Daily ration of Japanese Spanish mackerel Scomberomorus niphonius larvae

SUMMARY: Diel successive samplings of Japanese Spanish mackerel Scomberomorus niphonius larvae were conducted throughout 24 h both in the sea and in captivity in order to estimate their daily ration. Using the Elliott and Persson model, the instantaneous gastric evacuation rate was estimated from the depletion of stomach contents (% dry bodyweight) with time during the night for wild fish (3.0–11.5 mm standard length) and from starvation experiments for reared fish (8, 10, and 15 days after hatching (DAH)). Japanese Spanish mackerel is a daylight feeder and exhibited piscivorous habits from first feeding both in the sea and in captivity. Feeding activity peaked at dusk. The estimated daily ration for wild larvae were 111.1 and 127.2% in 1996 and 1997, respectively; and those for reared larvae ranged from 90.6 to 111.7% of dry bodyweight. Based on the estimated value of daily rations for reared fish, the total number of newly hatched red sea bream Pagrus major larvae preyed by a Japanese Spanish mackerel from first feeding (5 DAH) to beginning of juvenile stage (20 DAH) in captivity was calculated to be 1139–1404.     

Quantitative estimation of maximum daily feed intake of African catfish, Clarias gariepinus Burchell, fingerlings using radiography

Gastric evacuation rate, return of appetite and satiation time of African catfish, Clarias gariepinus Burchell 1822, fingerlings, fed with a commercial pelleted feed, were determined under experimental conditions. The gastric evacuation rate was described by an exponential function, which was found to be inversely related to the rate of ingestion (return of appetite). Satiation time remained constant over the experimental period. Based on these data the authors estimated maximum daily ration in relation to feeding schedule and feeding frequency for C. gariepinus fingerlings.     

Post-release survival of recreationally caught snapper, Pagrus auratus, in Port Phillip Bay, south-eastern Australia

Abstract  Snapper, Pagrus auratus (Forester), is an important recreational species in marine waters of Victoria, Australia. This study estimated survival for compulsorily released undersized P. auratus by holding fish in cages and tanks for 3 days. In all, 620 P. auratus caught by angling were assessed for post-release survival and 200 additional fish were used as controls. The survival rate was greater for shallow-hooked (97%) than deep-hooked (48%) P. auratus . Post-mortems showed that hooking injuries to the throat and/or gill area caused most deaths, while piercing of the heart also caused mortalities. Removing deeply ingested hooks decreased survival. To estimate survival of P. auratus across the Victorian fishery, this study's results should be combined with estimates of shallow-hooking rates in the fishery. Shallow-hooking rate estimates would quantify the impact of the low survival rate found for deep-hooked fish.     

Gut evacuation in barbel (Barbus sclateri G., 1868) and nase (Chondrostoma willkommi S., 1866)

Abstract– In this study we estimated the rates of summer gut evacuation for two cyprinids with detritivorous-omnivorous feeding habits, Barbus sclateri , Günther 1868 (barbel) and Chondrostoma willkommi , Steindachner 1866 (nase). This study was performed at two sampling stations in the upper Guadalete River (south Spain). A previous study reported differences in the natural diet of both species. The gut evacuation rate was estimated from the regression of gut contents weight against time. Linear and exponential models best described the pattern of gut emptying in the two species. There was no significant difference in the gut evacuation rate between both sampling stations for barbel. However there was a discrepancy related to the model that provided the best fit to empirical data. In contrast, the same model provided the best fit to the empirical data for nase in both sampling stations, but the gut evacuation rate was significantly different in both sampling stations. The results of these study provide the first data of evacuation rates for Iberian freshwater fish species directly measured in the field.     

投喂频率对尼罗系吉富罗非鱼幼鱼胃排空、生长性能和体组成的影响

通过胃排空试验与养殖试验研究了不同投喂频率对尼罗系吉富罗非鱼幼鱼的胃排空、生长性能以及体组成的影响.在试验开始时,观测尼罗系吉富罗非鱼幼鱼的胃内饲料排空情况,胃排空试验结果表明,胃排空率的最佳描述为平方根函数,胃内饲料在饱食投喂后15 h左右完全排空,达到投喂前水平,80％胃排空为9h,也就是投喂后大约9h恢复食欲.360尾试验鱼(初始体质量3.72 g)以不同的投喂频率(1d4次、1d3次、1d2次、2d4次、2d3次、2d2次)分组,每组设立3个平行组,随机养殖于18个网箱中,每箱养殖20尾鱼,按饱食量投饲膨化饲料.养殖期为6周.尼罗系吉富罗非鱼幼鱼在投喂频率为1d4次、1d3次和1d2次时特定生长率和饲料效率显著高于投喂频率为2d4次、2d3次和2d2次时(P＜0.05)；投喂频率为1d2次、2d4次、2d3次和2d2次时其摄食量显著低于1d4次和1d3次时(P＜0.05).随着投喂频率降低,鱼体水分含量逐步上升,脂肪和蛋白质含量逐步下降,其中1d4次、1d3次组鱼与2d2次组鱼有显著性差异(P＜0.05).各投喂频率组间的肝体指数无显著性差异(P＞0.05).3.7～48.0 g尼罗系吉富罗非鱼幼鱼的适宜投喂频率为1d2次,较2d2次、2d3次和2d4次时明显提高了生长速度和饲料效率,较1d3次、1d4次摄食量显著降低.2种试验结果较为一致.     

Diel feeding pattern and ration of two sizes of silver barb, Puntius gonionotus Bleeker, in a nursery pond and ricefield

The diel feeding pattern, electivity and ration of 4.5-6.9 and 11.5-13.6 cm (total length) silver barb, Puntius gonionotus Bleeker, were investigated along with water quality characteristics in a nursery pond and a ricefield in Bangladesh. Small fish had two peaks (0900-1200 h and 1500-1800 h) in feeding activity in the pond but only one in the ricefield at 1500 h. Feeding at high levels went on throughout the day and on moonlit nights for small fish, and their diet was dominated in both environments by aquatic macrophytes as well as Microcystis, Spirogyra, Oedogonium and Cladophora, rotifers, crustaceans and insects. Large fish fed at low levels, had a single feeding peak during midday in the pond but no clear feeding peak in the ricefield. Large fish consumed macrophytes as well as Microcystis, Anabaena, Spirogyra and Cladophora, and crustaceans (in the pond) or molluscs (in the ricefield). Overall electivity was negative for microalgae. Zooplankton were avoided by large fish in the ricefield. The gastric evacuation time was 1-5 h at 27.5-34.0°C. Daily rations for small and large fish were estimated to be 1.4% and 0.3% of body weight in the pond and 1.1% and 0.6% in the ricefield. Improved fish yields may be achieved by stocking small P. gonionotus where the available food resources include important amounts of zooplankton, and by allowing aquatic macrophytes and weeds to grow in the ricefield or pond after stocking, such that the growing fish can feed increasingly on these.     

Gastric evacuation and feeding in the gilthead sea bream reared under semi-intensive conditions

Gastric evacuation rates of the gilthead sea bream, Sparus aurata, fed with commercial pelleted food and polychaetes (Nereis diversicolor) were determined under experimental conditions. The estimated gastric evacuation rate for pelleted food was 7.97% h^–1, with a total time of digestion of approximately 9 h. The respective values for the natural food were 6.24% h^–1, with a total digestion time of approximately 12 h. The daily consumption of fish reared in earth ponds in a semi-intensive aquaculture facility was estimated through 24 h cycles performed between April and August. The daily consumption varied from 18.58 to 31.98 mg g^–1. There was a constant increase in the average daily consumption per individual of 1.8–4.6 g (dry weight). During these cycles, samples of stomachs were taken and the contents preserved for further observation. The feeding behaviour of the reared fish was compared with a fish sample caught in the Ria Formosa lagoon. No common species were found between samples. A total of 38 prey were identified, which suggests that the gilthead sea bream is a non-specific predator. Despite the high abundance of natural prey in the ponds, the dependence of sea bream on pelleted food was high.     

Auditing nutrient discharges from fish farms: theoretical and practical considerations

Nutrient discharges from fish farms can be determined retrospectively, simply and with a high degree of accuracy from records of fish production and feed conversion ratios (FCR), combined with chemical analyses of feed and fish. Prospective prediction of the inputs (via feed and outputs) via production and discharges) of given chemical elements, on a daily basis and over longer periods of time, would represent a valuable management tool for farmers, and for regulatory and planning authorities. A dynamic model is presented for Atlantic salmon, Salmo salar L., which integrates biomass, growth rate. FCR. and nutrient retention and discharges in relation to feeding rate, diet composition and environmental factors. In view of the importance of feeding rate on growth, FCR and nutrient discharges, three simulation alternatives were modelled; namely, feeding 50%. 75 or 100% of the estimated maximum daily ration of a specified diet to salmon smolts of 80 g initial weight over a period of one year in sea water. The 50 and 75% rations, in comparison with 100% ration, showed dramatic reductions in fish weight after one year (0.4 and 1.4 kg versus 3.3 kg). The discharges of nitrogen (N) and phosphorus (P) per unit biomass production were reduced to some extent in the first months of the simulation period, and thereafter, there were no clear differences in discharges of N and P per unit biomass at the three ration levels. However, the accumulated N and P discharges per unit weight gain were slightly increased on the 75% ration, and two-fold higher on the 50% ration compared to the 100% ration. The FCR was also higher in fish fed the lower rations. The simulation result indicates that reduced ration is not effective strategy for minimizing nutrient discharges from fish farms. In order to control discharges within any limits and to utilize the resources optimally, it is better to adjust the biomass on the farm and to feed the fish to appetite, at which growth rate is maximum and FCR is minimum.     

条纹石鮨摄食强度与代谢及能量收支间的关系

设日摄食率为０．４％、１．５％、４．０％三种水平，分别测定条纹石鱼旨Ｍｏｒｏｎｅｓａｘａｔｉｌｉｓ幼鱼的代谢及能量的收支情况。处于饱食（日摄食率４．０％）及维持状态（日摄食率１．５％）下，该鱼代谢率增加的峰值分别于摄食后３ｈ及７ｈ内出现，为静止时代谢水平的２．１０倍和２．４６倍，ＳＤＡ（特殊动力作用）持续时间均为２１ｈ，ＳＤＡ总耗能量分别占摄入能的１３％和３５．８％。条纹石鱼旨在饱食时的转化效率Ｋ（湿重）为２０．８５％。三种摄食水平下条纹石鱼旨的能量收支方程分别为：饱食状态（日摄食率４．０％）时，１００Ｃ＝８．４Ｆ＋７．８Ｕ＋１３．０ＳＤＡ＋３６．９（Ｒｓ＋Ｒａ）＋３３．９Ｇ；维持状态（日摄食率１．５％）时，１００Ｃ＝７．８Ｆ＋４．１Ｕ＋３５．８ＳＤＡ＋５２．３（Ｒｓ＋Ｒａ），其中Ｇ＝０；减重状态（日摄食率０．４％）时，（Ｆ＋Ｕ＋Ｒ）／（Ｃ＋Ｐ１）＝６７．３％，其中Ｃ＋Ｐ１＝１４．４Ｃ＋８５．６Ｐ１，Ｆ＋Ｕ＋Ｒ＝１．８Ｆ＋８．１Ｕ＋５７．４Ｒ。     

Use of a vertical-slot fishway by galaxiids in Western Australia

Abstract –  The Goodga River Fishway is the first vertical-slot fishway in Western Australia and was opened in April 2003 with the aim of increasing the habitat available to two galaxiids; the trout minnow ( Galaxias truttaceus ), a highly restricted freshwater fish species in Western Australia, and the widespread common jollytail ( Galaxias maculatus ). The fishway was designed to function during low flows to coincide with the upstream spawning migration of G. truttaceus . Prior to the opening of the fishway, no fish were found above the Goodga River gauging station (weir), which is approximately 2 km upstream of the river's entrance to Moates Lake. Fish migrations were monitored in each season between April 2003 and February 2005. Galaxias truttaceus utilised the fishway in all sampling periods. Adult fish migrated up the fishway prior to spawning, while large numbers of new recruits (small juveniles) negotiated the fishway during November 2003 and 2004. More G. truttaceus and G. maculatus were captured on the fishway during daylight hours compared with the night; however, larger G. truttaceus were more commonly captured at night whereas G. maculatus on the fishway were larger during the day. The fact that fishway utilisation by G. maculatus was consistent during all samples and new recruits migrated during periods of low flow demonstrates the importance of understanding the migration patterns of the target species when designing fishways.     

The influence of food particle size on gastric emptying and growth rates of fingerling African catfish, Clarias gariepinus Burchell, 1822

This study investigates the effect of feed particle size on gastric evacuation and growth of fingerling African catfish, Clarias gariepinus . Fish (0.97 ± 0.07 g) held in 40-cm diameter tanks at a stocking density of 5 fish L^–1 (25 fish per tank) were presented with one of four sizes of food particles (1, 1.5, 2 and 3 mm diameter). Gastric evacuation rate could be described by an exponential function with small feed particles being evacuated more rapidly: values of 0.076, 0.054, 0.047 and 0.029 were observed for fish fed 1 mm, 1.5 mm, 2 mm and 3 mm food particles, respectively. Growth rates were highest for fish fed the 1.5 and 2 mm pellets. Based on these findings, recommendations are made on the optimum food particle size for C. gariepinus fingerlings.     

Performance factors, body composition and digestion characteristics of gilthead sea bream (Sparus aurata) fed pelleted or extruded diets

The effects of steam pelleting or extrusion of a commercial feed on performance of 2 g (small) and 40 g (large) gilthead sea bream was studied. In addition the apparent digestibility of diets, gastric evacuation time (GET) and trypsin and amylase activities were measured in large fish. Fish size significantly increased protein and energy productive value, body protein and lipid, liver glycogen and liver lipid, however decreased daily growth index, feed intake and feed utilization, body moisture and hepatosomatic index. Extrusion processing decreased feed intake, more strongly for small fish, and increased daily growth index, feed utilization, protein and energy productive value, body protein and lipid. Digestibility of starch and energy increased with extrusion and GET of extruded feed was double that of steam-pelleted conditioned feed (i.e. 544 min versus 284 min). Digestive enzyme activities approached maximum values after 240 min for the pelleted diet, while those of the extruded continued to increase, at higher rates for amylase than trypsin. Pelleted diet indicated higher moisture for stomach digesta, while the moisture of the intestinal precipitate indicated a higher water-binding capacity for the extruded diet. The overall results indicate a better assimilation of the extruded diet, which could result from its prolonged gastric evacuation.     

人工养殖条件下岩原鲤幼鱼排空率与摄食量

在室内微流水养殖条件下,以水蚯蚓(Limnodrilus sp.)为饵料,应用现场胃含物法,研究岩原鲤[Procypris rabaudi(Tchang)]幼鱼的排空率和日摄食量。结果表明:岩原鲤幼鱼摄食强度具有明显的昼夜节律,呈现较典型的单峰分布特征,其摄食强度高峰时间在0:30到6:30;在实验水温18.6℃时,用湿重表示胃含物质量,线性、指数和平方根3种常用模型均可较好拟合岩原鲤幼鱼[体质量(3.30±0.94)g]的排空率实验数据(df=18,P<0.001),综合评价结果进一步表明,其中指数模型拟合度最好,所得模型为St=0.139e-0.169t(r2=0.952,P<0.001);同时得到岩原鲤幼鱼的排空率(以湿重计)为0.169 g/(100g.h)。实验得到养殖岩原鲤幼鱼的日摄食量(湿重)为24.91 g/(100g.d);应用Elliott-Persson模型评估得到自然环境中岩原鲤幼鱼日摄食量(以湿重计)Cd=14.309 g/(100g.d)。研究建立的岩原鲤幼鱼空消化道重(EDW)-体长(BL)-体质量(BW)经验关系式为EDW=0.24(BW/BL)1.547-0.139(n=83,r2=0.89)。研究表明,指数模型最适于描述岩原鲤幼鱼胃排空特征,Flliott-Persson模型在野外环境中岩原鲤幼鱼摄食评估上具有较大适用性。这些结果可为岩原鲤幼鱼摄食生态的定量研究及环境容纳量评估提供基础资料。     

Effect of starving and feeding on some haematological and physiological responses of the Nile catfish, <Emphasis Type="Italic">Clarias gariepinus</Emphasis> exposed to copper at extreme seasons

The lethal concentration for 50% of fish for 96h (96h LC₅₀) of copper (Cu²⁺) was estimated for the Nile catfish (Clarias gariepinus) in extreme seasons, winter and summer, 4.31 and 4.79 mg/l, respectively. The Nile catfish was exposed to 96h LC₅₀ of copper for 7 days in extreme winter and summer. The body indices, haematological parameters as well as some plasma and liver enzyme activities and metabolite level were significantly differed in fish exposed to copper over than those of the control fish. Most of the tested parameters were not significantly different between the control fish of winter and summer (winter, water temperature 18 ± 2°C and summer, 27 ± 2°C). The effect of two ration sizes on copper toxicity in two different seasons on C. gariepinus was justified. It was found that the haematological parameters and the tested plasma activities of enzymes were significantly valid due to season differences. The blood parameters as well as plasma activities of enzymes were significantly differed in fishes fed elevated ration (3%) and exposed to copper challenge. On the other hand, the exploit of low feeding ration (0.5%) along with copper exposure during the examined seasons induced non-significant differences of the tested parameters, from those of the corresponding control. Therefore, the low feeding ration provides some tolerance against the possible water-borne copper exposure.     

An evaluation of radiography in studies of gastric evacuation in African catfish fingerlings

Groups of 3–4 g African catfish (Clarias gariepinus Burchell, 1822; Family: Clariidae) were offered feeds of two types in three combinations: feed with a radio-opaque marker (Ballotini, 0.16–0.25 mm), feed without marker and a 50:50 mixture of marked and unmarked feeds. Stomach contents were estimated by X-radiography and gastrectomy just after meal termination and at different time intervals (4, 8, 12, 16, 20, 24, 32, 40 and 48 h). There were no significant differences among treatment groups confirming that there was no effect of the marker on feed preference and evacuation rate. Estimations of gastric evacuation rate calculated from gastrectomy and by X-ray sampling were not significantly different. Therefore, gastric evacuation rate of African catfish can be accurately estimated by feeding marked feed and then using X-radiography to monitor feed passage through the gut. © Rapid Science Ltd. 1998     

The effect of meal size on the rate of gastric evacuation of burbot, Lota lota (L.)

Abstract– The effect of meal size on the gastric evacuation rate of burbot Lota lota (L.), was determined at a constant temperature of 1.5°C. Burbot were fed vendace Coregonus albula (L.), in varying amounts from 1.0% to 12.6% of burbot weight. Although gastric evacuation rate decreased exponentially with increasing meal size, the absolute amount of food evacuated per day (g. day⁻¹ increased when meal size increased. The estimated maximum daily gastric evacuation rates were 0.8, 1.3 and 1.6 g/day with meal sizes 1%, 5% and 10% of burbot weight (200 g). No difference in gastric evacuation rate was observed between meals of the same size (8 g) but which consisted of either one or three vendace.     

Laboratory investigation of daily food intake and gut evacuation in larvae of African catfish <Emphasis Type="Italic">Clarias gariepinus</Emphasis> under different feeding conditions

Temporary accumulation of ascorbic acid 2-sulfate (AAS) was measured to estimate food intake and gut evacuation in larvae of African catfish. Fish larvae were fed decapsulated cysts of Artemia containing AAS. In a first experiment it was found that no biosynthesis of AAS occurs in the larvae of this species. In a second experiment, the gut contents of the fish larvae fed were calculated as they changed during development. In a third experiment, the gut evacuation rate of fish larvae was determined during continuous and discontinuous feeding regimes in the first five days after the start of exogenous feeding. Food consumption by catfish larvae increased from 46.5% of their body dry weight (BDW) on day 1 after the start of exogenous feeding to 53.8% BDW on day 3. Thereafter, food consumption decreased to 27.8% BDW on day 5. A similar pattern was observed for gut evacuation, which increased during the first days of exogenous feeding and decreased as fish growth continued. The rate of gut evacuation in a continuous feeding regime was significantly higher (P < 0.05) than that under discontinuous feeding. On day 1 post-hatch and 7 h after first food ingestion the fish larvae evacuated 87% of the food in continuous feeding compared with 43% under discontinuous feeding. It was found that gut emptying differs during larval development. Under continuous feeding, on days 1 and 3 post-hatch and 11 h after the first meal 90% of the food was evacuated compared with 71% evacuated on day 5. The advantages and limitations of the AAS method for estimation of food consumption by fish larvae are discussed.     

大阪鲫生物学的研究

本文对大阪鲫的生物学特性进行了研究，主要内容包括：(1)形态特征、生活习性、繁殖习性、食性和胚胎发育的研究；(2)生长速度、起捕率、疾病的试验；(3)丰满度、肌肉的营养成份和氨基酸的测定；(4)染色体、血清蛋白电泳的分析等。同时还将上述各项同东北鲫、本地鲫进行了比较。大阪鲫的性比为1：1，与东北鲫、本地鲫不同。大阪鲫的鳃耙个数多(最多可达120个)，且长而密，其侧突而长分枝，鳃耙与鳃丝等长。成鱼的肠管长度为体长的5．6倍，管细、壁薄、迂回盘曲。大阪鲫的食性广阔，是属于兼食浮游植物的杂食性鱼类。大阪鲫的染色体与本地鲫相同，都是2n=100。大阪鲫具有明显的生长优势，比本地鲫生长快12—46．2％。它的起捕率很高，可达90％以上，比东北鲫(50％)、本地鲫(5％)高得多。大阪鲫的丰满度为3．07—3．24，空体壳占体重的百分比为85—86％，具有较好的经济性状。肌肉中蛋白质、脂肪的含量与本地鲫、东北鲫相近，而水份含量略高于东北鲫，本地鲫。丝氨酸、精氨酸、谷氨酸、丙氨酸、亮氨酸等的含量均比东北鲫、本地鲫略高。大阪鲫的生长速度快，群体产量高，食谱广，经济性状良好，是一种淡水养殖的优良品种。     

Diurnal and seasonal variation in feeding patterns of Atlantic salmon, Salmo salar L., in sea cages

Atlantic salmon, Salmo salar L., in sea cages exhibit feeding patterns that vary both diurnally and seasonally. Hitherto, there are no data reporting feed rate and its variation through a complete annual cycle. Here we present data from Scotland showing diurnal and interseasonal variation in feeding patterns and feeding rates of Atlantic salmon fed daily to satiation from shortly after transfer to seawater until harvest about 11 months later. A major feeding peak regularly occurred soon after dawn, and feeding rates remained high for approximately one hour. Over the remainder of the day, the fish fed at a lower but steady rate. Relative feed intake varied over the trial, being initially high in summer followed by a sharp decline in autumn, and then further declining until fish reached harvest size at the beginning of the following summer. Further investigations of the relationship between variation in circannual feeding patterns and environmental parameters should now be carried out to improve the understanding of the mechanism behind these patterns.     

Oxygen consumption rates of white sturgeon under commercial culture conditions

Oxygen consumption rates of white sturgeon (Acipenser transmontanus) were measured under commercial culture conditions. Mean fish size ranged from 0.09 to 3.8 kg (0.2–8.4 lbs). Mean daily values of oxygen consumption rates ranged from 70–330 mg kg fish⁻¹ h⁻¹. Peak oxygen consumption rates were measured to be as much as twice the mean daily values and were seen to occur in response to feeding for fish fed a ration of less than 2.6% body mass per day. With higher feed rations, peak oxygen consumption rates were a smaller percentage of the mean daily value. Multiple regression analysis showed that 93% of the variations in measured oxygen consumption rate values could be attributed to variations in feed ration.