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1.
Abstract— An important aspect in the development of any aquaculture industry is the maximization of juvenile somatic growth (i.e., body growth) to reduce production time and increase the size of the final product. In this study, green sea urchins Strongylocentrotus clroebachiensis were fed a prepared diet from 4 December 1998 to 10 September 1999 (i.e., 280 d) in a laboratory to investigate the effect of protein source (soybean andlor fish), protein concentration (20,30,40, and 50% dry mass) and juvenile size (4‐8 mm and 12‐20 mm initial test diameter) on somatic growth. A natural diet of Laminwia longicrurus (i.e., kelp) was used as a reference. There was no difference in initial size among the treatments for either the smaller cohort 1 or the larger cohort 2 sea urchins (6.3 mm and 13.8 mm initial average test diameter, respectively) (P > 0.05 for all tests). After 280 d, the sea urchins fed kelp had an average size of 20.7 mm and 24.5 mm (cohort 1 and cohort 2, respectively). The final average sizes of the sea urchins fed the prepared diets, which did not relate to dietary protein concentrations andlor protein source, ranged from 13.2 mm to 16.2 mm (cohort 1) and from 20.4 mm to 22.9 mm (cohort 2), and were significantly smaller than the kelpfed sea urchins (P < 0.05 and P < 0.001, cohort 1 and cohort 2, respectively). All treatments experienced 95% survivorship or greater. Sea urchin size appears to affect growth rate when optimal conditions for growth are available (i.e., diet and water temperature). As water temperatures increased during the summer of 1999, the sea urchins in cohort 1 fed kelp had a significantly higher growth rate (0.069 dd) than the cohort 2 kelpfed sea urchins (0.052 dd) (P < 0.05). However, within each cohort, there were no significant difference in growth rate (P > 0.05) among the sea urchins fed prepared diets, suggesting sea urchins do not require high concentrations of dietary protein for superior growth, and that plant protein can substitute fish protein in sea urchin diets. Furthermore, the sea urchins fed the prepared diets had poorer test quality and larger gonad yields (13‐22%) compared to the kelpfed sea urchins (4.2%) and a wild sample of sea urchins of similar size (4.0%). The results suggest that the sea urchins fed the prepared diets allocated more energy to gonad production, whereas those fed a natural diet allocated more energy toward test production. To address this gap, more research is required to identify the nutritional components required for test growth that were present in kelp, but appeared to be deficient in the prepared diets.  相似文献   

2.
Abstract.— The black porgy Acanthopagrus schlegeli is one of the most important marine fish cultured in Taiwan. Wild-caught broodstock were spawned naturally in captivity at water temperatures of 19–26 C in 1989 and 1990. Females produced 352,000 to 957,000 eggs per female during the spawning period. The hatched larvae were reared in 45-m3 rectangular cement tanks and fed initially on rotifers, Brachionus plicatilis . followed by Artemia nauplii. and finally weaned onto an artificial diet. Larviculture trials to 40 d produced juveniles of 13.1–14.2 mm average total length, at a survival rate ranging from 18.3 to 74.8%. Lordotic deformation was observed in the juvenile stage. However, when an oil skimmer was used to remove the oil film on the water surface, the incidence of lordosis was reduced from 14.4 to 6.1%. High mortality of the larvae occurred during the initial 10–15 d after hatching and cannibalism was observed when larvae reached 7 mm total length. Juveniles grew to size of 83.7–101.4 mm total length with survival rate of 27.9–28.2% in 100 d. The results indicate that the present technique can be used for mass seed production of black porgy.  相似文献   

3.
We compared the gonad-enhancing effects of two diets (NIWA and NIFA diets) in two size classes of sea urchins (Evechinus chloroticus): small and large urchins with a test diameter of 75.6 ± 1.2 mm and 93.8 ± 0.5 mm, weighing 174.8 ± 7.9 g and 315 ± 5.6 g, respectively. After eight weeks being fed prepared diets, urchin gonad index (GI) had significantly surpassed that of the initial and final samples of wild urchins. Urchins in the NIWA/small treatment had a larger GI than the NIFA/small and NIFA/large treatments. The NIWA/large treatment had a larger GI than the NIFA/large treatment. The overall percentage increase in GI for the NIWA/small, NIWA/large, NIFA/small and NIFA/large treatments were 183%, 135%, 132% and 85%, respectively. In terms of gonad colour (CIELAB), there were no significant differences in gonad redness (a*) or yellowness (b*) between experimental treatments, but there was a significant difference in gonad lightness (L*) with small urchins fed both diets having lighter-coloured gonads than the large urchins fed both diets. Sensory assessment of gonads revealed that gonads from small urchins fed both diets were rated as being of better colouration and more uniform in colour than gonads from large urchins. Gonads of urchins fed the NIFA diet were rated as being less bitter and of better overall taste than gonads from urchins fed the NIWA diet. This study shows that feeding prepared diets to E. chloroticus can significantly increase gonad yield but that different diets can affect the magnitude of GI increase and the taste of gonads, and that smaller urchins appear more suitable for gonad enhancement.  相似文献   

4.
The growth and enzyme response of Fennero Penaeus indicus postlarvae (PL) was assessed with natural and artificial diets for the first 2 weeks of PL development to PL14 (14 days after metamorphosis to PL1). At PL14, postlarvae reared under similar conditions were separated into two size groups based on slow growth (9.57 ± 0.46 mm) and fast growth (13.90 ± 0.28 mm), and reared for a further 63 days. Growth among postlarvae PL1 and the smaller size group at PL14 fed on artificial diet was significantly slower than that of PLs fed on Artemia nauplii or fresh mussel. In contrast, the larger size group at PL14 did not show a significant difference in growth when fed artificial diet or fresh mussel. Trypsin and amylase response was significantly related to postlarval total length ( P  < 0.001); thus, digestive enzyme response increased with size and stage of development, but did not change significantly with diet fed. The amylase–protease ratio increased from PL1 and amylase activity became higher than the activity of trypsin for 2–3 weeks after metamorphosis. It appears that during the early stages of development postlarvae are unable to digest artificial diets efficiently because of low digestive capacity. Hence, poorly digestible feed delayed development and increased size variability. For smaller PL14, poor performance on artificial diets is possibly linked to a genetically regulated constraint, but not to digestive capacity since enzyme levels were similar to those found in larger PL14. During postlarval stages digestive enzyme production seems to be developmentally cued so that for postlarvae it appears that more digestible high-energy diets are required to reduce size variability during the nursery phase.  相似文献   

5.
The nutritive values of three pelleted prepared diets, based on animal (AP), vegetable (VP) and yeast protein (YP) were studied for the sea urchin Heliocidaris erythrogramma (Val.). Fresh macroalga Ulva australis was used as a natural control diet. Triplicate groups of five animals were fed one of the four diets ad libitum every second day for 85 days. Sea urchins fed pelleted feeds had significantly higher food consumption rates (dry basis) and significantly lower total and protein absorption efficiencies compared with the algal diet. The gonad yield and gonad production efficiency in sea urchins fed the natural diet were significantly higher compared with initial group (gonad yield only) and urchins fed animal and vegetable diets, but did not differ significantly from those of the animals fed the yeast diet. Percent protein and lipid in the gonads were not affected by the dietary source. The taste and smell of gonads were generally better in sea urchins collected from the wild or fed yeast and natural diets than in sea urchins fed animal and vegetable diets. The animal protein diet was the most stable in seawater while the yeast protein diet had the poorest water stability. The results of this study suggest that development of a more stable, single‐cell, protein‐based diet has a potential to promote gonad production of H. erythrogramma.  相似文献   

6.
In a 62‐day growth trial, wild caught Lytechinus variegatus (ca. 18 g, 35 ± 2 mm dia.) were fed as follows: (i) ration equivalent to 3% of average body weight proffered once daily in the morning (AM treatment); (ii) ration equivalent to 3% of average body weight proffered once daily in the evening (PM treatment); (iii) ration equivalent to 1.5% of average body weight proffered twice daily (every 12 h, AM/PM treatment); (iv) ration equivalent to 3% of average body weight proffered in the evening on alternate days (EODSR/PM); or (v) ration equivalent to 6% of average body weight proffered in the evening on alternate days (EODDR/PM). At 30 and 62 days, wet weight gain among urchins fed daily was significantly higher than that of urchins fed on alternate days, regardless of ration size. At 62 days, reduced gonad dry matter production and gonad index were observed among individuals fed on alternate days, regardless of ration size. At 30 and 62 days, feed conversion ratio was optimized among individuals fed daily and in the EODSR/PM treatment. These data suggest that, for culture of L. variegatus, daily feeding will optimize growth, gonad production and feed efficiency regardless of ration size or time of feeding.  相似文献   

7.
This study investigated the effects of dietary minerals and pigments in prepared diets on the somatic growth performance of wild and hatchery‐reared juvenile green sea urchins, Strongylocentrotus droebachiensis, by two feeding trials. In the first feeding trial, a modified Bernhart‐Tomerelli salt mix (BT) at 0, 1.5, 3, 6, and 15% dry mass and a Shur‐Gain/Maple Leaf Foods mineral mix at 3 and 6% dry mass were used to test for mineral effects. Pigment effects were tested by incorporating 1.25% Algro? to the prepared diets (i.e., 250 mg of beta‐carotene per kilogram of diet). Sea urchins (13–15 mm of initial test diameter [TD]) collected from the wild were fed the prepared diets over 154 d. The sea urchins that were fed the pigmented diets had significantly greater test growth than those fed the nonpigmented diets, and mineral concentration in the pigmented diets was directly related to juvenile size at the end of the feeding trial. A sample of juveniles from each treatment group was sacrificed to determine test, gonad, and gut yields and ash concentrations. Ash concentrations in the test and gonad were higher for juveniles fed pigmented diets than for those fed nonpigmented diets with similar mineral concentration, suggesting an interaction between minerals and pigments within the juvenile sea urchins. The second feeding trail used two size cohorts of hatchery‐reared juveniles ranging from 1–2 mm and 2–3 mm of initial TD to compare the growth of sea urchins fed either the pigmented diet with 15% BT (i.e., the best diet in the first feeding trial) or kelp, Laminaria longicruris, over 159 d. Growth performance was similar for both cohorts, indicating no size effect, but the juveniles fed the prepared diet were significantly larger at the end of the feeding trial than those fed kelp. This suggests that prepared diets with pigment and high mineral concentration can outperform kelp, and be utilized for juvenile green sea urchins to increase test growth.  相似文献   

8.
In adult sea urchins, formulated feeds can support both weight gain and gonad production; however, studies demonstrating the effects of formulated feeds on juvenile sea urchin growth are limited. In this study, juvenile sea urchins (test diameter: 3.20–7.33 mm, N = 12 per treatment) were reared individually in artificial seawater and fed with one of four experimental feeds: (1) mixed‐taxa algal biofilm (MTAB), (2) freeze‐dried MTAB, (3) a commercial, small‐mammal feed (Friskies® cat treats), or (4) a semipurified feed formulated for sea urchins. The MTAB and sea urchin feed supported weight gain and survival throughout the study; however, those individuals fed with the sea urchin feed exhibited a short lag period at the onset of feeding. This short lag period may be, in part, because of an initial lack of attraction of the urchins to the formulated feed. Furthermore, we hypothesize that gut physiology or gut flora must acclimatize to a new diet (all sea urchins were reared initially on the MTAB diet). The freeze‐dried MTAB and mammal feed did not support substantial weight gain. This study suggests that sea urchin juveniles as small as 3–4 mm can utilize formulated feeds for growth.  相似文献   

9.
Four artificial, dry feeds and two diets consisting of natural, live food were evaluated for use as starter diets in the intensive rearing of European grayling (Thymallus thymallus). Long-term effects of the different diets were also studied. The investigation was divided into two parts: a 14 day starter period and the subsequent 115 days, during which the long-term effects were studied. Diets differed between the different treatment groups during the initial 2 weeks, whereafter all fish were offered a single diet. At the end of the starter period, significant differences in weight (p<0.001) were obtained between natural (control) feed groups and three of the artificial feed groups. The highest growth rate (9.6% day–1), and length increase (9 mm) as well as the lowest mortality rate (6.0%) were obtained with one of the artificial diets. Growth rate, length increase and mortality of grayling in the other diet groups varied from 3.6 to 7.7% day–1, 5 to 7 mm and 7.0 to 9.1%, respectively. The switchover to a different dry diet resulted in an increase in mean daily mortality for all groups previously fed a dry diet. For the fish previously fed live food the mortality rate remained about the same. Groups of fish growing slowly during one period seemed to compensate for their initially low growth by increasing their growth rates during the next period. The highest mean daily mortality for all groups during the experiment was observed during the period with the highest water temperature. It was concluded that European grayling can be intensively reared during the start-feeding phase on artificial as well as natural diets, and that artificial dry diets can be used exclusively throughout the first summer.  相似文献   

10.
Abstract.— Two 10-d hatchery growth trials were conducted to determine if differences in growth, body composition, and survival existed among catfish fry Ictalurus punctatus fed a diet of 100% catfish-starter (CS) or CS in combination with decapsulated Artemia cysts (DAC) at 25%, 50 % , or 75% of diet weight. A 120–d production trial was undertaken immediately following the first hatchery trial to evaluate the effects of diet on production characteristics (survival, length, weight, feed conversion ratio, and total yield) of fingerling catfish produced from hatchery-raised fry. Fry fed diets containing DAC weighed 61–98% more ( P < 0.05) than fry fed only CS. The size differential of DAC-fed fry was maintained through 120 d of growth in simulated nursery ponds (0.001-ha earthen-bottom pools). The increased growth of fry fed DAC might have been related to differences in dietary lipid content, amino acid composition, or digestibility of CS and DAC. Body weights of fingerlings produced under simulated production conditions from fry fed hatchery diets containing 50% and 75% DAC were 17% and 25% higher, respectively, 130 d post-hatch, than fingerlings produced from fry fed only CS. In addition, the total yield of fingerlings produced from fry fed 75% DAC was 17% greater that that of fingerlings produced from fry fed only CS. The increased performance of fingerlings produced from DAC-fed fry could have resulted from their larger size at stocking, since larger fry might be capable of capturing natural food organisms and ingesting prepared diets more effectively than smaller fish. CS-DAC diet combinations could be used to increase weight gain of hatchery-raised fry if the cost-benefit ratio of adding DAC to the standard hatchery diet warrants its use.  相似文献   

11.
Newly hatched juvenile Buccinum undatum can be reared under laboratory conditions. Good was growth is achieved when juveniles were fed on combined diets (blue mussel, cod, and fish pellets). Juveniles reached shell heights of 33.0 ± 4.2 mm, 26.9 ± 3.8 ± mm, 23.2 ± 2.2 mm, and 20.1 ± 1.6 mm, after 14 months of fedding on a combined diet, blue mussel, cod, and fish pellets, respectively under ambient sea temperature and salinity. After 14 months juveniles fed blue mussel had the highest survival rates (67%) followed by those fed a combination of all other experimental diets (61%), cod waste (53%) and fish-feed pellets (46%). High mortalities were recorded in most treatments during the summer months between June and September. This species appears to have an aquaculture potential, as juveniles readily feed on artificial diets at an early age, show high survival rates and could potentially reach market size in 2 years or less. The major constraint in realising this potential at present, is the relatively low value of the species; if market values increased as a result of serious depletion of natural populations, hatchery production of juveniles for intensive aquaculture or restocking could become economically viable.  相似文献   

12.
“配合饲料”以植物蛋白质和碳水化合物为主，加以适量各种添加剂，经科学调配混合组成。蛋白质含量２５－２６％，脂肪８４－１２９％，碳水化合物４３－５６％，并含有扇贝亲贝性腺成熟必需的微量元素和其他促进性腺成长发育的重要成分。经饲喂试验表明：亲贝性腺指数提高２０－３０％，亲贝成活率９８％，比对照提高２６％，亲贝产出优质精、卵，受精卵的孵化率９３％，饲料成本降低５０％，是一种完全可以代替单胞藻喂养扇贝亲贝的优良配合饲料。  相似文献   

13.
Abstract Growth rates of juvenile yabbies Cherax destructor fed a variety of natural and an artificial diet were compared under controlled conditions. Newly independent (stage 3) juveniles were reared individually in 1-L pomades for 35 d. The best survival and growth were obtained on live zooplankton, frozen zooplankton, shrimp meal pellets and tubifex worms (survival, 100%; mean weights, 608, 444, 380 and 338 mg, respectively). Intermediate growth and survival was exhibited by crayfish fed chironomid larvae, snails and mussels (survival, 80–100%; mean weight, 138–169 mg). Juveniles fed trout muscle, beef heart and yabby tail gave very poor growth and survival (survival, 50–80%; mean weight, 50–55 mg). The use of shrimp meal pellets as a reference diet for juvenile yabbies is discussed.  相似文献   

14.
Newly hatched juvenile Buccinum undatum can be reared under laboratory conditions. Good was growth is achieved when juveniles were fed on combined diets (blue mussel, cod, and fish pellets). Juveniles reached shell heights of 33.0?±?4.2?mm, 26.9?±?3.8?mm, 23.2?±?2.2?mm, and 20.1?±?1.6?mm, after 14 months of fedding on a combined diet, blue mussel, cod, and fish pellets, respectively under ambient sea temperature and salinity. After 14 months juveniles fed blue mussel had the highest survival rates (67%) followed by those fed a combination of all other experimental diets (61%), cod waste (53%) and fish-feed pellets (46%). High mortalities were recorded in most treatments during the summer months between June and September. This species appears to have an aquaculture potential, as juveniles readily feed on artificial diets at an early age, show high survival rates and could potentially reach market size in 2 years or less. The major constraint in realising this potential at present, is the relatively low value of the species; if market values increased as a result of serious depletion of natural populations, hatchery production of juveniles for intensive aquaculture or restocking could become economically viable.  相似文献   

15.
The growth and mortality of Neptunea arthritica juveniles hatched from different egg masses (controlled conditions and field) reared at 10 and 15 °C, and provided with sardine (D1) and polychaete (D2) as foods were evaluated. Results showed that diet type and water temperature significantly affect the growth and mortality. Interaction between these factors reflected robust relationship among them, but restricted exclusively to growth. Through the study period, juveniles treated at 10 °C showed maximum increments of 2.5 mm (shell length), 2.3 mm (shell width) and 0.25 g (body weight) from their initial size. While maximum values of those treated at 15 °C for the above-mentioned parameters were 7.6 mm, 5.5 mm and 1 g respectively. In both cases, these increments were recorded for individuals fed with sardine. Mortality was significantly affected by diets and water temperature, which significantly increased under D2 [10 °C (20–67%), 15 °C (70–87%)] or 15 °C [D1 (30–83%), D2 (70–87%)]. According to the results, juveniles of N. arthritica could be maintained under controlled conditions, which allows growth improvement. Mortality appears to be the limiting factor, but this could be improved by the implementation of efficient culture method, basically oriented to increase the water quality.  相似文献   

16.
Abstract.— Feed costs are a major portion of aqua-culture operations. Accurate estimates of daily ration are vital to prevent overfeeding which results in wasted feed. poor water quality, underfeeding, and reduced growth. Understanding the relationship of ingestion rate and absorption efficiency of Strongylocentrotus franciscanus should improve the cost effectiveness of aquaculture of this candidate species. Adult S. franciscanus were collected from a subtidal area devoid of algae and fed two rations of an extruded diet for 62 d. Mean test diameter and whole weight of an initial sample were 91 ± 2 mm and 295 ± 18.4 g (mean ± SEM; N = 16). The two rations used were l-g dry feed/d or 3 g/d. An unfed control group was also maintained. Eight urchins per treatment showed significant differences in food ingestion rate, total organic absorption, gonad index, gut index, and moisture content of the gonad (P < 0.001). Food intake was greatest in the high ration treatment, while total organic absorption was greatest in the low ration treatment. The gonad index of S. franciscanus in the high food ration was significantly greater than the initial gonad index and was also greater than the index of animals in the low ration and unfed treatments. The gonad index of animals in the low food ration treatment was significantly greater than the index of the initial sample and the index of animals in the unfed treatment. The gut index of urchins in the high food ration treatment was significantly greater than initially and was also greater than the gut index for animals in the low ration and unfed treatments. The gut index for urchins in the unfed treatment was significantly less than the initial index. The moisture content of the gonad of urchins fed the prepared diet was significantly greater than the gonad moisture content of the initial sample or unfed group. Test diameter. whole animal weight, and gonad production efficiency (increase in g dry gonad weight/g dry feed intake) were not significantly different (P > 0.200). Histological examination of the gonads showed S. franciscanus in the two ration treatments developed from the spent to the growing or premature stage while the unfed controls lost nutritive tissue and contained only relict gametes or remained in the spent condition. The results suggest S. franciscanus from food-limited environments can be fed appropriate rations to control gonad production.  相似文献   

17.
Spermatophore and sperm quality of male Argentine red shrimp Pleoticus muelleri held under laboratory conditions was evaluated using compound spermatophore weight, sperm count and percentage of live sperm as indicators. Thirty-seven males of S to 20 g wet weight were held indoors in a 3-m diameter circular fiberglass tank for 45 d. They were fed fresh squid, clam and pelletized diet. Spermato-phores were obtained by manual ejaculations. Four shrimps were re-ejaculated to verify the subsequent spermatophore regeneration. Spermatophore mean weights were significantly lower for 5–10 g males than for 15–20 g males ( r = 0.998) (P < 0.05). There were no significant differences in sperm count and percent live sperm among the different weight classes (5–15 g, 15–20 g, 20–25 g). The sperm count varied from 2.22 to 5.62 million. No change in sperm quality was seen in re-ejaculated individuals. During the first 2 wk of the experiment, the spermatophores exhibited healthy morphology and colour; by the fifth week evidence of spermatophore deterioration was apparent. Despite the degree of melanization, sperm quality was not affected and the high variability in sperm count indicated that the artificial ejaculation is adequate in this species.  相似文献   

18.
In this study, we evaluated protein and carbohydrate levels in cold‐extruded dry diets. Sea urchins (12.6 ± 0.12 SE g wet weight, 29.5 ± 0.11 SE mm diameter) were collected from St. Joseph Bay, Florida (30°N, 85.5°W), and transported to the Texas Agrilife Research Mariculture Laboratory in Port Aransas, Texas. Urchins were held individually in replicated enclosures within a recirculating seawater system (32 ± 2 ppt and 22 ± 2 C). Urchins (n = 16urchins) were fed diets that differed in protein : carbohydrate levels (31:33%, 25:39%, 21:44%, and 17:47% dry weight) for 12‐wk. Survival was 100% in all diet treatments. Urchins fed the 31:33% protein : carbohydrate diet consumed less feed, more dry protein, less dry carbohydrate, less energy, and had lower feed conversion ratios than urchins fed other diets. Urchins fed the 31:33% protein : carbohydrate diet had larger test diameters, total wet weights, production efficiencies, and gonad production efficiencies than urchins in the other diets. Weight gain varied directly and significantly with protein intake. Sufficient energy was available for maximum weight gain as protein was spared. Growth rates and production efficiencies for the urchins in this study were higher than in previous feeding studies with adult Lytechinus variegatus.  相似文献   

19.
Abstract

A feed manufacturing method involving the production of large pellets followed by crumbling to desired diet sizes was used to produce six shrimp diets to determine its effect on growth of three size classes of Pacific white shrimp, Litopenaeus vannamei. The six diets containing 45% protein were 0.7 mm crumble, 1.2 mm crumble, 1.7 mm crumble, 2.2 mm crumble, 2.6 mm crumble, and 3.0 mm pellet. These diets were fed to three size classes of shrimp subjected to a four-week growth trial under indoor laboratory conditions. Stocking density was 12 shrimp/aquarium for size class 1 (1.13iö.01 g), 9 shrimp/aquarium for size class 2 (7.31iö.06 g), and 6 shrimp/aquarium for size class 3 (13.12iö. 10 g). Shrimp were fed three times daily and were evaluated for live weight, growth rate, feed conversion ratio (FCR), and survival. Results for shrimp growth appeared to be affected by diet size and pellet water stability. The effects of diet size, however, were more evident on smaller sized shrimp. Weekly growth rates for class 1 and class 2 shrimp indicated significant responses (P < 0.05) to the effects of diet size, while the class 3 shrimp did not show any significant result. The growth rates for both class 1 and class 2 shrimp were lowest at the smallest diet size (0.7 mm crumble) but differed with respect to highest growth rates. The largest diet (3.0 mm pellets) yielded the highest growth rates for class 1 shrimp, while medium sized feed (2.2 mm crumble) produced the best growth for class 2 shrimp. This could be partly attributed to pellet water stability, which had a direct correlation to diet size (r = 0.97). Smaller diet sizes resulting from crumbling larger pellets tend to have lower water stability. The water stability decreased from 82.5% to 76.3% as the 3.0 mm pellets were reduced to 0.7 mm crumbles. Stress cracks are created during crumbling, and surface area to volume ratio are increased as larger particles are reduced to crumbles. These would make smaller diet particles more susceptible to disintegration and nutrient leaching. For class 3 shrimp, the largest pellets produced the highest growth rate. This high growth value, however, was not significantly different (P > 0.05) from growth results produced by the crumbled feed sizes. This observation suggests that diet sizes ranging from 0.7 mm crumble to 3.0 mm pellet could be used for a 13 g shrimp, although preference would be given to larger pellets due to higher growth performance and better pellet water stability. Results for shrimp live weights were similar to results obtained for weekly growth rates. FCR and survival of all shrimp sizes did not show any significant response from the effects of various diet sizes. However, larger shrimp were less efficient in their diet utilization than smaller shrimp.  相似文献   

20.
The effect of a dry pelleted diet on growth of the Yucatan octopus (Octopus maya) was determined and compared with crab diet (Callinectes spp). Two groups of 15 wild collected animals were used. Octopuses were placed in isolation, in a flow‐through system composed of 30 circular tanks (80 L), with a bottom of 40 cm in diameter and a water depth of 80 cm. Experiment lasted 40 days, and octopuses were weighed every 10 days to determine growth rates. Octopuses were fed between 7% and 10% body weight (BW) per day, twice a day at 9:00 h and 17:00 h. Uneaten food was removed after 4 h in the tanks and weighed, to determine food ingestion and conversion. No mortality as a result of natural causes was observed. The 15 octopuses fed on frozen crabs and the 15 fed on the artificial diet had similar weights (P > 0.05) at the start of the experiment, of 486.2 ± 214.8 and 472.5 ± 228.3 g, respectively. At the end of the experiment, octopuses fed on frozen crabs weighed 1466.5 ± 484.0 g, and were significantly larger (P < 0.05), than octopuses fed on artificial diets (438.9 ± 202.6 g). Growth rates for the experiment were of 3.3 ± 0.2 and –0.0 ± 0.3% BW per day, for octopuses fed frozen crabs and the artificial diet, respectively. The artificial diet did not promote growth, but animals did not loose weight and more important, ate regularly all the food supplied, with feeding rates higher than reported in the literature for prepared diets. This makes O. maya a good research animal for the development of artificial diets for cephalopods.  相似文献   

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