Heritability of juvenile growth traits in red drum (Sciaenops ocellatus L.)

Heritability of juvenile growth rate was estimated for red drum (Sciaenops ocellatus), an economically important sciaenid fish in the southern USA. Thirty‐eight families were generated via ‘natural’ spawning of multiple sets of five breeders (three dams × two sires) in individual brood tanks. Offspring were individually tagged with Passive Integrated Transponder (PIT) tags and mixed for grow‐out in replicate ‘common‐garden’ tanks. Juvenile growth was followed from 166.4±18.6 to 254.0±27.0 mm (total length). Offspring were assigned a posteriori to individual brood fish (dam and sire) based on genotypes at nuclear‐encoded microsatellites. Heritability (h²) of a thermal growth coefficient was estimated using an animal‐additive model and a restricted maximum‐likelihood algorithm. Estimates of h² were 0.33±0.08 and 0.31±0.08 for thermal growth coefficient based on length and weight respectively. These results indicate a significant genetic component in juvenile growth rate in red drum. Estimates of h² for condition coefficient (K) at various measurement dates averaged 0.38, suggesting a genetic component to shape in juvenile red drum.     

Physiological improvement in the copepod Eurytemora affinis through thermal and multi‐generational selection

As a major part of fish larval diet in nature, copepods constitute an appropriate live prey for aquaculture purposes. Considering the difficulty of mastering copepod mass production, studies on their growth performance at different environmental conditions are needed to improve their productivity. In this study a new selective approach based on temperature control is proposed to improve the physiological (body size, fecundity and lipid storage) performance of copepods. The estuarine copepod Eurytemora affinis known to have a high genetic variance in temperature tolerance was used as a biological model. First two different copepod lines were obtained after long‐term culture at constant cold (7°C) and warm (20°C) temperatures. Then both populations were transferred to a higher temperature of 24°C appropriate for aquaculture use and followed during five generations. During the first two generations (F1–F2) of a cold‐acclimated population, female body size and fecundity decreased significantly whereas the survival rate remained high. The high lipid content of this population was used by females to compensate the heat shock of more than 10°C. However, the survival rate decreased dramatically in F3 but allowed the selection of robust individuals which progressively improved their fitness during the following generations. So, compared to the warm acclimated population, the cold acclimated one showed larger body size, higher fecundity and better lipid storage. After only five generations at 24°C the cold‐acclimated population showed a significant genetic gain in prosome length compared to the warm acclimated one.     

Physiological responses and HSP70 mRNA expression of GIFT strain of Nile tilapia (Oreochromis niloticus) under cold stress

An investigation on the physiological responses and HSP70 expression under cold stress was conducted on Genetically Improved Farmed Tilapia (GIFT) strain of Nile tilapia (Oreochromis niloticus). Tilapia were acclimated at 28°C as control and then the water temperature was reduced from 28°C to 15°C at a rate of 1°C h^?1, and serum biochemical indices, antioxidant enzymes and expression of HSP70 mRNA were analysed on days 0, 0.5, 1, 2, 3 and 5 after exposure to 15°C. The concentration of serum K, Na, Cl and Ca concentration showed instability during cold stress. Glucose rapidly increased on day 0 followed by a declining trend. Triglyceride, cholesterol, low density lipoprotein‐cholesterol signifi‐cantly decreased and high density lipoprotein‐cholesterol showed instability during cold stress. Aspartate aminotransferase, alanine aminotransferase and lactate dehydrogenase activities were prominently elevated under cold stress. Superoxide dismutase and catalase activities showed a remarkable rise on day 0.5 under cold stress, and gradually decreased thereafter. HSP70 mRNA level significantly increased both in liver and muscle under cold stress, especially on days 0.5 and 1. These results suggest that cold influences several physiological responses of tilapia, and the cold resistance and cold tolerance of tilapia will benefit from the enhancement of antioxidant enzymes activities and upregulated HSP70 mRNA expression.     

Developmental temperature stress and parental identity shape offspring burst swimming performance in sockeye salmon (Oncorhynchus nerka)

Abstract – The persistent effects of embryonic temperature stress and individual parentage on fry swimming performance were examined in a cross‐fertilisation experiment using sockeye salmon (Oncorhynchus nerka). A fixed‐velocity test of burst swimming was used to assess the endurance capacity and behavioural performance of individual fry from 10 offspring families incubated at 12, 14 or 16 °C to hatch and then reared through yolk absorption and exogenous feeding stages in a common posthatch environment (average 6.9 °C). Fry burst swim time (BST) was influenced by an interaction between incubation temperature and family identity. Average BST was longer for fry from the 12 °C prehatch treatment compared to 14 and 16 °C, although differences were largely attributable to temperature effects on average fry size. Behavioural observations revealed that fish incubated at 16 °C performed more poorly, having a larger proportion of individuals that required stimulation to swim, fatigued more frequently or were classified as ‘nonswimmers’. Within all three incubation temperature treatments, mean BST varied significantly among offspring families, independent of fry mass and length. An interesting relationship was observed within the 16 °C treatment, whereby families with higher survivorship were characterised with lower mean BSTs. Collectively, these findings demonstrate that exposure to high temperatures in early sockeye salmon development can result in persistent, parentally mediated effects on fry performance. As such, these results provide important insight into how elevated temperature events during egg incubation may affect early life history selection processes and survival in stages beyond when the stressor is experienced.     

Determination of optimal temperature(s) in juvenile red‐spotted grouper Epinephelus akaara (Temminck & Schlegel) based on growth performance and stress responses

This study sought to determine the optimal temperature(s) for aquaculture of juvenile red‐spotted grouper Epinephelus akaara (Temminck & Schlegel) (mean initial BW: 3.1 g). Growth performance, insulin‐like growth factor 1 (IGF‐1) expression and thermal stress responses (plasma cortisol, glucose, and hepatic heat shock protein 60 expression) were evaluated at three constant temperatures (24°C, 26°C and 28°C) in a 2‐week trial. At the end of the trial, final BW was significantly higher at 26°C and 28°C than at 24°C (p < 0.05); a quadratic regression analysis of final BW showed the optimum temperature for growth was 27.5°C (p < 0.05, R² = 0.806). The highest hepatic IGF‐1 expression was observed at 26°C (p < 0.05). On the other hand, hepatic heat shock protein 60 expression was highest at 28°C (p < 0.05), suggesting thermal stress. In conclusion, temperature optima, which support excellent growth but induce minimal thermal stress, was 26°C. This fine information within a narrow temperature range is expected to give empirical information for red‐spotted grouper farmers to sustain maximal production efficiency with avoiding thermal stress and to determine the future location of production, especially in consideration of arising seawater temperatures.     

Attachment and growth of vegetative propagules of Chondria crassicaulis Harvey (Ceramiales,Rhodophyta) under various culture conditions

The red alga Chondria crassicaulis has a wide‐ranging bioactive chemical composition and is used as a local foodstuff, representing a potentially new cultivar in Korea. The cultivation techniques were developed by examining the monthly changes in frond weight in a field population of C. crassicaulis from November 2016 to October 2017. For seedling production, temperature and irradiance effects on the attachment and growth of vegetative propagules of C. crassicaulis were evaluated. In addition, effects of day length and salinity on the propagule growth were examined. C. crassicaulis is a year‐round species with a maximum frond wet weight of 817 mg observed in July 2017, as seawater temperature increases to 20°C. The attachment of vegetative propagules was significantly affected by temperature and irradiance, with maximal values detected at 20–25°C and 60 µmol photons m^?2 s^?1. The relative growth rates of vegetative propagules of C. crassicaulis were the highest at 20–25°C, 60 µmol photons m^?2 s^?1, and a salinity of 25 psu. In conclusion, due to its tremendous tolerance under variable environmental conditions, the vegetative propagules of C. crassicaulis can be used as seedlings for mass cultivation.     

Optimum temperature and food-limited growth of larval Atlantic cod (Gadus morhua) and haddock (Melanogrammus aeglefinus) on Georges Bank

We estimated recent growth of Atlantic cod (Gadus morhua) and haddock (Melanogrammus aeglefinus) larvae collected on the southern flank of Georges Bank in May 1992–94 from the ratio of RNA to DNA (R/D) and water temperature. Growth of both species increased with water temperature to about 7°C and then decreased. The highest growth rates were observed in May 1993 at water temperatures around 7°C. These data confirm an earlier observation of comparable temperature optima for growth of Atlantic cod and haddock larvae in the north‐west Atlantic. Comparisons of field growth rates and temperature optima with data for larvae cultured at high temperatures and prey densities in the laboratory suggest that growth may have been food‐limited at higher temperatures on Georges Bank. Given that 7°C is the long‐term mean water temperature on the southern flank in May and that climate models predict a possible 2–4°C rise in water temperatures for the western North Atlantic, our findings point to a possible adverse effect of global warming on Atlantic cod and haddock.     

The induction of Hsp70 synthesis by non‐lethal heat shock confers thermotolerance and resistance to lethal ammonia stress in the common carp,Cyprinus carpio (Linn)

Exposure to heat‐shock protein (Hsp) stimulating factors induces Hsp accumulation and confers tolerance to lethal ammonia stress on the common carp Cyprinus carpio. This study investigated whether a non‐lethal heat shock bestowed similar protective effects against ammonia and induced thermotolerance, both thought to be rendered by increased amounts of Hsps. The 30‐min lethal temperature (30 min LHT) and 1‐h lethal ammonia concentration (1 h LCT) for this species occurred at 41°C and 14.2 mg/L NH₃ respectively. Heating juvenile carp (5 cm) from 28°C to 32, 34 and 38°C, with a subsequent 8‐h recovery period augmented tolerance to lethal heat and ammonia perturbation by two to threefold as compared with animals held at 28°C. Protection occurred in conjunction with Hsp70 accumulation in gills, substantiating the role of this Hsp in enhancing the stress tolerance of common carp.     

Effects of temperature on growth of juvenile blackfoot abalone, Haliotis iris Gmelin

The effects of temperature on growth and survival of juvenile blackfoot abalone, Haliotis iris, were investigated. Animals of 10, 30 or 60 mm initial shell length were exposed to ambient (6–10°C), 14, 18, 22 and 26°C for 112 days in a flow‐through culture system. Maximum growth occurred at 22°C for the 10 and 30 mm size classes and at 18°C for the 60 mm size class. Regression analysis identified the optimal temperature for growth (T_optG) at around 21°C for the 10 and 30 mm size classes and at 17–18°C for the largest size class. In a second experiment, the critical thermal maximum of H. iris was determined as a measure of thermal tolerance. Abalone were subjected to increasing water temperatures at a rate of 2°C h^?1 until they detached from the substrate. Abalone of 10 mm displayed greater thermal tolerance than abalone of 30 and 60 mm in length. CT₅₀ temperatures were 28.8, 27.7 and 27.8°C, yielding deduced T_optG values of 19.7, 18.3 and 18.4°C for the 10, 30 and 60 mm size classes respectively. The size‐dependent nature of the relationship between growth and temperature could be capitalized upon in recirculating aquaculture systems.     

Effects of chronic upper temperature regimes on growth of two geographical strains of channel and hybrid catfish

Climate change is a growing concern for pond culture of catfish, due to possible exacerbation of temperature fluctuations and increased maximum daily temperatures. Because channel catfish (Ictalurus punctatus) have a broad natural distribution from Canada to Mexico, it was hypothesized that natural differences in thermal tolerance and seasonal growth may be attributed to different geographical strains. Furthermore, it was hypothesized that these differences would be observed in hybrid catfish (I. punctatus x [blue catfish] I. furcatus). Chronic thermal tolerance and growth rate were quantified in two geographically distinct strains of channel catfish and a corresponding hybrid catfish from one of these strains with a cross to an industry standard blue catfish strain. In a 6‐week growth experiment, catfish were subjected to daily cycling temperatures of either 27–31°C or 32–36°C, mimicking pond fluctuations. Hybrid catfish had the highest survival at both temperatures, and both strains of channel catfish had greater growth in weight or length at 27–31°C than at 32–36°C. Therefore, these results indicate that physiological performance, in terms of growth, decreases in channel catfish at temperatures greater than 27–31°C regardless of geographical origin of strain, whereas hybrid catfish did not show a decrease in weight under the same temperature conditions.     

A preliminary study on the effects of dietary supplementation of brewers yeast and nucleotides, singularly or in combination, on juvenile red drum (Sciaenops ocellatus)

This study was designed to evaluate the effects of dietary supplementation with brewers yeast (Brewtech^®) and nucleotides (Optimûn), either singularly or in combination, on red drum growth, body composition, stress responses and possible resistance to Amyloodinium ocellatum infection. Juvenile red drum (～1 g initially) fed practical fish‐meal‐based diets for 6 weeks had similar weight gain regardless of whether the diet was unsupplemented (basal) or supplemented with brewers yeast (2% of diet), nucleotides (Optimûn at 0.2% of diet) or both brewers yeast (2% of diet) and nucleotides (Optimûn at 0.2% of diet). Dietary effects on hepatosomatic index, intraperitoneal fat ratio or whole‐body composition were not significant, except that fish fed the singular nucleotide supplement had a significantly higher whole‐body lipid content compared with fish fed the basal diet. No significant dietary effects on cortisol response were observed after a 15 min confinement stress test perhaps because of the extreme variation among individual fish. Subsequently, in situ challenge by co‐habitation with A. ocellatum caused 100% mortality regardless of dietary treatment within a 48 h period. It is concluded that dietary supplementation of brewers yeast and nucleotides did not promote enhanced growth or improved cortisol response and resistance to uncontrolled amyloodiniosis in juvenile red drum, at least at the tested dosages.     

A histological study of gametogenesis in captive red snapper Lutjanus campechanus

Gametogenesis was monitored histologically in wild‐caught red snapper (Lutjanus campechanus, Poey) maintained in captivity under simulated natural photothermal conditions. Gonads were collected every 2–3 weeks (average n = 14) for histology during the pre‐spawning season (February to May, temperature increasing from 16°C to 24°C). Primary vitellogenic oocytes were first observed in one female when temperature reached 20°C. Subsequent samples revealed females in pre‐vitellogenesis or at early stages of vitellogenesis, although one female had tertiary vitellogenic (Vtg3) oocytes. The first histological signs of spermatogenesis were observed when temperature reached 17°C. Spermatozoa were observed in testicular lobules of all males sampled on 14 May (24°C) but little or no sperm was released during manual stripping. Ten males and 10 females were left in tanks and monitored for spawning. No egg release was observed during the monitoring period that encompassed the natural spawning season of wild red snapper. Ovarian biopsies taken during the late spawning season (16 July) revealed that four of eight sampled females had Vtg3 oocytes. Males were manually stripped but released no sperm. These results indicate that captive red snapper can complete gametogenesis in photothermal controlled systems. Additional research is needed to develop procedures that will achieve reliable maturation and spawning.     

Interactions between temperature and size on the growth,size heterogeneity,mortality and cannibalism in cultured larvae and juveniles of the Asian catfish,Pangasianodon hypophthalmus (Sauvage)

Temperature effects vary throughout the ontogeny, but are proportionally more variable during the early life stages than in older fish. The larvae of a few species have been studied but contrasting trajectories were observed, thereby making it difficult to predict how temperature impacts on the growth, survival and size heterogeneity in a particular species. This study examined these interactions in young [0.9 mg–1 g wet mass (WM)] Pangasianodon hypophthalmus, one of the most extensively cultured tropical fish. Fish were raised at five temperatures from 23 to 33 °C in a recirculated water system, fed in excess with a high‐energy feed (Artemia then a formulated feed, >50% protein), and examined at 1‐day (first feeding days) or 4‐day intervals (older fish). The temperature that produced the fastest growth (T°_opt) was 31 °C at the start of exogenous feeding (0.9 mg); it increased to 32.7 °C at 8 mg then decreased by 0.7 °C for each 10‐fold increase of WM. Size heterogeneity was lower and survival was higher (70–85% from 0.9 mg to 1 g) when the temperature was close to T°_opt. Comparisons with other species suggest that the slope of the relationship between T°_opt and fish size has a strong latitudinal component, and may also reflect the fish sensitivity to oxygen.     

Effects of temperature,salinity and body size on the physiological responses of the Iwagaki oyster Crassostrea nippona

The physiological responses of the juvenile Crassostrea nippona in terms of filtration, oxygen consumption and ammonia excretion to changes in temperature (16–32°C), salinity (15–35 psu) and body size (small, medium and large) were investigated. In this study, the values of filtration rate (FR), oxygen consumption rate (OCR) and ammonia excretion rate (AER) increased with temperature rising from 16°C to 24°C, reaching the highest values at 24°C and 28°C; with any further increase in temperature above this limit, these values decrease drastically (p < .05). The highest Q₁₀ coefficients were 2.75 for large, 3.54 for medium at 16–20 and 3.47 for small size at 20–24°C respectively. Moreover, the responses of FR and OCR were found to be influenced significantly by salinity, tending to increase concomitantly with salinity up to 25–30 psu, though the values of these parameters were diminished dramatically (p < .05) above this level, showing a reverse pattern from that observed in AER, which firstly decreased to the lowest level at 25 and 30 psu, and then severely (p < .05) increased to the highest level at 35 psu. In addition, the low O:N ratios of all sizes of C. nippona at 16°C and 30–35 psu were indicative of a protein‐dominated catabolism, whereas the O:N ratios of large size at 20–32°C and all sizes at 20–30 psu, indicating that the metabolic energy from protein diminished and lipid and carbohydrate were used as the energy substrates. Physiological rates of C. nippona were well correlated with its size. The average values of mass exponents (b‐values) estimated in the present study were 0.657 for OCR and 0.776 for AER at different temperatures, and 0.647 for OCR and 0.767 for AER at varying salinities, signifying that physiological process of C. nippona becomes relatively slower with increasing body size regardless of temperature or salinity. Finally, our results confirm that the optimal temperature and salinity for juvenile C. nippona lie within 24–28°C and 25–30 psu respectively. The results of physiological traits in response to environmental factors of this species are informative in site selection for the cultivation.     

iTRAQ‐based quantitative proteomic analysis of Sargassum fusiforme in response to high temperature stress

Global warming increases seawater temperature, causing high temperature stress to marine organisms, including algae. This study aimed to explore the global proteomic response of Sargassum fusiforme under high temperature stress. Sargassum fusiforme seedlings were cultured in natural seawater for 24 hr and subjected to different temperatures (22°C, control group; 27°C and 32°C, high temperature stress group) for 1, 3, 5 and 7 days. Changes in their membrane lipid peroxidation after high temperature stress were investigated. Proteomic changes in the air bladders of S. fusiforme were analysed using isobaric tags for relative and absolute quantification, along with liquid chromatography–tandem mass spectrometry. Data were analysed using bioinformatics methods. Results showed that high temperature stress destroyed the cell membrane of the air bladders. Further, 28 and 53 differentially expressed proteins (DEPs) were found in the 27°C and 32°C treatment groups respectively. These DEPs were mainly involved in glycolysis, single‐organism catabolism, purine nucleoside diphosphate metabolism and carbohydrate catabolism. In addition, DEPs were significantly enriched in 10 pathways, such as glycolytic process, biosynthesis of antibiotics, ribosome, biosynthesis of secondary metabolites and biosynthesis of amino acids. Proteomics analyses indicated that proteins associated with synthesis, folding, degradation, photosynthesis and energy and carbohydrate metabolism are differentially expressed under high temperature stress and normal conditions.     

Effects of temperature and salinity on the survival and development of mud crab, Scylla serrata (Forsskål), larvae

The combined effects of temperature and salinity on larval survival and development of the mud crab, Scylla serrata, were investigated in the laboratory. Newly hatched larvae were reared under 20 °C temperature and salinity combinations (i.e. combinations of four temperatures 25, 28, 31, 34 °C with five salinities 15, 20, 25, 30, 35 g L⁻¹). The results showed that temperature and salinity as well as the interaction of the two parameters significantly affected the survival of zoeal larvae. Salinity at 15 g L⁻¹ resulted in no larval survival to the first crab stage, suggesting that the lower salinity tolerance limit for mud crab larvae lies somewhere between salinity 15 and 20 g L⁻¹. However, within the salinity range of 20–35 g L⁻¹, no significant effects on survival of zoeal larvae were detected (P>0.05). The combined effects of temperature and salinity on larval survival were also evident as at low salinities, both high and low temperature led to mass mortality of newly hatched larvae (e.g. 34 °C/15 g L⁻¹, 34 °C/20 g L⁻¹ and 25 °C/15 g L⁻¹ combinations). In contrast, the low temperature and high salinity combination of 25 °C/35 g L⁻¹ resulted in one of the highest survival to the megalopal stage. It was also shown that at optimal 28 °C, larvae could withstand broader salinity conditions. Temperature, salinity and their interaction also significantly affected larval development. At 34 °C, the mean larval development time to megalopa under different salinity conditions ranged from 13.5 to 18.5 days. It increased to between 20.6 and 22.6 days at 25 °C. The effects of salinity on larval development were demonstrated by the fact that for all the temperatures tested, the fastest mean development to megalopa was always recorded at the salinity of 25 g L⁻¹. However, a different trend of salinity effects was shown for megalopae as their duration consistently increased with an increase in salinity from 20 to 35 g L⁻¹. In summary, S. serrata larvae tolerate a broad range of salinity and temperature conditions. Rearing temperature 25–30 °C and salinity 20–35 g L⁻¹ generally result in reasonable survival. However, from an aquaculture point of view, a higher temperature range of 28–30 °C and a salinity range of 20–30 g L⁻¹ are recommended as it shortens the culture cycle.     

Replacement of Fish Meal with Plant Feedstuffs in the Diet of Red Drum,Sciaenops ocellatus: Effects on Production Characteristics and Tolerance to Aquaculture‐Related Stressors

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.     

The effects of temperature, body weight and hypoxia on the oxygen consumption of the Mexican mojarra, Cichlasoma urophthalmus (Günther)

Abstract. The oxygen consumption rate of the Mexican cichlid, Cichlasoma urophthalmus Günther, was determined using closed-circuit respirometry at 20,25,30 and 36°C over a weight range of l·91–116g. Oxygen consumption rates ranged from 31 to 4500mg/kg/h and were slightly higher than for other cichlid species reported. Q10 was 2·49 between 20°Cand 30°C, but showed a direct increase with temperature. The species is an oxygen conformer, with an estimated critical oxygen tension of 70 mmHg at 28°C. This confers good low oxygen tolerance and some advantages for culture. The fish were able to withstand virtual anoxia for up to 2h. The significance of these results is discussed.     

Food consumption and digestive enzyme activity of Clarias batrachus exposed to various temperatures

The effect of temperature on the food consumption rate and the digestive enzyme activities of Clarias batrachus (80.60 ± 5.34 g) were evaluated. Fish were exposed to six different temperatures of 10, 15, 20, 25, 30 and 35 °C following an acclimation temperature of 25 °C. The rate of temperature change was 2 °C day^?1. Highest food consumption was recorded at 25 °C. It gradually reduced with decreasing water temperature. Food consumption rate was significantly (P < 0.05) lower at 10 °C compared with other treatments. Hence, 46.67, 8.20–23.58 and 1.02–6.15% reduced food consumptions were recorded in groups exposed at 10, 15 and 20 °C temperatures, respectively, compared with the 25 °C. The consumption rate was not affected in fish exposed at 30 and 35 °C. Total protease, trypsin and chymotrypsin activities were significantly (P < 0.05) higher in fish exposed at 25 °C compared with others. Lipase activity was significantly (P < 0.05) higher in fish exposed at 30 °C compared with others. Lowest enzyme activities were recorded at 10 °C. Water temperature below 25 °C affected the food consumption and digestive enzyme activities in fish that served as indicators of stress in fish.