ABSTRACT Objective The purpose of this study was to evaluate the efficacy of the aquatically formulated humic acid product AC Aqua in reducing total phosphorus concentrations and controlling the proliferation of two harmful algal species, golden algae Prymnesium parvum and Microcystis aeruginosa. Methods Three treatments of AC Aqua (prophylactic, low dose, and high dose) and a control were tested in 13.3-L mesocosms with and without sediment (n = 6 per treatment) to simulate lined and earthen pond conditions. Prophylactic treatment (5 mL/m3) was applied 10 d before P. parvum (91 cells/mL) and M. aeruginosa (246 cells/mL) inoculation. Low (5 mL/m3) and high (7.67 mL/m3) doses were applied 6 h after inoculation. Phosphorus concentrations were measured before and after application to assess binding, while algal cell counts were monitored weekly for 7 weeks for each trial. Results Within 6 h, all AC Aqua treatments reduced total phosphorus, with the high-dose and sediment treatments having a significant reduction in phosphorus, compared with control groups, in both trials. Significant reductions in P. parvum cell counts were observed in the prophylactic treatments beginning in week 3 (P = 0.017). By week 7, all treatments had substantially lower cell counts compared with controls, with several treatment groups, particularly those with sediment, falling below 10,000 cells/mL, while control groups remained above 90,000 cells/mL. Significant reductions in M. aeruginosa cell counts were observed in the prophylactic treatments beginning in week 2 (P = 0.014). By week 6, all treatments were below 10,000 cells/mL, while control groups remained above 65,000 cells/mL. Conclusions AC Aqua effectively reduced P. parvum and M. aeruginosa cell densities in eutrophic systems when applied prophylactically. Its lag effect indicates a nutrient management mechanism, supporting its use as a sustainable, preventative strategy.

ABSTRACT Objective Cultured catfish are subjected to cold temperatures during winter, as aquaculture ponds are relatively shallow (<1.5 m) and experience seasonal thermal fluctuations. Cold temperatures reduce metabolic processes; however, little is known about comparative differences in metabolic rates, swimming performance, and blood metabolites among principal types of cultured catfish. Therefore, the objective of this study was to address this knowledge gap for catfish types used in the U.S. aquaculture industry. Methods Standard metabolic rate, maximum metabolic rate, metabolic scope, critical swimming speed (Ucrit), and blood metabolites were analyzed at 10°C and 20°C in juvenile Channel Catfish Ictalurus punctatus, Blue Catfish I. furcatus, and hybrid catfish (Channel Catfish × Blue Catfish). Results It was hypothesized that hybrid catfish would have greater metabolic and swimming performance than Channel and Blue catfishes across experimental temperatures due to heterosis. However, metabolic scope and Ucrit did not vary among fish types, but Ucrit was reduced among all fish types at 10°C. Lactate and glucose concentrations were higher and blood pH was lower in fatigued catfish, with Channel Catfish generally differing in blood metabolites from Blue and hybrid catfishes. Conclusions Results indicate that prolonged exposure to cold temperatures limits metabolic processes and swimming capacity, ultimately requiring catfish to allocate energetic resources to maintenance metabolic requirements. Although no distinct comparative advantage was found for any of the catfish types at low temperature, long-term health and survival likely relate to energy stores accrued prior to and during exposure to cold temperatures. These findings provide useful comparative metrics to direct future efforts into investigating the physiological and environmental mechanisms affecting the catfish aquaculture industry.

ABSTRACT Objective The objective of this study was to quantify the cascading effects on the pond ecology and water quality that result from mechanically harvesting large zooplankton (>250 µm) and to track the nutritional value of zooplankton over time. Methods Eight 0.04-ha ponds, containing no fish, were selected. In four ponds, a 373-W submersible pump was suspended in the water column and allowed to pump continuously for 4 d per week (treatment ponds) to collect zooplankton in 250-µm mesh bags. The other four ponds contained no submersible pump and were used as control ponds. The harvested zooplankton were subjected to proximate analyses to determine their base nutritional makeup. Weekly samples were analyzed for water quality, phytoplankton, and zooplankton. Results The nutritional value of zooplankton varied over time and was negatively influenced by ostracod abundance. There was no overall influence of treatment on water quality or total phytoplankton or zooplankton abundance; however, the effects for sampling date and the interaction of treatment and sampling date were significant. Over time, Cyanophyta continually increased in the control ponds but decreased in the treatment ponds. Chlorophyta decreased in the control ponds but slightly increased in the treatment ponds. Generally, zooplankton abundance increased throughout the summer in all the ponds. However, the treatment ponds typically had lower abundances, on average, than the control ponds. Zooplankton abundance was also much more variable in the control ponds than in the treatment ponds. Conclusion Zooplankton maintain adequate nutritional value over time as long as ostracod density remains low. The results of this study show that harvest pressure from capturing zooplankton resulted in the stabilization of the phytoplankton and zooplankton populations, particularly as the study moved further into the summer and communities were established. This shows promise as an effective method to harvest zooplankton for small-scale feed supplementation while improving the pond community by increasing Chlorophyta populations, reducing the variance in zooplankton populations, and reducing the variance and possibly the density of Cyanophyta.

ABSTRACT Objective This study was designed to explore the relationship between bacterial communities in different habitats and analyze how water quality affects the structure of bacterial communities and the distribution of pathogenic bacteria. The findings support healthy cultivation of red swamp crayfish Procambarus clarkii in rice–crayfish coculture systems and assist in assessing the health risks to the ecological environment. Methods The researchers used 16S ribosomal RNA gene sequencing to investigate the composition and diversity of the bacterial community in the crayfish gut and environment (water and sediment) in rice–crayfish coculture systems across various growth stages (larvae, juvenile, and adult). The water quality parameters were measured at different stages, and the duration of the investigation was 3 months. Results The bacterial communities in sediment showed higher α-diversity values than those in water and the crayfish gut microbiota. Proteobacteria dominated in all environments, particularly in the gut, whereas Acidobacteria and Chloroflexi were prevalent in sediment and Cyanobacteria and Verrucomicrobia in water. Gut microbiota exhibited significant shifts over the developmental stages, with increased prevalence of pathogens like Aeromonas and Acinetobacter. The SourceTracker analysis revealed a minimal contribution of sediment to gut microbiota, with water contributing significantly to gut microbiota at the juvenile stage. Environmental factors including dissolved oxygen, total phosphorus, orthophosphate, chemical oxygen demand (CODMn), and chlorophyll a have the greatest influence on bacterial communities. Notably, a pathogenic bacterium, Acinetobacter lwoffii, which was detected both in the gut (9.79–36.83%) and in the water (0.00–12.47%), showed a significant correlation with CODMn levels (P < 0.05). Conclusions The contribution to gut bacteria of the bacterial community in water was greater than that of the bacterial community in sediment. Environmental dissolved oxygen, total phosphorus, orthophosphate, CODMn, and chlorophyll a molded the bacterial community, especially the increase of CODMn, which can promote the distribution of intestinal pathogens. These results provide scientific reference for healthy crayfish culture, prevention of bacterial disease transmission, and health risk assessments of the ecological environment.

ABSTRACT Objective The hybrid catfish (male Blue Catfish Ictalurus furcatus × female Channel Catfish Ictalurus punctatus) is rapidly replacing the Channel Catfish as the fish of choice in the catfish industry of the southern United States. The objective of this study was to characterize survival and physiological responses in market-size (0.6–1.8 kg) hybrid catfish during capture from ponds and transport and before unloading them at a processing plant. Methods Ten commercial harvest and transport events were monitored over a year, allowing water temperature also to be considered. Survival and blood chemistries related to the stress response were monitored. Results All the fish survived seining, holding, transport, and unloading. Plasma cortisol, glucose, and lactate levels generally increased from harvest to arrival at the processing plant, whereas plasma osmolality remained unchanged. The fish that were harvested from warmer temperatures (25–32°C) demonstrated higher plasma glucose, lactate, and osmolality values than those that were harvested from cooler temperatures (9–16°C). Conclusions It appears that hybrid catfish tolerate harvest and transport well. The fish survived, demonstrated expected primary and secondary stress responses, appeared to remain largely aerobic during the events, and maintained acceptable water balance.

ABSTRACT Objective Invasive carp, a name encompassing Black Carp Mylopharyngodon piceus, Silver Carp Hypophthalmichthys molitrix, Bighead Carp H. nobilis, and Grass Carp Ctenopharyngodon idella, are outcompeting native fish and causing environmental instability in the lower Mississippi River basin. Harvest by commercial fishers is the most cost-effective management strategy. However, low demand and dockside prices have reduced incentives for commercial fishers to target invasive carp, reducing annual harvest numbers. Currently, the aquaculture industry relies on fish meal and fish oil from marine fish species, such as Atlantic Menhaden Brevoortia tyrannus, as important ingredients for many diets. However, as the industry continues to grow, demand for these marine fish will surpass availability. Methods In this study, we assessed the performance of invasive carp fish meal (ICFM) and invasive carp fish oil (ICFO) as feed ingredients for Channel Catfish Ictalurus punctatus. Graded levels of ICFM and ICFO (Aquatic Protein LLC, Beardstown, Illinois) were incorporated into starter diets. The diets were formulated on a 35% crude protein, 6% fat basis and designed to meet the amino acid requirements of Channel Catfish. In two 8-week feeding trials, ICFM was used to replace Atlantic Menhaden fish meal (MFM) or all plant and animal protein sources (MFM, soybean meal, corn protein concentrate; trial 1) and ICFO was used to replace 50% or 100% of the Atlantic Menhaden fish oil (trial 2). During these feeding trials, triplicate tanks of Channel Catfish were fed one of six treatment diets and growth, feed intake, feed efficiency, proximate composition, and protein and energy retention efficiency were assessed. Terminal measurements were also used to calculate values for condition factor, viscerosomatic index, and muscle ratio. Results There were no significant differences in the growth performance or composition of Channel Catfish when ICFM was included as up to 47% of the diet dry weight. Replacing plant and animal protein with ICFM enhanced energy retention efficiency relative to a diet where ICFM replaced only MFM. Similarly, growth performance was maintained when ICFO was used in place of 100% of MFM. This suggests that ICFM and ICFO are suitable alternative ingredients in Channel Catfish starter diets. Conclusions Invasive carp products offer suitable ingredient alternatives that can be used in starter diets for farmed Channel Catfish. This has the potential to enhance market demand for invasive carp, thereby benefiting fisheries and local economies, improving conservation and invasive species management in the Mississippi River basin, and enhancing the overall sustainability of aquaculture.

ABSTRACT Objective We investigated the effect of feeding frequency (FF-2 [2 times/d], FF-3 [3 times/d], FF-4 [4 times/d], and FF-5 [5 times/d]) on nursery-based co-culture of Pacific white shrimp Litopenaeus vannamei and giant river prawns Macrobrachium rosenbergii in a biofloc system. Methods The growth parameters, proximate composition, and hemocyte status of L. vannamei and M. rosenbergii were calculated. The physicochemical parameters, total bacterial load, and proximate composition of the biofloc were also measured among the treatments. Molasses was added (C:N ratio = 10:1), and salinity was 15‰. The experiment utilized twelve 125-L tanks, each containing 100 L of water. Each tank was stocked with 100 postlarvae, comprising 50 L. vannamei (mean ± SD = 28.38 ± 0.54 mg) and 50 M. rosenbergii (25.62 ± 0.31 mg). Results For L. vannamei, the specific growth rate (%/d) was significantly higher in FF-5 (mean ± SD = 9.87 ± 0.54) and lower in FF-2 (9.30 ± 0.46). For M. rosenbergii, the specific growth rate was significantly higher in FF-3 (5.78 ± 0.46) and lower in FF-2 (5.61 ± 0.46). The survival rate for L. vannamei was significantly higher in FF-5 (mean ± SD = 91.33 ± 6.43%) and lower in FF-2 (86.00 ± 13.86%). For M. rosenbergii, the survival rate was significantly higher in FF-5 (86.00 ± 7.21%) and lower in FF-2 (72.00 ± 10.58%). The feed conversion ratio was significantly better in FF-5 (1.29) for L. vannamei, whereas it was significantly better in FF-3 (2.08) for M. rosenbergii. Significantly higher hemocyte counts were recorded in FF-5 for both species. For L. vannamei and M. rosenbergii, significantly higher levels of crude protein, lipid, and ash were recorded in FF-5. The benefit–cost ratio was higher for FF-5 than for FF-4, FF-3, or FF-2. Conclusions This study indicates that higher feeding frequencies improved the survival rate of L. vannamei and M. rosenbergii and enhanced their economic viability, productivity, and sustainability in aquaculture.

ABSTRACT Objective Black Sea Bass Centropristis striata are a temperate reef finfish that occupy natural and artificial structured habitats. This study used fish behavior, condition indices, and production estimates to evaluate how oyster aquaculture cages serve as artificial reefs for Black Sea Bass in central Long Island Sound, USA. Methods Underwater video was recorded on oyster farms and a natural rock reef to identify and quantify the behavior of Black Sea Bass that is associated with oyster aquaculture cages and boulders. Juvenile Black Sea Bass were sampled from farms and reefs in Clinton and Milford, Connecticut, to assess individual energy density and relative condition factor as measures of habitat quality. Proximate analysis was conducted to develop a predictive regression for percentage of dry weight and energy density in juvenile Black Sea Bass, which was then applied to estimate energy density in fish that were collected from farms and reefs. The abundance of young-of-the-year Black Sea Bass was used to quantify fish production on the oyster farms. Results Significantly greater shelter and grouping activity were observed on cages than were observed among boulders. Instances of courtship/reproduction in mature fish, escape, foraging, and territorial behavior were statistically similar across the cage and boulder habitats. The condition metrics of energy density and relative condition factor showed no difference in the physiological status of juvenile fish that inhabited farms versus reefs. The enhanced production of Black Sea Bass was estimated to be 4.1 kg/100 cages per year based on higher abundance of young-of-the-year fish on farms relative to the rock reef reference habitat. Conclusions Our results suggest that aquaculture gear provides valuable habitat services that are similar to those obtained via other man-made structures that are considered essential fish habitat for Black Sea Bass throughout their life history.

ABSTRACT Objective The U.S. National Institute of Food and Agriculture-designated Western Region includes some of the top aquaculture-producing states in the country, with important clusters of ­shellfish, trout, White Sturgeon Acipenser transmontanus, and tilapia Oreochromis spp. farms. The objective of this study was to estimate the total farm-level economic contributions (i.e., impacts) from aquaculture farms to the economy of the Western Region. Methods Farm-level observations of expenditures extracted from national surveys of catfish, salmonids, tilapia, and hybrid Striped Bass (White Bass Morone chrysops × Striped Bass M. saxatilis); a regional West Coast shellfish survey; and a survey of Alaskan shellfish growers were used to develop Impact Analysis for Planning models from which economic output, employment, and tax revenue were estimated. Results The economic contribution (impact) of aquaculture to the Western Region was US$885.7 million, with a total economic output multiplier of 1.90. More than 6,000 jobs were supported, two-thirds of which were in direct employment, with an employment multiplier of 1.39. The total contribution of shellfish to the Western Region was $360.6 million, followed by $265.4 million from food fish sold to live markets, $217.9 million from food fish sold to processors, and $50.9 million from fish sold to recreational markets. Aquaculture farms supported 96% of the economic sectors in the Western Region. Conclusions Aquaculture farms in the Western Region make substantial direct, indirect, and induced economic contributions to the local economies where farms are located. The diverse species, production systems, and supply chains in the Western Region resulted in equally diverse expenditure patterns that contributed to a high percentage (96%) of regional economic sectors supported by aquaculture. This study is the first to estimate the economic contribution of aquaculture to the economy of the Western Region.