Design and performance of recirculating aquaculture system for marine finfish broodstock development

Tropical and subtropical climatic conditions in India present an ideal and unique opportunity for being the leader in tropical marine finfish aquaculture. However, the problem persist due to non-availability of marine finfish seed for the culture. In response to this problem, broodstock development of different tropical marine finfishes for seed production was started. The present study was undertaken to design a recirculating aquaculture system (RAS) and studying their performance in managing the various water quality required for the marine finfish broodstock development and breeding. The design of RAS, developed in the present study, included a broodstock tank, egg collection chamber, electrical pump, rapid sand filter, venturi type protein skimmer and biological filter. Two RAS were designed, one was stocked with a demersal fish species, orange spotted grouper (Epinephelus coioides) and the other was stocked with a pelagic fish species, Indian pompano (Trachinotus mookalee) at the rate 1 and 0.5 kg/m³ with a sex ratio of 1:1 and 1:2 (female: male) respectively. Various physio-chemical parameters, viz, total ammonia nitrogen (TAN), nitrite, nitrate, pH, alkalinity, temperature, free carbon dioxide (CO₂) and dissolved oxygen (DO) of both tank water were analyzed to assess the performance of recirculating aquaculture system in maintaining the water quality. Gonadal development of the fishes was assessed and the spawning performance was recorded and finally, economic performance of the system was also evaluated. During the entire experimental period, mean monthly total ammonia nitrogen was less than 0.07 and 0.06 mg L⁻¹ and mean monthly nitrite was less than 0.02 and 0.01 mg L⁻¹ in orange spotted grouper and Indian pompano RAS tanks respectively. The pH (7.8–8.2), DO (>4 mg/L) and alkalinity (100–120 mg/L) were found to be in optimum range in both recirculating aquaculture systems. Carbon dioxide was found to be nil during the entire experimental period in both the systems. In fact these levels were comparable or less than that is reported as the permissible limits for broodstock development. Indian pompano and Orange spotted grouper matured and spawning was obtained with production of fertilized eggs round the year. Economic evaluation showed the price of 10,000 fertilized eggs of orange spotted grouper to be US $ 1.33. The design of RAS devised in the present study is efficient in controlling and maintaining optimum water quality for broodstock development of both demersal and pelagic finfishes. The fishes stocked in RAS attained final maturation and round the year spawning was obtained.     

Status of Biological Studies and Aquaculture Development of the Mud Crab, <Emphasis Type="Italic">Scylla serrata</Emphasis>, in China: An Experimental Ecological Studies

This is an initial paper in a series of overviews of biological research and aquaculture development of the mud crab, Scylla serrata, in China. Results of experimental ecological studies on mud crabs are reported here. As a result of these experimental studies, results that are important for mud crab culture were also discovered and these include, methods to condition and manage broodstock, determination of ecological conditions that are suitable for embryonic development, and the influence of temperature, salinity, diet and larval density on development and survival of larvae. Results of this work will be useful in establishing a good method for artificial mass culture of larvae.     

Serotonin induces ovarian maturation in giant freshwater prawn broodstock, Macrobrachium rosenbergii de Man

This study investigated the effects of serotonin (5-hydroxytryptamine or 5HT) on ovarian development in Macrobrachium rosenbergii de Man. Adult female prawns at the ovarian stage I (spent) were injected with 5HT at 1, 5, 10, 20 and 50 μg g^− 1 body weight (BW) intramuscularly on days 0, 5 and 10, and sacrificed on day 15. The doses as related to the effect could be categorized into three levels: low (1 and 5 μg g^− 1 BW of 5HT), medium (10 and 20 μg g^− 1 BW of 5HT) and high (50 μg g^− 1 BW of 5HT). The low-dose, especially at 1 μg g^− 1 BW, caused prawns to exhibit a significant increase in ovarian index (ovarian weight/body weight × 100) (5.79 ± 0.09%) as compared to the control (1.49%). The ovaries of most of these prawns could develop to stage IV (mature) and contained synchronously mature oocytes while most of the control ovaries remained at stage I and II (proliferative), and contained only oogonia to previtellogenic (Oc1, Oc2) and early vitellogenic oocytes (Oc3). The medium- and high-dose treated prawns exhibited ovaries that could reach stages III and IV and contained various types of oocytes of different maturity. Pretreatment with 5HT receptor antagonist, cyproheptadine (CYP), at 10 μg g^− 1 BW before 5HT injection significantly suppressed the effect of 5HT. Intramuscular injection of the 5HT-primed thoracic ganglion culture medium into CYP-pretreated prawns resulted in the increase of ovarian index about 5–6 times more than in the control, and in the groups injected with 5HT-primed media from muscle strip, eyestalk and brain. The ovaries of most prawn could develop up to stage IV and contained synchronously developed vitellogenic (Oc4) and mature oocytes (Oc5). These findings suggest that 5HT indirectly induces ovarian development and oocytes maturation in M. rosenbergii, probably via a putative ovarian stimulating factor released from the thoracic ganglia.     

Tank culture of yellowfin tuna, Thunnus albacares: developing a spawning population for research purposes

A land-based culture facility for research on yellowfin tuna, Thunnus albacares, was developed at the Achotines Laboratory in the Republic of Panama. Six concrete tanks, and seawater and life support systems were built to maintain a yellowfin broodstock. On average, 50% of the yellowfin caught survived capture and handling, and approximately 30% became broodstock in Tank 1 (17 m diameter, 6 m depth) or Tank 2 (8.5 m diameter, 3 m depth). Each fish was tagged with a microchip implant tag, then weighed, measured, and injected with oxytetracycline (OTC) prior to stocking. Daily rations of primarily market squid, Loligo opalescens, and Pacific thread herring, Opisthonema spp., were regulated based on the feeding activity and energy requirements of the fish. Feeding activity of the broodstock decreased when the water temperatures decreased, and the fish ate decreasing daily rations and increasing calories with increasing size. Spawning occurred in both tanks within 6–8 months of capture. Spawning first occurred in Tank 1 when 24 females ranged in size from 6 to 16 kg and 65 to 93 cm fork length (FL). Spawning was intermittent during the first 2 months and occurred near daily thereafter. Tank size appeared to affect survival rates, the types of mortalities that occurred, and the growth of the fish. Survival rates after 1 year in captivity were higher, and the fish were larger, on average, in Tank 1 than in Tank 2. Most of the mortalities in Tank 1 were the result of wall strikes, which occurred more frequently after the fish reached their highest density of 0.64 kg m⁻³ and sizes greater than 96 cm FL and 19 kg. Non-linear growth models were fitted to the initial stocking sizes and final sizes of fish that died or were removed from Tank 1 during 1996–1999. Estimated growth rates in length (11–48 cm year⁻¹) for fish between 51 and 150 cm FL decreased with increasing length. Estimated growth rates in weight ranged from 9 to 19 kg year⁻¹ for fish less than 19 kg and 20–23 kg year⁻¹ for fish greater than 19 kg. The results of this work demonstrate that the stable environment of a land-based culture facility may be the preferred system for long-term maintenance of a yellowfin broodstock.     

Design and development of a geothermal temperature control system for broodstock management of channel catfish Ictalurus punctatus

A control system was designed to raise and maintain water temperatures within 0.03-ha earthen ponds to a range conducive for spawning (24–30 °C) channel catfish Ictalurus punctatus. Heating was done during February 2001 to April 2001, when temperatures would have otherwise prohibited spawning (<24 °C). Temperature was increased from 10 °C (ambient) by 2 °C per day, and maintained at 27 °C, by the addition of geothermally warmed water (36 °C). The control system substantially increased the controllability and precision of heating ponds compared to manual operation. Systems were designed to control sets of four ponds. In designing this control system, consideration of biological constraints was essential. Reproduction in channel catfish is most strongly influenced by temperature. Because cold fronts are common during the winter and early spring (January–March), it was essential to ensure that pond temperatures did not fall below the range for spawning. Constraints on the heating rate and temperature variability to maintain fish health and stimulate spawning behavior were considered. Components of the control system included temperature measurement devices (type-T thermocouples), a central electronic control unit, electronic switches and electrically actuated ball valves. In response to the temperature sensed by each thermocouple, the controller sent a message to close or open the valve. When the valve was opened, warm water was added to the pond to increase the average pond temperature. Hardware and algorithm design and initial system testing were the major components of this project. The final design incorporated information on relevant biological parameters and safety features including peak pond temperature, independent aeration and water pressure control mechanisms. Initial results indicate successful control of this biological system, and ongoing studies suggest similar mechanisms may be used for additional control objectives. In particular, this system could be used to vary pond temperatures to study biological responses and to cool ponds by addition of well water during summer months.     

贝壳紫菜单孢子和叶状体的研究

贝壳紫菜的叶状体是由丝状体直接产生的。通过试验，笔者发现贝壳紫菜生活史中虽没有壳孢子，但存在着单孢子。由单孢子萌发发生的叶状体在形态上与由丝状体直接发育而来的叶状体相似，而前者的生长速度较后者快。经Ｗｉｔｔｍａｎｎ氏染色法染色，１－３细胞期的单孢子幼叶状体的细胞间不存在胞间联系。本种的单孢子囊仅出现在叶状体成熟阶段，在幼苗期未发现有单孢子放散。由于在贝壳紫菜的生活史中存在果孢子和单孢子而没有壳孢子     

条斑紫菜叶状体色落症的初步研究

通过海区采样，运用光镜和电镜观察等实验方法，研究了条斑紫菜叶状体色落症，并对患病紫菜加工成的干品进行了初步的品质分析。光镜检查结果表明，患病藻体细胞的液泡很大，色素体萎缩或是挤向细胞边缘，藻体基部死亡细胞较多；电镜下患病藻体细胞的红藻淀粉颗粒增多。品质分析显示，患色落症干紫菜的总糖含量明显高于正常干紫菜，粗蛋白、脂肪、色素和游离氨基酸等指标均比正常干紫菜低，尤其是三种呈味氨基酸（Asp，Glu和Ala）所占比例非常低，由此造成紫菜品质低劣，对紫菜质量的影响较大。对健康藻体和患病藻体进行红外线活体吸收光谱的测定结果也表明，患色落症的藻体色素含量极低。用添加营养盐的海水对患色落症的藻体进行培养，发现6d后藻体色泽均有不同程度的恢复，藻体细胞也逐渐恢复到正常。     

饲料中添加不同水平的维生素E对半滑舌鳎(Cynoglossus semilaevis)亲鱼繁殖性能及后代质量的影响

在饲料中分别添加0、200、1200 mg/kg的维生素E(DL-α-生育酚乙酸脂形式)配制成Ec、El和Eh三种试验饲料,饲喂3龄半滑舌鳎亲鱼(雌性1.58±0.19 kg/尾、雄性0.20±0.05 kg/尾)70 d,探讨饲料中添加不同水平的维生素E对半滑舌鳎亲鱼繁殖性能的影响。结果显示,饲料中添加1200 mg/kg的维生素E(Eh组)不仅可以促进亲鱼性腺的发育,提高亲鱼产卵量、浮卵率、受精率、孵化率以及初孵仔鱼长度,而且影响仔鱼质量,仔鱼的成活率、12 d仔鱼长度、生存活力等方面均要高于对照组。而饲料中添加200 mg/kg的维生素E(El组)只对亲鱼性腺的发育和初孵仔鱼长度有一定的促进作用,对亲鱼产卵量、浮卵率、受精率、孵化率没有显著影响(P>0.05)。随饲料中维生素E的增加,血清中SOD的活性显著升高(P<0.05),MDA含量则显著下降(P<0.05)。此外,El和Eh试验组卵中干物质、维生素C的含量,以及卵子脂肪酸中PUFA、n-3PUFA、n-3HUFA和n-6PUFA的含量均要高于Ec组,El和Eh试验组之间的没有显著性差异(P>0.05)。结果表明,在半滑舌鳎亲鱼饲料中添加适量维生素E会亲鱼促进性腺的发育,增加产卵量,提高卵子和仔鱼的质量。在本试验中Eh组(1200 mg/kg)亲鱼的繁殖性能要优于Ec组(0 mg/kg)和El组(200 mg/kg)。     

Hatchery broodstock conditioning of the blue mussel <Emphasis Type="Italic">Mytilus edulis</Emphasis> (Linnaeus 1758). Part I. Impact of different micro-algae mixtures on broodstock performance

Blue mussel (Mytilus edulis) broodstock collected from the Irish Sea during wintertime (November) was conditioned with three different microalgae diets. Positive flagellates (PF) treatment consisted of Pavlova lutherii, Isochrysis galbana (T-Iso), and Chaetoceros calcitrans (1:1:1). Positive diatoms (PD) treatment consisted of Pavlova lutherii, Chaetoceros calcitrans, and Skeletonema costatum (1:1:1). Broodstock animals in the PF and PD treatments were fed a total of 2.4 × 10¹¹ algae cells per day. Animals in the negative flagellates (NF) treatment received only 1/8th of the total amount of algae of the PF diet. The conditioning diets had an impact on spawning success and broodstock fecundity but not on hatching rate, which was similar in all three groups. The best results were obtained with the PD diet where 84% of the conditioned animals spawned and females released 5.0 × 10⁶ eggs on average. Animals belonging to the PF and NF treatments released, on average, only 3.6 × 10⁶ and 1.6 × 10⁶ eggs, respectively. Although the amounts of algae provided to the broodstock animals had no effect on the hatching rate, the D-larvae resulting from the NF treatment were smaller in size than the larvae from the other treatments. Biochemical analysis of the different broodstock groups at the end of the experiment revealed higher carbohydrate levels in group NF than in PF and PD, supporting the theory that gametogenesis is mainly supported by the energy from the glycogen reserves. As far as we are aware this is the first study describing hatchery broodstock conditioning of blue mussels under fully controlled conditions.     

Designing a protocol to evaluate Crassostrea gigas spat production in hatcheries: Identification of critical aspects

The oyster Crassostrea gigas (Thunberg 1793) is one of the most important species for shellfish aquaculture worldwide, and many cultivation activities rely on the use of spat produced in hatcheries. The operation of hatcheries and the efficiency of the processes involved remain largely unknown. We designed a protocol to evaluate 31 elements of the different phases of C. gigas spat production to identify critical aspects. Our survey was conducted in four hatcheries located in Mexico. The results showed that hatcheries operate with an overall fair control of processes. Nonetheless, six critical control items and six below-average control items suggest that some practices are inappropriate for producing high-quality spat. For 16 items, at least one hatchery applies a suitable production process, but only for three items all hatcheries use the best alternative. Major concerns are the few oysters used in spawning processes, the lack of controlled crosses either between them or with other oyster lines, and the current lack of genetic tests. Besides, broodstock pedigree is not documented and the genetic variability of spat is unknown. Additional concerns are that hatcheries have no controls in place for gamete production estimates or for fertilization, hatching, settlement, and survival rates. The protocol seemed adequate to identify the major difficulties faced by hatcheries. These findings set the basis for the improvement of production processes in hatcheries. Potential areas deserving further research are also underlined.