Are there one or two stocks of Scoranza bleak - Alburnus scoranza Bonaparte, 1845 in Lake Skadar (Montenegro) - Research Article
←
→
Page content transcription
If your browser does not render page correctly, please read the page content below
Ecologica Montenegrina 40: 80-92 (2021) This journal is available online at: www.biotaxa.org/em http://dx.doi.org/10.37828/em.2021.40.7 Are there one or two stocks of Scoranza bleak - Alburnus scoranza Bonaparte, 1845 in Lake Skadar (Montenegro) DRAGO MARIĆ1* & KATARINA BURZANOVIĆ2 1Department of Biology, Faculty of Sciences, University of Montenegro, P.O. Box 328, 20000 Podgorica, Montenegro E-mail: dragomrc@yahoo.com 2 Natural History Museum of Montenegro, Trg vojvode Bećir bega Osmanafića 16, 20000 Podgorica, Montenegro. E-mail: kburzanovic@gmail.com *Corresponding author Received 30 January 2021 │ Accepted by V. Pešić: 9 March 2021 │ Published online 15 March 2021. Abstract This paper provides the first comprehensive information on the Length-Weight Relationship (LWR) of Scoranza bleak (Alburnus scoranza) from the Lake Skadar. The results of the study showed that LWR was different in young and older individual fish. We concluded that no single regression would adequately describe the length-weight relationship for Scoranza bleak in the winter period. Small fish, up to one year old, have positive allometric growth whereas older and larger, negative. The results of this study show that the animals grow equally in the same pattern in both localities (Raduš and Karuč) which shows that there are no two stocks as it was assumed in the past. The condition factor in young Scoranza bleaks was lower than in the elderly. Condition factor decreased significantly during the winter period in older specimens. Based on this, we conclude that Scoranza bleak during the winter is poorly fed/starved, which causes a decrease in the condition factor. Analysis of the total sample, of any species, cannot show by what rule the population grows, if infrapopulation variability is present, because the studied value will depend on the number of individual subgroups. If no infra- population variability is found, the required parameter for the entire population can be calculated. In order to determine population variability, multiple groups must be singled out. Preferably, the number of stratified samples should be at least 6 so that correlation-regression analysis can be performed. In stratified samples, the number of individuals should be between 30-40, for any parameter, in order to compare their mean values. The results of the study show that 50 individuals are sufficient for accurate determination of LWR (or and b, is a constant coefficient and b is the slope of the curve.), when it is determined that there is no intrapopulation variability. Key words: variability, length-weight relationship, conditioning factor Raduš, Karuč, Montenegro. Introduction The Scoranza bleak, Alburnus scoranza Bonaparte, 1845, like most species (i.e., carp, nase, goldfish, chub, etc.), belonging to the family Cyprinidae has been intensively studied because of its importance to commerce Ecologica Montenegrina, 40, 2021, 80-92
MARIĆ & BURZANOVIĆ and fisheries (Drecun & Miranović, 1962; Ivanović, 1965; Stein et al. 1975). The Scoranza bleak is endemic to the Southeastern Adriatic Ecoregions (Marić, 2019; Pešić et al., 2020). According to Marić (1995) and Talevski et al. (2009) the Scoranza bleak inhabits only Ohrid – Drim – Skadar sistem. This species is the most economically important species but in five last decades statistically significant decrease in abundance was recorded in Lake Skadar (Marić, 2018). There are a number of papers devoted to the life-history traits, catch, place and method of fishing of A. scoranza (Marić & Kažić, 1990; Burzanović & Marić, 2017). According to Ivanović (1965), the Scoranza bleak in Lake Skadar performs significant migrations – in summer it is dispersed throughout the lake and in winter it migrates to sublacustric springs. It feeds very little in these springs during the winter. Marić & Kažić (1990) showed that the number of Scoranza bleaks is different in sublacustric springs during the winter period, as well as the diversity of other fish species in these springs differs significantly. This affects the choice of fishing gear, fishing time, etc. During the rest of the year, Scoranza bleak is not fishing commercially, because it is scattered throughout the lake (not in a flock), so there is almost no data from that period (except for spawning) because of lack of a comprehensive research. Outside sublacustric springs, larger quantities of Scoranza bleak speciemens can only be caught during migration and spawning periods. Almost all data published on this species were based on the samples collected during autumn and winter, especially from sublacustric springs in which it is collected during the cold period (Drecun & Ristić, 1964; Marić, 2019). From this period (autumn-winter), the growth of Scoranza bleak from several sublacustric springs was studied in the past and it has been showed by Coble & Knežević (1981) that there are two growth patterns, positive allometry and isometry. The latter authors assumed that this was a consequence of the existence of two stocks of this species in Lake Skadar. So far, detailed studies of the length-weight sample of fish species growth from the Skadar Lake basin have not been conducted, and the available data refer either to a small number of specimens or to a particular phase of the life cycle (Milošević & Marić, 2012; Milošević et al., 2012; Marić & Rakočević, 2014). In addition to several applications of weight–length relationships (WLR) in fish biology, knowledge of these relationships is useful for the prediction of the weight from the length values as an indication of the fish condition or for fish stock assessments (Petrakis & Stergiou, 1995; Froese & Pauly, 2006; Vaslet et al., 2008). The importance of WLR has been extensively documented (Froese, 2006). This method requires the length and number of individual fish in situ while the total biomass is determined empirically by applying the established LWR parameters. Length and weight measurements along with age data can provide information on the stock composition, age at maturity, life span, mortality, growth and production (King, 1996; Diaz et al., 2000; Milošević & Marić, 2012; Marić & Rakočević, 2014). The LWR of fishes is useful in assessing the relative well-being of the fish population. It is important in estimating the standing stock biomass, as well as in comparing the ontogeny of fish population from different regions (Petrakis & Stergiou, 1995). Length- weight relationship parameters are often used as an indicator of fatness and general well-being or of gonad development of fish and are useful for between region comparisons of life histories of a specific species (Le Cren, 1951; Wotton, 1990). The condition factor (K) gives information when comparing two populations living in certain feeding, density, climate, and other conditions; when determining the period of gonad maturation; and when following up the degree of feeding activity of a species to verify whether it is making good use of its feeding source (Weatherley, 1972). The morphometric relationships between length and weight (LWRs) can be used to assess the well-being of individuals and to determine possible differences between separate unit stocks of the same species (King, 2007). In addition, they may also help to determine whether somatic growth is isometric or allometric (Ricker, 1975), as well as to describe seasonal variations of growth within species (Bobori et al., 2010). The aim of this study was to evaluate the length-weight relationship and condition of the native Scoranza bleak population from Lake Skadar. In this paper we want to show that only a detailed study (multiple samples and a large number of specimens from all age categories) can provide accurate data. Consideration of the life-history strategies of Scoranza bleak should be of great significance for the fisheries management, restoration and monitoring. This paper provides the first comprehensive information on the Length-Weight Relationship (LWR) of Scoranza bleak from the Lake Skadar, in order to determine whether there is there one or two stocks of the latter species in this lake. Ecologica Montenegrina, 40, 2021, 80-92 81
ARE THERE ONE OR TWO STOCKS OF SCORANZA BLEAK IN LAKE SKADAR Materials and Methods Area and habitat study. Lake Skadar is situated on the border of Montenegro and Albania (two thirds of the lake belongs to Montenegro, one third belongs to Albania). Lake Skadar is a karst lake created by inundation of a karstic field. It is situated between 19o 15' of eastern geographical longitude and 40o 10' of northern geographical latitude, at the very south of the Republic of Montenegro, With the surface area that fluctuates seasonally from approximately 370 to 540 km2 and water level also varies seasonally from 4.7 to 9.8 m above sea level (Pešić et al., 2018). Lake Skadar is the largest lake on Balkan Peninsula Its shape is elongated oval with peak width of circa 14 km at average water level (Figure 1). The lake extends in the NW-SE direction, and it is approximately 44 km long, with the mean depth of 5 m (Beeton, 1981). Figure. 1. Map of location of the Lake Skadar and study area. The grey oval marks indicate the four sampling sites. Waters from the watershed reach the lake by ground or underground water courses, through a number of sublacustrine springs (so called “oka” – “eye”). The largest tributary of Lake Skadar is the Morača River which brings around 62% of water, while the waters flow away from the lake into the sea by the Bojana River; its average flowing through is over 300 m3/s. Average monthly water temperatures range 5-7 oC in winter, to 25-28 oC in summer. During the summer the transparency of lake waters is 2-3 meters, but in winter it increases reaching up to 5 meters (Lasca et al., 1981; Petrović, 1981; Kastratović, 2018). 82
MARIĆ & BURZANOVIĆ The southern and southwestern sides of the lake are rocky, barren and steep, having bays in which the sublacustrine springs, are usually found. On the northern and northwestern side there is an enormous inundated area, the boundaries of which change as water levels fluctuate. these shores are overgrown by submersive and emerse vegetation (Myriophyllum sp., Ceratophyllum sp., Potamogeton spp., Phragmites sp., Trapa spp., Nymphea sp., Numphar sp. etc.), which tend to extend (Hadžiablahović, 2019). The average chlorophyll a concentration indicates mesotrophic conditions in Lake Skadar, but during mid-summer, when the highest phytoplankton abundance and biomass occurs, the trophic level of the lake increases to eutrophy (Rakočević, 2018). The lake represents one of the most important center of biodiversity for Western Balkan and South-East Europe with more than 100 species of water birds (Vizi, 2018) and 41 (34 autohtonus and 7 alohtonus) fish species (Marić, 2019). Fish are the lake’s most significant natural resource in terms of contribution to the local economies. Annual catch in Lake Skadar is 300 tones of fish, mainly Cyprinus carpio and Alburnus scoranza in the least decade (Marić, 2018). Fish collection and measurements and statistical analisis. Our study was conducted in the winter period during November to March 2012 and in November 2013 using various commercial fishing gears. A total of 1386 specimens of Scoranza bleak at Lake Skadar was caught. The study area included 3 localities at Lake Skadar: Raduš, Karuč and Virpazar. At the locality Raduš (7 samples), the Sscoranza bleak was caught with liftnets (kalimera-a type of stationary lift net) (885 specimens), sample from Karuč (7 samples) was caught using 14-16 mm mesh-sized sinking gill nets - scoranza bleak gill nets (365 individuals), and sample from Virpazar (1 samples) caught with hand nets (136 juvenile specimens). All specimens were measured for total length (TL, in cm) and weight (W, total wet weight in g) to the nearest 0.01g by an electronic balance immediately after collection (fresh). The total length (TL) of each fish (measured using digital caliper to the nearest 0.01 mm) was taken from the tip of the anterior part of mouth to the end of the caudal fin. Data from multiple periods from the same location were considered as separate analytical units. The LWRs then was calculated for each samples of A. scoranza using the following Le Cren (1951) equation: W=aLb, where W is the weight of body (g), : is a constant coefficient and b is the slope of the curve. The determination coefficient (R2) was used as an indicator of the quality of the regressions. If b = 3, growth is isometric, if b < 3, it is negative allometric and if b > 3, it is positive allometric (Ricker, 1975; Froese, 2006). Hence, the t-test was used in order to show significant deviation of obtained b- value in this study from the expected isometric value (b=3). = − 3 S , where, Sb is the Standard error of the b-value, b is the slope value of the curve estimation and Ts is the t-Test value. This analysis was performed both on the whole sample and on the sample subdivided by sex. Because the LWR for the same fish species is often different between adults and juveniles, the LWR was calculated separately for several length groups. The sex was determined macroscopically by dissecting the organisms and looking directly at the gonads. The age of all individuals from Virpazar was determined using scales. Fulton’s condition factor (K or CF), showing the degree of well-being of the fish in their habitat (Froese, 2006) was calculated using the equation: K = (W/L3)x100. Which, K or CF is the Condition Factor, W is the weight of individual of fishes and L is the total length value of individual of fishes and the factor 100 is used to bring K close to unity. The differences between sex, sites and samples were analysed by t–test or Analysis of Variance (ANOVA). All the statistical analyses were considered at a significance level of 5% or 1% or 0.1% (P
ARE THERE ONE OR TWO STOCKS OF SCORANZA BLEAK IN LAKE SKADAR Figure 2. The weight–length relationship and condition factor of Scoranza bleak from Virpazar. Young or individuals less than 12 cm caught at the Raduš site have the same growth pattern (LWR) as young individuals caught at the Virpazar site. The b-values were ranged from 3.36 to 3.60. The results are given below: Virpazar: Length
MARIĆ & BURZANOVIĆ Applying the t-test, it was noticedthat the regression coefficients of both the groups mentioned above differed significantly at 1% level. The results are given below: Length ≥12 cm (n= 365, all), (to 18.5cm) Y=0,0348x2.4505 R2 =0.7126 (Figure 3) Length ≥12 to 15.5 cm (n= 254), Y=0,0166x2.732 R2 =0.6511 (Figure 4 ) Figure 3. The weight–length relationship of Scoranza bleak from Karuč. Locality Raduš. The results of LWR ( and b parameters and R2) of Scoranza bleak population, from locality Raduš according to separate samples are shown in Table 2. Some data of LWR are presented in Fig. 3. No signffcant differences (P>0.05) were found between the males and females from Raduš. Table 2. Values of and b parameters and R2 in separate samples from Raduš. 13.12.201 13.12. 9.01.201 30.01. 30.01. 20.02. 20.02. 4.03. 4.03. 14.03. 14.03. 2 2012 3. 2013. 2013. 2013. 2013. 2013. 2013. 2013. 2013. N=136 N=145 N=46 N=49 N=101 N=84 N=66 N=67 N=83 N=80 N=50 10-12 cm ˃12cm ˃12 cm 10-12cm ˃12 10-12cm ˃12cm 8.5-12cm ˃12cm 8.5-12cm ˃12cm 0.0015 0.0133 0.0157 0.0130 0.0104 0.0023 0.0140 0.0150 0.0061 0.0031 0.0095 b 3.6504 2.7860 2.6995 3.6997 2.8358 3.4374 2.7707 3.5962 3.0302 3.2921 2.8530 R2 0.7186 0.8114 0.8239 0.4252 0.7164 0.9103 0.6602 0.9255 0.8517 0.8988 0.8699 Altogether 885 fish of the length range 8.5-15.5 cm were examined. The b values from the seven samples from Raduš were ranged from 2.6995 to 3.0302 for specimens larger than 12 cm. Based on the current data, there were no significant deviation (P>0.05) between obtained b values of A. scoranza samples and the b value of isometric growth (b=3), while there were a significant differences for the younger specimens (P
ARE THERE ONE OR TWO STOCKS OF SCORANZA BLEAK IN LAKE SKADAR The specimens large than 12 cm from the seven samples were adjusted adequately to the length– weight exponential (power function) model, and no signffcant differences were found between the samples of isometric growth (P>0.01 in all cases) from the Raduš locality; therefore, the data were pooled by using all individuals, and treating them as a single group. Length distribution of A. scoranza specimens caught at both sampling sites (Raduš and Karuč) is given in Figure 4. Also, for Raduš, differences were statistically insignificant between females and males (P>0.05), therefore, the data were pooled by using all individuals (length ≥12 cm), and treating them as a single group. The results of LWRs estimation in this research (table 3) showed a high association between length growths and weight which was statistically significant in specimens larger than 12 cm (P
MARIĆ & BURZANOVIĆ the sampling tools. We found no significant differences in weight/length relationship of Scoranza bleak between the studied sites, suggesting that Lake Skadar contains one stock or one homogenous population. The condition factor of Scoranza bleak. The condition factor for the sample from Virpazar varies in the range of 0.36 - 0.72 with an average value of 0.55 (SD = 0.06). In specimens that are older than one year, i.e. in this case they are two years old, the condition factor varies from 0.51 to 1.34. The condition factor of Scoranza bleak population from the studied sites is shown in Fig. 4-5. Table 3. Values of condition faktor (CV) in separate samples from Raduš. P e r i o d s 13.12.2012 9.01.2013. 30.01.2013. 20.02.2013. 04.03.2013. 14.03.2013. 9.12.2013. N=280 N=74 N=150 N=150 N=150 N=131 N=100 CV 0.77 0.74 0.69 0.66 0.65 0.64 0.77 Table 4. Values of condition faktor (CV) in separate samples from Karuč. P e r i o d s 13.12.2012 9.01.2013 20.02.2013. 4.03.2013. 01.11.2013 20.11.2013. 9.12.2013. N=120 N=74 N=40 N=30 N=87 N=101 N=71 CV 0.93 0.7 0.67 66 1.07 0.84 0.85 The Fulton’s condition factor of A. scoranza sampled in study area has average values between 1.07 and 0.64. Females proved to be in better condition than males, but the differences were not statistically significant (P
ARE THERE ONE OR TWO STOCKS OF SCORANZA BLEAK IN LAKE SKADAR Figure 7. Length and weight variability of Scoranza bleak from Raduš during the fish caught season (1 November - 14 March). The mean condition factor varied during season. Maximum value was obtained from November and December; however, they were low March during the sampling period. Therefore, the average condition factor was not calculated for all samples (Fig. 8). Figure 8. Condition factor of Scoranza bleak from Raduš and Karuč during the fish caught season (1 Novembar - 14 March = 135 days). Discussion The weight–length relationship and condition factor of Scoranza bleak (A. scoranza), were studied in specimens from Lake Skadar during the winter period. The results presented in this study contribute to the knowledge weight-length relationship and the condition factor variability. The parameters of the LWR might be affected by various factors including season, sex, differences in the length range of the caught specimens, population density, sexual maturity age, habitat, food quality or quantity, fish health or environmental conditions (Petrakis & Stergiou, 1995; Froese & Pauly, 2017; Kharat et al., 2008; Milošević & Marić, 2012; De Giosa et al., 2014; Özpiçak et al., 2018). A number of studies about the ratio of length and weight have been conducted on fish found in the world, but in many of these studies the length dependence was not 88
MARIĆ & BURZANOVIĆ analyzed (see for examples at https://www.fishbase.se/Search.php). There are only one study related to the biology of fishes from the Skadar Lake drainage, in terms of growth related to differences in the length range (Marić & Rakočević, 2014). Alburnus scoranza (Bonaparte, 1845), is an important freshwater species for comercial and recreational fishing in Montenegro (Marić, 2018). Many studies have been carried out on Scoranza bleak in Montenegro and other countries in the past (Coble & Knežević, 1981). The parameters for LWR and the type of growth were estimated for the first time in A. scoranza specimens from the Lake Skadar. Our study reveals that there was no difference in the LWR between juveniles from Raduš and Virpazar. On the other hand, the present study revealed that length groups of a smaller size had positive allometric growth as compared to larger specimens that shows negative allometric growth. Our result is consistent with Khan et al. (2012) who showed that juvenile and adult stages of a fish may exhibit differences in the length-weight relationships owing to the changes in the body form with size, feeding habits and factors related to reproduction. In fisheries practice of length-weight relationship (LWR) research is common (Froese, 2006). The Fulton’s condition factor (CF) is a widely used parameter that helps assess the general condition of fish, their growth, survival, maturity, and reproduction (Le Cren, 1951). In fish from Montenegrin waters, these parameters have been poorly studied, in more detail only for C. carpio (Milošević & Marić, 2012), two species of the genus Rutilus (Milošević et al., 2012) and S. farioides (Marić & Rakočević, 2014). Partial studies were performed on several species from Lake Skadar collected over a long period of time, and presented as aggregate data (e.g., Milošević & Mrdak, 2015). In the earlier period, Scoranza bleak and Carp were investigated by Coble & Knežević (1981). The study of condition factor in A. scoranza during the late autumn and winter period when this species usually migrates to sublacustric springs (Drecun & Ristić, 1964; Marić & Kažić, 1990) reveals a statistically significant decrease in this coefficient during the studied period (R2 = 0.79). At the beginning of the fishing season CF usually exceeds the value of 1.0, and at the end of the fishing season the value of the latter coefficient decreases to about 0.65. At the same time, this shows that specimens lose weight during the winter period (Fig. 7), which would mean that fish practically do not feed during this period. According to Ivanović (1965), the Scoranza bleak from the Lake Skadar feeds very little or does not feed at all during the winter. This research shows that through the conditioning factor, which can be easily calculated by the analysis of live individuals, it can be determined whether the species that in this case is Scoranza bleak feed or did not feed in studied water body for a longer period. At the same time, the above-mentioned data for Scoranza bleak, show that they end their intensive growth as early as November and from that period annual rings begin to form. Unlike the Scoranza bleak, C. auratus was found to feed intensively during the winter period, but due to its nutrition which is mainly represented by detritus, it slows growth (Marić, 2000). The condition factor in smaller specimens of A. scoranza, one year of age, differs significantly from larger specimens, but in larger specimens longer than 11 cm variability in relation to length and sex has not been determined. This shows that the feeding and thus the growth of young specimens differ significantly from the older ones, which has already been established in other species (Milošević & Marić, 2012; Marić & Rakočević, 2014). The analysis of length - weight relationship (LWR) shows that individuals of A. scoranza with different sizes have different values of the coefficient b, i.e. they have a different growth pattern. Young specimens have positive and large negative allometry, which is especially visible in specimens larger than 12 cm. This inequality in the growth of smaller and larger specimens is also recorded in other species, although in some species smaller specimens have positive and sometimes negative allometry (Milošević & Marić, 2012; Marić & Rakočević, 2014; Milošević & Mrdak, 2016). Analysis of samples during the winter period, when Scoranza bleak does not feed, as already explained, shows that there are no changes in the growth pattern. All large specimens from 7 periods, during the winter period, from the Raduš and Karuč sites have negative allometry. This paper shown that the existence of two Scoranza bleak stocks in Lake Skadar (Coble & Knežević, 1981) has no support. The study of the existence of different stocks is common in fish. Recent genetic research that has been done has shown the existence of different stocks not only between rivers but also in the same river (Anderson et al., 2007, Miettinen et al., 2020). In some lakes, as many as 4 morphs or stocks have been found that differ morphologically in growth and nutrition (Østbye et al., 2020). Fish polymorphism has been shown to be present in species living in deep lakes (Jonsson et al., 1998, Salzburger, 2018; Østbye et al., 2020). In Skadar Lake, however, morphological or ecological polymorphism of fish cannot be expected, because the lake is shallow (Beeton, 1981). Ecologica Montenegrina, 40, 2021, 80-92 89
ARE THERE ONE OR TWO STOCKS OF SCORANZA BLEAK IN LAKE SKADAR We assume that assumption of two stocks made by Coble & Knežević (1981) is a consequence of differences in the length structure of Scoranza bleak in the analysed samples. In this study, A. scoranza from some samples (which were treated as a whole) have different growth models, but separating young specimens from the sample showed that larger specimens (≥12 cm) had negative allometry. This suggests that in LWR analysis the age groups must be analysed separately. If it turns out that there is no infra- population difference in the growth pattern, the required parameter for the entire population can be calculated and compared with other populations. Unfortunately, not enough attention is paid to this problem in the so-called “technical contribution” that is published in numerous journals where LWR data are given mainly for the whole population and not by age. For example, LWR data calculated for the entire population were published for several species of fish from Skadar Lake, and for the Scoranza bleaks by Milošević & Mrdak (2016) who stated that the population from the Lake Skadar shows negative allometry as a growth model. However, in the latter study, both small (6.3 cm and 2.2 g) and larger samples (17.9 cm and 47.4 g) were analyzed together. Acknowledgements We thank two anonymous reviewere, whose constructive comments greatly improved this paper. References Bobori, D.C., Moutopoulos, D.K., Bekri, M., Salvarina. I. & Muňoz, A.I.P. (2010) Length-weight relationships of freshwater fish species caught in three Greek lakes. Journal of Biological Research- Thessaloniki, 14, 219–224. Anderson, C. E., Waples, S. R. and Kalinowski T.S. (2008) An improved method for predicting the accuracy of genetic stock identification. Canadian Journal of Fisheries and Aquatic Sciences, 65(7), 1475– 1486. https://doi.org/10.1139/F08-049 Beeton, A.M. (1981) Physical conditions of Lake Skadar and its Basin. General introduction. In:Karaman G.S. & Beeton, A.M. (Eds.) The biota and limnology of Lake Skadar. University Veljko Vlahović, Institute of Biological and Medicine Research Titograd, Smithsonian institution, Washington, DC, USA, pp. 15–17. Burzanović, K. & Marić, D. (2017) Population structure, state and perspectives, of bleak (Alburnus scoranza Bonaparte, 1845) from the Skadar Lake. The 1st SouthEast European Ichtyological Conference (SEEIC), Sarajevo, Ilidža, September, pp. 27–29. Coble, W. D. & Knežević, B. (1981) Growt and mortality of Bleak (Alburnus alburnus alborella) and Carp Cyprinus carpio) in Lake Skadar. In: Karaman, G.S. & Beeton M.A. (Eds.) The Biota and Limnology of Lake Skadar. Institute for Biological and Medical Research in Montenegro, Titograd & Centre for Great Lakes Studies, Milwaukee, pp. 320–334. De Giosa, M., Czerniejewski, P. & Rybczyk, A. (2014) Seasonal Changes in Condition Factor and Weight- Length Relationship of Invasive Carassius gibelio (Bloch, 1782) from Leszczynskie Lakeland, Poland. Advances in Zoology. Article ID 678763, 7 pages. Drecun, Đ. & Miranović, M. (1962) Ulov ribe na Skadarskom jezeru 1947-1960. Hydrobiologia Montenegrina, 1(10), 1–19. Drecun, Đ. & Ristić, M. (1964) Sublakustrična vrela ” oka“ i njihov značaju ribolovu Skadarskog jezera. Hydrobiologia Montenegrina, 2 (5), 1–21. Diaz, L.S., Roa, A., Garcia, CB., Acero, A. & Navas G. (2000) Length-weight relationships of demersal fishes from the upper continental slope off Colombia. Naga, The ICLARM Quarterly, 23(3), 23–25. Froese, R. (2006) Cube law, condition factor and weight-length relationships: History, meta-analysis and recommendations. Journal of Applied Ichthyology, 22(4), 241–253. https://doi.org/10.1111/j.1439- 0426.2006.00805.x. Froese, R. & Pauly, D. (eds.) 2017. FishBase. [Version 10/2017] www.fishbase.org. Hadžiablahović, S. (2018) The Diversity of the Flora and Vegetation of Lake Skadar/Shkodra. In: Pešić, V., Karaman, G. & Kostoanoy, A. (Eds): Lake Skadar/Shkodra Environment. The Handbook of Environmental Chemistry, vol 80. Springer, Cham, pp 203–238. 90
MARIĆ & BURZANOVIĆ Ivanović, B. (1965) Nutrition of Albumus albidus alborella (Filipi). Poljoprivreda i šumarstvo, 11 (3-4), 49– 61. (In Serbian) Jonsson, B., Skúlason, S., Snorrason, S. S., Sandlund, O. T., Malmquist, H. J., Jónasson, K., & Lindem, T. (1998) Life history variation of polymorphic Arctic charr (Salvelinus alpinus) in Thingvallavatn, Iceland.Canadian Journal of Fisheries and Aquatic Sciences., 45, 1537–1547. https://doi.org/10.1139/f88-182 Kastratović, V. (2018) The water and sediment chemistry of Lake Skadar. In: Pešić, V., Karaman, G. & Kostoanoy, A. (eds,) Lake Skadar/Shkodra Environment. The Handbook of Environmental Chemistry, vol 80. Springer, Cham, pp. 121-151. https://doi.org/10.1007/698_2017_233 Khan, MA, Khan, S & Miyan, K. (2012) Length– weight relationship of giant snake head, Channa marulius and stinging catfish, Heteropneustes fossilis from the River Ganga, India. Journal of applied Ichthyology 28, 154–155. Kharat, S.S., Khillare, Y.K. & Dahanukar, N. (2008) Allometric scaling in growth and reproduction of a freshwater loach Nemacheilus mooreh (Sykes, 1839). Electronic Journal of Ichthyology, 4(1), 8–17. King, R. P. (1996) Length–weight relationships and related statistics of 73 populations of fish occurring in inland waters of Nigeria. Naga, the ICLARM Quarterly, 19(3), 49–53. Konan, K.F., Ouattara, A., Ouattara, M. & Gourčne G. (2007) Weight–Length Relationship of 57 fish species of the coastal rivers in South–Eastern of Ivory Coast. Ribarstvo, 65(2), 49–60. Lasca, N.P, Radulović. V., Ristić, R.J. & Cherkauer, D.S. (1981) Geology, hydrology, climate and bathymetry of Lake Skadar. In: Karaman, G.S. & Beeton, A.M. (Eds.) The biota and limnology of Lake Skadar. University Veljko Vlahović, Institute of Biological and Medicine Research Titograd, Smithsonian Institution, Washington, pp. 17–38. Le Cren, E. D. (1951) The length-weight relationship and seasonal cycle in gonad weight and condition in the perch Perca fluviatilis. Journal of Animal Ecology, 20 (2), 201–219. Marić, D. (1995) Endemic fish spacies of Montenegro. Biological Conservation, 72, 187–194. Marić, D. (2000) Feeding of Carassius auratus gibelio (Bloch) in Skadar Lake (Montenegro) and competetive relations with autochthonus cyprinid species. CANU, Glasnik Odjeljenja prirodnih nauka, 13, 237-258. Marić, D. (2018) The Ichthyofauna of Lake Skadar/Shkodra: Diversity, Economic Significance, Condition, and Conservation Status. In: Pešić, V., Karaman, G. & Kostianoy, A. (Eds.) Lake Skadar/Shkodra Environment. The Handbook of Environmental Chemistry, vol 80. Springer, Cham, pp. 363–381. Marić, D. (2019) Fauna of Freshwater Fish (Osteichthyes) of Montenegro. Montenegrian Academy of Science and Arts, Special edition, Book 149, vol 48. Department of Natural Sciences, Podgorica, 419 pp. (In Serbian) Marić, D. & Kažić, D. (1990) Kvalitativno - kvantitativni sastav ihtifaune sublakustričnih izvora Skadarskog jezera u zimskom periodu od 1976. do 1987. Glasnik Republičkog zavoda za zaštitu prirode - Prirodnjačkog muzeja, 23, 85–96. Marić, D. & Rakočević, J. (2014) Some Life - History Traits of the Adriatic Beown Trout, Salmo farioides (Karaman, 1938) (Salmonidae) from the Morača River (Montenegro). Acta zoologica bulgarica, 66 (4), 539–546. Miettinen, A., Palm, S., Dannewit, J. & Lind, E. (2020) A large wild salmon stock shows genetic and life history differentiation within, but not between, rivers. Conservation Genetics, 22, 35–51. https://doi.org/10.1007/s10592-020-01317-y Milošević, D. & Marić, D. (2012) Length- weight relationship and condition factor of Cyprinus carpio from Skadar Lake (Montenegro) during spawn-ing period. Agriculture and Forestry, 52, 53–60. Milošević, D. and Mrdak, D. (2016) Length-weight relationship of nine fish species from Skadar Lake (Adriatic catchment area of Montenegro). Journal of Applied Ichthyology 32, 1331–133. Milošević, D., Pešić, V., Petrović, D., Pavićević, A. & Marić, D. (2012) Length-Weigth Relationship and Conditions factor of two sympartic Rutilus (Rafinesque, 1820) species from Lake Skadar (Montenegro). Archives of Biological Sciences, 64 (3), 991–994. Østbye, K., Hagen Hassve, M., Peris Tamayo, A-M., Hagenlund, M., Vogler, T. & Præbel, K. (2020) “And if you gaze long into an abyss, the abyss gazes also into thee”: four morphs of Arctic charr adapting to a depth gradient in Lake Tinnsjøen. Evolutionary Applications, 13(6), 1240–1261. https://doi.org/10.1111/eva.12983 Ecologica Montenegrina, 40, 2021, 80-92 91
ARE THERE ONE OR TWO STOCKS OF SCORANZA BLEAK IN LAKE SKADAR Özpiçak, M., Saygın, S., Hançer, E., Aydın, A., Yılmaz, S. & Polat, N. (2018) Length-weight and length- length relationships of chub (Squalius cephalus, L., 1758) inhabiting a few inland waters of the Middle Black Sea Region. Ege Journal Fisheries and Aquatic Sciences, 35(2), 175–179. Petrakis, G. & Stergiou K.I. (1995) Weight-length relationships for 33 fish species in Greek waters. Fisheries Research, 21 (3-4), 465–469. Petrović, G (1981) Chemical investigations of water and sediment of Lake Skadar. In: Karaman, G.S. & Beeton, A.M. (Eds.) The biota and limnology of Lake Skadar. University Veljko Vlahović, Institute of Biological and Medicine Research Titograd, Smithsonian institution, Washington, DC, USA, pp, 68– 96. Pešić, V., Karaman, G.S. & Kostianoy, A.G. (2018) Introduction. In: Pešić V., Karaman G. & Kostianoy A. (Eds.) The Skadar/Shkodra Lake Environment. The Handbook of Environmental Chemistry, vol 80. Springer, Cham, pp.1–10. Pešić, V., Grabowski, M., Hadziablahović, S., Marić, D. & Paunović, M. (2020) The Biodiversity and Biogeographical Characteristics of the River Basins of Montenegro In: Pešić, V., Paunović, M. & Kostianoy, A. (Eds.) The rivers of Montenegro. The handbook of environmental chemistry, vol. 93. Springer, Cham, pp. 157–200. https://doi.org/10.1007/698_2019_414 Rakočević, J (2018) The phytoplankton and trophic state of Lake Skadar/Shkodra. In: Pešić, V., Karaman, G. & Kostoanoy, A. (Eds.) Lake Skadar/Shkodra Environment. The Handbook of Environmental Chemistry, vol 80. Springer, Cham, pp. 153–167. Ricker, W.E. (1975) Computation and interpretation of biological statistics of fish populations. Journal of the Fisheries Research Board of Canada, 401 pp. http://dx.doi.org/10.1038/108070b0, Salzburger, W. (2018) Understanding explosive diversification through cichlid fish genomics. Nature Reviews Genetics, 19, 705–717. https:// doi.org/10.1007/s1075 0-019-3903-1 Talevski, T., Milošević, D., Marić, D., Petrović, D., Talevska, M. & Talevska, A. (2009) Biodiversity of ichthyofauna from Lake Prespa, Lake Ohrid and Lake Skadar, Biotechnology and Biotechnological Equipment, Special Edition, 23(2), 400–404. Vaslet, A., Bouchon-Navaro, Y., Louis, M. & Bouchon, C. (2008) Weight-length relationships for 20 fish species collected in the mangroves of Guadeloupe (Lesser Antiles). Journal of Applied Ichthyology, 24, 99–100. Vizi, O. (2018) Ornithological features of Skadar Lake. In: Pešić, V., Karaman, G. & Kostianoy, A. (Eds.) Lake Skadar/Shkodra Environment. The Handbook of Environmental Chemistry, vol 80. Springer, Cham, pp. 415–445. Weatherley, A.H. & Gill, H. S. (1987) The biology of fish growth. Academic Press, London, 443 pp. 92
You can also read