Rearing fish

The nature of the conditions of intensive production, however, can increase the risk of diseases and infections which can spread very rapidly and devastate large numbers of animals." Thus it is common practice for producers of poultry to add coccidiostats to their diets and vaccines to their drinking water in order to prevent coccidiosis and other infectious diseases such as bronchitis and Newcastle disease. A similar problem exists for intensively reared fish, where it is necessary to add antibiotics to their diets. A problem with intensively reared fish is that their diet is added directly into the water in which they live thus drugs and other additives in the diet are relatively easily dispersed into the local environment of fish farms, where they can increase bacterial resistance and also cause problems such as algal blooms. 

Felton, S.P., W. Ji, and S.B. Mathews. 1990. Selenium concentrations in coho salmon outmigrant smolts and returning adults a comparison of wild versus hatchery-reared fish. Dis. Aquat. Organ. 9 157-161. 

Brown, G, E, and Smith, R. J. F., 1998, Acquired predator recognition in juvenile rainbow trout (Oneor-Aync/nts mykiss). conditioning hatchery- reared fish to recognize chemical cues of a predator. Can. J. Fish. Aquat. S c . 55 611-617. 

During these tracking studies we collected water samples from different stratified layers within the water column. These samples were then used to stimulate the olfactory epithelium of hatchery-reared fish while we measured electrical activity from single olfactory bulb neurons. Ninety per cent of the responding neurons, presumably mitral cells, showed differential responses to the water samples (Figure 3) demonstrating the capacity of the olfactory system to discriminate among stratified water layers found in the ocean. 

A more realistic approach is provided by experiments that collect developing eggs or larvae in one stream and transplant them to another or release hatchery reared fishes in nonnative streams (review by Ricker 1972). These transplant experiments have demonstrated that nonnative fishes are able to return to the stream from which they were released, suggesting that the fish are somehow remembering something about the stream as they leave it, and that these remembered cues allow them to return as adults. Further work has shown that this imprinting takes place within a very short time period during the transition... 

GiRAUD E, BLANC G, Bouju-ALBERT A, WEILL F-x and DONNAY-MORENO c (2004), Mechanisms of quinolone resistance and clonal relationship among Aeromonas salmoni-cida strains isolated from reared fish with furunculosis , / Med Microbiol, 53, 895-901. 

Fishes in the family Salmonidae (trout and salmon) are in high demand, with the interest in salmon being greatest in developed nations. Salmon, mostiy Atiantic salmon, are produced in Canada, Chile, Norway, New Zealand, Scotiand, and the United States. Fishes in the family Cichhdae which includes several cultured species of tilapia, are reared primarily in the tropics, but have been widely introduced throughout both the developed and developing world. 

Salmon, steelhead trout, and a variety of marine fishes are currentiy being reared in net-pens (Fig. 5). The typical salmon net-pen is several meters on each side and may be as much as 10 m deep (1). Smaller units, called cages, are sometimes used by freshwater culturists. Cages tend to have volumes of no more than a few cubic meters. 

Fig. 5. Marine net-pens such as the ones shown here in Puget Sound, Washington (U.S.), are used for the rearing of salmon by commercial fish farmers.

In cases where zooplankton are reared as a food for predatory larvae or fry, it may be necessary to maintain three cultures. Though wild zooplankton have been used successfully in some instances (eg, in Norway wild zooplankton have been collected and fed to larval Pacific haUbut), the normal process involves culturing algae to feed to zooplankton that are fed to a young shrimp or fish. 

BCF factors in fish ranging from 1.08 to 1.85, indicating that bioconcentration of methyl parathion is not an important fate process (Crossland and Bennett 1984). In another study, methyl parathion was added to the water of a carp-rearing pond and the concentration of methyl parathion was measured in water, soil, macrophytes, and carp over a 35-day period. Results showed that methyl parathion accumulated in macrophytes for 1 day and in carp for 3 days following exposure, and then dissipated. The concentrations of methyl parathion decreased in macrophytes by 94% by day 35 and by 98% in carp tissue by day 28 (Sabharwal and Belsare 1986). These data indicate the potential for biomagnification in the food chain is likely to be low because methyl parathion appears to be metabolized in aquatic organisms. 

Ogata, M., Miyake, Y. (1978) Disappearance of aromatic hydrocarbons and organic sulfur compounds from fish flesh reared in crude oil suspension. Water Res. 12, 1041-1044. 

Ringo, E. 1993. The effect of chromic oxide (Cr203) on faecal lipid and intestinal microflora of seawater-reared Arctic charr, Salvelinus alpinus (L.). Aquacult. Fish. Manage. 24 341-344. 

A peculiarity of thiamine is that the vitamin can easily become inactivated. An early instance was seen in 1941 when commercially reared mink became paralyzed (Chastek paralysis), a disorder which could be cured by giving the animals thiamine. The problem was traced to their having been fed fish that had partially decomposed. Later work showed that in decayed fish a microbial enzyme had been released, thiaminase, which destroyed the thiamine normally present in the food. A rather different process occurs when horses or cows are allowed to graze on bracken. This contains a protein which binds to thiamine, so reducing its availability. Once again the condition can be treated by administering the vitamin. 

The apparatus was separated into two compartments(A,B) with a silicone rubber sponge sheet which had a hole in the middle to hold fish at just the back of pectoral fin. Both the head and rear parts of fish were covered with two small boxes which had many holes and were fixed to a cover plate of the apparatus. PCP-free water was supplied into the head compartment(A) at a flow rate of 1 liter/h and the overflow from (A) was reserved in an ice-cooled tank for the analysis of PCP excreted from gills. Fish urine was led by a cannula to an ice-cooled flask through... 

Even fish may mark their substrate. Juvenile Atlantic salmon (parr) are attracted to extracts from gravel over which salmon parr had been reared. They... 

In order to study the uptake and the metabolic fate of mephosfolan in fish reared in the rice paddy environment, fifteen Carasslus auratus (goldfish), a member of the carp family were introduced to mephosfolan-treated rice paddy tanks one week after the pesticide treatment. Fish were analyzed at periodic intervals. The radioactive residue levels found at various time intervals in the fish kept in the C-mephosfolan-treated rice paddy environment are presented in Table VII. All fish survived during the course of this study. The predominant metabolite in fish tissue was identified as thiocyanate ion. With this data and the data obtained from paddy water analyses, it is appropriate to evaluate... 

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