Mirror Carp Research Articles

Induction of gynogenesis in red crucian carp using Spermatozoa of blunt snout bream

Abstract Gynogenetic diploid was induced in red crucian carp (RCC) (Carassius auratus Red Variety) eggs using UV-irradiated spermatozoa from blunt snout bream (B) (Megalabrama amblycephala) or from mirror carp (C) (Cyprinus carpio. L). Spermatozoa were genetically inactivated by an appropriate UV dosage, and then the maternal DNA was duplicated with cold shock at 0–4°C. When using the spermatozoa of B, the fertilization rate, hatching rate and survival at first feeding were 52.6 ± 3.0 %, 23.6 ± 4.1 % and 15.7 ± 3.4 % respectively, and the survival at first feeding was significantly higher than that (11.3 ± 2.2%) when using the spermatozoa of C(Cypripnus carpio. L). According to the morphological characteristics, the chromosome number and the degree of gonadal development, gynogenetic RCC could be distinguished from the control hybrids of RCC ♀ × B♂. The individuals with red body color, 100 chromosomes and normal gonadal development were syccessful gyogenetic RCC, while the individuals with 124 or 148 chro...

The estimate of natural piscicultural productivity depending of physical-chemical, biological parameter of water.

The research was made during biological year 2006 (March – November), when it was follows the evolution of some physical-chemical parameter and biological from water level, because by those evolution depends the obtaining some much more or small quantity of fish. In that sense, was taked in study 3 fish ponds where its practice systematic fisheries. The species who are growing are: carp (Cyprinio carpio), beside of other asian ciprinidae Hypophtalmycthis molitrix; Ctenopharingodon idella, and an small number by mirror carps, having like final target the calculation of natural piscicultural productivity and reale productivity obtained by ponds

Fatty Acid Composition in Intramuscular Lipids of Experimental Scaly Crossbreds in 3-Year-Old Common Carp (Cyprinus carpio L.)

The aim of the study was to determine the differences in the composition of fatty acids (in % of total fatty acids investigated), their total contents and ratios (n-6/n-3) in intramuscular lipids (IML) of three experimental scaly groups of carp (pure line PS: Přerov scaly carp, hybrid PS × M72: Přerov scaly carp × Northern mirror carp, hybrid PS × ROP: Přerov scaly carp × Ropsha scaly carp) in comparison with the mirror carp control group (hybrid M2 × M72: Hungarian mirror carp × Northern mirror carp). Compared with the controls (M2 × M72), fat content in meat of experimental groups of carp (PS, PS × M72, PS × ROP) was practically the same (p > 0.05). The highest fat content (89.8 ± 1.94 g kg-1) was found in meat of PS × ROP hybrids. Composition of fatty acids in IML was not influenced to any large degree by a hybrid type or by gender. The only exception was the IML of PS × ROP hybrids which, compared with controls (M2 × M72) and PS × M72 hybrids, contained significantly (p < 0.05) more polyunsaturated fatty acids (PUFAsum). Higher content of oleic acid (PS × ROP: 54.94 ± 0.70%) in carp fat was manifested by higher monounsaturated fatty acids (MUFAsum) values (PS × ROP: 64.20 ± 0.57%). IML of PS × ROP hybrids contained 6.99 ± 0.20% of linoleic acid and 0.53 ± 0.02% of arachidonic acid. Contents of α-linoleic acid (PS × ROP: 0.86 ± 0.09%), eicosapentaenoic acid (EPA) (PS × ROP: 0.69 ± 0.09%) and docosahexaenoic acid (DHA) (PS × ROP: 0.35 ± 0.02%) were low and influenced the PUFA n-6/n-3 ratio (PS × ROP: 3.25 ± 0.18). From this point of view, the IML of carp groups in this experiment constituted a relatively minor source of PUFAn-3 (PS × ROP: 2.39 ± 0.09%).

Comparison of yttrium and chromic oxides as inert dietary markers for the estimation of apparent digestibility coefficients in mirror carp Cyprinus carpio fed on diets containing soybean-, maize- and fish-derived proteins

The apparent digestibility coefficients (ADC) of protein, lipid and energy components within three selected plant protein by-products, i.e. solvent-extract soybean meal, full-fat soybean meal and maize gluten meal were evaluated for mirror carp (Cyprinus carpio L.). In a series of feeding and digestibility experiments, the ingredients were incorporated at the rate of 50% within a basal diet formulation, at the expense of a high quality fish-meal (LT94) source using both yttrium oxide, Y2O3 and chromic oxide, Cr2O3 as inert markers in test diets. The ADC of nutrients obtained from Cr2O3 closely matched those obtained from Y2O3. The ADC of protein were generally high, with >91% for both the fish-meal reference diet and solvent-extract soybean meal, 86% for full-fat soybean meal and 79% for maize gluten meal. The ADC by yttrium oxide gave values of 75–90% for protein. Similarly close values were obtained for both markers with respect to lipid ADC (77–91% with chromic oxide and 74–89% with yttrium oxide). It was concluded that the use of Y2O3 as an inert marker in digestibility studies with carp ought to be suitable for carp following further validation. This should be considered in view of predicting the digestibility of feeds for this fish species before inclusion in practical diets.

Evaluation of spermatological parameters of mirror carp (Cyprinus carpio) during spawning season.

Evaluation of spermatological parameters of mirror carp (Cyprinus carpio) during spawning season.

Induction of Gynogenesis in Japanese Crucian Carp ( Carassius cuvieri)

Diploid gynogenesis was induced in Japanese crucian carp ( Carassius cuvieri) eggs using UV-irradiated genetically inactive spermatozoa from mirror carp ( Cyprinus carpio L.) or blunt snout bream ( Megalobrama amblycephala), with or without cold shock. The optimal radiation dosage was 4200 mJ/cm 2 and 3600 mJ/cm 2 for mirror carp and blunt snout bream sperm, respectively. At this dosage and without cold shock, the yields were (32.4±3.3)% vs. (33.8±1.4)% gynogenetic haploids and (0.7±0.3)% vs. (0.5±0.3)% hybrid diploids, respectively. At the optimal UV dosage but with cold shock (2 min after fertilization, 0–4°C for 40 min), the hatching rates were (27.8±2.1)% and (29.4±3.3)%, respectively. From hatching to feeding, (15.7±3.4)% and (23.6±4.1)% normal gynogenetic diploids were recorded, respectively. Survival of normal gynogenetic diploids was 56% out of the hatched fry when using irradiated spermatozoa of mirror carp, which was lower than that (up to 80%) when using irradiated spermatozoa of blunt snout bream. This indicated that the sperm of blunt snout bream, with distant genetic relation to the maternal Japanese crucian carp, was more effective than that of mirror carp to induce diploid gynogenesis. The nature of the gynogenetic progeny was identified with external appearance, chromosome number and gonad structure. The presence of only females in gynogenetic progeny probably suggested XX genotype in the female Japanese crucian carp. The gynogenetic diploids have potential values such as faster growth and stronger disease resistance than the normal Japanese crucian carp. All gynogenetic progeny possessed 100 chromosomes whereas all J x B crosses were triploid with 124 chromosomes. The formation of the new triploid hybrids in J x B crosses may be useful in aquaculture.

Evaluation of growth and dressing out parameters of experimental scaly crossbreds in 3-year-old common carp (Cyprinus carpio, Linnaeus 1758)

Performance tests of the Prerov Scaly Carp (PS), two crossbreds (PS [multiplication] M72 and PS [multiplication] ROP) and an internal control group (M2 [multiplication] M72) were designed to assess their production and dressing out parameters at harvest size for their potential commercial utilization. The fastest growth rate (standard length (SL): 405±21.91 mm, P<0.01) and the highest final live weight (FLW: 2015.70±323.92 g, P<0.01) were recorded in the PS [multiplication] ROP hybrid. The SL values in this group of carp were 12.5%, 19.12% and 11.57% higher (P<0.01) than those at M2 [multiplication] M72, PS and PS [multiplication] M72, respectively, and the FLW values were 21.57%, 62.83% and 24.37% higher (P<0.01) compared with M2 [multiplication] M72, PS and PS [multiplication] M72 hybrids respectively. Growth rate parameters of PS [multiplication] M72 hybrid and control group M2 [multiplication] M72 were practically identical. The lowest growth rate potential and FLW were recorded in the PS group (P<0.01). The highest (P<0.01) dressing out parameters were found in the control group of mirror carp M2 [multiplication] M72 with a dressing percentage of 65.64±2.11%. There were practically no differences in this parameter between scaly carp groups (PS: 61.79±2.82%, PS [multiplication] M72: 61.51±1.72%, PS [multiplication] ROP: 63.60±1.96%). This study shows evidence for faster somatic growth and bigger final weight in the hybrid line PS [multiplication] ROP of 3-year-old common carp compared with the pure line PS and the crossbreed PS [multiplication] M72.

Raw and heat-treated culban ( Vicia peregrina ) seed as protein source for mirror carp ( Cyprinus carpio ) fingerlings

An 80-day feeding trial was conducted in a recirculation system aquarium operating at 26 ± 0.3 °C, to evaluate the nutritive value of Vicia peregrina seed as a possible protein source in the diet of mirror carp ( Cyprinus carpio ) fingerlings. Vicia peregrina seed was included in the diets at different levels, viz. 100, 200, 300 g heat-treated and 100, 200, 300 g raw seed in experimental diets designated A1, B1, C1, A2, B2 and C2, respectively. Growth parameters of the fish fed these diets were compared to fish receiving a fish meal and soyabean meal based control diet. On the basis of the specific growth rate (SGR), feed conversion ratio (FCR) and protein efficiency ratio (PER), the control and diets A1, B1, C1 and A2 were similar and significantly better than diets B2 and C2. Fish fed diets B2 and C2 showed a lower growth performance compared to those fed diets A1, B1, C1 and A2. Whole body fat content of the fish fed the diets containing the higher levels (>10%) of raw V. peregrina was significantly lower than in fish in the other treatments. Vicia peregrine seed has a potential as an alternative feed ingredient. It can be used without any adverse effects at up to 10% of the diet as a protein source in diets for fingerling mirror carp. However, the seed should be heat-treated if inclusion rates are to exceed 10% of the diet. Keywords : Culban, Vicia peregrina , nutritive value, heat treatment, mirror carp, growth South African Journal of Animal Science Vol. 36 (4) 2006: pp. 235-242

Population Genetic Variation and Structure Analysis on Five Popula-tions of Mirror Carp Cyprinus carpio L. Using Microsatellites

In this paper, population genetic variability and genetic structure of five populations of an important cultivation species, mirror carp (Cyprinus carpio L.) were analyzed using 30 microsatellite loci. The observed (Ho) and expected (He) heterozygosity values, polymorphic information content (PIC) and number of effective alleles (Ae) were all determined. The genetic similarity coefficient and Nei's standard genetic distance were computed based on the allele frequencies. The Hardy-Weinberg equilibrium was checked by chi2 test. Genetic differentiation and hierarchical partition of genetic diversity were evaluated by FST and Nm. A dendrogram was constructed based on UPGMA methods using PHYLIP software package supported by a bootstrap value of 91.0%. Totally 7,083 fragments were procured. Their lengths were from 102 bp to 446 bp. For each locus, 1-16 alleles were amplified, adding up to 356 alleles in all the 5 populations. We found the genetic variability level was relatively high in all five populations, as shown by Ae = 1.07-2.30, He= 0.70-0.78 and PIC=0.69-0.75, respectively. The genetic similarity coefficients were all above 0.52, indicating their close genetic relationships. The UPGMA phylogenetic tree showed mirror carps sampled from Donggang, Fengcheng and Liaozhong were clustered into one group and the other two populations, both collected from Songpu, were grouped together. There were obvious relations between genetic distances and geographical distributions of the five populations. No fragments were amplified from some loci of EST-SSRs, which may suggest the loss of these loci in mirror carp genome or sequence divergence at the primer binding sites. These null alleles may result from selection because functional genes are under more selection pressure than non-encoding loci. Overall, population genetic variation is high for each of the five mirror carp, and the differentiations are also significant among populations.

Evaluation of the Dressing Percentage of 3-year-old Experimental Scaly Crossbreds of the Common Carp (Cyprinus carpio, Linnaeus 1758) in Relation to Sex

The aim of the present study was to compare dressing percentages, with relation to sex, of three bisexual groups of hybrid carp, i.e. Hungarian mirror carp and Northern mirror carp (M2 × M72), the hybrid line of Přerov scaly carp and Northern mirror carp (PS × M72), the hybrid line of P.erov scaly carp and Ropsha scaly carp (PS × ROP), and the pure line of P.erov scaly carp (PS) in harvest size (K3). There were practically no differences in growth variables of male and female carp between the pure line PS carp and M2 × M72 and PS × ROP hybrids. Statistically significant differences in some variables between sexes were found in the scaly hybrid line PS × M72. Females in that group had significantly higher growth rates (TL and SL by 4.08% and 4.52%, respectively; p &lt; 0.05), and their weight variables were also higher (FW, CW and FilletWabs by 11.37%, 13.70% and 14.83%, respectively; p &lt; 0.05 and p &lt; 0.01). The weight of gonads of male carp from all the groups studied was significantly higher (p &lt; 0.01) than that of ovaries of female carp (or, rather, the GSI of male carp was higher).

Characterization of different strains of common carp (Cyprinus carpio L.) (Cyprinidae, Cypriniformes) in Bangladesh using microsatellite DNA markers

Characterization of different strains of common carp (Cyprinus carpio L.) using molecular markers is essential for the management of this fish in respect to the evaluation of the potential genetic effects induced by hatchery operations and the genetic improvement of carp varieties. Five microsatellite loci (MFW1, MFW2, MFW11, MFW15 and MFW20) were analyzed for the molecular characterization of four common carp strains, i.e. scaled carp, mirror carp, red carp and koi carp. We observed differences in heterozygosities and the average numbers of alleles but not in polymorphic loci (P95) among the strains. Koi carp displayed the highest level of variability in terms of heterozygosity. The Nm values and the FST values indicated a low level of gene flow and high level of differentiation among the strains. The highest genetic distance was observed between the scaled carp and the koi carp whilst the lowest genetic distance was found between the red- and koi carp. The unweighted pair group method with averages (UPGMA) dendrogram resulted in two clusters, one containing only the scaled carp and the other the remaining three varieties. Microsatellite markers have been found to be effective tools for characterization of different strains of common carp.

ERRATUM

Aquaculture ResearchVolume 36, Issue 16 p. 1628-1628 Free Access ERRATUM First published: 18 November 2005 https://doi.org/10.1111/j.1365-2109.2005.01373.xAboutSectionsPDF ToolsRequest permissionExport citationAdd to favoritesTrack citation ShareShare Give accessShare full text accessShare full-text accessPlease review our Terms and Conditions of Use and check box below to share full-text version of article.I have read and accept the Wiley Online Library Terms and Conditions of UseShareable LinkUse the link below to share a full-text version of this article with your friends and colleagues. Learn more.Copy URL Share a linkShare onFacebookTwitterLinked InRedditWechat In Kocour, Gela, Rodina and Linhart (2005), the following error was published on page 1211. The text was incorrect and should have read as follows: Results Growth performance and survival The effect of the tested group after second and third growing seasons and for the whole duration of the test on the live weight was shown as significant. Least-squares (LS) means given by ancova after the second growing season were significantly different between M72 (229.8±8.8 g) and M72 × PL (293.7±10.1 g) and M72 × Dor (288.3±14.2 g) (Table 2). Growth performance of M72 × M2 (265.6±10.0 g) hybrid was comparable with M72 breed as well as to both other crossbreds. The situation at the end of the test was similar to the previous year, but M72 × Dor hybrid (1619±28.3 g) showed significantly higher LS mean compared with M72 (1278±26.3 g) and M72 × M2 (1371±26.2 g). The same statistical results were obtained for total assessment, which also include the first growing season. In this case, WD between the pure breed M72 and crossbreds were 6.9%, 11.3% and 20.2% for M72 × M2, M72 × PL and M72 × Dor respectively (Table 2). Because ancova was used no effect of growing season on observed weight was shown. Season × group interactions were significant. Table 2. LS means±(standard errors, SE) of live weight and survival in tested mirror groups received by ancova after the second and third growing season and the total results including the data of the first year Group After second growing season After third growing season Total results (including first growing season) Live weight (g±SE) WD (%) Survival (%±SE) Live weight (g±SE) WD (%) Survival (%±SE) Live weight (g±SE) WD (%) Survival (%±SE) M72 229.8a±8.8 – 72.6a±4.6 1278a±26.3 – 95.0a±0.92 681.0a±23.1 – 58.9a±3.7 M72 × M2 265.6ab±10.0 15.6 68.8a±6.2 1371ab±26.2 7.3 90.8a±0.92 728.2ab±23.3 6.9 61.7a±2.8 M72 × PL 293.7±10.1 27.8 88.9a±5.8 1475bc±29.8 15.4 95.0a±0.92 757.7bc±18.8 11.3 61.9a±4.5 M72 × Dor 288.3b±14.2 25.5 92.0a±4.7 1619c±28.3 26.7 95.0a±0.92 818.3c±25.2 20.2 73.9b±3.2 Weight differences (WD) between the individual crossbreds and the pure breed M72 are expressed in percentage as well. (Groups with a common superscript do not differ significantly in the trait within the year, α<0.05.) In Kocour et al. (2005), the following error was published on page 1211 in Table 2. The table was incorrect and should have read as follows: We apologize for these errors. Reference Kocour M., Gela D., Rodina M. & Linhart O. (2005) Testing of performance in common carp Cyprinus carpio L. under pond husbandry conditions I: top-crossing with Northern mirror carp. Aquaculture Research 36, 1207– 1215. Wiley Online LibraryWeb of Science®Google Scholar Volume36, Issue16December 2005Pages 1628-1628 ReferencesRelatedInformation

Chemical and sensory quality changes of fish fingers, made from mirror carp (Cyprinus carpio L., 1758), during frozen storage (−18°C)

The effects of frozen storage at −18 °C on the chemical and sensory qualities of fish fingers produced from unwashed and washed mirror carp (Cyprinus carpio) mince were investigated. The amounts of moisture, crude protein, lipid, crude ash, ω3 polyunsaturated fatty acids (PUFA ω3), and ω6 polyunsaturated fatty acids (PUFA ω6) in fish fingers produced from unwashed mince (UWF) were found to be 68.50%, 15.5%, 6.00%, 2.20% 2.31%, and 55.2%, respectively, while they were found to be 70.23%, 10.8%, 2.14%, 1.80%, 2.28%, and 54.6%, respectively, in carp fingers produced from washed mince (WF). The thiobarbituric acid value (TBA, mg malonaldehyde/kg) was found to be significantly higher in mince of WF than in mince of UWF and increased significantly during frozen storage in both the mince of UWF and WF (p < 0.05). A significant decrease in pH was obtained throughout the washing treatment (p < 0.05). There were no significant differences of pH in either the mince of UWF or WF between the beginning and end of the storage periods (p > 0.05), whereas a sharp increase was observed in the fourth month in both groups. The protein solubilities of the mince of both UWF and WF decreased significantly throughout the storage periods (p < 0.05). Sensory parameters of colour, odour, flavour, and general acceptability for both groups decreased during the frozen storage period (p < 0.05) but were still within acceptable limits. It was also concluded that mirror carp was a good source for fish fingers and that product could be stored for five months in a frozen state without undesirable changes of sensory and chemical qualities.

Testing of performance in common carp Cyprinus carpio L. under pond husbandry conditions I: top-crossing with Northern mirror carp

Performance tests of Northern mirror carp (M72) and three different crossbreds were conducted in semi-intensive pond conditions from the larval stage up to market size. The aim of this study was to evaluate the possible utilization of new hybrid combinations (M72 × PL – Pohořelice mirror carp) and (M72 × Dor – Israeli mirror carp), and to compare them with a hybrid widely reared as a commercial product (M72 × M2 – Hungarian mirror carp) and with M72 purebred. The testing model was derived from similar studies carried out in the conditions of the Czech Republic, where an internal control of different scale cover is used to eliminate all non-genetic effects. ancova revealed at market size significantly better growth in M72 × Dor (1 619±28.3 g; LS mean±SE) and M72 × PL (1475±29.8 g) compared with M72 (1278±26.3 g). Survival during the test of 3 years duration was significantly the best in the M72 × Dor hybrid as were the dressing out parameters measured at market size, even if these were significantly different only in proportion of fillets with skin (39.1±0.28%). Interestingly, the crossbred M72 × M2 commonly used by Czech fishermen showed for both, growth (1371±26.2 g) and survival, the lowest values among crossbreds and with regard to dressing out parameters mostly among all tested groups.

Comparative study of the estrogenic responses of mirror carp ( Cyprinus carpio) exposed to treated municipal sewage effluent (Lisbon) during two periods in different seasons

To assess the estrogenic potency of the treated domestic sewage effluent from a sewage treatment plant (STP) located in Lisbon (Chelas), 60 mirror carp ( Cyprinus carpio) were exposed to different concentrations of the sewage effluent (0%, 25%, 50% and 100%) for two periods of 28 days in two different seasons (winter/spring). Vitellogenin induction in males was used as a biomarker of exposure to xenoestrogens. At the end of the experiment, blood samples were taken for vitellogenin analysis and the fish were sacrificed and dissected. Gonad samples were taken for histological evaluation of the sewage effects. The results showed an increase in vitellogenin induction in exposed fish, both males and females, depending on the different dilutions of the sewage effluent. In comparison with controls, the gonadosomatic index decreased significantly ( P<0.05) in fish exposed to 100% treated effluent. Although statistically not significant, the hepatosomatic index (HSI) was high in all exposed fish. Histological abnormalities in fish gonads were evaluated and related to the different percentages of sewage effluent. Seasonal variations found in estrogenic responses were attributed to weather influences on sewage dilution.

Potential problems with removing scales before surgical transmitter implantation

Thirty one mirror carp Cyprinus carpio were implanted with telemetry transmitters. Several large scales were removed from the incision area of two mirror carp before implantation of transmitters. When the fish were recaptured after 4 months, the mirror carp from which scales were removed showed severe tissue necrosis at the incision site whereas intact fish did not.

Genetic relationships among members of the Ichthyobodo necator complex: implications for the management of aquaculture stocks

Abstract Ichthyobodo necator (costia) is a common and important flagellate parasite that infests the skin and gills of many freshwater and marine fish. Costia infestations are often fatal and cause significant aquaculture losses worldwide. Recently it has been demonstrated that Ichthyobodo is a multispecies complex with differing host preferences. Knowing if those species have broad or narrow host specificity has important implications for the management of costia. To address the question of host specificity, genomic DNA was isolated from Ichthyobodo trophonts collected from rainbow trout, Oncorhynchus mykiss, koi, Cyprinus carpio, mirror carp, C. carpio, goldfish, Carassius auratus, channel catfish, Ictalurus punctatus, swordtail, Xiphophorus helleri, and Japanese flounder, Paralichthys olivaceus. The small subunit ribosomal RNA (SSU rRNA) gene from each isolate was analysed with previously published Ichthyobodo sequences using Bayesian phylogenetic methods. The internal transcribed spacers (ITS) from six isolates were also PCR-amplified, cloned and sequenced. Both the SSU rRNA phylogenetic analysis and the ITS rRNA sequence data support grouping the 22 Ichthyobodo isolates examined into a complex of nine different species. Many of these species were frequently isolated from multiple hosts, indicating that exchange of infested fish from one region to another has a high potential for spreading the disease. In one instance, the same species was obtained from marine and freshwater fish, further suggesting that certain Ichthyobodo species may not be limited by salinity.

Effect of short-term preservation of mirror carp (Cyprinus carpio) semen on motility, fertilization, and hatching rates

Mirror carp (Cyprinus carpio) semen was collected by hand stripping for short-term preservation. Two groups of pooled semen were diluted with one of two extenders; a control group was undi- luted. The three groups were stored at 4oC for 72 h. During preservation, spermatozoa motility (%) and duration of spermatozoa movement (s) were determined every 12 h. Following preser- vation, fertilization was carried out using the dry fertilization technique at 1 x 105 spermato- zoa/egg. The highest fertilization rates were 21±3.60% in May and 16.67±2.08% in June, both significantly higher than in the control. The highest hatching rates, 69.60±11.86% in May and 89.13±10.75% in June, did not significantly differ from the control.

Effects of Light on Trace Elements and Triiodothyronine Levels in Plasma of Mirror Carp (Cyprinus carpio)

The changes of copper, zinc, iron, magnesium, manganese, and triiodothyronine as a result of short- and long-term isothermal exposure to light were determined in the plasma of mirror carp (Cyprinus carpio). Two groups of fish were subject to a 3-mo treatment that consisted of (1) 8 h of light followed by 16 h of darkness and (2) 16 h of light followed by 8 h of darkness at 25 degrees C. No significant changes were recorded between the two groups at the beginning of the study. After 3 mo, the triiodothyronine and elements levels as well as the growth rates of fish in the long-time exposure period were significantly higher than those in the short-time exposure (p<0.05).

Effect Of Photoperiod On Plasma Thyroxine Hormone Level Of Mirror Carp (Cyprinus Carpio) Raised At A Low Water Temperature In A Controlled Environment

The objective of this study was to examine the effects of various lighting regimes on the plasma thyroxin hormone (T4) level of mirror carp (Cyprinus carpio). The carp were kept at the low tem- perature of 9°C to eliminate any influence of water temperature on feed intake, growth, and the hormone level. Treatments were 8 h light:16 h dark, 12 h light:12 h dark, and 16 h light:8 h dark. Plasma thyroxin levels were measured every four weeks for 12 weeks. The levels were signifi- cantly higher (p&lt;0.05) in the groups exposed to 8 or 12 h light than in the group exposed to 16 h. The T4 levels significantly dropped with time in all photoperiods.