Evaluation of Three Sorghums as Potential Alternative Forages for Crawfish Culture 1

Three cultivars of Sorghum bicolor (L.) Moench (grain sorghum, forage sorghum, and a sorghum sudangrass hybrid) were evaluated as planted forages for crawfish (Procambarus spp.) in two simulated culture systems, double cropping and crawfish monoculture. Based upon ease of culture, biomass production, and biomass degradation characteristics, grain sorghum and sorghum sudangrass exhibited great potential for either system. With the added advantage of grain production, grain sorghum represents the more attractive option and may provide farmers with a viable alternative to rice for double cropping with crawfish. The sorghum sudangrass produced large amounts of vegetative biomass and also represents a worthwhile forage option for the crawfish fanner. Either of these plants is conveniently incorporated into existing farm operations and could provide options as producers strive to integrate crawfish aquaculture with conventional agriculture.     

Effects of Supplemental Feeding on Harvest of Red Swamp Crawfish,Procambarus clarkii,in Forage‐based Ponds

Procambarid crawfish aquaculture in the USA relies on an established forage‐based system for providing sustenance for growing crawfish. These systems may become inadequate at times for providing sufficient nourishment to support maximum growth of the population. Supplemental feeding is not routinely used because management recommendations for the cost‐effective use of supplemental feeds in ponds are not available. Because crawfish under confinement readily consume and grow well when fed single feedstuffs, such as rough rice seed and whole, raw soybeans, this study was initiated to investigate the use of these readily available low‐cost feedstuffs as supplemental feeds in aquaculture ponds. Earthen ponds (0.2 ha), constructed and managed to simulate commercial crawfish ponds, were used over three consecutive production seasons to evaluate the effects of supplemental feeding on yields and size of crawfish. Treatments for Seasons 1 and 2 consisted of (a) hull‐on rough rice seed, (b) whole raw soybean, (c) formulated 25% crude protein pellet, and (d) no supplementation and were replicated in four and three ponds for Seasons 1 and 2, respectively. Treatments for Season 3 consisted of (a) whole raw soybean and (b) no feed, with 10 replicated ponds each. Feeding frequency was established each year, and feeding rates were adjusted according to predetermined guidelines and monitoring of feeding trays. Crawfish harvesting was conducted by baited wire‐mesh traps and all harvested crawfish were subjected to a mechanical grader and sorted into three size classes. Results show that supplemental feeding, while trap‐harvesting operations are underway, can reduce yields and generate a negative economic benefit, perhaps as a result of residual feed within the pond rendering the baited trap less effective.     

The use of information technology in aquaculture management

Abstract

The recent advances in information technology (IT) have had profound impacts on all walks of life and aquaculture is no exception. The growing importance of aquaculture as an alternative source of protein has further emphasized the need to adapt and develop advanced IT for the better management of aquaculture facilities as well as the regional planning for aquaculture development.

It is the objective of this paper to review the use and potential prospects of IT in aquaculture management. The information technologies considered are instrumentation and process control, data management, computerized models, decision support systems, artificial intelligence and expert systems, image processing and pattern recognition, geographical information systems, and information centres and networks. The review includes a brief introduction of each of the aforementioned technologies, followed by a survey of their current application as well as their potential use in aquaculture management.     

Pre-Flood Evaluation of Seven Grasses (Graminae L.) as Planted Forage for Crawfish1

Seven potential alternatives to rice (Oryza sativa) as planted forage for pond production of crawfish in southwest Louisiana were evaluated. Browntop (Panicum ramosum L.), Japanese [Echinochloa crusgulli var. frumentacea (Roxb.) Wight], proso (Panicum miliaceum L.), and pearl [Pennisetum typhoides (Burn.) Stapf & C.E. Hubb] millets were compared with volunteer weeds (primarily Cyperus spp.), grain sorghum [Sorghum bicolor (L) Moench] and a sorghum sudangrass hybrid [S. bicolor (L.) Moench]. Early maturation and rapid senescence and decomposition characterized all except the two sorghums and pearl millet. The sorghum sudangrass was superior in biomass production and exhibited slow senescence. Grain sorghum and pearl millet also exhibited characteristics which might be desirable for use in some crawfish production ponds.     

Effectiveness of Commercially Formulated and Fish Baits in Trapping Cambarid Crawfish1

In the USA, cambarid crawfishes are harvested commercially with traps baited with fishes, formulated baits, or a combination of the two. Commercially formulated baits and fish baits, done and in combination, were evaluated to assess their relative effectiveness M attractants for crawfish. Traps baited with a combination of fish and formulated bait generally captured the most crawfish. Traps baited with common carp, the most effective natural bait, captured more crawfish than traps baited with skipjack herring, gizzard shad or channel catfish heads. Crawfish harvest from traps baited with several types of commercially formulated baits was equal to that obtained with traps baited with either gizzard shad or skipjack herring. Population density of crawfish and the availability of natural forage did not appear to influence relative effectiveness of either formulated baits or fish baits.     

Effects of the estrogen mimic genistein as a dietary component on sex differentiation and ethoxyresorufin-O-deethylase (EROD) activity in channel catfish (<Emphasis Type="Italic">Ictalurus punctatus</Emphasis>)

A number of aquaculture species, including channel catfish Ictalurus punctatus, are fed high proportions of soybean meal in their diet. We have investigated the potential for the most common phytoestrogen in soybean meal to alter phenotypic sex during sexual differentiation in channel catfish. Channel catfish were fed four dietary concentrations of the phytoestrogen genistein (0, 2, 4, and 8 mg g⁻¹) to determine its effect on gonadal sex differentiation. The four treatment diets were fed to sexually undifferentiated channel catfish between 5 and 140 days post hatch (dph) and between 60 and 150 dph. Phenotypic sex was determined by histological examination of the gonads. Ethoxyresorufin-O-deethylase activity was not significantly different among the treatment and control groups. Phenotypic sex was significantly dependant on dietary phytoestrogen concentration (P = 0.01). Additionally, logistic regression showed a significant relation between genistein concentration in the diet and gonadal sex (P = 0.02). Intersex individuals were present at all treatment concentrations, with increasing proportions of intersex fish as the genistein concentration increased for individuals fed treated diets between 5 and 140 dph. Increased proportions of phenotypically male individuals resulted from chronic dietary exposure to the estrogen mimic genistein. There were no significant differences in the proportions of males and females between feed treatment durations. These findings establish that dietary concentrations of genistein can alter sex ratios in cultured channel catfish populations and demonstrates the need to further understand the actions of this and other prominent phytoestrogens in aquaculture species.     

The economic impact of feeding restrictions on US catfish, Ictalurus punctatus (Rafinesque), aqafuaculture operations

Increasing stocking densities in catfish, Ictalurus punctatus (Rafinesque), aquaculture are making maintenance of water quality a crucial element of production strategy. A bioeconomic simulation model for catfish has been adapted to assess alternative feeding restriction management strategies for US catfish aquaculture operations. The current model includes five decision variables: feeding rate, diet quality, stocking weight, stocking date, and length of growing season. The growth model follows a bioenergetics approach, where the balance between energy intake and energy expenditure determines fish growth. The purpose of this analysis was to simulate changes in production practices resulting from water quality restrictions. Model simulations indicate that restricting maximum daily feeding allowance to maintain higher water quality will actually increase feed requirements to reach a harvestable fish size. In addition, as producers increasingly attempt to spread harvests throughout the year, both for their own cash flow needs and the consistent supply requirements of processors, restricting daily feed allowance will make summer harvests particularly difficult.     

中国深远海养殖发展方式研究

在渔业转型发展进程中,发展深远海养殖是突破生态环境和自然资源约束性挑战,实现新时期中国海水养殖业可持续发展的战略方向。基于联合国粮食及农业组织(FAO)关于深远海养殖发展的定义,结合中国海水养殖业发展水平和海域条件,对中国深远海养殖概念进行了界定。提出养殖品种选择、养殖系统构建、养殖海域规划是关系深远海养殖产业稳步有序发展的重要因素。在养殖品种选择方面,应重点考虑经济潜力、适应水温和养殖技术;在养殖系统构建上,分析比较了不同养殖系统应用于深远海养殖的适宜性、安全性和经济性;在养殖海域规划方面,应重点考虑养殖排放、环境承载力和海域条件。     

Histological and computed tomographic evaluation of a parasitic conjoined twin in hybrid catfish (Ictalurus punctatus [Rafinesque] X Ictalurus furcatus [Lesueur])

There is growing use of hybrid catfish (Ictalurus punctatus ♀ X Ictalurus furcatus ♂) in commercial aquaculture to utilize hybrid vigour to improve production A conjoined twin specimen found during the course of production studies by the United States Department of Agriculture Catfish Genetic Research Unit (USDA‐CGRU) was submitted to the Aquatic Research and Diagnostic Laboratory (ARDL). After preliminary inspection, it was transported to Mississippi State University, College of Veterinary Medicine for further evaluation. The specimen was examined using both computed radiography and computed tomography antemortem. Following humane euthanasia, the specimen was examined both grossly and histologically. Tissues from both fish were also submitted for genetic analysis to determine whether twins were derived from the same egg. This report records the presentation and examination of a pair of conjoined hybrid catfish (I. punctatus X Ictalurus furcatus).     

Analysis of the use of credit facilities by small-scale fish farmers in Kenya

The government of Kenya encourages aquaculture development by offering credit facilities through the government agricultural finance institution, Agriculture Finance Corporation. Nevertheless, the level of credit use in fish farming is very low. Access to credit is among several factors that affect farmers’ decision of whether to use particular technology or services. The study examined factors that affected the decision of fish farmers in Kenya to utilize credit facilities in fish production using a probit model. The analysis suggests that farmers in the Western province will have a 19% more probability of using credit facilities for their fish farming operations than farmers from the other provinces such as the Rift Valley, Central, and the Eastern province. The effect of tilapia sales on the probability of credit use by fish farmers is more than three times that of catfish sales. Total pond acreage owned by fish farmers had a positive effect on credit use but the effect was very small and negligible. The level of fish farmers’ use of credit facilities is very low, and there is probably the need to educate farmers on credit use and for the government agricultural lending agency and other commercial agricultural lenders to invest in this enterprise. Kenyan lending institutions have financed traditional agricultural enterprises, and with the growing production of farmed fish, more research is needed to document the aquaculture business model to assist in assessing the profitability potential in aquaculture.     

A mathematical model for soft-shell crawfish production

A mathematical model was developed for soft-shell crawfish production management based on the assumption that the crawfish molt interval follows a normal distribution. The mean and standard deviation of the molt interval, the two main parameters of the model, were estimated to be 48 and 15 days, respectively, based on experimental data for the red swamp crawfish (Procambarus clarkii). The model was further verified through comparison with experimental data. Simulations using the model were conducted to evaluate the impact of mortality and management strategies upon soft-shell crawfish production. The results indicated that mortality is a major factor in determining the production rate of a soft-shell crawfish facility. For a 6-month operation period, the predicted total production is 263% of the loading capacity for a mortality rate of 1%/day. This production will drop to 101% of the loading capacity with a mortality rate of 5%/day. Besides variations in the mortality rate, loading and replacement strategies also affect soft-shell crawfish operation, as demonstrated by the simulation results.     

Influence of Simulated Double‐crested Cormorant,Phalacrocorax auritus,Predation on Multiple‐batch Production of Channel Catfish,Ictalurus punctatus

The double‐crested cormorant, Phalacrocorax auritus, is considered the primary depredating bird species on commercially produced channel catfish, Ictalurus punctatus, in the southeastern USA. We simulated different levels of cormorant predation on losses at harvest and economic effects on channel catfish production in a multiple‐batch cropping system. We observed significant (P < 0.05) declines in catfish production at increasing levels of cormorant predation in this study. This decline was mitigated by increased individual growth of catfish at higher predation rates (i.e., lower catfish densities). This mitigating effect produced a non‐linear relationship with total kg of catfish harvested per pond resulting in a non‐linear incremental increase in breakeven price related to predation. Costs of production ($/kg) increased with increasing predation levels up to very high levels of predation with a cumulative maximum increase in breakeven price of $0.143/kg. These results indicate that losses at harvest due to cormorant predation occur immediately but are mitigated in part by compensatory growth of individual catfish. Losses due to cormorant predation in multi‐batch systems can be considerable, but there is not a 1:1 relationship between losses and kg of catfish harvested due to compensatory factors.     

An Analysis of Nearly One Billion Dollars of Aquaculture Grants Made by the US Federal Government from 1990 to 2015

The aquaculture industry relies on federal investments to stimulate aquaculture research and development (R&D). We conducted this study to track federal spending for aquaculture using a large database of 2957 US federal research grants awarded from 1990 to 2015. During that period, 1.04 billion US dollars (USD) were spent on aquaculture research, with 919 million USD from federal agencies and 123 million USD in matching funds. By comparison, over the same time frame, the US Department of Agriculture's R&D spending was 41 billion USD. Federal grant funding for aquaculture had a 37‐fold return on investment since 2000. Microalgae, oysters, salmon and trout, catfish, and shrimp received the most grant support, and the most common topics/disciplines were aquaculture production sciences, aquatic animal health and disease, genetics and breeding, and nutrition. Our findings can be used to identify research gaps and inform federal policy, grant making, and budget allocation.     

Analyzing Production Feasibility and Market Potential For Florida Aquaculture Catfish Products

A spatiotemporal linear programming model (GAMS) was constructed to simulate the catfish production and marketing system in the U.S. in order to study the economic feasibility of Florida entering the aquaculture catfish industry. Evaluation of base model results and sensitivity analysis were used to identify constraints to the potential expansion of the catfish industry in Florida. Results indicated production and processing costs were more important in determining the locus of production and processing than were processing capacity, storage costs and capacity, and transportation costs. Thus, existing industry geographic concentration is likely to continue, but small new processing plants could develop proximate markets for fresh product.     

Inherent variation in growth efficiency of African catfish Clarias gariepinus (Burchell, 1822) juveniles

Understanding the major causes of growth variation is crucial for the success of fish farming since its reduction contributes to maximize production efficiency, reduce food waste and improve water quality. The growth variation observed in aquaculture has been associated with the establishment of social hierarchies. However, some studies suggest that this variation may not be mainly a consequence of social hierarchies but mainly a result of inherent (genetic) differences. This study investigates the magnitude of individual responses, independently of group effects (fish housed individually), in growth efficiency and feeding behaviour of African catfish Clarias gariepinus (Burchell 1822). Despite the low variation in initial body weight (6.5%) and cumulative feed consumption (7.5%) over the experimental period, catfish exhibited high variation in final body weight (18.1%), specific growth rate (17.2%) and feed conversion ratio (27.9%), suggesting that individual variation in growth efficiency is important in determining growth rate. This individual variation may be related with individual differences in protein/fat deposition since faster growing fish deposited more protein and less fat than slower growing fish. Pronounced individual differences in feeding behaviour (reaction towards feed and time spent eating) were also observed and correlated with individual differences in growth efficiency. Fast eaters were the fast growers. We suggest that the growth variation observed in African catfish may be inherent and that the use of grading to increase uniformity should be further investigated.     

Cost of regulations on US catfish farms

Understanding the economic effects of regulations on US aquaculture farms provides insights into which compliance costs create the greatest compliance burden on farms. This can further guide strategies to improve the efficiency of regulatory frameworks and potentially reduce on-farm compliance costs while maintaining adequate oversight. This study estimated the regulatory compliance burden on US catfish farms as part of a national effort to quantify the cost of regulations on US aquaculture farms. Completed survey interviews of catfish farms in the major catfish-producing states covered 63% of the total US catfish production area. Total regulatory costs of the US catfish industry were estimated at $45 million annually. Lost farm revenues (measured as the value of lost production, the value of markets lost from regulations, and the value of business opportunities lost because of regulations) were estimated to be $35 million per annum. Catfish-producing states outside the Alabama/Arkansas/Mississippi region had the highest ($2856/ha) and Alabama the lowest ($1127/ha) regulatory costs per hectare among the surveyed states. The greatest regulatory cost burden on catfish farms ($18 million) was caused by environmental regulations related mostly to the management of federally protected piscivorous migratory birds, followed by labor regulations ($12 million), and taxes/insurance ($7 million). Regulatory costs ($/kg) were 2.6 times higher on smaller (<80 ha) farms relative to larger (>300 ha) farms. Attention is needed to identify alternative regulatory frameworks that provide the same degree of regulatory oversight but are more cost-efficient.     

Effect of ethanol, clofibric acid and temperature on the uptake and elimination of 2-methylisoborneol in channel catfish (Ictalurus punctatus)

Off-flavor, due to organoleptic compounds such as 2-methylisoborneol (MIB), is the single largest detriment to the harvest, production and profit from the channel catfish aquaculture industry of the Southeastern United States. Methods to increase the metabolism and/or elimination of compounds like MIB would provide a means towards improving catfish rearing practices. Previous studies indicated one or more forms of cytochrome P450 monooxygenase (CYP) may be involved in the biotransformation and elimination of specific organoleptic compounds, such as 2-methylisoborneol (MIB). In order to determine the role of CYP in the elimination of MIB, various compounds that have been shown to modulate cytochrome P450 expression in catfish were administered before and after exposure to ¹⁴C-MIB. Uptake and elimination was monitored in fish over 24 and 48 h, respectively. Pretreatment with clofibric acid (100 mg kg^–1-gavage) which induces a CYP2K-like isoform, and ethanol (1.0% v/v-aqueous) a CYP2 represser, alone and with enhanced temperature (added 10 °C) failed to affect uptake of MIB. Pretreatment with these compounds and conditions also failed to enhance elimination of MIB from channel catfish. However, when fish were treated with 1.0% ethanol after MIB exposure (i.e., during depuration), beta elimination halflives were changed from 144±35 to 71±13 h. in sexually mature animals but unchanged (191±113) in juveniles. The failure of CYP-modulating agents to alter MIB elimination in catfish suggests MIB may not readily undergo Phase I oxidation via CYP. The enhanced elimination of MIB in adults by ethanol warrants further study as to its potential use in aquaculture in purging MIB and related compounds prior to fish processing.     

Evaluation of Diquat as a Potential Algicide for Controlling the Musty-Odor-Producing Cyanobacterium,Oscillatoria perornata,in Catfish Aquaculture Ponds

ABSTRACT

The synthetic herbicide diquat was applied to a catfish aquaculture pond containing a heavy bloom of the cyanobacterium Oscillatoria perornata(a major contributor to musty off-flavor in farm-raised catfish) in order to determine the effectiveness of diquat as a selective algicide to prevent musty off-flavor in cultured catfish. Levels of the musty-odor compound 2-methylisoborneol (MIB) and numbers of O. perornata were monitored. Results indicate that diquat is not useful as an algicide for controlling O. perornata in catfish aquaculture ponds, despite its usefulness in controlling other aquatic weeds.     

The evolution of farm management,production efficiencies,and current challenges to catfish production in the United States

Abstract

The catfish industry is the most successful aquaculture business in the US. The development and growth of the catfish industry has resulted in complex fish farm businesses that require intensive management. Technological innovations have resulted in increased yields (land use efficiency). However, in more recent years, productivity gains have not kept pace with the rate of increase in input costs. Increasing intensification of catfish production over time has been accompanied by increased use of debt capital that results in higher levels of financial risk. While still a profitable activity, real profit margins have declined as financial risk has increased. New technologies will likely continue to increase productivity over time. Market‐oriented agribusiness approaches to catfish marketing are likely to become the norm. The challenge for the catfish industry is to coordinate adoption of new higher‐cost technologies with demand increasing market development to sustain farm price levels.     

USE OF A SEINE TO DETECT STUNTED CRAWFISH POPULATIONS IN PONDS,A PRELIMINARY REPORT1

A 4.5-m long bag seine was used to sample crawfish from six 0.04 ha experimental ponds. Length-frequency histograms were evaluated as a predictor of size structure and to detect stunted populations of crawfish. The findings demonstrated importance of determining size structure of crawfish in predicting stunting and harvest potential of a population. Distinct differences in size structure of crawfish populations were apparent by 6 and 12 weeks after flooding ponds. Crawfish populations, with over 45% of the individuals exceeding 75 mm total length after 12 weeks, produced 25 to 30% greater yields than populations in which less than 5% of the crawfish exceeded 75 mm at 12 weeks post-flooding.