Konrad Dabrowski

Estimation of sperm concentration of rainbow trout, whitefish and yellow perch using a spectrophotometric technique

Abstract Milt was collected individually from rainbow trout ( Oncorhynchus mykiss ), whitefish ( Coregonus clupeaformis ) and yellow perch ( Perca flavescens ) and sperm density measured by three different methods: measuring spermatocrit value, counting sperm using a Neubauer counting chamber, and by measuring absorbance at 505 nm. Sperm concentration significantly differed between yellow perch (41.58±3.5×10 9 ml −1 ) and the two other species, rainbow trout (11.80±6.19×10 9 ) and whitefish (7.95±2.57×10 9 ). In diluted yellow perch sperm and directly sampled sperm of whitefish and rainbow trout, correlation coefficients were highly significant between spermatocrit, counting, and the spectrophotometric method of measurement. It is suggested that sperm concentration measured by optical density offers a quick and accurate method of determining sperm concentration.

Protein requirements of grass carp fry (Ctenopharyngodon idella Val.)

Abstract The study was aimed at determining the optimal level of protein in a casein diet for grass carp. There was a linear relationship between the percentage of protein in the diet and the increase in fish protein and weight up to optimal levels of 41 and 43%, respectively. No further increase in fish protein or weight was noted with diets containing up to 64% of protein. However, if the optimal level was defined by the parabolic curve with the formula y = 36.21 + 6.238x − 0.0593x2, it would equal 52.6 ± 1.93%. Net protein utilization (NPU) values for experimental diets were obtained using a formula which took the maintenance nitrogen metabolism on a non-protein diet into consideration. This NPU formula was related to the length of the experiment, difference in the weight of fish at the beginning of the experiment, and growth of fish fed protein diets. Both protein efficiency ratio (PER) and NPU decreased with the increase in protein content of the diets according to the formulae y = 1.966−0.018x and y = 40.8−0.327x + 302.6 x , respectively.

Studies on the role of exogenous proteolytic enzymes in digestion processes in fish

Studies were carried out on the proteolytic activity of the fry of common carp, rainbow trout, grass carp, and whitefish, as well as on the activity of digestive organs of adult common carp and rainbow trout. Activity of exogenous enzymes in relation to endogenous ones was assessed on the basis of the proteolytic value of fish food and the activity of digestive organs. It was found that the share of proteolytic enzymes of natural food in the digestion process in fish was high. Beginning from a weight of 50–100 g for common carp and 10 g for rainbow trout, the relation between the daily enzymatic ration and the weight of fish indicates the cooperation of an approximately constant amount of exogenous enzymes.

Relationship between biochemical constituents of fish semen and fertility: the effect of short-term storage.

Spermatozoa and seminal plasma obtained from rainbow trout and whitefish were analyzed in respect to their aspartate aminotransferase (AspAT) and alkaline phosphatase activities. In particular, the experiments characterized AspAT optimum pH, optimization of assay conditions and action of coenzyme, pyridoxal 5-phosphate (vitamin B6). The effect of short-term semen storage at 0°C on biochemical indicators and fertilization rate was examined in both species. The concentrations of reduced and oxidized ascorbic acid in seminal plasma of both species were several folds higher than in spermatozoa and blood plasma of fish. Highly significant correlations were found for both species between AspAT activity (sperm or seminal plasma) and fertilization rate (% of eyed-stage or hatched embryos). For rainbow trout, highly significant correlations were found between sperm concentration, motility and fertilization rate. These results suggest that several biochemical indicators of seminal plasma can be used as measures of sperm quality of fish. Some common biochemical parameters for fish and mammals semen provide evidence for using fish sperm as a model in biomedical research.

Digestion of protein by rainbow trout (Salmo gairdneri Rich.) and absorption of amino acids within the alimentary tract

Abstract 1. 1. The alimentary tract content has been divided into the stomach, pyloric caeca region, the middle intestine and the posterior intestine which was parted into two equal segments. 2. 2. Protein and free amino acids were analysed in digesta of subsequent parts of digestive tract in fish fed three different diets. 3. 3. An indirect method of apparent digestibility was employed to ascertain the absorption site of particular amino acids. 4. 4. A separate trial was performed to determine the metabolic amino acids excretion with the use of non-protein diet. Assuming that traces of amino acids supplied in non-protein diet should be subtracted from the metabolic ones, the metabolic amino acid excretion was calculated for subsequent parts of digestive tract. 5. 5. On the basis of the knowledge of metabolic amino acid excretion, the true digestibility of examined diets was calculated in the parts of digestive tract.

Objective analysis of sperm motility in the lake sturgeon, Acipenser fulvescens: activation and inhibition conditions

Abstract An objective analysis of the duration of motility of sperm from the lake sturgeon, Acipenser fulvescens , has been performed using computer-assisted sperm motion analysis at 200 frames/s. Motility was measured in both 1993 and 1994. The percentage of activated motile sperm and their velocities ([1993] curvilinear velocity: 313 μm/s; straight-line velocity: 129 μm/s) were unchanged after 5 min in Tris/glycine buffer, pH 9.0, with 10 mM added Na + . Qualitative, visual measurements revealed motility lasting for 30 min in this medium. The percentage of motile cells, but not the velocities of the motile cells, was reduced by the addition of potassium to the Tris/glycine buffer. The percentage of motile sperm was inhibited by 50% at 0.5 mM added K + . Elemental analysis of seminal plasma revealed the following concentrations: P (3.02 mM); K (5.78 mM); Ca (0.16 mM); Mg (0.21 mM); Na (25.6 mM); Zn (0.76 μM); and Cl (5.41 mM). Differences between two years of milt collection were not significant.

The effect of egg fatty acid concentrations on embryo viability in wild and domesticated walleye (Stizostedion vitreum)

Abstract Eggs from three distinct populations of walleye Stizostedion vitreum , one domesticated (London State Fish Hatchery) and two wild (Lake Erie and Salt Fork Reservoir), were compared in terms of total lipid content and fatty acid profiles (phospholipids and neutral lipids). The concentrations of total lipids in eggs from domesticated broodstock were significantly lower (8.6 ± 1.0 % of wet weight) than those of both wild populations (13.3 ± 0.9 % and 10.9 ± 0.6 % of wet weight for Lake Erie and Salt Fork Reservoir, respectively). The profiles of fatty acids in egg lipids differed significantly among the three investigated populations. Domesticated females fed a formulated diet produced eggs containing significantly higher levels of linoleic acid (18:2n-6), characteristic of plant lipids. However, arachidonic acid (20:4n-6), was at significantly higher levels in eggs of wild walleye stocks. Although eicosapentaenoic acid (20:5n-3) was detected at significantly higher levels in eggs from Lake Erie walleye, docosahexaenoic acid (22:6n-3), the most abundant in polar lipids, was found at similar levels in eggs of all three populations. Survival of walleye embryos was correlated with the concentrations of polyunsaturated long chain fatty acids. Our data suggest that deficiency in n-3 fatty acids might be associated with impaired development of walleye, and thus poor larval and juvenile viability.

Mouth size and predicted food size preferences of larvae of three cyprinid fish species

Abstract Mouth size was examined in larvae and juveniles of three cyprinid fish species: grass carp (Ctenopharyngodon idella Val.), silver carp (Hypophthalmichthys molitrix Rich.) and bighead carp (Aristichthys nobilis Rich.). A linear relationship was found between mouth size and the total length of fish, from the initial exogenous feeding stage up to 20–30 mm. Based on the mouth size, the size of the prey which could be consumed was calculated assuming 45° of mouth opening for optimum prey width and 90° for maximum prey width. Food particle size considered to be suitable for commencement of feeding amounted to 50–90 μm for silver carp larvae, 90–150 μm for grass carp larvae and 150–270 μm for bighead carp larvae. These criteria can be applied to moving rotifiers and nauplii as well as to the motionless particles of compound, dry diets.

The use of fish meal and soyabean meal as a protein source in the diet of grass carp fry

Abstract Diets based on fish meal and soyabean meal were fed to grass carp fry, the average body weight of each individual being 0.4 g. During the 70 days of the experiment, the best results were obtained with a diet containing 40% fish meal, when growth increment, protein efficiency ratio and apparent net protein utilization amounted to 209, 1.26 and 20.3, respectively. There was a deficiency in sulphuric amino acids in both fish meal- and soyabean meal-containing diets, and this was particularly marked in the latter. A significant decrease in available lysine was found in the diets containing soyabean meal. The main reason for the retardation in fish growth and the reduction of protein utilization when soyabean meal content is increased in the diets, seemed to be that the destruction of anti-nutritional factors by the heat processing of the meal was only partial.

Free amino acid leaching from a protein-walled microencapsulated diet for fish larvae

The leaching loss of free amino acids (FAA) from an experimental protein-walled microencapsulated diet (MC) for larval fish after immersion in water was measured and compared with leaching loss from a gelatin microbound diet (MB) containing the same dietary ingredients. The loss of FAA (as a percentage of total dietary FAA) was significantly higher in the MB diet compared to the MC diet. After 5 min of re-hydration, 22% of FAA were leached from the MB diet compared with 8% from the MC diet. After 60 min, 85% of FAA from the MB diet were leached into the water compared to 17% from the MC diet. The addition of free lysine to protein-walled microcapsules (MC-L) was also investigated to determine the suitability of MC for delivering specific FAA. Lysine was incorporated into the particles with an efficiency of 7.5% and accounted for approximately 60% of the total FAA in the diet. The loss of this amino acid from MC-L after 60 min of immersion was 1.4%. The loss of specific FAA from MB and MC diets was found to be negatively and positively correlated to the hydrophobic character (hydropathy index) of each FAA, respectively. These results support the use of protein-walled microcapsules as a vector for specific dietary amino acids using a macronutrient-balanced diet.