Hatchery Trout Research Articles

Delineating the Growth Stanzas of Rainbow Trout, Oncorhynchus mykiss (Walbaum, 1792) Reared at a Major Himalayan Trout Hatchery

Delineating the Growth Stanzas of Rainbow Trout, Oncorhynchus mykiss (Walbaum, 1792) Reared at a Major Himalayan Trout Hatchery

Development of a recombinant adenovirus-vectored vaccine against both infectious hematopoietic necrosis virus and infectious pancreatic necrosis virus in rainbow trout (Oncorhynchus mykiss)

Infectious hematopoietic necrosis virus (IHNV) and infectious pancreatic necrosis virus (IPNV) are typical pathogens of rainbow trout Oncorhynchus mykiss, and the concurrent infection of the two viruses is very common among modern trout hatcheries, which has caused huge economic losses to the rainbow trout farming industry. To prevent and control the spread of IHNV and IPNV in juvenile trout simultaneously, in this study a bivalent recombinant adenovirus vaccine with IHNV Glycoprotein (G) and IPNV VP2 genes was developed. After immunizing juvenile trout with this bivalent vaccine via the immersion route, the expression levels of IHNV G and IPNV VP2 and the representative immune genes in vaccinated and control rainbow trout were tested to evaluate the correlation of immune responses with the expression of viral genes. The neutralizing antibody level induced by this bivalent vaccine as well as the protection efficacy of the vaccine against IHNV and IPNV was also evaluated. The results showed that IHNV G and IPNV VP2 were successfully expressed in juvenile trout, and all the innate and adaptive immune genes were up-regulated. This indicated that the level of the innate and adaptive immune responses were significantly increased, which might be induced by the high expression of the two viral proteins. Compared with the controls, high levels of neutralizing antibodies against IHNV and IPNV were induced in the vaccinated trout. Besides, the bivalent recombinant adenovirus vaccine showed high protection rate against IHNV, with the relative percent survival (RPS) of 81.25%, as well as against IPNV, with the RPS of 78.95%. Taken together, our findings clearly demonstrated that replication-defective adenovirus can be developed as a qualified vector for fish vaccines and IHNV G and IPNV VP2 were two suitable antigenic genes that could induce effective immune protection against these two pathogens. This study provided new insights into developing bivalent vectored vaccines and controlling the spread of IHNV and IPNV simultaneously in juvenile trout.

Branchitis and mortality in rainbow trout Oncorhynchus mykiss exposed to iron oxidizing bacteria: Diagnostics and management in a Colorado hatchery

AbstractA public trout hatchery in Colorado recorded repeat episodes of morbidity and mortality in early life stages of Rainbow Trout (Oncorhynchus mykiss) stocks. The water source for the affected tanks is a groundwater well with a pH of 6.3 and a ferrous iron concentration of 120 µg/L. Iron oxidizing bacteria (FeOB) were suspected as the underlying cause due to insoluble red particulate matter (iron oxide precipitate) in the water, and the presence of thick red slime (biofilm) that coated tanks and pipes of the facility and adhered to gills, opercula, and fins of fry. On necropsy, gill and fin clippings from moribund fish had mats of adherent red‐orange material. Histopathology revealed severe diffuse proliferative branchitis. There was abundant debris including granular to sheath‐like and stalk‐like pigmented material within the oral and branchial chambers, intimately associated with gill filaments. A Gram preparation demonstrated florid Gram‐negative bacteria within this debris. A Perls’ Prussian blue preparation revealed colocalization of abundant iron. Bacteria were identified morphologically to be of the iron oxidizing bacterial genera Gallionella and Leptothrix. This is the first known report of disease in fish associated with iron‐oxidizing bacteria.

American mink (Neovison vison) preying on hatchery and wild brown trout (Salmo trutta) juveniles in semi‐natural streams

AbstractPredator–prey interactions are one of the main ecological factors influencing the structure of fish communities. The impact of wading and diving semi‐aquatic predators on riverine fish populations is poorly known. We studied the effect of feral American mink predation on brown trout juveniles during winter in two experiments conducted in semi‐natural streams (length 26 m, width 1.5 m).In the first experiment, we compared the vulnerability of age‐1+ hatchery (length 142 ± 16 mm, average ±SD) and wild (112 ± 8 mm) brown trout of similar genetic origin in sympatry and allopatry. In the second experiment we used age‐0+ brown trout (79 ± 5 mm), increased habitat heterogeneity by addition of fine wood, and compared those to treatments without fine wood addition.Hatchery fish were more vulnerable to mink predation than their wild counterpart, and the predation rate increased with increasing body size among the hatchery trout. Predation by mink on wild trout was higher in sympatric than in allopatric treatments suggesting that stocking of hatchery fish may increase predation on wild conspecifics. Increased habitat heterogeneity resulted in reduced predation rate.The results show that a large size of hatchery fish in small streams was a negative trait, which was opposite to the mainstream observations of salmonid stockings made directly of feeding areas in lakes and oceans. Adding habitat heterogeneity was found important for habitat enhancements in streams with mammalian predators.We highlight the importance of taking all the habitats during the life cycle of migratory fish into account in management decisions and carefully considering whether using hatchery fish to support wild populations in streams.

Some Phenotypic Characteristics of Broodstock Populations Different in Rainbow Trout (Oncorhynchus mykiss) Hatcheries and Quality Criteria for Eggs Sampled from Different Broodstocks in the Same Environmental Conditions

Bu çalışmada Van ilindeki altı adet gökkuşağı alabalığı kuluçkahanesinde bulunan anaç populasyonlarının yumurta ve yumurtlamayla ilgili bazı fenotipik özellikleri ile örneklenen yumurtaların aynı çevresel şartlarda kuluçkalanmasıyla yumurta ve larva kalite kriterlerinin belirlenmesi amaçlanmıştır. Bu amaçla kuluçkahanelerde bazı su kalite kriterleri, anaçlarla ilgili kuluçkahane yönetim parametreleri, anaçların yumurta ve yumurtlama ile ilgili fenotipik özellikleri ve farklı kuluçkahanelerden örneklenen yumurtaların aynı çevresel şartlarda (10.1±0.14 °C) kuluçkalanarak yumurta ve larva kalite kriterleri belirlenmiştir. Su kalite kriterlerinin literatürde verilen aralıklarla uyumlu olduğu ve anaç refahını olumsuz etkileyecek düzeyde olmadığı görülmüştür. Kuluçkahanelerdeki toplam anaç sayısı, yaşı, boyu ağırlığı ile toplam ve nispi fekonditeleri her bir kuluçkahane için farklı olup bakım ve beslemelerinde de farklılıklar görülmüştür. Anaçların yumurtlama aralığı ve yumurtlama profili de her bir kuluçkahane için farklı olup kuluçkahanelerden birinde Kasım başında yumurtlayan anaçlar gözlenmiştir. Aynı çevresel şartlar altında yapılan deneme düzeneğinde ise yumurtaların gözlenme oranı ve larva çıkış oranı istatistiksel olarak farklı ve önemli bulunmuştur(P<0.05). Sonuç olarak tüm parametreler incelendiğinde kuluçkahaneler arasında fenotipik farklılıklar olduğu görülmüştür. Bu durumun nedeni kuluçkahanelerdeki su kalitesi ve anaç yönetim parametrelerinin farklı olması olabilir. Ancak bu farklılıkların nedeni kuluçkahanelerin bünyelerinde farklı anaç hatları bulundurmaları ve anaçlar arasında olan genotipik farklılıklar da olabilir. Bu nedenle genotipik farklılıklarla ile ilgili detaylı çalışmalara ihtiyaç vardır. Yetiştiricilik açısından ise kuluçkahanelerden sadece birisinde bulunan ve erken yumurtlayan anaçlardan, erken yumurtlayan hat elde etmek mümkündür. Daha ekonomik bir yetiştiricilik için anaçlarda yumurta sayısını ve kalitesini arttırmaya yönelik besleme yöntemleri uygulanmalıdır. Ayrıca anaç populasyonlarında homozigotluğu düşürmek için dişi erkek anaç oranı kuluçkahanelerde eşitlenmeli ve erkek anaç ihtiyacı porsiyonluk balıklardan karşılanmamalıdır.

Relative Cost and Post‐Release Performance of Hatchery Catchable Rainbow Trout Grown to Two Target Sizes

Catchable‐sized hatchery trout (hereafter, catchables) have become a staple component of many fisheries management programs throughout North America. Due to their size, catchables create immediate fisheries once they are stocked, and fisheries managers have gradually shifted towards stocking fewer, larger trout. However, the cost of growing larger fish may reduce the efficiencies of catchable stocking programs overall. We grew catchable‐sized Rainbow Trout Oncorhynchus mykiss to two target average sizes (254 and 305 mm total length) at a production scale, while tracking feed expenditures to examine the costs and benefits associated with increased size‐at‐stocking. Although larger catchables cost 31% more in feed expenditures than those reared to a smaller average size, catch (by anglers) of larger fish increased by 100% relative to smaller fish. Consequently, if target stocking size was changed from 254 to 305 mm and feed costs were held constant by reducing the total number of fish stocked, anglers would benefit by catching larger and more fish, despite the reduction in number of fish stocked. In lentic systems, larger catchables were reported by anglers more quickly than smaller fish, so managers must consider interactions between stocking size and residence time for lentic systems supported by catchables. In lotic systems, overall catch by anglers was much lower than catch at lentic waterbodies, and all catchables were either reported by anglers quickly or failed to be reported at all regardless of size‐at‐stocking. Producing larger catchables for hatchery‐supported fisheries serves to benefit angling and would likely increase angler satisfaction while improving efficiencies associated with hatchery catchable stocking programs.

Draft Genome Sequence of Janthinobacterium lividum ID1246, Isolated from a Rainbow Trout Hatchery Biofilm.

ABSTRACTWe present a draft genome sequence of Janthinobacterium lividum strain ID1246, isolated from within a rainbow trout hatchery raceway. Janthinobacterium spp. are well-known producers of antimicrobial compounds. Due to the unique isolation source, this genome may yield novel biosynthetic gene clusters.

Experimental Evidence of Epizootic Epitheliotropic Disease Virus (Salmoid Herpesvirus-3, Alloherpesviridae) Transmission via Contaminated Fomites and Subsequent Prevention Using a Disinfectant.

Epizootic epitheliotropic disease virus (EEDV) has caused considerable mortality in hatchery-reared lake trout Salvelinus namaycush in the Great Lakes Basin, and yet the routes of transmission and efficacious means of prevention remain poorly understood. To determine whether EEDV can be transmitted via contaminated fomites and clarify whether such transmission could be prevented via fomite disinfection, juvenile lake trout (n = 20 per treatment) were handled in nets previously soaked in an EEDV suspension (7.29 × 104–2.25 × 105 virus copies/mL of water) that were further immersed in either 1% Virkon® Aquatic (“disinfected” treatment, in triplicate) or in sample diluent (“EEDV-contaminated” treatment). Negative control nets were soaked in sterile sample diluent only. Characteristic gross signs of EED developed in the “EEDV-contaminated” treatment group, which was followed by 80% mortality, whereas no gross signs of disease and 0–5% mortality occurred in the negative control and “disinfected” treatment groups, respectively. EEDV was detected via qPCR in 90% of the “EEDV-contaminated” treatment fish, however, it was not detected in any fish within the negative control or “disinfected” treatment groups. Study findings not only demonstrate that EEDV can be readily transmitted via contaminated fomites, but importantly suggest that Virkon® Aquatic is an efficacious option for preventing EEDV contagion via the disinfection of hatchery tools, thereby highlighting a promising tool for improving lake trout hatchery biosecurity and minimizing EEDV-linked losses.

Length-weight relationship and relative condition factor of Polynemus paradiseus (Linnaeus, 1758) from Hooghly-Matlah estuary, West Bengal

The present study was conducted to isolate and characterise the genetic variations in Saprolegnia species and to study epidemiology of the fungal infection in rainbow trout hatcheries of Kashmir. A total of 145 infected fish samples were examined during October to March. The fungus infected trout showed signs of lethargy, irritation, loss of appetite, haemorrhages at the base of fins and deep wounds at the sites of severe infection associated with cottony wool like tufts on both dorsal and ventral side of body. Wet mount from infected lesions showed masses of mature and immature sporangia filled with spores of Saprolegnia. The colonies on fungal agar appeared with tufly of long hairs, whitish in colour that finally turned blackish after some days. The hyphae appeared profusely branched, aseptate and multinucleate. A total of 29 DNA samples were amplified by RAPD-PCR which revealed negligible genetic variations among the isolates indicating that a group of closely related strains of Saprolegnia having high degree of homology was present in the hatcheries of Kashmir. Key words Fungus, Fish, Cotton-wool disease, RAPD, Winter Introduction

Nuclear DNA reveals multiple waves of colonisation, reticulate evolution and a large impact of stocking on trout in north-west Africa

Using nuclear DNA sequences we studied the phylogeny and genetic structure of trout in Morocco, and estimated the impact of stocking upon natural populations. We supplemented the sample set from a previous study with new sample localities and with specimens from the main hatchery in Morocco. Phylogeny was performed using Bayesian inference, identification of genetic clusters and the genetic structure of populations were assessed from microsatellite polymorphism using discriminant analysis of principal components, and genealogical relationships among mitochondrial haplotypes were re-estimated with an unrooted phylogenetic network using statistical parsimony. Nuclear DNA sequences demonstrated the existence of three major clades in north-west Africa: (1) an Afro-Atlantic clade in Moroccan Mediterranean coastal rivers and the Sous drainage, stemming from a colonisation wave of the Atlantic lineage from Iberia, (2) a relict and native Draa clade (Dades trout), which has maintained an incipient nuclear DNA and mitochondrial DNA signature, and (3) a native Atlas clade, sister to Draa, in which only Atlantic mitochondrial DNA was found, suggesting invasion by Atlantic trout that introgressed into local populations and resulted in a reticulate evolutionary event. Microsatellite analysis and the distribution of the haplotypes revealed a large impact of hatchery trout stocking on wild populations.

Antifungal effect and comparison of saprolgenia sp. isolated resistance from Persion sturgeon (Acipencer persicus) and rainbow trout (Oncorhynchus mykiss) hatcheries against Huwa- San TR- 50 in invitro

Antifungal effect and comparison of saprolgenia sp. isolated resistance from Persion sturgeon (Acipencer persicus) and rainbow trout (Oncorhynchus mykiss) hatcheries against Huwa- San TR- 50 in invitro

Differential DNA methylation in somatic and sperm cells of hatchery vs wild (natural-origin) steelhead trout populations.

Environmental factors such as nutrition, stress, and toxicants can influence epigenetic programming and phenotypes of a wide variety of species from plants to humans. The current study was designed to investigate the impacts of hatchery spawning and rearing on steelhead trout (Oncorhynchus mykiss) vs the wild fish on a molecular level. Additionally, epigenetic differences between feeding practices that allow slow growth (2 years) and fast growth (1 year) hatchery trout were investigated. The sperm and red blood cells (RBC) from adult male slow growth/maturation hatchery steelhead, fast growth/maturation hatchery steelhead, and wild (natural-origin) steelhead were collected for DNA preparation to investigate potential alterations in differential DNA methylation regions (DMRs) and genetic mutations, involving copy number variations (CNVs). The sperm and RBC DNA both had a large number of DMRs when comparing the hatchery vs wild steelhead trout populations. The DMRs were cell type specific with negligible overlap. Slow growth/maturation compared to fast growth/maturation steelhead also had a larger number of DMRs in the RBC samples. A number of the DMRs had associated genes that were correlated to various biological processes and pathologies. Observations demonstrate a major epigenetic programming difference between the hatchery and wild natural-origin fish populations, but negligible genetic differences. Therefore, hatchery conditions and growth/maturation rate can alter the epigenetic developmental programming of the steelhead trout. Interestingly, epigenetic alterations in the sperm allow for potential epigenetic transgenerational inheritance of phenotypic variation to future generations. The impacts of hatchery exposures are not only important to consider on the fish exposed, but also on future generations and evolutionary trajectory of fish in the river populations.

Assessment and incidence of fish associated bacterial pathogens at hatcheries of Azad Kashmir, Pakistan.

Fish is the most indispensable source of proteins for individuals and have high nutritional value. On the other hand, the fish culturing raised issues of fish health due to close contact between the aquatic environment and the fish pathogens. So, the aim of the current study was to identify the bacterial pathogens and screen the injured Rainbow trout rearing in different trout hatcheries run under fisheries department of the government of Azad Jammu and Kashmir, Pakistan. Seven bacterial pathogens such as Shigella flexneri, Enterobacter amnigenus, Salmonella Typhimurium, Serratia odorifera, Pseudomonas aeruginosa, Streptococcus pyogenes, and Bacillus cereus were isolated and identified. Results revealed that the injury of fish specimens was due to overcrowding. Instead of rainbow coloration, specimens have darker black in color. The water of ponds was not clean and clear and such conditions was because of the greater quantity of feed thrown in the water. It was concluded that poor hygienic water condition and overloading allowed the opportunistic bacterial contaminations to succeed which cause a serious threat to hatcheries.

The Effect of Raceway Grading on Return to Creel for Catchable‐Sized Hatchery Rainbow Trout

AbstractHatchery trout of catchable size (i.e., about 250 mm total length; hereafter termed “catchables”), which are stocked into put‐and‐take fisheries, are expensive to raise, so fisheries management agencies strive to modify rearing practices to maximize the proportion of stocked catchables that anglers catch. We graded fish in production‐level hatchery rearing units at both fingerling and catchable size, dividing the fish into “leaders” (herein, the larger fish in a rearing unit, separated during a grading event) and “laggers” (the smaller fish). We hypothesized that (1) grading and immediate stocking of catchable leaders and short‐term retention and continued feeding of catchable laggers might increase lagger growth and result in a larger average size of fish being stocked (relative to fish from ungraded raceways), potentially improving overall return to creel for the graded group and (2) grading and separation of fingerling leaders and laggers early in the rearing process may reduce competition between smaller and larger fish for the remainder of the rearing period, potentially improving overall poststocking return to creel for the entire group without the need for catchable grading at the time of stocking. We found that grading catchables just prior to stocking slightly increased the mean size at stocking (compared with ungraded control fish) for the first stocking period, which resulted in slightly higher return to creel for stocked fish. However, across the entire stocking period and with equal feed between groups, mean size at release was nearly identical between the graded and the control fish, as was return to creel by anglers. Grading fingerlings to separate leaders and laggers for the remainder of the rearing period also had no positive effect on angler catch. Our findings suggest that production‐level grading is ineffective at increasing the growth of laggers, so it will not increase overall size at stocking. Consequently, improvements in angler catch are unlikely to materialize from grading hatchery trout prior to stocking them into put‐and‐take fisheries.

Microsatellites as a good approach for detecting triploidy in brown trout hatchery stocks

Mediterranean brown trout (Salmo trutta) populations have been extensively supplemented with genetically divergent hatchery stocks to enhance recreational fishing, and the displacements of native gene pools are well documented. Because of the great difficulty to breed local stocks of native Mediterranean brown trout in the farm, the introduction of Atlantic sterile individuals such as triploids has been proposed as an alternative to the traditional exogenous stocks. Several protocols of optimization and production of triploid fish have been described in S. trutta, nonetheless triploidy is not always induced in the totality of individuals. Therefore, a cost-effective and rapid method is necessary for triploidy verification. Several methods have been used to confirm triploidy, many of them costly in time and effort, and some providing approximate results. Here, we validated highly polymorphic DNA markers –microsatellites– as a rapid, useful and easy tool to detect triploidy. A total of 16 putative triploids, induced by a shock-heat treatment that suppressed the formation of the second polar body, were genotyped with nine microsatellites. All but two individuals showed a pattern of three peaks that corresponded to three alleles at least at one locus, and thus were confirmed as triploids. Genotypes of the two remaining individuals fit on a diploid genome. Our results provide useful insights into the development of alternative methods to assess triploidy in brown trout. Because a large number of microsatellites have been described for many species the use of these highly polymorphic markers to detect triploidy is a valuable tool to be applied in hatcheries.

Long‐ term effects of water quality on the freshwater bivalve Diplodon chilensis (Unionida: Hyriidae) caged at different sites in a North Patagonian river (Argentina)

AbstractWater quality was monitored along an Andean river of global importance using the freshwater bivalve Diplodon chilensis as sentinel species. Bivalves were placed in cages at three sites (S1–3) in the Chimehuin River in order to evaluate the long‐term effects of a trout hatchery (S2) and the open dump and sewage treatment plant of a nearby city (S3). Water samples and bivalves were collected at 0, 3, 6, 9 and 12 months, from S3, S2 and from a reference site upstream (S1), and physicochemical parameters and the biological response of the caged bivalves were studied. ROS production, antioxidant response, oxidative damage, energy status and morphometric ratios were included as response biomarkers. Most of biomarkers showed site and time dependence including bivalves transplanted at S1, revealing natural variability. Both anthropogenic perturbed sites (S2 and S3) showed differences in the exposed bivalves with respect to the reference site (S1) in their biomarker responses after 9 and 12 months of exposure (July and September, respectively). Multivariate analysis showed alterations in hemocytes (ROS, TOSC and NRRT50), in energy balance in digestive gland (energy and DGF) and in the detoxification response (GST) and GSH values in gill when bivalves were exposed to hatchery waste; whereas metal and bacterial pollution (S3 in July) caused GSH increase and a reduction of lysosomal damage in hemocytes. Results show that changes in the water quality of Chimehuin River due to the anthropogenic impact can be detected using the biomarkers analysed on D. chilensis, being a useful tool for studies of long‐term monitories.

ОСОБЕННОСТИ ФОРМИРОВАНИЯ МАТОЧНОГО СТАДА РАДУЖНОЙ ФОРЕЛИ В НАУЧНО-ПРОИЗВОДСТВЕННОМ ЦЕНТРЕ «ФОРЕЛЬ» (ОКОНСК, УКРАИНА)

The article presents the analysis of the data on developing brood stock and repair-brood stock of rainbow trout, as well as the data on individual reproductive indicators of females carried out in the Research and Production Center “Forel” (Okonsk Vlg., Ukraine). The stages of development of trout farming in the territories of the former USSR, Ukraine (the Carpathians, Ternopil and Volyn regions), and the Baltic states are considered. Currently, rainbow trout hatcheries need modern methods to increase the efficiency of artificial reproduction by reducing the loss of living material (especially at the early stages of ontogenesis), and increasing the vitality of juveniles. For the study, 20 trout females were selected from those participated in the spawning campaign in 2014, of which 18 females were from the main broodstock and 2 females were spawning for the first time in the repair broodstock. The females were divided into 3 groups depending on weight. In the course of the study there was stated the direct dependence of the main reproductive indicators on weight: the minimum amount of eggs was obtained from individuals with a minimum weight, and the maximum number of eggs was obtained from heavy individuals. It has been found that the greater the weight of individuals, the higher the percentage of egg fertilization. Females from the repair brood stock that spawned for the first time had low breeding and biological indicators.

Colonial Waterbird Predation and Angler Catch of Hatchery Rainbow Trout Stocked in Southern Idaho Fisheries

AbstractThe abundance of piscivorous colonial waterbirds such as double‐crested cormorants Phalacrocorax auritus and American white pelicans Pelecanus erythrorhynchos has increased dramatically in recent decades in North America, resulting in increased conflict between these birds and fisheries resources, which raises the need to quantify the effects of waterbird predation on fisheries. We estimated avian predation and angler use of two sizes of hatchery‐reared Rainbow Trout Oncorhynchus mykiss (250 mm and 300 mm on average; termed standard catchables and magnum catchables) at 15 Idaho waters with known cormorant and pelican presence. Fish were tagged with passive integrated transponder (PIT), radio, and T‐bar anchor tags prior to release; the tags were subsequently recovered from bird nesting, roosting, and loafing sites. Estimated angler use, which included fish harvested as well as those that were catch‐and‐release, averaged 17%, while avian predation averaged 35%. Angler catch at study waters declined exponentially as avian predation increased. Predation specifically attributed to double‐crested cormorants and American white pelicans was related to their relative abundance at the waterbodies where the fish were stocked. Avian predation rates were similar for standard and magnum catchables, suggesting that larger fish were not able to escape predation any better than smaller ones. Our results add to existing evidence indicating that in some southern Idaho fisheries, piscivorous birds, rather than anglers, are the dominant consumers of hatchery trout. This study further contributes to the larger issue of competition between humans, wildlife, and fisheries populations.

Janthinobacterium lividum as An Emerging Pathogenic Bacterium Affecting Rainbow Trout (Oncorhynchus mykiss) Fisheries in Korea

Janthinobacterium spp. are normally considered non-pathogenic, and few pathogenesis-related studies have been reported. Here, we report the first isolation of Janthinobacterium lividum in Korea as a pathogenic bacterium infecting rainbow trout. Mass mortality was observed at one rainbow trout hatchery, and dead fish were necropsied. Gram-negative, nonmotile, rod-shaped bacteria that grew on Cytophaga agar were isolated. A specific violet pigmentation was observed after 7 days of cultivation, and the species were characterized on the basis of the analysis of the 16S rRNA gene. Because no research has focused so far on the pathogenicity of these bacteria, our study was directed to their pathogenic role based on infection-induced histopathology. Examination of stained tissue sections revealed severe renal bacteraemia and tubule degeneration. Other tissue sections, including sections from the liver and the spleen, were relatively clear. The measured half-maximal lethal dose (LD50) was approximately 3 × 105 colony-forming units/fish, suggesting that this bacterium may be an opportunistic pathogen in rainbow trout fisheries. Since the bacterium commonly dwells in soil and most water for rainbow trout fisheries in Korea is supplied from ground water, the bacteria may naturally flow into the aquatic environment. Therefore, recognition of any pathogenic role of J. lividum is important for the prevention of disease in aquaculture.

Kahramanmaraş İlindeki (Türkiye) Farklı Kapasitelere Sahip Gökkuşağı Alabalığı (Oncorhynchus mykiss) Kuluçkahanelerinin Karşılaştırmalı Yapısal ve Ekonomik Analizi

In this study, the structural and economic aspects of rainbow trout (Oncorhynchus mykiss) hatcheries with the different production capacities in Kahramanmaraş Province of Turkey were compared. The commercial structure of this enterprises was 60% person-family and 40% company-partnership. Statistically, the medium-sized (96.88%) hatcheries have higher capacity usage rate than the the small (69.98%) and large-sized (60.0%) hatcheries (P˂0.01). However, the production efficiency of the small (64.50%) and medium-sized (63.99%) enterprises were higher (P˂0.01) than the large-sized enterprises. Average active capital was US $181 165 in the small-sized, $436 147 in the medium-sized and $1 271 634 in the large-sized enterprises. Gross and net income values were $40 213 and $4 215 in the small-sized enterprises, $189 412 and $74 268 in the medium-sized enterprises and $901 961 and $69 074 in the large-sized enterprises. The medium-sized enterprises have highest economic rantability (17.03%) followed by the large (5.43%) and small-sized (2.33%) enterprises (P˂0.01). Differences in the structural characteristics of existing enterprises directly affect their capacity usage rate and production efficiency.