Physical Characteristics of Commercial Pelleted Atlantic Salmon Feeds and Consideration of Implications for Modeling of Waste Dispersion through Sedimentation

Models used to employ waste dispersion from sea cages rarely take into account the physical characteristics of fish feed and faeces. In this study we determine the hardness, friability, water absorption properties and settling velocity of a range of commercial Atlantic salmon (Salmo salar L.) feeds, under defined laboratory conditions.Hardness of large, high energy pellets ( 8.5 mm) was generally greater than that of 6 mm high energy pellets. With the exception of 100 mm pellets, the friability of large pellets was also greater than that of the smaller pellets. Settling velocities were significantly greater at 20 psu than at 33 psu and significantly higher for most pellet types at 10 °C than at 20 °C. Settling velocities for unsoaked pellets were found to increase with pellet size, from a mean of 5.6 cm s^–1 for the smallest pellet (2 mm) to 13.9 cm s^–1 for the 10 mm standard (20 to 24% fat) pellets. The smallest feed pellets (2 mm) had the greatest percentage wet weight increase on immersion, irrespective of salinity. Settling velocities of pellets were not significantly affected by immersion time (0–15 min).Given the water depths at fish cage sites and the settling times involved, it is concluded that it is unnecessary to take account of changes in food pellet settling velocity as a result of immersion. Effects of pellet size and salinity on settling velocity are best incorporated into waste dispersion models through the use of 'look-up' tables.     

Method for determining the physical stability of shrimp feeds in water

Three methods for measuring the water stability and leaching characteristics of shrimp pelleted feeds were developed and tested: static water method, horizontal shaking method and vertical shaking method. Each method was tested using a commercial and experimental pelleted shrimp feed. Both feeds had a pellet size of 2.4 mm × 5.0 mm with similar proximate composition (35% protein and 9% fat). Each test run consisted of leaching c. 2 g of feed at six intervals of immersion time (0, 30, 60, 120, 240, 360 min), two concentrations of salinity (0, 34 ppt), and three different water temperatures (15, 25, 35 °C). A refrigerated circulating water bath was used to maintain the desired level of water temperature. For the static water and horizontal shaking methods, a Buchner filtration apparatus with Whatman filter paper no. 3 (5 μ) was used to separate the remaining pellets from leached water. The vertical shaking method (VanKel) utilized a perforated stainless‐steel basket (381 μ) for leaching and serving as a filter to separate pellets from leached water. For all three methods, the leached feed and original feed samples were dried in a convection oven at 105 °C for 24 h and then cooled in a desiccator. Dried feed samples were weighed and analysed for dry matter retention. Pellet stability was calculated as the ratio of dry matter retention after leaching and dry matter of original samples expressed as a percentage. Results indicated that any method for pellet stability analysis should take into account water temperature and salinity in addition to actual pellet agitation rate to obtain accurate and consistent measurement of pellet disintegration and nutrient leaching. Dry matter retention was different for each shrimp feed with experimental feed (72.8%) showing lower retention than commercial feed (88%) after 6 h of VanKel leaching under normal shrimp culture conditions. The three methods provided reproducible results with both horizontal and vertical shaking methods recommended for routine laboratory analysis because they could provide different degrees of pellet agitation that simulate actual indoor and outdoor shrimp culture conditions.     

Settling velocity and total ammonia nitrogen leaching from commercial feed and faecal pellets of gilthead seabream (Sparus aurata L. 1758) and seabass (Dicentrarchus labrax L. 1758)

The physico-chemical characteristics of particulate wastes of Sparus aurata and Dicentrarchus labrax were investigated. Changes in the dimensions, settling velocity and total ammonia nitrogen (TAN) leached from commercial feed pellets were investigated after soaking. Also, the settling velocity and TAN leached from faecal pellets of these fish were assessed at 15 and 25 °C. The settling velocity of feed pellets was influenced positively by pellet weight and negatively by immersion length as a result of changes in pellet dimensions after soaking. The settling velocity of faecal pellets was determined by pellet weight. The experimental design did not allow identification of any consistent effect of water temperature on settling velocity. Total ammonia nitrogen leaching over time from feed and faecal pellets was successfully explained by means of a first-order kinetic equation. For feed pellets, water temperature significantly affected the speed of the process and the time at which the maximum TAN leached was reached, but did not influence the maximum TAN leached. Leaching was related to feed pellet size, and so the smaller the pellet, the higher the leaching. Total ammonia nitrogen leaching from faecal pellets was greater per unit weight than in feed pellets. However, neither water temperature nor fish species influenced TAN leaching from faeces.     

Dissolved nutrient release from solid wastes of southern bluefin tuna (Thunnus maccoyii, Castelnau) aquaculture

Finfish pens are point sources of dissolved nutrients released from fish metabolism or degradation of solid wastes. Nutrients leaching from uneaten feed and faeces are not usually quantified in mass budgets for these systems, leading to an overestimation of fish retention or deposition to the seabed. In this study, we investigated nutrient leaching from pellets and baitfish feed as well as faeces of southern bluefin tuna (Thunnus maccoyii) into seawater. Faeces were nitrogen depleted (51–54 mg N g⁻¹ dw) and phosphorus enriched (62–72 mg P g⁻¹ dw) compared with feeds (83–111 mg N g⁻¹ dw and 17–21 mg P g⁻¹ dw). Less phosphorus was available for leaching from pellets and faeces of pellet‐fed tuna (5–6%) than from baitfish and faeces of baitfish‐fed tuna (17–21%). The proportion of soluble nitrogen in pellets (15%) was also lower than in baitfish and faeces (35–43%). Leaching loads for a feed conversion ratio of 5 were estimated as 22 and 26 kg N tonne⁻¹ growth when baitfish or pellets were used as feed respectively. Phosphorus loads were estimated as 15 and 4 kg P tonne⁻¹ growth respectively. More than 90% of nitrogen loads, and approximately 50% of phosphorus, are likely to be released into seawater before solid wastes reach the seafloor.     

Effect of organic fertilizer and formulated feed in pond culture of the freshwater prawn, Macrobrachium rosenbergii (de Man): pond productivity

Abstract. The application of different combinations and levels of pellet formulated feed and chicken manure to ponds stocked with Macrobrachium rosenbergii (de Man) did not result in any significant differences in water quality, sediment chemistry, or benthic macroinvertebrate populations. Water chemistry data indicated that all ponds were eutrophic. Chlorophyll was strongly correlated with total nitrogen, but not with total phosphorus, suggesting that nitrogen limited algal biomass. There was evidence that added organic matter was rapidly decomposed and mineralized. The sediments appeared to act alternately as sources and sinks of nutrients, although there was least variation in sediment nutrient levels in the treatment which received manure only. Applied pelleted feed was directly consumed by the prawns. In the absence of pelleted feeds, macrobenthos appeared to limit prawn growth after 1 month of culture. Simple nutrient mass-balance equations indicated that the losses of nitrogen, phosphorus and carbon from the treatments receiving feed were not dissimilar to previously reported values in finfish culture.     

Determining spatial feed distribution in sea cage aquaculture using an aerial camera platform

Within this paper we describe an unmanned aerial vehicle (UAV) based method to estimate the spatial feed pellet distribution in salmon fish-cages and exploit it within a case study to determine the radial pellet distribution for different rotor spreaders and blower configurations. Compared to previously used methods, capturing pellets thrown from a rotary feed spreader in rows of Styrofoam boxes, the UAV based method is simpler and faster to setup and allows to cover a larger portion of the sea cage surface area. We compare results obtained with the Styrofoam box method with results we obtained by an automatic analysis of aerial videos taken by the UAV during feeding experiments. The employed method helps to gain insight into the spatial feed pellet distribution in full-scale salmon fish-cages where the feeding pipe and actual fixation of the spreader may influence the dynamic behaviour of the feeding system. This can also be seen as a step towards a continuous measuring of the feed pellet distribution, particularly in view of possible future feeding systems that may allow to adapt the feed pellet distribution to the actual fish distribution.     

Intrinsic settling rate and spatial diffusion properties of extruded fish feed pellets

Spatial and temporal feed distribution in sea cages are important factors for the farmer, fish and environment due to the strong relation to growth, feed loss, pollution and welfare. This study presents a set of experimentally derived diffusion parameters and settling rates obtained in still water from four sizes and three densities of extruded fish feed pellets commonly used in aquaculture. It was found that pellet size is positively correlated with increased diffusion and that pellet density plays a less important role. Both the size and density of pellets had a significant impact on the settling rate. Results are compared to values obtained during feed production as well as other relevant studies. The findings suggest that parameters related to hydrodynamic behaviour of groups of feed pellets may vary across different pellet types. The results may be applied to refine and parameterize pellet motion in sea cage feeding models, improving estimates of fish behaviour, growth and feed loss.     

Determination of physical behaviour of feed pellets in Mediterranean water

Settled uneaten feed causes the most intense impact under sea cages, and settling velocity of the feed pellets represents a key parameter for waste dispersion models. Even if some data about physical properties of feed pellets have been published in the framework of salmonid rearing, there is a complete lack of information related to the Mediterranean Sea, as regards typical values of temperature, salinity and feed composition for Gilthead Sea Bream (Sparus aurata L.) and Sea Bass (Dicentrarchus labrax L.). In this study we try to fill this lack, determining dimensions, water adsorption properties, floating times and settling velocities of a typical growing sequence of pellets for the species mentioned above, under defined laboratory conditions reproducing Mediterranean Sea water. The settling velocity increases with pellet size from 0.087, for the smallest pellet (3 mm), to 0.144 m s^?1, for the 5 mm pellet. The biggest extruded pellet (6 mm) falls slower (0.088 m s^?1). The floating time before pellet's fall is found to be a critical parameter in determining settling velocity. The latter depends on pellet's size, water temperature and salinity. The examined pellets reach a 42% of weight increase after 10 min of immersion, while no appreciable dimension change is observed. Our results are in part different from previous ones and could play a role in evaluating and modelling Mediterranean aquaculture environmental impact.     

鱼类肠道的碳酸盐结晶物：海水鱼类养殖在碳汇渔业中的地位和作用

鱼类是一个迄今尚未被认知的非常重要的微细碳酸盐沉积物的来源,对海洋固碳有着重要作用,这个发现直接影响到碳汇渔业的内涵.本研究介绍了海洋硬骨鱼类渗透压调节机制及鱼类肠道碳酸盐结晶形成与其肠细胞膜上物质转运之间的关系,着重阐述了鱼类肠道碳酸盐结晶的特征,并论述了通过对特定区域内鱼类生物量和碳酸盐排泄率数据的研究,估计出全球海洋鱼类每年可产生大约1.1亿t的碳酸钙,在海洋总碳酸盐岩泥中占14％以上.研究重点论述了海水鱼类固碳的独特优势潜力,同时,提出为了更好地确定海水鱼类养殖在碳汇渔业中的地位和作用,有必要对主要海水养殖鱼类肠道碳酸结晶物的形成量及其调控机制,碳收支动态模型进行研究,进而合理地估算和测定海水鱼类养殖的碳汇量.     

Manufacturing Different Diet Sizes and Its Effect on Pellet Water Stability and Growth of Three Size Classes of Pacific White Shrimp,Litopenaeus vannamei

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.     

海水鱼养殖碳、氮、磷排放及对环境影响的初步评价——以大西洋鲑养殖为例

依据排放成因,初步建立了海水鱼养殖中二氧化碳排放负荷和排放强度的测算方法;依据竹内俊郎法并综合考虑生物滤池处理效率,初步建立了海水鱼养殖的氮、磷排放负荷和排放强度以及排放总量的测算方法;依据海上生活污水排放标准,初步建立了氮、磷瞬时排放浓度的测算方法;利用浓度限值法测算了黄海冷水团区域氮、磷的环境容量。以大西洋鲑养殖数据为基础,测算了6种养殖模式的碳、氮、磷排放负荷和排放强度,并将测算的氮、磷年排放量、瞬时排放浓度的结果与黄海冷水团区域的环境容量进行比较分析,初步评估了养殖活动对环境的影响。结果显示,网箱养殖模式的二氧化碳排放负荷和排放强度均显著低于其他模式,循环水养殖模式的氮排放负荷和排放强度均显著低于全流水养殖模式,而6种养殖模式之间,磷排放负荷和排放强度的差异不显著,磷排放是制约扩大养殖规模的主要因素。     

Demonstration of salmon farming as a net producer of fish protein and oil

To date aquaculture’s reliance on dietary marine sources has been calculated on a fish weight‐to‐weight basis without considering the absolute amounts of nutrients but this approach neglects the often considerable differences in the nutritional value of fish. We propose simple nutrient‐to‐nutrient‐based dependency measures that take into account these nutritional differences. In the first study reported here, individually tagged Atlantic salmon (Salmo salar) were reared in seawater supplied tanks with feed collection facilities. In the second, commercial net pens were used to grow over 200 000 fish. For both studies, a low marine ingredient feed containing approximately 165 g kg^?1 fishmeal was compared to a control feed (approx 300 g kg^?1 fishmeal) whilst fish oil inclusion was less markedly reduced. The low marine feeds supported similar growth and feed efficiency compared to the control feeds. With the low marine ingredient feeds, the weight of salmon protein and lipid produced through growth exceeded the weight of marine protein and lipid consumed by the fish meaning that salmon farming can be a net producer of fish protein and oil. The amount of n‐3 long‐chain polyunsaturated fatty acids deposited was sufficient to meet current recommendations from human health organizations.     

An acoustic based approach to evaluate the effect of different diet lengths on feeding behavior of Litopenaeus vannamei

Studying shrimp feeding behavior is challenging and, traditionally, studies have been using direct visual observation or video recordings with image analysis under laboratory conditions. Passive acoustics monitoring (PAM) is a non-invasive approach to study feeding behavior of penaeids, as their mandibles emit clicking sounds during feed ingestion. Considering the wide variation available in shrimp diet lengths, our knowledge is still limited about their effects on feeding behavior. The present study was designed to use acoustics to evaluate the feeding behavior of Litopenaeus vannamei fed different diet lengths. A commercial pelleted diet with similar diameter (2.4 mm) and three different lengths was used as treatments “small” (2.35 mm), “medium” (4.26 mm) and “large” (8.42 mm). Three separate trials were performed with fastened shrimp (20 g), using omnidirectional hydrophones and external audio recorders. Our approach started with the characterization of the click acoustic parameters produced by three shrimps when fed the different diet lengths in anechoic chambers (15 L). We then analyze the number of clicks produced per pellet and duration of the clicking activity when shrimp fed a single pellet in individual tanks (1 L). Finally, the acoustic energy of feeding activity and feed consumption, as well as theirs relationship to predict feed intake was evaluated in aquaria (70 L) with five shrimps. The acoustic parameters of isolated clicks were not affected by the different diet lengths, however, doubling the length of the pellet resulted in doubling the number of clicks emitted during feeding activity. The duration of clicking activity per pellet indicated that small pellets are consumed 2.9 and 4.7 times faster than medium and large pellets, respectively. Furthermore, feeding acoustic energy of small pellets decreased rapidly after feed offer, as their faster consumption probably contributed to shrimps achieved satiety earlier than larger diets. Feed consumption was similar among diets length, but significantly correlated with the feeding acoustic energy emitted by L. vannamei, which is a breakthrough in feeding behavioral research. The results highlight the potential and possibilities of an acoustic approach to estimate feed consumption, as well as an alternative to traditional methods in feeding behavioral studies to improve efficiency of feed management.     

Relationship between feed input and sediment quality of the fish cage farms

ABSTRACT: A study was conducted to examine the variation in fish farm sediment quality with varying organic carbon input in the form of feed. In order to elucidate the seasonal variation in farm sediment quality, relation between seasonal organic carbon input, temperature and sediment quality was studied. The sediment ignition loss, redox potential and acid volatile sulfide sulfur (AVS-S) content showed a correlation with annual organic carbon input. The seasonal AVS-S content showed a significant correlation with the seasonal organic carbon input as well as temperature. Multiple regression analysis revealed that both of these factors explicated 80% of the seasonal variation in AVS-S content. Although redox conditions of the sediment could also be correlated with both the organic carbon input and temperature, the latter seemed to have a greater control. Thus, the farm sediment quality could be directly related to the annual organic carbon input to the fish farm under similar hydrographic conditions. Acid volatile sulfide sulfur content exhibited a significant correlation with both the annual as well as the seasonal organic carbon input. Therefore, AVS-S content proved to be a fairly simple and better indicator for monitoring the fish farm environment for effective farm management and sustainable aquaculture. Importance of size of pellets as a factor affecting the feed input-sediment quality relation is also demonstrated in the present study.     

Modelling of surface and 3D pellet distribution in Atlantic salmon (Salmo salar L.) cages

Feed represents the greatest single cost factor in the production of Atlantic salmon (Salmo salar L.). Focusing on the problem of maximising the available feed for the fish while minimising the feed waste, a mathematical model of the feeding process has been developed. The model covers the feed spreader delivering the feed, water currents, pellet sinking speed and turbulent diffusion, fish appetite as a function of temperature, gut fullness and population structure, and is intended as a tool both for optimising general feeding strategies, and to support the daily handling of the feeding process. The process of horizontal and vertical diffusion of feed pellets in the model has been parametrised and validated through two low level validation experiments. Furthermore, global distribution patterns simulated by the model were verified by comparisons with experimental data from the literature.     

Effects of feed processing conditions and acid salts on nutrient digestibility and physical quality of soy‐based diets for Atlantic salmon (Salmo salar)

Two experiments were conducted to investigate effects of feed processing conditions and potassium diformate (KDF) supplementation on apparent digestibility of nutrients in Atlantic salmon (Salmo salar) and physical quality of extruded feed. In Exp. 1, diets with raw or expander pretreated full‐fat soybean meal (FFSBM) at 100 or 120 °C were extruded at 110 °C. Expander pretreatment significantly (P < 0.05) improved the digestibility of arginine, glutamine and tyrosine in Atlantic salmon. The higher digestibility of expander pretreated FFSBM was confirmed in mink (Mustela vison). In Exp. 2, diets with defatted soybean meal (SBM) were extruded at 110, 130 or 150 °C. The results showed that increasing extrusion temperatures significantly (P < 0.05) improved the digestibility of most major nutrients and amino acids in Atlantic salmon. In general, KDF supplementation to FFSBM and SBM diets did not affect digestibility of nutrients in Atlantic salmon or mink. Expander pretreatment and increasing extrusion temperatures increased pellet expansion, while KDF supplementation reduced pellet expansion.     

以PLA、PHBV为碳源的生物絮团技术在海水养殖中的应用

本研究以聚乳酸(PLA)和3-羟基丁酸-co-3-羟基戊酸共聚(PHBV)作为外加碳源,探究在模拟海水生物絮团养殖中,高、中、低盐度下PLA与PHBV碳源释放规律以及对海水生物絮团养殖中水质、微生物多样性及其群落结构的影响.结果显示:PHBV碳源要优于PLA碳源,中盐度更有利于各种营养盐的转化,氨氮质量浓度最终保持在3...     

Performance of Different Types of Commercial Feeds on the Growth of Juvenile Silver Pomfret, Pampus argenteus, under Tank Culture Conditions

The present study was carried out using juveniles of silver pomfret, Pampus argenteus, produced in the hatchery by stripping eggs from spawners collected from the wild during 2004 and 2005 culture period. The experiments carried out during 2004 investigated the efficiency of using salmon feed mixed with cyclopeeze, salmon feed mixed with shrimp meat, salmon feed alone, and shrimp meat alone in the diet using 1 m³ capacity round fiberglass tanks in three replicates for each treatment with flow‐through seawater. The results showed that inclusion of shrimp meat in the diet either with salmon feed or alone give significantly high (P < 0.01) weight gain of up to 1.10 ± 0.06 g/fish/d and significantly lower (P < 0.001) feed conversion ratio compared to that of feeds without shrimp meat. The experiments carried out during 2005 investigated the use of commercially available feeds with feed additives. The results showed that feeding with “Gemma” feed with 54.0% crude protein and 19.0% crude fat or salmon feed with 41.4% crude protein and 23.9% crude fat give significantly high (P < 0.01) growth rates compared to that of pompano feed with 43.0% crude protein and 6.0% crude fat. The results of these investigations although show high growth rate of the fish compared to that of previous observations; there is yet an urgent need to formulate a suitable feed for this fish species for commercial ventures.     

Do changes in Atlantic salmon,Salmo salar L., fillet fatty acids following a dietary switch represent wash‐out or dilution? Test of a dilution model and its application

The fatty acid compositions of fish tissue lipids usually reflect those of the feed lipids, but few attempts have been made to predict the way in which the profiles change or assess the time required for the fatty acid profile to stabilize following a dietary change. The present focus on the influences of vegetable oils and fish oils on the fatty acid compositions and sensory attributes of fish fillets increases the interest in the ability to make such predictions. A dilution model was tested using data for the influences of feed oils (rape/linseed (V) vs. sand‐eel (F)) and dietary fat concentrations (ca. 30% (H) vs. ca. 20% (L)) on the body growth and fatty acid compositions of the fillets of Atlantic salmon, Salmo salar L., parr and post smolt. Fish given HV or LV feeds during freshwater rearing (mass increase from ca. 19 g to ca. 130 g) were switched to HF and LF feeds following parr–smolt transformation. The changes in fillet percentages of 18:1, 18:2 (n‐6) and 18:3 (n‐3) during 98 days of on‐growing in seawater (mass increase from ca. 130 g to ca. 380 g) conformed closely to predictions made on the basis of the dilution model. Model applications require information about the proportionate increase in fillet fat over time, but the relative changes in body mass can be used as a surrogate provided that both fillet yield (as a % of body mass) and fillet fat percentage change little over time. This is not the case for small salmon, but does seem to apply to larger salmon as they approach harvest size. This means that, for large salmon, ratios of changes in body mass can be substituted for ratios in the quantitative change in fillet fat without the introduction of a large error in the prediction of the change in fillet fatty acid profile following the introduction of a novel feed.     

Effects of differently processed diets on growth,immunity and water quality of the sea cucumber,Apostichopus japonicus (Selenka, 1867)

The type of formulated diet used in aquaculture systems affects the feed efficiency and water quality. In this study, the water quality, growth performance and immunity of the sea cucumber, Apostichopus japonicus (Selenka, 1867), fed diets produced using four different processing methods (extruded pellet diet, cold‐bonded pellet diet, flake diet and mash diet) were quantified for 60 days to identify the optimal feed type for culturing of this species. Sea cucumbers grew faster, the feed conversion ratio was much lower, and immunity indicators were higher when fed the extruded pellet diet compared to the other diets. Sea cucumbers fed the extruded pellet diet had the highest specific growth rate (0.96), whereas A. japonicus fed the cold‐bonded pellet diet had the lowest specific growth rate (0.51). The lysozyme activity of sea cucumbers fed the extruded pellet diet was higher (57.52) than that of A. japonicus fed the cold‐bonded pellet diet (39.22), flake diet (37.32) and mash diet (32.68). When animals were fed the mash diet, the ammonia–nitrogen, nitrite–nitrogen and phosphate productions were higher than in animals fed the other diets. These results indicate that the extruded pellet diet is the optimum feed type for use in the culture of A. japonicus.