Effect of Protein Source and Concentration on Somatic Growth of Juvenile Green Sea Urchins Strongylocentrotus droebachiensis

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.     

Effect of Dietary Minerals and Pigment on Somatic Growth of Juvenile Green Sea Urchins, Strongylocentrotus droebachiensis

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.     

Effect of Lipid Source and Concentration on Somatic Growth of Juvenile Green Sea Urchins, Strongylocentrotus droebachiensis

Supplying juvenile sea urchins with an abundant supply of resources and essential nutrients for growth will facilitate somatic growth and, hence, improve the success of the sea urchin aquaculture industry. Lipids are essential in physical processes such as membrane production and are a concentrated source of energy. This study, using prepared diets, tested the effects of lipid sources containing different major fatty acids (i.e., n‐3 and/or n‐6) (Part 1) and lipid concentration (i.e., 1, 3, 7, and 10%) (Part 2) on the somatic (i.e., test or shell) growth of two size cohorts (7.0‐ and 15.3‐mm average initial test diameter [TD]) of juvenile green sea urchins, Strongylocentrotus droebachiensis. The growth of the sea urchins fed prepared diets was compared to the growth of sea urchins fed a kelp reference diet, Laminaria longicruris. After both feeding trials, the kelp‐fed sea urchins had superior test growth and were more similar in physical appearance to wild sea urchins (i.e., test color, spine length, and gonad color). The sea urchins fed the prepared diets had pale test color, short, stubby spines, and large, pale‐colored gonads compared to wild sea urchins. The smaller cohort of sea urchins grew at a faster rate, but growth patterns for both cohorts were similar. The juveniles fed the prepared diets (in both feeding trials) had high initial growth rates that decreased after approximately 100 d compared to the kelp‐fed juveniles. Differences in test growth were not shown to be affected by sea urchin size (i.e., similar results for both cohorts) or by differences in dietary lipid sources (i.e., the presence of n‐3 and/or n‐6 fatty acids). However, the sea urchins fed diets with lower lipid concentration (≤3%) had larger average TDs than those fed diets with higher lipid concentrations (≥7%). Differences in test growth and physical appearance among those fed the prepared diets and kelp may have been because of nutritional deficiencies in the prepared diets.     

Effects of Hyperoxic Conditions on Growth Performance in Juvenile and Adult Green Sea Urchin,Strongylocentrotus droebachiensis

The effects of hyperoxic conditions on survival, gonad growth, feed intake, and food conversion of adult and somatic growth and survival of juvenile green sea urchin, Strongylocentrotus droebachiensis, were examined. Juvenile and adult sea urchins with initial diameters of 11.5 and 75 mm, respectively, were reared in water with constant oxygen saturations of 100 (control), 115 and 130% for 42 d (juvenile) and 51 d (adult sea urchin) at 8 C and 33‰ salinity. During the experiment the gonad indices of the adults tripled from 7.3% (±1.5) to 21.4% (±4.3), 19.4% (±4.7), and 22.0% (±4.4) for the groups kept at 100, 115, and 130% oxygen saturation, respectively. At the end of the experiment, the differences in gonadal size among the groups were not significant. Neither were there any significant differences in food intake or food conversion ratio among the groups. Only one animal died during the experiment. The juvenile sea urchin kept at 100, 115, and 130% oxygen saturation doubled their test diameter from initially 11.5 mm (±1.5) to 19.9 mm (±1.4), 21.4 mm (±2.1) and 20.6 mm (1.0), respectively, but there were no significant differences in growth among these groups. There was no mortality during the experiments in these groups. Overall, the findings suggest that juvenile and adult S. droebachiensis are unable to utilize hypersaturation of oxygen to increase somatic or gonad growth, but can be reared at hyperoxygenated water for prolonged periods of time without harmful effects.     

Long‐term Growth Study of Male and Female Green Sea Urchins,Strongylocentrotus droebachiensis,under Constant Light and Temperature Regime

Juvenile green sea urchins, Strongylocentrotus droebachiensis, with an initial mean test diameter of 9.5 mm (±1.2 SD) were held in the laboratory, in individual compartments and at constant temperatures (8.5 C) (n = 90) for a period of 99 wk. The animals were supplied with flow‐through sea water, and fed the Nofima sea urchin manufactured feed ad libitum. Growth, survival, feed intake, feed conversion ratio (FCR), and gonad index (GI) of the sea urchins were monitored during this period. The mortality was 11% throughout the experimental period. The test diameter (TD) increased significantly with time, best described by a polynomial equation (TD = 0.8756 + 0.584Time − 0.002Time², R² = 0.995). Sex was included as dummy variable, but did not contribute significantly; hence, there were no differences in growth trajectories between males and females. The study showed there were no significant differences in body wet weight or FCR between males and females. However at the end of the experiment the female urchins had a significantly higher GI of 31.1% (±4.4), compared with the male urchins which had an average GI of 26.8% (±5.4). In conclusion, the present study showed that male and female green sea urchins have the same growth capacity and feed convention ratio but by the end of the experiment the gonad index was significantly higher in female than male urchins.     

Growth,Feed Conversion,and Nutrient Retention Efficiency of African Catfish,Clarias gariepinus, (Burchell) Fingerling Fed Diets with Varying Levels of Protein

Growth, feed conversion, and nutrient retention efficiencies of African catfish fingerling, Clarias gariepinus (5.22 ± .07 cm; 8.22 ± 0.03 g), fed diets with varying levels of protein were assessed by feeding seven casein/gelatin based isocaloric (17.62 kJ/g GE) experimental diets with graded levels of dietary protein (20%, 25%, 30%, 35%, 40%, 45%, and 50% of the diet) to triplicate groups of fish to apparent satiation for eight weeks. Effects of feeding these diets on live weight gain (LWG%), feed conversion ratio (FCR), protein efficiency ratio (PER), protein retention efficiency (PRE%), and energy retention efficiency (ERE%) were assessed. Maximum LWG% (867%), PER (2.01), highest PRE (32%), ERE (69%), best FCR (1.39), and maximum body protein were recorded in fish fed diet containing 35% protein. On the basis of the second-degree polynomial regression analysis of the above response variables, it is recommended that the inclusion of protein in the range of 34.4%–39.6% is optimum for maximizing growth potential, feed conversion, and nutrient retention in African catfish fingerling, Clarias gariepinus.     

四种因子对仿刺参幼参牛长的影响

以益生菌、水温、寡糖和配合饲料为因素,仿刺参幼参的特定生长率为指标,通过L9(34)正交试验方法,研究4种因子对仿刺参幼参生长的影响,获得各因子的最佳组合参数.试验结果显示,4种因子对幼参特定生长率的影响均极显著(P＜0.01),影响因素为益生菌＞水温＞寡糖＞配合饲料.最佳的因素搭配为益生菌5 mL/m3,水温24℃,壳寡糖+褐藻胶寡糖混合0.002 g/L,幼参B型配合饲料.各因素水平对仿刺参幼参特定生长率影响为益生菌5 mL/m3＞15 mL/m3＞10 mL/m3,水温24℃＞17℃＞10℃,壳寡糖+褐藻胶寡糖＞褐藻胶寡糖＞壳寡糖,幼参饲料B型＞幼参饲料加强型＞稚参饲料.     

Growth of Juvenile Synodontis petricola (Family: Mochokidae) Fed on a Formulated Diet, Artemia or Spirulina and Combinations Thereof

Two age groups of juvenile Synodontis petricola (Group I, 0.5 years and Group II, 1.5 years) were reared on each of five diets: formulated dry diet; Artemia; Spirulina; formulated diet plus Artemia; and formulated diet plus Spirulina. Fish were fed for 84 days and weighed and measured every 14 days. Growth of S. petricola averaged 0.06 mm/day for both age groups. There was no significant difference in percent survival between the fish fed on different diets within each of the two groups but the younger fish (0.5 years) had a significantly lower survival percentage (90.3%) than those in Group II (95.3%). Fish in Group I fed on Spirulina alone grew slower than those fed only on formulated dry feed, whereas the growth rates of fish fed on other diets, or diet combinations, did not differ from each other in both age groups. This revised version was published online in August 2006 with corrections to the Cover Date.     

Food Consumption, Absorption, Assimilation and Growth of the Sea Urchin Strongylocentrotus intermedius Fed a Prepared Feed and the Alga Laminaria japonica

Prepared feeds are standard for developed aquaculture programs. Prepared feeds have been shown to be effective for several species of sea urchins. We investigated the use of prepared feeds for culture of the important commercial species Strongylocentrotus intermedius by comparison with the usual food used, the brown alga Laminaria japonica . The experiment was done in the summer and consisted of two successive 30-d periods. Individuals consumed more of the alga than the prepared feed but the absorption efficiencies were the same. This probably resulted from a higher content of structural carbohydrates in the alga and a higher content of available organic matter in the feed. The amount of organic matter absorbed was the same for both foods. However, the amount of gonad production and the assimilation efficiency was greater for the prepared feed. This indicates the prepared feed is of better nutritional quality. The physiological measurements and production were greater in the first 30-d period when the temperature was < 20 C than in the second when it was > 21 C. This indicates temperature will be an important consideration in aquaculture of S. intermedius .     

Effect of Feeding Regime on Compensatory Growth of Juvenile Abalone,Haliotis discus hannai,Fed on the Dry Sea Tangle,Laminaria japonica

Effect of feeding regime on compensatory growth of juvenile abalone (Haliotis discus hannai) fed on the dry sea tangle (Laminaria japonica) was determined. Thirty juvenile abalone averaging 15.7 g were randomly stocked into 18 50‐L plastic rectangular containers each. Six treatments were prepared in triplicate: Abalone were fed the dry sea tangle once a day at a satiation level with a little leftover for 16 wk as the control (Con) and other abalone were fed the dry sea tangle once a day at a satiation level with a little leftover for 15 wk after 1‐wk starvation (S1 treatment), 14 wk after 2‐wk starvation (S2 treatment), 13 wk after 3‐wk starvation (S3 treatment), 12 wk after 4‐wk starvation (S4 treatment), and 10 wk after 6‐wk starvation (S6 treatment), respectively. A linear relationship between weight change of abalone and wk of starvation was observed: Y (Weight of abalone) = ?0.17X (Wk of starvation) + 15.89 (R ² = 0.9462) (P < 0.0001). The highest survival of abalone was achieved in the S2 treatment, but not different from that of abalone in the Con, S1 and S3 treatments. Weight gain of abalone in the Con treatment was higher than that of abalone in the S4 and S6 treatments. Abalone fed on the dry sea tangle seemed to be able to achieve full compensatory growth up to 3‐wk starvation.     

Effects of Feed Type and Temperature on Growth of Juvenile Abalone,Haliotis discus hannai Ino

Effects of feed type and temperature on growth and body composition of juvenile abalone, Haliotis discus hannai Ino, were determined. A 2 (feed types: formulated diet and dry sea tangle) × 3 (temperature conditions: 20, 23 and 26 C) factorial design with triplicate was used. Seventy juvenile abalone averaging 4.7 g were randomly distributed into each of 18, 50‐L plastic rectangular containers. Six containers were placed into each temperature condition of three 1.3 ton concrete flow‐through raceway systems. Abalone were daily fed with either the formulated diet or dry sea tangle once a day to satiation level. Survival was affected by feed type, but not by temperature. Weight gain of abalone was affected by both feed type and temperature. Regardless of temperature, weight gain of abalone fed the formulated diet was better than that of abalone fed the dry sea tangle. Shell length and width were affected by feed type, but not by temperature. In conclusion, weight gain of abalone was affected by both feed type and temperature, but feed type had a stronger effect than temperature. The formulated diet achieved better growth of abalone than the dry sea tangle regardless of temperature and 20 C seemed to be recommendable for abalone among temperature tested.     

Growth and Feed Conversion of Juvenile Heterobranchus longifilis Fed Live Oreochromis niloticus with or without Artificial Feed

Growth and feed conversion were monitored in triplicate groups of the African catfish Heterobranchus longifilis (mean weight 11 ± 1.8 g) fed small (2.5–5.54 cm) tilapia (Oreochromis niloticus) and artificial feeds at various rates (treatments 1, 2, and 3), and tilapia or artificial feed (treatments 4 and 5, respectively). Artificial feed was a 42% crude protein commercial pellet. Live O. niloticus were fed at a rate of 4 g live tilapia/catfish/day. Pelleted feeding rate was 2%, 1%, 0.5%, and 1% of body weight thrice daily in treatments 1, 2, 3, and 5, respectively. After 70 days, mean weight was 180 ± 9.5 g, 157 ± 15.7 g, 147 ± 2.6 g, 77 ± 10.9 g, and 74 ± 10 g, in treatments 1, 2, 3, 4, and 5, respectively. Treatment significantly affected SGR (% day^?1) (P < 0.03) and pelleted feed conversion ratio (P < 0.0003). FCR was 1.09 ± 0.01, 0.63 ± 0.08, 0.42 ± 0.11, and 1.12 ± 0.13 in treatments 1, 2, 3, and 5, respectively. Profit was highest (P < 0.01) in treatment 2. Tilapia consumption seems to improve utilization of artificial feed and may be a way for some catfish farmers to save money.     

The Effect of Astaxanthin in Feed and Environmental Temperature on Carotenoid Concentration in the Gonads of the Green Sea Urchin Strongylocentrotus droebachiensis Müller

The aim of this study was to investigate the long term development of carotenoid concentration in gonads and gonad development of green sea urchins reared at different temperatures and fed formulated feed containing dwerent levels of astaxanthin. Urchins, sampled from a natural population, were reared under two different temperature regimes (7 C and 12 C) and fed formulated feed containing 0, 100 and 500 mg astaxanthin/kg feed, respectively. The study lasted 112 d. Astaxanthin was detected in the groups fed feed containing astaxanthm, but in low quantities. No effect of temperature was observed on the retention of astaxanthin. Echinenone values declined throughout the study, probably due to the lack of suitable metabolic precursor for production of echinenone. Water and lipid concentration in the gonads increased throughout the study indicating the progressions of gametogenesis and the generally improved nutritional status of the animals. No significant difference in gonad index (GI) due to treatment was observed but GI varied between the sexes with male GI increasing significantly faster compared to females.     

凡纳滨幼虾采食不同蛋白水平日粮的免疫与消化率研究

在室内养殖条件下,进行单因素随机设计动物试验,即5种饲料蛋白质水平（31%、35%、39%、43%、47%;以A～E组表示）处理,投喂平均体质量0.2 g的凡纳滨幼虾,养殖60 d。研究结果表明,蛋白质营养对凡纳滨幼虾生长、免疫与抗氧化指标和消化率特征影响显著。随着饲料蛋白水平的升高,特定生长率显著增加,饲料系数下降,E组两项指标最好,分别为5.52和1.96。高蛋白质含量饲料有利于提高对虾免疫指标水平,血淋巴中血细胞浓度、T-AOC活力、POD活力、溶菌酶活力、总蛋白含量,随着蛋白质水平提高显著增加,各项指标E组最高,比A组分别显著提高133.7%、21%、16.8%、20.8%、19.7%(P<0.05);而SOD活力C组最高,与A组差异显著。凡纳滨幼虾对蛋白质的消化率随饲料蛋白质含量增加显著升高(P<0.05),E组比A组提高8.2%。通过饲料蛋白质水平与特定生长的回归分析,获得凡纳滨对虾幼虾最大生长饲料蛋白质需要量为46.5％。     

Effect of Feed Protein and Carbohydrate Levels on Feed Intake,Growth, and Gonad Production of the Sea Urchin,Lytechinus variegatus

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.     

Growth Performance and Proximate and Fatty Acid Compositions of Channel Catfish, Ictalurus punctatus, Fed for Different Duration with a Commercial Diet Supplemented with Various Levels of Menhaden Fish Oil

A 15‐wk study was conducted to evaluate the effect of supplemental menhaden fish oil levels and feeding duration on growth performance and tissue proximate and fatty acid (FA) compositions of juvenile channel catfish, Ictalurus punctatus. Dietary fish oil levels had no effect on final weight gain, feed efficiency, and survival of channel catfish. Tissue lipid contents were directly correlated to dietary lipid levels, while moisture contents were inversely related to dietary lipid levels. Fillet moisture contents progressively decreased, whereas fillet lipid increased with increasing feeding duration. Significant increase in saturated and total n‐3 FAs and decrease in monoenoic and total n‐6 FA in whole body and fillet were observed at each incremental level of dietary fish oil. Percentages of n‐3 and n‐3 highly unsaturated fatty acids in fillet of fish fed the control and 3% fish oil diets decreased with increasing feeding periods, whereas those of fish fed 6 or 9% added fish oil diets remained stable or increased. Ratios of n‐3/n‐6 were statistically comparable throughout the 15‐wk feeding. When expressed in terms of mg/g of fillet, the highest concentration of n‐3 was obtained in fillets of fish fed the 9% added fish oil diet for 15 wk.     

Effect of Dietary Essential Oils Supplementation on Growth Performance,Nutrient Utilization,and Protein Digestibility of Juvenile Gilthead Seabream Fed a Low‐Fishmeal Diet

The present study aimed to assess the efficacy of supplemental plant essential oils (PEOs) on the growth performance and digestive processes of juvenile gilthead seabream. Three experimental diets were tested: (1) a control (CTRL) diet formulated with low marine‐derived protein level (19%); (2) CTRL diet supplemented with a blend of anise, citrus, and oregano essential oils at 1.2 g/kg (diet Phyto C); and (3) CTRL diet supplemented with a similar blend at 0.2 g/kg, but in encapsulated form (diet Phyto E). Triplicate groups of 20 fish (mean initial body weight = 27.9 ± 2.1 g) were fed the experimental diets over 63 d. Results showed that specific growth rate, voluntary feed intake, feed conversion ratio, and protein efficiency ratio were not significantly affected by the two dietary supplements. The commercial blend of PEOs tested here can be successfully incorporated into a low‐fishmeal diet to maximize protein and fat retention and to minimize nitrogenous losses in seabream juveniles. Phyto E presented a decrease in nitrogenous metabolic and fecal losses. The practical implications of including this plant‐based blend in aquafeeds can potentially include faster fish growth and improved production time, but these remain to be tested in a longer experimental trial.     

匙吻鲟仔稚鱼摄食前后生长规律与体脂肪酸组成研究

为了掌握匙吻鲟(Polyodon spathula)仔稚鱼摄食前后的生长规律及其能量代谢情况,研究了孵化后第3、5、7、13、19、25天匙吻鲟仔稚鱼生长特征与体脂肪酸组成变化。结果表明,摄食前匙吻鲟仔鱼全长(L_1)生长方程为:L_1=0.1288t_1+0.7134(3≤t_1≤7),R~2=0.9993;摄食后匙吻鲟仔稚鱼全长(L_2)生长方程为:L_2=0.9133e~(0.0785t_2)(7t_2≤25),R~2=0.9913;2个阶段全长(L)生长方程为:L=0.8948e~(0.0796t)(3≤t≤25),R~2=0.9950。摄食前匙吻鲟仔鱼体重(W_1)生长方程为:W_1=0.0035t_1-0.0032(3≤t_1≤7),R~2=0.9932;摄食后仔稚鱼体重(W_2)生长方程为:W_2=0.0061e~(0.1893t_2)(7t_2≤25),R~2=0.9948;2个阶段体重(W)生长方程为:W=0.0049 e~(0.2004t)(3≤t≤25),R~2=0.9911。2个阶段匙吻鲟仔稚鱼体重(W)与全长(L)的幂函数关系为:W=0.007L~(2.513)。前仔鱼期,随着孵化天数的增加,匙吻鲟饱和脂肪酸(SFA)比例显著升高(P0.05);单不饱和脂肪酸(MUFA)比例显著下降(P0.05);多不饱和脂肪酸(PUFA)比例无显著变化;其中,亚油酸(C_(18)∶2 n-6)、α-亚麻酸(C_(18)∶3 n-3)、n-6 PUFA比例显著下降(P0.05),EPA(C_(20)∶5 n-3)、DHA(C_(22)∶6 n-3)、n-3 PUFA比例显著升高(P0.05);摄食生物饵料后,随着孵化天数的增加,匙吻鲟SFA比例先升高后下降(P0.05);MUFA比例先下降后升高再下降(P0.05);PUFA比例先升高后下降再升高(P0.05);其中C_(18)∶2 n-6先升高后下降,EPA、DHA呈相反趋势(P0.05),C_(18)∶3 n-3先升高后下降再升高(P0.05)。研究表明,随着孵化时间的延长,摄食前匙吻鲟仔鱼全长和体重均呈线性增长,摄食后均呈指数增长,2个阶段匙吻鲟仔稚鱼全长和体重均呈指数增长,体重与全长呈幂函数关系;前仔鱼期,匙吻鲟仔鱼对体内不同脂肪酸利用顺序为MUFAn-6 PUFAn-3 PUFA和SFA;摄食后,生物饵料脂肪酸组成对匙吻鲟仔稚鱼脂肪酸组成的影响日益显著。     

Ingestion, Absorption, and Gonad Production of Adult Strongylocentrotus franciscanus Fed Different Rations of a Prepared Diet

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.