Volume 61, Issues 1-4, 2009

Optimal Dose of Total Residual Oxidants for Hybrid Tilapia (Oreochromis mossambicus x O. niloticus) and Whiteleg Shrimp (Litopenaeus vannamei) in Ozone-Treated Sea Water

Lee, Hung-Tsai; Lee, Hung-Jen; Wang, Jih-Temg; Leu, Ming-Yih; Meng, Pei-Jie — Thu, 01 Jan 2009 00:00:00 GMT

The purpose of this study was to use total residual oxidants (TRO) as an indicator for determining the optimal ozone dosage needed to control water quality and thereby enhance survival of cultivated aquatic organisms. When the TRO concentration was maintained at 0.16 mg/l for two hours, the total bacteria plate count dropped from 7.7 x 103 CFU/ml in the untreated sea water to less than 10 CFU/ml in the ozone-treated sea water. The TRO con- centration in the ozone-treated water was well below the 96-h LC50 for hybrid tilapia (Oreochromis mossambicus x O. niloticus) and whiteleg shrimp (Litopenaeus vannamei) determined in this study. Hence, adjust- ment of the ozone concentration in aquacultural sea water is a viable option that simultaneously kills the majority of harmful bacteria in the water and enhances survival of cultivated aquatic organisms.

Changes in Copper Content of Allogynogenetic Silver Crucian Carp after Application of Copper Sulfate to Fishponds

Liu, Jinlan; Yang, Guang — Thu, 01 Jan 2009 00:00:00 GMT

Copper sulfate was applied to freshwater fishponds containing allogyno- genetic silver crucian carp and changes in the copper content in fish tissues were measured. The copper content in blood, gill, amd liver went up quick- ly, but remained high for a relatively short time. Twenty-four hours after application, the copper content in the gill and liver reached their highest lev- els, 4.846 mg/kg and 6.624 mg/kg, respectively. The copper content in the blood reached its maximum of 22.125 mg/l three days after application. The copper content in the kidney also reached its maximum, 17.472 mg/kg, on day 3 but the high copper content prevailed until the end of the 20-day observation. The copper content in the muscle reached its maximum, 1.873 mg/kg, on day 7 and its minimum, 0.6 mg/kg, after two weeks.

Evaluation of the New Fluorescent Internal Tag (Soft Visible Implant Alphanumeric Tag) in the Freshwater Prawn, Macrobrachium rosenbergii

Thu, 01 Jan 2009 00:00:00 GMT

The new version of the polyester visible implant alphanumeric tag (VI Alpha tag; Northwest Marine Technology Inc., Shaw Island, Washington, USA) was evaluated in the giant river prawn (Macrobrachium rosenbergii) under laboratory conditions. The new VI Alpha tag is soft and fluorescent with an alphanumeric code designed to identify individual specimens. Two tag sizes - standard (1.0 x 2.5 mm) and large (1.5 x 3.5 mm) - were tested on juve- niles (standard size), subadults (standard size), and adults (large size) for 10 weeks. Retention, readability, and effects on growth and survival were evaluated. Final mean tag retention was 71.25±3.3% in juvenile prawns, 91.3%±2.73 in subadult prawns, and 59.0%±1.65 in adult prawns. Final tag readability was 100.0% in juveniles, 88.6±5.3 in subadults, and 77.8±4.8 in adults. Average daily growth (mg/day) and SGR (%/day) of tagged juvenile prawns (22.4±0.23 and 0.81±0.02, respectively) did not significantly differ (p>0.05) from that of the untagged control (20.5±1.47 and 0.83±0.04). Similar results were observed in subadult and adult M. rosenbergii. Mean final survival did not significantly differ (p>0.05) between tagged and untagged prawns. Results indicate that tagging M. rosenbergii with VI Alpha tags has no adverse effect on survival or growth and can therefore be effec- tively used to identify individuals in selective breeding programs.

Bacteria in Rainbow Trout (Oncorhynchus mykiss) in the Southern Black Sea Region of Turkey - A Survey

Kayis, Sevki; Capkin, Erol; Altinok, IIhan — Thu, 01 Jan 2009 00:00:00 GMT

Thirty-two freshwater rainbow trout (Oncorhynchus mykiss) farms, two rain- bow trout marine cages, and one research station in the Black Sea region of Turkey were surveyed for bacterial pathogens and diseases in 2006- 2008. Forty bacterial isolates were phenotypically identified in 558 fish. Yersiniosis, furunculosis, vibriosis, motile Aeromonas septicemia, bacterial cold water disease, and Pseudomonas infection were recorded. Infections caused by Yersinia ruckeri, A. hydrophila, and A. salmonicida occurred most frequently, but one or two outbreaks of P. putida, Flavobacterium psy- chrophilum, and P. luteola infection were also recorded. Most of the bacte- ria were isolated in spring and summer rather than fall and winter. Susceptibility to antibiotics was fairly consistent regardless of geographic area or year of isolation. Fifty percent or more of the bacteria were resistant to ampicillin, cephalothin, erythromycin, neomycin, sulfamethoxazole, tetra- cycline, and O/129. The most effective antibiotics were oxolinic acid and flo- refenicol.

Interaction of Spirulina with Different Levels of Vitamin E on Growth, Reproduction, and Coloration in Goldfish (Carassius auratus)

James, Raja; Vasudhevan, Iyyadurai; Sampath, Kunchitam — Thu, 01 Jan 2009 00:00:00 GMT

The interaction between spirulina (30 g/kg diet) and different levels of vita- min E (100, 200, 300, and 600 mg/kg diet) on growth, gonad weight, repro- duction, and coloration were studied in goldfish, Carassius auratus, for 120 days. The mean body weight increased with time in all experimental diets. Growth, gonad weight, and fecundity in fish fed the diet containing spiruli- na+300 mg vitamin E were significantly (p<0.01) enhanced, compared to other diets. Supplementation of vitamin E beyond this level significantly (p<0.01) reduced gonad weight and, subsequently, fecundity. Control fish spawned only once, with fewer eggs per spawn, than other groups, which spawned twice with a greater number of eggs per spawn. Females fed spir- ulina without vitamin E laid 703 eggs in two spawnings compared to 1057 eggs in fish fed with the spirulina+300 mg vitamin E diet. Fish treated with other combinations laid fewer eggs. While all combinations of spirulina and vitamin E significantly enhanced coloration, the combination of spiruli- na+300 mg vitamin E was the most influential.

Effects of Selenium on the Activity of Antioxidant Enzymes in the Shrimp, Neocaridina heteropoda

Thu, 01 Jan 2009 00:00:00 GMT

The effects of a selenium-supplemented diet on the antioxidant enzyme activity of superoxide dismutase (SOD), catalase (CAT), and glutathione peroxidase (GPX) in muscles of the shrimp, Neocaridina heteropoda, were investigated. Purified diets with six levels (0, 0.15, 0.30, 0.45, 0.60, and 0.75 μg/g) of supplemental Se were fed to N. heteropoda for three months. CAT and GPX activity was determined after one month and SOD activity was determined every month. The activity of the enzymes was dose dependant; activity of all three enzymes was significantly higher in shrimp fed Se-sup- plemented diets than in those fed the unsupplemented control diet. SOD activity significantly rose and fell during the three months and was higher in the second month than in the first or third. For all three enzymes, antioxi- dant activity reached a maximum when the Se concentration was 0.45 μg/g.

Evaluation of Feed Stimulants in Diets for Sea Bream (Sparus aurata)

Thu, 01 Jan 2009 00:00:00 GMT

Six isoprotein and isolipidic diets were formulated to investigate the effect of dietary additives on growth and feed efficiency of sea bream (Sparus aura- ta) fry fed a fishmeal-based diet for 80 days. The additives (protorsan, hydrolyzed fish protein, squid meal, krill meal, and betaine + inosine-5’- monophosphate) were added to the diets at the expense of fishmeal. The specific growth rates of the fish ranged from 2.17-2.18% per day for the pro- torsan and control groups to 2.42% per day for the group fed the squid addi- tive. Significant differences (p<0.05) in final body weight and specific growth rate were detected only between the protorsan and control groups and the squid additive group. The feed conversion ratio ranged from 1.04 in the group fed hydrolyzed fish protein group to 1.24 in the group fed krill with no statistically significant differences (p>0.05) between treatments. The feed stimulating action of taurine was tested by observation. Pellets coated in a taurine solution were more actively consumed than control pellets during the morning feeding but consumption did not differ during the afternoon feeding.

Effects of Seminal Plasma Composition on Sperm Motility in Mirror Carp (Cyprinus carpio)

Bozkurt, Yusuf; Ogretmen, Faith; Secer, Faik Sertel; Ercin, Ugur — Thu, 01 Jan 2009 00:00:00 GMT

This research provides data concerning the biochemical (ionic and organic) composition of sperm of the mirror carp (Cyprinus carpio) and its relation- ship to spermatozoa motility. Seminal plasma contained 67.12±1.06 mM/l Na+, 105.1±2.24 mM/l K+, 7.85±0.67 mg/dl Ca2+, 2.61±0.11 mEq/l Mg2+, 0.14±0.002 g/dl total protein, 10.3±1.01 mg/dl triglyceride, 6.83±0.72 mg/dl cholesterol, and 54.72±3.49 mg/dl urea. A positive relationship (p<0.05) was determined between Na+ and motility (r = 0.522). On the other hand, Ca2+, K+, and Mg2+ ions negatively correlated (p>0.05) with motility (r = -0.565, r = -0.160, and r = -0.184, respectively). Spermatozoa motility correlated negatively (p>0.05) with protein (r = -0.233), triglyceride (r = -0.348), and urea (r = -0.331) but positively with cholesterol (r = 0.012). This information will help to develop cryopreservation procedures, to meet species-specific extender requirements, and to optimize artificial fertilization procedures in mirror carp.

Herbal Extract Effects on White Spot Syndrome Virus (WSSV) in Shrimp (Penaeus monodon)

Thu, 01 Jan 2009 00:00:00 GMT

Synthetic drugs and chemicals used in aquaculture cause disadvantageous side effects, while medicines made from medicinal herbs are non-toxic, easy to use, and pollution- free. Many medicinal herbs have potent antiviral properties. The extract of Phyllanthus amarus is a lignan composed of the compounds: niranthin, phyllanthin, and hypophyllanthin which have an impact on the white spot syndrome virus (WSSV) in the shrimp, Penaeus monodon. The virucidal activities of the three substances were tested by mixing them with WSSV, followed by injection into healthy shrimp. The quantity of WSSV DNA on the gills of tested shrimp was measured before and seven days after injecting the mixture. The quantity decreased significantly after injection. Anti-virucidal activities were also assessed by observation of the mortality rates of injected shrimp. The lignan compound inactivated the virus when injected in P. monodon at a dose of 100 mg per kilogram body weight. The survival rate of the lignan injected shrimp was 96.67% , compared to the positive control in which it was only 3.33% .

Infectious Myonecrosis Virus (IMNV) in Pacific White Shrimp (Litopenaeus vannamei) in Indonesia

Taukhid; Nur’aini, Yani Lestari — Thu, 01 Jan 2009 00:00:00 GMT

Penaeid shrimp culture has become a leading export fishery in Indonesia. The Pacific white shrimp (Litopenaeus vannamei) was unofficially intro- duced to Indonesia in 1999, and received government approval in 2001. By the end of 2007, the Pacific white shrimp was cultured in over 17 provinces. The main constraints of shrimp culture have always been diseases, espe- cially those caused by viral agents. Taura syndrome (TS) disease was detected in Indonesia in 2002 and the disease currently affects at least ten provinces. Infectious myonecrosis (IMN) is an emerging L. vannamei dis- ease, first detected in Indonesia in May-June 2006. IMN disease causes significant mortality in growout ponds and is characterized by acute onset of gross signs: focal to extensive whitish necrotic areas in the striated mus- cle, especially of the distal abdominal segments and the tail fan. The white necrotic areas redden, similar to the color of cooked shrimp. The outbreak results in elevated mortality that was initially associated with a chronic course of persistent low level mortality. To date, IMN has been detected in East Java, Bali, and West Nusa Tenggara provinces. This paper reviews studies of IMN disease of Pacific white shrimp in Indonesia: outbreaks, sur- veillance, diagnosis, and control measures.

Study on the Pathogenesis of the White Spot Syndrome Virus (WSSV) on Juvenile Penaeus monodon in Vietnam

Thu, 01 Jan 2009 00:00:00 GMT

The white spot syndrome virus (WSSV) causes disease and mortality in cul- tured and wild Penaeus monodon. In this study, specific pathogen-free P. monodon were injected with WSSV to determine in which primary organs the virus replicates and to analyze viral spread. Shrimps were injected with a low SID50 endpoint (shrimp infectious dose resulting in 50% infected shrimp) of 101.5 or a high SID50 of 104 of the virus. Six shrimps per treat- ment were collected at 0, 3, 6, 9, 12, 15, 18, 21, 24, 30, 36, 42, 48, 54, and 60 h post injection (hpi) for detection of the virus in tissues from 10 organs by immunohistochemistry. In shrimps injected with the low dose, WSSV- infected cells were first detected in the heart and antennal gland 12 hpi, then in the foregut, stomach, and gills at 18 hpi. The integument was infect- ed 24 hpi and the hematopoietic tissue, lymphoid organ, midgut, and con- nective tissues 36 hpi. In shrimps that received the high dose, the heart, antennal gland, stomach, gill, and connective and hematopoietic tissues were WSSV-positive 12-15 hpi while the foregut and cuticular epithelium were positive 18 hpi and the lymphoid organ and midgut were positive 21 hpi. The present study confirmed the replication of WSSV in P. monodon heart, antennal gland, foregut, stomach, gills, cuticular epithelium, hematopoietic tissue, connective tissue, and lymphoid organ.

Viral Infections of Macrobrachium spp.: Global Status of Outbreaks, Diagnosis, Surveillance, and Research

Hameed, A.S. Sahul — Thu, 01 Jan 2009 00:00:00 GMT

Macrobrachium rosenbergii, a global and economically important cultured freshwater prawn, is farmed on a large scale in many countries. Compared to penaeid shrimps, M. rosenbergii is a moderately disease-resistant species. However, viruses such as Macrobrachium hepatopancreatic parvo-like virus (MHPV), Macrobrachium muscle virus (MMV), infectious hypodermal and hematopoietic necrosis virus (IHHNV), white spot syn- drome virus (WSSV), Macrobrachium rosenbergii nodavirus (MrNV), and extra small virus-like particle (XSV) have been reported and are responsi- ble for economic losses to freshwater prawn culture. MrNV and XSV, the causes of white tail disease (WTD), have been reported as dangerous viruses to M. rosenbergii, resulting in 100% mortality in postlarvae and juve- niles within five days of infection. Clinical signs of WTD include lethargy and opaqueness of the abdominal muscle. Various aspects of WTD are dis- cussed in this paper, including tissue tropism of the causative viruses, host range, virus structure, vertical transmission, pathogenicity, and the possibil- ity of multiplying MrNV and XSV in a mosquito cell line.

Current Status of Viral Diseases in Asian Shrimp Aquaculture

Flegel, T.W. — Thu, 01 Jan 2009 00:00:00 GMT

The giant or black tiger shrimp, Penaeus monodon, was formerly the dom- inant cultured shrimp species in Asia. Since approximately 2002, it has been essentially replaced by the domesticated American whiteleg shrimp P. vannamei. The change in dominant species has affected disease concerns. For both species, white spot syndrome virus (WSSV) and yellow head virus (YHV) are the most lethal. For P. monodon, the next most important dis- eases are hepatopancreatic parvovirus (HPV) and monodon baculovirus (MBV). For P. vannamei, they are taura syndrome virus (TSV) and infec- tious hypodermal and hematopoietic necrosis virus (IHHNV). TSV was introduced to Asia in 1998 by careless importation of shrimp stocks for aquaculture but has not been reported to cause problems with local crus- tacean species. IHHNV, which is endemic in Asia, is harmless to P. mon- odon but poses a constant threat to IHHNV-free stocks of P. vannamei if they are hatched and reared in Asia under non-biosecure conditions. An emerging disease for P. monodon is monodon slow growth syndrome (MSGS), a component of which seems to be Laem-Singh virus (LSNV). Infectious myonecrosis virus (IMNV) is a P. vannamei disease, first report- ed from Brazil but now reported in Indonesia where it was probably intro- duced by careless importation of shrimp aquaculture stocks. So far, IMNV has not been reported in other Asian countries. Penaeus vannamei nodavirus (PvNV) is a new pathogen first reported from Belize in 2004 with gross and histological signs that are indistinguishable from those of IMNV. The disease has not yet affected Asian culture. A more recent disease of P. vannamei in Asia is abdominal segment deformity disease (ASDD), possi- bly caused by a yet unknown local virus.

Hemorrhage Disease of Cultured Tra Catfish (Pangasianodon hypophthalmus) in Mekong Delta (Vietnam)

Ly, Loan Thi Thanh; Nguyen, Du Ngoc; Vo, Phuong Hong; Doan, Cuong Van — Thu, 01 Jan 2009 00:00:00 GMT

This study investigated hemorrhage disease in cultured tra catfish (Pangasianodon hypophthalmus) from An Giang, Ben Tre, Can Tho, and Vinh Long provinces in the Mekong Delta (Vietnam). The disease is characterized by internal organ necrosis, white (spot) nodules in the liver, kidney, and spleen, and petecchial hemorrhages on the tail, fins, and abdomen. Some fish have exophthalmus (pop eye), a reddish and swollen anus, and yellowish fluid in the peritoneal cavity. Moribund fish lose their appetite and swim at the sur- face. Bacteria isolated from the diseased fish consisted of Aeromonas hydrophila (38.8%), A. sobria (4.1%), A. caviae (2.0%), Edwardsiella ictaluri (4.1%), and a gram positive, anaerobic bacteria, Clostridium sp. (40.8%). Histological analyses showed necrotic cells and intranuclear, randomly- arranged, straight rod cells (1.0-1.5 x 3.0-4.0 μm) concentrated in the ulcers. Challenge test with A. hydrophila induced external signs of hemorrhagic dis- ease. Challenge test with Clostridium sp. confirmed the presence of the bac- teria in infected tissues with development of white nodules similar to those in naturally-infected fish. Fish challenged with E. ictaluri exhibited gas bubbles in the stomach and gut with a foul smell. Reovirus-like particles were seen by transmission electron microscopy. Further study is needed to determine the role of each pathogen alone and together with others in the pathogenesis of hemorrhage disease of tra catfish.

Surveillance of Emerging Fish Viral Pathogens in Some Southeast Asian Countries

Thu, 01 Jan 2009 00:00:00 GMT

Preventing the transboundary movement of fish viral pathogens in a global environment requires active surveillance. This study examined the presence of three emerging viral pathogens among koi, common, grass, and silver carp in Cambodia, Lao PDR, Myanmar, Philippines, and Vietnam. The stud- ied viruses included koi herpesvirus (KHV), spring viremia of carp virus (SVCV), and grass carp reovirus (GCRV). Detection methods consisted of virus isolation by cell culture, infection assay in naive fish, polymerase chain reaction (PCR), and reverse-transcriptase PCR (RT-PCR). Tissues were collected and pooled from 193 fish samples in Dec. 2004 to Feb. 2005, 406 in Sep. 2005 to Feb. 2006, and 1302 in Oct. 2006 to Feb. 2007. For cell cul- ture, tissue filtrates were prepared from pooled spleens, kidneys, livers, and gills and inoculated onto koi fin (KF-1), grass carp kidney (GCK), and fat head minnow (FHM) cells. For infection assay, tissue filtrates were injected intraperitoneally to healthy, naive common carp. No virus was detected after three cell culture passages and the infection bioassays. One-step and nest- ed-step PCR was used to detect KHV in gills of fish samples. One-step and semi-nested RT-PCR was used to detect SVCV and GCRV in the spleens, kidneys, and livers of fish samples. Samples from all three years from all five countries yielded negative results for all three viruses, indicating that KHV, SVCV, and GCRV were not present in these five countries during the period of the study although KHV outbreaks had been detected in Indonesia, Taiwan, Japan, Thailand, China, and Malaysia.

Current Knowledge on Viral Nervous Necrosis (VNN) and its Causative Betanodaviruses

Nakai, T.; Sugaya, T.; Nishioka, T.; Mushiake, K.; Yamashita, H. — Thu, 01 Jan 2009 00:00:00 GMT

Viral nervous necrosis (VNN) or viral encephalopathy and retinopathy (VER) caused by betanodaviruses (Nodaviridae) has seriously damaged global marine aquaculture since its first appearance in the late 1980s. In the past two decades, more than 100 papers have been published on the dis- ease. Although information is still limited, we now have more knowledge on the taxonomic position and molecular characteristics of betanodaviruses, and on the diagnosis, control, and infection mechanisms of the disease. This paper briefly reviews studies on VNN and betanodaviruses.

Hemorrhagic Disease of Grass Carp: Status of Outbreaks, Diagnosis, Surveillance, and Research

Jiang, Yulin — Thu, 01 Jan 2009 00:00:00 GMT

Hemorrhagic disease of grass carp is the most serious infectious disease of grass carp and causes significant losses of fingerlings. The main clinical signs are external and internal hemorrhage. The disease is caused by aquareovirus and has several serotypes. The optimal epidemic temperature of this disease is 25-28°C. The disease can be transmitted by water or par- asite bite. Susceptible hosts are grass and black carp. Other cyprinids are only carriers. Vaccination can control hemorrhagic disease of grass carp. An inactivated vaccine prepared from organs of sick fish is simple and easy to produce with good efficacy. In China, hemorrhagic disease of grass carp was prevalent but has been controlled by wide application of the vaccine. In other Southeast Asian countries, it is a new disease. For surveillance and diagnosis of hemorrhagic disease of grass carp, isolation of the virus using carp kidney (CK) cells and reverse transcriptase polymerase chain reaction (RT-PCR) are the main methods of detection.

Spring Viremia of Carp Virus (SVCV): Global Status of Outbreaks, Diagnosis, Surveillance, and Research

Goodwin, Andrew E. — Thu, 01 Jan 2009 00:00:00 GMT

The spring viremia of carp virus (SVCV) is an OIE-listed rhabodovirus his- torically responsible for losses of cultured fish in Europe. Acute disease is associated with high mortality, especially in common carp Cyprinus carpio during their first spring season when water temperatures are 10-15°C. Mortality has been reported in other cyprinids and in the Wels catfish Siluris glanis. The disease is characterized by hemorrhages on the skin and bloody mucus in the intestine, clinical signs shared by other diseases including bacterial infections. In 2002, SVCV was detected on a large koi farm in the USA. The USA isolate was 98% identical to isolates associated with koi and goldfish imported from China, but distantly related to European strains. In spring 2002, a major SVCV kill of common carp occurred in Cedar Lake, Wisconsin. This isolate was also of the Asian type, as were subsequent isolates from wild and cultured fish in several states. In the USA, all infected farmed populations were destroyed and no additional iso- lates have been detected since 2004. One of the most critical aspects of SVCV diagnosis is to differentiate the disease from the koi herpesvirus (KHV). The most obvious difference is that KHV generally occurs in tem- peratures of 20-28°C while SVCV disease occurs below 18oC and com- monly at 10-15°C.

Koi Herpesvirus: Status of Outbreaks, Diagnosis, Surveillance, and Research

Yuasa, Kei; Sano, Motohiko — Thu, 01 Jan 2009 00:00:00 GMT

Koi herpesvirus (KHV; Cyprinid herpesvirus 3) is a major threat to common carp and koi carp production worldwide. It is listed by the World Organization for Animal Health (OIE), and has been reported in 26 coun- tries. KHV was designated a Specific Disease by Japanese law in 2003. Japan’s National Research Institute of Aquaculture (NRIA) is a reference laboratory for the disease and conducts confirmatory diagnosis. The num- ber of disease occurrences in Japan peaked in 2004, but has been gradu- ally decreasing since then. The disease occurs mostly during spring and autumn when water temperatures are 16-28°C. In general, conventional polymerase chain reaction (PCR) is the most useful method for diagnosing KHV due to its high sensitivity, high specificity, and rapidity. More recently, real time PCR, nested PCR, and loop-mediated isothermal amplification (LAMP) were developed to diagnose the virus. Reverse transcriptase poly- merase chain reaction (RT-PCR) targets mRNA of KHV to detect the repli- cating virus. An enzyme-linked immunosorbent assay (ELISA) detects anti- KHV antibodies in carp serum of surviving infected fish and is expected to be a tool for surveillance of KHV. However, cross reactions with anti- Cyprinid herpesvirus 1 antibodies in the ELISA need to be resolved. A sys- tematic research project on development of diagnostic and prevention tech- nologies for KHV disease was conducted in 2004-2006 by the NRIA in cooperation with Japanese universities and enterprises and SEAFDEC. The fruitful results of the project are included in this review.

The Effects of Different Sized Granules and Particle Composition on Growth of Rainbow Trout (Oncorhynchus mykiss)

Thu, 01 Jan 2009 00:00:00 GMT

Three feeding regimes were tested to determine their effects on growth, survival, and feed conversion in rainbow trout alevins for 60 days. In the first regime, the alevins were fed a starter feed consisting of 800 micron parti- cles for the first 15-day period. For the following 15-day period, the alevins were given a starter feed consisting of 1200 micron particles. For the final two 15-day periods, the alevins were given feeds consisting of 1500 micron and 2 mm particles, respectively. In the second regime, feed particles in the four periods were 1200 micron, 1500 micron, 2 mm, and 3 mm granules, respectively. In the third regime, feeds contained 1500 micron, 2 mm, 3 mm, and 4 mm granules. During the first two 15-day periods, no significant dif- ferences in growth parameters were detected (p>0.05). In the second two 15-day periods, there were significant differences in final live weight, growth, and feed conversion rates between groups (p<0.05). Growth was lowest in the group fed the first regime. There were no significant differ- ences between groups in survival rate (p>0.05).