RESEARCHES ABOUT NEGRENI LAKE S IHTIOFAUNA

Transcription

1 Analele Ştiinţifice ale Universităţii Al. I. Cuza Iaşi, s. Biologie animală, Tom LIII, 2007 RESEARCHES ABOUT NEGRENI LAKE S IHTIOFAUNA Cătălin Dumitru COSTINIUC 1, Dan STOICA 2 and Ana Maria NECHITA 1 1 Al.I.Cuza University, Departament of Biology, Carol I St, 11, Iasi, Iasi County, Romania, RO costiniuc_catalin@yahoo.com; n_anutza@yahoo.com 2 Al.I.Cuza University, Departament of Geografy and Geology, Carol I St, 11, Iasi, Iasi County, Romania, RO dan_sezu@yahoo.com Abstract. Ichthyologic research regarding the lake of Negreni was conducted between April and August The ichthyologic material was collected using special designated fishing nets of 200 to 230 meters long. The openings of the nets are between 16 and 60 mm. During the fishing operation 13 species were caught, species that can be included in 4 representative families (Cyprinidae, Percidae, Siluridae, Centrarchidae). The ecological characteristics of the above mentioned lake ichthyo-cenosis are presented through diverse ecological indices: numerical stock and gravimetric stock, percentile ratio for numerically defined species individuals, certain parametres concerning the dimensional structure of these populations. Keywords: ihtiofauna, Negreni, ecological indexes. Rezumat. Cercetări privind ihtiofauna lacului Negreni. Cercetările ihtiologice privind lacul Negreni au fost realizate în perioada aprilie 2004 august Colectarea materialului ihtiologic a fost efectuată prin utilizarea de setci cu ochiuri de la 16 la 60 mm, lungimea totală fiind de circa m liniari. Au fost detectate 13 specii aparţinând la 4 familii (Cyprinidae, Percidae, Siluridae, Centrarchidae). Caracteristicile ecologice ale ihtiocenozei prezente în lac au fost redate prin diverşi indici ecologici: stoc numeric şi gravimetric, raportul procentual al numărului de exemplare pe specii, unii parametri privind structura dimensională a populaţiilor. Cuvinte cheie: ihtiofauna, Negreni, indici ecologici. Introduction The Başeu River, 118 km long, covers, inside its basin 916 km 2 and it springs from the Ibaneşti-Herţa Hill at 300 m absolute altitude, running into Prut River at 57 m absolute altitude. The average slope is 2.3 o / oo. (Hăisan et al., 2001) One of the most important retention lakes situated on the course of Başeu River, the Negreni Lake covers 304 hectares having 4.5 km in length and 3.86 in depth, with a retention capacity of 25 millions m 3. The main purpose is that of describing the Negreni Lake ichthyofauna for the intervals, considering that very less attention was given to this area in the last decades. Material and Methods The ichthyofaunistic material was collected with nets of mm openings and in length. From the collected material, statistical representative specimens were separated, identified (the identification was done based on the Banarescu s 2002 identification guidebooks) and measured from the biometric and gravimetric points of view. Then specific ecological indexes, proper to the science of ichthyology, were calculated: numerical and gravimetric stocks, percentile ratio of the individual number by species, dimensional structure of the populations (given by the F/C, Y/C ratios and the A T, A F, S F parameters). The dimensional structure refers to: the participation and importance of diverse species concerning the individuals body measurements, the ratio between carnivorous (C) and plant feeder (F) species, the quantification of available prey (Y) for predatory species -67-

2 Cătălin Dumitru Costiniuc et.al. and, finally, the economical importance of industrial fishing for the discussed ichthyocenosis through the percentage of big predators, economically valuable inside the total ichthyo-cenosis fauna. Consequently, we can apreciate the equilibrium and disequilibrium degrees inside the ichthyo-cenosis, depending on the quantitative ratio between the ecological fish groups (wolfish, unwolfish, prey fish and predators). For the purpose of the present study, the following dimensional classes were considered: small size individuals (S), with no difference on species which, usually, represents the nurture predators; medium size individuals (I), too big to become nurture for predators species and too small to become economically important; big size individuals (A) with economic importance. A different classification criterion refers to the feeding habits: - unrapacious individuals (F) phytophagous, planktophagous; - rapacious individuals (C) belonging to the carnivorous species; - prey individuals (Y) individuals which represents the nurture for rapacious species (including the rapacious seedlings) The equilibrium state of an ichthyo-cenosis can be established through a series of parameters. These parameters are: - the F/C ratio, which means the non-carnivorous - carnivorous ratio; - the Y/C ratio, which shows the prey fish quantity available for one unit of weight from the C fish category; - the A T parameter which represents the percentage of fish with economic value from the total ichthyo-cenosis biomass; - the parameters A and C represent the quantitative abundance of weight category (A, I, S) from the total association, taking count of all individuals from trophic category F (Godeanu S., 1997). Results and Discussion The taxonomic structure the collection put together 13 species belonging to 4 families (Cyprinidae, Percidae, Siluridae, Centrarchidae); there are 11 native species and 2 species introduced (Tab. 1). Table 1. The taxonomic structure of Negreni Lake fish populations. No. Ecologic status Scientific name Popular name Native species Introduced species 1. Carassius auratus gibelio Bloch, 1782 carp * 2. Alburnus alburnus L., 1758 bleak * 3. Cyprinus carpio L., 1758 crap common * 4. Abramis brama Pavlov,1956 carp bream * 5. Pseudorasbora parva Schlegel, 1842 stone moroko * 6. Scardinius erythrophthalmus L., 1758 roşioară rudd * 7. Rhodeus sericeus Bloch, 1782 boarţă bitterling * 8. Gobio gobio L., 1758 gudgeon * 9. Perca fluviatilis L., 1758 perch * 10. Stizostedion lucioperca L., 1758 zander * 11. Silurus glanis L., 1758 catfish * 12. Lepomis gibbosus L., 1758 pumpkinseed sunfish * 13. Gymnocephalus cernuus L., 1758 ruffe * The numeric and gravimetric stocks one can notice a dominance of phytophagus and planktophagus species (carp, bleak, stone moroko), and as far as the rapacious species are concerned, the perch is dominat both from the numerical and -68-

3 Analele Ştiinţifice ale Universităţii Al. I. Cuza Iaşi, s. Biologie animală, Tom LIII, 2007 gravimetric points of view. (Tab. 2). While the dominance of phytophagus species is considered to be a result of controlled introduction and the lake s utilizations habits, the dominance of perch is a result of the great seedlings number as a consequence of abundant zooplankton. No. Table 2. The numerical and gravimetic stoks for the Negreni Lakes fish population. Species Numerical stock Gravimetric stock individuals/100m 2 g/100 m 2 1. Carassius auratus gibelio Bloch Alburnus alburnus L Cyprinus carpio L Abramis brama Pavlov Pseudorasbora parva Schlegel Scardinius erythrophthalmus L Rhodeus sericeus Bloch Gobio gobio L Perca fluviatilis L Stizostedion lucioperca L Silurus glanis L Lepomis gibbosus L Gymnocephalus cernuus L Total The percentile ratio of the individuals numbers by species shows a dominance of bleak (26.6%), followed by carp (18.5%) and stone moroko (14.3%) while the rapturous species are dominated by perch (10.7%) (Fig. 1). Individual no. (%) Figure 1. The percentile ratio of the individuals numbers by species 1. carp, 2. bleak, 3. common carp, 4. carp bream, 5. stone moroko, 6. rudd, 7. bitterling, 8. gudgeon, 9. perch. 10. zander, 11. catfish, 12. pumpkinseed sunfish 13.ruffe. -69-

4 Cătălin Dumitru Costiniuc et.al. The dimensional structure of the fish populations By determining the dimensional structure of the entire sampling stock, the equilibrium or dis-ecquilibrium statuses of the whole ichthyo-cenosis can be evaluated. Nurishmen t habits Table 3. The dimensional structure of the fish populations. No. Species DIMENSIONAL GROUPS AGE GROUPS Biomass (%) Juvenile Adults S I A S I A J % A % 1. carp bleak common carp carp bream stone moroko rudd bitterling gudgeon NON-RAPTUORUS perch zander catfish pumpkinseed sunfish 13. ruffe RAPTUROUS Total TOTAL F (total) F/C C (total) 6950 / 1626 = Y (total) Y/C C (total) 2772 / 884 = 3.13 Unrapacious Rapacious A T = 35.94% A F = 42.07% S F = 29.20% F/C = the ratio between non-carnivorous and carnivorous Y/C = the quantity of pray fish available as nurishment for a unity of weight from the C category A T = the percentage of fishable individuals from the total lake s biomass A F = the quantitative abundance of the A category inside the association, considering all the individuals from the F trophic category. S F = the quantitative abundance of the S category inside the association, considering all the individuals from the F trophic category. Table 3 includes the values of biomass by dimensional groups and species. The F/C ratio is 4.27 being in the optimal interval for an equilibrium status and the Y/C ratio is 3.13 describing a balanced association, very close to the optimal status. The A T values is 35% belonging to the equilibrium status range but, still, feckless; this feckless feature is emphasized also by the value of S F which is and indicates an overload of individuals from the I F category (Fig. 2). -70-

5 Analele Ştiinţifice ale Universităţii Al. I. Cuza Iaşi, s. Biologie animală, Tom LIII, 2007 Figure 2. The diagrams of optimal values domains and the deviations from these domains for the F/C, Y/C ratios and the A T, S F, and A F parameters (after Godeanu S., 1997). Conclusions The Negreni Lake ichthyo-cenosis contains 13 species of fish, 11 of them being native ant 4 of them introduced from other ichthyo-cenosis. The numerical stock in medium is about individuals/100m 2 and the gravimetric stock is about 932 g/100m 2. The percentile ratio of the individuals numbering by species shows the dominance of the bleak (26.6%), followed by the carp (18.5%) and, the rapacious species are dominated by perch (10.7%). The dimensional structure of the populations indicates a balanced ichthyocenosis per total but, still, inefficient from the economic point of view. -71-

6 Cătălin Dumitru Costiniuc et.al. References Bănărescu,P., Class Osteichthyes, în Diversitatea Lumii Vii, Vol. II, Apele Continentale. ed. Bucura Mond, 692 pg. Bănărescu, P., Fauna R.P.R., Pisces-Osteichthyes. XIII, Ed. Acad., Bucureşti, 959 p. Godeanu, S., Elemente de monitoring ecologic/integrat, Ed. Bucura Mond, Bucureşti, 183 p. Hăisan, E., Davideanu, G., Iliescu, S., Sbiera, S., Avârvarei, C., The river Prut. Description of the Romanian part of the river and its catchment area. RIZA work document, Lelystad, 29 p. -72-