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1.
Striped bass, Morone saxatilis (Walbaum), larvae, although physoclistous as adults, initially need to inflate their swimbladders by passing ingested air through a pneumatic duct to the swimbladder. Failure to inflate the swimbladder results in swimbladder atrophy, dysfunctional buoyancy control, deformities, and poor larval survival and growth. The present investigation studied the effects of light intensity, tank colour and photoperiod on the initial swimbladder inflation success of striped bass. In the first experiment, newly hatched larvae were reared for 2 weeks in black or white 350-L circular tanks exposed to incandescent lighting at 163 or 10 lux. Larvae were fed Artemia from 6 days post-hatching (dph). The standard length, and oil globule and yolk areas were measured. Swimbladder condition and evidence of feeding were recorded. To study the effects of photoperiod on inflation, larvae were reared in black tanks exposed to either 8 h:16 h or 16 h:8 h light:dark photoperiods at 139 lux. Striped bass inflated their swimbladders between 6 and 9 dph at 17 oC. Inflation success was significantly higher in black tanks (65%) compared with white tanks (42%), but light intensity did not significantly affect swimbladder inflation. Larval growth and food consumption were better in black tanks, primarily because this treatment resulted in more larvae with inflated swimbladders, although larvae with uninflated swimbladders in black tanks were longer at 12 dph than larvae with inflated swimbladders in white tanks. Larvae that successfully inflated their swimbladders fed earlier and exhibited better growth than larvae with noninflated swimbladders. Larvae reared at higher light intensities used up yolk reserves faster. Exposing striped bass larvae to 8 h:16 h light:dark photoperiods resulted in higher inflation rates (55%) compared to larvae reared at 16 h:8 h light:dark photoperiods (30%). Therefore, black tanks and short photoperiods are preferable for early rearing of striped bass larvae to maximize swimbladder inflation success.  相似文献   

2.
Weaning marine fish larvae from live prey to a dry microdiet is an important step towards optimizing the commercial production, but early weaning is constrained by the lack of sufficient digestive enzymes at first feeding. This study quantified the activity of five digestive enzymes throughout the larval period of pigfish (Orthopristis chrysoptera [L.]) to assess ontogenetic changes in digestive abilities, and then trials were conducted that determined the optimal time for weaning. The activity of all digestive enzymes was low or undetectable at first feeding (3 days post hatching, dph; 2.5 mm standard length, SL). A substantial increase in activity occurred at 5.7 mm SL (17 dph), 6.9 mm SL (21 dph), 7.7 mm SL (23 dph), 8.4 mm SL (25 dph) and 11.2 mm SL (30 dph) for bile salt‐dependent lipase, trypsin, chymotrypsin, amylase and acid protease respectively. During the weaning experiment, larvae were co‐fed live prey and microdiet beginning 15 dph (4.8 mm SL). Live prey was withdrawn from the diet at 24, 28, 32 or 36 dph, with the control receiving live prey and microdiet throughout (to 43 dph). There were no significant differences in mean final SL among treatments, but survival was significantly lower when larvae were weaned at 24 dph compared to 32–43 dph. Based on the digestive enzyme activity and survival, weaning larval pigfish at 32 dph (11.7 mm SL) when reared at 24°C is recommended.  相似文献   

3.
Success of swim bladder inflation (SBI) is crucial for early survival of Pacific bluefin tuna (PBF) larvae, because it reduces larval sinking death by enhancing buoyancy. In Experiment 1, we examined the effect of photoperiod on SBI and survival in PBF larvae by comparing photoperiods of 9L: 15D (9L), 14L: 10D (14L: natural photoperiod), 19L: 5D (19L) and 24L: 0D (24L) during 2–10 days post hatch (dph). In Experiment 2, the combined effects of photoperiod (24L and 14L) and nighttime aeration rate (enhanced night‐time aeration: ENA of 1300 mL min?1 as a countermeasure for sinking death and 130 mL min?1) on the survival and SBI were also examined during 2–10 dph. Moreover, in Experiment 3 the effect of photoperiod on vertical distribution of larvae in night‐time was examined on 3–5 dph. Photoperiod of 24L in Experiment 1 significantly inhibited SBI compared with 14L and 19L; nevertheless, it significantly improved survival compared with other photoperiods with a dark period. On the other hand, the shortened light period (9L) showed significantly reduced SBI and also survival. In Experiment 2, the countermeasure for sinking death of ENA under 24L did not further improve the survival; rather it tended to reduce the survival. In Experiment 3, larvae distributed less in the bottom layer in 24L than in 14L, suggesting the reducing effect of 24L on sinking death. The results indicate that 24L without ENA is suitable for survival which is the most serious problem in PBF larviculture.  相似文献   

4.
The effects of two weaning diets and different weaning protocols on growth, survival, skeletal deformity and gut morphology of Atlantic cod larvae were studied in four groups from 16 to 45 days posthatch (dph). Cod larvae in groups 1 (early weaning with control diet) and 2 (early weaning with experimental diet) were used to evaluate the effects of different polar lipid content of weaning diets on larval and juvenile performance. Cod larvae in groups 2, 3 (early weaning with experimental diet + cofeeding with Artemia) and 4 (earlier weaning with experimental diet and earlier cofeeding with Artemia) were used to evaluate the effects of early introduction of dry diet and Artemia. From 45 to 170 dph, cod juveniles from all four groups were reared using a standard feeding protocol. No significant differences in growth, survival, deformities and gut morphology were found between cod larvae and juveniles from groups 1 and 2. Cod larvae fed on cofeeding regime with Artemia nauplii (groups 3 and 4) were bigger and had lower frequencies of jaw and neck deformities and higher foregut microvillus circumference than cod larvae from group 2. Our results demonstrate the importance of proper weaning protocols in producing better quality cod juveniles.  相似文献   

5.
Systemic granulomatosis is the most frequent disease in juvenile and adult meagre, but studies regarding the first appearance of granulomas in larvae do not exist. In order to evaluate this, meagre larvae were fed four different feeding regimes as follows: RS and RO (rotifer enriched with Easy DHA Selco or Ori‐Green from 3 to 30 dph respectively), RAS and RAO (rotifer enriched with Easy DHA Selco or Ori‐Green from 3 to 21 dph and Artemia enriched with Easy DHA Selco or Ori‐Green from 12 to 30 dph respectively). All treatments were also fed with commercial microdiet from 20 to 30 dph. At 30 dph weight, length, specific growth rate and survival were significantly higher in Artemia‐fed larvae, regardless of the enrichment. Microscopic first appearance of granulomas was observed in 20 dph larvae fed RS and RO. At 30 dph granulomas and thiobarbituric acid reactive substances (TBARS), values were significantly higher in RS and RO‐fed larvae than in RAS and RAO‐fed larvae. The results showed that granulomas first appeared in meagre larvae at 20 dph when fed rotifers only. Conversely, a reduced appearance of granulomas and lipid peroxidation occurs when Artemia is included in the feeding sequence reinforcing the hypothesis of a nutritional origin of the systemic granulomatosis.  相似文献   

6.
The study investigated the combined effect of weaning from live feed to a commercial dry pellet at 10, 15, 20, 25 or 30 days posthatching (dph) and co‐feeding for 1, 3 or 6 days on survival and growth of Coregonus peled larvae. Additional groups fed only live Artemia sp. nauplii (ART), and only Biomar LARVIVA ProWean 100 (DRY) were included. A final survival rate of 66.4%–85.5% was observed in groups weaned after 20 dph. Final body weight (BW) and total length (TL) were significantly lower in groups weaned at 10 and 15 dph, regardless of the duration of co‐feeding. Larvae reached 29–37 mg BW and TL of 17.7–19.0 mm in groups weaned at 20, 25 and 30 dph. The recommended minimum duration of feeding with live food, based on these results, is 20 days. Based on the significantly higher yield of larvae weaned after 20 dph irrespective of co‐feeding duration, it can be concluded that abrupt weaning to dry food after 20 days of feeding with live prey can provide adequate production while reducing the effort and costs associated with live feed.  相似文献   

7.
There is considerable interest in rearing Southern flounder, Paralichthys lethostigma, for commercial production and for stock enhancement. Both goals depend upon excellent larval nutrition for the production of robust juveniles. The current use of live prey for larviculture is an expensive and time consuming process that can be alleviated by weaning larvae onto dry feed. A study was conducted to assess the potential for early weaning of southern flounder larvae onto a microdiet (MD). In addition, the activity of selected digestive enzymes was measured during ontogeny to evaluate the digestive capabilities of the larvae over time. Pancreatic enzyme activities (U larva− 1) were very low or undetectable at hatching and a marked increase in activity was not observed until the larvae reached 4 mm (~ 11 dph) in standard length for chymotrypsin (24–44,000) and 6 mm (~ 25 dph) for amylase (< 1–24), trypsin (1–18) and bile salt-dependent lipase (0–443). Acid protease activity (~ 1.0) was detected once the larvae were 8.5–9.0 mm (37–39 dph) in length although a sizeable increase in activity (> 10.0) was not observed until after complete metamorphosis (> 11.0 mm; 40–45 dph). Feeding regimes employed for the weaning study consisted of a live feed control (C) and a combination of live feed and MD in which the addition of the MD was initiated on 11 dph and live feed terminated on 17 (T17), 23 (T23) or 29 (T29) dph. At the end of the study (35 dph), mean standard length and the percent of settled fish were significantly greater for fish in the control treatment (8.3 mm; 21.1%) than for fish fed any combination of live prey and MD (6.4 mm; 2.0%). Average survival was 27.7% and no significant differences were noted among treatments. However, the number of fish exhibiting spinal deformities, lordosis, was significantly lower in the control and T29 treatments (1.7%) than the T17 and T23 treatments (25%). The results of this study indicate that southern flounder larvae readily wean onto dry feed prior to the onset of metamorphosis. However, decreased growth and a high incidence of lordosis emphasize the need for the development of a more appropriate MD for this species when digestive enzyme activities are relatively low and gastric digestion is absent.  相似文献   

8.
In hatcheries, meagre Argyrosomus regius larvae still depend on an adequate supply of rotifers and Artemia, as no artificial diet can totally fulfil their nutritional requirements. However, production of live feed is highly expensive and demands intensive labour and specific facilities. This study investigated the effect of a dietary regime without the use of rotifers, to simplify the meagre larval rearing protocol. Two feeding treatments (T1 & T2) are compared to investigate their effects on survival and growth of meagre larvae. In T1, larvae were fed rotifers from 2 to 5 days post hatch (dph), and Artemia from 4 to 15 dph. In T2, larvae were kept under dark conditions and fed Artemia from 6 to 15 dph. Standard larval length (SL) was significantly higher in T1 (p < .01) until 8 dph in comparison with larvae reared initially without rotifers. No significant difference in SL was found among treatments (p = .187) at 15 dph. Significant difference was found among treatments in survival rate at 15 dph (p < .003). The survival rate observed at 15 dph in T2 (30 ± 4.2%) represents an important finding, although the highest survival rate was observed in T1 (45.0 ± 3.4%). This study showed that it is possible to conduct larval rearing of meagre without using rotifers. Nevertheless, further research efforts are still needed to improve these results in comparison with the common larval rearing protocol.  相似文献   

9.
To evaluate the nursery value of the estuarine turbidity maximum (ETM) for the anadromous engraulid fish Coilia nasus, physical and biological samples were collected along the macrotidal Chikugo River estuary, southwestern Japan, from June 2005 to January 2006. Generally, eggs were distributed upstream of the ETM, whereas larvae were distributed in the ETM. The first cohort was washed out of the estuary by a large flood in early July. The second cohort appeared after the flood, gradually extending its distributional area through the estuary and growing to 100 mm in standard length (SL) by December. Larvae and juveniles (20–100 mm SL) fed selectively on copepods, specifically large calanoid species, whereas more developed juveniles fed on mysids. Prey organisms in guts were significantly more abundant and present in greater weights in the ETM (salinity <10) than in the lower estuary (salinity >10). The better feeding conditions were primarily attributable to consistently high densities of two large calanoid species, Sinocalanus sinensis and Pseudodiaptomus inopinus, in the ETM. In contrast, the poor feeding conditions in the lower estuary were likely due to a seasonal decrease in copepod density and the dominance of small copepods such as Oithona spp. Given that better feeding conditions contribute positively to the growth and survival of larvae and juveniles, we conclude that the ETM has a significantly higher nursery value for C. nasus compared with other habitats in the Chikugo River estuary.  相似文献   

10.
The effects of weaning strategies of cobia (Rachycentron canadum L.) larvae to commercial microdiets, either from rotifers or from Artemia, on growth, survival and enzymatic digestive capacity, were investigated. In the first experiment, cobia larvae were weaned from rotifers by co-feeding with a microdiet (Otohime) from 8, 13 or 20 days post-hatching (dph). The larvae in the control treatment were fed rotifers (2–12 dph), Artemia nauplii from 7 dph, and co-fed with the microdiet from 20 dph. In the second experiment, the larvae were weaned from Artemia, which was fed to the larvae from 7 dph, by co-feeding with a microdiet (NRD) from 8, 13 or 18 dph. The larvae in control treatment were fed rotifers, then Artemia to the end of the experiment (28 dph). Weaning of cobia larvae onto a microdiet directly from rotifers significantly reduced growth, survival and digestive capacity of the larvae and did not lead to larval acceptance of the microdiet, compared to those weaned from Artemia in the first experiment. Early weaning of cobia larvae onto NRD microdiet (on 8 or 13 dph) from Artemia in the second experiment also reduced growth, survival rate and gut maturation index, compared to those fed live feed. With available microdiets, weaning of cobia larvae could start from Artemia at around 18 dph in order to obtain comparable growth, survival and gut maturation to larvae fed live feed.  相似文献   

11.
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12.
The shortfin silverside Chirostoma humboldtianum has been considered for culture in Mexico, but success has been limited by a poor knowledge of its early development. First synthesis of the early development of the shortfin silverside is presented to determine conditions suitable for rearing. Brooder maturation was induced through photothermal cycles. C. humboldtianum ova were fertilized in vitro. The eggs were incubated in reconstituted water (160-180 mg/L CaCO3) at 18 °C and 5 gm of NaCl per litre. During the hatching day, 300 shortfin silversides were stocked and followed up until metamorphosis in order to establish the timing of exogenous feeding, changes in food type, growth and development during critical periods for survival, according to the theory of saltatory ontogeny. Free embryos hatched 12 days after fertilization at 18 °C. First critical point for survival is the beginning of exogenous feeding. Free embryos started mixed feeding on day four of post-hatching (dph), point of no-return was presented towards the end of mixed feeding on 6 dph, larval period began at six (dph) when the anus is opened, and metamorphosis to juvenile was presented at 65 dph with a SL of 19.34 ± 2.28 mm, when scales and fins were well developed. Differences in growth between periods were detected: free embryos growth slower than larvae but mouth size depicted a larger growth rate in the former. Cephalic length and mouth size were negatively related to standard length in embryos and larvae. Mouth size was positively related to cephalic length in free embryos but negative in larvae. Results suggest that during the free embryo phase, growth priorities are directed to the development of apparatuses and systems; whereas, during the larval period, energy is directed to growth in length, mouth size and development of fins, which allows them to increase their swimming velocity, grants them a greater capacity to obtain exogenous food and, in consequence, increases fitness for survival.  相似文献   

13.
The aim of this study was to compare the nutritional composition and effects of short periods with cultivated copepod nauplii versus rotifers in first‐feeding. Atlantic cod (Gadus morhua) and ballan wrasse (Labrus bergylta) larvae were given four different dietary regimes in the earliest start‐feeding period. One group was fed the copepod Acartia tonsa nauplii (Cop), a second fed enriched rotifers (RotMG), a third fed unenriched rotifers (RotChl) and a fourth copepods for the seven first days of feeding and enriched rotifers the rest of the period (Cop7). Cod larvae were fed Artemia sp. between 20 and 40 dph (days posthatching), and ballan wrasse between 36 and 40 dph, with weaning to a formulated diet thereafter. In addition to assessing growth and survival, response to handling stress was measured. This study showed that even short periods of feeding with cultivated copepod nauplii (7 days) had positive long‐term effects on the growth and viability of the fish larvae. At the end of both studies (60 days posthatching), fish larvae fed copepods showed higher survival, better growth and viability than larvae fed rotifers. This underlines the importance of early larval nutrition.  相似文献   

14.
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15.
This study investigated the influence of initial swimbladder inflation (ISI) failure on survival of Pacific bluefin tuna (PBT), Thunnus orientalis, larvae to prevent mass mortality due to sinking death. In Experiment 1, swimbladder inflation frequency and survival within an ISI promoted (PS) group, for which surface film of rearing water was removed, and a group without ISI promotion (NPS) were compared in 20 and 30 kL tanks. The PS group demonstrated significantly higher swimbladder inflation frequency and increased survival than the NPS group within 20 kL tanks at 9 days post hatching (dph). Similar tendencies were observed within 30 kL tanks. In Experiment 2, larval distribution and swimbladder inflation frequency in the night‐time were examined through larval sampling within the upper and middle layers of the water column and tank bottom within 1.6 and 30 kL tanks at 5 dph. Larvae at tank bottom had higher distributional density and significantly lower swimbladder inflation frequency than those distributed in the upper and middle layers within 1.6 kL tanks. Similar tendencies were observed within 30 kL tanks. Results of this study suggest the improvement of larval survival due to prevention of sinking death through ISI promotion in mass‐scale PBT larviculture.  相似文献   

16.
In cultured juvenile Pacific bluefin tuna (Thunnus orientalis), reducing the mass deaths caused by collision or contact with tank or net walls at night is a priority for seedling production. Pacific bluefin tuna is a visually dependant species, although its scotopic vision is poor. We recorded electroretinograms to investigate the visual function with growth in the dark-adapted eyes of juvenile Pacific bluefin tuna. Peak wavelengths of spectral sensitivity [38–62 days posthatch (dph), 77–167 mm standard length (SL)] were observed between 474 and 494 nm. Visual light sensitivity has a tendency to increase slightly with growth at 28–64 dph in individuals that measured 29–175 mm SL. However, visual temporal resolution did not significantly increase with growth at 38–62 days dph in individuals that measured 77–167 mm SL. These results suggest that the mass death continues between 28 and 64 dph because of low visual function and increasing swimming speed with growth.  相似文献   

17.
The concept of nutritional programming raises the interesting possibility of directing specific metabolic pathways or functions in juvenile fish, for example, to improve the use of substitutes to fishmeal and oil, and hence to promote sustainability in aquaculture. The aim of the study was to determine effects of early nutritional stimuli of gilthead seabream larvae and check if nutritional programming of gilthead sea bream is possible between 16 days post hatching (dph) and 26 dph. A trial was conducted to determine the effects of early nutritional stimuli of gilthead seabream larvae. Five experimental microdiets (pellet size <250 μm) were formulated containing five different proportions of a marine lipid source rich in long‐chain polyunsaturated fatty acids (LC‐PUFA) and two vegetable lipid sources rich in linolenic and linoleic acids. The results of this study demonstrate that dietary n‐3 LC‐PUFA levels increased larval growth and survival affecting Δ6 desaturase gen (fads2) expression and retinal neurons density. However, the high mortalities obtained along on‐growing in fish fed low n‐3 LC‐PUFA at 16 dph constrained the feasibility of nutritional programming of gilthead seabream during this late developmental window and needs to be further investigated.  相似文献   

18.
The growth and morphological development including fins, spine distribution and pigmentation of larval and juvenile of hatchery‐reared yellow puffer, Chonerhinos naritus were described to provide essential information on the early life history of this species. The total length (TL) of newly hatched larvae was 3.42 ± 0.23 (mean ± SD) mm, reaching 5.66 ± 0.38 mm on 5 days after hatched (DAH), 7.80 ± 0.28 mm on 11 DAH, 9.88 ± 0.40 mm on 27 DAH and 10.92 ± 0.58 mm on 30 DAH. The yolk was completely absorbed in preflexion larvae at 4 DAH. The mouth opening started at 3 DAH of yolk sac larvae, while the teeth appeared starting from preflexion larvae at 7 DAH. Overall aggregate fin ray numbers including caudal fin attained full complement in postflexion larvae at 27 DAH. Several melanophores with appearance of small stellate were first appeared dorsally on the head of flexion larvae at 13 DAH, expanded at the dorsal region of the head, above the eye in juveniles at 30 DAH. The spines first appeared in preflexion larvae of C. naritus at 7 DAH, covering the ventral skin region below pectoral fin base and expanded to the ventral part of the body and nearly covered the whole abdomen region before the anus and below the eyes in juveniles. C. naritus remain as larvae for approximately 29 days, during which they metamorphose to the juvenile stage prior to sexual maturation. Observations in larvae development of C. naritus revealed similar characteristics with other Tetraodontidae species.  相似文献   

19.
This study investigated the optimal timing of day to promote initial swimbladder inflation (ISI) for improved Pacific bluefin tuna (PBT), Thunnus orientalis, larval survival. Larval swimbladder inflation frequency was compared based on three experiments using different time schemes of surface film removal (SFR) from 3 to 9 days post hatch (dph). SFR was conducted from 05:00 to 19:00 hours (light period: S.5–19), 19:00 to 05:00 hours (dark period: S.19–5), 08:00 to 19:00 hours (S.8–19) and the entire day (S.24) in Experiment 1; from 08:00 to 19:00 hours (S.8–19‐E2), 08:00 to 13:00 hours (S.8–13), 13:00 to 19:00 hours (S.13–19) in Experiment 2; and from 13:00 to 16:00 hours (S.13–16), 16:00 to 19:00 hours (S.16–19), 18:00–19:00 hours (S.18–19) in Experiment 3. The swimbladder inflation frequency at the experiment termination (9 dph) was significantly higher (P < 0.001) in S.24 (91.1 ± 5.7%), S.5–19 (92.2 ± 5.1%) and S.8–19 (93.3 ± 3.4%) than in S.19–5 (11.1 ± 5.1%) in Experiment 1, and remarkably higher in S.8–19‐E2 (81.7%) and S.13–19 (88.3%) than in S.8–13 (0.0%) in Experiment 2, and significantly higher (P < 0.001) in S.16–19 (84.4 ± 5.1%) and S.18–19 (70.0 ± 12.0%) than in S.13–16 (7.8 ± 3.9%) in Experiment 3. These results suggest that the optimal timing to promote larval ISI by SFR is a few hours before the end of light period (16:00–19:00 hours) from 3 to 9 dph.  相似文献   

20.
Allometric growth and ontogeny were studied in thick‐lipped grey mullet Chelon labrosus reared in mesocosms from 1 to 71 day post hatching (dph). Multivariate allometric analysis of morphometric growth distinguished three distinct developmental stanzas separated by two morphometric metamorphosis lengths (Lm1 = 4.46 ± 0.06 mm; Lm2 = 28.56 ± 1.04 mm). Body mass growth also showed three distinct episodes separated by two inflections, correlated with morpho‐functional changes. First episode concerned pre‐flexion larvae and ended around 4.5 mm‐LT (14‐dph), coinciding with estimated Lm1. It was distinguished by reduced growth, but intense morphogenesis and differentiation processes. Organogenesis and allometric changes indicated that development priorities concerned feeding efficiency, by improving detection ability (sensory system development), ingestion capacity (head growth) and assimilation performance (digestive system differentiation), together with respiration efficiency (gill development). Second episode concerned post‐flexion larvae and, ended around 8.6 mm‐LT (25‐dph). It was distinguished by fast growth of trunk and tail, acquisition of adult axial muscle distribution and completion of gill filament development, improving locomotion and oxygenation performances. It corresponded to transition towards metamorphosing stage as indicated by later isometric growth, musculature maturation and acquisition of juvenile phenotype. Metamorphosis seemed to end at Lm2, suggesting to avoid zootechnic handling before this size.  相似文献   

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