Caspian Brown Trout Research Articles

Phylogeography, genetic structure, and conservation of the endangered Caspian brown trout, Salmo trutta caspius (Kessler, 1877), from Iran

The Caspian Sea, the largest inland closed water body in the world, has numerous endemic species. The Caspian brown trout (Salmo trutta caspius) is considered as endangered according to IUCN criteria. Information on phylogeography and genetic structure is crucial for appropriate management of genetic resources. In spite of the huge number of studies carried out in the Salmo trutta species complex across its distribution range, very few data are available on these issues for S. trutta within the Caspian Sea. Mitochondrial (mtDNA control region) and nuclear (major ribosomal DNA internal transcribed spacer 1, ITS-1, and ten microsatellite loci) molecular markers were used to study the phylogeography, genetic structure, and current captive breeding strategies for reinforcement of Caspian trout in North Iranian rivers. Our results confirmed the presence of Salmo trutta caspius in this region. Phylogenetic analysis demonstrated its membership to the brown trout Danubian (DA) lineage. Genetic diversity of Caspian brown trout in Iranian Rivers is comparable to the levels usually observed in sustainable anadromous European brown trout populations. Microsatellite data suggested two main clusters connected by gene flow among river basins likely by anadromous fish. No genetic differences were detected between the hatchery sample and the remaining wild populations. While the current hatchery program has not produced detectable genetic changes in the wild populations, conservation strategies prioritizing habitat improvement and recovering natural spawning areas for enhancing wild populations are emphasized.

Broken Eggs Influence on Fertilization Capacity and Viability of Eggs, Turbidity and pH of Ovarian Fluid and Fertilization Water in the Endangered Caspian Brown Trout, Salmo Trutta Caspius

To identify a simple tool for quick evaluation of quality of endangered Caspian brown trout, Salmo trutta caspiuseggs, the changes of pH (both in ovarian fluid and fertilization water), turbidity (both in ovarian fluid andfertilization water), fertilization and eyeing rates were investigated in ovarian fluid samples containing perfecteggs as well as different concentrations of broken eggs. The pH of ovarian fluid and water as well as fertilizationand eyeing rates decreased significantly (P<0.05) with increasing of broken eggs in ovarian fluid. In contrast, theturbidity of ovarian fluid and water as well as mortality rate of eggs increased significantly (P<0.05) withincreasing of broken eggs in ovarian fluid. Also, significant correlations (P<0.01) were found between measuredparameters as follow: pH of ovarian fluid vs. pH of water and fertilization and eyeing rates; turbidity of ovarianfluid vs. turbidity of water; turbidity of ovarian fluid and water vs. fertilization and eyeing rates. Our resultsconclude that pH and turbidity of ovarian fluid and water effectively influence on efficiency of artificialpropagation. Therefore, these could be used as two simple tools for quick evaluation of quality of Caspian browntrout eggs during artificial reproduction in the hatchery.

Assessment of ability of endangered Caspian brown trout, Salmo trutta caspius (Salmonidae) in production of semen with desirable quality

To assay the effects of stripping frequency on semen characteristics of Caspian brown trout, Salmo trutta caspius, the chemical composition of seminal fluid, sperm production (semen volume, sperm density, spermatocrit,) and sperm motility characteristics (percentage and duration of motility) were investigated over four times stripping during the spawning season. According to data, semen volume, sperm density, osmolality and the concentrations of Na+, Cl−, K+, Ca2+, Mg2+ and total protein gradually decreased by increasing of stripping frequency. The values of glucose and triglyceride had no significant changes over four times stripping. Also, the values of semen pH, the percentage (5 s after activation) and duration of motility were statistically stable until third stripping but a decrease was recorded for these parameters in the fourth stripping. As well as, significant positive correlations were found for sperm density vs. K+, Cl−, Na+, Ca2+, Mg2+, total protein, spermatocrit; the percentage of motile spermatozoa vs. Ca2+, Mg2+, K+, Cl−, Na+, total protein, and also the duration of motility vs. K+, Cl−, total protein and pH. In text, specific objectives of this study have been expressed.

Effects of total fish oil replacement to vegetable oils at two dietary lipid levels on the growth, body composition, haemato-immunological and serum biochemical parameters in caspian brown trout (Salmo trutta caspius Kessler, 1877)

This research aimed to evaluate the effects of two dietary fat levels [low fat (LF) (10%), high fat (HF) (20%)] and sources [fish oil (FO), vegetable oil (VO)] on the growth and some physiological parameters of Caspian brown trout fingerlings for 60 days. Tuna oil or blends of canola and soybean oils (85:15) were added to diets to design four feeds namely LFFO, HFFO, LFVO and HFVO according to the fat levels and sources. The fish fed the LFFO diet had lower weight gain than the other fish (P<0.05). The total n-6 fatty acids increased in fish fed diets with the blends of VO, while the total n-3 fatty acids decreased in these fish (P<0.05). Serum lysozyme activity was higher in fish fed the HFVO diet than the other fish (P<0.05). Serum glucose, total cholesterol, triglyceride and very low-density lipoprotein were lower in fish fed LFFO than the other fish (P<0.05). The present study demonstrates that in terms of fish growth, VOs can be used as an alternate source of dietary fat, whereas fish health and nutritional value are improved with the LFFO diet. According to these results, a partial substitution of FO by VO in high-level fat diets is suggested for long-term feeding of Caspian brown trout.

Evaluation of semen quality of endangered Caspian brown trout (Salmo trutta caspius) in different times of spermiation during the spawning season

Sperm motility and sperm production as well as organic and inorganic components present in the seminal plasma were measured at different time periods of spermiation during the spawning season in order to evaluate the semen quality in Caspian brown trout, Salmo trutta caspius. For such evaluation, males were divided into four groups based on the date of spermiation: group A (pre-mature broodstocks), group B and C (mid-mature broodstocks), group D (late-mature broodstocks). Our results showed that the Caspian brown trout produces semen of variable quality depending on the date in the period of spermiation. In this regard, the percentage of motile spermatozoa, duration of motility, sperm density, osmolality and also the concentrations of Na&lt;sup&gt;+,&lt;/sup&gt; Cl&lt;sup&gt;&amp;ndash;&lt;/sup&gt;, K&lt;sup&gt;+&lt;/sup&gt;, Ca&lt;sup&gt;2+&lt;/sup&gt;, Mg&lt;sup&gt;2+&lt;/sup&gt; and total protein content were significantly higher in mid-mature broodstocks (which matured in the middle of spawning season, i.e. groups B and C) compared to pre-mature (group A) and late-mature (group D) samples. Statistically significant positive correlations were also found between these semen parameters: sperm production vs Na&lt;sup&gt;+&lt;/sup&gt;, Cl&lt;sup&gt;&amp;ndash;&lt;/sup&gt;, K&lt;sup&gt;+&lt;/sup&gt;, Ca&lt;sup&gt;2+&lt;/sup&gt;, Mg&lt;sup&gt;2+&lt;/sup&gt;, total protein, osmolality, pH; percentage of motile spermatozoa vs Na&lt;sup&gt;+&lt;/sup&gt;, Cl&lt;sup&gt;&amp;ndash;&lt;/sup&gt;, K&lt;sup&gt;+&lt;/sup&gt;, Ca&lt;sup&gt;2+&lt;/sup&gt;, Mg&lt;sup&gt;2+&lt;/sup&gt;, total protein, osmolality; duration of motility vs Na&lt;sup&gt;+&lt;/sup&gt;, Cl&lt;sup&gt;&amp;ndash;&lt;/sup&gt;, K&lt;sup&gt;+&lt;/sup&gt;, Ca&lt;sup&gt;2+&lt;/sup&gt;, Mg&lt;sup&gt;2+&lt;/sup&gt;, total protein, pH. The significance of such correlations is interpreted in terms of physiological implications and is discussed in relation to semen quality.

Growth response, body composition and fatty acid profile of Caspian brown trout (Salmo trutta Caspius) juvenile fed diets containing different levels of soybean phosphatidylcholine

We investigated the effects of soybean phosphatidylcholine (PtCho) on the growth, fatty acid (FA) profile, and body composition of juvenile Caspian brown trout. Juvenile trout, initial average weight 0.8 ± 0.12 g, were fed semi-purified formulated diets supplemented with 2, 4, and 6% PtCho for 5 weeks. Results showed that fish with diets containing 4 or 6% PtCho had significantly greater growth. The FA profiles of both the polar lipids (PL) and neutral lipids (NL) in juvenile tissues were influenced by dietary FA, although the effects of PtCho supplementation were more marked for PL than for NL. Fish fed PtCho in the diet also had higher levels of 18:2n-6, 20:4n-6 and n-6, and significantly lower levels of docosahexaenoic acid and eicosapentaenoic acid in both PL and NL. The lipid contents of whole-body tissues and liver were positively affected by PtCho percentage in the diet. Specific growth rate, hepatosomatic index, visceralsomatic index, and protein efficiency ratio were also significantly influenced by dietary PtCho. The results of our study indicate that dietary PtCho has a growth-promoting effect and that juvenile Caspian brown trout have a relatively moderate PtCho requirement (at least 4% dry weight of the diet).

Changes in Sperm Production, Sperm Motility, and Composition of Seminal Fluid in Caspian Brown Trout, Salmo trutta caspius, Over the Course of a Spawning Season

This study was carried out to evaluate milt quality in male Caspian brown trout (Salmo trutta caspius) over the course of the winter spawning season. Milt samples were collected biweekly during December and January. Chemical composition of seminal fluid, sperm production (milt volume, sperm density, spermatocrit,) and sperm motility characteristics (percentage and duration of motility) were measured. Milt volume, sperm density, osmolality, seminal minerals (Ca2+, Mg2+, K+, Na+, Cl−), and total protein gradually decreased over the spawning season. Glucose and triglyceride content of milt did not show significant changes over the spawning season. Milt pH and the percentage and duration of motility were comparatively stable, declining only at the end of the season. Significant positive correlations were found between sperm density and seminal minerals, total protein and spermatocrit; percentage of motile spermatozoa and seminal minerals, total protein; and duration of motility and K+, Cl−, total protein, and pH. Results show that season has a significant influence on milt quality in male Caspian brown trout, with the best milt being available at the beginning of spawning season.

Biochemical and histological studies of over-ripened oocyte in the Caspian brown trout (Salmo trutta caspius ) to determine biomarkers for egg quality

The aims of the present study were to determine the best time for egg stripping after ovulation and to study oocyte over-ripening in the Caspian brown trout (Salmo trutta caspius ). Eggs were retained in the female abdominal cavity for 40 days post ovulation (DPO). Partial volumes of eggs stripped from 10 individually identified females at 10 days intervals and fertilized with a pool of semen obtained from 8 males. The biochemistry and histology of the eggs and the biochemistry of the ovarian fluid were studied. The eyeing and hatching rate of the eggs declined with over-ripening time, which decreased from 90.60±6.28% for eyeing and 86.33±6.82% for hatching in newly ovulated eggs (0–10 DPO) to 1.34±0.67% for eyeing and 0.98±0.49% for hatching in over-ripened eggs (30–40 DPO). However, larval abnormalities remained constant for 30 days after ovulation. During the course of oocyte over-ripening, the pH of the ovarian fluid significantly decreased and the concentration of glucose, protein, calcium, iron, and aspartate aminotransferase activity significantly increased. Moreover, the concentration of protein, triglycerides, and aspartate aminotransferase activity in the eggs changed with over-ripening. In the newly ovulated eggs, the yolk consisted of homogenous tissue and its perivitelline space diameter had no considerable differences. With over-ripening, the yolk became heterogeneous, and while chorion diameter did not change, the perivitelline space diameter varied among different areas. The present study demonstrated that the best time to take Caspian brown trout eggs after ovulation at 7±0.6°C was up to 10 DPO. Among the studied parameters of the egg and ovarian fluid, egg quality was related to both ovarian fluid parameters (pH, protein, aspartate aminotransferase, glucose, cholesterol, triglycerides, calcium) and egg parameters (iron, aspartate aminotransferase), suggesting that these parameters can be used as egg quality biomarkers for Caspian brown trout.

The Relation Between Egg Viability, Selected Aspects of Egg and Ovarian Fluid Composition and Time of Stripping in Endangered Caspian Brown Trout (Salmo trutta caspius)

The Relation Between Egg Viability, Selected Aspects of Egg and Ovarian Fluid Composition and Time of Stripping in Endangered Caspian Brown Trout (Salmo trutta caspius)

Assessment of digestive enzymes activity during the fry development of the endangered Caspian brown trout Salmo caspius

The study of digestive enzymes activity at Salmo caspius fry showed that enzymes were available at the moment of mouth opening on the first day post hatching (dph) and the activity of enzymes showed no significant difference from the hatching day 28 dph. An increased activity was seen between 32 and 43 dph and this activity was significantly higher than the activity during the first 28 days. In the primary stages after yolk sac resorption (43-58 dph), enzymes activity showed an increased profile, however none of them showed a significant difference between 43 and 58 dph.

LHRHa-induced ovulation of the endangered-Caspian brown trout (Salmo trutta caspius) and its effect on egg quality and two sex steroids: testosterone and 17α-hydroxyprogestrone

To induce synchronized ovulation, migrating wild Caspian brown trout (Salmo trutta caspius) females were treated with two interperitoneal injections of Des-Gly10, d-Ala6 LHRH (LHRHa), given 3 days apart. Two injections of 100 μg kg−1 body weight of this hormone effectively induced ovulation. Within 27 days from the second injection, all fish injected with 100 μg kg−1 LHRHa had ovulated compared with 54.5% of the controls. The mean time to ovulation was reduced significantly (P<0.05) from 31.67±4.84 days in control fish and 28.83±7.31 days in sham-treated fish to 16.36±1.61 days in fish injected with 100 μg kg−1 LHRHa. The fertilization rate in 50 and 100 μg kg−1 LHRHa-injected fish was significantly lower than that in the control fish (P<0.05). In fish injected with 50 and 100 μg kg−1 LHRHa, significant (P<0.05) changes in testosterone (T) and 17α-hydroxyprogestrone (OHP) levels were observed. After the second LHRHa injection, the fish injected with 100 μg kg−1 showed the highest serum levels of testosterone and OHP. These results demonstrate that the use of LHRHa can effectively reduce the mean time to ovulation and induce synchronized ovulation in Caspian brown trout.

Effects of Different Protein and Energy Levels on Growth Performance of Caspian Brown Trout, Salmo trutta caspius (Kessler, 1877)

Effects of Different Protein and Energy Levels on Growth Performance of Caspian Brown Trout, Salmo trutta caspius (Kessler, 1877)

Effects of Stripping Frequency on Semen Quality of Endangered Caspian Brown Trout, Salmo trutta caspius

Problem statement: Because of dramatic declines in stocks of endangere d Caspian brown trout males, Salmo trutta caspius in Caspian Sea, each male brooder is stripped indi spensably more than once during the spawning season in other to ar tificial insemination in hatchery. The aim of the present study was to assay the changes of indicator s of semen quality (sperm motility, sperm production, semen volume and chemical composition of seminal fluid) during these sequential strippings. Approach: The 11 tagged males were stripped four times every 12-14 days with beginning of spermiation period (2 December 2008) towards its end (10 January 2008). One-way Analysis Of Variance (ANOVA) was employed to analyze differences between means of semen parameters. Also, the relationships between semen p arameters were tested using the bivariate correlation coefficients of Pearson. Results: The semen volume, sperm density, osmolality and the concentrations of Na + , Cl - , K + , Ca 2+ , Mg

Composition of ovarian fluid in endangered Caspian brown trout, Salmo trutta caspius, and its effects on spermatozoa motility and fertilizing ability compared to freshwater and a saline medium

In this study, ovarian fluid composition and its effects on the motility and fertilizing ability of sperm were studied in endangered Caspian brown trout, Salmo trutta caspius, and were compared with a saline activation medium (125 mM NaCl, 30 mM Glycine, 20 mM Tris-HCl, pH = 9.0) and freshwater as the control. The ovarian fluid was composed of sodium 164.4 +/- 4.4 mM l(-1), potassium 1.8 +/- 0.1 mM l(-1), calcium 0.6 +/- 0.1 mM l(-1), magnesium 0.4 +/- 0.02 mM l(-1), chloride 127.4 +/- 5.9 mM l(-1), total protein 389.5 +/- 89.6 mg 100 ml(-1), cholesterol 9.3 +/- 1.2 mg dl(-1), and glucose 3.3 +/- 0.2 mM l(-1). The percentage of motile spermatozoa and the duration of sperm motility were significantly higher in ovarian fluid (62 +/- 3%, 74.6 +/- 0.8 s) than freshwater (35 +/- 4%, 44 +/- 1 s), but they did not differ significantly from saline medium (56 +/- 3%, 74.3 +/- 0.7 s) (P > 0.05). Higher eyeing rates were observed after the activation of sperm in ovarian fluid and saline solution than freshwater when 35,000 or 350,000 spermatozoa per egg were added into the activation media. However, no significant differences were observed at higher concentrations of spermatozoa per egg (730,000) (P > 0.05). Also, this study showed that the ovarian fluid composition can be considered as a species-specific character among salmonid fishes. As a conclusion, the results of this study recommend the use of ovarian fluid or the saline solution as an activation medium in the artificial reproduction of Caspian brown trout.

On the status of the critically endangered Caspian Brown Trout, Salmo trutta caspius, during recent decades in the southern Caspian Sea basin (Osteichthyes: Salmonidae)

The changes in some of the biological traits of mature females of the critically endangered Caspian Brown Trout, Salmo trutta caspius Dorofeeva, 1967, during recent decades were analysed. The results demonstrated that the mean length has significantly (p<0.05) declined over the past 60 years, from 77.6 cm in 1947 to 59.8 cm in 2007 (22.4%). The same trend was observed for mean total weight which significantly (p<0.05) reduced from 4880.2 g in 1947 to 2486.8 g in 2007 (49.5%). Also, the level of absolute fecundity sharply decreased from 7041.8 in 1947 to 4526.1 in 1973 and to 2941.2 in 1986. Whereas there was no significant (p>0.05) difference between the relative fecundity in 1947 (1451.4 per kg of body weight) and 1973 (1372.6 per kg of body weight), a significant (p<0.05) reduction has been observed since 1986 (1199.8 per kg of body weight). The possible reasons for these biological changes are discussed. Based on this study, the exploitation and sale must be controlled, and efforts should be concentrated on rehabilitation of the natural spawning habitats as soon as possible.

Sperm density, seminal plasma composition and their physiological relationship in the endangered Caspian brown trout (Salmo trutta caspius)

Sperm density, mineral and organic composition of the seminal plasma and their physiological relationship were investigated in the Caspian brown trout (Salmo trutta caspius). To establish a rapid and accurate method for assessment of sperm density, three different techniques were used: sperm counting, spectrophotometry (at 480 nm) and determination of the spermatocrit. The seminal plasma contained 159.26±8.84 mM sodium (Na), 33.72±2.01 mM potassium (K), 133.04±5.96 mM chlorine (Cl), 1.68±0.2 mM calcium (Ca) and 0.988±0.13 mM magnesium (Mg). The following organic components were found: total protein 0.75±0.14 mg 100 mL−1, cholesterol 2.86±0.58 mg L−1 and glucose 3.81±1.04 mM L−1. The mean sperm density was estimated to be 3.3 × 109 spermatozoa mL−1. The spermatocrit (%) ranged from 25 to 52 in sperm samples. Highly significant linear relationships were found between sperm density and spermatocrit (R2=0.703, P<0.001) and sperm density and optical density (R2=0.909, P<0.001), indicating that optical density can be used as a quick and accurate method of estimating sperm density. Significant relationships were also found between sperm density and Ca, Mg and total protein of seminal plasma. A significant correlation was also observed between the Ca and Mg concentrations (R2=0.774, P<0.01). The following correlations were observed between mineral and organic components: total protein and Ca (R2=0.462, P<0.05), total protein and Mg (R2=0.518, P<0.05) and glucose and Cl (R2=0.374, P<0.05). These parameters should be considered when developing procedures for either artificial fertilization or for cryopreservation of sperm.

In vitro storage of unfertilized ova of endangered Caspian brown trout ( Salmo trutta caspius) in artificial media

In order to study the effects of storage media and time of storage on the viability of unfertilized eggs of endangered Caspian brown trout ( Salmo trutta caspius), the ova of this fish was stored in coelomic fluid and Cortland artificial media at 2–3 °C for 120 h. In this research, Cortland artificial medium was buffered with 20 mM of three different buffers: Hepes (C 8H 18N 2O 4S), Tris–HCl (C 4H 11NO 3–HCl) and sodium salt Hepes (C 8H 17N 2O 4SNa). The pH of these media were adjusted according to natural pH of coelomic fluid. The eggs that stored in these media fertilized at times 0 h (eggs fertilized prior to storage), 48, 72 and 120 h of post-stripping, using fresh and pooled sperm obtained from four to six males. According to the results of present study, time of storage showed a significant ( p < 0.05) main effect on eyeing, hatching and eyed eggs mortality rates. Eyeing and hatching rates significantly ( p < 0.05) decreased from 97.4 ± 2.1% and 95.1 ± 4.4% at time 0 (eggs fertilized prior to storage) to 77.9 ± 3% and 65.5 ± 5% after 120 h of storage. Within a similar period of time, eyed eggs mortality significantly ( p < 0.05) increased from 2.4 ± 2.4% to 17.2 ± 3.9%. No significant ( p > 0.05) main effect was found among media buffered with Tris–HCl (82.8 ± 3.2%, 73.4 ± 5.4%, 12.1 ± 4.5%), Hepes (88.2 ± 3.4%, 80.7 ± 5.5%, 9.3 ± 3.4%), sodium salt Hepes (77.8 ± 3.8%, 69.3 ± 5.7%, 12.2 ± 3.9%) and coelomic fluid (84.8 ± 3.8%, 77.7 ± 5.1%, 8.9 ± 2.7%) for eyeing, hatching and eyed eggs mortality rates. There was a negative correlation ( r = −0.895, p < 0.001) between eyed eggs mortality and hatching rates. In conclusion, unfertilized eggs of endangered Caspian brown trout can be successfully stored for 48 h without significant loss of fertility. But, storage for 120 h results in the falling of hatching rate. In addition, no significant difference was found between viability rates of ova stored in coelomic fluid and artificial media, 120 h post-storage. It reveals that artificial media could be substituted for coelomic fluid as storage medium at least for 120 h in Caspian brown trout.

Cryopreservation of semen from the endangered Caspian brown trout ( Salmo trutta caspius)

Semen cryopreservation of the endangered Caspian brown trout ( Salmo trutta caspius) and effects of two extenders and three thawing rates on fertilizing ability were studied. After assessment of semen quality, one part of semen was diluted with three parts of extender and filled into 0.5-ml straws. Freezing was carried out at 2 cm above surface of liquid nitrogen and thawed at 5 °C for 90 s, 15 °C for 45 s and 25 °C for 30 s in water baths and used for fertilization. Use of the extender: 0.3 M glucose + 10% methanol + 10% egg yolk, and 0.6 M sucrose + 10% DMSO + 10% egg yolk, yielded 66.6% ± 2.2 and 59.8% ± 5.1 eyeing rates, respectively. Thawing of cryopreserved semen was best at 25 °C water bath for 30 s and significant differences were seen in the eyeing and hatching rates between 25 °C water bath with 5 °C, 15 °C ( p < 0.05). Significant interactions ( p < 0.05) were found between extender type and thawing rate in this study.