Effect of supplementation of a dry feed with natural food on growth, condition and size distribution of juvenile tench Tinca tinca (L.)

In a 120‐day experiment, tench Tinca tinca juveniles [initially, 135 days post‐hatch, 37.4 mm total length (TL), 0.51 g body weight (BW)] maintained at 28°C received commercial starter alone (control group) or together with a supplement of frozen fly or chironomid larvae, in single or double quantities. Final survival rates were 100% in all treatment groups. Double additives significantly (P ≤ 0.05) improved fish growth in TL (final growth 62.0 or 62.5 mm, respectively) as compared with those fed single quantities (both 60.8 mm) or starter alone (59.1 mm). Significant differences in BW were found only between groups fed double additives and starter alone (final growth 2.96–3.07 and 2.71 g, respectively). Significantly highest Fulton's coefficient values were found in the control group and in the group fed single supplement of fly larvae (both K = 1.22), and lowest in both groups receiving chironomid larvae (K = 1.15–1.17). BW distribution was positively asymmetric in all groups, and the distribution of TL only in the control group and in the group fed with the single supplement of chironomid larvae. From a practical point of view, supplementation of a commercial starter with insect larvae has a minor effect on the results of T. tinca rearing under controlled conditions.     

Effects of feeding rate on the growth performance of gynogenetic albino sterlet,Acipenser ruthenus (Linnaeus, 1758) larvae

The feeding rate effects were studied on the growth performance of gynogenetic diploid larvae of sterlet Acipenser ruthenus during the first 4 weeks of exogenous feeding. The experimental rearing was conducted from 7 to 38 days post‐hatch (dph) in a circulation system. This was set up in four groups with three replicates (440 individuals/replicate), viz: AC‐control larvae fed Artemia sp., CFC‐control larvae fed compound feed, AG‐gynogenetic larvae fed Artemia sp., and CFG‐gynogenetic larvae fed compound feed. The larvae were reared in glass tanks (44 L volume, 10 individuals/L) with the temperature maintained at 18 ± 0.5°C, photoperiod of 12L:12D and water flow regime of 1‐L/min and fed 50%, 25%, 25%, and 9% of their total biomass/day during feeding. Highest TL and WBW of gynogenetic diploid larvae (AG) were observed with 50.6 ± 1.2 mm and 607.3 ± 36.1 mg (n = 30) at 38 dph. Highest TL and WBW of control larvae (AC) were recorded with 49.5 ± 3.8 mm and 600.8 ± 88.0 mg (n = 30), respectively, with 73.1% ± 11.4% survival; the lowest survival rate was at 46.4% ± 7.1% (n = 30) for the CFG group. The results indicate that the gynogenetic and normal larvae of sterlet fed with live food (Artemia nauplii) from 7 dph can achieve higher growth and survivability compared to the larvae fed with formulated test feed. Results of this study suggest that the effective rearing of sterlet larvae from 7 to 38 dph strongly depends upon the types of feed rather than the genome manipulation performed.     

微流水培养条件下斑鳜仔鱼的摄食与生长

在孵化环道连续微流水培养、水温(24±2)℃条件下,斑鳜(Siniperca scherzeri Steindachner)初孵仔鱼全长为(4.87±0.10)mm(n=50),卵黄囊体积为(1.461±0.172)mm3(n=50),油球直径为(0.47±0.04)mm(n=50).仔鱼孵出12h,胸鳍增大,具有一定阵发性水平游动能力,1日龄巡游模式建立;2日龄口膜消失,开始主动摄食,进入混合营养期,3 日龄外源性摄食关系完全建立.5日龄仔鱼的卵黄和油球全部消失.进入外源营养期;15日龄全长达到(13.72±0.76)mm(n=12).仔鱼发育过程中,其全长生长存在内源性营养阶段的较快速生长,混合营养阶段的慢速生长以及外源性营养阶段的快速生长三个生长期相,平均增长率为0.59 mm/d,对仔鱼全长TL(mm)与日龄D(d)进行同归,其生长模型为:TL=-0.0004D3+0.0283D2+0.2159D + 4.9335(R2=0.985,n=261).2-15 日龄,口宽与全长呈正比关系.仔鱼从初孵到PNR仅为5-6d,具有摄食能力的时间4d,仔鱼依赖外源性营养开始时间较早,对饥饿的耐受力较差.     

Rearing tench (Tinca tinca L.) larvae on live feed (Artemia) and on two transition schedules from live to dry diets

Two 60‐day experiments were carried out on tench (Tinca tinca L.) from day 5 post‐hatch. Density was 20 larvae L^?1 and temperature 24 ± 0.5°C. In experiment 1, Artemia nauplii were the sole food, testing nauplii amounts and feeding frequency. High survival rates (between 79.5% and 95.5%) were obtained. Growth was faster as nauplii amounts were greater; the highest growth rate (11.00), weight (265.5 mg) and Fulton’s coefficient (1.40) were obtained when fish were fed in excess once a day, without significant differences from the growth obtained by feeding in excess of eight times a day. In experiment 2, a dry diet for marine fish was tested as a replacement for Artemia nauplii, following two transition protocols, one faster than the other; high survival rates (between 77.7% and 87.1%) were again obtained. The slower transition allowed a growth rate of 10.14, length of 23.1 mm, weight of 158.3 mg and a Fulton’s coefficient of 1.28, without significant differences from the faster transition. At all stages, growth values were significantly higher from feeding nauplii in excess as the sole food, but the required nauplii quantity was six times higher than the amount supplied to the animals fed the dry diet.     

Early development of the laboratory-reared flounder,Pleuronichthys cornutus

Fertilized eggs ofPleuronichthys cornutus were obtained by both artificial fertilization and natural spawning of laboratory-reared fish. The present paper describes in detail the early development of the fish and the rearing methods employed to provide basic information for mass production of this species. Eggs and sperm for artificial fertilization were obtained from adult fish caught in the Ariake Sound, Kyushu in November and December of 1984. Their maturation was successfully induced by intermuscular injection of pituitary homogenate of the silver carp,Hypophthalmichthys molitrix. Fertilized eggs were also obtained in 1985 by natural spawning of a broodstock kept in a tank for a year. Hatched larvae were fed successively with rotifers,Artemia nauplii and the harpacticoid copepod,Tigriopus japonicus and reared for 80 days. Ten thousand young fish of about 33 mm TL were obtained in 1984 and 1985 with the survival rate of about 17%. Ten developmental stages were defined on the basis of the morphological characteristics: A) newly hatched to 4 day old larvae, 2.7 to 4.1 mm TL (2.6 to 3.9 mmNL), yolk sac present; B) 4 to 16 day old larvae, 3.8 to 5.9 mm (3.6 to 5.6 mm), yolk resorbed, actively feeding on rotifers; C) 15 to 30 day old larvae, 6.3 to 8.3 mm (6.0 to 7.9 mm), notochord straight, hypural fin ray visible; D) 24 to 40 day old larvae, 6.7 to 9.2 mm (6.4 to 8.8 mm), caudal notochord upturned (45°); E) 28 to 45 day old larvae, 7.9 to 10.8 mm (7.5 to 10.3 mm), caudal notochord upturned (45°–90°); F) 32 to 50 day old larvae, 10.8 to 15.7 mm (8.8 to 12.8 mm BL), eyes symmetrical; G) 35 to 66 day old larvae, 13.4 to 20.0 mm (10.9 to 16.3 mm), eyes asymmetrical, but left eye not visible from the right side; H) 40 to 75 day old larvae, 13.8 to 26.2 mm (11.3 to 21.4 mm), the upper edge of left eye visible over top of the head from the right side; I) 46 to 89 day old larvae, 20.1 to 27.4 mm (16.4 to 22.4mm), left eye on the edge of the head and pupil visible from the right side; and J) juveniles of 51 day old or over, 23.6 mm or more (19.3 mm or more), metamorphosis completed. One to three inflections were found for relative growth of total length, eye diameter, upper jaw length, preanal length, and distance between the base of the pectoral fin and the anus against the notochord length or body length. Two inflections were found for body length (or notochord length)-body weight relationship. Most inflections appeared at the stages of D, F and J, corresponding to the body length of 8, 9–12 and 18–22 mm respectively.     

Comparison of some live organisms and artificial diet as feed for Asian catfish Clarias macrocephalus (Günther) larvae

Experiments were conducted to evaluate the efficacy of five live organisms (Artemia, Brachionus calyciflorus, Chironomus plumosus, Moina macrocopa and Tubifex sp.) and an artificial diet (40% protein) in the larval rearing of Asian catfish Clarias macrocephalus. The larvae were fed three times daily starting at the onset of exogenous feeding. Results showed that the catfish larvae utilized the live organisms more efficiently than the artificial diet. The Tubifex‐fed larvae consistently showed the highest growth rate. In trial 1, length increment (64.9 mm), weight gain (3192 mg) and specific growth rate (13.1%) after 8 weeks of feeding were significantly higher (P < 0.05) in catfish larvae given Tubifex than those in all other treatments. In trial 2, length increment after 4 weeks of feeding was highest in larvae fed Tubifex (22.9 mm) although it did not significantly differ from that of larvae given Moina (21.0 mm). However, weight gain of larvae fed Tubifex (253.0 mg) was significantly higher than that of larvae fed Moina (171.6 mg). The specific growth rate was highest for larvae fed Tubifex (15.0%) followed by larvae fed Artemia (14.5%), Moina (14.4%) and Chironomus (12.0%). Survival rates of the catfish larvae ranged from 9 to 39% after 8 weeks in trial 1 and from 26 to 83% after 4 weeks in trial 2. The present results suggest that Tubifex is an excellent food and a potential substitute for Artemia in the rearing of catfish larvae.     

The diet of Abramis brama (L.) larvae reared in illuminated cages

The paper presents the results of investigations on the feeding of bream larvae reared in illuminated cages in a mesotrophic lake. The same species of zooplankton were found in both the lake and the fish cages. Copepoda predominated in abundance and biomass. During the mixed feeding the bream larvae diet consisted of rotifers (45.8%), small cladocerans (41.6%) and phytoplankton (13.6%). According to Ivlev's selectivity indices (E), the most important food species were: Keratella cochlearis (E = +9.94), Kellicotia longispina (E = +0.93), K. quadrata (E = +0.92), Bosmina longirostris (E = +0.92), Trichocerca sp. (E = +0.89), and Chydorus sphaericus (E = +0.88). The total length (TL) of bream larvae consuming their first nauplii and copepodites of Copepoda was 8.9 mm. As bream larvae grew, cladocerans were more often selected than rotifers. Copepods usually made up an insignificant component of the diet. Bream larvae in illuminated cages generally fed at night; their alimentary tracts were filled to the maximum in the period from sunset to sunrise. Indices thereof reached 755.6 at night and 278.0 ? in the daytime.     

The effect of starvation on RNA: DNA ratios and growth of larval striped bass, Morone saxatalis

Hatchery reared larval striped bass, Morone saxatilis , 8-days-post-hatching were subjected to various feeding/starvation regimes over a period of 14 days.
Batches of larvae from each treatment were sampled over the 14-day period and subdivided for determination of notochord length and RNA:DNA ratio. The best growth was found in fully fed F1000 larvae (exposed to 1000 Artermia nauplii l⁻¹), which reached 8.2 mm after 11 days and 9.6 mm after 14 days. Starved animals after 11 days had notochord lengths of 4.9 mm. Growth curves from feeding-delayed larvae indicated that animals fed after up to 5 days starvation were capable of complete recovery. F100 larvae (exposed to 100 Anemia nauplii 1^−l) had a slower growth rate than F1000 larvae, reaching a notochord length of 7.3 mm after 14 days. RNA:DNA ratios over time closely followed notochord growth curves, with clear differences between starved, F100 and F1000 larvae being established after only 2 days. Equilibrium RNA:DNA ratios of 3.0 and 2.25 were established in F1000 and F100 larvae, respectively, 6.8 days after the beginning of the experiment. The average lag time between a change from the starved to the fed condition and a change in RNA:DNA ratio as determined by the divergence of the nucleic acid curve from the starved condition was 0.66 days.
In treatments where starvation followed various periods of feeding, larvae regressed in notochord length such that the final length at 14 days reflected the degree of feeding. RNA:DNA ratios in these animals again closely followed growth curves with a lag time of 0.81 days.
It was concluded that RNA:DNA ratios provided very accurate indices of growth in striped bass larvae which were highly sensitive to feeding status.     

Effects of starvation on the formation of daily growth increments in the otoliths of milkfish, Chanos chanos (Forsskål), larvae

The effects of starvation on daily growth and increment formation in the otolith were examined using a double oxytetracycline-labelling method on larval milkfish, Chanos chanos (Forsskål), reared under different feeding regimes. The results indicated that the differences in body and otolith growth between the larvae fed once and three times a day were not significant, and that the otolith growth increment was deposited daily in both groups of fed larvae. In contrast, the starved larvae grew at a slower rate than fed larvae in body length and otolith dimensions, and the otolith growth increment in the starved larvae was not deposited on a daily basis. After undergoing starvation, the larvae were unable to recover their normal growth either in otolith increment deposition or in body and otolith growth even though they were fed. Therefore, the application of ageing techniques based on counting otolith growth increments seems to be inaccurate for starved larvae.     

Effect of water temperature,feeding frequency,and protein percent in the diet on water quality,growth and behavior of Nile tilapia Oreochromis niloticus (Linnaeus, 1758)

This study evaluated how water temperature (26, 28, and 30°C), number of meals per day (one or two meals), and protein percent in diet (20, 25 and 30%) impact growth performance, biometric indices, and feeding behavior of Nile tilapia, Oreochromis niloticus. Fish were randomly allocated into 18 equal replicate groups. Higher final body weight was observed in fish reared at 30°C and fed one meal per day containing 30% crude protein. Better weight gain, weight gain %, feed conversion ratio, specific growth rate, and condition factor were recorded in fish reared at 26°C and fed one meal per day containing 30% protein. The best length weight relationship was obtained in fish reared at 26°C and fed one meal per day containing 30% crude protein. Shorter feeding duration and duration of appetite inhibition latency were recorded in fish reared at 30°C, fed one meal per day, and given a diet containing 30% protein. The highest proactivity was recorded in fish reared at 30°C, received one meal per day, and with 25% crude protein in their diet. Conclusively, rearing Nile tilapia at 26–30°C with a lower feeding frequency (one meal/day) and a 30% crude protein diet achieved better performance and feeding behavior.     

Evaluation of an improved RNA/DNA quantification method in a common carp (Cyprinus carpio Linnaeus 1758) larval feeding trial with Artemia,two nematodes (Panagrellus redivivus Linnaeus 1758, Panagrolaimus sp. Fuchs 1930) and dry feed

The RNA/DNA ratio commonly used as proxy for the nutritional condition of fish larvae is affected by RNA degradation during analysis. For evaluation of two strategies to improve RNA integrity, a three‐week feeding trial was carried out to assess the suitability of two nematode species (fam. Panagrolaimidae) as feed for newly hatched carp larvae (Cyprinus carpio) in comparison to Artemia nauplii (Artemia sp.) and a commercial dry feed. Aiming for an increased reproducibility of RNA/DNA determination, a high‐salt inactivation (RNA later) as well as a targeted approach with a recombinant RNase inhibitor were compared to the classical protocol using lab chip technology. Improved RNA integrity was observed with high‐salt inactivation when compared with a strategy applying a specific RNase inhibitor or the classic protocol. Carp larvae fed Artemia for 2 weeks and then dry feed for 1 week revealed the best overall growth performance as well as survival [83.0 ± 35.2 mg fresh weight (FW), 20.0 ± 2.4 mm total length (TL), 86.6 ± 11.7% survival]. Larvae fed the nematode species Panagrellus redivivus for 1 week and subsequently dry feed for 2 weeks (37.4 ± 29.1 mg FW, 14.7 ± 2.8 mm TL, 76.0 ± 6.0% survival) performed better than larvae fed with dry feed alone (28.2 ± 29.6 mg FW, 14.3 ± 2.9 mm TL, 54.3 ± 14.2% survival) or those receiving Panagrellus for 2 weeks. Between both nematode species, Panagrellus was a better feed with regard to growth performance and survival. RNA/DNA ratios ranged between 0.65 ± 0.27 (8 days post‐hatch) and 1.96 ± 0.63 (22 days post‐hatch) and were in the same treatment order as the other growth parameters. RNA/DNA ratios were significantly correlated with the growth rate, and decreasing RNA/DNA ratios in larger larvae may reflect decreasing growth rates with size rather than decreased nutritional status. Here, an improved RNA/DNA ratio protocol is presented in a feeding trial that reveals the suitability of nematodes as a first feed for common carp larvae.     

Effects of the Amount of Food on Duration of Stages,Mortality Rates,and Size of Individuals in Tropisternus lateralis nimbatus (SAY) (Coleoptera: Hydrophylidae)

Larvae of Tropisternus lateralis nimbatus (SAY) were reared in the laboratory using different feeding regimes. Controls were fed as many mosquito larvae as they would readily eat until the later larval stages. Experimental groups were reared on a reduced number of larvae per day. The duration of stages, growth ratios, mortality rates, and elytral lengths in the control and experimental groups are compared.     

Mariculture of kurosoi,Sebastes schlegeli

Synopsis The technology of collecting developing larvae from female kurosoiSebastes schlegeli, and raising the larvae to juveniles (100 mm total length (TL)) to be released into the oopen sea, is presented. Gravid females 40–46 cm TL were captured in May–June 1977–1980 and held in the laboratory until parturition. Fecundity of fish in this size range was 100 000–184 000. Larvae were sequentially fed rotifers,Artemia nauplii, and young sand lance,Ammodytes personatus, until reaching 25 mm; this required 35 days and yielded a survival rate of 50%. Thereafter, the fish were reared in separate size groups to avoid cannibalism. Minced or chopped sand lance and commercial food were provided until the final size of 100 mm was attained. The growth of juvenile kurosoi from 25 to 100 mm required 85 days, with a survival rate of 90%. The effect of released cultured fish on the local stock is being determined from information on the recapture of tagged fish.     

Early ontogeny of Ancherythroculter nigrocauda and effects of delayed first feeding on larvae

Development of embryos and larvae in Ancherythroculter nigrocauda Yih et Woo (1964) and effects of delayed first feeding on larvae were observed after artificial fertilization. The fertilized eggs were incubated at an average temperature of 26.5°C (range: 25.7–27) and the larvae reared at temperatures ranging from 21.8 to 28°C. First cleavage was at 50 min, epiboly began at 7 h 5 min, heartbeat reached 72 per min at 24 h 40 min and hatching occurred at 43 h 15 min after insemination. Mean total length of newly hatched larvae was 4.04 ± 0.03 mm (n = 15). A one‐chambered gas bladder was observed at 70 h 50 min, two chambers occurred at 15 days, and scales appeared approximately 30 days after hatching. Larvae began to feed exogenously at day 4 post‐hatch at an average temperature of 24°C. Food deprivation resulted in a progressive atrophy of skeletal muscle fibres, deterioration of the larval digestive system and cessation of organ differentiation. Larval growth under food deprivation was significantly affected by the time of first exogenous feeding. Starved larvae began to shrink, with negative growth from day 6 post‐hatch. The point of no return (PNR) was reached at day 11 after hatching. Mortality of starved larvae increased sharply from day 12 after hatching.     

Growth of Perca fluviatilis larvae fed with Artemia spp. nauplii and the effects of initial starvation

Experiments were performed to test the growth and survival of perch larvae fed with Artemia spp. nauplii and to determine the most advantageous time of first feeding. During a first experiment, perch larvae were divided into groups according to their hatching dates. Daily ingestion of Artemia spp. nauplii began significantly 2 days after mass larvae hatching. By day 7, the daily prey acceptance was over 75% among the separate larvae groups. During a second 14-day feeding experiment, larvae fed after a 2- or a 3-day delay showed the best growths: 12.5 mm and 13.7 mg. There was no significant difference (P > 0.05) among survival rates (85.3%) of perch larvae fed after a 1-, 2- or 3-day delay.     

Deposition of copper, iron, manganese and zinc in the empty body of growing lambs of the breed German Merino Landsheep

A growth experiment with 108 lambs (breed: German Merino Landsheep) was carried out to examine the effect of gender, body weight (BW) and feeding intensity on the deposition of Fe, Zn, Cu and Mn in the empty body (whole animal minus contents of the gastrointestinal tract and bladder). The lambs (50% female and 50% male animals) were fed at three feeding levels ('low', 'medium' and 'high' by varying daily amounts of concentrate and hay) and slaughtered at different final BWs (30, 45 or 55 kg). Six male and six female animals were killed at a BW of 18 kg representing the animals' BW at the beginning of the comparative slaughter experiment. There were significant main effects for the treatments growth rate and final weight on the daily rate of accretion of the trace elements examined. Feeding intensity had a marked influence on the accretion rate for Fe (P < 0.001), Zn (P < 0.001), Cu (P < 0.001) and Mn (P = 0.003). With increasing feeding intensity (low, medium, high) the daily deposition of these trace elements increased (4.4, 5.2, 6.6 mg/day for Fe; 4.9, 5.5, 6.9 mg/day for Zn; 0.20, 0.36, 0.44 mg/day for Cu; 0.14, 0.16, 0.21 mg/day for Mn). Heavier final BW led to increased daily retention of Zn (P < 0.001) and Mn (P = 0.002). Gender had a marked influence only on the accretion rate for Zn (P < 0.001). Ram lambs had a higher daily deposition of this element than female lambs. Related to 1000 g empty body gain, the following concentrations were found for the trace elements examined: Fe 26.1 mg, Zn 30.0 mg, Cu 1.41 mg and Mn 1.04 mg. A feeding influence was given for Zn (P < 0.001) and Cu (P = 0.039). Feeding level low had higher Zn and lower Cu concentrations. Male animals showed less Fe (P < 0.001) and Zn (P = 0.034) per kg empty body gain than females.     

Induction of ovarian maturation and development of eggs,Larvae and Juveniles of the Puffer,Takifugu exascurus,Reared in the Laboratory

Ovarian maturation of the pufferTakifugu exascurus (Jordan et Snyder) was induced, and embryonic, larval and juvenile development was observed. The brood fish were collected in Tassha Bay, Sado Island (38°05′N, 138°15′E), during the spawning season in 1986 which seemed to extend from late June to mid-July. To each female 3 mg acetone-dried pituitary ofHypophthalmichthys molitrix was injected to induce ovarian maturation, which took place in about 77 hours at a water temperature of 19.5–21.0°C. The eggs obtained by hormone injection were artificially fertilized with the milt from a collected male. The hatched larvae were fed successively on rotifersBrachionus plicatilis, Artemia nauplii and minced fish meat, and reared for a period of about one year. The eggs were spherical, 1.24±0.04mm in diameter, demersal and adhesive. The egg-membrane Was transparent and yolk was orange in color, containing a cluster of small oil-globules. The incubation period was about 160 hours at a water temperature of 18.5–21.0°C. The newly-hatched larvae, measuring 2.9– 3.1 mm TL, had 8+15 = 23 myomeres. Absorption of the yolk was completed 3 days after hatching, by which time the larvae had attained 3.5–3.6 mm TL. Larval finfolds disappeared and rudimentary dorsal, anal and caudal fins formed at 4.1–4.4 mm TL, in 6 days after hatching. In 9-day old larva (5.4 mm TL), fin ray rudiments appeared on the dosai, anal and caudal fins and spine-like scale formed on the belly. In 16-day old specimens, 9.1–10.2 mm TL, the full complements of fin rays were completed on all the fins and the fish reached the juvenile stage. The growth of larvae and juveniles reared in 1986–1987 is expressed by the following equations, where y is total length (mm) and x is days after hatching. y₁ = 2.9420· 1.0639^x 0 ≦ x ≦ 19 (r = 0.998) y₂ = 4.0286· 1.0464^x 19≦ x ≦ 33 (r = 0.998) y₃ = 9.8854· 1.0180^x 33 ≦ x ≦ 72 (r = 0.996) y₄ = 20.1555· 1.0080^x 72 ≦ x ≦ 115 (r = 0.998) y₅ = 28.0610· 1.0049^x 115 ≦ x ≦ 202 (r = 0.995)     

Diel food utilization by woundfin,Plagopterus argentissimus,in Virgin River,Arizona

Synopsis Woundfin, Plagopterus argentissimus, fed predominantly on simuliid larvae during the day, and shifted to the larger Hydropsyche spp. at night. Ephemeropteran larvae were eaten nearly uniformly throughout the 24 hour period. Mean weight of food consumed varied from 20–40 mg per individual (0.7–2.5% body weight) throughout the 24 h period. Our estimated daily ration of about 8% body weight, at temperatures that varied between 15–25°C, is based upon our measure of mean gut contents over a 24h period, combined with intestinal evacuation rates suggested for other cyprinids in the literature. The relatively continuous feeding pattern suggests a foraging strategy that would minimize competition with other species for food during June, a period of minimum annual food abundance in Virgin River.     

Effets du retard dans la première alimentation sur le développement de la larve planctotrophe de l'oursin Paracentrotus lividus

The growth of the skleleton and changes in biochemical constituents (proteins, carbohydrates and lipids) were observed in embryos (days 0 and 1) and larvae (2-8 days) of the sea urchin Paracentrotus lividus that were starved (C 0) or fed low (1,000 cells of Hymenomonas elongata, C 1) or high (5,000 cells, C 5). Different batches of C 1 and C 5 larvae were fed first the 2nd, 3rd, 4th or 5th day after fertilization. Initiation of feeding 24 h after hatching slowed down the rate of increase in length of the larval appendages. A differential growth of skeletic rods (somatic and postoral rods) and variations in proteins weights shows the existence of a mixotrophic phase between endotrophic and planktotrophic phases. Best development occured in larvae which were first fed at the lower food level 24 h after hatching. On the 2nd and the 3rd day the somatic/postoral rod ratio is ≥1. This higher ration can be used to estimate the age of natural populations of larvae.     

Weak compensatory growth makes short-term starvation an unsuitable technique to mitigate body deformities of <Emphasis Type="Italic">Tinca tinca</Emphasis> juveniles in intensive culture

Juvenile tench, Tinca tinca (L.) (initial mean weight 0.67 g) were continuously fed at high (5.0% of fish biomass) or low (2.5% of fish biomass) daily doses of a commercial formulated diet, or starved for 6 days, then fed these doses. The experiment lasted 40 days. Visible skeletal deformities occurred in fish fed the high doses, and the 6-day food deprivation mitigated the percentage of deformed fish from 37.3 to 12.1%. Deformities were associated with higher condition coefficient value. Faster growing individuals were more susceptible to body malformations within the feeding groups. No compensatory growth in body weight was observed in juveniles fed high or low doses. Lack of compensation was supported by lower carbon/nitrogen ratio in starved-re-alimented fish. Morphometric indices (condition coefficient and height/length ratio) suggested only partial compensation observed mostly during the first few days after the end of starvation. The possible mechanisms underlying this weak compensatory response in T. tinca juveniles may be associated with their slow growth rate and low oxygen consumption. Short starvation mitigates body deformities in intensively fed tench juveniles, however, this technique is not recommended in aquaculture due to their weak compensatory growth response.