Electronic Journal of Polish Agricultural Universities (EJPAU) founded by all Polish Agriculture Universities presents original papers and review articles relevant to all aspects of agricultural sciences. It is target for persons working both in science and industry,regulatory agencies or teaching in agricultural sector. Covered by IFIS Publishing (Food Science and Technology Abstracts), ELSEVIER Science - Food Science and Technology Program, CAS USA (Chemical Abstracts), CABI Publishing UK and ALPSP (Association of Learned and Professional Society Publisher - full membership). Presented in the Master List of Thomson ISI.
2006
Volume 9
Issue 3
Topic:
Fisheries
ELECTRONIC
JOURNAL OF
POLISH
AGRICULTURAL
UNIVERSITIES
Skrzypczak A. , Mamcarz A. 2006. OCCURRENCE OF VENDACE, COREGONUS ALBULA (L.), AND ITS HABITATS IN NORTHEASTERN POLAND IN 1951-1994, EJPAU 9(3), #22.
Available Online: http://www.ejpau.media.pl/volume9/issue3/art-22.html

OCCURRENCE OF VENDACE, COREGONUS ALBULA (L.), AND ITS HABITATS IN NORTHEASTERN POLAND IN 1951-1994

Andrzej Skrzypczak, Andrzej Mamcarz
Department of Lake and River Fisheries, University of Warmia and Mazury in Olsztyn, Poland

 

ABSTRACT

Vendace habitats in northeastern Poland has been carried out on the basis of commercial fish catches from 1951 to 1994. The occurrence of this fish, in various time periods and in different abundance, was confirmed in 463 lakes that covered a total area of over 106.1 thousand hectares. Based on the frequency of vendace occurrence in catches, the lakes were divided into three categories. For each category, the time-related dynamics in the number of lakes populated by vendace was described, and the relevant trend lines were plotted. Within the three categories of the habitats examined, some statistically significant differences were demonstrated between such parameters as maximum and mean depth, depth index and the percentage of the lake area occupied by pelagic waters. Vendace lived for the longest time-periods in habitats which are called vendace lakes because of their morphometric parameters. The migration of this fish species was observed. The most dynamic growth in the number of lakes where vendace was commercially exploited took place in the 1960s and 1970s. Against the background of intensive stocking operations vendace appeared, usually brief , in water bodies rather different in their morphometric parameters from vendace lakes.

Key words: Coregonus albula, habitat, lakes, northeastern Poland, occurrence, vendace.

INTRODUCTION

Vendace, Coregonus albula L., referred to as a post-glacial relic, appeared after the recession of the Baltic glacial. In Poland, until 1956, vendace lived in its natural habitats, delineated by the southern border of the last Baltic glaciers. Today, because of introductions, vendace is found in water bodies located outside this area [5].

A few publications from the late 19th century and early 20th century described the introduction of vendace and its appearance and disappearance in many habitats inside its natural distribution range in Poland [2]. Just before the fisheries economy in Poland commenced, a precise picture of the distribution of vendace in northwestern and northeastern Poland was presented by Bernatowicz [2], Radziej [22] and Walczak [28].

In the early 1950s vendace, which is an economically and commercially valuable species, became an object of intensive management practices [1]. In this period vendace habitats comprised in approximately 36% of the total area of the Polish lakes [5]. Numerous introductions and increasing catches of vendace were reported. In the early 1950s the mean annually catches of this fish species in Polish lakes reached about 269 tons, whereas ten years later about 422 tons [13]. Several observations were made on the adaptability of vendace to habitats and its capability of living in profundal zones of oxygen-deficient lakes during the summer stagnation season [4, 27]. While the vendace economy was on the increase, several exploitation analyses [9, 14, 26] were conducted along with the research and observations on the biology of this fish species. The fecundity of vendace [33], survival and mortality in its eggs at spawning grounds [34], and growth of selected populations of this fish species in Poland [8] has been studied. Univariate time series analyses indicated disappearance of coregonid fishes and the overall decrease of fish species number [18]. Facing some changes in the natural environment, including progressing eutrophication of lakes, researchers reported on decreasing efficiency of vendace stockings and natural spawning as well as declining catches of the fish in commercially exploited lakes [30, 31]. Trends of stockings and catches as well as effectiveness of stocking with vendace were determined for selected groups of Polish lakes [16]. Bnińska and Wołos [7] and Bnińska [6] reported that increased lake trophy resulted in lower effectiveness of stocking in terms of the number of vendace larvae needed to produce 1 kg of commercial catch.

The objectives of this study were to analyse time-related changes in the distribution of vendace within the analysed area against the background of the intensive fishing economy of this species, and to characterise habitats settled by vendace in 1951-1994.

MATERIALS AND METHOD

Northeastern Poland is a region characterized by the largest total area of lakes in the country [12]. Its borderlines are delineated by the Lower Vistula River to the west, the last Baltic glaciation to the south and the state borders to the east and north (Fig. 1). The total number of water bodies of an area over 10 ha in the territory covered by the present research project is 1003, and their aggregated surface area is 132.45 thousand ha. The contribution of lakes area (>10 ha) to river drainage area of northeastern Poland is diverse and it range from 1.4 to 16.9% at a mean value of 7.2% (±4.6) [10, 11].

Fig. 1. The area of northeastern Poland covered by the study on the occurrence of vendace and characterization of its habitats in 1951-1994

The source material for the study was commercial fish catch data. Based on the records in the management books for the lakes of northeastern Poland [20], made in 1951-1994, the authors selected a group of reservoirs in which vendace occurred in fishing statistics or which were stocked with this fish species. The changes which occurred in the ownership and management structure of lakes and fish farms in Poland after the year 1994 have made any further continuation of the analysis extremely difficult. The lakes were assigned an appropriate category as vendace habitat according to the frequency of occurrence of this fish species in the commercial catches. This index was expressed as a ratio between the number of years when vendace was present in catches to the total number of the years when exploitation was carried out. The index served to divide the lakes into three categories of vendace habitats: A (≥0.75) – considered as permanent in character, B (0.74-0.25) – considered as temporary and C (<0.25) – considered as incidental.

The morphologic and morphometric parameters of the analysed lakes came from morphometric cards prepared from the data provided by the Inland Fisheries Institute in Olsztyn. Mean depth, depth index (a ratio of the mean depth in meters to the maximal depth in meters), relative depth (a ratio of maximal depth in meters to the square root of the area in hectares) and shore development (a ratio of shore line length in meters to the double value of a square root of the quotient of π value by lake area in hectares) are generally accepted parameters which characterise the water bodies [25]. The size of the pelagic zone was determined relative to the 5.0 meter depth contour. The size parameters of Sniardwy Lake (the largest Polish lake – 9975.4 ha without the bays) and the depth of Hańcza Lake (the deepest Polish lake –108.5 m) were excluded from the analysis of vendace habitat characteristics due to their outlying values.

For basic calculations, descriptive statistics were used, such as arithmetic mean, standard deviation (SD), and standard error of the mean (SE). To analyse potential differences in the parameters describing vendace habitats, analysis of variance (ANOVA) and post-hoc comparison of means (T-Tukey test) were performed. Groups of variables were pre-tested in order to check whether they fulfilled the basic requirements of ANOVA tests and were therefore applicable to perform certain statistical analyses (Leven’s test, Brown and Forsythe’s test, W Shapiro-Wilk’s test) [23]. The significance of the results and analyses was determined at the level of significance α=0.05

Approximation of time-related changes in the occurrence of vendace in commercial catches was done with a cubic polynomial function. The values of the R-squared determination coefficient were treated as a trend line adjustment measure [24].

RESULTS

Vendace was present, at one time or another, in 463 lakes in northeastern Poland between 1951 and 1994 that covered the total area of 106.1 thousand ha. In total, 122 lakes with an aggregated surface area of 66 642 ha were classified as permanent habitats (category A). Category B (temporary habitats) was represented by 109 lakes with a total area of 14 836 ha. Sporadic and incidental occurrence of vendace were recorded in 232 lakes that were rated as category C. Their total area was 24 631 ha. The mean (±SD) of the frequency of vendace occurrence in commercial catches in category A, B and C habitats was 0.92 (±0.07), 0.49 (±0.14) and 0.08 (±0.06), respectively.

Analysis of morphometric and morphological characteristics of the lakes showed statistically significant differences within all the analysed parameters between category A and C habitats (Table 1). For most of the parameters (except relative depth) the differences were highly significant (P<0.0001). For maximal and mean depth, depth index and share of the pelagic zone statistically significant differences were found between all the three habitat categories. Between the permanent (category A) and temporary habitats (category B) no statistically significant differences were observed for the relative depth only.

Table 1. Results of comparisons of the morphometric traits of vendace habitats (categories A, B, C – see Materials and Methods) in northeastern Poland in 1951-1994 (mean±SE). Critical value F=3.02 (df 2; 301-460; a=0.05). All the test statistics values (F-ratio) are statistically significant (P<0.05). Mean values with different letter superscripts (in the same line) are statistically different (P<0.05)

Parameters

F-ratio

Category of vendace habitats

A

B

C

Lake area (ha)

45.92

466.18a ± 47.87

136.11b ± 24.91

106.17b ± 16.43

Pelagic zone area (ha)

44.87

361.81a ± 39.60

111.38b ± 32.19

47.43b ± 11.38

Share of pelagic zone (%)

128.07

68.71a ± 0.91

57.72b ± 2.00

30.04c ± 1.93

Maximal depth (m)

230.49

34.56a ± 1.06

21.68b ± 0.94

11.97c ± 0.49

Mean depth (m)

199.47

10.30a ± 0.28

7.01b ± 0.26

4.44c ± 0.15

Depth index

26.48

0.31a ± 0.01

0.35b ± 0.01

0.40c ± 0.01

Relative depth

11.95

0.02a ± 0.00

0.02a ± 0.00

0.01b ± 0.00

Shore development

22.85

2.45a ± 0.08

2.02b ± 0.07

1.85b ± 0.05

In 1951-1994 the number of lakes in northeastern Poland where vendace was caught fluctuated. The biggest rise in the number of vendace habitats was seen within category B lakes, where an increasing tendency continued until the end of the 1970s (Fig. 2). Similar events, albeit less dynamic and durable, occurred within the group of permanent (category A) and incidental habitats (category C). The highest number of lakes with exploited vendace populations occurred in 1978 – in total, 249 lakes. In subsequent years, the number of water bodies where vendace was fished began to decline systematically, with the decrease becoming more rapid in the late 1980s. In 1993–1994 the presence of vendace was recorded in 173 of the analysed lakes. Regression equations and determination coefficients for the plotted curves are presented in Table 2. The highest degree of adjustment was seen for the line depicting the trend of vendace occurrence in category B lakes (R2 = 0.944).

Fig. 2. Occurrence of vendace in commercial catches from lakes (categories A, B, C – see Materials and Methods) in northeastern Poland in the years 1951-1994

Table 2. Regression equation coefficients (Y=ax3+bx2+cx+d) and determination coefficients (R2) in the 3-degree polynomial adjustment of trends lines approximating the relationship between occurrence of vendace in fishery catch (Y) of exploited lakes categories A, B, C (see Materials and Methods) and time (x) for northeastern Polish lakes in 1951-1994

Category of
vendace habitats

R2

Equation coefficient

a

b

c

d

A

0.836

0.0006

-0.0873

3.0312

67.6370

B

0.944

-0.0035

0.1515

0.6518

10.7330

C

0.541

-0.0006

0.0251

0.0478

3.2945

In the early years of the analysed time period, vendace was present in 110 lakes in northeastern Poland. The lakes covered a total area of about 58.1 thousand ha (Table 3). The greatest number of vendace habitats was found in category A lakes- 89 lakes (55 843 ha). Vendace stocking was carried out in all these lakes. In most of the habitats (82%) stocking was undertaken in the first 11 years of the analysed time period. Among the temporary and incidental habitats (categories B and C) vendace was found in 21 lakes.

Table 3. Distribution of vendace populations in lakes (categories A, B, C – see Materials and Methods) of northeastern Poland in 1951, with the time distribution of the first stocking treatments

Specification

Category of vendace habitats

A

B

C

No.
of lakes

lake area

No.
of lakes

lake area

No.
of lakes

lake area

ha

%

ha

%

ha

%

Total

89

55 843

83.8

15

1998

13.5

6

242

1.0

Non-stocked lakes

-

-

0.0

5

917

6.2

3

45

0.2

First stocking

1951-1961

73

40 520

60.8

8

727

4.9

1

30

0.1

1962-1972

14

14 973

22.5

2

354

2.4

-

-

0.0

1973-1983

2

350

0.5

-

-

0.0

-

-

0.0

1984-1994

-

-

0.0

-

-

0.0

2

167

0.7

While analysing the records, we found that vendace appeared in 353 lakes of the total area of 48 026 ha (Table 4) after 1951. The permanent (category A) and temporary (category B) habitats are worth special attention. These were 33 and 94 lakes, respectively, with a total area of 23.6 thousand ha. In the category A and B lakes, the majority of new habitats appeared before 1961, and consisted of 76 lakes, of which the first vendace catch was not preceded by immediate stocking in 35 documented cases. Until the end of the analysed time period, stocking was performed in all category A lakes, and in the vast majority of category B lakes (82 out of 94). The occurrence of vendace in incidental habitats (category C) was most frequently recorded in 1962-1972, when this fish species was observed in 89 lakes. Among all the 226 lakes in this group of habitats, only 37 (16%) could, at least theoretically, have been associated with fish stockings.

Table 4. Increasing distribution of vendace and time analysis of the first stocking in habitats (categories A, B, C – see Materials and Methods) of northeastern Poland settled after 1951 (BS – first catch before first stocking, AS – first catch after first stocking)

Specification

Category of vendace habitats

A

B

C

No.
of lakes

lake area

No.
of lakes

lake area

No.
of lakes

lake area

ha

%

ha

%

ha

%

Total

33

10 799

16.2

94

12 838

86.5

226

24 389

99.0

first catch

1951-1961

BS

8

3452

5.2

27

3176

21.4

51

7270

29.5

AS

24

7161

10.7

17

4834

32.5

7

433

1.8

1962-1972

BS

-

-

0.0

17

1926

13.0

75

6454

26.2

AS

1

186

0.3

24

2379

16.0

14

894

3.6

1973-1983

BS

-

-

0.0

3

142

1.0

47

6217

25.2

AS

-

-

0.0

6

381

2.6

9

780

3.2

1984-1994

BS

-

-

0.0

-

-

0.0

16

1996

8.1

AS

-

-

0.0

-

-

0.0

7

345

1.4

Non-stocked lakes

-

-

0.0

12

1029

6.9

165

18 457

74.9

first stocking

1951-1961

29

8032

12.1

29

6235

42.0

17

1056

4.3

1962-1972

4

2767

4.1

32

3840

25.9

13

1696

6.9

1973-1983

-

-

0.0

11

1242

8.4

22

2667

10.8

1984-1994

-

-

0.0

10

492

3.3

9

513

2.1

In the analysed northeastern polish lakes, the number of lakes stocked with vendace varied from 102 in 1987 to 20 in 1994 (Fig. 3). Since 1951, when numerous fluctuations were observed, the number of lakes stocked with vendace annually was on the increase, to eventually reach the average value of 86 (±12) in 1977-1987. Stockings prevailed in category A lakes, of which 64 (±5) on average were stocked every year in this period. From 1988 to 1994 a decrease in the number of vendace stocked lakes was seen in all lake categories.

Fig. 3. Number of lakes (categories A, B, C – see Materials and Methods) in northeastern Poland stocked with vendace in 1951-1994

DISCUSSION

For the zoogeographic distribution of vendace in northeastern Poland in 1951-1994, lakes classified as categories A and B habitats played the most important role. This conclusion is confirmed by the duration of time periods when this fish species occurred in commercial catches, irrespective of its abundance. There is probably an error margin regarding the total number of lakes settled by vendace in this part of Poland. There could have been a small percentage of lakes in which vendace was not commercially exploited due to the small size of its populations. This phenomenon was reported by Bernatowicz [2], who studied the post-war distribution of vendace in the Masurian and Suwałki Lake Districts. It can also be assumed that as the fisheries economy began to develop in the 1950s, the number of unexploited populations was marginalised. Vendace was then introduced to lakes in order to obtain good production output via exploitation.

The area studied by Bernatowicz [2] together with that analysed by Radziej [22] covered the territory of northeastern Poland, and the results obtained by these two researchers could serve as a background for the considerations on vendace distribution in this paper. According to these two authors, there were 132 lakes in northeastern Poland with a total area of 67 858 ha that had vendace populations in the early 1950s. This figure is higher by 22 water bodies than the number determined in the present analysis. It may, therefore, be speculated that these were lakes with unexploited populations, identified on the basis of oral reports [2]. Quite large discrepancies in the total area of the lakes with vendace populations, which equal 9775 ha, can originate from differences in the data from various sources that were used to asses the total area in the 1950s and in the present paper.

The initial number of vendace habitats in the present report should not be considered as indicative of the lakes with autochthonous populations. Some of the lakes were stocked with this fish species between 1946 and 1950 and, according to the German sources, some stockings had been carried out earlier than that [2, 22]. At the same time, there were reports suggesting that vendace was disappearing from many habitats in the first half of the 20th century. Bernatowicz [2] analysed the available data documenting the years 1923-1951 and concluded that vendace had retreated from at least 18 lakes of the Masurian Lake District. According to the same author, the disappearance of this fish species during those years was connected with progressing eutrophication and land reclamation works, which were conducted after 1850, especially in the area of the Masurian Lake District. As a result, the water table in many lakes went down, in some cases by several meters.

The insufficient lake management with vendace led to more intense stockings with this fish species in the mid-1950s, although the results of the stockings were reported as unsatisfactory [3]. This paper examined the effects of those stockings in about 80 lakes in northeastern Poland, stocked with vendace in 1952-1953.

In the late 1950s and in the 1960s, the number of lakes in different parts of Poland where vendace was fished was increasing. In Poland, according to data in Bernatowicz [2], Radziej [22] and Walczak [28], vendace was present between 1950 and 1957 in 244 lakes with a total area of 100 758 ha. It was nearly 36% of the total area of the Polish lakes [5]. Marciak [19] demonstrated that in 1970 vendace was present in 379 Polish lakes with a total area of 119 621 ha. In the mid-1970s vendace was fished in 420 Polish lakes with a total area of 126 985 ha [5]. It was taken for granted that an increase in the distribution range of vendace was predominantly associated with vendace stockings [14]. The analysis of the commercial fisheries records completed for this study has shown that among category A and B habitats (in which vendace appeared after 1951), 55 lakes (43%) were the water bodies in which vendace had occurred prior to the first stocking. Among category C lakes, in which vendace appeared rather sporadically in the fish catches, the percentage of such cases was nearly 84% (189 lakes). Typically, small amounts of vendace fish were caught then, so the fishing efficiency was expressed in the order of hundredths or tenths of 1 kg ha-1, and stocking was usually undertaken after catching vendace specimens. These facts suggest that the species is able to migrate between water basins, and the scale of vendace migration excludes the theory of erroneous records in commercial fisheries books or that such records were made carelessly.

Migratory journeys of vendace have seldom been taken into consideration when analysing fluctuations in the distribution of this species. For example, the appearance of vendace in Niegocin Lake in the 1930s, after the fish had disappeared from that lake at the turn of the 19th and 20th centuries, was explained by migration of vendace from Lake Jagodne [32]. Both lakes lie in the complex of the Great Masurian Lakes. There have also been reports on disappearance of this fish species and its subsequent reappearance without artificial stocking owing to improved water quality [21, 31], an event which by some authors is referred to as ‘self-renewal’ of a species [3].

For many years it was thought that vendace lakes should be clean, deep, large in surface area, cold and well oxygenated, with large epilimnion – this is how such lakes were described in the lake typology [25]. Opinions on the high environmental requirements of vendace were modified gradually as autochthonous occurrence of vendace in small and eutrophic lakes without thermal layers had been documented [5]. Marciak [19] demonstrated that nearly 28% of the total area of the lakes in which vendace was caught in Poland consisted of eutrophic lakes in the early 1970s. The presence of vendance on a commercial scale was also observed in ponds and dystrophic lakes [14]. The analysis of the morphometric characteristics and parameters for each lake category of vendace habitats accomplished in the present study shows distinct preferences of this fish species. It needs to be assumed that the possible presence of autochthonous vendace populations could be associated only with category A lakes. The characteristics of this group of lakes show closer convergence with the morphology of vendace lakes in the fisheries typology.

The range of epi- and metalimnion, the extent of the pelagial zone and its trophic potential are the primary decisive components for vendace to appear in a given lake [3]. Furthermore, studies on the effect of some morphometric characteristics of lakes (total area, maximal and mean depth and shore development) on vendace economy efficiency (mean yield and mean stocking) showed that the latter is most strongly dependent on the parameter of lake depth [17]. The characteristics of the lakes inhabited by vendace populations for the longest time periods in the years 1951-1994 (categories A and B) are largely congruent with the above statement. Furthermore, some statistically significant differences with category C habitats occurred for most of the analysed parameters.

A dynamic growth in the number of vendace habitats in northeastern Poland has been recorded since the end of the 1970s. The decline in the number of lakes settled by this fish species noticed in the early 1980s shows much convergence with the tendency towards decreased efficiency in vendace catches in a group of 60 lakes reported by Leopold and Wołos [16]. In another study a decreasing trend in vendace catches was observed in the earlier years. In the complex of Sniardwy and Mamry Lakes (the Great Masurian Lakes) such a declining tendency became evident in the mid-1970s, and in the complex comprising Niegocin Lake – a few years before that [18].

A decrease in the number of vendace habitats was most probably caused by a change in the fish stocking policy. The relationship between vendace catches and stocking has been demonstrated on many occasions [16]. In addition to that, the decline in vendace catches observed throughout Poland since 1985 was associated by Wołos and Bnińska [31] with changes in the ownership structure, small stockings, and the restructuring of fish assemblages. Some researchers have also reported cases of vendace introduction or maintenance of existing populations of this fish in water bodies by stocking as well as a complete disappearance of vendace when stocking was discontinued [29].

A decrease in the number of vendace habitats noticed in the present study became apparent earlier than a decline in the total number of stocked lakes. This can be somehow related to the decrease in the efficiency of vendace catches observed by Leopold and Wołos [16], which frequently coincided with a tendency of increasing the amounts of stocking material introduced (individuals ha-1) accompanied by decreasing efficiency of stockings. Progressing eutrophication can be blamed for this because, as shown by Bnińska and Wołos [7], the efficiency of fish stocking (number of larvae per kg-1 catch of vendace) with this species declines while the trophy of a lake measured as the content of chlorophyll in surface layers of water increases. The decline in vendace management in the 1980s was in many cases caused by a small frequency of stocking and excessive amounts of larval stocking material [15].

CONCLUSIONS

  1. In the years 1951-1994 vendace lived for the longest time-periods in habitats which, in the fishery typology, are called vendace lakes because of their morphometric parameters. At the same time, those lakes were most often stocked with vendace.

  2. Against the background of intensive vendace stocking operations in the lakes of northeastern Poland, the migration of this fish species was observed, accompanied by its appearance, usually brief, in water bodies rather different in their morphometric parameters from vendace lakes.

  3. The most dynamic growth in the number of lakes where vendace was commercially exploited took place in the 1960s and 1970s.


REFERENCES

  1. Bernatowicz S., 1953a. Występowanie i przyrost sielawy jezior mazurskich na tle warunków srodowiska [Distribution and growth of the small whitefish (Coregonus albula L.) in Mazurian Lakes on the background of the environmental conditions]. Rocz. Nauk Rol. 67-B-1, 1-20 [in Polish].

  2. Bernatowicz S., 1953b. Aktualny stan występowania sielawy (Coregonus albula L.) na Pojezierzu Mazurskim i Suwalszczyznie [The actual state of distribution of the small whitefish (Coregonus albula L.) in the lakes of the Mazurian and Suwałki districts]. Rocz. Nauk Rol. 67-B-1, 61-80 [in Polish].

  3. Bernatowicz S., 1955. Zagospodarowanie sieją i sielawą jezior Pojezierza Mazurskiego [Whitefish and vendace management in lakes of the Masurian Lakeland]. Gospod. Ryb. 6, 1-3 [in Polish].

  4. Bernatowicz S., 1960. Obserwacje nad wsiedlaniem sielawy do jeziora z wysokim pułapem siarkowodoru [Observations on stocking lakes with a high hydrogen sulphide ceiling with ablen (Coregonus albula L.)]. Rocz. Nauk Rol. 75-B-2, 273-282 [in Polish].

  5. Bernatowicz S., Dembinski W., Radziej J., 1975. Sielawa [Vendace]. PWRiL, Warszawa, [in Polish].

  6. Bnińska M., 2000. Commercial fisheries versus water quality in lakes with special reference to coregonid management. Fish. Manage. Ecol. 7, 105-114.

  7. Bnińska M., Wołos A., 1998. Effectiveness of coregonid management versus environment quality. Arch. Pol. Fish. 6 (2), 295-314.

  8. Christianus J., 1995. Age and growth of selected vendace (Coregonus albula L.) populations in Poland. Arch. Hydrobiol. Spec. Issues Advanc. Limnol. 46, 97-102.

  9. Dabrowski B., Leopold M., 1969. Analiza eksploatacji sielawy w jeziorach Polski [Analysis of Coregonus albula L. exploitation in Polish lakes]. Rocz. Nauk Rol. 91-H-1, 59-74 [in Polish].

  10. Jańczak J., 1997. Atlas jezior Polski. Tom II. Jeziora zlewni rzek Przymorza I dorzecza dolnej Wisły [Atlas of Polish lakes. Vol II. Lakes of the river catchments in the Pomerania region and the lower river basin of the Vistula]. Bogucki Wyd. Nauk., Poznan, [in Polish].

  11. Jańczak J., 1999. Atlas jezior Polski. Tom III. Jeziora Pojezierza Mazurskiego i Polski południowej [Atlas of Polish lakes. Vol III. Lakes of the Masurian Lake District and southern Poland]. Bogucki Wyd. Nauk., Poznan, [in Polish].

  12. Kostrowicki J., 1961. Srodowisko geograficzne Polski [The geographical environment of Poland]. PWN, Warszawa, [in Polish].

  13. Leopold M., 1970. Znaczenie gospodarcze sielawy (w: Zagospodarowanie jezior sielawa. Częsc I) [The economic significance of vendace (in: Vendace management in lakes. Part I)]. Inland Fisheries Institute, Olsztyn, Broszura 39, 3-8 [in Polish].

  14. Leopold M., 1972. Metodyka prognozy i oceny połów ryb o krótkim cyklu życiowym w jeziorach polskich (na przykładzie sielawy – Coregonus albula L.) [Methodology of forecasting and evaluating catches of fishes with short lifetime in the Polish lakes (on the example of Coregonus albula L.)]. Rocz. Nauk Rol. 94-H-4, 9-98 [in Polish].

  15. Leopold M., Wołos A., 1998a. Effectiveness of vendace stockings as affected by stocking frequencies. Arch. Pol. Fish. 6 (2), 287-293.

  16. Leopold M., Wołos A., 1998b. Regularities of vendace management and methodical aspects of its assessment on long-term basis. Arch. Pol. Fish. 6 (2), 329-344.

  17. Leopold M., Wołos A., Mickiewicz M., 1998. The effect of lake morphometry on the effectiveness of vendace management. Arch Pol. Fish. 6 (2), 279-286.

  18. Mamcarz A., Skrzypczak A., 2002. Coregonids in the Great Masurian Lakes. Arch. Hydrobiol. Spec. Issues Advanc. Limnol. 57, 157-169.

  19. Marciak Z., 1970. Podstawa przyrodnicza gospodarki sielawowej (w: Zagospodaro-wanie jezior sielawą. Częsc II) [Biological base of the vendace economy (in: Vendace management in lakes. Part II)]. Inland Fisheries Institute, Olsztyn, Broszura 39, 8-14 [in Polish].

  20. Nagięć M., 1978. Dynamika intensywnie eksploatowanej populacji sandacza w jeziorze Jeziorak [Dynamic of intensive exploited pikeperch (Stizostedion lucioperca) population in Lake Jeziorak]. Zesz. Nauk. ART Olszt. Ochr. Wód i Ryb. Sród. 8, 119-176 [in Polish].

  21. Pietrucha M., 1999. Powrót siejowatych (Coregonus Lavaretus Maraena B. and Coregonus albula L.) do jeziora Miedwie [Return of coregonid fishes (Coregonus lavaretus maraena B. and Coregonus albula L.) to Lake Miedwie]. Kom. Ryb. 3, 14-19 [in Polish].

  22. Radziej J., 1960. Występowanie sielawy w jeziorach obszaru przyległego do prawego brzegu Dolnej Wisły [The occurrence of ablen (Coregonus albula L.) in lakes of the area neighboring with the right bank of the Lower Vistula]. Rocz. Nauk Rol. 75-B-2, 223-235 [in Polish].

  23. Statistica, 1997a. STATISTICA PL dla Windows (Tom I): Ogólne konwencje I statystyki I [Statistica for Windows (Volume I): General Conventions and Statistics]. StatSoft Polska, Cracow, 1001-1878 [Polish Ed.].

  24. Statistica, 1997b. STATISTICA PL dla Windows (Tom II): Grafika [Statistica for Windows (Volume II): Graphics]. StatSoft Polska, Cracow, 2001-2982 [Polish Ed.].

  25. Szczerbowski J.A., 1995. Inland fisheries in Poland. Wyd. IRS, Olsztyn.

  26. Turkowski K., Bonar A., 1995. Effects of species composition and stocking on commercial catches of vendace, Coregonus albula (L.), in Ostroda lakes (northern Poland). Arch. Hydrobiol. Spec. Issues Advanc. Limnol. 46, 397-403.

  27. Walczak J., 1953. Sielawa (Coregonus albula L.) kilku jezior Pomorza Zachodniego [The small whitefish (Coregonus albula L.) of several western Pommerania Lakes]. Rocz. Nauk Rol. 67-B-1, 21-37 [in Polish].

  28. Walczak J., 1956. Występowanie sielawy (Coregonus albula) w jeziorach północno-zachodniej Polski [The occurrence of ablen (Coregonus albula L.) in the lakes of north-western Poland]. Rocz. Nauk Rol. 71-B-1, 21-50 [in Polish].

  29. Wołos A., 1994. Efektywnosc zarybień koregonidami. (w: Aktualne problemy rybactwa jeziorowego) [Effectiveness of coregonid stockings. (in: The current problems of lakes fisheries)]. Ed. A. Wołos Wyd. IRS, Olsztyn, 79-93 [in Polish].

  30. Wołos A., 1998. General characteristics of coregonid management in 132 Polish lakes. Arch. Pol. Fish. 6 (2), 265-278.

  31. Wołos A., Bnińska M., 1998. Effectiveness of coregonid management on the backgro-und of fish yield changes in 25 Polish lakes. Arch. Pol. Fish. 6 (2), 315-328.

  32. Zachwieja J., 1966. Snięcie sielawy w jeziorze Niegocin [Vendace mortality in Lake Niegocin]. Gospod. Ryb. 6, 16-18 [in Polish].

  33. Zawisza J., Backiel T., 1970. Płodnosc sielawy (w: Zagospodarowanie jezior sielawa. Częsc II) [Fecundity of vendace (in: Vendace management in lakes. Part II)]. Inland Fisheries Institute, Olsztyn, Broszura 40, 8-19 [in Polish].

  34. Żuromska H., 1970. Przeżywalnosc i ważniejsze przyczyny smiertelnosci jaj sielawy na tarliskach (w: Zagospodarowanie jezior sielawa. Częsc II) [Survival and some more important causes of mortality in vendace eggs at spawning grounds (in: Vendace management in lakes. Part II)]. Inland Fisheries Institute, Olsztyn, Broszura 40, 3-8 [in Polish].

 

Accepted for print: 27.09.2006


Andrzej Skrzypczak
Department of Lake and River Fisheries,
University of Warmia and Mazury in Olsztyn, Poland
M. Oczapowskiego 5, 10-957 Olsztyn, Poland
phone +48 89 523 33 88,
fax +48 89 523 39 69
email: sandacz@uwm.edu.pl

Andrzej Mamcarz
Department of Lake and River Fisheries,
University of Warmia and Mazury in Olsztyn, Poland
M. Oczapowskiego 5, 10-957 Olsztyn, Poland
phone +48 89 523 33 88,
fax +48 89 523 39 69
email: mamcarz@uwm.edu.pl

Responses to this article, comments are invited and should be submitted within three months of the publication of the article. If accepted for publication, they will be published in the chapter headed 'Discussions' and hyperlinked to the article.