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Bulgarian Journal of Agricultural Science, 19 (Supplement 1) 2013, 118–125 Agricultural Academy

AGE COMPOSITION AND GROWTH RATE OF THE SPAWNING PART OF THE POPULATION OF PONTIC SHAD IMMACULATA (BENNETT, 1835) IN THE BULGARIAN SECTOR OF RIVER

D. ROZDINA, G. RAIKOVA-PETROVA and P. MIRTCHEVA Sofi a University, Faculty of Biology, Department of Common and Applied Hydrobiology, BG – 1164 Sofi a, Bulgaria

Abstract

ROZDINA, D., G. RAIKOVA-PETROVA and P. MIRTCHEVA, 2013. Age composition and growth rate of the spawning part of the population of pontic shad Alosa immaculata (Bennett, 1835) in the Bulgarian sector of Danube River. Bulg. J. Agric. Sci., Supplement 1:

The age structure and the growth ratе of the population of Pontic shad Alosa immaculata (Bennet, 1835) in the Bulgarian sector of the Danube River are studied. The catchments have been done in April 2010 and April 2012 during the spawning migration of the species. Altogether 239 specimens have been examined. The age of the individuals varied between II and V. The most abundant are II and III age groups representing 53.2% and 37.9% of the spawning part of the population respectively. The standard length ranged from 15.4 cm to 37 cm and the weight ranged from 37 g to 351 g. The equation representing the relation between the standard length and the scale radius in the population is L = 0.3955S – 0.996; r = 0.8. The length – weight relationship is described by the equation W = 0.0234L2.7315 , r = 0.95. The von Bertalanffy`s length and weight growth equations -0.493209 (t-0.34115) -0.319987 (t – 1.04376) 2.7315 are Lt = 35.749 [1 – e ] and Wt = 436.228 [1 – e ] respectively.

Key words: Pontic shad, Alosa immaculata, Danube River, age, growth Abbreviations: NAFA – National Agency of Fisheries and aquaculture

Introduction danov and Kolarov, 1983) but in the recent years the studies are rare (Yankova et al., 2011). The structure of The Pontic shad (Alosa immaculata) is anadromous the Pontic shad in Danube River has been also studied fi sh species, belonging to the family . The spe- by Ciolac and Patriche (2004). cies is native for Bulgaria, Georgia, Moldova, Romania, The species is vulnerable according to IUCN and Russia, Serbia, Turkey and Ukraine. It occurs in Bulgarian Red Data Book (http://e-ecodb.bas.bg/rdb/bg/ and and for spawning, migrates in Danube, vol2/Alpontic.html; http://www.iucnredlist.org/apps/redlist/ Dnepr, Dniester, Don, Bug etc. Since 2001, the species is details/907/0). It is also included in Annex 2 and 4 of established in the Sea of Marmara (Eryilmaz, 2001). the Bulgarian Biodiversity Act (http://www.biodiversity. bg/fi les/File/zak_bg_biodiv.pdf). The species has been regularly studied on the ter- A. immaculata is a commercial fi sh species. Its ritory of Bulgaria (Kolarov, 1958a; 1958b; 1960a, catchments in the last decade vary signifi cantly with a 1960b; 1961; 1963; 1964; 1965; 1978; 1980; 1982; maximum in 2004 (21.95 t) and minimum in 2007 (0.2 1983; 1985; 1989; Ivanov and Kolarov, 1979 and Pro- t) (according to data from NAFA). This catchment vari-

E-mail: [email protected], [email protected], [email protected] Age Composition and Growth Rate of the Spawning Part of the Population of Pontic Shad... 119

ability focused our attention on studying some basic coeffi cient and to (in yr) represents the age a fi sh would biological parameters of the population. have at zero length. The aim of the article is to assess the age and size To asses if the growth potential of the population structure, growth rate and condition factor of the re- was well used the coeffi cient of Hohendorf was applied productive part of the population of A. immaculata in (Hohendorf, 1966). Bulgarian sector of Danube River. Condition of the population has been studied in three ways: ● 3 Material and Methods By the equation of Fulton: kf= (W/L ).100, where W is the fi sh weight (in g) and L is the fi sh length (in The specimens of A. immaculata were collected in cm) April 2010 and April 2011 during the spawning migra- ● By the equation of Fulton but instead the exponent tion of the species. Spawning sites were located in the 3, the exponent b from the length-weight relationship area between Lom and Vidin. The geographical coordi- of the population was used (kb). nates of the sampling points are as follows: Sampling ● Calculating fi sh weight at the length of 5 cm, 10 point 1: 43°54′17.96″N and 22°50′27.45″E; Sampling cm, 15 cm, 20 cm and 25 cm with the use of length- point 2: 43°47′40.46″N and 23°4′50.41″E; Sampling weight relationship. The population with higher point 3: 43°50′45.61″N and 23°18′44.17″E. weight at the same length of fi sh has better condition Altogether 239 specimens were collected (134 indi- (Goldspink, 1979; De Silva, 1985; Basami and Grove, viduals in 2010 and 159 in 2011 respectively). Gill nets 1985; Raikova-Petrova, 1992 and Zivkov, 1999). were used with the size of the eye 32–88 mm. Each specimen was measured the standard length (L) Results and Discussion to the nearest 1 mm, the total weight (W) and the gutted weight (w) to the nearest 1g. The age was determined Age structure of Pontic shad in Danube River was by the scales at magnifi cation of 17.5x with Projector represented from 4 age groups (from II to V) (Table 1). Dokumator, Lasergeret (Carl Zeiss, Jena). Age and size The average age of the population was 2.6 years. The structure was studied according to (Chugunova, 1959). most abundant were two and three year old individu- Length and weight growth rates were determined by als. The oldest specimens were two 5 years old males, back calculation using the following equations: L = a + which represent the less abundant age group. The ab- bS (L – fi sh length, in cm and S – scale radius, in units) sence of individuals older than 5 years was due to the and W = a.Lb (W – fi sh weight, in g) (Le Cren, 1951). commercial fi shing of the species in the Danube Delta Back-calculated lengths and weights at age were where selectively the biggest and the oldest individuals used to calculate the von Bertalanffy’s growth param- were caught. eters, using the software Growth II. Linear and weight The established age structure shows, that in the growths were described using the von Bertalanffy spawning part of the population of A. immaculata (1938) growth equations: replenishment dominates over the residue. Kolarov (1965) reported similar results. L = L (1-e-k(t-to)), t ∞ Kolarov (1960a) reported similar age structure for the Black sea catchments along the Bulgarian shore. where Lt (in cm) is the length of fi sh at age t, L∞ (in cm) is the asymptotic length, k (in yr-1) is the growth Ciolac and Patriche (2004) report six age groups (from 2 to 7 years old individuals) for Pontic shad in Danube coeffi cient and to (in yr) represents the age a fi sh would have at zero length. River. In a study the most abundant were three (41.2%) and four (30.3%) years old individuals. Kolarov (1965; W =W [1-e -k(t-to) ]b, t ∞ 1980) reported for the Bulgarian sector of Danube Riv-

where Wt (in g) is the weight of fi sh at age t, W∞ (in er age structure of 1 to 6 years old individuals of Pontic g) is the asymptotic weight, k (in yr-1) is the growth shad. 120 D. Rozdina, G. Raikova-Petrova and P. Mirtcheva

Table 1 respectively. Other authors describe smaller number of Age-size composition of Alosa immaculata size classes (Pavlov, 1953; Kolarov, 1964; 1980). catchments in Bulgarian sector of Danube River During our study, we established a size structure Size class Age with the smallest average size of the individuals in 2345%n comparison with previous studies. The main reason is the high commercial catchments rates in Danube Delta 15 –15.9 3 1 1.4 4 where selectively the biggest individuals are caught. 16–16.9 12 1 4.4 13 17–17.9 34 12 15.7 46 Temp of growth 18–18.9 20 20 1 14.0 41 The equation representing the relation between the 19–19.9 15 8 7.8 23 fi sh length (L) and the scale radius (S) for the popula- 20–20.9 19 4 7.8 23 tion of Pontic shad is L = 0.3955S – 0.996; r = 0.8. The relation is represented on Figure 1. On Table 2 are 21–21.9 7 6 1 4.8 14 represented the back calculated lengths at age and the 22–22.9 4 5 1 3.4 10 annual increments. 23–23.9 4 1.4 4 40 24–24.9 2 2 2 2.0 6 35 25–25.9 2 5 3 1 3.8 11 30 26–26.9 5 18 8 10.6 31 25 20 27–27.9 11 9 5 1 8.9 26 L, cm 15 28–28.9 10 15 2 9.2 27 10 29–29.9 6 2 1 3.1 9 5 0 30–30.9 2 1 1.0 3 0 102030405060708090 31–31.9 1 0.3 1 S 37–37.9 1 0.3 1 Fig. 1. Relation between the fi sh length (L, cm) and scale radius (S, units of ocular-micrometer) in Pontic shad Total number 156 111 24 2 100 293 (Alosa immaculata) in the Bulgarian sector of Danube % 53.2 37.9 8.2 0.7 River

600 Size structure of A. immaculata was represented with 18 size classes (Table. 1). The most abundant were 500 W = 0,0234L 2,7315 the individuals with size range 17–17.9; 18–18.9 and 400 r = 0.95 26–26.9. The biggest individual was male with length 37 cm, weight 225 g and was 3 years old. The specimen 300 W, g with the highest weight (W = 351 g) was two years old male with a length of 29 cm. The individual with the 200 smallest size had a length of 15.4 cm, weight 37 g, and 100 was 3 years old. The size classes with the highest age range were 25–25.9 and 27–27.9. The III age group had 0 the highest size range and included 17 size classes. The 0 5 10 15 20 25 30 35 40 V age group included only two size classes. L, cm Kolarov (1978) has established 19 size classes in Fig. 2. Relation between the length (L, cm) and weight the area of Silistra and Svishtov. The most abundant (W, g) of Pontic shad (Alosa immaculata) were 21–22 and 23–34 size classes for the both area in the Bulgarian sector of Danube River Age Composition and Growth Rate of the Spawning Part of the Population of Pontic Shad... 121

Table 2 Back calculated length (L, cm) at age and annual length increments for Pontic shad (Alosa immaculata) in the Bulgarian sector of Danube River Generation Age Back calculated average lengths (L, cm) at the end of each vegetation period Number of (year) group L1' L2' L3' L4' L5' fi sh 2009 II 11.58 17.94 100 2008 II–III 11.62 19.43 32.45 111 2007 III–IV 10.67 19.45 26.21 43.10 60 2006 IV 10.51 19.41 25.23 30.98 20 2005 V 8.10 15.22 20.76 24.91 30.05 2 Average length 10 496 18.29 26.20 32 997 30.05 293 Increments 10 4967.8 7.9 6.8 –2.9

Table 3 Back calculated weight (L, cm) at age and annual weight increments for Pontic shad (Alosa immaculata) in the Bulgarian sector of Danube River Generation Age Back calculated average weights (W. g) at the end of each vegetation period Number of (year) group W1' W2' W3' W4' W5' fi sh 2009 II 18.83 62.24 100 2008 II–III 19.01 77.41 314.06 111 2007 III–IV 15.06 77.62 175.37 682.11 60 2006 IV 14.44 77.19 157.89 276.77 20 2005 V 7.09 39.71 92.69 152.54 254.67 2 Average weight 14.89 66.83 185.00 370.47 254.67 293 Increments 14.89 51.9 118.2 185.5 –115.8

The length-weight relationship for the population of yearlings show highest values of length increments. A. immaculata in Bulgarian sector of Danube River is On the fi fth year negative length and weight incre- W = 0.0234L2.7315, r = 0.95 (Figure 2). The back calcu- ments were established (Tables 2 and 3). The negative lated weight at age is represented on Table 3. increments are due to the small number of 5 year old The average length and weight increases with in- fi sh represented in the excerption as well as due to the creasing the fi sh age. Similar results were obtained for commercial fi shing in Danube’s Delta when the biggest other populations of A. immaculata (Kolarov, 1960а; individuals are caught. Kolarov (1978) has established 1964; 1965; 1978; 1980; 1983; 1985; Ciolac and decreasing the average weight of the Pontic shad from Patriche, 2004 and Ergüden et al., 2007). Danube’s mouth to Silistra and Svishtov. Generation 2005 showed the slowest temp of growth In comparison to other populations (Pavlov, 1953; while the fastest growth rate was found for generations Kolarov, 1964; 1965; 1978; 1980; 1983; 1985; Ciolac 2007 and 2008. The nature of linear and weight growth and Patriche, 2004; Ergüden et al., 2007) of the species more precisely is described by the change of the annual the studied by us showed the lower linear increments increments. The length increments decrease with in- during the fi rst and fi fth year of life, while two, three creasing fi sh age, while the weight increments increase and four year old fi sh showed higher increments. The with increasing fi sh weight until the fi fth year. The higher increments for the two and three year old indi- 122 D. Rozdina, G. Raikova-Petrova and P. Mirtcheva

Observed Predicted

Fig. 4. von Bertalanfy’s growth equation curve describing the linear growth of Pontic shad (Alosa immaculata) from Bulgarian sector of Danube River

Observed Predicted

Fig. 3. Ford-Walford curve for the linear growth of Pontic shad (Alosa immaculata) from Bulgarian sector of Danube River Observed Predicted viduals are due to the faster growth rates of the younger age groups and the earlier maturation of the population. Fig. 5. Ford-Walford curve for the weight growth of For some of the populations the changes in the an- Pontic shad (Alosa immaculata) from Bulgarian sector of Danube River nual increments are uneven (Pavlov, 1953; 1965; 1978; 1980; 1985; Ciolac and Patriche, 2004 and Ergüden et Concerning weight increments in comparison to al., 2007). For other populations there is a clear ten- other Pontic shad populations the studied by us showed dency of decreasing the increment with the fi sh age highest values during the third and fourth year. As for (Kolarov, 1964; 1978; 1983, 1985 based on data by the linear increments changes in the weight increments Miklashevskaya, 1953). are uneven for some of the populations (Kolarov, 1964; Age Composition and Growth Rate of the Spawning Part of the Population of Pontic Shad... 123

Table 4 Von Bertalanffy’s growth parameters for the linear and weight growth of A. immaculata Linear growth

Water body and autor L∞, cm k to Danube River (our data) 35 749 0.493209 0.34115 Danube River (Kolarov, 1980) 57.38 0.1067 1727 Danube River, Black sea (Kolarov, 1983) 40.43 0.2705 -0.218 Black sea (Prodanov, Kolarov, 1983) 40.43 0.27 -0.218 Weight growth

W∞ kto Danube River (our data) 436 228 0.319987 104 376 Danube River, Black sea (Kolarov, 1983) 859.7 0.2416 –0.405 Black Sea (Prodanov, Kolarov, 1983) 860.58 0.241 –0.421 Table 5 Variations between the average weights of Pontic shad (Alosa immaculata) from different water bodies cal- culated at the same length by the use of length-weight relationship Water body and author Population length- Average weights calculated at one and the same length weight equation W5 W10 W15 W20 W25 Danube River – our data W = 0.0234L2.7315 1.9 12.6 38.2 83.7 154.1 Kolarov (1983) W = 0.0629L2.574 4.0 23.6 67.0 140.4 249.4 Sea of Marmara, Ergüden et al. (2007) W = 0.0163L2.8511 1.6 11.6 36.8 83.5 157.7 Black Sea, Kalayci et al. (2007) W = 0.0046L3.1237 0.7 6.1 21.7 53.3 107.0 Black Sea, Yılmaz, Polat (2011) W = 0.0032L3.285 0.6 6.2 23.4 60.1 125.1 Black Sea, Yankova et al. (2011) W = 0.071L2.488 3.9 21.8 59.9 122.5 213.5

1978; 1980; 1983; 1985; Pavlov, 1953 and Ergüden reservoir (Raikova-Petrova and Zivkov, 1992). et al., 2007). For other populations weight increments There is a linear regression between the average fi sh increase with increasing the fi sh age (Kolarov, 1978; weight in the end of the t year (Wt) and the weight one

Ciolac and Patriche, 2004). year later (Wt+1) (Figure 5). Based on this the weight There is a linear regression between the average growth of A. immaculata can be described with the von Bertalanffy’s equation (1938) for the weight growth fi sh length at age t years (Lt) and the average length (Figure 6). in one year (Lt+1) (Figure 3). Based on this the linear growth of A. immaculata can be described with the von Bertalanffy’s equation (1938) (Figure 4).

-0.493209 (t-0.34115) Lt = 35.749 [1 – e ] The received value for the asymptotic growth was 35.749 cm. This value was lower than the maximal one obtained by us (37 cm) due to the fast temp of growth Observed Predicted of the young fi sh and absence of adult individuals in the Fig. 6. von Bertalanfy’s growth equation curve describ- excerption. Similar result has been established for the ing the weight growth of Pontic shad (Alosa immaculata) zander (Stizostedion lucioperca) in Ovcharitsa cooling from the Bulgarian sector of Danube River 124 D. Rozdina, G. Raikova-Petrova and P. Mirtcheva

-0.319987 (t – 1.04376) 2.7315 Wt = 436.228 [1 – e ] The values of the coeffi cient of Hohendorf close to one show that the population of A. immaculata in Dan- The obtained asymptotic weight for the conditions ube River uses maximally well its growth potential. in Danube River was 436.228 g. The value of the coeffi cient of Hohendorf (1966) for the linear growth was 1.03 and for the weight growth References was 0.8. The values close to one mean that the pop- Basami, R. and D. Grove, 1985. Studies on feeding, growth ulation of Pontic shad in Danube River best uses its and production of a recruited inshore populations of growth potential. Pleuronectes platessa (L.) at East Anglesey, North Wales. Comparing the temp of growth with the coeffi cient J. Fish Biol., 27: 765–783. k from the von Bertalanffy’s equation the population Bertalanffy, L., 1938. A quantitative theory of organic studied by us shows the fastest growth rates (Table. growth. (Inquiries on growth laws. II). Human Biol., 10 4). Lowest temp of linear growth had the population (2): 182–213. studied by Kolarov (1980) in Danube River and low- Chugunova, N., 1959: Handbook on studying fi sh age and est weight growth rates had the population studied by growth. Moscow, ASUSSR 156 p (Ru). Prodanov and Kolarov (1983). Ciolac, A. and N. Patriche, 2004. Structure of danube shad (Alosa pontica Eichwald, 1838) spawner fl ocks migrat- ing for reproduction in Danube River. Applied Ecology Condition factor and Environmental Research, 2 (2): 53–58. The received value for the coeffi cient of Fulton was De Silva, S., 1985: Body condition and nutritional ecology

1.22 and for kb it was 2.8. Comparing to other popula- of Orefchromis mossambicus (Pisces, Cichlidae) tions the value we received for the coeffi cient of Fulton populations of man-made lakes in Sri Lanka. J. Fish was one of the highest (Kolarov, 1965; 1978; 1980). Biol., 27: 621–633. Ergüden, D., C. Turan and C. Çevik, 2007. The growth Kb for the population studied by us had higher value (2.8) than the one for the population in Marmara Sea features of Pontic Shad Alosa pontica (Eichwald, 1838) (1.88) Ergüden et al. (2007b) and lower values than the in the Sea of Marmara, Turkey. Journal of Biol. Sc., 7 (4): 685–688. population in Black Sea and Danube River (6.8) Ko- Eryilmaz, L., 2001. A study on the bony fi shes caught in the larov (1983a) and the one in Black Sea (7.26) (Yankova south of the Sea of Marmara by bottom trawling and their et al., 2011) morphologies. Turk J Zool., 25: 323–342. Calculated fi sh weight at the length of 5 g, 10 g, 15 Goldspind, C., 1979. The population density, growth rate g, 20 g and 25 g with the use of length-weight relation- and production of roach, Rutilus rutilus, in Tjeukemeer, ship is represented on Table. 5. This index had average the Netherlands. J. Fish Biol., 15: 473–498. values for the population studied by us. The popula- Hohendorf, K., 1966. Eine Diskussion der Bertalanffy – tions studied by Kalayci et al. (2007) and Yilmaz and Funktionen und ihre Anwendung zur Charakterisierung Polat (2011) had lower condition values while the high- des Wachstums von Fishen. Kieler Meeresforsschungen, est condition was established from Kolarov (1983). 22 (1): 70–90. Ivanov, L. and P. Kolarov, 1979. Relation between the Conclusions catchments of Pontic shad (Alosa kessleri pontica, Eichw) and solar activity. Societas internationalis limno- logiae – SIL, XIX, Jubiläumstagung donauforschung, pp. The studied population of A. immaculata is young 389–396 (Ru). with average age of 2.6 years. The most abundant are Klayci, F., N. Samsun, S. Bilgin and O. Samsun, 2007. the fi shes with size range 17–19 cm. The age structure Length-weight relationship of 10 fi sh species caught by is represented from 4 age groups (2 to 5 years old fi sh). bottom trawl and midwater trawl from the middle Black According to von Bertalanffy’s growth model in the Sea, Turkey. TrJFAS, 7: 33–36.

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