Pond-raised Catfish Research Articles

Using quantitative polymerase chain reaction (qPCR) and occupancy models to estimate atypical Aeromonas hydrophila (aAh) prevalence in catfish

A strain of atypical Aeromonas hydrophila (aAh) has caused issues within the channel catfish Ictalurus punctatus industry of the southeastern United States since 2009. These atypical pathotypes cause acute mortality events resulting in catastrophic losses, as opposed to more chronic mortality and lesions seen in typical infections of motile aeromonas septicemia (MAS). This study provides a basic framework for rapid field sampling negating the need for re-isolation or enrichment culture, thereby reducing the time between sampling and detection. Rapid and accurate quantitative PCR based methods for detection of aAh have been described and are important confirmative tools in research and diagnostic settings. These methods also have application in epidemiological surveys investigating the spread of disease and elucidating pathogen dynamics that may lead to outbreaks. To date, no field-based sampling technique for rapid aAh detection in resident pond populations has been explored. In this study, culture swabs taken from the gills and lower intestine of pond-raised catfish were assessed for their suitability as rapid field-based collection methods for downstream applications. Results showed the state of the pond has a significant effect on which swab location yields the highest proportion of PCR positive results. During an active outbreak, gill swabs identified more fish as aAh-positive; however, in apparently healthy populations, swabs taken from the lower intestine identified significantly more aAh-positive fish than gill swabs, despite no statistical difference in the concentration of aAh cell equivalents between swab sites. Naïve prevalence estimates from the two swab types were compared to estimates provided by a hierarchical occupancy model. Prevalence estimates from gill swabs was 0.95% while vent swabs showed a prevalence of 2.2%; however, estimates based on the occupancy model were 6.6% and 9.8%, respectively. This multi-fold increase in prevalence estimates highlights the importance of accounting for imperfect detection in epidemiological studies and in assessing potential outbreak risk. Furthermore, occupancy models based on these data indicate resident fish can be aAh-positive carriers with no gross signs of infection, providing evidence aAh can reside in catfish ponds in the absence of disease. The presence of a carrier state indicates the pathogen may pose minimal risk to the host is compromised or a mechanical portal of entry into the blood stream is available. This provides an important direction for future research in understanding the mechanisms of aAh outbreaks in catfish aquaculture ponds.

Microbiological Quality, Proximate Composition and Heavy Metal Contamination of Pond-raised Catfish (Clarias gariepinus)

Microbiological Quality, Proximate Composition and Heavy Metal Contamination of Pond-raised Catfish (Clarias gariepinus)

English

Proximate composition and shelf-life studies of wild and pond-raised catfish (Clarias gariepinus) were determined using chemical, microbiological and sensory analyses. Proximate composition of both wild and pond-raised catfish showed differences in the lipid and protein levels. The pond-raised fish had higher lipid (6.30%) and protein (20.00%) than the wild fish lipid (4.48%) and protein (18.05%). Whole ungutted wild and pond-raised catfish was in good and satisfactory conditions for 17 and 22 days, respectively when stored in ice immediately after harvesting. There was no significant difference (p > 0.05) in the storage life in ice of the wild and pond-raised catfish. The descriptive sensory evaluation showed that the fish underwent changes in eyes, gills, texture, odour and general appearance. The statistical analysis showed that the correlations between the cooked odour, texture and flavour of both samples were significant at p < 0.05. The wild and pond-raised catfish showed a decline in sensory parameters during storage in ice with concomitant increase in bacteria counts and total volatile bases (TVB). The microbial population was dominated by bacilli, the counts ranged from 11.5 × 102 cfu/g to 15.4 × 102 cfu/g for wild catfish and 9.7 × 102 cfu/g to 11.1 × 102 cfu/g for the pond-raised catfish. Rejection of the catfish after 22 days was based mainly on rancid, putrid, feacal, ammoniacal and sulphide odours. TVB ranged from 2.41 to 20.50 mg/100 g for wild catfish and 2.86 to 22.88 mg/100 g for pond-raised catfish.   Key words: Sensory changes, farmed Clarias, wild Clarias, shelf-life.

Molluscicidal and antifungal activity of Erigeron speciosus steam distillate.

The steam-distilled fraction of the aerial parts of Erigeron speciosus (Lindl) DC was tested for activity against strawberry plant pathogenic fungi Botrytis cinerea Pers ex Fr, Colletotrichum acutatum Simmonds, C fragariae Brooks, C gloeosporioides (Penz) Penz & Sacc, and the intermediate host snail Planobdella trivolvis that harbors the trematode, Bolbophorus confusus, that infests and causes severe infections in pond-raised catfish in the Mississippi Delta region of the USA. Bioautography on silica TLC plates demonstrated antifungal activity in the steam distillate. Preliminary bioassays of the steam distillate indicated the presence of phytochemicals toxic to P trivolvis. The bioactive compounds methyl 2Z, 8Z-deca-2,8-diene-4,6-diynoate and its 2E, 8E isomer were isolated by bioassay-guided fractionation and chromatographic techniques and identified by 1H NMR spectroscopy.

A River Full of Fish: Industrial Catfish Production and the Decline of Commercial Fishing on the Upper Mississippi River

This paper explores the decline of commercial fishing on the upper Mississippi River. For much of the 20th century fishing provided work for many in river communities and an important buffer against fluctuations in the regional economy. In the late 1960s the introduction of pond-raised catfish from newly created fish farms in the southern United States created a source of uniform, mild-flavored, and untainted fish that satisfied the preferences of both the food industry and consumers. Demand for river fish, in particular catfish, collapsed. Today fish are plentiful in the Mississippi but low prices offer little incentive to independent fishers. Some fish processors, faced with declining local demand, have stepped up sales of river fish to markets as far away as New York. Other processors have opted not to fight the fish-farming industry and now distribute pond-raised catfish. This paper explores the complex social and economic forces that have reshaped local economies and the ecology of the river itself.

Effects of Dietary Catfish Oil, Menhaden Oil, and Tallow on Production Characteristics of Pond-Raised Channel Catfish, Ictalurus punctatus

A study was conducted to evaluate three practical lipids -catfish oil, menhaden oil, and tallow -as energy supplements for channel catfish fed extruded diets during a two-year production trial. For 20 months, pond-raised catfish were fed a custom-manufactured diet containing 2% or 4% of each lipid source. Fish were sampled after eight months of treatment at approximately 0.5 kg body weight (year-1 fish) and again at termination of the experiment (20 months) at approximately 1 kg body weight (year-2 fish) to determine effects of lipid supplementation on weight gain, tissue total lipid content, and dressing percentage. Fish production among the six treatment groups also was compared. Survival, per-hectare yield, live weight at harvest, dressing percentage, and liver lipid content did not differ (P> 0.05) among year-1 fish or year-2 fish, regardless of dietary treatment. Similarly, muscle (fillet) lipid content of year-1 fish did not differ (P> 0.05) among treatments, nor did muscle lipid levels in year-2 fish, with one exception: year-2 fish fed 2% catfish oil had significantly higher muscle lipid levels than fish fed 4% catfish oil. The reason for this difference was not apparent. When data were pooled by year without regard to diet, year-2 fish had significantly lower hepatosomatic index and visceral fat content and significantly higher dressing percentage and muscle lipid content than year-1 fish. Results indicated no difference among catfish oil, menhaden oil, and tallow as dietary energy sources for channel catfish raised in ponds from fingerling size to 1-kg body weight.

PCDD, PCDF, and PCB in farm-raised catfish from Southeast United States - concentrations, sources, and CYP1A induction

Nine catfish fillets, three catfish nuggets, two feed samples, and one pond sediment were analyzed for PCDD, PCDF, and PCB. Farm-raised catfish from Mississippi, Alabama, and Arkansas contained significant levels of 2,3,7,8-substituted PCDD and PCDF. In addition, a large number of non-2,3,7,8-substituted congeners were present in all samples. The catfish fillets and catfish nuggets also contained high concentrations of dioxin-like PCB, as well as a number of non-dioxin-like PCB. The TEQ based on PCDD and PCDF ranged from 9.5 to 43.0 pg/g lipid and the TEQ based on PCB ranged from 0.45 to 4.9 pg/g lipid for all catfish samples. The dioxin-like PCB contributed 4–16% to the total TEQ (PCDD/PCDF/PCB) for the catfish samples. The major source for the PCDD, PCDF, and PCB appears to be from feed and not from pond sediment. Immunoreactive CYP1A protein was elevated 2.5 fold in the pond-raised catfish compared to the aquarium-raised one. The results of this study suggest that the PCDD/PCDF are more important than the PCB in the CYP1A Induction.

Changes in serum concentrations of channel catfish ( Ictalurus punctatus Rafinesque) phosphorylcholine-reactive protein ( PRP) in response to inflammatory agents, low temperature-shock and infection by the fungus Saprolegnia sp.

Channel catfish ( Ictalurus punctatus Rafinesque) produce a 100-kDa serum protein referred to as phosphorylcholine-reactive protein (PRP). PRP appears homologous to human C-reactive protein (CRP) i.e. it is an acute phase pentraxin with calcium-dependent reactivity with phosphorylcholine. In this study a immunoassay was employed to quantify PRP levels in sera of pond-raised catfish collected at monthly intervals (January 1990 to January 1992) from ponds in Mississippi. Serum PRP was also measured in laboratory-maintained catfish exposed to physical, environmental, or chemical stressors and for catfish infected with the fungus Saprolegnia sp. For pond-raised catfish the average level of serum PRP was 2·42 ± 0·85 mg ml -1 for healthy animals and 1·74 ± 0·94 mg ml -1 for those infected with Saprolegnia sp. In general PRP levels were maximal in summer and minimal in winter, coincident with similar extremes in pond-water temperature. Levels of serum PRP for laboratory-maintained catfish were higher and more variable (3·8 ± 2·4 mg ml -1) than those for pond-raised fish. Within 2-4 days after injection with turpentine, serum PRP levels in laboratory-maintained catfish rose to concentrations as high as 10·6mg ml -1, representing an 18-fold increase over pre-injection levels. In contrast, fish injected with pneumococcal C-polysaccharide or Saprolegnia sp. fungal homogenate exhibited transient decreases in serum PRP levels. Concentrations of serum PRP for catfish subjected to low temperature-shock decreased 14% compared to pre-shock values by day 6 and 86% by day 18. In contrast, by day 6 fish subjected to low temperature-shock and subsequently infected with Saprolegnia sp. exhibited PRP levels 57% lower than healthy fish and 50% lower than healthy, low temperature-shocked fish. Several lines of evidence suggest that reduced levels of serum PRP induced by low temperatures may play a major role(s) in determining the increased susceptibility of channel catfish to infection by Saprolegnia sp. during the winter months.

Microbiological assessment of channel catfish grown in cage and pond culture

Channel catfish (Ictalurus punctatus) grown in cage and pond culture were collected from South Georgia. Bacterial indicators and pathogens of pond water and fish samples were assessed. Microbial changes on processed catfish packaged with wrapping or vacuum packed were analyzed during 16 days of refrigerated (4°C) storage. Results showed that water for cage culture had significantly higher (P < 0·05) fecal streptococci and Aeromonas hydrophila populations than water for pond culture. This difference in water and bacteria was reflected in the microbial populations on skin rinse fluid of the catfish. On both cage- and pond-raised catfish, bacterial counts were reduced by processing procedure. However, on the eighth day of cold storage both cage- and pond-raised catfish packaged in vacuum bags had lower (P < 0·05) bacterial counts than catfish packaged with wrapping.

Household demand for catfish in Louisiana

Addressing the lack of information on the demand for specific aquaculture species, this article presents the results of a cross-sectional analysis of consumer demand for commercial pond-raised catfish in Louisiana. Results indicate that size of household and Catholic religious preference positively influenced the consumption of pond-raised catfish. However, children present in the household negatively influences the household's expenditures for pond-raised catfish fillets. The number of years that a household has resided in Louisiana is positively associated with expenditures on catfish. Empirical analysis also indicates that catfish fillets are perceived to be an inferior good in Louisiana, which agrees with previous research results.