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1.
This study investigated: 1) susceptibility differences to infection by Neobenedenia girellae (Capsalidae) between amberjack Seriola dumerili (Carangidae), yellowtail S. quinqueradiata and Japanese flounder Paralichthys olivaceus (Paralichthyidae); 2) growth and egg production of N. girellae on each fish species; 3) acquired protection of each fish species against this parasite. The number of N. girellae on S. dumerili was significantly higher than on S. quinqueradiata and P. olivaceus when these fishes were exposed to oncomiracidia in the same aquarium. Neobenedenia girellae growth on S. dumerili was fastest and, thus the number of eggs laid by parasites on S. dumerili was greater than on the other two species. Seriola dumerili and P. olivaceus, which were previously infected with N. girellae and treated by freshwater bath, acquired partial protection against re-infection by N. girellae. The relative re-infection of three S. dumerili individuals out of eleven individuals was markedly low compared with the initial infection, and the relative initial infection and re-infection on two P. olivaceus out of eleven individuals was markedly low. The results of this study could be useful to control N. girellae infections when cultivating S. dumerili, S. quinqueradiata and P. olivaceus.  相似文献   

2.
Infections by the gill fluke Zeuxapta seriolae are a serious concern for sea cage aquaculture of kingfish, Seriola lalandi. The present study aimed to determine the pathophysiological effects of a progressive infection with Z. seriolae and the effects of treatment with hydrogen peroxide. For the progression of infection study, infected fish were taken from a sea cage farm, treated to remove parasites and then infected by cohabitation with heavily infected fish. Samples were taken at 2-week intervals for 8 weeks. Infection intensity peaked at 4 weeks post-infection (mean intensity 565.9) and the number of mature worms (2 mm fixed length or larger) peaked at 6 weeks post-infection. Attachment of Z. seriolae appeared to cause little localized pathology; however, the occurrence of hyperplastic lamellae increased as the infection progressed. Haemoglobin concentrations were negatively correlated with Z. seriolae intensity and were lower than controls at 4 weeks (35.8% decrease) and 6 weeks (57.4% decrease) post-infection. Blood lactate concentration and plasma osmolality increased throughout the course of infection. For the effect of treatment experiment, groups of infected and non-infected fish were sampled either before or after treatment with hydrogen peroxide. Treated fish from both infected and uninfected groups had increased plasma lactate, osmolality and pH compared with pre-treatment groups. Treatment with hydrogen peroxide appeared to have acute effects on fish health but the magnitude (e.g. lactate, osmolality) and extent of the effects (e.g. haemoglobin) was much less than that caused by chronic infection with Z. seriolae.  相似文献   

3.
Juvenile fluted giant clams, Tridacna squamosa (mean shell length (SL) 15.7 ± 1.9 mm, mean total wet weight (TWW) 0.3 ± 0.1 g), were cultured for 4 months in land-based nursery tanks under four shade regimes (0, 10, 55 and 80 % shade). After 4 months, there were no significant differences in survival which ranged from 98.8 ± 0.1 % in juveniles cultured under 55 % shade to 100.0 ± 0.0 % in the other treatments. The SL of unshaded juveniles was only significantly greater than that of juveniles shaded 55 and 80 %. However, the TWW of juveniles cultured with no shade was significantly greater than that of the juveniles from all other treatments. The mean growth rate of juveniles varied from 5.0 mm month?1 for juveniles shaded 80 % to 6.9 mm month?1 for juveniles not shaded. There was no significant difference in mean growth rate of unshaded juveniles and juveniles shaded 10 %, but only the growth rate of juveniles cultured unshaded was significantly greater than that of juveniles shaded 55 and 80 %. The organic tissue content of juveniles cultured either unshaded or shaded 55 % was significantly higher than that of juveniles shaded 80 %. In contrast, the condition index (CI) of juveniles shaded 80 % was significantly higher than the CI of juveniles cultured either unshaded or shaded 55 %. However, there was no significant difference between the CI of juveniles shaded 80 and 10 %. Growth rate of juveniles was significantly correlated with temperature, dissolved oxygen content and flow rate of seawater. While low degrees of shade increase the growth rate of juvenile T. squamosa, they also negatively affect tissue condition. A shade level of 10 % appears to be optimal as it maximises growth and maintains a high CI.  相似文献   

4.
Experiments were conducted to control reproduction of Tilapia nilotica using cage culture compared with growth and reproduction in ponds. Three rearing densities (5, 15, and 45 fish per cage), and three kinds of aquatic plant (Hydrilla sp., Lemna sp., and Chara sp.) were used as feed.Results of the study showed that Tilapia reproduced in both cages and ponds; however, the intensity of reproduction was low. Growth rates of fish reared in cages were higher than those of fish reared in ponds.Lemna sp. as feed gave the best results in terms of growth rate and protein content of fish flesh. There was no interaction between feed and rearing density.  相似文献   

5.
To evaluate the effect of inexpensive cages made from concrete and bamboo on the skeletal extension rates of the scleractinian corals Acropora gomezi and Pavona cactus, fragments were cultured without cages, inside partial cages, and inside full cages with bamboo covers of two mesh sizes at different depths around Sambangan Island, Indonesia. An additional experiment was designed to assess the impact of shading by cages on skeletal extension. Linear extension rates of all fragments were measured over a period of four months. Culture inside cages led to significantly reduced extension rates of A. gomezi at both depths, while P. cactus only showed significantly reduced extension rates when cultured in full cages at greater depth. Caging lead to a significant increase in skeletal damage at both depths in A. gomezi, and at shallow depth in P. cactus. Shaded fragments of A. gomezi had much smaller extension rates (5 ± 1 mm/132 days, mean ± SE) than unshaded fragments (24 ± 1 mm/132 days) and sustained significantly more damage, while shaded fragments of P. cactus grew significantly better (15 ± 0 mm/132 days) than unshaded fragments (12 ± 0 mm/132 days) and sustained less damage, although the difference was not significant. The culture of coral fragments without cages may yield the best results. However, the choice of the optimal culture method will depend on the species to be cultured and the conditions encountered in the reef.  相似文献   

6.
A two‐factor experiment was performed to evaluate the effects of cage colour (black or white 0.5 m3 experiment cages) and light environment (natural sunlight or reduced level of natural sunlight) on the skin colour of darkened Australian snapper. Each treatment was replicated four times and each replicate cage was stocked with five snapper (mean weight=351 g). Snapper exposed to natural sunlight were held in experimental cages located in outdoor tanks. An approximately 70% reduction in natural sunlight (measured as PAR) was established by holding snapper in experimental cages that were housed inside a ‘shade‐house’ enclosure. The skin colour of anaesthetized fish was measured at stocking and after a 2‐, 7‐ and 14‐day exposure using a digital chroma‐meter (Minolta CR‐10) that quantified skin colour according to the L*a*b* colour space. At the conclusion of the experiment, fish were killed in salt water ice slurry and post‐mortem skin colour was quantified after 0.75, 6 and 22 h respectively. In addition to these trials, an ad hoc market appraisal of chilled snapper (mean weight=409 g) that had been held in either white or in black cages was conducted at two local fish markets. Irrespective of the sampling time, skin lightness (L*) was significantly affected by cage colour (P<0.05), with fish in white cages having much higher L* values (L*≈64) than fish held in black cages (L*≈49). However, the value of L* was not significantly affected by the light environment or the interaction between cage colour and the light environment. In general, the L* values of anaesthetized snapper were sustained post mortem, but there were linear reductions in the a* (red) and b* (yellow) skin colour values of chilled snapper over time. According to the commercial buyers interviewed, chilled snapper that had been reared for a short period of time in white cages could demand a premium of 10–50% above the prices paid for similar‐sized snapper reared in black cages. Our results demonstrate that short‐term use of white cages can reduce the dark skin colour of farmed snapper, potentially improving the profitability of snapper farming.  相似文献   

7.
Previous investigations into the environmental impacts at a shallow-water oligotrophic marine experimental cage aquaculture site in Western Australia have found no accumulation of organic material, and limited changes in macrofaunal communities. It was hypothesised that wild fish populations in the area consumed particulate wastes emanating from the cage, thus reducing the benthic impacts. An experiment was designed to quantify the accumulation of organic material on the seabed occurring in the presence and absence of wild fauna. Three treatments were arranged in duplicate, cages without exclusion nets (normal situation) (CAGE-FISH); cages surrounded by a 35-mm mesh exclusion net (preventing wild fish access to the sea bed and water column near the cage) (CAGE-FISH-EXCL); and empty cages surrounded by exclusion nets (to control for effects from the exclusion net) (CAGE-EXCL). In addition, four reference sites without cages (REF) were sampled. Following baseline sampling, rainbow trout (Oncorhynchus mykiss) were stocked into the CAGE-FISH and the CAGE-FISH-EXCL treatments at an initial stocking density of 2.4 kg m−3. The experiment was terminated after 62 days, at a final stock density of 5.6 kg m−3. Sampling found significantly greater accumulation of nutrients and fine sediments under the cages enclosed in the exclusion net than in other treatments and sites. Levels of organic carbon deposition at cages with exclusion nets was found to be 4.5±1.0 g C m−2 day−1 (mean±S.E.) compared to 0.7 to 1.1 g C m−2 day−1 at control and reference sites.The accumulation of nutrients at the CAGE-FISH-EXCL sites was correlated to distinct changes in macrofaunal community composition, with a sharp increase in overall macrofaunal abundance and a growing dominance of capitellid polychaetes. Based on a comparison between sedimentation rates within and outside excluded areas, the proportions of the total sedimenting nutrients consumed by wild fish were calculated to be 40% to 60%. It was concluded that in the natural coastal system of Western Australia or comparable environments, wild fish are potential important consumers of cage aquaculture waste materials. The fact that sediment C, N and P did not increase below cages with fish and no exclusion nets suggests that the benthic fauna, including surface grazing fish, at these sites were able to assimilate much of the remaining total sedimentary nutrients.  相似文献   

8.
Three 2‐factor experiments were conducted to determine the effects of background colour and synthetic carotenoids on the skin colour of Australian snapper Pagrus auratus. Initially, we evaluated the effects on skin colour of supplementing diets for 50 days with 60 mg kg?1 of either astaxanthin (LP; Lucantin® Pink), canthaxanthin (LR; Lucantin® Red), apocarotenoic acid ethyl ester (LY; Lucantin® Yellow), selected combinations of the above or no carotenoids and holding snapper (mean weight=88 g) in either white or black cages. In a second experiment, all snapper (mean weight=142 g) from Experiment 1 were transferred from black to white, or white to white cages to measure the short‐term effects of cage colour on skin L*, a* and b* colour values. Skin colour was measured after 7 and 14 days, and total carotenoid concentrations were determined after 14 days. Cage colour was the dominant factor affecting the skin lightness of snapper with fish from white cages much lighter than fish from black cages. Diets containing astaxanthin conferred greatest skin pigmentation and there were no differences in redness (a*) and yellowness (b*) values between snapper fed 30 or 60 mg astaxanthin kg?1. Snapper fed astaxanthin in white cages displayed greater skin yellowness than those in black cages. Transferring snapper from black to white cages increased skin lightness but was not as effective as growing snapper in white cages for the entire duration. Snapper fed astaxanthin diets and transferred from black to white cages were less yellow than those transferred from white to white cages despite the improvement in skin lightness (L*), and the total carotenoid concentration of the skin of fish fed astaxanthin diets was lower in white cages. Diets containing canthaxanthin led to a low level of deposition in the skin while apocarotenoic acid ethyl ester did not alter total skin carotenoid content or skin colour values in snapper. In a third experiment, we examined the effects of dietary astaxanthin (diets had 60 mg astaxanthin kg?1 or no added carotenoids) and cage colour (black, white, red or blue) on skin colour of snapper (mean weight=88 g) after 50 days. Snapper fed the astaxanthin diet were more yellow when held in red or white cages compared with fish held in black or blue cages despite similar feed intake and growth. The skin lightness (L* values) was correlated with cage L* values, with the lightest fish obtained from white cages. The results of this study suggest that snapper should be fed 30 mg astaxanthin kg?1 in white cages for 50 days to increase lightness and the red colouration prized in Australian markets.  相似文献   

9.
Sarafin (sarafloxacin hydrochloride), a new antibacterial, was evaluated in the field on a naturally induced infection of Edwardsiella ictaluri in channel catfish, -Ictalurus punctatus. Healthy channel catfish (mean weight = 50 g) were stocked into nine cages at 200 fish per cage in a pond with an undergoing E. ictaluri infection. Seven days after stocking, dead fish were observed in the cages with clinical signs of enteric septicemia of channel catfish (ESC). After E. ictaluri was confirmed through isolative biochemical tests, medicated feed was applied for five consecutive days. During this period, fish in three control cages received a commercial 32% protein floating feed, three other cages of fish served as positive controls and were fed Romet, and three cages received the test feed with Sarafin. Both medicated feeds reduced the increase in cumulative percent mortality. In the control cages, cumulative percent mortalities continued to increase throughout the study period. Average daily mortality rates were significantly lower following both treatments of medicated feed, and treatments receiving Sarafin showed the greatest reduction in average daily mortality rates. Average daily mortality rates in the control did not change after the medicated feeding period. Toward the end of the study, temperatures reached 30°C, above the active range of ESC infections, and all mortalities ceased.  相似文献   

10.
The effects of water flow, fish feed and cage position on net biofouling was examined in a floating cage fish farm. Fouling of 16 mm mesh net panels suspended inside and outside net cages and exposed to different treatments were monitored weekly until net apertures were completely occluded by the fouling organisms (8 weeks). Results indicate a dramatic reduction in water flow velocity throughout the fish farm due to the cage units themselves and net biofouling. The reduced water flow (<10 cm s?1) inside net cages promoted rapid net biofouling, while rapid water flow outside the net cages (>25 cm s?1) kept the net fouling organisms at bay. Although fish rearing in net cages with inputs of commercial pellet feed increased sessile biofouling (222% higher than outside the net cages) and non‐sessile biofouling (570% higher), the type of fish feed used did not significantly affect biofouling development. The study recommends that the geometry of serially arranged net cages, as commonly deployed in tropical tidal estuaries, be reconfigured to improve flow through in order to minimize the impact of fouling.  相似文献   

11.
Channel catfish (lctalurus punctatus) fingerlings stocked at a rate of 450 fish/0.04 ha pond were simultaneously cultured with fingerlings stocked in 1.25 m3 cages (0, 250, 350, or 450 fishlcage; one cage/pond). The fish in the cages were cultured and harvested for a 90–330 g (whole fish) market. The fish in the open ponds were cultured and harvested for a 490–1,140 g market. Harvest weights of open pond fish in all treatments were similar indicating that the presence of the caged fish and the associated higher daily pond feeding rates did not affect open pond production. Ninety-five to 99% of the caged fish and 96 to 98% of the open pond fish were of marketable size at harvest. Survival and food conversion ratios were similar among treatments. Results of this study indicate that total pond production can be increased (in this case up to 19%) by using a combination of open pond and cage techniques and by simultaneously producing fish for two markets.  相似文献   

12.
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13.
Studies in cage‐cultured fish have reported spatial and temporal variations on parasite prevalence; however, most of these studies have been carried out in cold water and marine environments. Channel catfish, Ictalurus punctatus, is the main floating cages‐raised species used in intensive fish culture in Tamaulipas. In Mexico, there are no seasonal reports on fish parasites in this type of cage system. The aim of the present study was to determine the prevalence and mean intensity of ectoparasites of cage‐cultured channel catfish in a year. Fish were sampled bimonthly from six locations in Tamaulipas and measured and evaluated for ectoparasites. Results showed the presence of two gill‐dwelling metazoans, Ligictaluridus floridanus and Ergasilus cerastes and one skin‐dwelling protozoan, Trichodina sp.; a pattern characterized by peaks in prevalence in early autumn for L. floridanus and late autumn for E. cerastes was observed. In addition, geographic location had a significant effect on the prevalence of L. floridanus and E. cerastes. It was also observed that presence of these parasites was not associated with any fish mortality. To our knowledge, this is the first seasonal study on ectoparasite prevalence on channel catfish reared in cages in México.  相似文献   

14.
The effects of open‐water and caged fish density on growth, feed utilization, water quality and profitability were investigated to assess the feasibility of a small‐scale rotational system for production of Oreochromis niloticus (L.) in fertilized ponds. Hand‐sexed male fingerlings averaging 18.6 and 29.9 g were stocked in open water and cages, respectively in four treatments with open‐pond:caged tilapia ratios of 300:0 (control), 150:150 (L), 300:150 (H1) and 300:300 (H2). The ponds in L and H1 contained one cage, two cages in H2, and the control ponds had no cages. Each cage contained 150 fish, which were fed daily at 1.5% body weight for 125 days. All fish in the open water except the control fish were not fed. Growth of open water tilapia was significantly (P<0.05) higher in L than in control. Feed utilization, dawn DO and economic returns were significantly better (P<0.05) in caged than control ponds. Growth of tilapia in L was significantly lower (P<0.05) in cages than in open water. Fingerling production was significantly lower (P<0.05) in L than in other treatments. In conclusion, cage‐cum‐open‐pond integrated treatment (L) was optimal for O. niloticus production in fertilized ponds. However, the system could not rotate and needed further fine‐tuning to rotate.  相似文献   

15.
A reduction in light intensity may increase shrimp activity, although it may also negatively affect the development of photoautotrophic organisms present in biofilm, an important natural food source for shrimp. This experiment evaluated the influence of light intensity on biofilm development and on the growth of cultured Farfantepenaeus paulensis juveniles. Six cages were deployed in a shrimp culture pond and stocked with 60 juveniles (0.72 ± 0.03 g). Three cages were randomly chosen and covered with five layers of polyamide net to reduce light incidence (shaded treatment), while the other three cages were not covered (control treatment). Biofilm chlorophyll a and microorganism abundance, as well as shrimp growth, were monitored during the experiment. Chlorophyll a concentration and the abundance of bacteria and flagellates were significantly lower in the shaded treatment (P<0.05). After 75 rearing days, shrimp stocked in control treatment achieved significantly higher (5.98 g) (P<0.05) mean weight than shrimp reared in shaded treatment cages (5.13 g). Similarly, the biomass produced was also significantly higher (P<0.05) in the control treatment (322.92 g) than in the shaded treatment (287.31 g). The results of this study demonstrate that light intensity has a huge influence on shrimp performance mainly due to the increase in natural food availability.  相似文献   

16.
The Philippines has vast freshwater resources for cage culture of fish. Two tilapia species, Tilapia mossambica and Tilapia nilotica, are cultured commercially in cages in several lakes.Field testing for cage culture of Tilapia nilotica, the preferred species, is described. A pilot commerical cage farm has been established.The major problems affecting development are the short supply of quality fingerlings, the lack of a standard commercial feed, and the increasing costs of cage construction. Recommendations for resolving these problems are given.  相似文献   

17.
Experiments were carried out to establish the effect of a simulateddecrease in daylight intensity on the yield of the cultured shrimpPenaeus stylirostris. The purpose of these experiments wasto simulate the periods in intertropical regions, which may last for severaldays, when solar radiation levels fall due to seasonal cloud cover. After 4weeks of culture, the light reduction resulted in lower shrimp yields comparedto unshaded tanks. Survival rates ranged from 54.9 to 71.1% for shaded tanksandfrom 77.0 to 83.0% for unshaded tanks. Growth rates varied between 0.091 and0.110 g.d–1 for shaded tanks and between0.189 and 0.224 g.d–1 for unshaded tanks.In unshaded tanks, variation in growth rate is related to initial shrimpstocking densities. The light reduction led to a reduced phytoplankton growthwith, as a consequence, an increase in the concentration of dissolved mineralnitrogen [(NO3 – +NO2 –)-N,(NH4 ++NH3)-N] and dissolved organicnitrogen (DON). The higher mortality and lower growth observed in the shadedtanks cannot be entirely explained by the concentrations of mineral nutrients,the temperature, the pH or the O2 concentration. The lower resultsobtained with the shaded tanks could be most likely a consequence of thetoxicity of dissolved organic matter.  相似文献   

18.
Presence of coastal aquaculture activities in marine landscapes is growing with impacts on the wild fish that share these habitats. However, it is difficult to disentangle subsequent ecological interactions between these activities and marine fish communities. We evaluated the impact of both salmon and halibut farms on mackerel (Scomber scombrus) and whiting (Merlangius merlangus) sampled near sea cages using condition indices and fatty acid (FA) biomarkers. Results of the stomach content analysis indicated that mackerel and whiting consumed waste feed which was also reflected in their modified FA profiles. Both mackerel and whiting had elevated levels of FAs that are of vegetable oils origin. The use of vegetable oils as replacement for marine oils is a lot more common in salmon farming than halibut farming. Additionally, the overall effects of the two fish farms were more pronounced in whiting than in mackerel sampled near the sea cages. By allowing discrimination between sources of trophic interactions, this method could lead to more informed decisions in managing different farming activities.  相似文献   

19.
Socio‐economic factors related to management of costal zones and biological parameters related to species‐specific requirements set limitations for the rearing location of net‐pen sea cages. A cage was designed and installed at 45 m depth based on the REFA Tension Length Cage technology at the cage facility of the Hellenic Centre for Marine Research in Crete. The cage‐net module consisted of a net‐pen contained within a hexagonal rigid frame to maintain the shape of the net. Vertical beams of the frame glider on six tension legs were placed in a circle. The operation of the cage was evaluated using a group of red porgy (Pagrus pagrus) for a rearing period of 4 months whereas a second group reared in a surface net‐pen cage served as control. Growth performance was similar between the experimental groups. The rearing method significantly affected fish skin pigmentation. Individuals reared in the submerged cage had a brighter skin colour and lower skin melatonin content compared with the ones reared in the surface cage. The presented submerged cage may provide a feasible alternative for rearing fish in exposed areas and particularly species requiring specific biological conditions, such as narrow temperature ranges and low light intensity.  相似文献   

20.
In an attempt to improve post‐harvest skin colour in cultured Australian snapper Pagrus auratus, a two‐factor experiment was carried out to investigate the effects of a short‐term change in cage colour before harvest, followed by immersion in K+‐enriched solutions of different concentrations. Snapper supplemented with 39 mg unesterified astaxanthin kg?1 for 50 days were transferred to black (for 1 day) or white cages (for 1 or 7 days) before euthanasia by immersing fish in seawater ice slurries supplemented with 0, 150, 300, 450 or 600 mmol L?1 K+ for 1 h. Each treatment was replicated with five snapper (mean weight=838 g) held individually within 0.2 m3 cages. L*, a* and b* skin colour values of all fish were measured after removal from K+ solutions at 0, 3, 6, 12, 24 and 48 h. After immersion in K+ solutions, fish were stored on ice. Both cage colour and K+ concentration significantly affected post‐harvest skin colour (P<0.05), and there was no interaction between these factors at any of the measurement times (P>0.05). Conditioning dark‐coloured snapper in white surroundings for 1 day was sufficient to significantly improve skin lightness (L*) after death. Although there was no difference between skin lightness values for fish held for either 1 or 7 days in white cages at measurement times up to 12 h, fish held in white cages for 7 days had significantly higher L* values (i.e. they were lighter) after 24 and 48 h of storage on ice than those held only in white cages for 1 day. K+ treatment also affected (improved) skin lightness post harvest although not until 24 and 48 h after removal of fish from solutions. Before this time, K+ treatment had no effect on skin lightness. Snapper killed by seawater ice slurry darkened (lower L*) markedly during the first 3 h of storage in contrast with all K+ treatments that prevented darkening. After 24 and 48 h of storage on ice, fish exposed to 450 and 600 mmol L?1 K+ were significantly lighter than fish from seawater ice slurries. In addition, skin redness (a*) and yellowness (b*) were strongly dependent on K+ concentration. The initial decline in response to K+ was overcome by a return of a* and b* values with time, most likely instigated by a redispersal of erythrosomes in skin erythrophores. Fish killed with 0 mmol L?1 K+ maintained the highest a* and b* values after death, but were associated with darker (lower L*) skin colouration. It is concluded that a combination of conditioning snapper in white surroundings for 1 day before harvest, followed by immersion in seawater ice slurries supplemented with 300–450 mmol L?1 K+ improves skin pigmentation after >24 h of storage on ice.  相似文献   

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