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The concept of continuous egg and adult separation was studied to evaluate the possibility of cultivating the copepod Acartia tonsa at high density (> 2.5 adults mL−1). First experiment: Densities of 5, 10, 15, 30, and 45 adults mL−1 were evaluated. For this, eggs spawned were allowed to settle quickly, harvested, and counted to determine the specific and relative egg production (SEP and REP, eggs female−1 day−1 and eggs mL−1 day−1, respectively). Second experiment: Mature females were spawned on slides to observe the shape of the freshly spawned eggs. Third experiment: respiratory rate under four corporal velocities in the filter system were evaluated (57, 115, 173 and 231 PL min−1; PL, prosome length), corresponding to four water exchange rates (50, 100, 150 and 200 volumes day−1). Fourth experiment: A high-density (7 adults mL−1) prototype based on continuous egg separation was designed and compared with daily egg harvest for siphon (control system). The specific egg production (SEP, egg female−1 day−1) and relative egg production were determined (REP, eggs mL−1 day−1). The SEP decreased with culture density (p 2.5 mL−1), which was confirmed by higher REP in the prototype (100 eggs mL−1 day−1) than in the control system. This study contributes to intensive A. tonsa culture; a superior density of 5 mL−1 is possible with a high water exchange rate and careful egg harvesting.

In calanoid copepods, intensive culture is preferred, but currently, densities do not exceed a few adults per milliliter. Several explanations exist, but none have allowed increasing the density of adults. This study proposes a new explanation for the problem of adult density in intensive culture, using the copepod Parvocalanus crassirostris as a model. First: eggs (2 h old) were supplied to adults kept at 20 adults mL−1 in 1 L containers with and without microalgae; constant aeration was supplied to determine egg survival to damage caused by the adults. Different samples were taken up to 175 min. Second: A high-density spawning test (5–80 adults mL−1) was performed, using shallow depth (2.5 cm) and supersaturation level of oxygen for rapid egg separation and sufficient oxygen for adults, respectively. The SEP (egg female−1 day−1) and REP (egg mL−1 day−1) were determined. Third: two systems of continuous egg harvesting, filtration and sedimentation, were evaluated under a high density of adults culture (10 adults mL−1). The adults of P. crassirostris quickly damaged the eggs, but the presence of food reduces the damage caused. Adults presented high SEP up to 10 adults mL−1; however, REP increased significantly to more than 170 eggs mL−1 day-1 using densities of 20 and 30 adults mL−1 (p

This study provides a first evaluation of different hatchery culture methods for the giant clam Tridacna noae. Three culture methods (intensive, semi-intensive, and extensive) using two tank designs (60 L and 277 L) were successful in producing 30-day old T. noae juveniles. There was no statistically significant interaction between tank design and culture method when considering cumulative survival (P = 0.89) or antero-posterior growth (P = 0.20), and the two tank designs did not influence cumulative survival (P = 0.78) or antero-posterior growth (P = 0.81). Differences in cumulative survival among the extensive (0.027 ± 0.015%), semi-intensive (0.005 ± 0.002%), and intensive (0.004 ± 0.001%) culture methods were non-significant (P = 0.11). The mean antero-posterior measurements at 30 days post-fertilisation among intensive (583.57 ± 12.71 μm), semi-intensive (530.92 ± 11.02 μm), and extensive methods (541.67 ± 10.95 μm), were also non-significant (P = 0.05). Further analysis of survival among different developmental stages identified significantly greater survival of T. noae between the pediveliger and juvenile development stages within the extensive culture method. Our results show that extensive culture methods can achieve comparable hatchery production of T. noae to semi-intensive and intensive culture methods, which require additional managerial, infrastructural, and nutritional inputs.

Feeding is a key factor in the growth performance of rainbow trout farming, its sustainable production and profitability. However, supplying the daily ration in trout farming in flow-through system without any control is an inconceivable practice both economically and environmentally. In this study, the effect of different feeding regimes has been evaluated to optimize growth performance minimizing the feed wastage for simulating realistic intensive culture conditions (daily ration and feeding frequency per day depending on temperature and stocking density). Growth patterns of the reared fish in terms of average daily gain (ADG) and specific growth rate (SGR%) at two feeding schedules (FS-I & FS-II) and three stocking densities (Sd1, Sd2, Sd3) showed that the best performance was at Sd2 (R2 = 0.869) at FS-I and it was highly significant (P

The aim of this study was to develop a commercial-scale biofloc-based tank system for shrimp culture in an efficient and environmental-friendly way. Eight independent and identical tanks (6 m/length × 6 m/width × 1 m/height, water volume of 30 m3) were randomly selected and prepared for the trial: four were from indoor and other four from outdoor. A complete production trial for super-intensive culture of L. vannamei was conducted under both indoor and outdoor environmental conditions simultaneously. In the trial, ten-day-old post-larvae of L. vannamei were stocked at a density of 580 ind m−3 and cultured for 13 weeks, obtaining survival rates of 82.7% and 81.3%, yields of 6.75 and 7.36 kg m−3, and FCRs of 1.32 and 1.25 under indoor and outdoor culture conditions, respectively. For producing one kg of shrimp, the usages of water, molasses and sodium carbonate were 210 L, 0.23 L and 0.27 kg under indoor condition and 217 L, 0.15 L and 0.19 kg under outdoor condition, respectively. Throughout the trial, the concentrations of both TAN and NO2−-N first increased and then decreased during the early to middle phases and then maintained below 1.0 mg L−1 until the end under both indoor and outdoor conditions. After mature bioflocs established in the culture water, diverse bacterial communities were detected from sampled bioflocs, with Shannon index significantly higher in outdoor than in indoor condition. Top eleven abundant phyla and top nine abundant genera of bacteria with relative abundance over 1% were all shared by both culture conditions, although most of them had significant differences in relative abundance between the two conditions. Notably, communities of nitrifying bacteria were detected in the bioflocs but with very low relative abundances under both culture conditions. Taken together, these results demonstrate the efficiency of a commercial-scale biofloc-based system for super-intensive culture of L. vannamei under limited water exchange. Moreover, the data suggest that the outdoor environmental conditions were more favorable in terms of production performance and inorganic nitrogen control of the system. Improved application of biofloc technology was also discussed and proposed for inorganic nitrogen control in intensive shrimp culture.

As the demand for fish increases and limitations are placed on water use, intensification in closed aquaculture systems could help to increase its sustainable production. The Amazon region stands out for its stable warm climate with fast-growing and resilient fish. This study evaluated the efficacy of two aeration regimes on intensive rearing of tambaqui, Colossoma macropomum, in six 46.4-m3 concrete-wall earthen bottom ponds, with no water exchange. Two aeration regimes were tested: (1) emergency aeration (EA), in which the aeration system was activated with dissolved oxygen (DO) levels below 3 mg L−1; (2) supplemental aeration (SA), with 8 h of aeration every night, and also during days with low solar radiation. Water quality, fish performance and health (haematological and parasitological indicators), aeration use and cost were assessed. Juveniles (44.39 ± 9.72 g, mean weight ± SD) were stocked in six concrete-wall ponds with earthen bottoms at 32,300 ha −1 and fed commercial feed (36–32% crude protein) for 17 weeks (122 days). Mean values of the water quality parameters showed no difference between treatments, but occurrences of hypoxia were significantly higher in SA (31 hypoxias with DO

Aerators are essential and crucial auxiliary devices in intensive culture, especially in industrial culture in China. In this paper, we propose a real-time expert system for anomaly detection of aerators based on computer vision technology and existing surveillance cameras. The expert system includes two modules, i.e., object region detection and working state detection. First, we present a small object region detection method based on the region proposal idea. Moreover, we propose a novel algorithm called reference frame Kanade-Lucas-Tomasi (RF-KLT) algorithm for motion feature extraction in fixed regions. Then, we describe a dimension reduction method of time series for establishing a feature dataset with obvious boundaries between classes. Finally, we use machine learning algorithms to build the feature classifier. The proposed expert system can realize real-time, robust and cost-free anomaly detection of aerators in both the actual video dataset and the augmented video dataset. Demo is available at https://youtu.be/xThHRwu_cnI .

China is the largest producer and consumer of abalone worldwide, harvesting nearly 140,000 tons in 2016. Due to rising temperatures, intensive culture patterns, and other factors, hypoxia has become a serious problem for Chinese abalone aquaculture, especially in Fujian Province. A hypoxia-tolerant strain is needed for the sustainable development of abalone farming. However, it is problematic to evaluate hypoxia tolerance in abalone. Usually, the traditional analyses cause severe damages to the sampled individuals, possibly including disorders in gonad development or death and these samples could hardly be used for breeding. Here, it was found that abalone heart rates characteristically exhibited a sharp decline below a certain DO threshold, which can be referred to as the breakpoint of dissolved oxygen (BPDO). The BPDOs were sensitive to temperature – the higher acclimation temperature or experimental temperature would increase BPDO. To verify the utility of BPDO as an indicator of hypoxia tolerance in abalone, an acute stress test was conducted with 32 abalone individuals under severe hypoxia (~0.5 mg/L) and significant negative correlations between BPDO and attachment duration, and between BPDO and survival time were found. The BPDO method was advantageous, as it supported individual detection and survival, which allows the selection and retention of hypoxic-tolerant individuals for further genetic breeding. BPDOs at different temperatures also provide important references for abalone aquaculture.

Chirostoma estor estor, commonly known as whitefish, is an important species that lives in some Mexican lakes and is endangered due to overexploitation. This work proposes a new computational model for water quality assessment in freshwater intensive culture tanks using fuzzy logic, and an Analytical Hierarchy Process (AHP). The most critical parameters for whitefish culture, namely dissolved oxygen, pH, temperature, total ammonia, and non-ionized ammonia, were measured. Using measurements from real cultured tanks, different situations were studied to define importance parameter weights. As a result, an index concerning good or bad water quality conditions was obtained. Chirostoma farms were assessed using the proposed index to detect potential undesirable situations, improving water management for a constant growth, reproduction and survival of this important fish.

Cannibalism is a major cause of mortality in the intensive culture of the spotted seatrout, Cynoscion nebulosus . Increased feeding frequency may reduce attacks on conspecifics and enhance growth due to less energy spent on aggression, or more efficient digestion of smaller ration parcels. The goal of this study was to examine the effects of feeding frequency on aggressive and cannibalistic behaviors in larval hatchery-reared spotted seatrout. Ten-day-old reared larvae stocked at 30 fish l − 1 were subjected to one of four feeding frequencies (every 1, 2, 4, or 8 h) for eight days by subdividing the total ration of enriched Artemia accordingly. Blocks of three replicate tanks per treatment were monitored from 2-h before feeding until 1-h after feeding via four video cameras. For each tank, two pre-selected 30 min segments starting 30 min before and 30 min after each feeding event were scored for the number of nips, chases, and captures (Type 1 cannibalism). Three main factors, Frequency, Day, and Time were significant for all three behaviors. Significant Frequency × Time interactions along with follow-up tests of interaction means indicated that the numbers of nips and chases were lower after feeding than before feeding for all but the most frequent (1-h) feeding frequency. The 2-h frequency treatment elicited the fewest aggressive and cannibalistic acts, likely reflecting the best balance between the opposing effects of ration size on satiation and feeding frequency on gut evacuation time. Specific growth rate (SGR) was relatively high and did not differ between the 2-h and conventional 8-h frequencies; but size heterogeneity was significantly higher for the 8-h frequency treatment.

a b s t r a c t This article models the growth of a population in aquaculture, including the phenomenon of size hetero- geneity. Experimental observations of six initial densities (90, 130, 180, 230, 280 and 330 shrimps m−2) in an intensive culture of Penaeus vannamei in freshwater were used to fit a growth model. For this, three mathematical functions were analysed (Gompertz, von Bertalanffy and Putter), which were modified in order to include the effect of initial density. Two models were constructed, one assuming the hypothesis of homogeneous individual growth and the other including size-heterogeneity throughout the culture cycle. For the second case, a stabilisation time was evaluated which defines the future heterogeneity of the cohort. In each initial density, the stabilisation phase was reached at approximately 2 g. However, the time taken for this phase to start increased with increasing initial culture density. The modified von Bertalannfy function was the most effective of the three equations in predicting growth. The weight pre- dictions, assuming homogeneity and variability of sizes, presented low Percentage Root Mean Square Errors (PRMSE). However, the inclusion of size variability in the fit produced better statistical results than when they were not included (PRMSE decreased from 16% to 12%). This confirms the importance of taking into account size heterogeneity at an intensive level. Particularly at the technical level when the

article i nfo The objective of this study was to determine the effect of temperature on growth and survival of larval and juvenile burbot, Lota lota maculosa. Burbot aquaculture is developing primarily in response to declining wild stocks and a need to restore such populations. Beyond conservation efforts, there is also potential to culture this species commercially. However, many important aspects of burbot culture remain unaddressed. In this study larval and juvenile burbot were reared at three constant water temperatures (10, 15, and 20 °C) in an intensive culture setting. Two 30 day trials were conducted during the larval life stage and one 60 day trial during the juvenile life stage. In Trial 1, larval burbot (mean total length±SD, 6.9±1.0 mm, approximately 65 days post hatch) reared at 20 °C grew the fastest, while growth was lowest in the 10 °C treatment. Survival was inversely related to temperature, with the lowest average of 6.6% observed in larvae reared at 20 °C. The percentage cannibalized was quantified and found to be positively correlated with water temperature, and reached 58.0% in larvae reared at 20 °C. In Trial 2, as larvae approached metamorphosis (12.9±1.9 mm, approximately 100 days post hatch), growth was also highest in fish at 20 °C and lowest in those at 10 °C. At this stage survival was higher in fish at lower temperatures, but the percentage cannibalized appeared independent of temperature, averaging over 50% in fish at all temperatures. In Trial 3, growth of juveniles (59.9±12.4 mm, approximately 205 days post hatch) reared at 15 and 20 °C was not significantly different, yet both displayed significantly increased growth relative to juveniles reared at 10 °C. Juveniles were fully transitioned to a dry diet, and survival averaged >93% in all culture temperatures. The percentage cannibalized during this life stage averaged b5%, and was not affected by temperature. This study demonstrated the importance of water temperature, as it clearly affects culture performance of larval and juvenile burbot. Results from this study have implications for maximizing growth during larval and juvenile life stages of this species, and provide a comparative, empirical framework for establishing conservation, or commercial aquaculture programs for burbot.

Diel oxygen consumption patterns were determined in this study for California halibut ( Paralichthys californicus ) 3.2, 4.4, 6.2, 7.5, 9.2, 11.8, 12.8 and 14.2 g and between 110.5, 113.8, 115.7, 117.9, 120.1, 126.5, 132.4, 140.6, and 165.6 g held under farm-like conditions. The concept farm-like refers to a fish rearing condition as close as possible to a farming operation in terms of density, loading, and daily management. Open respirometries were performed in culture raceways during 24 h cycles while fish were growing from 3.2 g up to 165.6 g to determine hourly oxygen consumption rates by mass balance calculations. Fish were offered feed continuously during 12 h (within the 16 h light phase) resulting in maximum daily oxygen consumption rates that were between 1.2 and 1.5 times the mean daily values. A typical diel oxygen consumption pattern of the smaller group of fish tested (range between 3.2 and 14.2 g) had a peak during the feeding period, and relatively low and falling oxygen consumption after feeding was stopped. Oxygen consumption of the larger group of fish (range between 110.5 and 165.6 g) showed a less marked diel variation and did not change significantly after feed was distributed. In conclusion, diel oxygen consumption rates for California halibut reported here are key bioengineering parameters to be used when designing and sizing a rearing facility for the intensive culture of California halibut.

We examined the effect of light regime on daily egg harvest ( EH , eggs tank − 1 d − 1 ), and 48-h egg hatching success ( HS , %) by Acartia tonsa (Copepoda: Calanoida) in intensive 130-l cultures. Since this copepod produces more eggs during darkness than in the light, we tested whether EH could be increased by utilizing unnatural light regimes. Egg harvests were between 0.85 to 1.20 million eggs culture − 1 wk − 1 and mean EH was not significantly different among tanks maintained at 3 h:3 h, 4 h:4 h, 6 h:6 h and 12 h:12 h light:dark. HS was not significantly different for eggs produced in the different light regimes and incubated at 12 h:12 h. In a second experiment, cohorts were reared (from nauplii) in constant darkness (D) and constant light (L) and eggs produced in each cohort were incubated in darkness (D–D, L–D) or light (D–L, L–L). Mean(± SE) HS was significantly different among the treatments, increased with increasing light exposure, and equal to 3.7(1.1), 32.2(15.1), 38.3(0.8) and 52.2(16.5)% for D–D, L–D, D–L and L–L treatments, respectively. These and published data were combined to generate an equation predicting 48-h HS for eggs produced and incubated at photoperiods between 0.5 and 24 h. Our experiments indicated that light can be an important factor affecting the success of intensive cultures of A. tonsa and that copepod culture protocols should include information on light regimes used during rearing and incubation of eggs.

Rearing crayfish in individual compartments could be a means of overcoming social-dependent density limitations in order to increase yields per unit area in intensive culture. Two experiments were conducted to evaluate the impact of neighbors on the growth of redclaw crayfish (Cherax quadricarinatus) males in three-dimensional units, consisting of 144 individual compartments, designed for intensive battery culture. The first experiment revealed significantly lower growth rates in crayfish surrounded by neighbors on all sides than in those reared with no neighbors in adjacent compartments, or with neighbors only in compartments on the same level but not above or below them. The second experiment revealed significantly lower growth rates in relatively small crayfish surrounded by large crayfish in a mixed-size unit than in those surrounded by similar-sized small crayfish in a uniform-size unit. No such effect was found for relatively large crayfish surrounded by small crayfish. The results clearly indicated interactions between crayfish in our system, despite them being housed in separate compartments. Growth was adversely affected by the presence of neighbors in adjacent compartments, especially vertically adjacent ones, and the presence of larger individuals in adjacent compartments. This social effect was attributed to partial tactile contact between neighbors in our system. The consequences of these findings for battery culture of crayfish are discussed.

The aims of this study were to determine whether growth, feed handling and feeding efficiency of gilthead sea bream ( Sparus aurata ) changed in response to imposed competition levels, manipulated by altering ration and feed delivery rate, and to investigate the effect of feed handling on feed conversion efficiency. Triplicate tanks of bream (32 g, 12 kg m −3 ) were fed rations of 3.5%, 3%, 2.5% or 2% BW day −1 at a rate of ca. 10 g min −1 , in three meals. To compare the effect of feed delivery rate, triplicate tanks were fed a 3% BW day −1 ration at a rate of ca. 20 g min −1 . Low rations increased competition levels; feeding intensity, density of fish under the feeder and frequency of sharp-angled turns increased during meals. Increasing the feed delivery rate had a weaker influence on competition; feeding intensity was higher and sharp angled turns more frequently observed but fish density under the feeder increased and swimming speeds decreased during feeding for both feed delivery rates tested. Increasing ration and feed delivery rate led to an increase in feed intake, growth rate, rate of chewing and proportion of feed particles in the stomach. High feed delivery rate also appeared to result in a reduction in waste from chewing. Bream fed the 3% BW day −1 ration (just under satiation) delivered at a high rate had the lowest standard FCR. This was also true for when calculating FCR, taking into account the actual feed intake. However, when taking waste from handling feed into account, the resulting FCRs were higher in treatments where waste from chewing was reduced i.e. for bream fed at the high rate of feed delivery. The results are discussed in terms of improved feeding practices for the intensive culture of this species.

In the framework of the France–Brazil cooperation in Oceanology, experiments have been carried out in the State of Bahia (Brazil) from 1992 on, in order to design a new technology for culture shrimps in floating cages in an estuarine zone. The zootechnical research has focused on the species Penaeus vannamei which has been tested in different rearing conditions (density in the cages) and seasons (wet and dry). The results may be compared with the most intensive and costly technologies which are practised in Asian countries. The average growth rate is about 0.8 g wk−1 and the average final biomass is 800 g m−2. The achieved results are all the more important as they are obtained with a simple technology which does not require energy for pumping and mechanical water aeration. Investigations on the impact of this kind of technology, carried out on a pilot site with estuarine conditions after three years of farming activity, showed no measurable effect on the sediment (in terms of organic matter) and in the water (in terms of oxygen). Economic analysis was recorded from the very beginning of the project, making it possible to design a computerised simulation tool in order to assess the feasibility of such an operation and to help in decision making for future research and development. Initial results indicate that ex-farm production costs for shrimps weighing 15 g would be around US$ 4.7 per kg. The major competitive advantages of such a technique are the high yield, the quality of the product, the environmental friendliness and the positive social impact for a fishing community.

Intensive culture of frogs is one of the most complicated forms of aquaculture. Standard management techniques for laboratory or commercial culture are being developed. Tadpole density is one of the most important factors to consider when rearing anurans. The experiment was performed on Rana perezi tadpoles to test the effects of density on growth and metamorphosis. Effects of larval density were examined by subjecting tadpoles to four different densities (1, 5, 10 and 20 larvae l −1 ). Density affected growth rate, weight at metamorphosis, survival and duration of larval stage. Results agree with previously known relationships for ranids: at higher densities developmental time is longer, mean size at metamorphosis is smaller, and mortality is higher. There are clear benefits in rearing R. perezi larvae at low densities (5 larvae l −1 ).

An experiment was established in central New York State in 1987 to determine the effect of spacing and fertilization on wood biomass production of one willow clone grown with intensive culture and harvested annually. Spacings were 0.15 × 0.15, 0.30 × 0.30 and 0.46 × 0.46 m. Half of the plots were fertilized annually with N, P and K at elemental rates of 336, 112 and 224 kg ha−1. All plots were irrigated during their third, fourth and fifth growing seasons. Fertilizer increased the rate at which trees attained their maximum production, but their maximum estimated production level was reduced compared with non-fertilized trees. Trees responded positively to fertilizer during the first three growing seasons. Trees spaced at 0.46 × 0.46 and 0.30 × 0.30 m had significantly higher maximum estimated production levels than trees spaced at 0.15 × 0.15 m. During the fourth and fifth growing seasons, trees spaced at 0.46 × 0.46 m were most productive, but cumulative production after five successive annual harvests was highest by trees spaced at 0.30 × 0.30 m. Survival remained high (83% averaging spacing and fertilizer treatments) after five harvests and was not affected by spacing or fertilization.

Genetic manipulation of predominantly monofactorial sex determining mechanisms in the Nile tilapia Oreochromis niloticus is proposed as a technology for the mass production of all-male progeny for culture. Existing alternative methods for producing all-male tilapia, principally direct hormonal masculinization, have produced inconsistent results and are largely the preserve of scientists and developed country aquaculturists. Successful adoption of these techniques in developing countries is seriously limited by the number and complexity of factors involved in their effectiveness. Novel YY-male genotypes have been shown to be viable and to produce all- or nearly all-male (XY) progeny in crosses with normal XX females. This paper presents the results from a series of on-station growth performance trials of these genetically male tilapia (GMT) in three environments. Two comprehensive and replicated trials in extensively managed earthen ponds, compared the performance of GMT with sex reversed male (SRT) and normal mixed sex tilapia (MST). Three further, smaller experiments, compared the growth of GMT with that of MST populations in rice-cum-fish culture and under intensive culture in closed recirculating systems. These comparisons were made within the ‘Egypt-UCS’ strain of O. niloticus. Results indicate that culture of GMT populations can improve marketable yields under all environments. In the first experiment in ponds, GMT had significantly (P = 0.003) higher yields than both MST (+ 58.8%) and SRT (+ 31.03%). The second experiment, following the same design, showed a similar trend, although differences were smaller and not significant. GMT produced yields 11.9% greater than MST in rice-cum-fish culture and 33.6–47.0% greater in recirculating systems. There was no recruitment in GMT pond populations whereas recruits were present in MST and SRT populations. Coefficient of variance for individual weight in ponds was significantly (P < 0.05) lower for GMT than for MST for both pond experiments. GMT produced from novel YY-males in this strain has considerable potential for increasing yields from tilapia culture.

Short rotation intensive culture plantations can be managed under a single rotation or coppice system. This paper shows the optimality conditions that must exist in order to maximize volume production of short rotation coppice stands. The results indicate the importance of equating the current annual increment of the stand to its mean annual increment whether managing with a single rotation or a series of coppice rotations over a cycle of time. The mathematical conditions for having the coppice system rather than the single rotation for volume production are also derived. These conditions indicate the average of the mean annual increments for the coppice harvests must be greater than the maximum mean annual increment of the single rotation. Finally, an example illustrates an application of the optimality conditions to a set of hypothetical data.

Experiments were undertaken on two groups of South African abalone, Haliotis midae , with different thermal histories to determine their critical thermal maximum and their preferred temperature. There was no difference between the two groups in terms of their thermal preference and critical thermal maxima. The final temperature preferendum was determined in a horizontal thermal gradient chamber and was found to be 24.1–24.5°C, which was significantly higher than ambient environmental temperatures. The 50% critical thermal maximum was 27.9°C. The results are discussed in relation to the natural distribution of the species, and the implications of these findings are considered for site selection and commercial rearing.

Egg development of perch (Perca fluviatilis L.) at a series of constant temperatures, and larval survival and growth in intensive culture systems at different temperatures and food densities were compared. Hatching was observed within the temperature range of 6–22°C, with the highest survival between 12 and 20°C. The longer larvae at mass hatching were found at 12 to 18°C. In one trial, 4-day-old larvae were fed at 15 and 20°C with 0, 500, 3000, 6000, 9000 and 12 000 rotifers·l−1 over a 9-day period. A high mortality was observed during the second week after hatching. Survival and growth of larvae at different temperatures and food densities were significantly different. The best survival and growth were observed at 20°C and 6000 rotifers·l−1. In another trial, 12-day-old larvae were fed at 15 and 20°C with 0, 50, 100, 200, 400, 600, 800 and 1000 copepodites·l−1 over a 12-day period. Survival rates were similar between both temperatures but growth was significantly better in the warmer water. Survival rates at both temperatures increased with copepodite densities from 50 to 200·l−1. At 200 or more per liter, survival rates were similar, but growth rates were highest at 400–1000 copepodites·l−1 and 20°C.

Growing interest in woody biomass for energy in the midwestern U.S. will require information on species and site productivities. We investigated 3, 6 and 14 year yields of the nitrogen-fixing tree species. European black alder, at three spacings on a marginally productive soil in central Indiana, U.S.A. The highest yield was 10 Mg ha −1 yr −1 at age three at the closest spacing of 0.5 × 1 m. Other spacings and ages provided smaller yields. Fertilization with phosphorus and potassium only provided a response in the initial 3 year rotation. Whole-tree and stem-only harvests removed varying levels of nutrients from the site. However, on these marginally productive sites where N and sometimes P are limiting, sustainable harvesting could be maintained due to the nitrogen-fixing capability of this species and the effects of N fixation on P availability. Preliminary economic analyses indicated that growing biomass on farms could be profitable, but only with farm or forestry program cost-sharing assistance. Where establishment expenses could be reduced by wider spacings, the use of seed rather than seedlings, or farmer-substituted labor, returns to the farmer were competitive with row-crop and timber production.

It is often argued that in short rotation intensive culture plantations, biomass productivity increases with narrower tree spacings. Biomass productivity and tree spacing relations were studied for up to 16 years in northern Wisconsin hybrid poplar plantations. Maximum mean annual biomass increment was 12.8 Mg ha −1 yr −1 for Populus clone NE-41 planted at a l m 2 spacing. Productivity differences related to spacing were found to be minor. Productivity was influenced mainly by clone, irrigation and disease. A hypothesis is proposed that time to canopy closure is linearly related to time to maximum mean annual biomass productivity. Wide spacing and wide-crown trees that permit wider tree spacing allow longer rotations, which can lower costs and increase flexibility in management.

An experiment was established in central New York State in 1987 to determine the biomass production potential of Salix using ultrashort-rotation intensive culture with annual harvests. Half of the plots were fertilized annually with N, P, and K, and all plots were irrigated during their third, fourth, and fifth growing seasons. The most productive clone, willow clone SV l, yielded 16 o.d. t ha −1 yr −1 during the fifth growing season. Fertilization significantly increased the rate at which clones reached their annual maximum biomass production, but the annual maximum level ultimately achieved was the same with or without fertilization. Total five year biomass production was increased by fertilization for specific clones. Large clonal variation in biomass production potential and survival was observed, along with significant clone-by-fertilizer interaction.

The use of 16.67 mg/l tetracycline was effective for the wound healing of injured epidermis within 28 days. Increased growth and better health conditions were observed for the tetracycline-treated fish.

Groups of age-0 pond-reared yellow perch ( Perca flavescens ) fingerlings were harvested and habituated to intensive culture conditions and formulated feeds under various treatment regimes. The habituation intervals for the different fish groups lasted from 19 to 51 days, until the number of dead fish recovered daily for each group became insignificant and all remaining fish were actively feeding. End points measured included (1) habituation, defined as the percentage of fish that survived the transition to intensive culture conditions; (2) starvation, defined as the percentage of fish that died and were recovered; and (3) cannibalism, defined as the percentage of fish that could not be accounted for at the end of the habituation intervals. The habituation of perch harvested at mean total lengths (TLs) of 16.9, 32.5, or 42.6 mm did not differ (53.3 ± 5.5, 68.3 ± 6.3, and 55.7 ± 4.5%, respectively), but habituation occurred faster and over a shorter interval in smaller perch. Perch harvested at 16.9 mm TL grew to a larger ultimate size than those harvested at 42.6 mm TL. Fingerlings harvested at 16–20 mm TL and initially stocked into 750-l tanks at 13.7 fish/l had improved habituation (53.3 ± 5.5%) and reduced cannibalism (20.3 ± 11.0%) compared to those stocked at 37.4 fish/l (28.0 ± 3.2 and 50.5 ± 3.2%, respectively). Perch reared using internal tank lighting had improved habituation compared to those reared overhead lighting (54.5 ± 3.2 vs. 42.7 ± 2.2%). Our results show that pond-reared perch fingerlings can be successfully habituated to intensive culture conditions at a mean size as small as 16.9 mm TL, and that fingerling production can be greatly improved by using a strategy of early pond harvest in combination with appropriate tank stocking densities and internal tank lighting.

A 2·6 m 3 round-bottomed trough and a 3·3 m 3 round tank with a hemispherical bottom were tested as potential modules for a production system for walleye (Stizostedion vitreum) larvae during the first 30 days after hatching. Each module was stocked with 50 000 larvae. The larvae were reared entirely on a prepared feed. After 30 days, survival in the trough was 47% but only 13% in the tank. Fish in both modules reached a total length > 30 mm after 30 days. Swim-bladder inflation in the tank was 69% but only 16% in the trough. Excessive horizontal water flow at the surface may have impeded inflation in the trough. Water quality in each system was satisfactory. The trough required the least maintenance.

This paper gives an overview of the potential interaction between cultured and wild Atlantic salmon in respect to disease, parasites, behavior-ecology and genetics. The threat from diseases and parasites is real and, in some cases, serious during interaction between reared and farmed Atlantic salmon. Diseases are a more serious threat to reared than to wild salmon owing to intensive culture, resulting stressful conditions and the ease of transmission of pathogens. Little is known of infections of wild salmon resulting from culture activity. Metazoan parasites can pose serious threats to both farmed and wild salmon. In the examples given, sea lice are of little danger to wild salmon but are a major concern in salmon mariculture. The fluke, Gyrodactylus salaris , is a serious threat to wild salmon in Norway where the parasite has been recently introduced from the Baltic area. Behavioral and ecological interaction between cultured and wild salmon is likely since it has been demonstrated that culture salmon do enter rivers and spawn. It is safe to assume that the two forms do interbreed but the extent is unknown. Cultured salmon quickly become genetically dissimilar to the wild stocks from which they are derived. Wild stocks are believed to have developed unique genotypes which are adaptive to local conditions and life history imperatives. Reasonably precise homing behavior is believed to have been responsible for development of unique genotypes and for helping to maintain this uniqueness. There is no consensus as to possible damage and loss of adaptivenes following inter-breeding a between potentially greatly different genotypes. It is recommended that a long-term study be conducted using farmed and wild salmon in a previously unaffected river to answer vital questions about behavioral interactions and the short- and long-term consequences of interbreeding between farmed and wild salmon.

The successful development of exclusively dry feed regimes for the intensive culture of lake white-fish larvae and fingerlings is reported. Whitefish larvae were reared on diets combining commercially-available dry larval feeds, live Artemia spp. nauplii, and decapsulated Artemia cysts, as well as on dry feeds only. Large-scale (>80 000 larvae per year) experiments were carried out over three consecutive year-classes. Growth to 800–1000 mg final fish weights, and 97–98% survival over the 56-day study periods were achieved on the most successful dry feed regimes. The methods employed for large-scale, production-oriented larval coregonid intensive culture, the performance of various commercial diets, and the potential causes of skeletal deformities observed on some diet regimes are presented.

Paramecium was cultured by batch and semi-continuous culture techniques, with addition of skimmed milk powder or fish liver to the medium. Batch culturing using skimmed milk powder was the most successful method in terms of both culture density and costs.

Fingerlings of Oreochromis niloticus (L.) (av. wt. 19.0 g) were stocked in 3.75-m3 outdoor concrete tanks at 240/tank, and reared for 98 days to evaluate the effects of rate of water exchange on growth, feed conversion and water quality. The average harvest weight of fish ranged from 122.4 to 87.6 g. The best growth was obtained with a continuous flow rate of 11/min per kg biomass (specific growth rate (SGR) 1.80, average daily gain (ADG) 1.06 g/day), closely followed by fishes receiving 0.5 l/min per kg (SGR 1.74, ADG 0.94 g/day). The poorest growth (SGR 1.46, ADG 0.7 g/day) occurred when the water was batch changed once every 24 h. With two batch changes daily, the average SGR and ADG were 1.63 and 0.86 g/day respectively. The feed conversion ratios ranged from 1.7 to 2.3, being low in tanks with continuous flow and high in tanks with batch exchange. As there was no significant difference in growth performance in two sets of flow-through tanks, a flow rate of 0.5 l/min per kg appears to be desirable for intensive culture of tilapia.

Yield increases of 2 to 3 times have been achieved for some agricultural crops over 40 years because of improved genetic material and culture. These increases suggest that similar yield increases might be achieved in short-rotation intensive culture (SRIC) energy plantations. Current poplar SRIC record small-plot yields are 4 to 7 times greater than average field yields. SRIC yields necessary for marginal profitability have not yet been attained in the field, but field yields are expected to increase based on the gains recently achieved in small experimental plots. The rate and potential size of future yield increases are uncertain, however. Whether the large yield gains achieved recently in agricultural crops can be duplicated in SRIC within a reasonable time will depend on a number of factors, including future investment in cultural and breeding research, and the realization of the biotechnology potential.

Short rotation intensive culture (SRIC) plantations, established in central Pennsylvania, were analyzed to determine their economic optimum rotation age. The general management design for the plantations used fertilized and non-fertilized strategies, a tree spacing of 0·48 m 2 and a rotation length of 4 years. A stand-level financial model analyzed the unit cost of production for alternate rotation lengths based upon the plantation's investment and operating costs and resulting biomass yields. Analysis of the first two rotations indicated that the minimum unit cost for fertilized and non-fertilized strategies was in the fourth year of the first rotation and the third year of the second rotation. Growth curves for the rotations also showed a maximum volume production at the same points in the rotations. Selection of a 3-year rather than 4-year harvest during the second rotation would reduce unit costs by 14% in the non-fertilized strategy and by 15% in the fertilized strategy.

The International Energy Agency (IEA) has recognized the importance of the proper use of current technologies in researching the concept of biomass as a renewable energy source. An early program included one project that dealt entirely with the mechanization of harvesting trees grown under short-rotation intensive culture (SRIC) forestry. The Bioenergy Agreement that ended 31 December 1988 expanded this involvement with mechanization by creating a separate Activity called ‘Production Technology’. This Activity investigated the current state of technology for establishing, managing and harvesting SRIC forests or plantations. Five countries participated: Canada, Denmark, Sweden, the UK, and the US. Several workshops were held, and a final joint project evolved. As the final effort, a ‘Sourcebook’ of Production Technology will be made available. A summary of the main findings is provided here. This document will be published by the IEA and updated in future years as needed.

Eel production in recirculation systems has grown rapidly in Denmark and there are now approximately 60 eel farms. Under the intensive culture conditions, fish diseases have caused substantial problems. The most important has been gill infections with monogeneans, Pseudodactylogyrus spp., but at times other parasitic infections as well as fungal and bacterial infections have caused severe problems.

Feeding experiments with carp were performed in plastic tanks, in cages and in experimental ponds, using pelleted rations of 25% total crude protein. Fishmeal was the only source of supplemental protein in the control ration, besides the basal ground grains. Partial replacement (40% of the fishmeal) by soybean meal in pond trials required only supplements of methionine and 5% oil in order to attain the same growth, protein and energy utilisation as with the control ration. When most or all of the fishmeal was replaced by soybean meal, supplements of methionine, 0.4–0.5% lysine and 10% oil were necessary to achieve gains, protein efficiency ratio (PER), net protein utilization (NPU), protein retentions and energy retentions equal to those of the control fishmeal ration. It was concluded that regular soybean meal contains 10–15% less available energy and 10–15% less available lysine for carp than the generally accepted values (as in NRC-NAS, Nutrient Requirements of Poultry, 1977).

Short-rotation intensive culture (SRIC) research has demonstrated that biomass yields can be substantially increased over those for conventional forestry. Moreover, this research has shown that the concept is technically feasible, and that costs of production are potentially competitive. The greatest potential for cost reduction lies in genetics, which appears to have the promise to increase productivity by as much as 40%. The development of innovative harvesting equipment can further reduce production costs by 30% compared with costs now experienced with conventional equipment. Although stand management research is now completed with regard to defining proper practices, there nonethe-less remains the potential for further cost reduction (e.g. refinement of yield-response relationships for various management practices). Many experimental plots are now entering the coppice stage. Productivity gains are almost certainly possible with development of management practices for established rootstocks. The ultimate test of the concept will require the demonstration of much larger monocultural plantations to identify uncertainties and financial risks.

Black burn spot exoskeletal lesions of bacterial aetiology are a frequent feature of crustaceans in intensive culture. The appearance under the scanning electron microscope of such lesions associated with Aeromonas hydrophila on Macrobrachium rosenbergii is described. The effect of oxolinic acid treatment on these lesions is discussed.

Tiger muskellunge ( Esox masquinony × E. lucius ) juveniles were reared at constant temperatures in the temperature range 14–28°C. For fish 3–4 cm long, growth, production and feed conversion efficiency were greatest at 20–22°C. Survival was reduced and unaccountable mortality (cannibalism index) was greatest at 24°C. Growth per unit of temperature was about equal over the range 16–22°C. For fish 12–13 cm long, feed conversion efficiency and mean individual growth were greatest at 23°C; growth per unit of temperature was nearly equal over the range 20–24°C.

Technological systems advances have shifted emphasis in aquaculture research to intensive culture, while biological understanding of pond ecosystems has not advanced commensurately. World aquaculture production will be dominated by earthen pond systems for some years to come, suggesting increased emphasis in this area. Transfer of research findings into commercial operations is hampered by differences in goods and priorities between the research and industrial sectors, and improved communications can help focus research on critical areas and improve the transfer of research results to operations. Neglected areas inviting further research include biological and chemical processes in the pond ecosystem, innovative harvesting techniques for earthen ponds, evaluation of new species for culture, utilization of processing wastes, and new nutrient input strategies to utilize local feedstuffs or cheaper nutrient sources.

Three shrimp growout trials were conducted in a 337-m2 round pond. Juvenile Penaeus vannamei were stocked at 45 shrimp/m2 and the trials lasted 74–85 days. Shrimp were fed once a day in trial 1 and four times per day in trials 2 and 3. In trial 1, survival was 90% and feed conversion was 2.0, while in trials 2 and 3 survival averaged 83±2.5% and feed conversion averaged 2.5±0.2. Shrimp growth dramatically increased from 0.7 g/week in trial 1 to 1.8±0.15 g/week in trials 2 and 3. Total production increased from 3360 kg/ha in trial 1 to 7406±206 kg/ha in trials 2 and 3. The combined production of trials 2 and 3 was 14 812 kg/ha in 156 days (from stocking of trial 2 to harvest of trial 3). Sedimentation rates in the pond center were 81% greater than at mid-radius and 172% greater than at the pond perimeter, indicating that the round pond design effectively concentrated sediments to the center where they were flushed out the drain. These results indicate that P. vannamei is well suited to intensive culture, exhibiting rapid growth, high survival, and uniform growth when stocked at 45 shrimp/m2. The round pond design appears to provide a high level of control over factors critical to intensive shrimp culture.

The establishment of short rotation, intensive culture, (SRIC) woody biomass plantations using hybrid poplar was cost analyzed on a financial and energy input basis. Establishment operations were at a commercial scale and met the power requirements of each task in a cost-efficient manner. Total establishment costs amounted to $1249 ha−1 and, on an energy cost basis, 16205 MJ ha−1. The planting operation was the largest expense, involving 73% of the total financial and energy costs in establishment. The second largest expense was herbicide spraying, costing approximately 22% on a financial and energy basis. In turn, establishment represented 36% of the total production costs in the 4-year rotation of non-fertilized plantations.

Above-ground growth of four Populus × euramericana clones was compared on intensively cultured plots in Ames, Iowa, and Rhinelander, Wisconsin. Clones 5323 and 5377 were superior biomass producers three years from planting. The lowest planting density (5,000 trees ha−1) produced the greatest leaf surface area and stem-branch per tree, whereas the highest density (15,000 trees ha−1) yielded the greatest leaf area and stem-branch per hectare. Better growth performance was shown at Ames than at Rhinelander.

A pelleted basal ration of 25% protein was spray-coated with oils of different origin — plant, chicken or fish, and fed to carp in experimental ponds and cages for 4–7 weeks. Acid oils and neutral oils were utilized equally well, except crude cottonseed oil. Carp grew normally on less than 0.5% ω: 3 fatty acids. Five percent oils increased yields in cages by 30–50%, and in ponds by 18%. Feed conversions were improved proportionally. Oiled pellets maintained growth rates and feed conversions at twice the stocking rate of the standard pellets. Protein retention and energy retention were increased; the marginal retention of energy due to the added oil exceeded 100% in several trials (increment of retained energy due to added oil ÷ increment of energy due to feed). The fat content of the carp was raised by 2% on average. The pattern of the body fatty acids tended to change in direction of the dietary oils, i.e. toward higher unsaturation.

This paper describes experiments in which nine species of prawns were compared for their suitability for intensive culture in closed systems. The species tested were: Macrobrachium rosenbergii, Penaeus aztecus, P. indicus, P. japonicus, P. monodon, P. occidentalis, P. orientalis, P. schmitti and P. setiferus. Tanks with a bottom area of 0.6 m2 and water depth 20 cm were stocked with juvenile prawns (0.2–0.5 g mean live-weight) of each species at two stocking densities, equivalent to 25 and 166 prawns/m2. Water conditions were maintained at 28±2°C and 28–30‰ (M. rosenbergii was reared in fresh water), and growth and survival were monitored during 16 weeks. Fastest growth was recorded for P. monodon and P. orientalis, which reached mean live-weights of 25.43 g and 22.80 g respectively at the low stocking density and 12.95 g and 14.63 g at the high stocking density. Best survival was recorded for P. monodon, which was considerably better than any of the other species. It was concluded that P. monodon and P. orientalis merit further consideration as candidates for intensive culture.

Growth trials were carried out with tilapia in experimental ponds to develop an animal-protein-free diet of nutritive value equal to a standard commercial fish-meal feed. A diet based on soybean meal and supplemented with amino acids, oil and di-calcium phosphate resulted in growth performances and body compositions equal to those on a fish-meal diet. Successive withdrawal of the supplements resulted in a final fish-meal-free diet, with 3% di-calcium phosphate and 2% oil as the only supplements necessary to achieve growth performances equal to those obtained with a fully supplemented diet.