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

Factors Affecting Italian Ryegrass (\u3cem\u3eLolium multiflorum\u3c/em\u3e L.) Seed Distribution

Italian ryegrass (Lolium multiflorum L.) can be a productive and high-quality cool-season forage in the Southern Great Plains of the U.S.A, if it is managed to produce sufficient seed for effective reestablishment without compromising forage yield. Before the re-seeding dynamics of Italian ryegrass can be modeled an understanding of seed production, seed-shed, and seed dispersal is necessary. Here two factors affecting Italian ryegrass seed dispersal and distribution are examined – wind and cultivation practice (mowing and raking)

The Effect of Harvest Management on Forage Production and Self-Reseeding Potential of Italian Ryegrass (Lolium Multiflorum L.)

Italian ryegrass (Lolium multiflorum L.) (IRG) can be managed to produce a seed output sufficient for effective re-establishment, without compromising forage yield, it may provide an alternative to perennial cool-season grasses in the Southern Great Plains of the U.S.A. The reduction in cost of replanting and avoidance of cultivation offered by a self-seeding crop may be particularly useful in low-input production systems. We examined the effect of dates of initial harvest in spring and of partial harvests on forage yield, seed output and re-establishment of Italian ryegrass

Overseeding Unimproved Warm-Season Pasture with Cool- and Warm-Season Legumes to Enhance Forage Productivity

Overseeding forage legumes into existing warm-season pasture may help to reduce cool-season forage deficit on small and resource-limited small farms in the southern Great Plains of the United States. Unimproved warm-season grass pastures were overseeded with Korean lespedeza (Lespedeza stipulacea Maxim) were not overseeded with summer legume. These same plots were subsequently overseeded with hairy vetch (Vicia villosa Roth), crownvetch (Coronilla varia L.), black medic (Medicago lupulina L.) or ladino white clover (Trifolium repens L.) or, not overseeded with cool-season legume. Including lespedeza in a forage mixture increased total forage yield by an average of 15%, or 1700 kg ha-1 over 4 years. Overseeding with cool-season legumes provided a net benefit in total annual forage yield of 0.75 kg for each 1.0 kg of legume produced. Yield increases resulting from overseeding with hairy vetch or black medic were largely limited to the harvest season following sowing, while overseeded crownvetch or white clover provided limited short- to medium-term yield benefit. Improvement of low-productivity pasture resulting from legume introduction is likely to be slow and will require sustained management input to ensure the presence of a productive legume plant stand

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