Effects of Rice-Fish Co-culture on Oxygen Consumption in Intensive Aquaculture Pond

Rice-fish co-culture has gained increasing attention to remediate the negative environmental impacts induced by intensive aquaculture. However, the effect of rice-fish co-culture on oxygen depletion has rarely been investigated. We constructed a rice-fish co-culture system in yellow catfish (Pelteobagrus fulvidraco) and freshwater shrimp (Macrobrachium nipponense) ponds using a new high-stalk rice variety, and conducted a field experiment to investigate the effect of rice-fish co-culture on water parameters and oxygen consumption. The results showed that rice-fish co-culture reduced the nutrients (total nitrogen, ammonia-N, total phosphorous and potassium) and the dissolved oxygen content in fish and shrimp ponds. However, they showed similar seasonal change of dissolved oxygen in the water of fish and shrimp ponds. Rice-fish co-culture reduced the total amount of oxygen consumption and optimized the oxygen consumption structure in pond. The respiration rates in water and sediment were significantly reduced by 66.1% and 31.7% in the catfish pond, and 64.4% and 38.7% in the shrimp pond, respectively, by additional rice cultivation. Rice-fish co-culture decreased the proportions of respiration in sediment and water, and increased the proportion of fish respiration. These results suggest that rice-fish co-culture is an efficient way to reduce hypoxia in intensive culture pond.     

Partitioning characteristics of PAHs between sediment and water in a shallow lake

Goal, Scope and Background

Distribution of hydrophobic organic contaminants in abiotic compartments is essential for describing their transfer and fate in aquatic ecosystems. Taihu Lake is the third largest freshwater lake in China. Water quality of Taihu Lake has deteriorated greatly during the last decades and has threatened the water supply. The aim of the present study was to investigate the partitioning of polycyclic aromatic hydrocarbons (PAHs) among overlying water, suspended particulate matter (SPM), sediments, and pore water in Meiliang Bay, Taihu Lake and to provide useful information for the ecological engineering in this area.

Materials and Methods

Overlying water and surface sediment were sampled from six sites in Meiliang Bay, Taihu Lake, China. Within 72 h of sampling, sediments were centrifuged to obtain the pore water. Overlying water samples were filtered to separate dissolved and SPM samples. After extraction, samples were purified following a clean-up procedure. PAH fraction was obtained by elution with a mixture of hexane: DCM (7:3, V/V) and analyzed by GC/MS.

Results

PAHs concentrations in overlying water varied from 37.5 ng/L to 183.5 ng/L. Concentrations of PAHs in pore water were higher than those in overlying water. The total concentrations of 16 priority PAHs in sediments ranged from 2091.8 ng/g-dw to 4094.4 ng/g-dw. PAHs concentrations on SPM were decreased with suspended solid concentrations (SSC). Total PAHs concentrations on SPM varied in the range of 3369.6 ng/g-dw to 7531.1 ng/g-dw. The partition coefficients between sediment and overlying water (log K _oc) for PAHs with log K _ow<5 were positively correlated with their octanol-water partition coefficients (log K _ow) (n=39, r=0.79, p<0.0001). Partition coefficients between sediment and pore water (log K _oc′) for all PAHs were also significantly correlated with their log K _ow values (n=48, r=0.82, p<0.0001).

Discussion

In general, PAHs derived from combustion sources tend to bind strongly to soot particles in natural sediment. Consequentially, K _oc values observed in the natural environment could be orders of magnitude higher than those predicted by linear correlation relationships under laboratory conditions. In the present study, the ratio of log K _oc values to log K _ow values falls consistently above 1, indicating that the sediment soot carbon in the bay was more attractive for PAHs than n-octanol. The log K _oc′ was also higher than that predicted under laboratory conditions, suggesting that the measured pore water PAH concentrations were lower than those predicted. That is to say, not all the sediment PAHs can be available to partition rapidly into sediment pore waters. A variation in soot content is a possible reason. Furthermore, concentrations of PAHs on SPM were higher than those in sediments. The compositions of PAHs on SPM and in sediments were similar, indicating the importance of re-suspension process of sediments in the partitioning process of the shallow lake.

Conclusions

The results indicated the equilibrium partitioning model could be used to predict PAHs distribution in various phases of a shallow lake in the stagnation period, but re-suspension processes should be considered to modify the relationship between log K _ocs and log K _ows.

Recommendations and Perspectives

Concentration, particle size and composition of resuspended particles could affect the relationship between log K _ocs and log K _ows. Further work should be done under field conditions, especially where a steady thermodynamic equilibrium state could be assumed.

     

Growth and survival of juvenile red drum,Sciaenops ocellatus,acclimated to freshwater at three different stocking densities in a partial recirculation system

Preliminary technical baseline information for the inland culture of juvenile red drum, Sciaenops ocellatus, in a freshwater fish hatchery is presented. Three initial stocking densities (d₁ = 83, d₂ = 167, and d₃ = 250 fish/m³) were tested in a semirecirculation system for 575 days using a commercially available feed (48.1% protein, 25% lipids, and 0.13% fiber). Initial and final mean fish weight were 7.11 ± 0.02 g and 287.6 ± 27 g. As carrying capacity appeared to have been reached, only data from Days 1–333 were analyzed. One‐way ANOVA analyses indicated that the survival rate of the smaller density (d₁ =40 ± 3.7%) was significantly different from the other two densities (d₃ = 21 ± 1.1% and d₂ = 23 ± 1.0%), which did not differ between them. Absolute growth rate (0.87 ± 0.02 g/day) was not significantly different between densities (F = 0.23. p = .801). Neither was weight significantly different between treatments. There were significant differences in the feed conversion rate (FCR) between densities (F = 8.54; p = .02). FCR for d₁ was significantly lower than for the two other densities, which did not differ from each other. A von Bertalanffy growth model was adjusted (R² = 0.95), and weight–length relationship presented negative allometric values (b = 2.85, R² = 0.98).     

The future of genetic engineering to provide essential dietary nutrients and improve growth performance in aquaculture: Advantages and challenges

Advancements in gene technology in recent years have been driving the aquaculture industry forward. Improvements in growth performance, feed efficiency, and omega‐3 content are goals of the industry that could capitalize on applications of genetic engineering. One of the major challenges in the industry is to reduce the use of fish meal and oil, to improve the environmental and economic sustainability of aquaculture. The recent development of genetically engineered feed ingredients is one potential solution to the looming problem of fish meal and oil dependency. Furthermore, the development of transgenic fish has potential to improve production efficiency and other future desirable characteristics that relate to feed utilization and product quality. New gene technologies are beginning to revolutionize how we produce our food, and in aquaculture, will ultimately reduce pressure on wild fish stocks, help to preserve natural aquatic ecosystems, and improve nutritional profiles of farmed fish for human consumption. The purpose of this review is to provide an update on the current applications of genetic engineering technology to improve aquaculture through nutrition, including the development and use of transgenic feed ingredients, transgenic fish, and ultimately their impacts on nutrition, product quality, and consumers.     

Habitat associations of the Threatened pugnose minnow (Opsopoeodus emiliae) at the northern edge of the species range

Pugnose minnow (Opsopoeodus emiliae) is a small, reclusive species that is widespread in North America, but is one of the rarest fishes in Canada, found in less than 12 known localities in southwestern Ontario. In contrast to most pugnose minnow populations across the global range, Canadian populations are primarily found in turbid systems, potentially indicating persistence in suboptimal conditions. We used data from a multi-gear species and habitat survey in the Canard River, Ontario, a system dominated by agricultural inputs and the best-known capture site of the species in Canada, to parameterise multi-gear occupancy models for understanding the relationship between pugnose minnow occupancy and microhabitat features, including the role of turbidity. Almost 300 pugnose minnow were captured, representing the largest single collection of the species in Canadian history. The best occupancy model indicated that the probability of pugnose minnow occupancy was highest in the deepest sites with the lowest water clarity (i.e. high turbidity); however, competing models suggested that occupancy was highest at sites with wild celery (Vallisneria americana) and higher water clarity, signifying that habitats with low turbidity may be utilised if sufficient physical cover exists. Together, our results suggest that Canadian pugnose minnow populations occupy and potentially favour turbid conditions, possibly to avoid visual predators in clearer habitats. It remains uncertain whether this abiotic association represents a long-term, viable, local adaptation or whether persistence of pugnose minnow in the Canard River is at risk unless significant water quality improvements can be made.     

Partial nomadism in large‐bodied bream (Abramis brama)

The recent focus on a common movement ecology paradigm has increased awareness about the importance of distinguishing different movement patterns for understanding their specific impact on animal ecology and evolution. One specific form of movement is nomadism, where animals move between habitats in an arrhythmic fashion. Although not yet described in detail for freshwater fish, nomadism between lakes within drainage systems could affect local lake food webs in an otherwise unpredictable fashion. In this study, we used passive telemetry to describe inter‐lake movements of 1,280 individually tagged adult benthivorous bream (Abramis brama) over nine contiguous years in a drainage system with two paired lakes. The movements can best be described as partial nomadism, where a part of the population is neither resident nor migratory, but instead moves between lakes in a variable, arrhythmic fashion, often with long residency in one lake before moving to the other. We found extensive between‐year variation in the proportion and direction of bream moving, with higher movement propensity being partly associated with lower somatic condition. Notably, movements out of lakes were significantly more in direction of the neighbouring lake than away from the paired lakes, suggesting that at least direction was not random. Since bream are important ecosystem engineers, fluctuating densities of adult bream could affect ecological stability in lakes. Our study suggests that fish populations in interconnected lakes within drainages should not be treated as isolated units, and we discuss this in relation to lake ecology and the importance for lake ecosystem management.     

First evidence of spawning migration by goldfish (Carassius auratus); implications for control of a globally invasive species

Goldfish (Carassius auratus) was one of the first fishes to be domesticated and has been widely introduced across the globe, but is now considered one of the world's worst invasive aquatic species. Surprisingly, there is a dearth of information on its spatial and temporal movement patterns, which hampers the development of effective control programmes. We examined the movement patterns of an introduced population of C. auratus in a south‐western Australian river using passive acoustic telemetry. The study population had a high residency index within the array (i.e. proportion of all days at liberty that, on average, each fish was detected by a receiver) with fish being detected on 64% of days. The individuals were also reasonably mobile, travelling a mean of 0.30 km (linear river kilometres).day^‐1 within the array, and one fish moved 231.3 km over the 365‐day study period (including 5.4 km in a 24 hr period). Importantly, C. auratus displayed significant seasonal movement patterns including a clear shift in habitats during its breeding period with most mature individuals being detected in an off‐channel wetland during that time. The results of this study strongly suggest that C. auratus undertook a spawning migration into a lentic habitat. These results have important implications for developing control programmes for the species, such as targeting connections to off‐channel lentic systems during its breeding period.     

罗氏沼虾亲虾暴发性疾病病原的研究及防治

通过对上海一家水产养殖公司在１９９１￣１９９２年度发生的暴发性疾病的现场检测和病原分离,获得了Ｓ－１、Ｓ－２菌株。经人工感染试验对健康亲虾具有很强的致病力,出现与自然病虾相同的症状并在人工感染病虾上分离出同性状的菌株。证实了这二菌株是该病的致病菌。通过菌体形态,培养特性和生理生化反应,鉴定为莫格球拟酵母。通过药物筛选,配制出沼虾－１和沼虾－Ⅱ药饵,对预防及早期治疗效果良好。     

Genetic differentiation among Atlantic salmon reared in sea‐cages reveals a non‐random distribution of genetic material from a breeding programme to commercial production

Seven samples, each consisting of approximately 50 Atlantic salmon, were collected from five marine farms in Norway. These farms reported to rear fish originating from the same commercial breed; however, all samples followed a unique route of production from breeder to marine farm via egg, fry and smolt producers. A group of farmed escapees (n=50) were also captured. Following genotyping with 18 microsatellite loci, the global F_ST was 0.083, and pair‐wise values were as high as 0.158. Four clusters, with varying degrees of genetic differentiation, were identified among samples from the farms, and the source of the escapees was identified successfully. It is suggested that the genetic differences observed among samples from the farms were created through the process of genetic drift, facilitated by parallel sub‐strains, extensive within‐strain selection and low to moderate numbers of adults contributing to batches of eggs. In conclusion, this study has demonstrated that genetic identification of escaped Atlantic salmon, back to the farm of origin, may be possible even when farms rear fish reported to originate from a single breeder.     

微波消解-FAAS测定虾肉中钙的质量分数

采用微波消解-火焰原子吸收光谱法（flame atomic absorption spectrometry,FAAS）测定虾肉中钙（ca）元素的质量分数,对微波消解前处理的条件进行了研究。试验结果显示,最佳的微波消解体系为取样量0．500g,以硝酸（HNO,）作为消解溶剂,用量5．0mL,最适微波消解程序为多步消解程序D,包含3个步骤：1）功率400W,比例100％,升温5min,消解温度120℃,保持5min;2）功率800W,比例100％,升温5min,消解温度150℃,保持10min;3）功率800W,比例100％,升温10min,消解温度180℃,保持10min。样品消解液在常温或冷藏条件下保存48h之内的稳定性良好。经微波消解前处理后虾肉样品中”（ca）的相对标准偏差（relative standard deviation,RSD）为5．284％,加标回收率为91％-98％。微波消解-FAAS测定虾肉中的w（Ca）具有样品处理时间短、试剂用量少、结果准确和安全性高等优点。