatus) have been grown successfully in an outdoor biofloc technology production system. Outdoor biofloc production systems in the tropic sare operated year-round, whereas the channel catfish studies were conducted only during the growing season and biofloc production tanks were harvested and idled for the winter. If an outdoor biofloc production system is to be adopted by farmers at temperate latitudes, then data gaps related to system and fish performance over the winter must be addressed. The present study was conducted to address these data gaps for channel catfish culture. Waters from a recently completed biofloc production experiment that contained low (153.3 mg/L) and high (790.0 mg/L) total suspended solids were retained for this study. Three 15.7-m3 tanks per water type each were stocked (8kg/m3) with market-size channel catfish from that same study for a 152-day study from November to April. Mean chlorophyll a concentrations were similar in both treatments during the first 55 days, after which treatments diverged and chlorophyll a concentration increased linearly (P\u3c0.001, R2=0.721) to a mean final concentration of 2251.7 mg/m3 in the low solids treatment. Ammonia from ammonium chloride spikes (1.25–1.5mg TAN) added on three occasions during the experiment was biotransformed completely, putatively by algal uptake and nitrification. Ammonia biotransformation rate was linearly related to mean water temperature in the high solids (P\u3c0.001, R2=0.920) and low solids (P=0.002, R2=0.761) treatments. Catfish survival through the winter was high (99.75%) in biofloc tanks and did not differ significantly between treatments. Net fish yield did not differ significantly between treatments. However, net fish yields were 1–4% less than initial fish biomasses. Water in the biofloc production tanks appeared to retain through the winter the ability to biotransform ammonia regardless of whether phytoplankton or suspended solids predominate and despite sustained input of ammonia-nitrogen. Having an active biofloc in the spring obviates the start-up time required to establish a new, fully functional biofloc and the associated TAN and nitrite spikes

Performance of a Temperate-Zone Channel Catfish Biofloc Technology Production System During Winter

Channel catfish (Ictalurus punctatus) have been grown successfully in an outdoor biofloc technology production system. Outdoor biofloc production systems in the tropic sare operated year-round, whereas the channel catfish studies were conducted only during the growing season and biofloc production tanks were harvested and idled for the winter. If an outdoor biofloc production system is to be adopted by farmers at temperate latitudes, then data gaps related to system and fish performance over the winter must be addressed. The present study was conducted to address these data gaps for channel catfish culture. Waters from a recently completed biofloc production experiment that contained low (153.3 mg/L) and high (790.0 mg/L) total suspended solids were retained for this study. Three 15.7-m3 tanks per water type each were stocked (8kg/m3) with market-size channel catfish from that same study for a 152-day study from November to April. Mean chlorophyll a concentrations were similar in both treatments during the first 55 days, after which treatments diverged and chlorophyll a concentration increased linearly (P\u3c0.001, R2=0.721) to a mean final concentration of 2251.7 mg/m3 in the low solids treatment. Ammonia from ammonium chloride spikes (1.25–1.5mg TAN) added on three occasions during the experiment was biotransformed completely, putatively by algal uptake and nitrification. Ammonia biotransformation rate was linearly related to mean water temperature in the high solids (P\u3c0.001, R2=0.920) and low solids (P=0.002, R2=0.761) treatments. Catfish survival through the winter was high (99.75%) in biofloc tanks and did not differ significantly between treatments. Net fish yield did not differ significantly between treatments. However, net fish yields were 1–4% less than initial fish biomasses. Water in the biofloc production tanks appeared to retain through the winter the ability to biotransform ammonia regardless of whether phytoplankton or suspended solids predominate and despite sustained input of ammonia-nitrogen. Having an active biofloc in the spring obviates the start-up time required to establish a new, fully functional biofloc and the associated TAN and nitrite spikes

Comparative water quality and channel catfish production in earthen ponds and a biofloc technology production system

This 210-day study compared variation in water quality and fish growth for channel catfish (Ictalurus punctatus; 47 g/fish) stocked in earthen ponds (1.5 fish/m2, 14,820/ha) and in a biofloc technology (BFT) production system with high-density polyethylene-lined rectangular tanks (12.6 fish/m2, 126,000/ha). Feed input and culture environment affected water-quality dynamics. In ponds, phytoplankton uptake predominated and little nitrification occurred, whereas in the BFT system phytoplankton uptake and nitrification maintained low ammonia-nitrogen concentrations. Size classes of fish were skewed toward the larger market sizes in ponds and toward smaller market sizes in the BFT system. Mean final fish weight was 630 g/fish in ponds and 542 g/fish in the BFT system. Despite these differences, fish yield was higher in the BFT system (7.7 kg/m3 v. 1.5 kg/m3) because of the greater initial stocking rate

Growth of Stocker Channel Catfish to Large Market Size in Single-Batch Culture

Catfish farmers increasingly are producing fish larger than the traditional size of 0.45-0.57 kg/fish in order to meet processing plant requirements for larger fish. Production of larger channel catfish (Ictalurus punctatus) in multiple-batch culture has been investigated in a few studies, but the impact of understocked fingerlings on growth of carry-over fish is unknown. The present study was conducted to quantify growth, feed conversion ratio, net daily yield, and net and total yield of stocker channel catfish grown in single-batch, one-season culture to mean individual weights of 0.60, 0.72, 0.91, or 1.17 kg/fish. Channel catfish (mean weight = 0.26 kg/fish) were stocked into 12 0.1-ha ponds at 11,115 fish/ha. Fish were fed a 32% crude protein floating extruded feed once daily to apparent satiation. When the average weight of the fish population reached the target weight, three randomly selected ponds were harvested. Fish growth was linear in all treatments. Growth rates were similar for fish grown to 0.60, 0.72, and 0.91 kg/fish, and significantly lower (P \u3c 0.05) than for fish grown to 1.17 kg. Variation in individual fish weight increased linearly with increased duration of culture period. Feed conversion ratio averaged 1.9 and did not differ significantly among treatments. The percentage of the fish population at harvest that fell within the 0.57 to 2.04 kg-size range preferred by processing plants increased from 56.6 to 98.5% as the mean weight at harvest increased from 0.60 to 1.17 kg/fish

Ultimate Biochemical Oxygen Demand in Semi-Intensively Managed Shrimp Pond Waters

Three independent studies were conducted to quantify ultimate biochemical oxygen demand (UBOD) and the corresponding decomposition rate constant for production pond (average 21.5 ha each) waters and effluents on six semi-intensively managed marine shrimp (Litopenaeus vannamei) farms in Honduras. Samples were collected during the rainy season in studies 1-3 and during the dry season only in study 1. Pond water samples were collected during the culture period and/or at harvest. The dry season 30-d biochemical oxygen demand (BOD30) of pond waters across all farms was 26% lower and UBOD was 54% lower, but the decomposition rate constant was more than twice as great as during the rainy season. During the dry season, biochemical oxygen demand was nearly completely expressed after 30 d of incubation whereas during the rainy season BOD was about 65% expressed after 31 d of incubation and the correlation between BOD31 and UBOD was less strong compared to the dry season. Water quality variables were correlated with measures of BOD during rainy and dry seasons, but only the correlation between chlorophyll a and BOD measures was predictive. In studies 2 and 3, BOD after 88-94 d of incubation was expressed almost completely and corresponded closely with computed UBOD. No significant differences in UBOD were detected in pond samples taken after 30, 61, or 71 (harvest) d of grow out in study 3. Mean decomposition rate constant ranged from 0.054-0.071 d-1 in studies 1-3 (rainy season), compared to 0.123 d-1 in study 1 (dry season)

Effect of Stocking Biomass on Solids, Phytoplankton Communities, Common Off-Flavors, and Production Parameters in a Channel Catfish Biofloc Technology Production System

The effect of initial channel catfish (Ictalurus punctatus, Rafinesque, 1818) fingerling biomass (1.4, 1.8, or 2.3 kg m-3) on phytoplankton communities, common off-flavours and stocker catfish production parameters was evaluated in biofloc technology production tanks. Stocker catfish size (145.5–172.6 g fish-1) at harvest did not differ among treatments, but net yield increased linearly as initial biomass increased (R2 = 0.633). Mean total feed consumption increased linearly with initial catfish biomass (R2 = 0.656) and ranged from 10.7 to 15.8 kg m -3. Total suspended solids (TSS) in all treatments increased linearly with total feed addition, and high TSS appeared to impact negatively daily feed consumption. Initial phytoplankton populations were dominated by small colonial green algae and diatoms, and later transitioned to populations dominated by a small, filamentous cyanobacteria and diatoms. Low, variable concentrations of 2-methylisoborneol and geosmin were present in biofloc tank water during most of the study and two tanks yielded catfish with 2-methylisoborneol or geosmin concentrations that might be classified as off-flavour. One isolate of actinomycete was isolated sporadically from some biofloc tanks, but its abundance was not correlated with 2-methylisoborneol concentration in tank waters. The microbial sources of 2-methylisoborneol and geosmin in biofloc tanks remain unidentified

Effects of Solids Removal on Water Quality and Channel Catfish Production in a Biofloc Technology Production System

Total suspended solids control was evaluated in a channel catfish (Ictalurus punctatus) biofloc technology production system. Settling chamber flow rates were 0.9 (LO) or 2.9 (HI) L/min to reduce total suspended solids to 300 mg/L; solids were not removed from control tanks. Channel catfish yields (7.6–8.7 kg/m3) were not affected significantly, but control fish were skewed toward smaller size classes. Control treatment channel catfish tolerated 1,410 mg/L total suspended solids without adverse effects. LO- and HI-treatment fillet geosmin concentrations were high enough to be designated as off-flavor. Water quality results suggested that nitrification was affected by solids removal

Factibilidad de la producción masiva de alevines machos de Tilapia nilotica a través de la inversión hormonal del sexo en Honduras

La demanda de alevine machos de tilapia para sembrar en estanques de engorde ha aumentado significativamente en los últimos cinco años. Nuevas tecnologías de producción son necesarias para poder abastecer la demanda existente y futura de alevines. Una de ellas es la Inversión hormonal de sexo en pescaditos de tilapia que consiste en la administración por vía oral de una hormona masculina sintética (17 a-metilo-testosterona) durante un período de 28 días comenzando poco después de haber eclosionado y antes de haberse diferenciado el tejido gonadal. El objetivo de este trabajo, que se desarroll ó durante el período enero a noviembre de 1988, fue determinar la factibilidad de implementar en la Estación Experimental Acuícola El Carao, Comayagua, Honduras, la producción masiva de alevines machos de tilapia utilizando la Inversión hormonal de sexo. El proceso requiere pescaditos menores de 13 mm de largo que se obtienen de estanques de reproducción (0.05 - 0.1 ha) que han sido sembrados con reproductores de Tilapia nilotica (2 hembras: 1 macho). Los estanques son drenados en promedio de 18 a 20 días después de sembrados,  los reproductores transferidos a piletas de concreto Y las larvas cosechadas usando una red de mano con malla de 1.6 mm. El ciclo completo (siembra a siembra) de producción de larvas dura un promedio de 23 d. El número promedio de larvas cosechadas variaba entre 66,500 a 99500. Los pescaditos son sembrados (4,400/m2) en japas (encierro de malla de 1.6 mm; dimensiones 2 m x 2.1 m x 1m o 1 m x 2 m x 1 m, profundidad promedia de agua = 60 cm) después de haber sido pasados por un excluidor con malla de 3.2 mm. La hormona es Incorporada en alimento molido (23% proteína) a razón de 60 mg/kg alimento. Alimento es ofrecido cuatro veces al día, siete días por semana. La duración de] tratamiento es de 28 d. El promedio de sobrevivencia de la etapa de tratamiento hormonal fue 87.6%. Larvas tratadas son sembradas en estanques de pre-engorde (0.2 ha) para crecimiento adicional a razón de 102,500/ha. Un total de 1.935,000 pescaditos fueron cosechados de los estanques de reproducción, de los cuales se descartaron 350,000 por ser grandes para tratarse. De las 1,585,000 de pescaditos restantes 1.313,500 fueron sometidas a tratamiento hormonal; 272,000 fueron descartadas por falta de espacio en japas. Un total de 1.189,600 pescaditos completaron o se encontraron en la etapa de tratamiento. Estanques de pre-engorde han sido sembrados con un total de 661,700 alevines; el promedio de sobrevivencia de esta etapa fue 81.6%. Hasta noviembre, 1988, se produjeron 399,000 alevines de 18 g cada uno y de los cuales más del 97% fueron machos. El costo de producción de alevines tratados (0.15 g cada uno) fue L. 9.124,000 alevines. La tecnología ha resultado ser factible no sólo para la Estación Experimental Acuí- cola El Carao, sino también para piscicultores calificados

Effect of Stocking Rate on Growing Juvenile Sunshine Bass, Morone chrysops × M. saxatilis, in an Outdoor Biofloc Production System

The biofloc technology production system is a production intensifying management strategy used primarily for culturing tilapia and penaeid shrimp, both of which can consume the biofloc. Other fish can be grown in biofloc systems because the biofloc serves to maintain water quality, metabolizing the ammonia excreted by intensively fed fish. A dose-response study was conducted in an outdoor biofloc system to begin quantifying the stocking rate-production function for sunshine bass, Morone chrysops x M. saxatilis, advanced fingerlings. Sunshine bass (2.9 ± 0.2 g/fish) were stocked into tanks at 50 to 250 fish/m2 in 50 fish/m2 increments. After 94 days, gross yields ranged from 1.4 to 3.1 kg/m3 and were independent of stocking rate. Harvested fish were separated into two size groups: smaller than 115 mm total length (target fish) and larger than 115 mm TL (jumper fish). Target fish increased linearly from 62% to 93% and jumpers decreased linearly from 38% to 7% of the population, respectively, as stocking rate increased. The outdoor biofloc system offers potential for intensifying the production of advanced sunshine bass fingerlings, but feed consumption appeared to be impeded by high total suspended solids concentrations. Further research is needed to optimize stocking rates and solids management

Hypoxia affects performance traits and body composition of juvenile hybrid striped bass (Morone chrysops x M. saxatilis)

Performance traits and body composition of juvenile hybrid striped bass (Morone chrysops x M. saxatilis) in response to hypoxia were evaluated in replicate tanks maintained at constant dissolved oxygen concentrations that averaged 23.0 ± 2.3%, 39.7 ± 3.0%, and 105.5 ± 9.5% dissolved oxygen saturation. Fish were fed a commercially formulated feed daily to apparent satiation. Total feed intake and fish growth and yield increased linearly in response to increased dissolved oxygen concentration. Nutrient utilization was reduced significantly only at the greatest level of hypoxia. With the exception of whole-body protein content, whole body compositional indices and nutrient retention efficiencies were linearly related to dissolved oxygen concentration. Results demonstrate that as hypoxia becomes more severe, juvenile hybrid striped bass feed intake is reduced, which affects growth and nutrient retention