Scholarly article on topic 'Growth Rate and Histological Picture of the Gonads of Pike, Esox Lucius L., and Pikeperch, Sander Lucioperca (L.), from the Tresna Reservoir (Lake Żywieckie)'

Growth Rate and Histological Picture of the Gonads of Pike, Esox Lucius L., and Pikeperch, Sander Lucioperca (L.), from the Tresna Reservoir (Lake Żywieckie) Academic research paper on "Animal and dairy science"

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Academic research paper on topic "Growth Rate and Histological Picture of the Gonads of Pike, Esox Lucius L., and Pikeperch, Sander Lucioperca (L.), from the Tresna Reservoir (Lake Żywieckie)"

Arch. Archives

Vol. 16 Fasc. 2 147-154 2008

Pol. Fish. of Polish Fisheries

GROWTH RATE AND HISTOLOGICAL PICTURE OF THE GONADS OF PIKE, ESOX LUCIUS L., AND PIKEPERCH, SANDER LUCIOPERCA (L.), FROM THE TRESNA RESERVOIR (LAKE ZYWIECKIE)

Piotr Epler, Ewa tuszczek-Trojnar, Magdalena Socha, Pawel Szczerbik, Miroslawa Sokolowska-Mikolajczyk, Wlodzimierz Popek

Department of Ichthyobiology and Fisheries, University of Agriculture in Krakow, Poland

ABSTRACT. The aim of this study was to determine the growth rates of pikeperch, Sander lucioperca (L.), and pike, Esox lucius L., from the Tresna Reservoir. Back-calculations were used to determine fish age. Histological pictures were used to determine the spawning success of the two species compared. The study material was comprised of 18 pikeperch females and 13 males, and 20 pike females and 12 males. The growth rate of pikeperch from the Tresna Reservoir was higher in comparison to populations inhabiting other basins in Poland. The histological analyses of the gonads indicated that pikeperch spawned successfully in the reservoir. The growth rate of the pike in the reservoir was comparable to that of this species in other basins. However, the histological picture of the ovaries indicated that spawning was only partially successful since 25% of females did not spawn and their eggs were in a state of resorption.

Key words: GROWTH RATE, GONAD HISTOLOGY, PIKEPERCH, PIKE

INTRODUCTION

Pike, Esox lucius L., occurs in the fresh and brackish waters of Europe and North America (Zalachowski 2000). Until the 1970s, it occurred rather commonly in Poland (Kowalska et al. 1976), but currently the abundance of populations of this species are in decline in various basins, including dam reservoirs (Jelonek et al. 2003a). Pike populations increase in size in the first years following reservoir inundation, but then they begin to decline (Heese and Mastynski 1990) due to limited reproductive opportunities or from intense angling and fishing pressure (Bieniarz et al. 1990a, b). The share of pike in commercial catches made in reservoirs in Poland is small

CORRESPONDING AUTHOR: Piotr Epler, University of Agriculture in Krakow, Department of Ichthyobiology and Fisheries, Prof. Spiczakowa 6, 30-199 Krakow, Poland, Tel./Fax: +48 12 6375176, +48 12 6385979; e-mail: rzbienia@kinga.cyf-kr.edu.pl

DOI 10.2478/s10086-008-0012-6

(Falkowski and Wisniewolski 2003, Falkowski 2005, 2006, 2007). In the 2002-2006 period, it ranged from 2 to 3.8% of the biomass of the fish caught.

Pikeperch, Sander lucioperca (L.), was introduced to Polish reservoirs mainly through stocking programs. In recent years, an increased share of this species has been noted in commercial catches. In the 1960-1974 period, the biomass of pikeperch in overall catches ranged from 0.9 to 1.3% (Terlecki 2000), while in the 2002-2006 period this figure had increased to a range of 2.2 to 4.4% (Falkowski and Wisniewolski 2003, Falkowski 2005, 2006, 2007).

The aim of the study was to determine the ages and growth rates of pike and pikeperch from the Tresna Reservoir and to identify the maturity stage of the gonads during the catch period as this would permit determining spawning success.

MATERIALS AND METHODS

The study material was comprised of scales and gonad samples collected from pike and pikeperch from commercial fishing and angling in July and August from 1999 to 2001 in the Tresna Reservoir. Thirty-two pike and 31 pikeperch were obtained for the study (Table 1). Scales were collected from these individuals, they were weighed, and their body lengths were measured. Ages and growth rates were determined based on back-calculations from scales. Gonad samples were preserved in Bouin's solution and stained with hematoxylin and eosin. The maturity stage was determined according to the Sakun and Bucka scale (1968), and egg diameter was measured. Four maturity stages were identified: II - oocytes in protoplasmatic growth; III - oocytes in various phases of trophoplasmatic growth (vitellogenesis); IV - oocytes after completion of vitellogenesis with a centrally located nucleus. The gonadosomatic index (GSI) was also determined as the gonad volume of the total fish body weight.

RESULTS

The results of the scale analyses confirmed that the age of the pike caught ranged from 2 to 7 years while that of the pikeperch ranged from 2 to 6 years (Table 1). The growth rate readings indicated that the mean body length of pikeperch from the Tresna Reservoir at ages 1 to 6 were 15.0, 30.5, 38.3, 44.9, 55.3, and 60.0 cm, respectively (Table 2). The largest increase in mean body length was noted in the first two years of

life (15.0 cm), while the smallest was noted between years 6 and 7 (4.7 cm). The analysis of pike growth indicated that in the first year of growth pike reached a mean length of 23.3 cm, while in the seventh year it was 70.0 cm (Table 3). The greatest increase in body length was noted in the first year of life (23.3 cm) and the least in the fourth year of life (4.1 cm).

TABLE 1

Sex ratio (females : males) and number of pike and pikeperch in each age group

Age groups

Species N 2 3 4 5 6 7 Sex

Pikeperch 31 12 9 4 3 3 - 18:13

Pike 32 3 6 7 7 5 4 20:12

TABLE 2

Total length growth rate of pikeperch from different waters

Total length (mm) at age (years)

Basin and author 1 2 3 4 5 6

Tresna 150 305 383 449 553 600

Zemborzyce - Jarzynowa et al. 1990 131 225 308 371 438 504

Dobczyce - Jelonek et al. 2003a 104 214 324 407 468 516

Goczalkowice - Kolder 1969 127 222 324 411 476 519

Roznowski - Kolder 1969 116 207 285 363 422 490

Otmuchowski - Kolder 1969 145 242 343 418 497 -

Turawa - Nagi^c 1961 156 292 334 489 538 -

Mean from lakes in north Poland - Nagi^c 1961 146 255 358 438 498 -

Vistula River - Nagi^c 1964 157 251 371 446 502 572

The histological analyses of gonads indicated that the samples caught were comprised of 20 pike females and 12 males, and 18 pikeperch females and 13 males (Table 1). In pike aged 2+ (females only) 80% of the oocytes were in maturity stage II at a mean size of 60 p.m while 20% of them were in maturity stage III. The testicles of the male pike at ages 3 to 7 were in maturity stage III. In females it was confirmed that in the ovaries there were oocytes of a diameter of 60 p.m in maturity stage II, which comprised 64.8% of all the egg cells, as well as oocytes in maturity stage III at a mean diameter of 180 p.m. Among them, five did not spawn and their ovaries were in a state of resorption. The female GSI ranged from 0.4 to 1.4, while that of the males ranged from 1.0 to 1.2.

TABLE 3

Total length growth rate of pike from different waters

Total length (mm) at age (years)

Basin and author 1 2 3 4 5 6 7

Tresna 233 337 422 463 535 593 700

Goczalkowice - Wajdowicz 1965 208 315 425 620 710 - -

Zemborzyce - Jarzynowa et al. 1990 197 328 428 537 632 728 -

Jeziorsko - Heese and Mastynski 1990 192 275 351 420 - - -

Dobczyce - Jelonek et al. 2003b - - 360 445 526 640 748

Orawa - Balon 1965 231 337 426 490 618 664 -

Mean from lakes near W^gorzewo - Antosiak 1961 206 304 388 478 650 - -

Wyzyna Lodzka River - Kopczynska and Penczak 1969 227 264 310 363 403 455 534

The analysis of the histological picture of the pikeperch gonads indicated that ovaries of females ranging in age from 3 to 6 years contained oocytes in maturity stages II, III, and IV. The most abundant were the smallest oocytes (58 p.m) in maturity stage II (mean 80.4%). Oocytes in maturity stage III at a mean size of 130 p.m comprised an average of 17.7% of the total, while the largest oocytes (mean 160 p.m) in maturity stage IV comprised 5.7%. Empty follicular membranes were observed in the histological preparations. The gonadosomatic index of the analyzed pikeperch ranged from 2.4 to 4.4 (females) and from 1.9 to 2.1 (males).

DISCUSSION

Pike and pikeperch are essentially the only obligatory predatory fish species inhabiting the reservoirs of southern Poland. The results of studies by Falkowski (2005, 2006,2007) and Falkowski and Wisniewolski (2003) prove that the share of pikeperch and pike has stabilized in spite of significant stocking efforts. Since both of these species are of interest to anglers and are also key to the proper functioning of fisheries management, it is necessary to study their growth rates. It is also key to analyze the histological pictures of their gonads, since they indicate, among other things, if a given species spawned successfully (Epler and Bieniarz 1979, Epler et al. 1996, Epler et al. 2005).

The growth rates of pikeperch from the Tresna Reservoir were slightly higher than those of this species in most other dam reservoirs (Table 2), especially in the fifth and sixth years of life in the Roznow (Kolder 1969), Goczalkowice (Kolder 1969), and

Dobczyce (Jelonek et al. 2003b) reservoirs. The mean pikeperch body length in the Tresna Reservoir was higher in each year of life than the mean from many other lakes in northern Poland (Nagi^c 1961) and equal to the growth of pikeperch in the Vistula River (Nagi^c 1964).

The pikeperch sample from the Tresna Reservoir analyzed during the current study was comprised of 18 females and 13 males. The ovaries were dominated by oocytes in the protoplasmatic growth stage (mean 80%), which is characteristic of maturity stage II and is the beginning of ovary preparation for the subsequent spawning season (Sakun and Bucka 1968); oocytes in the process of vitellogenesis (mean 17.7%) that are characteristic of maturity stage III; and oocytes in the final phases of vitellogenesis that belong to maturity stage IV, but at the beginning of this phase when the egg cell nucleus (embryonic sac) is located in the center of the cell (Bieniarz and Epler 1991, Epler and Sokolowska-Mikolajczyk 2007). The histological pictures of the ovaries were similar in all of the female year classes. Empty follicular membranes were in the resorption process which signaled that the fish had spawned at the appropriate time. The lack of females with ovaries in the state of resorption indicated that pikeperch spawning in Tresna Reservoir had been successful. The testicles of all the males were in maturity stage III, which denotes intense spermatogenesis and involves the processes of the growth, maturity, and formation of the male germ cells (Sakun and Bucka 1968).

The growth rate of pike in the Tresna Reservoir was close to that of this same species in other dam reservoirs (Balon 1965, Wajdowicz 1965, Jarzynowa et al. 1990, Jelonek et al. 2003a, b). Lower growth rates were noted in pike from Jeziorsko Reservoir (Heese and Mastynski 1990) and other lakes in northern Poland (Antosiak 1961). Substantially lower growth rates were noted in pike from the rivers in Central Poland (Kopczynska and Penczak 1969, after Zalachowski 2000) in comparison to the fish from the Tresna Reservoir. Differences in mean body length were especially apparent between the fourth and eighth years of life (Table 3).

The histological picture of ovaries in year class 2 pike females indicated that 80% of the oocytes were in the protoplasmatic phase, and 20% were in the vacuolization phase, which is considered to be the first stage of vitellogenesis (endogenic vitellogenesis) still prior to the incorporation of the yolk (stage III). This indicates the second stage of maturity, and the small percentage of oocytes in the beginning of vacuolization indicates that the ovary building process for the first spawning had begun (Bieniarz and Epler 1991).

Fish in age classes from 3 to 7 exhibited a majority of oocytes in protoplastic growth stage that is indicative of maturity stage II (mean 64.8%), and a mean of 35.2% oocytes in maturity stage III at the initial period of vitellogenesis, which is evidence of the rebuilding of the ovary following the most recent spawning. Although no empty follicular membranes were observed (it had been about four months since spawning), it is a fact that five females (two of which were from year class 3) had ovaries in the resorption state. This indicates that spawning was not entirely successful, which might have been related to the lack of appropriate spawning substrate or the large fluctuations in the water level in the reservoir. The testicles of the pike from age classes 3 to 7 did not differ with regard to the maturity stage and all were in stage III.

The data presented clearly indicates that pikeperch have good conditions for growth and spawning in Tresna Reservoir, but while those for pike growth are good, they are only moderately good for spawning. Both of these species can be supported by stocking and are valuable components of the ichthyofauna of the Tresna Reservoir.

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Received - 20 August 2007

Accepted - 22 November 2007

STRESZCZENIE

TEMPO WZROSTU ORAZ OBRAZ HISTOLOGICZNY GONAD SZCZUPAKA, ESOX LUCIUS L. I SANDACZA, SANDER LUCIOPERCA (L.) ZE ZBIORNIKA ZAPOROWEGO TRESNA (JEZIORO ZYWIECKIE)

Celem badan bylo okreslenie tempa wzrostu sandacza, Sander lucioperca (L.) i szczupaka, Esox lucius L. ze zbiornika zaporowego Tresna. Wiek ryb okreslono metodq odczytow wstecznych. Na podsta-wie analizy histologicznejgonad okreslono sukces tarlowy porownywanych gatunkow. Material badawczy stanowilo 18 samic i 13 samcow sandacza oraz 20 samic i 12 samcow szczupaka (tab. 1). Tempo wzrostu sandacza w zbiorniku Tresna bylo wyzsze w porownaniu z populacjami zyjqcymi w innych akwenach w Polsce (tab. 2). Analiza histologiczna gonad wskazuje na sukces tarlowy sandacza w zbiorniku. Tempo wzrostu szczupaka w zbiorniku Tresna jest porownywalne z tempem wzrostu tych ryb w innych akwenach (tab. 3), natomiast obraz histologiczny jajnikow wskazywal na cz^sciowy sukces tarlowy, gdyz 25% samic nie przystqpilo do rozrodu i ikra znajdowala si^ w stanie resorpq'i.