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1.
ZdzisŁaw Zakęś Krystyna Demska-Zakęś PrzemysŁaw Jarocki Konrad Stawecki 《Aquaculture International》2006,14(1-2):127-140
The effect of feeding frequency (one, three, and continuous feeding), feed ration (0.2, 0.5, 0.8% of total fish biomass),
and feeding per se on the oxygen consumption (OC, mg O2 kg−1 h−1) and ammonia excretion (AE, mg TAN kg−1 h−1) of juvenile tench (body weight 15–19 g) and variations in these parameters in daily cycles were examined. Fish metabolism
was studied in a recirculating system (rearing tanks of 0.2 m3, water temperature 23 °C). It was found that oxygen consumption and ammonia excretion depended significantly on feed ration.
An increase of feed ration from 0.2 to 0.8% of fish biomass caused an increase of OC and AE from 126.80 mg O2 kg−1 h−1 and 1.95 mg TAN kg−1 h−1 to 187.35 mg O2 kg−1 h−1 and 8.80 mg TAN kg−1 h−1 (p<0.05). There was no dependence between feeding frequency and the mean rate of oxygen consumption. However, the relationship
between feeding frequency and ammonia excretion by juvenile tench was statistically significant (p<0.05). Feeding frequency significantly affected daily fluctuations of AE and OC. It was found that diurnal variations in
metabolic rates were strictly related to tench feeding, and the daily variations of AE were significantly higher than OC. 相似文献
2.
Commercially exploited tench populations in 755 lakes in the Northeastern part of Poland were observed on the basis of the
fishing data from 1951 to 1994. The observations were analyzed in five size categories of water reservoirs, whose total area
reached over 123,900 ha. The analyses were performed according to the parameter of a commercial fish catch per area unit,
taking into consideration the number of months per year when the lakes were exploited. Statistically significant differences
were determined in the mean value of the tench catch parameter between the different size categories of lakes. Similar time-related
differences were observed. In the lakes >100 ha the relative tench catch gradually declined in the successive time intervals.
Tench was the rarest in catches from lakes <50 ha. The complete disappearance of tench from commercial catches occurred first
as early as the late 1960s in lakes <200 ha. The largest quantities of tench stocking material were introduced to the lakes
from 1951 to 1972. The amount of stocking material per 1 ha of stocked lakes decreased for larger lakes. The average frequency
of tench stocking in the analyzed lakes was higher in larger lake size categories. On the other hand, in each lake size group
the frequency of stocking was found to have declined along with the average volume of the stocking material in the subsequent
11-year-long periods. 相似文献
3.
Tomoki Hashimoto Katsuya Hyodoh Takuma Hirose Satoshi Nishikawa Toshiya Katano Shin-ichi Nakano 《Aquaculture International》2008,16(4):309-318
In the pearl cultivation farms of the Ehime Prefecture, Japan, mass mortalities of the pearl oyster Pinctada fucata have occurred since 1994. The occurrences of mass mortality roughly coincided with a shift of the dominant phytoplankton
from Skeletonema and Chaetoceros to Chaetoceros and Nitzschia all of which belong to Bacillariophyceae. Hence, we evaluated Nitzschia, together with Chaetoceros and Isocrysis, as food for the oyster. Wet weights, lengths, widths, glycogen contents, and growth rates in terms of wet weight of the
oysters in all the feeding treatments were significantly higher than those in the non-feeding treatment. The highest glycogen
content (2.34%) and growth rate (2.21 g month−1) were found in the Chaetoceros treatment. Growth rate in the Isocrysis treatment (1.63 g month−1) was also high, although glycogen content in this treatment (0.41%) was low. In the Nitzschia treatment, growth rate of the oyster (0.94 g month−1) was the lowest and glycogen content (0.83%) was also low relative to that in the Chaetoceros treatment. Chlorophyll a concentration in fecal pellets was lowest in the Nitzschia treatment (<2.7 μg mg−1), suggesting more complete digestion of Nitzschia by the oyster. Thus, Nitzschia was edible and digestible but not assimilated by P. fucata. We propose the following scenario for the relationship between Nitzschia dominance and mass mortality. When Nitzschia dominates in a culture area, the physiological condition of P. fucata deteriorates due to low assimilation of Nitzschia by the oyster, followed by susceptibility of the oyster to infection by agents lethal to the oyster. 相似文献
4.
Fish landing data from the Mombasa Marine National Park (MNP) and a marine reserve exploited by various gears were studied over a 5‐yr period to determine the influence of the closed area and different gears in fisheries. The number fishing and boats per landing site was constant, but total and catch per unit effort progressively declined in all sites on an annual basis irrespective of the existence of a marine reserve, exclusion of the beach seines or use of gear. Differences between landing sites were most pronounced when analysed on a catch per area as opposed to the more standard catch per fisherman, suggesting compensation in human effort when catches decline. A marine reserve next to a closed area that excluded beach seines had the highest catch per area (5.5 kg ha?1 month?1) despite having the highest density of fishermen (0.07 ± 0.02 fishermen ha?1 month?1). The annual rate of decline in the catch was lower than the other sites at around 250 g day?1 compared with 310–400 g day?1 in the other sites. One landing site, which excluded beach seine landings for more than 20 yrs, had a high catch per area (~5.3 kg ha?1 month?1), but after experiencing a doubling in the effort of other gears (line, speargun and trap), the catch per fisherman and area were reduced. Environmental or habitat degradation and excessive effort remain the most likely explanation for the overall declines in catch from 1995 to 1999. Closed areas and beach seine exclusion have the potential to increase catch rates, but the first often reduces the total fishing area and possibly leads to a loss of total catch, at least on a time scale of less than 10 yrs. The exclusion of beach seines can lead to an increase in other gear types that can also cause reductions in catch. 相似文献
5.
The study investigated the growth performance of abalone from juvenile to marketable size in a commercial-scale recirculating
aquaculture system. The rearing system consisted of 12 raceways (4.0 × 0.8 × 0.6 m) with a protein skimmer and a submerged
biofilter for juveniles and 10 raceways (6.6 × 1.3 × 0.6 m) with a protein skimmer and a trickling biofilter for on-growing.
Sea mustard (Undaria pinnatifida) and kelp (Laminaria japonica) were fed to the abalone. The total weight of abalone in the recirculating aquaculture system at the juvenile stage increased
from 22.0 kg (average shell length 24.5 mm) to 75.5 kg (average shell length 42.5 mm) after 180 days. Feed conversion ratios
increased slightly from 13.7 for the first 90 days to 16.3 thereafter. The shell growth rate of juvenile abalone between 24.5 mm
and 34.8 mm was 3.4 mm month−1, while for juveniles between 34.8 mm and 42.5 mm it was 2.6 mm month−1. The total weight of abalone in the recirculating aquaculture system for the on-growing stage increased from 100.0 kg (average
shell length 44.0 mm) to 433.3 kg (average shell length 72.7 mm) after 570 days. The feed conversion ratios for the first
173 days, the next 320 days, and the last 570 days were 19.6, 22.1, and 24.8, respectively. The growth rate of the average
shell length during the on-growing period was 1.5 mm month−1. Total ammonia nitrogen (TAN) concentrations were stabilized below 0.12 mg l−1 in the juvenile recirculating system and 0.14 mg l−1 in the on-growing recirculating system after conditioning of the biofilters. 相似文献
6.
Various procedures for artificial insemination in tench, Tinca tinca (L.) were re-examined with evaluation of fecundity of males and females among different tench strains. The objectives of
this study were to enhance fertilization and hatching rates through optimization of the activation solution, the insemination
process, the activation of gametes, and the elimination of eggs stickiness. Sperm for all experiments was collected directly
into immobilization solution of modified Kurokura solution containing 180 mM of NaCl and stored at 2 °C for 2.5–5 h prior
to the experiment. When dechlorinated tap water was used for activation a gamete ratio of 1150 spermatozoa per egg showed
the best significant fertilisation and hatching rates. Optimal ratio between eggs (weight in g) and activation solution (in
cm3) was 1:1. Different concentrations of activation solutions such as NaCl from 0 to 68 mM (0–136 mOsmol kg−1) without buffer statistically decreased fertilization and hatching rates. The activation solution containing 17 mM of NaCl,
10 mM Tris–HCl, pH 8 and 9 significantly increased fertilization and hatching rates compared to dechlorinated tap water of
pH 7 or activation solution containing 17 mM of NaCl, 10 mM Tris–HCl, pH 6 and 7. Adhesiveness of the eggs was successfully
removed by incubation in Alcalase and activity: 3.16 Anson units per cm3. 相似文献
7.
J. D. Celada J. M. Carral R. Rodríguez M. Sáez-Royuela A. Aguilera P. Melendre J. Martín 《Aquaculture International》2007,15(6):489-495
After artificial reproduction of tench, larvae must be maintained indoors, and studies on rearing conditions are needed, focussing
on the reduction of labour and costs. Three experiments on larvae (5th day post-hatch) were conducted for 25 days using Artemia nauplii as the sole food in order to determine basic feeding and density conditions during the first rearing period. Tench
were maintained in 25 l fibreglass tanks, supplied with an artesian water flow throughout of 0.2 l min−1. Water temperature was 22.5 ± 1°C, and the photoperiod was natural. Larvae fed on a restricted amount of nauplii reached
high survival rates, even with the minimum of 50 nauplii larva−1 day−1. This amount of food may be sufficient at least for the first 25 days of exogenous feeding if fast growth is not the priority,
and high densities can be maintained with good survival rates (over 90% up to 160 larvae l−1 and 77% with 320 larvae l−1). When food was supplied in excess once a day, high survival rates were achieved (91–97%), without differences among the
densities tested. Animals at a density of 100 l−1 reached the highest length (15.57 mm) and individual weight (46.8 mg). This growth is greater than those reported in studies
feeding several times a day. It could be deduced that, while live food remains available for tench, it is not necessary to
feed so frequently. Considering the relationship among the initial number of animals, final survival and growth and ration
supplied, the new data reported here are useful to establish suitable stocking densities under both culture and experimental
conditions. 相似文献
8.
EWA KAMLER LESZEK MYSZKOWSKI RAFAŁ KAMIŃSKI MICHAŁ KORWIN-KOSSAKOWSKI JACEK WOLNICKI 《Aquaculture International》2006,14(1-2):99-111
Duplicate groups of tench (Tinca tinca) juveniles (mean weight 0.69 g) were fed at 28 °C for 70 days either a commercial formulated diet, Futura, or frozen Chironomidae
larvae at four levels: below satiation, at about satiation, above satiation and well above satiation. These are represented
by the feeding groups F1–F4 and C1–C4, respectively. No mortality was observed throughout the experiment. In groups F2–F4
a considerable incidence of uneaten food (>40% observations), deformities of the caudal penduncle, retarded growth, elevated
condition coefficient (>1.2), reduced amounts of minerals in the tissue (<10% dry matter), high C/N ratio (>5) and high caloric
value of the tissue (>28 J mg−1 dry matter) (the latter two suggesting excessive fat deposits), were found. The combination of these indices was indicative
of overfeeding in fish fed the Futura diet at the daily doses ≥2.7% fish biomass. First symptoms of overfeeding: a considerable
incidence of uneaten food, retarded growth, and elevated C/N ratio were observed in the group fed Chironomidae larvae at the
highest level, (C4, wet Chironomidae 20.7% of the fish biomass daily, that is, 3.9% of dry chironomids per fish biomass and
day). Thus, restricted daily doses of formulated diet not exceeding 2.5% fish biomass are recommended for tench juveniles
aged 130–200 days post hatch. Safe daily doses of frozen Chironomidae (in terms of larvae dry weight) remain below 3.5% of
fish biomass. 相似文献
9.
Richard Skøtt Rasmussen Flemming Hausgaard Larsen Stig Jensen 《Aquaculture International》2007,15(2):97-107
Rainbow trout were studied at different rearing densities, fish sizes and feeding frequencies so that we could evaluate the
effect of these parameters on fin condition, growth and feed utilisation. In one study, two sizes of rainbow trout (18–70 g
or 48–125 g), fed to near satiation at 17.7°C, were examined at two rearing densities (11–41 kg m−3 or 21–92 kg m−3). This study showed that the anal fin was healthier (P < 0.05) at low densities. In the second study rainbow trout were again fed to near satiation and grown from 50 g to 125 g
in 16.4°C water, and they were fed either once daily or three times daily at two densities (18–45 kg m−3 or 54–124 kg m−3). Rainbow trout growth and feed utilisation were slightly but significantly (P < 0.05) reduced at high densities, while dorsal fin condition, surprisingly, was better (P < 0.0001) at the high densities. Possible explanations to these findings are discussed. Condition of the left pectoral fin
was improved at once daily feeding (P < 0.05) compared with three feedings per day, at which fights for feed possibly are more frequent. 相似文献
10.
A total of 518 Gerres sp. were collected around Okinawa Island, Japan, from November 2002 to July 2005, with monthly sampling where the standard
length of females (n=218) were 56.2–147.1 mm, and males (n=149) were 62.2–139.4 mm. The maximum ages observed for females were 5+ years and males were 4+ years, estimated by transverse sectioned sagittal otoliths. Mean marginal increment indicated that opaque rings were formed
once a year during April to July. The standard length (SL; mm) — body wet weight (BW; g) relationships were described as BW=(3.26×10−5) SL2.97 and BW=(3.13×10−5) SL
2.98 for females and males, respectively, and the standard length at age described by von Bertalanffy growth function for females,
L
t=137.1(1−e−0.80[t+0.80]) and males, L
t=127.3(1−e−0.82[t+0.93]). 相似文献
11.
The effect of prebiotic xylooligosaccharides (XOS) on the growth performance and digestive enzyme activities of the allogynogenetic
crucian carp, Carassius auratus gibelio, was investigated. XOS was added to fish basal semi-purified diets at three concentrations by dry feed weight: diet 1, 50 mg kg−1; diet 2, 100 mg kg−1; diet 3, 200 mg kg−1, respectively. Twelve aquaria (n = 20) with three replicates for each treatment group (diets 1–3) and control treated without XOS were used. Weights of all
collected carp from each aquarium were determined at the initial phase and at the end of the experiment, and the carp survival
was also determined by counting the individuals in each aquarium. After 45 days, there were significant differences (P < 0.05) in the relative gain rate (RGR), and daily weight gain (DWG) of diets 1–3 were compared with the control. However,
the survival rate was not affected (P > 0.05) by the dietary treatments. For enzymatic analysis, dissection produced a crude mixture of intestine and hepatopancreas
of each segment to measure. The protease activity in the intestine and hepatopancreas content of fish in diet 2 (487.37 ± 20.58 U g−1 and 20.52 ± 1.93 U g−1) were significantly different (P < 0.05) from that in the control (428.13 ± 23.26 U g−1 and 12.81 ± 1.52 U g−1) and diet 3 (428.00 ± 23.78 U g−1 and 14.04 ± 1.59 U g−1). Amylase activity in the intestine was significantly higher for diet 2 compared to diet 1 and the control. As for amylase
in the hepatopancreas, assays showed higher activity in diet 2 (P < 0.05) compared to the rest. 相似文献
12.
L. R. Harris M. H. Cake D. J. Macey I. C. Potter 《Fish physiology and biochemistry》1990,8(6):451-457
The concentration of total non-haem iron and its ferritin iron component, and the activity of the enzyme superoxide dismutase
(SOD), were measured in the livers of ammocoetes, metamorphosing animals (stages 1–7) and recently metamorphosed downstream
migrants of the lamprey Geotria australis. Total non-haem iron in the liver rose significantly from 0.15–0.55 μg.mg wet weight−1 in ammocoetes and metamorphosing stages 1–3 to 2.2–2.9 μg.mg−1 in stages 5–7 and to 8.8 μg.mg−1 in downstream migrants. The comparable values for ferritin iron were 0.06–0.26, 1.4–2.0, and 5.3 μg.mg−1. Superoxide dismutase activity fell sharply from 0.39 μg.mg−1 in large ammocoetes to between 0.07 μg.mg−1 in stage 1 and 0.15 μg.mg−1 in stage 6, before rising significantly to 0.26 μg.mg−1 in stage 7 and 0.35 μg.mg−1 in downstream migrants. The sharp fall in SOD activity at the beginning of metamorphosis is assumed to be related to the
marked decline in plasma iron which occurs at the onset of this non-trophic phase in the life cycle. It is proposed that the
subsequent increase in SOD activity in the liver of G. australis with increasing iron represents a mechanism aimed at reducing the potentially toxic effects of iron accumulation. This view
is consistent with the significant and positive correlation found between both total non-haem and ferritin iron and SOD activity
in the liver of non-trophic animals. 相似文献
13.
Standard oxygen consumption rate (MO2) was determined for 19 cownose rays (Rhinoptera bonasus) using flow-through respirometry. Rays ranged in size from 0.4 to 8.25 kg (350–790 mm DW). Respirometry experiments were
conducted on seasonally acclimatized rays at temperatures from 19.0 to 28.8 °C. Estimates of mass-dependent MO2 ranged from 55.88 mg O2 kg−1 h−1 for an 8.25 kg ray to 332.75 mg O2 kg−1 h−1 for a 2.2 kg animal at 22–25°C. Multiple regression analysis examining the effect of temperature, salinity, and mass on standard
mass-independent MO2 found temperature (P < 0.01), and mass (P < 0.0001) to have a significant effect on oxygen consumption, whereas salinity
did not (P > 0.05). Q
10 was calculated as 2.33 (19–28 °C), falling between the estimates determined for two other batoid species, the bull ray (Myliobatos aquila; Q
10 = 1.87) and the bat ray (Myliobatis californica; Q
10 = 3.00). The difference in the Q
10 estimates may be attributed to the use of seasonally acclimatized as opposed to laboratory-acclimated animals. 相似文献
14.
Nicolas Caille Marek Rodina Martin Kocour David Gela Martin Flajšhans Otomar Linhart 《Aquaculture International》2006,14(1-2):75-87
The spermiation of tench males was stimulated with Supergestran containing mammalian LHRHa lecireline at the following doses:
5, 10, 20 and 40 g kg−1 b.w.; then with carp pituitary suspension (CPS) at a dose of 2 mg kg−1 b.w. and with a control of saline physiological solution. The following days, meaning 24, 48 and 72 h after injection, sperm
was collected to evaluate volume and the number of sperm per male per kg body weight (B.W.) The percentage of motile sperm
and velocity of spermatozoa were measured 48 h after hormonal injection, and 72 h after hormonal injection the sperm was evaluated
for fertilization and hatching ability. All 42 males in experimental groups were diploid. Live weight did not differ significantly
among experimental groups. The strongest stimulation of spermiation was achieved with LHRHa in dosage of 20 and 40 g kg−1 b.w. and CPS compared to males of the control group and lower dosage of LHRHa. Analysis of variance showed no significant
influence of the treatment on the velocity and percentage of motile spermatozoa. The effect of different treatment on the
fertilization capacity (the number of spermatozoa per egg was equilibrated) was significant. Significantly the highest quality
of sperm collected 72 h after injection expressed by percentage of fertilization and hatching (62–65% fertilization and 61–64%
hatching rates, respectively) was found for LHRHa in dosage of 20 and 40 g kg−1 b.w. Significantly the lowest parameters of fertilization and hatching were found for the control group, on the 12% level. 相似文献
15.
Jeffrey A. Malison Lynne S. Procarione Terence P. Barry Anne R. Kapuscinski Terrence B. Kayes 《Fish physiology and biochemistry》1994,13(6):473-484
The annual reproductive cycle of walleye (Stizostedion vitreum) was characterized by documenting changes in gonadal development and serum levels of estradiol-17β (E2), testosterone (T), 17α,20β-dihydroxy-4-pregnen-3-one (17,20-P), and 11-ketotestosterone (11-KT) in wild fish captured from
upper midwestern lakes and rivers throughout the year. Fish from the populations used in this study spawn annually in early-
to mid-April. Walleye showed group synchronous ovarian development with exogenous vitellogenesis beginning in autumn. Oocyte
diameters increased rapidly from ∼ 200 μm in October to ∼ 1,000 μm in November, and reached a maximum of 1,500 μm just prior
to spawning. Changes in gonadosomatic indices (GSIs) paralleled changes in oocyte diameters. Serum E2 levels in females increased rapidly from low values in October (< 0.1 ng ml−1) to peak levels of 3.7 ng ml−1 in November, coinciding with the period of the most rapid ovarian growth. Subsequently, E2 levels decreased from December through spawning. Serum T levels exhibited a bimodal pattern, increasing to 1.6 ng ml−1 in November, and peaking again at 3.3 ng ml−1 just prior to spawning. We detected 11-KT in the serum of some females at concentrations up to 5.6 ng ml−1, but no seasonal pattern was apparent. In this study (unlike our results in a related study) 17,20-P was not detected. In
males, differentiation of spermatogonia began in late August, and by January the testes were filled (> 95% of germ cells)
with spermatozoa. Mature spermatozoa could be expressed from males from January through April. GSIs ranged from 0.2% (post-spawn)
to 3.2% (pre-spawn). Serum T levels rose from undetectable levels in post-spawn males to 1.6 ng ml−1 by November, remained elevated throughout the winter, and peaked at 2.8 ng ml−1 I prior to spawning. Levels of 11-KT in males remained low (< 10 ng ml−1, from post-spawning through January, then increased significantly by March and peaked just prior to spawning at 39.7 ng ml−1. Our results indicate that vitellogenesis and spermatogenesis are complete or nearly so, in walleye by early winter, and
suggest that it may be possible to induce spawning in this species several months prior to the normal spawning season by subjecting
fish to relatively simple environmental and hormonal treatments. 相似文献
16.
Survival, growth and yield of competent great scallop (Pecten maximus) larvae were investigated during a full production season in a commercial hatchery in western Norway. Broodstock were collected from natural scallop beds and 12 groups were induced to spawn during the period December 2002 to July 2003. Larvae were reared on a large scale in 36 flow-through tanks (3500 l) at 17±1 °C and continuously fed a mixture of five algal species produced in an indoor continuous-flow system. Large variations in larval performance between spawning groups and tanks were observed, but the results were as good as earlier results using the batch system and prophylactic addition of chloramphenicol. Growth from days 3–24 averaged 4.8 μm day−1±0.8 (sd) and survival 22.4%±21.8 (sd). Mean yield of day 3 larvae was 7.1%±10.0 (sd) and 26.6%±25.9 (sd) for those surviving to day 24. Yield was significantly correlated to larval survival. Larval success was related to initial larval density, algal concentration and season. It was found that the best production regime had an initial larval density lower than 6 ml−1 and algal concentration of less than 12 μl−1 regardless of season. Seventeen tanks met these criteria and produced a mean yield of 0.5 larvae ml−1 to settlement. Flow-through systems are currently regarded as the only feasible method for viable hatchery production of P. maximus larvae in Norway. 相似文献
17.
S. M. J. Punitha M. M. Babu V. Sivaram V. S. Shankar S. A. Dhas T. C. Mahesh G. Immanuel T. Citarasu 《Aquaculture International》2008,16(6):511-523
Herbals such as Cynodon dactylon, Piper longum, Phyllanthus niruri, Tridax procumbens, and Zingiber officinalis were extracted with acetone, benzene, butanol, and petroleum ether and screened against the pathogen Vibrio harveyi isolated from the infected Grouper Epinephalus tauvina. Among the different solvent extractions screening to V. harveyi, petroleum ether extracts were suppressed significantly (P < 0.05). Equal proportions of the all-plant extracts were mixed with the artificial feeds at concentrations of 100, 200,
400, and 800 mg kg−1 of diet and fed to grouper juveniles of 20 ± 2 g average weight for a period of 60 days. Every 20 days, fish juveniles were
challenged with V. harveyi and the immune response was studied. The herbal diets significantly (P < 0.05) increased the survival, growth, and immune responses compared to the control group. The herbal diets were significantly
improved (P < 0.01) in immune parameters such as phagocytic activity and albumin–globulin (A–G) ratio. Among the different concentrations
of the herbals in the diet, the 400 mg kg−1 diet was the most effective in the experiment. 相似文献
18.
The agarophyte Gracilaria birdiae Plastino & Oliveira was cultivated under field conditions in an estuary over a 6-month period. Biomass production varied significantly (p<0.01) and ranged from 900.0 to 3537.0 g m−2 with a mean of 2124.4±1004.36 g m−2 over the cultivation period. The epiphyte-biomass varied from 64.7 to 313 g m−2, with maximum values observed in July. Relative growth rate (RGR) of G. birdiae varying from −0.59 to 4.67% day−1, with a maximum mean observed in July. Correlation analysis showed that RGR was positively correlated with epiphyte-biomass (R-Pearson=0.69; p< 0.01) and negatively correlated with salinity (R-Pearson=−0.41; p<0.05). These correlations were used in a mathematical regression model to estimate the growth of Gracilaria in an estuary. The regression model explained 61% of RGR variability demonstrating that growth rates of Gracilaria were directly related to the variables salinity and epiphytes. The model was developed to help to predict production at a cultivation site in order to evaluate its suitability for Gracilaria cultivation. 相似文献
19.
Alfredo Hernández-Llamas Javier M.J. Ruiz-Velazco Victor M. Gomez-Muñoz 《Aquacultural Engineering》2011,45(2):66-73
We investigated the variability of shrimp Litopenaeus vannamei production by incorporating stochastic elements into deterministic stock models and determined the contribution that white spot disease, zootechnical parameters, water quality, and alternative management strategies have on variability. The model was calibrated for intensive shrimp cultivation in the State of Nayarit, Mexico. Mean annual production increased as a consequence of improved management from 8000 kg ha−1 to 22,000 kg ha−1 when cultivation was not affected by the disease and from 3200 kg ha−1 to 10,400 kg ha−1 when the disease affected production. When simultaneously considering both cases, mean annual production increased from 6300 kg ha−1 to 16,800 kg ha−1. White spot disease was a major factor determining variability of production. Shrimp production was particularly sensitive to levels of dissolved oxygen when management was inadequate, while final weight and mortality rate of shrimp were more sensitive when management improved. Water temperature and salinity had intermediate importance, and mortality caused by the disease and the time when mortality occurred had intermediate or low relevance. Improving management increased shrimp production and diminished variability. The duration of cultivation and stocking density were the most important management variables controlling variability of production when cultivation was affected by the white spot disease. When the disease was not present, pond size and duration of cultivation were the main factors affecting production. Starting time of aeration had relatively lower importance in determining variability, while the stochastic values of dissolved oxygen, in contrast, became most important. These results call for studies on improving aeration management to reduce variability of dissolved oxygen in ponds. 相似文献
20.
Jesus D. Celada Amelia Aguilera Jose M. Carral María Sáez-Royuela Pedro M. Melendre Jose R. Pérez 《Aquaculture International》2007,15(6):461-465
In two 120-day experiments, performed in the laboratory at 22°C, the effects of stocking density on the survival and growth
of juvenile tench (Tinca tinca L.) were evaluated. Fish were kept in fibreglass tanks, supplied throughout with flow of artesian water, and fed a dry diet
for salmonids, in excess, supplemented with restricted amounts of Artemia nauplii. In the first experiment four-month-old juveniles (0.31 ± 0.04 g and 32.00 ± 1.17 mm TL) were stocked at four densities—0.18,
0.88, 1.05, and 2.10 g l−1. Survival was high (>89%) for all treatments. Final densities ranged between 1.10 g l−1 (significantly lowest) and 10.46 g l−1 (significantly highest). The density increase was significantly higher (611%) for fish stocked at the lowest initial density
(0.18 g l−1) than for fish stocked at 0.88, 1.05, and 2.10 g l−1, for which the density increase averaged 457%. In the second experiment, 4.5-month-old juveniles (0.58 ± 0.17 g and 39.54 ± 0.83 mm
TL) were stocked at three densities—1.05, 3.00, and 4.00 g l−1. Survival was high (>96%) for all treatments. Final densities ranged between 4.08 and 16.53 g l−1 and were significantly higher for greater initial densities. The density increase was greatest (413%) for fish stocked at
the highest density (4 g l−1) and was not significantly different for fish stocked at 1.05 and 3 g l−1. Considering all the densities in the two experiments, for stocking at 4 g l−1 the final density was 15 times higher than that reached after stocking at 0.18 g l−1, without harmful effects on survival and growth. This final density (equivalent to 16.53 kg m−3) is in the range recommended for other fish species in this period under intensive conditions. 相似文献