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1.
A 55‐day mesocosm experiment was conducted to evaluate the effects of commercial microbial products (Novozymes Pond Protect and Novozymes Pond Plus) and extra carbon (glucose) on water quality and bacterial community in a fish polyculture system. A 2 × 2 layout, including four treatments (non‐supplementation of the microbial products or glucose, adding glucose, adding the microbial products and adding the microbial products and glucose in combination), was established. The microbial products and glucose were added on the 40th day, 46th day and 52th day. Ammonia, nitrite and nitrate reduced in the tanks after glucose addition, while adding the microbial products did not significantly affect ammonia, nitrite, nitrate, reactive phosphate, total nitrogen, total phosphorus, chemical oxygen demand and total organic carbon. Adding the microbial products and glucose affected relative abundance of some bacterial taxa, but did not reshape bacterial community. Non‐positive interactive effect on water quality and bacterial community was detected between the microbial products and glucose. This study reveals that supplementation of the microbial products did not benefit water quality in the fish polyculture system, and glucose addition could reduce ammonia, nitrite and nitrate.  相似文献   

2.
Replicated groups of Atlantic cod were rearedfor up to 40 days in 100 l tanks stocked at adensity of 75 eggs l–1. Larvae weretransferred from rotifers, Brachionusplicatilis, to either fresh-hatched orenriched Artemia nauplii on each of days5, 15 and 25 post-hatch (ph). Rotifers wereprogressively withdrawn over a 5 day period.The type of Artemia offered(fresh-hatched, enriched) did not affectsurvival or growth rates at any of the 3transfer ages. Larvae transferred toArtemia from day 5 ph suffered a highincidence of swimbladder over-inflation andhigh mortality during metamorphosis (< 1%survival to day 36 ph). Cod in the day 15 and day25 transfer groups did not differ significantlyin weight-specific growth rate or size on day40 ph (mean standard length 13.8 mm, dry weight3.8 mg). Highest mean survival rates to day 40ph (18.1%) and lowest mortality followingtransfer to nursery tanks were also observed inthe day 25 transfer groups. Fish that receivedArtemia from day 5 ph containedcirca twice as much total lipid per unit bodyweight and had a 30% higher triacylglycerol(TAG) content compared to all other groups.Ratios of the essential fatty acidsdocosahexaenoic acid (DHA), eicosapentaenoicacid (EPA) and arachidonic acid (ARA) alsodiffered according to age-at-transition.DHA:EPA ratio exceeded 1 only in codtransferred to Artemia on day 25 ph.Based on these findings, it is recommended thatintensively reared Atlantic cod should continueto receive rotifers until completion ofmetamorphosis.  相似文献   

3.
Abstract.— The effects of recirculation aquaculture on walleye Stizostedion vitreuin fry culture was evaluated from hatch (day 0) to day 65 and compared to traditional flow-through aquaculture used at New York State's Fish Culture Station, Oneida, New York, USA. A comparison of survival rates of walleye fry through a feed transition period was also conducted with the variable being the age (d) at which dry feed was first introduced to fingerlings; this trial was conducted using recirculation aquaculture systems only. Comparisons were made of growth rates and survival rates broken down into two life stages: stage one was from day 0 to day 45 and stage two from day 45 to day 65. All systems were taken off live feed completely on day 45 resulting in a feed transition period between days 45 and 65. Fish in the flow-through system had the highest cumulative growth rates through day 70 (P < 0.05) while fish in the recirculating system grew faster through day 53 (P < 0.10). The recirculating system showed significantly higher survival rates during the feed transition period (day 45–65) than fish in the conventional flow-through system (P < 0.05). This is important because the transition period is the most stressful period in training fingerlings onto dry feed from a live diet. It was found that fish started on a dry diet on day I or day 14 in addition to the live diet had a significantly higher survival rate through the feed transition period than fish started on dry feed on day 30 (P < 0.1). The age at which dry feed was introduced had no significant impact on growth rates. There was a significant positive correlation (P < 0.05) between survival rates and the initial stocking density over a range of densities from 3,500 to 7,000 fish/m3.  相似文献   

4.
A 15‐day lab‐scale experiment was performed to determine the possible use of bioflocs as a feed for Macrobrachium rosenbergii postlarvae. The bioflocs were grown on acetate, glycerol and glucose. A glycerol‐fed reactor was initially inoculated with a Bacillus spores mixture. The highest protein content was obtained in the (glycerol+Bacillus) bioflocs, i.e. 58±9% dry weight (DW). The glycerol and acetate bioflocs showed a lower, but similar content (42–43% DW) and glucose bioflocs contained 28±3% DW. Higher total n‐6 fatty acid contents were observed in the glycerol and (glycerol+Bacillus) bioflocs. The vitamin C content was variable, up to 54 μg ascorbic acid g?1 DW in the glycerol bioflocs. Bioflocs were fed to M. rosenbergii postlarvae as the sole feed. High survival levels were obtained in the (glycerol+Bacillus) and glucose groups, i.e. 75±7% and 70±0% respectively. This was significantly higher than the starvation control (0% survival after 15 days). This indicated that the prawns were able to feed on the bioflocs. These results are in accordance with the biofloc's nutritional parameters and suggest that the choice of the carbon source used for growing bioflocs is of prime importance.  相似文献   

5.
冯汉茹  张其中  罗芬  朱成科  鉏超 《水产学报》2009,33(6):1003-1010
阐明生殖期亲鱼在注射灭活菌苗后的血细胞和体液免疫变化规律,是预防亲鱼产后虚弱患病和仔鱼染病死亡的理论基础。本研究在试验组和对照组黄颡鱼胸鳍基部分别注射0.2 mL浓度为1.0×108 CFU/mL福尔马林灭活温和气单胞菌苗（F-AS）和0.65%灭菌生理盐水,在免疫后第1、2、4、7、14、21、28、35天,从尾静脉采血,测定外周血液血细胞数量及组成比例,血细胞吞噬活性和抗体效价。结果显示：注射菌苗后白细胞数量和淋巴细胞的白细胞分类计数逐渐增加,显著高于对照;中性粒细胞、单核细胞的白细胞分类计数以及吞噬百分比（PP）、吞噬指数（PI）在4～7 d显著高于对照;抗体效价逐渐升高且在第14天达到最高,随后逐渐下降;而红细胞数和血栓细胞的白细胞分类计数逐渐下降,显著低于对照组。结果表明：单次注射菌苗后亲鱼可以产生良好的免疫应答,1～7 d以增强单核细胞和中性粒细胞等非特异细胞免疫为主;7～35 d淋巴细胞增值,并大量释放抗体且在第21天淋巴细胞出现极显著升高,此后虽逐渐下降但仍显著高于对照,抗体维持在较高水平上的时间为1周左右,建议在黄颡鱼催产前10～14 d进行单次菌苗注射以增强亲鱼免疫力。  相似文献   

6.
We have previously reported that night‐time lighting prevents the mass death of Pacific bluefin tuna (PBT) juvenile due to collision and/or contact with the walls of sea cages, immediately after transfer to the cages, and that night‐time lighting does not negatively impact fish stress levels. However, the period of night‐time lighting should be limited to minimize negative impacts on the surrounding environment and aid management. Therefore, we investigated the optimal period of night‐time lighting by evaluating the whole‐body cortisol and glucose levels as stress parameters, growth performance and survival of PBT juvenile in four cages with different periods of night‐time lighting (i.e. unlit, 4‐day, 8‐day and 12‐day lighting). The results showed that almost all fish were died 1 day after transfer to the unlit cage. In comparison, the other groups (4‐day, 8‐day and 12‐day lighting) had high survival rates (92.5–96.0%) without significant difference. However, in the 4‐day‐lighting group, an obvious stress response was recorded on day 5, and growth performance was significantly lower. In the 8‐day‐lighting group, whole‐body cortisol levels were slightly elevated on day 9; however, significantly elevation was not recorded on day 12. These results indicate that the recommended lighting period of night‐time lighting in sea cages is 8–12 days.  相似文献   

7.
Monthly budgets for nitrogen and phosphorus for a marine fish pond in Eilat were determined for the period September 1983 to June 1984. The ponds are operated as a semi-open system, 41% of the pond water being replaced each day by water from a nearby seawater well. Only 29% of the phosphorus and 36% of the nitrogen are incorporated into harvestable fish flesh (Sparus aurata or Mugil sp.). The remainder reaches the pond as uneaten food, fish faeces or excreted matter, and it is then available to support high levels of phytoplankton and heterotrophic activity. The total input of nutrients supplied to the ponds showed a seasonal trend, with the lowest amount being supplied at the beginning of the sampling period (October) (5.2 moles N/day, 0.25 moles P/day), and increasing in June to 10.6 moles N/day, 0.57 moles P/day. All the increase was due to the amount of food fed. A large proportion (70–80%) of the excess nutrients was exported from the system as dissolved or particulate matter in the overflow. Because of this the water quality of the ponds has remained at levels which have enabled 6.5–12 tons fish/ha to be cultured without regular drying of the ponds. Oysters have been grown on the plankton carried out with the overflow. The ponds have a surplus of nutrient inflow in October/November (1.9 moles N/day, 0.06 moles P/day), a small deficit of N (0.4 moles/day), and surplus of P (0.01 moles/day) in spring, and a large surplus again in May and June of 1.3 moles N/day, 0.11 moles P/day. In all, 60–120% of the nutrient inputs are directly accounted for.  相似文献   

8.
在水温22～24℃,pH7.0左右的人工培育条件下,对密斯特黄彩鲶(Mystus sp.)仔、稚、幼鱼的形态特征和生长发育进行了观察与研究。密斯特黄彩鲶的鱼苗发育分为卵黄囊期仔鱼期(初孵至第5天)、晚期仔鱼期(第6～10天)、稚鱼期(第11～20天)和幼鱼期(第20天以后)。初孵仔鱼平均全长5.12 mm,卵黄囊体积1.63 mm3;仔鱼第3天开始摄食,第5天卵黄囊被完全吸收,鱼苗主要外部器官主要集中在晚期仔鱼阶期和稚鱼期内形成。仔鱼在饥饿状态下最高初次摄食率出现在出膜后第6天,为84.0%,其饥饿的不可逆点则为出膜后第8天,第8天以后即进入不可逆PNR期,至第11天绝大部分饥饿仔鱼死亡。  相似文献   

9.
投喂频率对黄鳝幼鱼摄食、生长及饵料利用效率的影响   总被引：1，自引：0，他引：1  
研究了不同投喂频率对黄鳝(Monopterus albus)摄食率、特定生长率、饵料效率、体重分化、鱼体组成的影响。试验共设5组不同投喂频率(2、3、4、12次/d和24次/d),每组3个重复,试验持续30 d。结果显示:投喂频率4次/d组的摄食率显著高于其它各组(P<0.05);特定生长率有不同程度增高,4次/d组达到最高(P<0.05);饲料利用效率4次/d组显著高于2次/d组(P<0.05),与其它组无显著性差异(P>0.05);随着投喂频率增加,各试验组组内个体体重无显著差异(P>0.05),黄鳝的规格趋于整齐。试验各组黄鳝的鱼体成分无显著性差异(P>0.05);饵料蛋白质和能量的表观消化率,在4次/d时达到最高(P<0.05)。试验表明:黄鳝的生长受投喂频率的影响,每天投喂4次是黄鳝养殖的最佳投喂频率。  相似文献   

10.
The level of infection by infectious pancreatic necrosis virus (IPNV) of kidney macrophages from 12 asymptomatic carrier Atlantic salmon post-smolts was studied. Kidney leucocytes were fractionated on 34/51% Percoll gradients, allowed to adhere to plastic wells overnight, washed to remove non-adherent cells and cultured for up to 7 days with or without renewal of medium on day 3. On day 1, supernatants were harvested, macrophages were counted, lysed and IPNV in the supernatants and lysates was titred in chinook salmon embryo (CHSE-214) cells. The multiplicity of infection ranged between 1:2.2 and 1:7.4 (virus:macrophages). On day 3, the titres of IPNV in macrophage lysates decreased and in wells where the medium was renewed on day 3, IPNV was no longer detectable on day 7. In the supernatants, one fish was positive for IPNV on day 1, four fish on day 3 but none were detectably positive on day 7. In parallel wells in which the medium was not renewed, on day 7 IPNV was detected in macrophage lysates of three fish and the supernatants were also IPNV positive in two of these fish. This suggests that virus might be shed from infected macrophages and then reinfect other macrophages. When macrophages were serially diluted in wells and cultured for 24 h, IPNV could be cultured from macrophage lysates of wells containing between two and 70 macrophages. These results indicate that a very high proportion of the adherent kidney macrophages must be infected with very few non-replicating virions.  相似文献   

11.
The present study analyzed the effects of prey density, the time of day, and ontogenetic development on the predation of Artemia nauplii by the larvae of the Amazon river prawn, Macrobrachium amazonicum, as well as possible synergy among these factors. Larvae were raised in 120‐L tanks with biological filter systems, and fed on recently hatched Artemia nauplii, using two feeding management protocols: (a) fed once per day at 2000 h (high density – HD) and (b) half of the ration provided at 2000 h, complemented at 0800 h the following day by a replacement of the nauplii consumed up to a maximum of the full ration (low density with replacement – LDWR). Each treatment consisted of six replicates. The consumption of nauplii was estimated prior to the feeding times. Consumption varied according to time of day, ontogenetic development, and feeding protocol. The larvae ingested more nauplii during the daytime at most developmental stages. Ingestion rates were similar during the day under both treatments, but at night the higher density of prey in the HD treatment caused a higher encounter rate and increased ingestion of nauplii by the larvae. Among the performance indicators only survival was greater in HD in comparison with LDWR; productivity and dry weight were similar. The results indicate a circadian trophic rhythm in M. amazonicum, with the encounter rate being an important mechanism for the capture of prey during the night. A second mechanism – probably the visual system – aids the perception of prey during the daytime. Based on these results, we suggest that feeding captive Amazon river prawn larvae only once a day would be appropriate and economically beneficial. Further work is necessary to determine the most effective time that this single feed should be applied.  相似文献   

12.
The hypophysis of early larval stages, from the moment of hatching on the 18th day after fertilization to the 101st day of larval life, of the arctic lamprey Lampetra japonica was studied with scanning and transmission electron microscopes. A solid cord of cells of the distal part of the nasopharyngeal duct represents the early adenohypophysis. On the 20th day after fertilization, several of the epithelial cells of this structure showed first indications of secretory activity with an extensive Golgi apparatus and small electron-dense secretory granules. On the 26th day, non-secretory, stellate (=supporting) cells and secretary cells can be distinguished. Already on the 39th day, two different parts can be distinguished in the adenohypophysis: the pars distalis with cells containing small dense granules, and the pars intermedia with cells containing larger granules of medium density. The number of granulated cells increases steadily; on the 101st day two pars distalis cell types can be distinguished. The neurohypophysis consists of a thin anterior and a thick posterior part. Already on the 20th day single nerve terminals in the ependymal layer of the diencephalic (=infundibular) floor contain dense elementary granules. The number of granule-containing terminals increases steadily; on the 101st day almost all terminals contain granules. The present observations suggest an early secretory function of the lamprey hypophysis.  相似文献   

13.
A 10 week experiment was conducted to determine theeffects of feeding rate on growth, feed utilizationand body composition of the tropical bagrid catfish,Mystus nemurus. Catfish fingerlings with anaverage initial body weight of 12 g were fed apractical diet (36.2% protein, 16.5 kJ/g diet) atrates of 1, 2, 2.5, 3, 3.5, 4 or 5% of their bodyweight (BW) per day in two equal meals. Watertemperature was approximately 29 °C throughoutthe experiment. Percent weight gain increased almostlinearly with increasing feeding rates up to 2.5%BW/day beyond which no significant (P > 0.05)improvement in weight gain was observed. The specificgrowth rate of catfish fed rations of 1% BW/day was0.72%/day and this increased significantly to anaverage of 1.39%/day for catfish fed 2.5% BW/day andbeyond. Feed utilization did not differ significantly(P > 0.05) between fish fed 1.0 to 2.5%BW/day but decreased when rations were increased to3.0% BW/day and above. Feed efficiency ratio was0.79 for catfish fed 1.0% BW/day compared to a ratioof 0.27 for fish fed at 5% BW/day. Catfish fed 1.0%BW/day had the lowest condition factor, hepato- andviscerosomatic indices, but the highest carcass tobody weight ratio. These fish also had lowerproportions of whole body dry matter, lipid andprotein, carcass dry matter and lipid, and visceraldry matter and lipid than fish in other groups. Therewere no significant differences in either conditionindices or relative body composition of fish fedrations of 2.0 to 5.0% BW/day. Based on the growth,feed efficiency and body composition data obtained, afeeding rate of 2.5% BW per day is recommended forM. nemurus fingerlings raised at 29 °C.  相似文献   

14.
Soybean molasses was evaluated as a partial replacement for sugarcane molasses as a carbon source for biofloc development in the superintensive culture of Pacific white shrimp (Litopenaeus vannamei). A 50‐day study was conducted with juvenile (3.2 g) shrimp stocked in 16 800 L tanks at a stocking density of 250 shrimp m?3. Control of total ammonia concentration was performed by the addition of combined mixtures of soybean and sugarcane molasses to the culture water. Three different molasses treatments were evaluated using different soybean‐to‐sugarcane molasses ratios: 15–85%, 38–62% and 60–40% respectively. The control group was treated only with sugarcane molasses. Water quality, chlorophyll a concentration, heterotrophic bacterial load, Vibrio spp. concentration and zootechnical indexes were all evaluated. Total ammonia concentration was controlled by heterotrophic and chemotrophic pathways. Biofloc formation, as quantified by measuring the total suspended solids, was not altered. The Vibrio spp. concentration showed a significant reduction in treatments with soybean‐to‐sugarcane molasses ratios of 38–62% and 60–40%. All combined mixtures of soybean and sugarcane molasses could maintain water quality and productivity in the superintensive culture of L. vannamei using the biofloc system. Thus, the potential use of a residue from agroindustry as a carbon source in a biofloc culture is demonstrated.  相似文献   

15.
An eight‐week feeding trial was conducted to evaluate the feed intake, growth, feed utilization, body composition and waste output of juvenile hybrid bream at different feeding frequencies (0.5, 1, 2, 3 or 4 meals/day). Fish (initial body weight of 10.6 ± 0.8 g) were fed to satiation at each feeding. The test diet contained 336 g/kg crude protein and 79 g/kg crude lipid. The weight gain significantly increased with increase in feeding frequency from 0.5 to 3 meals/day (p < 0.05) and afterwards did not change with feeding frequency from 3 to 4 meals/day (p > 0.05). The feed intake increased with increase in feeding frequency (p < 0.05). Fish fed at 3 meals/day exhibited the lowest feed conversion ratio and waste output of nitrogen and phosphorus, however, the highest nitrogen retention efficiency (p < 0.05). No significant differences were found in the phosphorus retention efficiency, the body composition of crude protein, ash and phosphorus among all the feeding frequencies (p > 0.05). The body lipid content increased, whereas the content of moisture decreased, with the increase in feeding frequency (p < 0.05). The present study reveals that the optimum feeding frequency is 3 meals/day for hybrid bream.  相似文献   

16.
The freshness of red porgy slaughtered in ice slurry and stored in melting ice was evaluated instrumentally, biochemically and sensorialy. Additionally, postmortem skin colour changes were monitored, in an attempt to demonstrate the use of chromaticity parameters as a reliable and convenient approach to quality assessment. Dielectric properties showed a statistically significant decrease (P<0.05) from 12±0 on day 0 to 7.85±0.31 on day 7; there was also a significant decrease in muscle polyamines with more than two amino groups (spermidine and spermine) and an increase in the di‐amine putrescine. The sensorial score was significantly decreased from 30±0 to 4.33±0.21 on day 7. Minimal lightness (L*) and hue (H°ab) at the dorsal skin area were observed on days 1 and 3 following harvesting. Finally, there was a marked decrease in the entire colour index (ECI – a combination of skin hue and chroma) of both the dorsal and the ventral area in day 3 onwards to day 7, as well as a statistically significant correlation between all the estimated freshness indices and ECI. Based on all these, we inferred that the total polyamines (or putrescine to spermidine and spermine ratio) and ECI could be reliable estimators of freshness, at least under the experimental conditions applied.  相似文献   

17.
对驼背鲈(Chromileptes altivelis)的胚胎发育及仔、稚、幼鱼的形态特征进行了详细的观察与研究,描述了从受精卵到仔、稚、幼鱼各发育期的时间和形态特征变化。结果表明,在水温25-26℃、盐度30的海水中,受精卵历时27 h 25 min完成整个胚胎发育过程,经历从卵裂、囊胚、原肠、神经胚到肌节形成、各器官的逐渐形成、变化、完善等一系列的胚胎发育和变化过程;根据其卵黄囊消长情况、鳞片的覆盖状态、体色发生的不同变化以及第二背鳍和腹鳍的消长,将胚后发育分为仔、稚、幼鱼3个阶段。在水温22-26℃、盐度29-31、DO≥5 mg/L的条件下,2-3 d仔鱼卵黄囊消失,开口摄食;生长发育至31 d,仔鱼已变态进入稚鱼期;培育至57 d,稚鱼完成变态,成为幼鱼。第二背鳍棘和腹鳍棘的生长与收缩等石斑鱼类早期发育的共性生长特征及其体表特性体色变化特征为驼背鲈胚后发育过程中最明显的特征。  相似文献   

18.
Razorback sucker fry were raised for 126 days and fed five diets for three time periods: in Phase I fish were fed BioKyowa-B from day 5 to day 25 (post-hatching); in Phase II (day 26 to day 52), fish were fed either BioKyowa-A, Bio-Dry, AP-100, or Silver Cup Salmon Starter; during Phase III (days 53-126), fish were fed either BioKyowa-A or Silver Cup Salmon Starter. In Phase I, the fish doubled in body weight and had high survival (96%). In Phase II, BioKyowa A-250 produced better weight gain than the other rations and higher survival then Silver Cup Salmon STarter. In Phase III, fish fed BioKyowa-A gained more weight than fish fed Silver Cup Salmon Starter, and survival of fish fed Biokyowa-A in Phase II remained high (96.7%) in Phase III. Razorback sucker can be raised successfully for 126 days in BioKyowa B0259 is used for the first 25 days, followed by BioKyowa A-250 to day 71 and then BioKyowa A-400 to day 126. Some spinal and muscular deformities were detected in fish fed all diets, presumably due to vitamin deficiencies. These might be reduced by providing extra vitamins or by storing feeds for only short periods.  相似文献   

19.
Indoxacarb is a relatively new pesticide from oxadiazin class, which is used near carp ponds for agricultural purposes. Thus, the aim of this study was to determine indoxacarb effects on common carp (Cyprinus carpio). The fish were exposed to 0 (control), 0.75, 1.5 and 3 ppm of indoxacarb over 21 days and plasma biochemical characteristics and liver histopathology were examined. Exposure to indoxacarb induced fall in total protein after 21 days. Globulin increased after 7 days and then decreased after 14‐ and 21‐day exposure. Plasma alanine transaminase and aspartate transaminase activities increased in 1.5 and 3 ppm treatments after 7‐day exposure. Indoxacarb exposure significantly decreased plasma alkaline phosphatase after 7 days with no change at the second and third samplings. After 7 days, plasma T3 levels had no significant change; however, it decreased after 14 days in the 1.5 and 3 ppm treatments and also reduced after 21‐day exposure to the 3 ppm treatment compared to the control group. Plasma T4 level only decreased significantly in the 3 ppm treatment compared to the control group after 21 days. Different histopathological symptoms such as necrosis, hyperaemia, sinusoidal space extension, pyknotic nuclei, leucocyte infiltration and melanomacrophage aggregates were observed after 21‐day exposure to indoxacarb. The symptoms intensity was dependent on indoxacarb concentration. In conclusion, the present results show that indoxacarb exposure adversely affects common carp health and welfare, which consequently may induce serious problems in this species aquaculture.  相似文献   

20.
Abstract – Understanding the larval ecology of individual fish species is fundamental in ensuring their long‐term conservation. The endangered eastern freshwater cod, Maccullochella ikei, is endemic to the Clarence and Richmond River systems of north‐eastern New South Wales, Australia. Little is known about the behaviour of larval M. ikei in the wild, particularly before and after the swim‐up stage, and following dispersal from the nest site. The aims of this study were to quantify the swimming ability, depth selection, light preference and substrate selection of hatchling to day‐30 M. ikei under controlled laboratory conditions, and to describe its growth and development over the same period. Maccullochella ikei larvae grew constantly but not consistently during the experiment. Exogenous feeding commenced around day 12, prior to the full exhaustion of the yolk. Maximal swimming ability improved daily, but maximum swimming speed declined significantly between days 12 and 13 and remained low. Maccullochella ikei larvae were initially photonegative but were positively phototactic by day 10. Depth selection was for the benthos until day 8, beyond which time larvae dispersed to all depths when released. Substrate selection was for sand in younger larvae but changed to upstream substrates as the experiment progressed. The results of the current study suggest that the period between day 10 and day 20 is critical in the early ontogeny of M. ikei, when it switched phototrophic behaviour, transitioned from endogenous to exogenous feeding and experienced a decline in swimming ability.  相似文献   

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