Influence of the rearing conditions on the sterlet (Acipenser ruthenus (Linnaeus)) morphological and biological parameters

Abstract

Paper shows research data considering investigation and analysis of specific technological parameters due to external and internal marks of sterlet.

Our research goal is to analyze influence of specific sterlet rearing conditions on the morphological, biochemical and hematological marks.

Sterlet fry and fingerlings were the object of investigation.

Sterlet fingerlings rearing was conducted in experimental ponds (2 ha square) of Dnieprovsky surgeon fish hatching facility. Three variances were formed: І – without fertilizers; ІІ – with organic (3 t/ha) and inorganic fertilizers (50 kg/ha); control – with organic fertilizers (5 t/ha). Stocking density in ponds ranged 95k-100k  fishes/ha, stock bodymass ranged from 77,5 to 85,0 mg.

Analysis of hydrochemical, morphometric and fishery marks was made according to well-known methods.

Water temperature was ranged from 20°С to 27°С, average 24,2–25,4°С. Dissolved oxygen was about 4,6-10,4 mgО₂/dm³.

Phytoplankton biomass in I variance ponds ranged from 9,95 to 11,05 g/m³, in II variance ponds – 13,6-16,0 g/m³. The most abundant zooplankton and zoobenthos was registered in second variance, which was caused by using organic and inorganic fertilizers. Thus, zooplankton biomass was about 8,3–8,6 g/m³, zoobenthos –6,69–7,71 g/m².

As a result of rearing we received sterlet fingerlings with average individual bodymass 3,2±0,25 g (I variance), 4,17±0,30 g (II variance). The best survival rate (69.55%) and fish productivity (267kg/ha).

We can see apparent difference in morphometric if we compare body length (M_diff = 3,28-4,08.), pectoventral distance (M_diff = 3,10-3,28) and bodymass (M_diff = 3,22-3,96).

Fulton’s condition factor was ranged from 0,70 in I variance (Cv = 28,21%) to 0,80 in II variance (Cv =27,73%).

Analyzing chemical composition of sterlet fingerlings muscle tissue, we defined that moisture was about 80,0–82,2%, lipids – 1,8–2,0%, inorganic – 0,9–1,4%. Protein ranged from 12,6-12,9% (I variance) to 15,0-15,4% (II variance). Overall, biochemical marks of sterlet fingerlings corresponded to physiological standard for this age category. Sterlet fingerling muscle tissue contained less than 0,05% of ammonia, 35,6-50,0 mg/kg of nitrates, 0,6-1,8 mg/kg of nitrites, 190,0-220,0 mg/kg of phosphorus, 0,2-0,22% of NaCl. Acid value for lipids ranged from 0,1 to 0,3 mgКОН.

Comparative hematology analysis defined that haemoglobin concentration in different variances ranged from 85 to 159 g/l.

Red blood cells concentration was about 0,51-0,93 Т/l, leucocytes - 153-208 g/l, thrombocytes – 25-106 g/l. Relative standard deviation for red blood cells – from 11,8 to 36,4%.

Mathematical analysis allowed us to build polynomial equations with coefficient of determination as much as 0,7892–0,9083.

Also we investigated influence of rearing conditions in ponds of different fish farms on the separate blood marks.

We defined reasonable correlation between level of intensification and main fishery indexes, such as bodymass, fish productivity and survival rate and biochemical marks.

Obtained data complement existing technology of sterlet combined rearing in ponds of Southern Ukraine due to its later introduction into natural water reservoirs. Also obtained data may be used in modern aquaculture according to its rearing goals.

 Keywords: sterlet, fingerling, pond rearing, intensification, fertilizer, survival rate, average individual bodymass, fish productivity, red blood cells, protein, fat.