Integration of duck and fish farming: Experimental results

In 1977 and 1978, two fish ponds at the Dor Aquaculture Experiment Station were integrated with duck production. Each pond's area was 400 m² and they were stocked with a polyculture of common carp, Tilapia, silver carp and grass carp (White Amur). The ducks were fed with prepared, nutritionally balanced feed, while the fish had to get by with the ducks' droppings plus the feed dropped directly from the ducks' beaks into the ponds. The ducks' performance on the ponds was superior to their ‘land’ control in growth rate, feed efficiency, viability and cleanness of feathers and skin. The average daily gain of the fish was 38.5 kg ha^?1, not significantly different from ponds receiving similar mixtures of dry poultry manure plus supplementary feeds.Our experimental results provide necessary empirical support to the conclusion that the system is very efficient and its use should be expanded in warm water aquaculture.     

Temperature Tolerance and Metabolic Depression of a Convict Child Under the Influence of Enhanced Ultraviolet-A (320–400 nm) Irradiation

The effect of an enhanced (5%) sub-lethal UVA irradiation on the total metabolism of a sub- tropical convict cichlid (Cichlasoma nigrofasciatum) is described. The specific oxygen consumption (vo₂) of related but differently treated populations was determined from 23 °C to 35 °C, to detect their tolerance limits toward environmental temperature. The experiments cover two generations (G1 and G2) of inbred derived populations. The fish were measured at different stages of development covering the period before and after maturation. The fish were grown at and adapted to 27–29 °C. The results showed that the population which was grown under an enhanced UVA irradiation since hatching (G2-UVA) had developed a general metabolic depression (MD) at all ranges of experimental temperature. The MD was especially expressed after the fish reached maturation. No MD was shown for the non-irradiated control populations (G2-control and G1-control) nor for the mature fish of G1-UVA. The G1-UVA population was grown under an enhanced UVA irradiation from 4 months of age. The vo₂ increased with increasing temperature, reaching a maximum at 31–33 °C for the G1- and G2-control populations. For the G1-UVA, a small peak of vo₂ was obtained at 29 °C reaching its maximum level at 33 °C. For the G2-UVA population, a maximum vo₂ was reached at 33 °C for the young and mature fish and at 29 °C during the maturation period. It can be concluded that the accumulation of UVA irradiation from early life was responsible for the MD in this fish. A wider temperature tolerance observed in the G2-UVA population might possibly be due to a reduction of total metabolic activity. The mechanisms underlying the MD observed in this fish are not yet known, but natural selection and adaptation processes might be involved.     

Estimates of nutrient discharge from striped catfish farming in the Mekong River,Vietnam, by using a 3D numerical model

A simulation was carried out by using a 3D numerical model for estimate the nutrient level discharged from striped catfish, Pangasianodon hypophthalmus intensively farming in the Mekong River, Vietnam. The simulated period was dry season from April 24, 2007, to April 27, 2007. Both dissolved and particulate forms of nutrients were simulated. A real status of water environment and scenario of discharge after applying fishpond effluent for irrigation of rice field were estimated in My Hoa Hung fish farm, An Giang Province. Simulated results were verified by observed data. Our results showed that nutrient levels at farming area in dry season were temporarily high and local. Applying waste water from the fishpond for irrigation of rice field could greatly reduce nutrients level in the fish farming area, the nutrient levels were 77 % for total nitrogen and 73 % for phosphorus. Therefore, recycling nutrient from fishpond effluent for irrigation of rice field illustrated an effective technology for pollution reduction which is a crucial issue to enable sustainable development of intensively farmed striped catfish.     

The fate of organic matter derived from small-scale fish cage aquaculture in coastal waters of Sulawesi and Sumatra, Indonesia

To determine the fate of organic matter derived from fish cage aquaculture, carbon and nutrient cycling processes in waters and sediments, and water circulation, were examined at two fish cage farms of different size and utilizing different food types, on Sulawesi and Sumatra islands, Indonesia. Mass balance models of C, N and P were constructed to assess the pathways of waste utilization and dispersal. At the smaller farm in Sulawesi (64.5 m² cage area; 3 t annual net production) using pelleted food, there was proportionally less waste (≈ 40% of total C input) than at the larger Sumatran farm (2432 m² cage area; 9 t annual net production) using trash fish (≈ 70% of total C input) as food. At the small farm, the mass balance and hydrographic models indicated a maximum dispersal area of 1180 m², equivalent to 18 times the farm area. Within this area, 30% of total organic matter input (farm waste + fixed phytoplankton carbon) was buried in sediments with 30% mineralized in the water-column and 40% mineralized in the seabed. At the larger Sumatran farm, the models indicated a maximum dispersal area of 29  220 m², roughly 12 times the farm area. Within this area, 30% of total organic matter input (farm waste + natural pelagic input) was buried in sediments with 50% mineralized in the water-column and 20% mineralized on the seabed. There was some evidence of benthic enrichment at both farms, mostly as enhanced dissolved nutrient release, but sulfate reduction accounted for < 25% of total C flux, and denitrification/ammonium oxidation accounted for only 4–17% of N lost from sediments. There was no clear evidence of impact with distance from the cages at either farm. Phytoplankton gross primary production accounted for 60–77% of the total organic input to the receiving environment, suggesting that the relative importance of fish cage wastes must be assessed against natural inputs of organic matter.     

Evaluations of rum distillation wastes,pharmaceutical wastes and chicken feed for rearing Tilapia aurea in Puerto Rico

Rum distillation wastes (solubles and yeast), pharmaceutical wastes (spent beer and spent beer plus solids), and a locally manufactured chicken feed were evaluated for their potential use in the culture of Tilapia aurea in Puerto Rico. The experimental products were compared to three types of controls: a commercial fish feed, an inorganic fertilizer, and an unmanaged system. The yield trials were conducted for 120 days in 9.3 m plastic pools. Three replications were made of each treatment. Survival of fish in the various treatments ranged from 80 to 96.7%. The highest mean standing crop at harvest (690 kg ha^?1 equivalent) resulted from the fish receiving the commercial fish feed. This was followed by the fish from the spent beer treatment (643 kg ha^?1 equivalent), inorganic fertilizer (559 kg ha^?1 equivalent), distiller's yeast (454 kg ha^?1 equivalent), spent beer plus solids (429 kg ha^?1 equivalent), chicken feed (413 kg ha^?1 equivalent), distiller's solubles (347 kg ha^?1 equivalent), and the unmanaged system (145 kg ha^?1 equivalent). The average feed conversion values for the fish fed the commercial fish feed and chicken feed were 1.53 and 2.06, respectively. Dissolved oxygen levels in pools treated with rum distiller's yeast declined from approximately 8.0 to 0.4 p.p.m. following initial application of the product. Dissolved oxygen depletions occurred after each subsequent application. All other systems had waters with dissolved oxygen concentrations generally suitable for fishculture.     

The effects of fish farm effluents on the water quality in the Åland archipelago, Baltic Sea

The main aim of this study was to increase our knowledge on how fish farm effluents influences the surface water quality in the Åland archipelago (Baltic Sea). A second aim was to conduct critical model tests of three models that predicts the impact of farm emitted phosphorus on total phosphorus (TP), chlorophyll and Secchi depth. Extensive field studies were conducted between 1997 and 1999 in nine defined coastal areas with, and four reference areas without, fish farms. According to our results the most significant effects on TP concentrations, periphytic growth and phytoplankton standing crop was observed in two coastal bays with small to moderate fish farm production (≈70 tonnes per year). The significant effects in each bay was mainly due to the small size of the bay (0.48 and 0.73 km²) and the shallow mean water depth (3 and 3.8 m), rather than long water retention times (2 and 6 days). Due to a very large fish farm production (800 tonnes per year), we also observed significant effects in a coastal area of moderate size (8 km²), which had a theoretical water retention time of about 8 days. No significant effects of fish farm effluents on the surface water quality were observed in the other six areas. Furthermore, our data shows that, besides the fish farm effluents, the import of nutrients from the surrounding sea and the sediment resuspension may have a decisive effect on the water quality in the studied areas. Finally, we can conclude that at least two of the tested models are useful in context of environmental management.     

Grey heron, Ardea cinerea L., predation at cage fish farms in Argyll, western Scotland

Abstract. The aims of the present study were to determine the number and age structure of grey herons, Ardea cinerea L., visiting a large freshwater cage trout farm in a study area in Argyll, western Scotland and to quantify heron predation at the site. Heron abundance was assessed on sea loch shores, running and standing freshwater bodies and at the trout farm between September 1985 and August 1987. Herons visited the farm almost exclusively at night or during twilight periods and, as a consequence, were seen more often by farm staff in winter than in summer. Herons selected cages containing small trout (<300g) and removed them from cages by standing on the top nets and fishing through the mesh. Stock losses were of two kinds; trout were either eaten directly or were dropped by herons during manipulation, when characteristic wounds increased susceptibility to disease or made the fish unmarketable. Adult herons were more successful at feeding than first-years and although younger birds spent more time feeding their intake rates remained lower than those of adults in terms of their total time at the farm. Within a cage, smaller fish aggregated closer to the surface than larger ones and so were more vulnerable to heron predation. In many cases, a high proportion of the fish attacked by herons were blind and/or in poor condition. By recording only wounded fish, farm staff considerably underestimated their losses to herons. Nevertheless, attacks sometimes appeared serious to farmers. However, such losses were small compared with other forms of fish mortality and loss.     

Salmon farming affects the fatty acid composition and taste of wild saithe Pollachius virens L.

There is an ongoing controversy on whether fish farming affects the quality of wild fish in fjords. In northern Norway, local people prefer not to eat saithe, Pollachius virens L., from areas in the vicinity of fish farms because they say the taste is inferior to saithe from other areas. To address this issue, saithe were collected in the vicinity of a salmon fish farm in a fjord in northern Norway and in two reference areas: one site 6 km away from the nearest fish farm in the same fjord, and the other in a fjord nearby with no fish farms. The objective of this study was to clarify whether the physiology or taste of saithe near fish farms differs from saithe in areas with no or limited influence from fish farms. The fish collected near farms were larger than those from control sites of the same age and had been eating pellets. Analysis of fatty acid composition of the fillet indicated that fish collected near the farms had fatty acid profiles that resembled that of pellets more than fish from reference sites. The results suggest that there were individual differences in the time spent near cages for saithe collected near the farm, and that saithe collected at the reference area in the same fjord had also been eating pellets, i.e. had visited at least one of the fish farms in the fjord. In a sensory test, the test panel found that saithe from the fjord without fish farms tasted better than saithe collected near the cages. The test panel found no clear differences in taste between saithe collected near the fish farm and saithe from the same fjord, but 6 km from the nearest fish farm.     

Evaluation of duckweed (Lemna gibba) as feed for tilapia (Oreochromis niloticus × O. aureus) in a recirculating unit

Hybrid Oreochromis niloticus × O. aureus were cultured at high densities in an experimental recirculating unit over a period of 89 days with duckweed (Lemna gibba) or a combination of duckweed and commercial pellets as feed. When fed duckweed alone, intake rate was low, feed conversion ratio good (1:1) and relative growth rate poor (0.67% of body mass d^?1). Sixty five percent of the duckweed consumed was assimilated and 26% converted to fish. When the fish were fed pellets in addition to duckweed the rate of duckweed consumption decreased and growth rate of the fish doubled with feed conversion ratios between 1.2 and 1.8. Seventy percent of the mixed diet was assimilated but only 21% converted. Fish grown on the mixed diet performed similarly to fish grown on pellets but had a better feed conversion ratio.     

金鸡湖渔业利用现状及增殖途径

金鸡湖养殖场以肥水养鱼而闻名,自８０年代开始单产已达１５０ｋｇ／１０００ｍ２以上,进入９０年代后,在养殖模式、经营管理上进行了调整和改进,现基本模式是平均每千平方米放２５．５ｋｇ、４５０尾左右,其中鲢、鳙占７５％,鲤、鲫、鳊等占２５％;平均单产１７４ｋｇ／１０００ｍ２,增肉倍数为６．８,其中鲢、鳙产量占６９％;利润率１００％;在捕捞、销售上实行常年捕捞、周年上市。     

Epidemiological observations of pancreas disease of farmed Atlantic salmon, Salmo salar L., in Ireland

Epidemiological investigations into the pancreas disease (PD) of farmed salmon were conducted on populations of Atlantic salmon reared in Ireland during 2003 and 2004. The investigations surveyed all marine salmon farms operating in Ireland through a detailed questionnaire with follow-up farm visits. Information was gathered on 21 populations of fish in 2003 and 14 populations in 2004. Thirteen of the 21 populations suffered PD in 2003 and 12 of the 14 in 2004. The mean mortality due to PD on affected farms was 18.8% in 2003 and 14.8% in 2004 and the loss of growth due to PD was estimated at 11.4% over the 2-year period. The highest risk periods for outbreaks of PD were early summer and early autumn and the farms most seriously affected by PD mortality were in the western counties of Ireland. Factors which showed an indication of association with a PD outbreak or high mortality during a PD outbreak were: livestock movement to another sea site, high feeding rate prior to any PD outbreak, the presence of another PD positive farm in the same water body, greater than 250000 fish on a site, a previous history of PD on a site, a high sea lice burden, and sites located in the western regions of Ireland which reared a specific strain of salmon.     

DNA fingerprinting: application to conservation of the CITES-listed dragon fish, Scleropages formosus (Osteoglossidae)

Since 1975,CITES has listed the dragon fish, Scleropages formosus, as anendangered species. In 1995, a captive-bred population was set upby a commercial fish farm with assistance from the PrimaryProduction Department in Singapore. Other farms in Indonesia andMalaysia followed suit. These populations have contributed to animmediate conservation of the species. Due to very high demandfor this ornamental fish, these venues may be its last sanctuary.DNA fingerprints of the dragon fish were obtained by different methods from the green, red and gold varieties grown in a Singapore fish farm to determine which method was most suitable in providing information on genetic variability. Because a DNA fingerprint is a pattern made up of DNA fragments that are resolved by electrophoresis, each individual has its own unique fingerprint due to a genetic make-up different from another individual. Thus, genetic variability was best studied by developing DNA fingerprints.Firstly, restriction fragment length polymorphisms (RFLPs) were obtained. DNA fragments formed by cleavage with nine restriction endonucleases used singly were hybridized individually to four non-radioactively labelled probes to give RFLPs. The RFLPs for each variety were similar and genomic DNA from each variety had many binding sites to the probes. This made differentiating RFLPs specific to individual varieties difficult. Secondly, random amplified polymorphic DNA (RAPD) fingerprints were developed. DNA fragments that were resolved on a denaturing polyacrylamide gel were hybridized to seven arbitrary primers used singly. RAPD fingerprints for each variety were different for each primer tested. The similarity index indicated low genetic variability between varieties. Lastly, DNA was screened for microsatellite loci which refer to short tandem repeats of two or three bases. The occurrence of other microsatellite loci, their chromosome location and frequency is being investigated while primers have been designed to detect more loci by the polymerase chain reaction. As this method provides undisputed and reproducible evidence of relatedness and stock identification, and can be applied for long-term management of domesticated populations through pedigree construction and evaluation of heterozygosity, it is the preferred choice to determine genetic variability     

Does marine fish farming affect local small‐scale fishery catches? A case study in the NW Mediterranean Sea

Fish farms have been shown to aggregate large numbers of wild fish in their surroundings. Although little is known about how this affects the local fishery, two hypotheses have been put forward; a trapping and a protecting effect on wild fish. This study provides the first monitoring of commercial and recreational fishing activity at a fish farm. We assessed the effect on the small‐scale fishery analysing the differences between fishing in farm proximity and away from the farm (in terms of catch rate, income and catch composition). Moreover, we estimated the biomass removal from fishing activities by farm employees inside the farm. The study was conducted from January 2011 to June 2012 at a Gilthead seabream farm in the NW Mediterranean. The findings revealed a relevant amount of commercial and recreational fishing effort in farm proximity. Yet, the results showed no benefit or difference of fishing in close proximity to the farm compared with areas away from the farm. Thus, we conclude that farm‐aggregated fish are protected from the commercial fleet by the farm leasehold area, but remain vulnerable to hidden fishing practices inside the farm, where farm employees harvest more than 4 t of wild fish annually.     

Growth of Tilapia nilotica in ponds with differing histories of organic fertilization

A series of six 0.04 ha ponds that had received varying rates of organic fertilization during 1976 and 1977 were each stocked with 200 Tilapia nilotica for a 3.5 month period during the 1978 growing season. Slotted feeding floors were placed over five of the six ponds and two growing-finishing hogs were placed on each feeding floor. The sixth pond received neither manure nor supplemental feed. Growth of T. nilotica was most rapid in ponds that had a history of relatively high manuring rates. Condition factors paralleled fish growth. Survival was 75% or more in each of the ponds with no apparent correlation between percent survival and history of manuring. Water quality was similar and acceptable for tilapia in each of the six ponds. The data indicated that a stocking rate of 50 hogs/ha can result in high fish yields; and that the history of a pond's experimental use influences subsequent experimental results.     

De novo synthesis of fatty acids in the rotifer, Brachionus plicatilis

The fatty acid composition of rotifer phospholipids is largely dependent on that of their food, indicating that the ingested lipids are hydrolysed in the gut, resorbed, metabolized and incorporated into body phospholipids. It is stable and does not change considerably after 1 or 2 days of starvation.Considerable differences were found in the fatty acid composition of rotifers fed baker's yeast (Saccharomyces cerevisiae), Chlorella or Isochrysis. Rotifers fed on baker's yeast for several generations contained considerable amounts of PUFA (1.6% of 22:6 ω3) although this yeast contains mainly 16:1 and 18:1 acids and is completely devoid of 16:3, C:20 and C:22 unsaturated and saturated fatty acids. This observation suggests that fatty acid synthesis and elongation had occurred. De novo synthesis of PUFA was further suggested by experiments in which 1-¹⁴C acetate was incorporated into radioactive acids and was verified by chemical degradation. Upon decarboxylation, approximately 10% of the total radioactivity in the PUFA was recovered as ¹⁴CO₂, indicating that all the uneven C-atoms must contain ¹⁴C. Oxidative cleavage of all of the double bonds of PUFA yielded ¹⁴C-labelled propionic and hexanoic acid from the methyl end of the molecule. However, the rate of synthesis of these acids is rather low. Hence, in order to supply large amounts of PUFA to marine fish larvae, rotifers must be fed on PUFA-rich food.     

Cage culture of sutchi catfish, Pangasius sutchi (Fowler 1937): effects of stocking density on growth, survival, yield and farm profitability

The sutchi catfish, Pangasius sutchi (Fowler 1937) was grown at 10 stocking densities in cages suspended in a river‐fed channel during the summer of 2000. Catfish fingerlings (mean length 9.1–9.7 cm and mean weight 5.9–6.7 g) were stocked at densities of 60, 70, 80, 90, 100, 110, 120, 130, 140 and 150 fish m^?3. After 150 days, growth and yield parameters were studied and a simple economic analysis was carried out to calculate profitability. The mean gross yield ranged from 15.6±0.27 to 34.5±0.44 kg m^?3 and the net yield ranged from 15.2±0.22 to 33.5±0.36 kg m^?3 and showed significant variations (P<0.05). The mean weights of fish at harvest were inversely related to stocking density. Both gross and net yields were significantly different and were directly influenced by stocking density but the specific growth rate, survival rate and feed conversion rate were unaffected. Higher stocking density resulted in higher yield per unit of production cost and lower cost per unit of yield. The net revenue increased positively with increasing stocking density. A density of 150 fish m^?3 produced the best production and farm economics among the densities tested in this experiment.     

Homing of coho salmon (Oncorhynchus kisutch) exposed to morpholine

Smolts of coho salmon (Oncorhynchus kisutch) were exposed to 5 × 10^?5 mg·l^?1 morpholine for 15 days and released into the Salmon River along with an unexposed control group. During the following two autumns, morpholine was introduced into the hatchery's fish ladder on various days and the return of experimental fish was recorded. The returns of morpholine-exposed and control fish were not statistically different. With morpholine present in the fish ladder, control fish were not repelled, and with morpholine absent from the ladder, morpholine-exposed fish returned as readily as control fish.     

Distribution,abundance and growth of juvenile salmonids off the coast of Oregon and Washington,summer (1980)

Juvenile salmonids (< 50 cm) were sampled by purse seine off the Pacific coast from Tillamook Bay, Oregon, to Copalis Head, Washington, during the period May through September (1980). Temporal distribution and abundance of the major Columbia River species were determined. Spring chinook salmon (Oncorhynchus tshatuytscha) and steel head (Salmo gairdneri) were present only during early cruises and were distributed almost entirely in the Columbia River plume and the sample area to the north. Coho salmon (O. kisutch) and fall chinook salmon were distributed more uniformly throughout the sampling area and were relatively abundant throughout the sampling period. Concentrations of fish were found only within 28 km of the shore. A number of fish that had been marked before or during their outmigration from the Columbia River system were recaptured. It appeared possible that with concentrated sampling in areas with high fish abundances, sufficient numbers of marked juvenile salmonids could be captured to provide relative survival estimates between different stocks of Columbia River fish.     

Observations on the use of Furanace for the control of vibrio disease in marine flatfish

Minimum inhibition concentrations (MICs) were determined for Furanace (Dainippon Pharmaceutical Co. Ltd.) against 17 strains of pathogenic vibrios isolated from marine fish and salmonidae. All the strains tested were sensitive to Furanace, the highest MIC being 3.1 μg/ml for one strain and the remainder being < 1.6 μg/ml. Plaice (Pleuronectes platessa L.), Dover sole (Solea solea (L.)) and brill (Scophthalmus rhombus (L.)) rapidly took up Furanace from low-concentration baths (5–10 μg/ml) at 9.5–11.5°C. Uptake varied between species at these temperatures and in most cases blood levels above 1 μg/ml were achieved after 1 hour's exposure. Two hours after exposure over 70% of the Furanace had been eliminated from the blood.