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Important operational changes that have gradually been assimilated and new approaches that are developing as part of the movement toward sustainable intensive aquaculture production systems are presented via historical, current, and future perspectives. Improved environmental and economic sustainability based on increased efficiency of production continues to be realized. As a result, aquaculture continues to reduce its carbon footprint through reduced greenhouse gas emissions. Reduced use of freshwater and land resources per unit of production, improved feed management practices as well as increased knowledge of nutrient requirements, effective feed ingredients and additives, domestication of species, and new farming practices are now being applied or evaluated. Successful expansion into culture of marine species, both off and on shore, offers the potential of substantial increases in sustainable intensive aquaculture production combined with integrative efforts to increase efficiency will principally contribute to satisfying the increasing global demand for protein and food security needs.

The utilization of seafood processing waste (SPW) is a potential means of reducing aquaculture’s reliance on marine forage fish. Therefore, in an effort to recycle valuable nutrients such as high-quality proteins and polyunsaturated fatty acids from potentially wasted seafood processing, a novel approach was evaluated to enrich plant-derived feedstuffs. Four thermally-processed blends were manufactured by dry-extruding a mixture of either soybean meal (SBM) or distillers dried grains with solubles (DDGS) with two different ratios of SPW (60:40, and 40:60 of SPW: plant-derived feedstuffs on a wet-weight basis). Five diets were formulated to contain 36 % of crude protein and 12 % of lipid, and each of the four blends comprising treatments (SBM 60:40, SBM 40:60, DDGS 60:40, DDGS 40:60) which contributed 30 % of the dietary crude protein, with SBM providing 45 % and FM providing the remaining 25 %. The reference diet had its protein provided solely by FM. Groups of 30 fish (∼98.8 g/fish) were distributed into 15 fiberglass tanks (1200 L), and fed the experimental diets in triplicate to apparent satiation twice a day for 8 weeks. At the end of the trial, four fish per tank had their intestine samples collected and flash frozen to measure digestive enzymes activities. The remaining fish were pooled per treatment, re-distributed into two tanks per treatment, and fed the experimental diets for an additional week. A transport-induced stress challenge was then performed, and fish were transported in a hauling tank for 2 h. Blood hematocrit, and plasma cortisol, lactate and osmolality, were measured from four fish per treatment at five sampling points: prior to and 30 min after transportation, and at 24, 36 and 48 h after the transport-induced stress challenge. Weight gain was significantly affected by the dietary treatments, with fish fed all blends but the SBM 40:60 outperforming those fed the reference diet. Fish fed all treatments also were significantly different from those fed the reference diet for hepatosomatic index. Dietary treatments also significantly impacted, relative to the reference diet, the activity of trypsin, alkaline phosphatase, and amylase. A lower percentage of red blood cells were observed for fish fed SBM 60:40 when compared to those fed the reference diet, but only before the transport-induced stress challenge. Based on the results of this study, the inclusion of both SPW blends had a favorable influence on production performance of red drum while reducing the fishmeal and fish oil in the diet formulation.

The objective of our study was to determine the acute toxicity of 3 common aquatic nitrogenous toxicants to the federally endangered Barton Springs salamander (Eurycea sosorum). Based on our findings, the 96-h median lethal concentrations (96-h LC50) for un-ionized ammonia-N, nitrite-N, and nitrate-N to E. sosorum are 2.0 ± 0.32, 31.7 ± 4.02, and 968.5 ± 150.6 mg/L, respectively. These results establish a benchmark for the tolerance of plethodontid salamanders to these toxicants and indicate that current water quality criteria are adequate for their protection. Environ Toxicol Chem 2017;36:3003-3007. © 2017 SETAC.

Fingerling Red Drum Sciaenops ocellatus were held in water recirculating systems for 4–5 weeks under selected combinations of temperature and salinity: 30°C and 35‰ (reference environment), 34°C and 45‰, or 34°C and 55‰. At the end of the culture period, condition factor, hematocrit, plasma osmolality, plasma lactate concentration, plasma glucose concentration, and liver glycogen content were determined. Responses of fish in the warm, hypersaline treatments did not differ significantly from fish in the reference treatment. Based on the results of this study, juvenile Red Drum can tolerate warm, hypersaline conditions for several weeks with no apparent detrimental effects if slowly acclimated to environmental temperature and salinity as long as food is not limiting and other water quality characteristics are acceptable.Received October 2, 2015; accepted January 4, 2016

A 15-week feeding trial was conducted to evaluate the replacement of fishmeal (FM) with soybean products (SP) in the diet of advanced juvenile red drum, Sciaenops ocellatus . Two dehulled, hexane-extracted SP were evaluated: commodity soybean meal [SBM; 48% crude protein (CP)] and Navita 3010 [N-3010; produced from non-genetically modified, selectively bred varieties; 54% CP]. The additive effect of a prebiotic (GroBiotic®-A; GBA) on the overall performance of red drum also was evaluated. All diets were formulated to contain 35% digestible protein (DP), 15% lipid, and an estimated 3.5 kcal DE kg − 1 . The reference diet was formulated to contain 44.6% Special Select® menhaden FM and 15.0% corn protein concentrate (CPC). Three test diets (SBM, SBM + GBA, and N-3010) were formulated to contain 6.0% FM and 15.0% CPC, together providing approximately 38% of the dietary DP. The remaining 62% DP was provided by 5.7–5.8% soy protein concentrate (SPC) and the specific SP treatment. Diets were fed to apparent satiation to advanced juvenile red drum (mean ± SD = 68 ± 5.1 g initial weight) in each of four replicate 1-m 3 floating-cages. After 15 weeks of feeding, no significant differences were found among treatments for all growth performance and non-specific-immunity parameters evaluated. Based on these results, SBM or N-3010 in combination with SPC can replace approximately 86% of the DP provided by FM in the diet without negatively affecting production performance and health status of advanced juvenile red drum.

We conducted a 26-week study to evaluate the performance of cage-raised hybrid Striped Bass (female White Bass Morone chrysops × male Striped Bass M. saxatilis) fed fish meal (FM) and soybean (SOY; soybean meal + soy protein concentrate) based diets. A FM reference diet was formulated to contain crude protein (CP) at 450 g/kg, lipid at 120 g/kg, and an estimated digestible energy level of 13 MJ/kg. Two test diets (SOY and SOY+GBA) were formulated to replace 70% of the CP in the reference diet with SBM in the absence or presence of GroBiotic-A (GBA), a yeast-based prebiotic, at 20 g/kg. The other 12% of dietary FM in the reference diet was replaced with SPC in the test diets, further reducing FM inclusion to 70 g/kg. Each diet was fed to quadruplicate groups of 40 advanced juvenile hybrid Striped Bass (initial weight ∼ 54 g/fish) stocked into each of twelve 1-m3 floating cages, which were equally divided into four 0.05-ha, rubber-lined ponds according to a randomized complete block design. Caged fi...

Fingerlings of channel catfish Ictalurus punctatus exhibited a significant exposure-dependent decrease in growth (measured by weight gain and increase in total length) and condition factor after 9 weeks of exposure to environmental ammonia. Concentrations of 5-hydroxytryptamine (5-HT) and dopamine in the brain decreased significantly whereas the ratio of 5-hydroxyindoleacetic acid (5-HIAA) to 5-HT increased significantly in exposure-dependent manners. The brain dopamine concentrations and the 5-HIAA : 5-HT ratio collectively explained 88% of the variation in growth due to ammonia exposure. This study demonstrates the potential to predict ammonia-induced inhibition of growth in channel catfish with physiological changes.

Advancing the production efficiency and profitability of aquaculture is dependent upon the ability to utilize a diverse array of genetic resources. The ultimate goals of aquaculture genomics, genetics and breeding research are to enhance aquaculture production efficiency, sustainability, product quality, and profitability in support of the commercial sector and for the benefit of consumers. In order to achieve these goals, it is important to understand the genomic structure and organization of aquaculture species, and their genomic and phenomic variations, as well as the genetic basis of traits and their interrelationships. In addition, it is also important to understand the mechanisms of regulation and evolutionary conservation at the levels of genome, transcriptome, proteome, epigenome, and systems biology. With genomic information and information between the genomes and phenomes, technologies for marker/causal mutation-assisted selection, genome selection, and genome editing can be developed for applications in aquaculture. A set of genomic tools and resources must be made available including reference genome sequences and their annotations (including coding and non-coding regulatory elements), genome-wide polymorphic markers, efficient genotyping platforms, high-density and high-resolution linkage maps, and transcriptome resources including non-coding transcripts. Genomic and genetic control of important performance and production traits, such as disease resistance, feed conversion efficiency, growth rate, processing yield, behaviour, reproductive characteristics, and tolerance to environmental stressors like low dissolved oxygen, high or low water temperature and salinity, must be understood. QTL need to be identified, validated across strains, lines and populations, and their mechanisms of control understood. Causal gene(s) need to be identified. Genetic and epigenetic regulation of important aquaculture traits need to be determined, and technologies for marker-assisted selection, causal gene/mutation-assisted selection, genome selection, and genome editing using CRISPR and other technologies must be developed, demonstrated with applicability, and application to aquaculture industries.Major progress has been made in aquaculture genomics for dozens of fish and shellfish species including the development of genetic linkage maps, physical maps, microarrays, single nucleotide polymorphism (SNP) arrays, transcriptome databases and various stages of genome reference sequences. This paper provides a general review of the current status, challenges and future research needs of aquaculture genomics, genetics, and breeding, with a focus on major aquaculture species in the United States: catfish, rainbow trout, Atlantic salmon, tilapia, striped bass, oysters, and shrimp. While the overall research priorities and the practical goals are similar across various aquaculture species, the current status in each species should dictate the next priority areas within the species. This paper is an output of the USDA Workshop for Aquaculture Genomics, Genetics, and Breeding held in late March 2016 in Auburn, Alabama, with participants from all parts of the United States.

The continued expansion of intensive aquaculture activities requires that substitutes for fish meal-based protein be identified. In this study, we evaluated partial (50 and 75%) replacement of fish meal in red drum, Sciaenops ocellatus, diets with soy protein concentrate (S) and barley protein concentrate (B). Growth, feed efficiency, survival, tolerance to low temperature, and tolerance to handling in warm, hypersaline water were evaluated. Only the diet with a 50% replacement of fish meal with S yielded results comparable to fish fed a nonsubstituted fish meal diet. However, the low-temperature studies were complicated by differences in mean fish weight among the groups. The results of this study indicate S may be partially substituted for fish meal in red drum diets.

Fingerling Guadalupe Bass Micropterus treculii were cultured in 18, 21, 24, 27, or 30°C water for 6 weeks. Temperature affected the growth of the Guadalupe Bass when it was measured by increases in TL but not when measured by increase in mass. The optimal temperature for growth of Guadalupe Bass was 27–28°C. Condition factor increased linearly with temperature, indicating that the fish were plumper at warmer temperatures. The mean hematocrit was 37 and not significantly affected by temperature, although a trend of increasing hematocrit with increasing temperature was apparent. The liver index varied significantly with temperature, and the maximum index was at 24°C. The results of this study provide basic thermal information and some base line hematological values for hatchery production and management of Guadalupe Bass. Received September 24, 2012; accepted March 9, 2013

The objective of our study was to determine the acute toxicity of 3 common aquatic nitrogenous toxicants to the federally endangered Barton Springs salamander (Eurycea sosorum). Based on our findings, the 96-h median lethal concentrations (96-h LC50) for un-ionized ammonia-N, nitrite-N, and nitrate-N to E. sosorum are 2.0 ± 0.32, 31.7 ± 4.02, and 968.5 ± 150.6 mg/L, respectively. These results establish a benchmark for the tolerance of plethodontid salamanders to these toxicants and indicate that current water quality criteria are adequate for their protection. Environ Toxicol Chem 2017;36:3003-3007. © 2017 SETAC.

Striped bass hybrids (Morone chrysops female x Morone saxatilis male) confined in a net for 10 minutes had significantly elevated corticosteroid levels (24.2 † 5.4 μg/100 ml) and significant hyperchloremia (150.02 † 2.7 meq/liter), in comparison with baseline levels of 0.8 † 0.1 μg/100 ml and 132.6 † 1.5 meq/liter, respectively. Hauling hybrids for 2 hours in freshwater significantly elevated corticosteroid levels (12.2 † 1.2 μg/100 ml) and reduced chloride levels (119.8 † 1.4 meq/liter). Corticosteroid levels remained high and hypochloremia developed within 24 hours after both netting and hauling. Although netting and hauling in 25 mg/liter MS-2223 or 10 g/liter NaC1 prevented chloride depletion during the stress, hypochloremia developed within 72 hours after the fish were transferred to freshwater. The development of hypochloremia several hours after handling indicates that hybrid bass that survive the initial stress do not necessarily recover, but may die in the days following handling. Fish anesthetized in 50 mg/liter MS-222 for 15 minutes prior to handling followed by hauling in water containing a combination of 25 mg/liter MS-222 and 10 g/liter NaCl did not develop hypochloremia within 72 hours after hauling; plasma corticosteroids were elevated during transport, but returned to nearly normal levels within 24 hours. This combination of 25 mg/liter MS-222 and 10 g/liter salt was the most successful handling medium tested.

Interest in culturing the Pacific white shrimp Litopenaeus vannamei in low-salinity and brackish-well waters has led to questions about the ability of this species to osmo- and ionoregulate in environments containing low concentrations of ions and in environments with ionic ratios that differ from those found in sea water. After seven days, hemolymph osmolality and potassium, sodium and calcium values were all significantly affected by salinity (as artificial sea salt) with values decreasing with decreasing salinity. These decreases were small, however, relative to decreases in salinity, indicating iono- and osmoregulation with adjustment for gradients. The hemolymph osmolality and sodium and calcium concentrations in shrimp exposed to either 2 g/L artificial sea salt or 2 g/L mixed-ion solution (a mixture of sodium, potassium, calcium, and magnesium chlorides that approximate the concentrations and ratios of these cations found in 2 g/L dilute seawater) did not differ significantly. However, hemolymph potassium levels were significantly lower in shrimp held in the mixed-ion environment. Potassium influx rates were similar in shrimp held in either artificial sea salt or mixed ions. The results of this study indicate that salinity affects hemolymph-cation concentrations and osmolality. Further, differential potassium-influx rates do not appear to be the basis for low hemolymph potassium levels observed in shrimp held in mixed-ion environments.

Black sea bass Centropristis striata juveniles survived abrupt transfer from 15 g/L salinity to 8 g/L, but not to 6 g/L salinity. Seven days after abrupt transfer, the plasma osmolality was proportional to environmental osmolality. Increasing environmental calcium concentration in receiving environments did not have an effect on either survival or plasma osmolality after abrupt transfer. Abrupt transfer from 15 g/L salinity to 4.5 g/L artificial sea salt + 4.5 g/L calcium chloride resulted in 100% mortality. Abrupt transfer of black sea bass to salinities below ∼ 15 g/L will have osmotic and perhaps survival consequences.

Strict environmental regulations and the high cost of land limit the growth of coastal aquaculture in developed countries. Finding ways to successfully culture marine species in inland systems may prove to be more economically viable. An important step in developing inland culture of marine species is to identify minimal environmental ion concentrations and ratios required for economical growth. Recent research has examined the potential for Pacific white shrimp, Litopenaeus vannamei, to be cultured in low-salinity environments (Laramore et al. 2001; McGraw et al. 2002; Atwood et al. 2003; Saoud et al. 2003). However, little research (Atwood et al. 2003; McNevin et al. 2004) has been conducted to assess shrimp survival in environments that are not dilute seawater. This experiment is based on previous work performed in our laboratory that has shown that L. vannamei exhibits no differences in growth or survival when grown in 2 and 20 g/L sea salt and that a 2 g/L mixed-salt environment (the term mixed salts is used here to refer to the chlorides of sodium, calcium, potassium, and magnesium) does not support growth and survival as well as an equal concentration of sea salt (Sowers et al. 2005). Our objective in this experiment was to determine if L. vannamei grow as well in 1 g/L dilute seawater plus 1 g/ L mixed salts as it would in 2 g/L dilute seawater. Equivalent growth would allow for the partial substitution of less expensive mixed salts for sea salt, reducing the need for sea salt in inland culture systems. Materials and Methods

Mortality and physiological responses of adult striped bass Morone saxatilis angled from Lake Murray, South Carolina, and held in live-release tubes were evaluated during the spring and summer of 2003. To estimate mortality, we attached external ultrasonic transmitters to 59 striped bass (mean total length (TL) = 585 mm). Striped bass were caught with angling gear, tagged, and immediately released or held in live-release tubes for 2, 4, or 6 h prior to release. No mortality of striped bass was observed during spring. Overall mortality during summer was 83%. Mortality of summer-caught striped bass was not related to tube residence time, fish TL, depth of capture, or surface water temperature. To characterize physiological stress, we measured the plasma cortisol, glucose, lactate, and osmolality levels of 62 additional striped bass (mean TL = 563 mm) that were angled and immediately released or angled and held in live-release tubes. Plasma cortisol, glucose, lactate, and osmolality were positively ...

Mechanisms of copper toxicity and consequences of exposure vary due to uptake route and ionoregulatory status. The goal of this research was to develop a model fish system to assess the influence of different Cu exposure routes (waterborne or dietary) on bioavailability, uptake, and effects in hybrid striped bass (Morone chrysops x Morone saxatilis) acclimated to fresh- or saltwater. Initially, hybrid striped bass were exposed to dietary Cu concentrations of 571, 785, and 1013 mug Cu/g, along with a control (approximately 5 microg Cu/g), for 14 days in saltwater. Intestinal and liver Cu accumulated in a dose-dependent manner in fish exposed to increasing levels of dietary Cu. Chronic (42 days) experiments were then conducted to determine sub-lethal effects of aqueous, dietary, and combined aqueous and dietary Cu exposures to both freshwater- and saltwater-acclimated hybrid striped bass. Growth and Cu accumulation in the gill, intestine, and liver were measured. Although no significant effects were observed in fish exposed to waterborne Cu, those exposed through the diet accumulated significant liver and intestinal Cu but showed no significant change in growth. Overall, these results suggest that at the levels tested, exposure to elevated waterborne Cu did not cause significant long-term tissue Cu accumulation, whereas dietary Cu exposure caused significant liver and intestinal Cu accumulation in hybrid striped bass which was comparable in both freshwater and saltwater (15 g/L).

The uptake, depuration and toxicity of environmental nitrite was characterized in Litopenaeus vannamei exposed in water containing low concentrations of artificial sea salt or mixed salts. In 2 g/L artificial sea salts, nitrite was concentrated in the hemolymph in a dose-dependent and rapid manner (steady-state in about 2 d). When exposed to nitrite in 2 g/L artificial sea salts for 4 d and then moved to a similar environment without added nitrite, complete depuration occurred within a day. Increasing salinity up to 10 g/L decreased uptake of environmental nitrite. Nitrite uptake in environments containing 2 g/L mixed salts (combination of sodium, potassium, calcium and magnesium chlorides) was similar to or lower than rates in 2 g/L artificial sea salt. Toxicity was inversely related to total dissolved salt and chloride concentrations and was highest in 2 g/L artificial sea salt (96-h medial lethal concentration = 8.4 mg/L nitrite-N). Animals that molted during the experiments did not appear to be more susceptible to nitrite than animals that did not molt. The shallow slope of the curve describing the relationship between toxicity and salinity suggests that management of nitrite toxicity in low-salinity shrimp ponds by addition of more salts may not be practical.

Uptake of environmental NO2- by most freshwater fishes occurs at the gills where NO2- is actively transported into the blood by the Cl- uptake pathway. Some freshwater fishes do not concentrate NO2- in their plasma, regardless of environmental NO2- exposure and exhibit a high degree of resistance to NO2-. Recent studies indicate that freshwater-adapted killifish (Fundulidae: Fundulus heteroclitus) and European eel (Anguillidae: Anguilla anguilla) have no or minimal Cl- uptake activity at the gills relative to most freshwater fishes; rather, Cl- requirements are met in other ways (probably dietary). We hypothesized that different rates of Cl- uptake by the gill may explain the observed differences in NO2- uptake and consequent toxicity among freshwater fishes. Cl- influx rates of channel catfish (Ictaluridae: Ictalurus punctatus), a species that concentrates NO2- in the plasma and is sensitive to NO2-, and bluegill (Centrarchidae: Lepomis macrochirus), a species that does not concentrate NO2- in the plasma and is resistant to NO2-, were determined over a range of environmental Cl- concentrations. Channel catfish actively transported chloride into the plasma (Km = 155.6+/-101.2 micromol/L Cl-; Jmax = 414.9+/-51.4 nmol/g/h; +/-SEM). In contrast, bluegill exhibited no observable Cl- uptake. We placed our results and previously reported results in a phylogenetic context and concluded that differences in Cl- uptake mechanisms among groups of freshwater fishes may explain, in large part, the wide range of sensitivity to environmental NO2-. NO2- uptake determinations may also prove to be an easy screening method when studying the phylogenetic distribution and nature of Cl- uptake mechanisms in the gills of fishes.

Ecophys.Fish is a deterministic STELLA® model for simulating rates of fish growth in environmental regimes that have simultaneous temporal variation in food, oxygen, temperature, pH, and salinity. The purpose of this article is to introduce Ecophys.Fish to those who might want to use it as a framework or starting point for applications of their own. We believe our model, although focused in autecology, will prove useful at organizational levels both below and above the individual fish. Ecophys.Fish is a quantitatively explicit interpretation of concepts originally formalized by F.E.J. Fry, almost 60 years ago. Fry's “physiological classification of environment” and his concept of “metabolic scope for activity” were coupled with conventional bioenergetics to provide the model's theoretical basis. The model's inputs are initial size of fish, and time series of temperature, pH, dissolved-oxygen concentration (DO), salinity, and food availability and its energy content. Outputs are food consumption, oxygen co...

Resistance of juvenile cobia, Rachycentron canadum, to low salinity, low temperature and high nitrite concentrations was examined under laboratory conditions. After acclimating juveniles to a salinity of 20 g/L (27.3°C), salinity was decreased by 2 g/L/day. The first fish died at a salinity of 8 g/L and 80% offish were dead within 24 hours of exposure to 2 g/L. Acclimation offish to 22.6°C (21 g/L salinity) followed by a temperature reduction of 0.53°C/day resulted in initial mortality at 12.9°C. The median-lethal temperature was 12.1°C and all fish were dead by the time the temperature reached 10.4°C. Fish exposed for 96 hours to nominal ⁁ 32 mg/L nitrite-N survived. Results of this study indicate that cobia juveniles require a salinity and temperature of > 8.0 g/L and > 12.9°C, respectively, and that environmental nitrite should not be deleterious at concentrations normally found in aquaculture systems.

Recent interest in the culture of black sea bass, Centropristis striata, has led to questions regarding the environmental requirements of this species for economically-viable production. Here, we present the results of short-term laboratory studies on ammonia toxicity, nitrite toxicity and oxygen consumption rates. Fifty percent of the juveniles died when exposed to 0.7-0.8 mg/L un-ionized ammonia-N for 24 hours (25°C, 23 g/L salinity). All exposed fish survived exposure to ≤ 0.6 mg/L un-ionized ammonia-N for 10 days. Black sea bass juveniles survived 24-hours exposure to 250 mg/L nitrite-N when exposed in 12 or 20 g/L salinity. Fish exposed for 24 hours to nitrite in 35 g/L salinity died when exposed to 250 mg/L nitrite-N, but survived exposure to 100 g/L nitrite-N. All fish exposed to 50 mg/L nitrite-N for 10 days survived (salinities of 12, 20 and 35 g/L). Mean oxygen consumption rate was 0.09 mg/hour/g (25°C). Fish weight significantly affected oxygen consumption rate with larger fish consumi...

Aquaculture for the purpose of supplementing natural recruitment is one approach used to assist the recovery of endangered fish populations. A common consequence of high-density culture is the accumulation of nitrite in the water. Razorback suckers (Catastomidae; Xyrauchen texanus) survived a 72-hour exposure to 25 mg/L nitrite-N. Bonytails (Cyprinidae; Gila elegans) died within 48 hours of exposure to 10 mg/L and 25 mg/L nitrite-N. A chloride:nitrite ratio of 5 (as either calcium chloride or sodium chloride) protected bonytail from nitrite toxicity. This study provides some basic knowledge that can be applied to the culture of these two endangered species and raises some interesting questions about the nature of nitrite toxicity and inhibition of toxicity in these two species.

This study was conducted (1) to evaluate the effects of photoperiod (fixed vs. decreasing light), fish size (136 vs. 220 mm), dissolved ions (hardness and salinity) and diet (menhaden oil vs. coconut oil-based) on the tolerance (survival) of Nile tilapia, Oreochromis niloticus, to low temperatures (decreased by approximately 0.5 °C per day) and (2) to evaluate the effect of dietary fatty acid composition on selected physiological characteristics of Nile tilapia exposed to decreasing temperatures. Size significantly affected mortality, with smaller fish being less tolerant to low temperatures than larger fish. Results were equivocal in the photoperiod, dissolved ion and dietary lipid experiments, and were dependent on the method of data analysis employed. Diet significantly affected plasma osmolarity, with higher values in fish fed the menhaden-based diet. Haematocrit, serum glucose, sodium and cortisol concentrations, serum and splenic lysozyme activities, lymphocyte count and hepatosomatic index were not affected by diet. Haematocrit, white cell count and serum glucose and sodium concentrations were significantly affected by temperature, but serum and splenic lysozyme content, hepatosomatic index, and serum cortisol concentrations were not. The results of this series of experiments indicate that altering the environment or diet has little effect on the ability of Nile tilapia to survive low temperatures.

The salinity and temperature tolerances of black sea bass Centropristis striata juveniles (46 ± 10.3 mm total length [mean ± SD]) were estimated to assist in decisions concerning location of culture facilities and types of production systems. At 21°C, all exposed fish survived for 7 d in salt concentrations of 10, 20, or 35 g/L. All fish exposed to salt concentrations of 5 g/L died within 3 d. Temperature extremes were estimated after acclimation of fish to 24–25°C. Half of the juveniles exposed to a gradual increase (+0.65°C/d) or decrease (–0.51°C/d) in temperature (at a nominal salt concentration of 20 g/L) were dead when the water temperature reached 33.3°C and 3.7°C, respectively. Results of this study indicate that this species requires saline water at or above a salt concentration of 10 g/L and that it may not be practical to keep black sea bass over winter or over summer in shore-based outdoor facilities located in temperate climates.

Northern-stock black sea bass Centropristis striata demonstrated upper and lower median lethal temperatures of 33.6°C and 2.7°C, respectively, when temperatures were increased or decreased at a rate of approximately 0.5°C per day. The temperature for optimal growth was 25.6°C. This work, along with information in the literature, indicates that thermal tolerances and preferences do not differ greatly between the northern and southern stocks of black sea bass.

Red drum, Sciaenops ocellatus fingerlings cultured in recirculating systems for 56 days at 18, 22, 26, 30, or 34° C in salinities of 5 and 10 ppt exhibited best growth at 30.4 °C in 5 ppt and 31.1 °C in 10 ppt. Growth ranged from 7 to 125%. Survival and condition factor were not affected by temperature. The results of this study indicate that optimization of temperature in red drum culture systems will have profound effects on productivity.

Fingerlings of channel catfish Ictalurus punctatus exhibited a significant exposure-dependent decrease in growth (measured by weight gain and increase in total length) and condition factor after 9 weeks of exposure to environmental ammonia. Concentrations of 5-hydroxytryptamine (5-HT) and dopamine in the brain decreased significantly whereas the ratio of 5-hydroxyindoleacetic acid (5-HIAA) to 5-HT increased significantly in exposure-dependent manners. The brain dopamine concentrations and the 5-HIAA : 5-HT ratio collectively explained 88% of the variation in growth due to ammonia exposure. This study demonstrates the potential to predict ammonia-induced inhibition of growth in channel catfish with physiological changes.

— Two studies were conducted to examine the influence of salinity on low-temperature tolerance of southern flounder Paralichthys lethostigma. Juveniles (3.4 g ± 1.2 g in study one; 32.8 g ± 34.8 g in study two) were acclimated to 20 C at salinities of 1, S, 10, 20 and 30%o in study one and 1, 10 and 30%o in study two. Temperature was then decreased approximately 1 C per day to a nominal 4 C and 2 C, in studies one and two. respectively. Fish were subjected to the low temperatures for 10 d and then returned to the initial temperature (20 C) at a rate of approximately 1 C per day. Mortality ranged from 0 to 10% in study one and from 30 to 100% in study two and was significantly affected by salinity. Results of this research suggest that the chronic low-level tolerance limit is between 2 and 4 C and that increased salinity offers some mitigating effect.

The 96-h median-lethal concentration (96h LC50) of total ammonia nitrogen (ammonia-N) to fingerling shortnose sturgeon Acipenser brevirostrum was 149.8 ± 55.20 mg/L (mean ± SD, 17.9 ± 0.62°C, pH = 6.8–7.3). Calculated 96-h LC50 for un-ionized ammonia-N was 0.58 ± 0.213 mg/L. The 96-h LC50 of nitrite nitrogen to shortnose sturgeon fingerlings was 11.3 ± 8.17 mg/L (17.9 ± 0.31°C

We conducted a large-scale mark–recapture study to estimate the population size of blueback herring Alosa aestivalis in the J. Strom Thurmond Reservoir, a 28,329-ha reservoir on the Savannah River. The reservoir was divided into four strata, and 100,619 blueback herring (140 ± 5.0 mm TL; mean ± SD) were tagged and released between April 26 and May 24, 1996. Blueback herring were tagged with 1-mm sequentially coded wire tags injected into the nasal cartilage. In a controlled field study conducted concurrent to tagging, we estimated a combined survival and tag retention rate of 90% and used this estimate to adjust the number of marked fish. In all, 155 tags were recovered from 144,227 fish examined from May 29 to August 14. Chi-square analysis indicated that recaptured fish from the lower stratum of the reservoir were not represented in proportion to tagging effort. A stratified approach was taken in an effort to eliminate bias due to incomplete mixing. When we disregarded fish marked in the lower ...

Striped bass Morone saxatilis (initial total length 38.7 ± 1.31 cm, mean ± SD) were either fed or not for two summer months in warmwater ponds (23–30°C). At the beginning, middle, and end of the study, fish from each group were captured with hook and line. Half the fish from each feeding treatment were landed as quickly as possible (20 ± 7.7 s) and half were played for 180 ± 7.5 s. Immediately after landing, fish were weighed, measured and bled. Fed fish maintained their absolute and relative weight during the study while unfed fish did not. Plasma glucose concentrations increased in both fed and unfed fish with long play. On average, glucose concentrations in both short- and long-play groups were higher in fed fish. Plasma lactate concentrations were higher in fed fish played for 180 s than in the unfed fish played 180 s. Plasma osmolalities were higher in fish played 180 s than in fish played 20 s, and were similar between fed and unfed fish. The results of this study indicate that the growth a...

Feed consumption by white river crayfish Procambarus acutus in a 56-d laboratory study increased at a linear rate with water temperature over a range of 5 to 25 C. Feed consumption changed as water temperatures were cycled from 20-8-20 C (0.5 C/d) over a 68-d period and was the highest at the initial 20 C level and the lowest at 8 C. As water temperature increased, feed consumption rate increased; however, consumption never reached the initial rate at 20 C. Crayfish fed 3% and 6% of body weight were significantly larger than animals fed at 1% of body weight after 8 wk. Feed conversion ratios increased significantly with feeding rate. Based on this laboratory study, white river crayfish feed most effectively when water temperature is 2 15 C and the feeding rate is 3% of body weight/d. Aquaculture research with crayfish in the United States has focused on the red swamp crayfish Procambarus clarkii because of its successful culture in Louisiana and other areas of the southeastern USA (Huner 1994). As crayfish aquaculture has expand- ed to the temperate regions of the United States, interest in the culture of other spe- cies, better suited to lower temperatures, has increased. The white river crayfish P.

The 96-h median lethal concentration of un-ionized ammonia-nitrogen for fingerling white bass Morone chrysops (mean weight ± SD, 4.4 ± 1.42 g) at 19.7 ± 0.4°C was 0.63 ± 0.17 mg/L in soft (≤5.0 mg calcium/L) freshwater. The uptake of ammonia by fingerling white bass (mean weight, 14.0 ± 2.74 g) was similar in soft freshwater, hard (78.3 ± 3.80 mg calcium/L) freshwater, and dilute (7.4 ± 0.30 g sea salt/L) seawater. However, exposure time did affect the concentration of plasma ammonia in exposed white bass. Based on the observations in this study and others, it is estimated that growth of fingerling white bass should not be inhibited if fish are continuously exposed to un-ionized ammonia nitrogen at 0.06 mg/L or less.

A pilot study was conducted to determine the acute resistance of Gila trout Oncorhynchus gilae to ammonia (NH3) and nitrite (NO− 2). All fish survived exposure to up to 4.5 mg/L total NH3-N (0.36 mg/L un-ionized NH3-N; pH 8.5, 15°C) for 96 h. The 96-h median lethal concentration was 5.86 mg/L total NH3-N (0.47 mg/L un-ionized NH3-N). Gila trout exposed to nitrite for 96 h died when exposed to 10 mg/L or more NO− 2-N and 3 mg/L environmental chloride. Increasing the environmental chloride concentration increased survival.

The effects of environmental calcium (5, 10, 20, 40, and 80 mg/L) on production and selected blood characteristics of sunshine bass (female white bass Morone chrysops × male striped bass M. saxatilis) under normal culture conditions were investigated in two 6-week trials. Environmental calcium had no significant effects on growth, food conversion, condition factor, hematocrit, plasma osmolality, or plasma calcium concentrations. Previous studies have indicated that environmental calcium is advantageous under stressful conditions; however, this study indicated that elevated calcium levels offer no advantages during apparently nonstressful periods.

Channel catfish Ictalurus punctatus were stressed by net confinement for 0–12 h, and the percentages of apoptotic peripheral leukocytes were determined. The frequency of apoptosis was lower in stressed animals than in nonstressed controls, and the degree of reduction was dependent on the duration of stress. Leukocytes isolated from control fish were incubated in autologous plasma or plasma from stressed fish. The cells cultured in plasma from stressed fish showed decreased apoptosis, indicating a direct effect of stress on the individual cells rather than redistribution or cell lysis. Hydrocortisone (0.l mg/mL) had no effect in vitro on apoptosis in leukocytes. The mechanism, as well as the significance, of stress-induced changes in apoptosis in circulating leukocyte populations remains to be explained.

Fingerling channel catfish Ictalurus punctatus were fed purified diets either unsupplemented and deficient in both selenium and vitamin E, deficient in either selenium or vitamin E, adequate in both selenium (0.2 mg/kg) and vitamin E (60 mg/kg), or excessive in both nutrients (four times the recommended levels). After 115–120 d of feeding the experimental diets, the red blood cell membranes offish fed diets deficient in vitamin E were more susceptible to peroxidation than were those of fish fed diets that met or exceeded vitamin E recommendations. Hepatic, selenium-dependent glutathione peroxidase activity was suppressed in fish fed diets deficient in selenium when compared with this enzyme activity in fish fed diets containing recommended or higher levels of selenium. Intracellular superoxide anion production of macrophages was higher in fish fed the diet fortified with four times the recommended levels of both nutrients than in fish fed the other diets. None of the results indicated that seleni...

Three-month-old fingerling channel catfish Ictalurus punctatus were fed purified diets supplemented with ∝-tocopherol acetate to provide 0, 60, and 2,500 mg vitamin E/kg for 180 d. A 30-s immersion bath and an oral booster were used to deliver a bacterin of formalin-killed Edwardsiella ictaluri to half of the fish from each dietary treatment. Resistance of red blood cells to peroxidation was used as an index of antioxidant status. The susceptibility of red blood cells to oxidative hemolysis decreased with increasing levels of dietary vitamin E. Vaccinated and nonvaccinated fish were evaluated for agglutinating antibody titers and macrophage activity. Humoral antibody titers in response to E. ictaluri were significantly (P ≤ 0.05) higher in vaccinated fish than in nonvaccinated fish; however, no such differences in agglutinating antibody titers were detected among any of the dietary treatment groups. Both vaccination and vitamin E significantly enhanced the ability of macrophages to phagocytize vi...

The effects of environmental calcium and salinity on toxicities of ammonia and nitrite for sunshine bass (female Morone chrysops × male M. saxatilis) were investigated, and the effects of pH, sodium chloride, and calcium chloride on uptake and depuration of ammonia and nitrite were characterized. The concentration of un-ionized ammonia-nitrogen (UIA-N) lethal to 50% of the fish within 96 h (96-h LC50) ranged from 0.32 to 0.60 mg/L and increased significantly with increased concentration of environmental calcium over the range tested (5–80 mg/L). The acute toxicity of UIA-N was not affected by salinity over the range tested (1–24 g/L), and the 96-h LC50 was 0.70 ± 0.04 mg UIA-N/L (mean ± SE) over all salinities tested. The rate and degree of ammonia uptake was greater at elevated environmental pH. Environmental pH did not affect the rate of depuration of ammonia. Environmental calcium did not affect nitrite toxicity, and the 96-h LC50 of nitrite-nitrogen (nitrite-N) was 12.8 ± 1.6 mg/L (mean ± SE)...

Small (4.4 ± 1.50 g; mean ± SD) Nile tilapias Oreochromis niloticus were more tolerant of nitrite than large (90.7 ± 16.43 g) fish. The 96-h median lethal concentration of nitrite-N to small fish was 81 mg/L (95% confidence interval = 35–127 mg/L) compared with 8 mg/L (4–11 mg/L) for large fish. Addition of chloride to test water (as either calcium chloride or sodium chloride) protected both small and large fish from nitrite. Sodium chloride and calcium chloride appeared to be similarly effective in inhibiting nitrite toxicity.

Copper sheeting is a common roofing material used in many parts of the world. However, copper dissolved from roof sheeting represents a source of copper ions to watersheds. Researchers have studied and recently developed a simple and efficient model to predict copper runoff rates. Important input parameters include precipitation amount, rain pH, and roof angle. We hypothesized that the length of a roof also positively correlates with copper concentration (thus, runoff rates) on the basis that runoff concentrations should positively correlate with contact time between acidic rain and the copper sheet. In this study, a novel system was designed to test and model the effects of roof length (length of roof from crown to the drip edge) on runoff copper concentrations relative to rain pH and roof angle. The system consisted of a flat-bottom copper trough mounted on an apparatus that allowed run length and slope to be varied. Water of known chemistry was trickled down the trough at a constant rate and sampled at the bottom. Consistent with other studies, as pH of the synthetic rainwater decreased, runoff copper concentrations increased. At all pH values tested, these results indicated that run length was more important in explaining variability in copper concentrations than was the roof slope. The regression equation with log-transformed data (R(2) = 0.873) accounted for slightly more variability than the equation with untransformed data (R(2) = 0.834). In log-transformed data, roof angle was not significant in predicting copper concentrations.

Stress induced by severe confinement in cages and by simulated transport was evaluated in reciprocal white bass × striped bass hybrids (Morone chrysops × M. saratilis) after acclimation to various calcium concentrations in freshwater (5, 10, 20, 40, and 80 mg/L calcium) and various salinities (1, 8, 16, and 24%o) at 25 C. Survival was monitored in both confinement and transport events. In confinement events, changes in plasma osmolality were used as an indicator of osmoreg-ulatory dysfunction. After 6 h of severe confinement in cages, survival was significantly affected by treatments in both freshwater (FW) and saltwater (SW) events. Survival was greatest in 80 mg/L calcium in FW treatments and 8%o in the SW treatments. Simultaneous analysis of both FW and SW confinement data revealed that, after compensating for fish weight, survival increased as environmental ionic content increased (up to 8%o) then decreased with increasing salinity. Plasma osmolality decreased significantly from baseline levels with respect to confinement time in all FW treatments. Significant differences in plasma osmolality were observed among SW treatments: plasma osmolality of fish confined in 1%o decreased while those confined in salinities of 16 and 24%o increased. The plasma osmolality offish confined in 8%o remained near baseline levels. Almost no mortality (

Channel catfish (lctalurus punctatus) fingerlings stocked at a rate of 450 fish/0.04 ha pond were simultaneously cultured with fingerlings stocked in 1.25 m3 cages (0, 250, 350, or 450 fishlcage; one cage/pond). The fish in the cages were cultured and harvested for a 90–330 g (whole fish) market. The fish in the open ponds were cultured and harvested for a 490–1,140 g market. Harvest weights of open pond fish in all treatments were similar indicating that the presence of the caged fish and the associated higher daily pond feeding rates did not affect open pond production. Ninety-five to 99% of the caged fish and 96 to 98% of the open pond fish were of marketable size at harvest. Survival and food conversion ratios were similar among treatments. Results of this study indicate that total pond production can be increased (in this case up to 19%) by using a combination of open pond and cage techniques and by simultaneously producing fish for two markets.

Production characteristics of pan-size (approximately 227 g) channel catfish (Ictalurus puncturus) were determined in cages and open ponds stocked with fingerlings to densities of 20,000 and 12,500 fish/ha. After 145 days, mean fish weight in all treatments exceeded 227 g. Mean survival was similar in all treatments. Food conversion ratios were significantly better in ponds than in cages but density did not affect the ratios. Neither density nor production system affected production (as measured by total weight produced) when initial density differences were considered (analysis of covariance). Variability in total length at harvest was similar between production systems; however, low density treatments were less variable than high density treatments. Results of this study indicate that pan-size channel catfish can be cultured efficiently at stocking densities well above the 12,500 fish/ha (5,000 fishlacre) generally used when culturing fish to larger sizes.

Fingerling red drums (Sciaenops ocellatus; mean weight ± SE, 28.0 ± 0.9 g to 42.3 ± 1.1 g) were acclimated to salinities of 2, 4, 8, 16, or 35‰ (25°C) and then crowded in cages for up to 48 h. Fish in the intermediate salinities survived whereas most fish in the two extreme salinities died. Plasma osmolality values increased in fish confined in 35‰ salinity, decreased in fish confined in 2‰ water, and were stable in the fish confined in the intermediate salinities. All fish (weight, 20.2 ± 1.2 g to 37.1 ± 1.7 g) survived 9 h of simulated transport and a 3-d followup in 2, 4, 8, 16, or 35‰ salinity at temperatures of 25 or 30°C. Results of this study and others indicate that healthy red drum fingerlings tolerate confinement and transport well. Further, survival is enhanced if fish are handled and transported in water that is nearly isosmotic with the plasma of the fish (approximately 11‰).