Prey size selectivity of pikeperch (Sander Lucioperca L.) fed with topmouth gudgeon (Pseudorasbora Parva Temminck & Schlegel)

M. Gevezova-Kazakova*, M. Yankova, T. Hubenova, A. Zaikov, G. Rusenov

Institute of Fisheries and Aquaculture, 4003, Plovdiv, Bulgaria
(Manuscript received 29 May 2017; accepted for publication 29 July 2017)

Abstract. The aim of this study is to examine the size selectivity of the pikeperch fed with one of the most widespread weed fish in fish farms, such as topmouth gudgeon (Pseudorasbora parva Temminck & Schlegel). Topmouth gudgeon (Pseudorasbora parva Temminck & Schlegel), separated in two size groups: large – group 1 (body weight of the specimens 8.63 ± 2.68 g, total length 9.58 ± 0.92 cm, and height of the body 2.06 ± 0.33 cm) and small – group 2 (body weight of the specimens 1.10 ± 0.36 g, average total body length of 5 ± 0.62 cm, and height of 0.85 ± 0.13 cm), were used for prey. The experiment was carried out under controlled laboratory conditions, in the course of 40 days, in 7 tanks. One pikeperch and 10 topmouth gudgeons from both size groups, in total 20 preys were placed in each tank. During the experimental period it was observed that pikeperch preferred to feed on smaller individuals, the difference in the number of consumed small and large fish is approximately 2 times (70 to 34, respectively).

Biochemical and chemical investigations of pikeperch fingerlings (Sander Lucioperca L.) after wintering

A. Ivanova*, R. Atanasova

Institute of Fisheries and Aquaculture, 248 Vasil Levski, 4003 Plovdiv, Bulgaria (Manuscript received 14 September 2016; accepted for publication 13 October 2016)

Abstract. The purpose of the present study was to investigate some basic biochemical and chemical parameters of pikeperch (Sander lucioperca L.) yearlings reared in ponds after wintering. The investigation has been carried out in the Institute of Fisheries and Aquaculture, Plovdiv. The fish included in the study were randomly selected from one pond, with area of 0.40 ha. Blood samples were collected from 10 pikeperches with average weight from 80 to 100 g. Blood biochemical parameters were individually analysed. For hemoglobin determination, blood was anticoagulated with sodium citrate. Samples for body tissue analysis (without the head and viscera) were collected from 4 fish, autoclaved and used for analysis of water content, % (drying at 105 оС, 24 h; Bulgarian State Standard – SR ISO 5984), protein content, % (Kjeldahl method, Bulgarian State Standard – SR ISO 5983 semi-automated DK 6 digester unit and UDK 132 distillation system, Velp Scientifica), fats (%) by the method of Smidt-Boudzynski Ratzlaff and ash (%) by burning in a muffle furnace at 550 oС, BSS – SR ISO 6496. The average blood serum total protein was 66.1±0.12 g.l-1, blood glucose concentration was 92.8±3.42 mg.100 ml-1 (5.15 mmol.l-1) and average hemoglobin content was 44.7±0.33 g.l-1. The average protein content in analysed fish samples was 16.65±0.23 %. Protein content was the highest among studied dry matter components, followed by the ash (1.97±0.06 %) and fat content (0.84±0.03 %). The levels of blood serum total protein, blood glucose and hemoglobin content as well as body composition parameters – water, protein, fat and ash of pikeperch fingerlings (Sander lucioperca L.) after wintering reflect the specific equilibrium of plastic and energy substances after the winter period, with no deviations from the reference ranges.