Common carp (Cyprinus carpio L.) alters its feeding niche in response to changing food resources: direct observations in simulated ponds

We used customized fish tanks as model fish ponds to observe grazing, swimming, and conspecific social behavior of common carp (Cyprinus carpio) under variable food-resource conditions to assess alterations in feeding niche. Different food and feeding situations were created by using only pond water or pond water plus pond bottom sediment or pond water plus pond bottom sediment and artificial feeding. All tanks were fertilized twice, prior to stocking and 2 weeks later after starting the experiment to stimulate natural food production. Common carp preferred artificial feed over benthic macroinvertebrates, followed by zooplankton. Common carp did not prefer any group of phytoplankton in any treatment. Common carp was mainly benthic in habitat choice, feeding on benthic macroinvertebrates when only plankton and benthic macroinvertebrates were available in the system. In the absence of benthic macroinvertebrates, their feeding niche shifted from near the bottom of the tanks to the water column where they spent 85% of the total time and fed principally on zooplankton. Common carp readily switched to artificial feed when available, which led to better growth. Common carp preferred to graze individually. Behavioral observations of common carp in tanks yielded new information that assists our understanding of their ecological niche. This knowledge could be potentially used to further the development of common carp aquaculture

Stress Relaxation Measurement of Fibroblast Cells with Atomic Force Microscopy

We measured the stress relaxation of mouse fibroblast NIH3T3 cells with an atomic force microscope (AFM) using a sharp silicon tip and a silica bead with a radius of ∼1 µm as an indenter. The decay of loading force was clearly observed in NIH3T3 cells at a small initial loading force of ∼0.4 nN and was well fitted to the stretched exponential function rather than to a single exponential function. The stretching exponent parameter was ∼0.5 for both indenters, indicating that the stress relaxation observed in NIH3T3 cells consisted of multiple relaxation processes. The time-domain AFM technique described in this report allows us to measure directly the relaxation process of living cells in a range from milliseconds to seconds

Effective method to culture infusoria, a highly potential starter feed for marine finfish larvae

This study was conducted to detect suitable protozoan species of infusoria as starter diet for early stage of marine finfish larvae. Infusoria were cultured using vegetables (Brassica pekinensis and Brassica chinensis) and dry fish meal with 30 ppt, 15 ppt saline water and freshwater in 40 liter aquaria. In the 30 and 15 ppt aquaria, Euplotes sp. was the dominant species and cell sizes were 60–80 μm. The densities of Euplotes sp. were 400–500 individuals/ml in the 30 ppt aquaria and 800-1300 individuals/ml in the 15 ppt aquaria. In both conditions, the high densities were maintained for 13 days. The densities of protozoa in saline water were higher in 15 ppt than in 30 ppt aquaria. The densities of protozoa cultured by our method was enough amount for early stage larvae of groupers and snappers. Therefore, this method is suitable for protozoa culture in small scale hatcheries

Land-based poly-eco-aquaculture of abalone and seaweed in a small scale recirculating system using a recycled freezer container

To minimize environmental problems associated with aquaculture, we wanted to develop an abalone and seaweed polyculture approach in a small scale recirculating aquaculture system housed in an air-conditioned recycled freezer container. We conducted two experiments; each used two recirculating systems. Each system consisted of two biofilters and two abalone culture tanks. Each abalone culture tank contained three plastic baskets for abalone. In the first experiment one of the systems also incorporated a protein skimmer (PS) to evaluate its effects on water quality and abalone growth. In the second experiment, the same system was incorporated with both a PS and a seaweed culture tank (PSS) to evaluate their combined effects on water quality and abalone growth. The abalone stocking density was 20 individuals (average weight 5.3-0.08 g and 8.7-1.9 g in the first and second experiment) per basket. Pelleted artificial feed was supplied six days per week at 2.3% of abalone body weight per day. The pH, dissolved oxygen (DO), total inorganic nitrogen (TIN), total inorganic phosphorus (TIP), and bacterial abundance were monitored daily. The duration of first and second experiments were 87 and 70 days. DO concentration was significantly higher in the system with the PS. An opposite trend was observed in TIN concentration and bacterial abundance. PS had no effect on pH or TIP. PSS influenced water quality parameters and bacterial abundance similar to PS except TIP, which was greater in the system with PSS than without. Treatment effects on growth, feed consumption, and FCR were similar in both experiments. Abalone consumed less feed and had significantly higher FCR and lower growth rates in the control. However, feed consumption, FCR and growth rate of abalone were comparatively better in the PSS system than in the PS system. The PSS system was not only better for abalone growth, but also produced an additional crop in the form of seaweed. The system did not discharge waste. Therefore, future abalone culture systems can be focused on this model. However, more research is necessary before extrapolating results to an industrial level

Effects of protein skimming on water quality, bacterial abundance and abalone growth in land based recirculating aquaculture systems

Recirculating aquaculture systems can reduce many challenges associated with open culture systems but maintaining suitable water quality in recirculating system is difficult. Protein skimmer removes organic matter from the water before it breaks down into nitrogenous waste. Therefore, the aim of this study was to evaluate the effects of protein skimming on water quality, bacterial abundance and abalone growth in recirculating aquaculture system. Two recirculating systems utilizing artificial seawater were housed in an air-conditioned, insulated recycle frozen container (4.3×1.9×1.9 m) to maintain optimum water temperature (19.2 0.80C) for abalone growth. Each system consisted of two biofilters (100 and 200 L) and two abalone culture tanks (each 200 L) containing three plastic baskets (each 50 × 34 × 6 cm, with 12 mm mesh). One culture system incorporated a protein skimmer. Over an experimental period of 87 days, protein skimming resulted in significantly better water quality, heterotrophic bacterial abundance and abalone growth. Results indicate recirculating abalone culture systems with protein skimmer housed in an air-conditioned, insulated recycle frozen container may provide a viable alternative to current land-based, flow-through systems. More research is needed to further increase the efficiency of this system

A simple and effective method to culture ciliated protozoans as a starter diet for marine finfish larvae

Infusoria play an important role in microbial food chains. Infusoria are the microscopic single celled animalcules belonging to Class, Ciliata and Phylum, Protozoa. They are smaller in size than SS rotifers, soft bodied and highly nutritious, making them an ideal starter diet for early stage fish larvae. In tropical regions, grouper and snapper species are cultured in fish farms. Infusoria will be suitable live feed for these fish larvae, how-ever there are a limited number of studies about infusoria culture method. This study was conducted to determine optimum salinity to culture infusoria. In this study, infuso-ria were cultured following Kitani’s (1989) method. Fish meal was made by small dried anchovies (TL 40–60 mm) by a general food processor. Vegetables (Chinese cab-bage) were cut into small pieces (1–2 cm). Fish meal (0.025%/water volume) and vege-tables (0.5%/water volume) were put into 0, 10, 15, 20, 25 and 30 ppt fresh and saline water in 3 liter aquaria. Many types of infusoria were observed in fresh water group. Less number species of infusoria were observed in saline water groups. The density of infusoria in saline water showed no significant difference among different salinities. In the saline water groups, Euplotes sp. with the size of 60-80 μm was observed, and this species would be good candidate as live feed for marine finfish larvae

Landbased poly-eco-aquaculture of abalone and seaweed in the small scale recirculating system using the recycled frozen container

To minimize environmental problems associated with aquaculture, we wanted to develop an abalone and seaweed polyculture approach in a small scale recirculating aquaculture system housed in an air-conditioned recycled freezer container. We conducted two experiments; each used two recirculating systems. Each system consisted of two biofilters and two abalone culture tanks. Each abalone culture tank contained three plastic baskets for abalone. In the first experiment one of the systems also incorporated a protein skimmer (PS) to evaluate its effects on water quality and abalone growth. In the second experiment, the same system was incorporated with both a PS and a seaweed culture tank (PSS) to evaluate their combined effects on water quality and abalone growth. The abalone stocking density was 20 individuals (average weight 5.3-0.08 g and 8.7-1.9 g in the first and second experiment) per basket. Pelleted artificial feed was supplied six days per week at 2.3% of abalone body weight per day. The pH, dissolved oxygen (DO), total inorganic nitrogen (TIN), total inorganic phosphorus (TIP), and bacterial abundance were monitored daily. The duration of first and second experiments were 87 and 70 days. DO concentration was significantly higher in the system with the PS. An opposite trend was observed in TIN concentration and bacterial abundance. PS had no effect on pH or TIP. PSS influenced water quality parameters and bacterial abundance similar to PS except TIP, which was greater in the system with PSS than without. Treatment effects on growth, feed consumption, and FCR were similar in both experiments. Abalone consumed less feed and had significantly higher FCR and lower growth rates in the control. However, feed consumption, FCR and growth rate of abalone were comparatively better in the PSS system than in the PS system. The PSS system was not only better for abalone growth, but also produced an additional crop in the form of seaweed. The system did not discharge waste. Therefore, future abalone culture systems can be focused on this model. However, more research is necessary before extrapolating results to an industrial level