Hybrid catfish (♀ Channel Catfish Ictalurus punctatus × ♂ Blue Catfish I. furcatus) were reared as single‐batch crops during the growing season (June–September) of two years under two different dissolved oxygen (DO) regimes each year: (1) a high‐DO (control) treatment with minimum daily DO maintained above 3.8 ppm in both years and (2) a low‐DO (test) treatment with minimum DO maintained at 1.6 ppm in the first year and 1.3 ppm in the second year. Fish were fed daily to apparent satiation with a 32% protein commercial feed and harvested each year. In both years, dissolved oxygen concentration significantly impacted gross and net production, final fish weight, and mean fish weight gain due to reduced feed intake. Feed intake was reduced in the low‐DO treatment by 26.6% in year 1 and 29.2% in year 2. Food conversion ratios averaged 1.83 overall and were not affected by minimum DO. Fish in high‐DO treatments gained an average of 44% more weight (1.50 lb/fish) than fish in low‐DO treatments (1.04 lb/fish). Initial weight at stocking also had a significant impact on weight gain: fish stocked at a 0.16‐lb average weight (year 2) gained 37% more weight than fish stocked at a 0.11‐lb average weight (year 1), even though the stocking rate of the larger fish was 50% higher. Hybrid catfish had less reduction in feed intake at reduced DO compared with reported values for Channel Catfish and Blue Catfish.
Hybrid catfish (♀ Channel Catfish Ictalurus punctatus × ♂ Blue Catfish I. furcatus) production ponds often produce a wide size range of fish, and payments to farmers may be reduced due to discounts for larger fish. In general, fish under 1 lb or over 4 lb may decrease the price paid to farmers, but this is highly dependent on individual processors. The present study was conducted to determine the effect of grading hybrid catfish fingerlings on the size distribution of harvested food fish. Three 0.25-acre ponds were stocked with ungraded fingerlings (average weight = 0.05 lb; coefficient of variation [CV] = 78.0%) at 8,000 fish/acre. An additional three 0.25-acre ponds were stocked with double-graded fingerlings of the same average weight (0.05 lb) as the ungraded fingerlings but with a significantly reduced size variation (CV = 26.9%). Grading of the fingerlings had no significant effect on any production variable other than final size variation (ungraded fingerlings: CV = 48.2%; graded fingerlings: CV = 26.1%). Final mean weights were identical (1.1 lb) and feed conversion ratios were nearly identical (1.58 and 1.57) between the treatments. Survival and net production were similar between treatments. Overall, 13.5% of ungraded fish and 1.2% of graded fish were less than 0.5 lb at harvest; 5.6% of the ungraded fish and 0.1% of the graded fish were larger than 2.0 lb. Grading of hybrid catfish fingerlings is an effective means of decreasing food fish size variability without impacting production efficiency.
Feed intake, the feed conversion ratio (FCR), and the production of blue catfish Ictalurus furcatus and channel catfish I. punctatus were examined in 1‐acre ponds maintained at either a high or low minimum dissolved oxygen (DO) concentration (mean values of 4.29 and 2.54 ppm [55% and 32% air saturation], respectively). Two additional studies were conducted examining only blue catfish in 0.25‐acre ponds maintained at either a high (mean values of 4.43 and 4.46 ppm [56% and 55% air saturation] in the two studies) or low (mean values of 1.41 and 1.64 ppm [18% and 20% air saturation]) minimum DO concentration. Blue and channel catfish exhibited similar feed intake (13,432 versus 13,063 lb/acre), growth (1.40 versus 1.49 lb/fish), gross production (6,662 versus 6,663 lb/acre), and net production (5,935 versus 5,813 lb/acre) in the high‐DO treatments in the 1‐acre ponds. Within the low‐DO treatment, feed intake was not significantly different (13,555 versus 12,398 lb/acre for blue and channel catfish, respectively), but both gross production (6,796 versus 5,810 lb/acre) and net production (6,069 versus 4,960 lb/acre) were significantly lower in the channel catfish ponds. The FCR was similar between species (2.25 versus 2.38) and was not affected by DO treatment. In the blue catfish studies in the 0.25‐acre ponds, ponds in the high‐DO treatments had significantly higher feed intake (+23.0% and +33.4% in 2006 and 2007, respectively) and net weight gain (+38.0% versus +42.3%) than those in the low‐DO treatments; both gross production (16,898 versus 12,963 lb/acre) and net production (14,768 versus 10,855 lb/acre) were significantly higher in the high‐DO treatment in 2006. Food conversion ratios averaged 1.86 in 2006 and 2007 and were similar in fish among DO treatments in both years. Data from these and other similar controlled studies indicate that most blue catfish production variables tend to be affected less by low DO concentrations than are channel catfish.
Eight channel catfish Ictalurus punctatus spawns were split into two similar portions and incubated under controlled conditions to determine the effect of dissolved oxygen (DO) concentration on the development and survival of eggs and fry. The DO concentration was 7.42 ± 0.03 mg/L (mean ± SD; 92.5% saturation) and 18.40 ± 0.28 mg/L (230% saturation) through hatching in the low‐ and high‐oxygen treatments, respectively. Eggs hatched 6 h earlier in the low‐oxygen treatment, but fry reached swim‐up stage 31 h later. Survival to the swim‐up stage in the low‐oxygen treatment was 16.4 percentage points lower than in the high‐oxygen treatment (72.5% versus 88.9%, respectively). The routine metabolic rate and limiting oxygen concentration were also determined for eggs, sac fry, and swim‐up fry. Oxygen consumption increased through swim‐up stage, as expected. However, the limiting oxygen concentration peaked during the last day of incubation at 88.1 ± 2.9% saturation and decreased to 40.1 ± 2.0% saturation upon hatching. Premature hatching observed in the low‐oxygen treatment was apparently initiated when the limiting oxygen concentration approached the ambient oxygen saturation on the last day of incubation. A survey of DO management in 26 commercial catfish hatcheries in the Mississippi Delta revealed that DO saturation in the hatching troughs ranged from 45.2% to 100.2%, with only nine hatcheries (35% of the hatcheries sampled) having a DO saturation greater than 95%. Seventeen hatcheries (65%) had a DO saturation less than that maintained in the low‐oxygen treatment in our hatching experiment and could experience greater mortality through swim‐up than we observed. We recommend that hatcheries initially run well water through a packed column and use blowers or liquid oxygen to maintain the DO concentration in hatching troughs at or above air saturation as eggs near the time of hatching.
The original description of Henneguya pellis, a myxozoan parasitizing blue catfish Ictalurus furcatus, is supplemented with new data on histopathology, spore morphology, and 18S small subunit (SSU) ribosomal DNA (rDNA) sequence. Plasmodia presented as both internal and external, raised, cyst-like lesions on the body wall of the peritoneal cavity and on the skin. The cysts contained numerous elongate, lanceolate myxospores, flattened parallel to the suture line. The spore body was 14.8 ± 1.1 µm (range 13.0-17.1) long and 4.8 ± 0.8 µm (range 4.0-7.4) wide in frontal view. The caudal appendages were 77.7 ± 8.8 (range 57.4-96.4) in length. There were 2 pyriform polar capsules, unequal in length, with the longer capsule measuring 7.2 ± 0.6 µm (range 6.2-8.4) in length and the shorter capsule measuring 6.5 ± 0.5 µm (range 5.5-8.0). The polar capsules were not significantly different in width, measuring 1.7 ± 0.2 µm (range 1.4-1.9). There were 8 turns in the polar filament coil. The total length of the spore was 92.5 ± 9.2 µm (range 73.3-113.5). Spore morphology and site of development are similar to that of Henneguya sutherlandi from channel catfish; however, 18S rDNA sequence data support previous findings that identify H. pellis and H. sutherlandi as 2 distinct species.
scite is a Brooklyn-based organization that helps researchers better discover and understand research articles through Smart Citations–citations that display the context of the citation and describe whether the article provides supporting or contrasting evidence. scite is used by students and researchers from around the world and is funded in part by the National Science Foundation and the National Institute on Drug Abuse of the National Institutes of Health.
hi@scite.ai
10624 S. Eastern Ave., Ste. A-614
Henderson, NV 89052, USA
Copyright © 2024 scite LLC. All rights reserved.
Made with 💙 for researchers
Part of the Research Solutions Family.