AGE AND GROWTH OF THE PERCH (Perca fluviatilis L.) IN THE SOLINA AND ROZNOW DAM RESERVOIRS

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1 Acta Sci. Pol., Piscaria 4(1-2) 25, 43-5 AGE AND GROWTH OF THE PERCH (Perca fluviatilis L.) IN THE SOLINA AND ROZNOW DAM RESERVOIRS Piotr Epler, Ewa uszczek-trojnar, Magdalena Socha, Ewa Dr g-kozak, Pawe Szczerbik Agricultural University in Kraków, Poland Abstract. Age and growth of the perch inhabiting the Solina and Ro nów dam reservoirs were studied on 124 and 26 perch individuals, respectively. Age of the fish collected in the Solina was found to range from 3 to 1 years (uncertainty coefficient of 17%), the Ro nów perch age varying from 2 to 12 years (uncertainty coefficient of 1%). In the Solina dam reservoir, the perch aged 4+ and 5+ were the most numerous groups, the age groups most numerous in the Ro nów encompassed the 5+ to 9+ interval. The highest annual body length gains in the Solina reservoir were observed in the perch aged 4+, 6+, 8+, and 9+, the respective gains amounting to 43.2; 44.4; 44.3, and 48.4 g. In the Ro nów reservoir, the highest length gains (55 g) were typical of the perch aged 1+ and 12+. Coefficients of condition were found to range within and in the Solina and Ro nów reservoirs, respectively. Key words: age, dam reservoirs, growth, Perca fluviatilis, perch INTRODUCTION Perch is a species common to all types of European freshwater reservoirs. It is characterised by a low growth rate and high adaptive potential under new environmental conditions [Bryli ska 2, Bieniarz and Epler 24]. The species is regarded as a food competitor to more valuable predatory fish, thus it plays a controlling role in the fish fauna of a reservoir. Studies on the Solina dam reservoir fish fauna, based on commercial catches, revealed the perch to rank third, after bream and roach, in terms of the number of fish caught; the species accounted for 4.8% of all the fish caught. A similar pattern was provided by the analysis of anglers catches; in 1988 and 1989, the perch ranked fourth (8.1 and 3.1% of all the fish caught, respectively), whereas its rank increased to third Corresponding author Adres do korespondencji: Prof. dr hab. Piotr Epler, Department of Ichthyobiology and Fisheries, Agricultural University in Cracow, Spiczakowa 6, Kraków- -Mydlniki, Poland, rzbienia@kinga.cyf-kr.edu.pl

2 44 P. Epler et al. in 199 (17.3% of all the fish caught) [Bieniarz and Epler 1993]. Perch records in the commercial catch statistics on the Ro nów dam reservoir are scant and evidence low abundance (from.1 to.5% of all the fish caught) [Masty ski 1985]; in subsequent years, the proportion of perch in catches, both commercial and those attributed to anglers, was observed to increase. The angling statistics showed the perch to account for % [Bieniarz et al. 199]. Perch is a slowly growing fish that extend the food chain and are highly predatory with respect to young developmental stages of other, valuable fish species [Bryli ska 2, Bieniarz and Epler 24]. When overly abundant, the perch become smaller and smaller, for which reason excessive abundances are not beneficial from the standpoint of fisheries and angling. Therefore, knowledge on age and growth of the perch in the Solina and Ro nów dam reservoirs should contribute to rationalising the fisheries and angling and to developing approaches aimed at limiting the perch population size. MATERIALS AND METHODS The study involved perch individuals collected in from sporadic commercial catches with gill nets and by angling; the Solina and Ro nów dam reservoirs supplied 124 and 26 individuals, respectively. All the fish were measured (total length, longitudo totalis [l.t.] and fork length, longitudo corporis [l.c.], to.5 cm and weighed to 5 g. Age was determined from scales, collected from each individual from below the lateral line on the side of the body at the height of the second ray of the first part of the dorsal fin. Age was read from the number of annual rings [Heese 1992]. As the perch ctenoid scale is difficult to be read correctly due to the frequent presence of additional annuli, it was decided to assess the uncertainty of the reading by calculating the uncertainty coefficient (as proposed by Sych [1971]) as a ratio between the uncertainty sum ( W) and the number of fish examined (N): W/N. The perch growth increments were determined from direct measurements, taken with the Zietz projector or a stereomicroscope. The condition coefficient was determined using the Fulton formula K = 1W/l 3, where W is the fish weight (g) and l is the fish length (cm). RESULTS AND DISCUSSION The age of the perch examined was determined at (uncertainty coefficient of 17%); most numerous were the age groups 4 + and 5 + (37.9 and 27.41% of all the fish examined), followed by 3 + (12.9%), 8 + (7.25%), 6 + and 1 + (4.83% each), 7 + (4.9%), and 9 + (2.41%) (Table 1). Length increments of the perch examined should be regarded as low, compared with length gains of the perch inhabiting the dam reservoirs of Gocza kowice [Suskiewicz 1961] or Koz owa Góra [Skóra 1964], particularly contrasting in older age groups (Table 2). Acta Sci. Pol.

3 Age and growth of the perch 45 Table 1. Summary of data on total length (l.t.), fork length (l.c.), body weight, fork length (l.c.) gains, and body weight gains of perch in the Solina reservoir Tabela 1. D ugo ca kowita (l.t.), d ugo cia a (l.c.), masa cia a oraz przyrosty l.c. i masy cia a okonia w zbiorniku zaporowym Solina Age Percentage, % Odsetek, % Mean l.t., cm rednia l.t., cm Mean l.c., cm rednia l.c., cm Mean body weight, g rednia masa cia a, g l.c. gain, cm Przyrosty l.c., cm Body weight gain, g Przyrosty masy, g Total Razem Table 2. Perch fork length (l.c.) gains in the Solina and in other Polish dam Tabela 2. Porównanie przyrostu d ugo ci cia a (l.c.) okonia ze zbiornika zaporowego Solina z przyrostami d ugo ci cia a tego gatunku w innych zbiornikach zaporowych Polski Age Reservoir Zbiornik 3 + / / / / / / /1 + Reference Autor Gocza kowice Suskiewicz, 1961 Koz owa Góra Skóra, 1964 Solina This study Badania w asne The Fulton condition coefficient was found to range from 1.23 (3 + ) to 1.55 (1 + ) and did not vary much in individual age groups; not did it differ from the values found in other reservoirs. The mean fork length (l.c.)-based comparison of fish growth between the Solina and Ro nów perch and the conspecific fish in other dam reservoirs (Gocza kowice [Suskiewicz 1961] and Koz owa Góra [Skóra 1964]) and lakes in the vicinity of W gorzewo [ uromska 196] and Lake Wdzydze [Zawisza and Karpi ska-walu 1961] show the Solina perch growth to be similar only in the fish aged 3 and 4, to decrease markedly later on (Fig. 1). The data presented above show the Solina reservoir to fail to offer the perch a suitable conditions for growth. This is most probably due to the too abundant perch population in the reservoir, poor food resources, and low water temperature. Piscaria 4(1-2) 25

4 46 P. Epler et al. The species, however, plays an important biological role in the reservoir. As a predator, it controls populations of cyprinids, abundant in the Solina dam reservoir, and is an attractive angling target, distinct by virtue of its tasty meat (individuals aged 6 and more years are most desirable in this respect). The management of the perch population in the Solina reservoir should aim at harvesting young fish with small-meshed trawls. Reduction of the abundance of young fish will make it possible for the remaining fish to grow more rapidly to a larger size, which will render them more attractive to anglers. 35 Fork length (l.c.), cm D ugo cia a, cm W gorzewo Wdzydze Gocza kowice Koz owa Góra Solina Age Age Fig. 1. Perch growth in the Solina dam reservoir (this study) versus growth in other dam reservoirs (Gocza kowice and Koz owa Góra), lakes near W gorzewo, and Lake Wdzydze Rys. 1. Porównanie wzrostu okonia w zbiorniku zaporowym Solina (badania w asne) ze wzrostem tego gatunku w innych zbiornikach zaporowych Gocza kowice i Koz owa Góra oraz w jeziorach z okolic W gorzewa i jeziora Wdzydze The Ro nów reservoir perch were found to range in age from 2+ to 12+ years (Table 3), the uncertainty coefficient amounting to 1%. Most numerous were the age groups 5+, 6+, 8+, 7+, and 4+ which accounted for 18.4, 18, 18, 17, and 12.1%, respectively, of the perch population under study. The remaining age groups contributed from 7.76 (9+) to.48% (2+ and 3+) to the population. The total and fork length were found to vary within cm and cm, respectively (Table 3). The highest mean annual fish length gains occur between the third and the fourth (3.8 cm), the fourth and the fifth (3.1 cm) as well as the fifth and the sixth (3. cm) years of life (Table 3). Acta Sci. Pol.

5 Age and growth of the perch 47 Table 3. Age, total length (l.t.), fork length (l.c.), and annual length increments of perch in the Ro nów dam reservoir Tabela 3., d ugo ca kowita, d ugo cia a i roczne przyrosty d ugo ci cia a badanych okoni z Ro nowa Age Percentage, % Odsetek, % Mean l.t., cm rednia l.t., cm Mean l.c., cm rednia l.c., cm Mean body weight, g rednia masa cia a, g l.c. gain, cm Przyrosty l.c., cm Body weight gain, g Przyrosty masy cia a, g Total Razem The lowest mean annual length increments were typical of the oldest fish and varied from 1.7 cm (1+/11+) to 1. cm (11+/12+) (Table3). The mean annual body weight gains ranged from 1 to 55 g, the highest increments being shown by the age groups 1+ and 12+. The Fulton condition coefficient was found to range from 1.27 to Fork length (l.c.), cm D ugo cia a, cm Ro nów Gocza kowice W gorzewo Wdzydze Koz owa Góra Chany Age Age Fig. 2. Growth of perch in the Ro nów reservoir (this study), compared with that in reservoirs (Gocza kowice and Koz owa Góra), W gorzewo lakes, Lake Wdzydze, and Lake Chany Rys. 2. Wzrost okonia ze zbiornika Ro nów (badania w asne) w porównaniu ze wzrostem okonia w zbiornikach Gocza kowice i Koz owa Góra oraz w jeziorach z okolic W gorzewa, jeziorze Wdzydze i Chany Piscaria 4(1-2) 25

6 48 P. Epler et al. Comparison between the Ro nów and other dam reservoirs and lakes in terms of perch growth showed the growth in the initial years of life to be similar between the Ro nów and the Gocza kowice [Suskiewicz 1961] and the Koz owa Góra [Skóra 1964] as well as in lakes near W gorzewo [ uromska 196] (Fig. 2). However, as of the sixthseventh year of life, the Ro nów perch growth becomes much slower, as the 6-year-old individuals in the Ro nów are by as much as 5.4 cm smaller than their contemporaries in the Gocza kowice. A similar pattern is revealed by comparing mean annual size increments between the Ro nów perch and the perch from other water bodies (Fig. 3). Fork length increases, cm Przyrosty d ugo ci cia a (l.c.), cm Ro nów Gocza kowice W gorzewo Wdzydze Koz owa Góra Chany 2/3 3/4 4/5 5/6 6/7 7/8 8/9 9/1 1/11 11/12 Age Age - Fig. 3. Annual length increments of perch in Ro nów reservoir (this study), compared to those in other reservoirs (Gocza kowice and Koz owa Góra), W gorzewo lakes, Lake Wdzydze, and Lake Chany Rys. 3. Roczne przyrosty d ugo ci cia a okonia w zbiorniku Ro nów (badania w asne) w porównaniu z przyrostem w zbiornikach: Gocza kowice oraz w Koz owej Górze, jeziorach z okolic W gorzewa, jeziorze Wdzydze i Chany The species growth potential under favourable conditions is evidenced by studies in Lake Chany, reported by Berg [1949]: the mean length in all the age groups was higher than that in other water bodies by 5-1 cm (Fig. 2). CONCLUSIONS The study presented evidences a necessity to reduce the abundance of younger perch age groups by using small-mesh trawls, which will assist in protecting the fry of other fish species, valuable for the water body. The large perch, occurring with a somewhat lower abundance, is a fine fish, attractive for anglers. Acta Sci. Pol.

7 Age and growth of the perch 49 Mean fork length (l.c.), cm rednia d ugo cia a (l.c.), cm Solina Ro nów Age Age Mean body weight, g rednia masa cia a, g Age Fig. 4. Perch growth in the Solina and Ro nów dam reservoirs Rys. 4. Porównanie wzrostu okonia z Soliny i Ro nowa ( rednia d ugo i masa cia a) A direct comparison of mean length and weight increments of the perch inhabiting the two dam reservoirs discussed (Fig. 4) shows the fish to attain higher length and weight gains in the Ro nów, which is most probably related to the water temperature regime there. REFERENCES Berg L.S., Ryby presnych vod SSSR i sopredelnych stran [The freshwater fish of the USSR and neighbouring countries]. Wydaw. Akad. Nauk SSSR Leningrad Moskva [in Russian]. Bieniarz K., Epler P., Po owy w dkarskie na Soli skim zbiorniku zaporowym [Anglers catches in the Solina dam reservoir]. Rocz. Nauk. PZW. 6, 5-18 [in Polish]. Bieniarz K., Epler P., 24. Zoologia [Zoology]. Vol. V. Wydaw. Albatros, Kraków [in Polish]. Bieniarz K., Epler P., Sych R., 199. Po owy w dkarskie na Ro nowskim Zbiorniku Zaporowym [Anglers catches in the Ro nów dam reservoir]. Rocz. Nauk. PZW 3, [in Polish]. Bryli ska M., 2. Ryby s odkowodne Polski [The freshwater fishes of Poland]. PWN, Warszawa [in Polish]. Heese T., Optymalizacja metody okre lania tempa wzrostu ryb za pomoc odczytów wstecznych [Optimisation of back reading-based method of fish growth estimation]. Monogram 42, WSI, Koszalin [in Polish]. Masty ski J., Gospodarka rybacka, mo liwo ci produkcyjne wybranych zbiorników zaporowych Polski [Fishery management, production potential of selected dam reservoirs of Poland]. Rozpr. AR Pozn. 146 [in Polish]. Skóra S., Wzrost i od ywianie si okonia w zbiorniku zaporowym w Koz owej Górze [Growth and feeding of perch in the Koz owa Góra dam reservoir]. Acta Hydrobiol. 6, [in Polish]. Piscaria 4(1-2) 25

8 5 P. Epler et al. Suskiewicz T., Oko (Perca fluviatilis L.) w zbiorniku Gocza kowickim [The perch (Perca fluviatilis L.) in the Gocza kowice dam reservoir]. Acta Hydrobiol. 3, [in Polish]. Sych R., Elementy teorii oznaczania wieku ryb wed ug usek. Problem wiarygodno ci [Elements of theory of scale-based fish age estimation. The reliability problem]. Rocz. Nauk. Rol. ser. H. 1, 93, [in Polish]. Zawisza J., Karpi ska-walu B., Wzrost ryb w jeziorze Wdzydze [The fish growth in Lake Wdzydze]. Rocz. Nauk. Rol. ser. D, 93, [in Polish]. uromska H., 196. Wzrost okonia (Perca fluviatilis L.) w jeziorach okolic W gorzewa [The growth of perch (Perca fluviatilis L.) in lakes near W gorzewo]. Rocz. Nauk. Rol. ser. B2, 77, [in Polish]. WIEK I WZROST OKONIA (Perca fluviatilis L.) W ZBIORNIKACH ZAPOROWYCH SOLINA I RO NÓW Streszczenie. Opracowanie zawiera wyniki bada nad sk adem wiekowym i wzrostem okoni ze zbiorników zaporowych Solina oraz Ro nów. Materia badawczy stanowi o 124 okonie ze zbiornika Solina oraz 26 okoni ze zbiornika Ro nów. okoni ze zbiornika Solina waha si od 3-1 lat (przy wspó czynniku w tpliwo ci 17%), a w zbiorniku Ro nów od 2 do 12 lat (przy wspó czynniku w tpliwo ci 1%). W Solinie najliczniej reprezentowane by y roczniki 4+ i 5+, w Ro nowie 5+ do 9+. Najwi ksze przyrosty d ugo ci cia a stwierdzono w Solinie u okoni rocznika 4+ (3 cm), a w Ro nowie u roczników 4+, 5+ i 6+ (3,8; 3,1 i 3, cm). Najwi ksze roczne przyrosty masy cia a okoni z Soliny zaobserwowano w 4+, 6+, 8+ i 9+ roku ycia, które wynosi y odpowiednio: 43,2; 44,4; 44,3 i 48,4 g, a u okoni z Ro nowa u roczników 1+ i 12+ po 55 gramów. Wspó czynniki kondycji u okoni z Soliny waha y si w granicach 1,23 do 1,55, a u okoni z Ro nowa od 1,27 do 1,62. S owa kluczowe: Perca fluviatilis, wiek, wzrost, zbiorniki zaporowe Accepted for print Zaakceptowano do druku: Acta Sci. Pol.