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1.
Tawny puffer Takifugu flavidus is a species found in China considered to have potential for aquaculture. Experiments were conducted to determine the optimal temperature for its incubation and larval culture. Fertilized eggs collected from cultured broodstocks that were induced to ovulate with a [d ‐Ala6‐Pro9‐Net]‐luteinizing hormone‐releasing hormone analogue were inseminated. The effect of temperature (19, 20, 23, 26 and 29 °C) on the hatch rate, incubation period, viability of 24 h post‐hatch larvae and total mortality rate was assessed. The effect of temperature (20, 23, 26 and 29 °C) on the growth and survival of larvae from 3 to 19 days after hatching (dah) was also assessed. The results showed that the optimal temperature for successful development of fertilized eggs ranged from 23 to 26 °C, and the highest hatch rate, the optimal viability of 24 h post‐hatch larvae and the lowest total mortality rate were all predicted using quadratic equations. The relationship between temperature and the incubation period of tawny puffer eggs was determined using the effective degree‐day model. The temperature at developmental zero (t0) was 11.34 °C, and the sum of effective degree‐days (k) was 52.356. The survival rate of tawny puffer larvae at 20 °C was significantly lower than among 23, 26 and 29 °C, whereas the survival rate was not significantly different from that at 23, 26 and 29 °C. The larval growth rate increased rapidly as the temperature increased, showing a linear relationship in the range of temperatures investigated. The optimal temperature for larval culture ranged from 23 to 29 °C.  相似文献   

2.
The effects of photoperiod and water exchange rate on the larvae of gilthead sea bream, Sparus aurata, from hatching to metamorphosis, 60–70 days later, were tested. Survival, growth rate and condition factor were determined with photoperiods of 12 and 24 h, and water exchange rates of 0 and 25%/day.Continuous light supported the highest mean survival (3.25%), with a maximum of 7.8% from hatching to metamorphosis. Growth rate in dry weight was best under continuous light in a water system with no exchange, up to 20 days post-hatching. Highest growth rates of larvae 40–60 days old were obtained in tanks with 25% of their water exchanged daily, along with a 12-h photoperiod. Condition factor was directly correlated with larval age. For the first 30 days after hatching, condition factor was affected by photoperiod and was highest for larvae exposed to continuous light.  相似文献   

3.
Constant and oscillating egg incubation temperatures on embryonic development and early larval morphology were studied in longfin yellowtail (Seriola rivoliana Valenciennes). We investigated the effects of constant temperatures from 16 to 32°C on embryo development and larval morphology at hatch, and whether oscillating temperature during embryogenesis could lead to larval morphological variations. After hatching, larval morphology and development during yolk sac (YS) utilization were examined in larvae at constant temperatures and larvae at 25°C that had oscillating temperature during egg incubation. Hatching rates were > 75%, only decreasing to ~ 50% at 30°C. At constant temperatures, the largest larvae occurred at 22 and 24°C. The oscillating temperature did not affect the timing of embryo development but resulted in larger and smaller larvae with a smaller and bigger YS, respectively, with a similar hatching time. Therefore, a growth response occurred in embryos during a window of development before hatching, depending on the adaptive response to temperature (spawn‐specific). After hatching, most of the YS was absorbed within 24 hr in all treatments, and the growth of the larval head was a priority with an optimal development at 26°C. There was compensatory growth in smaller larvae resulting in similar sizes after YS utilization, but larvae showed variations in body structure that could be important in further aquaculture research.  相似文献   

4.
Based on the analysis of 11 morphometric variables of body (total length, body area and perimeter, myotome height and eye diameter) and yolk sac (length, height, area, perimeter and volume) of pike larvae, the aim of this study was to evaluate how larval size at hatching and growth of larvae hatched from single egg batches vary according to three hatching times: early, mid and late. Hatching time structures strongly pike larval morphometrics. Early hatched larvae have smaller body sizes at hatch, faster growth and higher yolk use efficiency than late hatched ones. Early hatched larvae seem to be premature and hatch at precocious developmental stage whereas late hatched individuals continue their growth within the egg shell and hatch at larger size but with lower reserves (yolk). A compensatory growth phase was observed for the early hatching pike larvae particularly during the first 5 days post hatch. Consequently, no significant difference in body parameters was recorded from day 10 post hatching whatever the hatching time. The higher growth accomplished by early hatched larvae may be related to a particular metabolic activity that converts more efficiently yolk into body tissues.  相似文献   

5.
大黄鱼仔稚鱼不同发育阶段矢耳石形态发育和微结构特征   总被引：2，自引：0，他引：2  
对人工培育大黄鱼(Larimichthys crocea)的生长发育与矢耳石形态及微结构特征进行研究,结果表明:(1)大黄鱼矢耳石上的轮纹是每日形成的,第1日轮在孵化后第2天形成,与其初次摄食相对应。(2)大黄鱼卵黄囊期和前弯曲期仔鱼的耳石形态为圆形,进入弯曲期耳石长轴迅速伸长,在后弯曲期耳石形态变为椭圆形。进入稚鱼期,矢耳石开始形成次生核。随后次生核数量逐渐增加,在孵化后47～78 d的个体中,次生核数量稳定在5～7个,耳石近似盾形。(3)根据耳石日轮宽度推算的大黄鱼稚鱼在其仔鱼期生长率(b)与第1个次生核的形成时间(tsp1)之间存在明显的线性关系,表明生长较快的个体形成次生核的时间较早,进入稚鱼期所需的时间更短。以上结论表明,大黄鱼矢耳石可以反演其早期生活史阶段的生长发育特征。  相似文献   

6.
The southern flounder, Paralichthys lethostigma, is an important commercial and recreational marine flatfish that inhabits estuaries and shelf waters in the south Atlantic, from North Carolina through the Gulf coasts, with the exception of south Florida. Because juvenile and adult fish are highly euryhaline, it is a prime candidate for aquaculture. Methods for captive spawning of southern flounder are well developed; however, information on optimal culture requirements of the early larval stages is required for reliable mass production of juveniles.To determine the optimal photoperiod and salinity conditions for culture from hatching to day 15 post-hatching (d15ph), embryos were stocked into black 15-l tanks (75 l−1) under four photoperiods (24L:0D, 18L:6D, 12L:12D, and 6L:18D) and two salinities (25 and 34 ppt) in a 4×2 factorial design. Temperature was 18 °C, light intensity was 150 lx, and aeration was 50 ml min−1. Significant (P<0.05) effects of photoperiod and salinity on growth (notochord length, wet and dry weights) were obtained. Growth increased with increasing photoperiod and salinity and was significantly greater at 24L and 18L than at 12L or 6L, and at 34 than at 25 ppt. On d11ph and d15ph, significant interactive effects between photoperiod and salinity on growth (wet and dry weights) were also evident. Growth of larvae reared at 25 ppt increased with increasing photoperiod to a maximum at 24L, while growth of larvae at 34 ppt reached a plateau at 18L. While there were no significant photoperiod effects on these parameters, larval survival, body water percentage, and larval osmolality on d15ph were significantly higher at 34 than at 25 ppt (41% vs. 16% survival; 322 vs. 288 mosM kg−1; and 84% vs. 76% water, respectively), suggesting stress and nonadaptation to 25 ppt, a salinity more nearly isoosmotic than full-strength seawater. Since larvae from both salinity treatments were neutrally or positively buoyant at 34 ppt, but negatively buoyant at 25 ppt, larvae reared at 25 ppt probably allocated energy to maintain vertical positioning, compromising growth and survival.The results demonstrate that growth and survival of early-stage southern flounder larvae are maximized under long photoperiods of 18–24L and in full-strength seawater. Longer photoperiods probably extend the time larvae have for feeding, while full-strength seawater salinity optimizes buoyancy and vertical positioning, conserving energy. The results show that early larval stage southern flounder larvae are not entirely euryhaline, which involves not only the ability to osmoregulate, but to conserve energy under reduced buoyancy. This is consistent with suboptimal vs. maximal growth of larvae reared at 25 and 34 ppt, respectively, under 18L (i.e., photoperiod×salinity interaction). This is also consistent with other reports that tolerance to lower salinities in these euryhaline flatfish increases post-metamorphosis when transition from a pelagic to benthic existence alleviates the need to counteract reduced buoyancy.  相似文献   

7.
Atlantic cod Gadus morhua and haddock Melanogrammus aeglefinus broodstock maintained under altered regimens of temperature and photoperiod spawned up to 8 mo per year. The cod broodstock produced viable embryos from October through June. The haddock broodstock produced viable embryos from December through May. Egg diameters were largest during the middle of the spawning season when water temperature was at a minimum, resulting in an inverse relationship between egg diameter and water temperature in both species. Egg quality was high, as evaluated by buoyancy, fertilization rate, regularity of early cleavage, and percent viable hatch. Low temperature incubation of cod and haddock eggs extended the embryonic period. Cod embryos tolerated a wider range of temperatures than haddock. High mortality (1 90%) was observed before hatching in haddock embryos incubated at 1 C. Atlantic cod embryos hatched at temperatures as low as —1 C, extending the embryonic period to 59 d. At 8 C Atlantic cod and haddock embryos hatched in 11–12 d. To determine if extending the embryo incubation time by using low temperatures had a detrimental effect, embryos were incubated through hatch at either 1 C or 6 C, and the larvae from both groups reared at 6 C. Growth and early survival of larvae were comparable in both treatments.  相似文献   

8.
We carried out an experiment to determine how rapidly the early incubation temperature of Atlantic cod eggs can be increased without affecting normal embryonic development and hatching. Atlantic cod eggs were incubated at a constant low temperature (4.5 ± 0.5°C; T5 – control) and four temperature increment treatments where the temperatures were increased stepwise from 4.5°C at zygote stage to 9.5 ± 05°C (T1‐8 h, T2‐32 h, T3‐64 h and T4‐96 h). Embryonic cell symmetry, embryonic mortality, hatching success and larval skeletal abnormalities, length and yolk sac volume were recorded. Larval samples were also taken at hatch for histological analysis. Except for higher egg mortality and lower hatching success in the T1, the differences among experimental groups were minor. Cell asymmetries and embryo mortalities were not significantly different between the control and T2–T4 treatment groups. Control larvae were significantly longer and had smaller yolk reserves at hatch than T1–T4 larvae and larvae from T2 had the largest yolk reserves. Tissue and organ histology of hatched larvae were similar. Considering embryonic cleavage pattern, hatching success and larval morphology and histology, a gradual increment of temperature in 32 h seems to be the better choice for future developmental programming studies in Atlantic cod.  相似文献   

9.
Blackspot seabream, Pagellus bogaraveo (Brunnich), has been identified as a potential species to diversify European aquaculture production. Although rearing aspects have been widely investigated, little information exists on the nutritional requirements for this species. The aim of this study was to build up information on the activity of digestive enzymes at certain developmental stages of blackspot seabream in order to understand the nutritional needs of larvae and post larvae. Fish larvae were reared from hatching to 55 days after hatching (dah), and the feeding plan consisted in rotifers (5–35 dah), Artemia naupli (30–35 dah) metanaupli (35–45) and Gemma microdiet (45–55 dah). At 7, 11, 21, 45 and 55 days after hatching (dah), pooled samples of fish larvae were collected for analysis of trypsin, amylase, lipase, alkaline phosphatase and leucine–alanine peptidase activity. Up to 21 dah, the whole larvae body was used for enzymatic analysis, whereas in older larvae only the dissected abdominal cavity was used. Blackspot seabream body dry weight growth was exponential, increasing from 60 μg at 5 dah to 30±9.7 mg at 55 dah. Amylase specific activity decreased significantly during development, exhibiting at 11 dah (0.6 U mg?1 protein) an average value 2.7 times lower than at 7 dah, and remaining stable between 45 and 55 dah (0.7 U mg protein?1). Trypsin specific activity remained constant until 21 dah (between 38 and 44 mU mg protein?1), which could be related to the larvae feeding regime. At later stages of development, lipase‐specific activity exhibited a significant increase (P<0.05), being three times higher at 55 dah (8 U mg protein?1) than at 45 dah. The total activity of the studied digestive enzymes increased significantly during larval development (until 21 dah), whereas afterwards only lipase and leucine–alanine peptidase increased significantly between 45 and 55 dah. The pattern of digestive enzymes activity was related to organogenesis and the type of food used at different developmental stages.  相似文献   

10.
Larval size heterogeneity is known to induce cannibalism, and procedures to avoid larval size differences are consequently implemented already during egg incubation and hatching. We investigated the relation between larval development variability, size heterogeneity and cannibalism in pikeperch. Larvae were sorted into five groups according to the time of hatching during a 65‐h period. The larvae with different times of hatch were then reared separately or together during an 18‐day period. Late hatched larvae were longer (P=0.003) and had less yolk remaining (P<0.001) than early hatched individuals at the time of hatching. However, on 11 days post fertilization, the late‐hatching larvae tended to have larger yolk reserves than earlier hatched individuals (P=0.07). Furthermore, the next day, a lower proportion in the late fraction had switched to exogenous feeding (P=0.024). That larvae with a late hatching time developed slower suggests a positive relationship between the hatching time and the embryonic developmental rate. However, differences in the length and available yolk reserves at hatching between larval fractions with different hatching times suggest that hatching is not strictly associated with a specific developmental stage, and that factors other than the development rate of the embryo are involved in the timing of hatching.  相似文献   

11.
为探讨水体pH对龟足(Capitulum mitella)胚胎孵化和幼虫生长发育的影响,采用单因子实验的方法,在水温25-28℃条件下,研究了不同pH(5.0,5.5、6.0、6.5、7.0、7.5、8.0、8.5、9.0、9.5)对龟足胚胎的孵化时间、孵化率和幼虫存活率、变态率的影响.结果表明:pH为5.0时,胚胎不...  相似文献   

12.
The arachidonic acid (20:4n-6,AA) requirements of larval summer flounder weredetermined for the rotifer- and Artemia-feeding stages. Experimental emulsionscontained adequate n-3 highly unsaturated fattyacid (HUFA) ratios and emulsion levels of AAwere set at 0, 3, 6, 9, and 12% (AA0, AA3,AA6, AA9, and AA12). Examination of fatty acidlevels in live feeds and larval tissuesconfirmed the physiological incorporation offatty acids relative to dietary levels. In thefirst experiment, survival, growth, andsalinity tolerance (2-h in 70) were measuredat 18 days after hatch (dah) after feeding thelarvae the various levels of AA. Larvae fedAA6-enriched rotifers were better able tosurvive the salinity tolerance test. AAenrichment up to 12% had no effect on growthand survival. In the second experiment, larvaewere fed AA0- or AA6-enriched rotifers until 23dah, followed by unenriched 24- and 48-h Artemia nauplii until 32 dah. These larvaethen were subdivided and fed AA-enriched Artemia from 33-45 dah. At the end of thisexperiment, larvae fed AA6-enriched rotifershad higher survival, increased growth, andsurvived better in the salinity tolerance test(2-h in 80). The enrichment of Artemiadid not have any effect on these variables.Thus, the provision of AA6-enriched rotifers(10 mg AA g–1 DW) early in larvaldevelopment may serve to enhance larval stresstolerance at the rotifer stage while alsoincreasing larval survival, growth, and stresstolerance later in the Artemia stage.  相似文献   

13.
Eggs of European hake (Merluccius merluccius L.) were stripped from fish caught at sea. Larvae were kept under semi‐intensive conditions at around 12°C. In addition, eggs were incubated in single wells at 9.2, 12.7 and 14.5°C, where hatching, development and survival were closely examined. During the larval stage, a total of 299 larvae were sampled to follow development and growth. In addition a small number of juveniles were sampled. Larvae hatched approximately 4 days after fertilization, and were 2.9 mm in total length (TL). At 6‐day post hatching (dph), the larvae were 4.1 mm (TL), the jaw apparatus was developed, and the larvae had started to feed. Most of the growth during the early larval period is restricted to the head, and there is almost no increase in length for the first 3–4 weeks post hatching. Teeth and pelvic fins appear at 25 dph. Development of unpaired fins at approximately 30 dph marks the start of the larval–juvenile transition. Weaning to formulated feed was accomplished 50 dph, when external morphology was similar to that of adult hake.  相似文献   

14.
Populations of the coconut crab, Birgus latro, have been severely depleted on most inhabited islands throughout the Indo‐Pacific regions because of overharvesting and environmental degradation. To assist in the development of artificial propagation technologies for supportive breeding programmes in conserving this species, this study was designed to elucidate the effect of photoperiod on the survival, developmental period of zoeae and body size of megalopae through laboratory experiments. We tested six light (L) and dark (D) photoperiod regimes times of 0–24 h, thus 0L:24D, 6L:18D, 12L:12D, 18L:6D and 24L:0D. Photoperiod conditions significantly affected larval survival. Survival was lower in the 0L:24D condition than in other photoperiod conditions, reflecting higher mortality during the zoeal stage in the 0L:24D condition. On the other hand, survival rates were high during the periods when larvae metamorphosed into megalopae, regardless of photoperiod conditions. In the 24L:0D condition, larval survival rate was slightly lower than in other conditions containing a light phase. Zoeal duration and megalopal body size were not different in light durations ranging from 0 to 18 h, but they were longer and larger, respectively, in the 24L:0D condition. Thus, continuous dark or continuous light conditions impaired the survival and development of larvae, and such photoperiod regimes should be avoided for culturing larvae of the coconut crab.  相似文献   

15.
异沟虫是红鳍东方鲀常见寄生虫之一,对红鳍东方鲀养殖业危害极大。为有效防治异沟虫病,在观察异沟虫虫卵孵化规律的基础上,研究评价福尔马林药浴对异沟虫的杀灭效果及其对红鳍东方鲀的安全性,形成红鳍东方鲀异沟虫病的防治方案。试验结果发现,异沟虫虫卵的孵化过程大致可分为孵化初期、孵化中期、孵化后期和破卵4个阶段,在17~19 ℃条件下,异沟虫虫卵5.5 d孵化出幼虫,8 d孵化结束;不同大小的异沟虫对福尔马林的耐受性有明显差异,当福尔马林剂量为600 mL/m 3 时,浸浴1 h可杀灭全部异沟虫幼虫(体长≤1 cm),但对异沟虫成虫(体长>1 cm)几乎无效;在600 mL/m 3 福尔马林浸浴条件下,红鳍东方鲀在浸浴后第5 h开始出现游动异常、呼吸困难等现象,在浸浴后第6 h出现死亡;而在650、700 mL/m 3 福尔马林浸浴条件下,红鳍东方鲀分别在浸浴后第5.5 h和4 h出现死亡。综上,体质量约为20 g的红鳍东方鲀异沟虫病的建议防治方案为600 mL/m 3 福尔马林溶液浸浴1 h,8 d后重复药浴1次。  相似文献   

16.
黄海  杨宁  张希 《南方水产》2012,8(2):43-50
在（28±1）℃条件下对马拉瓜丽体鱼（Cichlasoma managuense）仔鱼进行饥饿试验,确定仔鱼的不可逆点（PNR）,并研究延迟投饵对仔鱼成活和生长的影响。结果显示,仔鱼在4日龄时开口摄食,进入混合营养期,持续3 d;7日龄时卵黄囊消失,进入外源营养期。初次摄食率开始时仅为15%,6日龄时的初次摄食率最高达100%,9日龄以后初次摄食率急剧下降,PNR出现在仔鱼孵出后第9至第10日龄。延迟投饵1～3 d对仔鱼的成活率影响不大,延迟投饵4 d以上仔鱼成活率明显下降。完全饥饿条件下仔鱼全长在0～8日龄为正增长,之后开始转为负增长。延迟投饵1～3 d的12日龄仔鱼全长无显著差异（P〉0.05）;延迟投饵超过4 d的仔鱼全长则有极显著差异（P〈0.01）。马拉瓜丽体鱼仔鱼的最佳投喂时间应在仔鱼开口后的3 d之内。  相似文献   

17.
The effects of four light intensities on growth and survival of first‐feeding stage black sea bass larvae Centropristis striata were investigated in a controlled‐environment laboratory. Fertilized eggs, obtained from LHRHa‐induced spawning of captive broodstock, were stocked (72 eggs L?1) into twenty 15 L black tanks under light intensities of 100, 500, 1000 and 1500 lx, with five replicate tanks per treatment. The photoperiod was 12L:12D, the temperature was 20°C and the salinity was 35 g L?1. Larvae were fed rotifers Brachionus rotundiformis from day 2 post‐hatching (d 2ph) at 5–10 rotifers mL?1. Microalgae Nannochloropis oculata and Isochrysis sp. were added (1:1) daily to maintain a density of 300 000 cells mL?1. Hatching success and larval growth and survival from d 2ph through d 15ph were monitored. Hatching success was 28–38% under all light intensities, and notochord length at hatching ranged from 2.8 to 3.0 mm, with no significant differences among treatments. By d 15ph, growth (mg wet weight) was significantly higher in the 1000 lx (0.914) and 1500 lx treatments (0.892) than in 100 lx (0.483), and a highly significant trend (P<0.01) towards increased survival with increasing light intensities was observed, from 1.3% at 100 lx to 13.9% at 1500 lx. Higher light intensities within the range of 100–1500 lx improved growth and survival of early larval black sea bass, suggesting that even higher light intensities may improve culture performance. This is consistent with conditions in shallow, near‐shore locations where eggs and larvae are distributed in nature.  相似文献   

18.
NORIYUKI  HORIE  TOMOKO  UTOH  YOSHIAKI  YAMADA  AKIHIRO  OKAMURA  HUAN  ZHANG  NAOMI  MIKAWA  ATSUSHI  AKAZAWA  SATORU  TANAKA  HIDEO P  OKA 《Fisheries Science》2002,68(5):972-983
Development of embryos and larvae in the common Japanese conger Conger myriaster was observed after artificial fertilization. Eggs were obtained from females matured artificially by hormone injections and milt was obtained from males matured naturally. Fertilized eggs were kept in seawater at 12–14°C. The first cleavage occurred at 4 h, epiboly began at 24 h, the embryonic body was formed at 38 h and hatching occurred at 84 h after insemination. Newly hatched larvae were approximately 2.5 mm (total length) and similar to those of Anguilla japonica in terms of external features. The mouth and anus opened on the 7th day after hatching. Pigments began to appear at the tip of the tail on the 10th day. The total length of the larvae reached approximately 8 mm on the 11th day. Eye pigmentation began on the 14th day. One larva lived for 19 days without food.  相似文献   

19.
Several samples of P. splendida larvae were obtained from eggs until day 60 after hatching (dah) to determine acid and alkaline proteases, trypsin, chymotrypsin, leucine aminopeptidase, α-amylase, lipase, and acid and alkaline phosphatase activities using biochemical techniques. Additionally, SDS–PAGE alkaline protease zymogram and PAGE acid protease zymogram were carried out to identify active isoforms during larviculture. Alkaline protease and chymotrypsin were present at the moment of hatching, increased gradually reaching the maximum values at 35 dah. Trypsin and leucine aminopeptidase activities were low from hatching, increasing gradually as larvae grew. Alkaline protease zymogram showed four zymogens, which appears at different days, remaining present until the end of the larviculture (95.2 kDa at 11 dah, 26.4 kDa at 9 dah, 21.4 kDa at 3 dah, and 23.3 kDa at hatching). Pepsin activity was present at day 7 after hatching and increased progressively until the end of the larviculture. Acid protease zymogram only showed one zymogen (0.65 rf), which appear at 6 dah. Lipase was high at the time of hatching and increased until 15 dah, after which decreased gradually. Amylase was high from the beginning and until 15 dah and then decreased rapidly to almost nothing onward. Alkaline and acid phosphatases presented a high activity at the egg stage, fell slightly during the first feeding and increased again from 20 to 30 dah. Results obtained in this study show that larvae can be fed artificial diets starting on day 10 after hatching.  相似文献   

20.
盐度对暗纹东方鲀胚胎发育的影响   总被引：2，自引：0，他引：2  
杨州  华洁  陈晰 《齐鲁渔业》2004,21(9):3-5
研究了不同盐度对暗纹东方鲀胚胎发育的影响，盐度为4和8的试验组中受精卵的发育历期、孵化率及初孵仔鱼24小时的存活能力和淡水相比均无显著差异。在盐度12及以上，绝大部分受精卵死亡，仅有极少数个体孵化出膜，且全为畸形并都在24小时内死亡；发育速度随着盐度的升高而变慢。因此，暗纹东方鲀胚胎正常发育所能耐受的盐度范围是0～8。  相似文献   

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