INITIAL REARING OF VIMBA LARVAE (VIMBA VIMBA L.) UNDER CONTROLLED CONDITIONS ON NATURAL FOOD AND COMMERCIAL FODDER

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1 POLISH JOURNAL OF NATURAL SCIENCES Abbrev.: Pol. J. Natur. Sc., No 21(2): , Y INITIAL REARING OF VIMBA LARVAE (VIMBA VIMBA L.) UNDER CONTROLLED CONDITIONS ON NATURAL FOOD AND COMMERCIAL FODDER Roman Kujawa, Piotr Hliwa 1, Andrzej Martyniak 2, Andrzej Mamcarz, Dariusz Kucharczyk Chair of Lake and River Fisheries 1 Chair of Ichthyology 2 Chair of Fish Biology and Rearing University of Warmia and Mazury in Olsztyn K e y w o r d s: Vimba vimba, larvae, controlled rearing, natural food, formulated diets. Abstract Vimba (Vimba vimba L.) larvae were initially reared at 25.0 ± 0.5 o C for the period of 20 days. The stock in 25-liter tanks was 1000 larvae per tank. The first natural food (naupliuses of artemia) was substituted by feeds by Aller Aqua intended for commercial rearing of carp (Aller Uni Starter) and trout (SGP 493 Krystal). Application of commercial starter feeds by Aller Aqua, after 10 days of feeding the larvae on natural food proved useful and justified for rearing and practical reasons. Better rearing results expressed by indicators (survival, ITL, RGR, RBR) were achieved substituting the natural food with formulated starter carp diet by Aller Aqua. PODCHÓW LARW CERTY (VIMBA VIMBA L.) W WARUNKACH KONTROLOWANYCH NA POKARMIE NATURALNYM I PASZY KOMERCYJNEJ Roman Kujawa, Piotr Hliwa 1, Andrzej Martyniak 2, Andrzej Mamcarz, Dariusz Kucharczyk Katedra Rybactwa Jeziorowego i Rzecznego 1 Katedra Ichtiologii 2 Katedra Biologii i Hodowli Ryb Uniwersytet Warmińsko-Mazurski w Olsztynie S ł o w a k l u c z o w e: Vimba vimba, larwa, chów kontrolowany, pokarm naturalny, pasze komercyjne. Address: Roman Kujawa, Chair of Lake and River Fisheries, University of Warmia and Mazury, Michała Oczapowskiego 5, Olsztyn, Poland, roman.kujawa@uwm.edu.pl lub reafisha@uwm.edu.pl

2 972 Roman Kujawa et al. Abstrakt Larwy certy (Vimba vimba L.) podchowywano w temp. 25,0 ± 0,5 o C przez 20 dni. Obsada 25-litrowych zbiorników wynosiła 1000 osobników. Pierwszy pokarm naturalny (naupliusy solowca) zastępowano paszami firmy Aller Aqua, przeznaczonymi do komercyjnych podchowów larw karpia (Aller Uni Starter) i pstrąga (SGP 493 Krystal). Zastosowanie komercyjnych pasz startowych firmy Aller Aqua, po 10 dniach karmienia larw pokarmem naturalnym, ze względów hodowlanych i praktycznych okazało się celowe i uzasadnione. Lepsze wyniki hodowlane, wyrażone wskaźnikami (przeżywalność, ITL, RGR, RBR), osiągnięto, zastępując pokarm naturalny komercyjną paszą dla karpi typu starter, firmy Aller Aqua. Introduction Deteriorating natural environment conditions and regulation of riverbeds have resulted in many irreversible changes in aquatic ecosystems. Construction of barriers caused destruction of natural spawning sites and initial growth sites for young reophile fish in many places and made traveling of double habitat fish up the rivers for spawning (BACKIEL 1985, BACKIEL and BONTEMPS 1995). Sedimentation of organic substances caused silting up of riverbeds, which in turn caused deterioration in quality and reduction in area of the spawning sites. In so strongly transformed aquatic environment the fish rarely engage in spawning and the spawn laid under such conditions frequently dies out within a short time. Cumulating effects of numerous unfavorable factors has lead to a significant decrease in the number and reach of many species of reophile fish (MARSZAŁ and PRZYBYLSKI 1996, WITKOWSKI 1996a,b, BŁACHUTA 1998), and, as a consequence, classifying some of them as vanishing species or species threatened by extinction (WITKOWSKI 1992, WITKOWSKI et al. 1999). Among reophile cyprinid fish, vimba (Vimba vimba (L.) is the species particularly sensitive to deterioration of water quality (JAKUBOWSKI et al. 1988, PENCZAK et al. 1995, 1996, WITKOWSKI and HEESE 1996). Vimba is the only anadromic traveling cyprinid fish found in the inland waters of Poland (PLISZKA 1953, BONTEMPS 1960). It favors mainly cool flowing waters with high contents of oxygen dissolved in the water. It belongs to the litophile reproduction group (BALON 1975, 1981, MANN 1996). Maintaining the numbers of fish at the level securing survival of the local requires both protection of the natural spawning grounds and the necessity of substituting natural spawning with artificial one, incubation of spawn under controlled conditions and next initial rearing of the material obtained (WOJDA 1997). Controlled initial rearing of the larvae is a very important stage in the material production. During that rearing the larvae can be fed on

3 Initial Rearing of Vimba Larvae live food (naupliuses of Artemia sp.) and/or formulated diets (SCHUMPBERGER et al. 1976, KAMLER et al. 1987, OPUSZYŃSKI et al. 1989, FORESTI 2000). So far, however, no formulated starter diet has been developed for the larvae of reophile cyprinid fish. On industrial scale attempts are taken at feeding the larvae with starters generally available in the market composed for trout or carp larvae. There is little information available, however, on the possibilities of effective substituting of natural food with commercially available formulated feeds. Absence of detailed studies on those issues was the inspiration to take up studies aiming at assessment of possibilities of vimba initial rearing using commercially available starters fed after initial feeding on natural food and defining the minimum necessary period of feeding vimba larvae on natural food. Material and Methods Material Fish The study used larvae of vimba (Vimba vimba Linnaeus, 1758). The ready to spawn specimens of vimba originated from Ostrowieckie lake (HLIWA et al. 2002) through which the Płociczna River flows. After catching them from the natural environment and transporting to the hatching-initial rearing hall, they were placed in 1000 dm 3 tanks. The larvae of vimba were obtained from semi-artificial reproduction (the fish were injected with hormones and released into the tank, where the substrate for placing spawn was prepared). Hormonal stimulation of reproduction was done using Ovopel (HORVATH et al. 1997). Following the stimulating injection, the tank water temperature was increased from 20 to 22 o C. The fish started spawning after 24 hours. After spawning the fish were caught. Mass hatching of the larvae occurred one day since observing the first hatched individuals. They stayed in the tank until the end of gull bladder resorption period. The spawn incubation conditions and vimba larvae characteristics are presented in Table 1. Methods The initial rearing of the larvae using the natural food and starter type feed was done in tanks supplied with water from closed circuit designed by KUJAWA et al. (2000). Fish larvae, on the second day after starting free floating and filling the air bladders with air, were placed in 14 flow-through tanks with the

4 974 Roman Kujawa et al. Conditions of incubation and characteristics of vimba larvae (Vimba vimba L.) Table 1 Parameter Water temperature during incubation ( o C) Time of incubation (days) 4 Larvae length (longitudo totalis) after hatching (mm) 5.0 ± 0.1 Water temperature during yolk sac resorption ( o C) 20 ± 0.5 Yolk sac resorption time (days) 6 Larvae length (longitudo totalis) at the start of feeding (mm) 8.1 ± 0.2 Mean ± standard deviation working capacity of 40 dm 3. The total water replacement time in individual tanks was ca 20 minutes. Water temperature during initial raring was 25.0 ± 0.5 o C. The initial density of larvae in tanks was 25 larvae per 1 dm 3. The content of air dissolved in water ranged from 6.1 to 7.9 mg O 2 dm -3, and the ph from 7.3 to 7.5. During the experiment no presence of ammonia in water was detected. During the entire raring period the day light cycle was constant at 12 hours of light and 12 hours of darkness. The first food (naupliuses of Artemia sp.) was fed to the larvae after 24 hours from placing them in the raring tanks (VANHAECKE et al. 1990). Fish were fed ad libitum. To assure their continuous access to food they were fed six times a day, every 2 hours. The natural food was substituted with formulated diet after 5 and 10 days of initial feeding on naupliuses of artemia. Initially the daily dose of the formulated diet for vimba larvae was 120% of the biomass. Every four days it was decreased by 20% as compared to the initial value. Finally, at the end of raring, the daily dose was 20% of the larvae biomass. The experiment was conducted in 7 experimental groups, each in two repetitions. Three control groups were identified. One consisted of larvae that were fed with naupliuses of artemia only during the entire time of initial raring (20 days) (KA20), the second one was fed on the carp formulated diet only (KK20) and the third one on the trout formulated diet only (KP20). The natural food was substituted by Aller Aqua formulated diets for commercial initial raring of carp larvae (Aller Uni Starter) or trout larvae (SGP 493 Krystal). The compositions of the individual formulated diets used in the experiment is presented in table 2. In planning the setup of the experiments the earlier works on development of reophile fish larvae were considered (WOLNICKI 1996, KUJAWA et al. 1998a-d, KUJAWA 1998, 2004).

5 Initial Rearing of Vimba Larvae Table 2 Chemical composition of Artemia nauplii and starter diets produced by Aller Aqua (% dry weight) Food Component (%) protein fat carbohydrate ash phosphorus Artemia sp Aller Uni Starter SGP 493 Krystal Measurements and data analysis In case of initial raring of larvae on different diets the control sample (2 times 30 larvae) was collected on the day of filling the tanks, before commencement of feeding. The consecutive samples (of 30 larvae each) were collected every four days. Collection of samples was done immediately after switching on the lights and before commencement of feeding. Before measurements the fish caught were subjected to short anesthesia in the solution of 2-phenoxy-ethanol at the concentration of cm3 dm -3. The larvae were weighted with the accuracy of up to 1 mg and their total length (longitudo totalis l. t.) was measured with the accuracy of up to 0.1 mm. After measurements the fish were returned to the appropriate tanks. On the basis of the data obtained the length increase over a time unit ITL (mm d -1 ) was calculated according to the formula (PEŇÁZ et al. 1989): ITL = TL(n 2) TL(n 1 ), t where: TL average total length (longitudo totalis), n 1 beginning of raring, n 2 end of raring, t period of raring (days d). The relative weight increase rate SGR and the relative biomass increase rate (SBR) from the time of commencement of feeding until the completion of the experiment were calculated according to the formulas (BROWN 1957): SGR = 100 ln W 2 lnw 1 and t

6 976 Roman Kujawa et al. SBR = 100 ln (n 2 W 2 ln(n 1 W 1 ), t where: W 1 average initial bodyweight of individual (mg) during raring, W 2 average end bodyweight of individual (mg) during raring, N 1 number of individuals at the beginning of raring, N 2 number of individuals at the end of raring, t duration of raring (days). Next the relative mass increase ratio for the individual RGR and the relative biomass increase rate since commencement of feeding until the end of the experiment were calculated according to the formulas (MYSZKOWSKI 1997): RGR = 100 ( e SGR 100 1) and RBR = 100 ( e SBR 100 1). The rates of increases (SGR and RGR) for the length were calculated in the same way. The biomass of fish in the tanks was calculated as the product of the average individual weight and the number of live individuals. The obtained value was divided by the tank volume. The obtained biomass was expressed in g dm -3. The number of dead fish recorded daily served preparation of cumulated mortality curves for individual raring variants. The statistical differences in mortality of larvae between population groups were analyzed using the χ 2 test (GREŃ 1984, ŁOMNICKI 2003). The χ 2 test was used to verify the zero hypothesis (H0) that the mortality in the compared groups was the same. Statistical differences between experimental groups were established using the DUNCAN test (1955) at the significance level α = Statistical processing of the results was done using the Excel 9.0 and Statistica 6.0 for Windows software. Results The larvae of vimba were willingly consuming both the natural food and the starter diet. Mass and length increases of vimba larvae achieved

7 Initial Rearing of Vimba Larvae a cumulative mortality (% ) day of rearing KK20 A5 A10 KA20 b cumulative mortality (% ) day of rearing KP20 A5 A10 KA20 Fig. 1. Cumulative mortality of vimba larvae (Vimba vimba L.) reared on natural (Artemia sp. A) and artificial foods: carp (a) or trout (b) starters. Transfer to artificial food after 5, 10 days at the end of raring on the natural food were the largest. Similar results were also obtained when the natural food was substituted after 10 days with carp starter. During raring of vimba larvae using different types of feed a larger mass and length of fish were obtained when feeding

8 978 Roman Kujawa et al. a mean body weight ( mg ) mean body length ( mm) day of rearing 0 weight length KK20 A5 A10 KA20 KK20 A5 A10 KA20 b mean body weight ( mg ) KA mean body length ( mm) day of rearing 0 weight length KP20 A5 A10 KA20 KP20 A5 A10 KA20 Fig. 2. Growth of vimba larvae (Vimba vimba L) reared on natural (Artemia sp. A) and artificial foods: carp (a) or trout (b) starters. Transfer to artificial food after 5, 10 days

9 Initial Rearing of Vimba Larvae them with carp starter (Table 3.). The differences in the average mass and length of larvae in individual feed groups appeared after 15 days of raring only (Figure 1 a,b). The average weight of fish fed during the entire period with the naupliuses of artemia was the highest and reached 68.7 mg at the end of raring while the average length reached 20.6 mm. The larvae fed on carp starter from the first day reached the average weight of 21.0 mg and the average length of 14 mm while those receiving trout starter 17.9 mg only and the average length of 13.4 mm. The vimba larvae fed from day 6 or 11 with carp starter reached the average weight of 29.5 and 47.9 mg and average length of 16.9 and 18.6 mm respectively. Much poorer results were obtained feeding the vimba larvae with trout starter as of day 6 or 11. Clear differences in mortality of larvae appeared in the groups where the larvae were fed on starters as of day 1 (Figure 2a, b). It was 57% in the group receiving trout starter as of day 1 and 45.6% in the group receiving carp starter as of day 1. The survival of vimba larvae in the other groups was high and ranged from 97.3 to 99.9%. The length increase rate per time unit was between 0.26 and 0.62 mm d -1. The biomass of fish in both feeding variants differed significantly and ranged from 0.83 to 1.10 g dm -3 in groups fed on formulated diets as of day 6. Fish fed with naupliuses of artemia during the entire experiment reached 2.75 g dm -3. In groups where as of day 11 the natural food was replaced by carp or trout starter s of RGR and RBR calculated for them were also closest to the values calculated for the control group (Table 3). Discussion Securing appropriate feed quality and volume is one of the major issues during raring of fish larvae under controlled conditions. Fresh water zooplankton or naupliuses of artemia Artemia sp. are the most frequently applied live feeds characterized by high availability and acceptance by the majority of fish larvae (BRYANT and MATTY 1980). That can be the only feed during the initial life period of he larvae, but the starter formulated diets can be used as supplements (WIGGINS et al. 1986, FERMIN and RECOMETA 1988, ABI-AYAD, KESTEMONT 1994). The larvae of cyprinid fish should initially be fed on the natural food because only after some time they can effectively assimilate nutrients contained in starter feeds (GRUDNIEWSKI et al. 1979, DABROWSKI 1984a, DĄBROWSKI and POCZYCZYŃSKI 1988). In case of reophile cyprinid fish the group of digestive enzymes during the initial period of life is poor and hence feeding them from the start on formulated diets is not recommended (DABROWSKI 1984b, STANNY 1984).

10 980 Roman Kujawa et al. Results of rearing vimba (Vimba vimba L.) larvae fed with Artemia and transferred to carp starter or trout starter after 5 or 10 days Table 3 Carp starter Trout starter Natural food Parameter feeding period with starter (days) 10(A10) 15(A5) 20(KK20) 10(A10) 15(A5) 20(KP20) 20 (KA20) Initial mean body weight (mg) 2.0 ± 0.2 a 2.0 ± 0.2 a 2.0 ± 0.2 a 2.0 ± 0.2 a 2.0 ± 0.2 a 2.0 ± 0.2 a 2.0 ± 0.2 a Final mean body weight (mg) 47.9 ± 7.1 d 29.5 ± 3.6 c 21.0 ± 4.3 b 42.4 ± 3.7 d 28.3 ± 2.1 c 17.9 ± 2.4 a 68.7 ± 2.6e Initial mean body length (mm) 8.2 ± 0.1 a 8.2 ± 0.1 a 8.2 ± 0.1 a 8.2 ± 0.1 a 8.2 ± 0.1 a 8.2 ± 0.1 a 8.1 ± 0.1 a Final mean body length (mm) 18.6 ± 1.3 c 16.9 ± 1.4 bc 14.0 ± 0.9 b 16.7 ± 0.7 bc 15.4 ± 0.9 b 13.4 ± 0.4 a 20.6 ± 0.6 d Initial stock (indiv.) Final stock (indiv.) 991 ± 3.5 f 934 ± 6.4 d 544 ± 6.4 b 972 ± 2.1 e 733 ± 9.9 c 430 ± 14.1 a 999 ± 1.4 f Survival (%) 99.1 ± 0.3 f 93.4 ± 0.6 d 54.4 ± 0.6 b 97.2 ± 0.2 e 73.3 ± 0.9 c 43.0 ± 1.3 a 99.9 ± 0.1 f Increase in total length (ITL) (mm d -1 ) 0.52 ± 0.0 e 0.44 ± 0.0 d 0.29 ± 0.0 b 0.43 ± 0.0 d 0.36 ± 0.0 c 0.26 ± 0.0 a 0.62 ± 0.0 f Relative growth rate (RGR) of weight (% d -1 ) ± 0.4 d ± 1.0 c ± 1.0 ab ± 0.5 d ± 0.4 bc ± 1.0 a ± 0.4 e Relative growth rate (RGR) of length (% d -1 ) 4.10 ± 0.1 d 3.62 ± 0.3 b 2.66 ± 0.3 a 3.56 ± 0.1 d 3.15 ± 0.1 c 2.46 ± 0.3 a 4.61 ± 0.2 e Relative growth rate (RBR) of biomass (% d -1 ) ± 0.4 d ± 1.0 c 8.71 ± 1.0 b ± 0.5 d ± 0.4 c 6.74 ± 1.0 a ± 0.4 e Biomass (g dm -3 ) 1.90 ± 0.1 e 1.10 ± 0.2 c 0.46 ± 0.2 b 1.65 ± 0.1 d 0.83 ± 0.1 c 0.31 ± 0.1 a 2.75 ± 0.2 f Mean value ± S.D. Results in rows with the same letter index are not statistically significantly different (p 0.05)

11 Initial Rearing of Vimba Larvae The larvae of those species of fish compensate the shortage of their own digestive enzymes partly with the enzymes of consumed zooplankton (POCZYCZYŃSKI 1996). Only after some time, different in different species, they can digest ingested granulated feed. Defining the optimum period during which the larvae should be fed on natural food (to be able to substitute it with formulated diets) is very important during controlled raring. Attempts at feeding the larvae of cyprinid reophile fish (excluding the larvae of barbell and nase) from the very beginning on formulated starters usually end at stopping the growth and decreasing the resistance to diseases, which, as a consequence leads to mass deaths (WOLNICKI 1997, KUJAWA 2004). Some authors believe that feeding cyprinid fish larvae with formulated diet can start when they reach the unit mass of 5-15 mg (BRYANT and MATTY 1981) or mg (STANNY 1984),and that during the initial period of life they should be fed on live food. That allows fast bodyweight increase and achievement of consecutive stages of development. That would explain to a certain extent the fact that the larvae of barbell can practically from the start be fed with starter feeds (KUJAWA et al. 1998d, FIALA and SPURNY 2001). Feeding the larvae of other cyprinids with starter type feeds gives much worse results (lower bodyweight increase and low survival rate) as compared to feeding with zooplankton (STANNY 1984). That is also confirmed by the studies on raring nase larvae with natural feed that after a defined time was substituted by starter feeds (KUJAWA et al. 1998a). That is also confirmed by studies on raring cyprinid fish using starter formulated diets (WOLNICKI 1996, WOLNICKI and GÓRNY 1995ab, WOLNICKI and MYSZKOWSKI 1999ab). They indicate that species of fish such as barbell and nase can be fed from the start on starter formulated diets while the other need several days of raring on natural food. After a certain period of feeding on natural food, the larvae of cyprinid fish can be fed with quite satisfactory results on formulated diets. Application of naupliuses of artemia substituted during raring with commercially available starter feeds allowed in own studies on defining the time for which the larvae must receive natural food to be able later to assimilate nutrients contained in feeds. The results obtained confirm earlier observations (KUJAWA 1998a-d) that during the first period of life different for different cyprinid fish the larvae must receive natural food. It was shown that after 10 days on natural food substitution with starter feeds does not influence survival of the larvae significantly. The growth rate of larvae receiving naupliuses of artemia and feed was lower than that of fish fed all the time on naupliuses of artemia only. Similar results were obtained by LITTAK et al. (1979) for raring of carp larvae when the natural food after 10 days was formulated by formulated diet.

12 982 Roman Kujawa et al. The above data indicate that using feeds only during raring does not allow full use of growth potential of the larvae, which was also confirmed by studies by WOLNICKI and KORWIN-KOSSAKOWSKI (1993), concerning tench (Tinca tinca L.) larvae raring. The studies presented in this paper confirm the earlier observations and results of studies that vimba larvae can be fed on starter type fodders only after a period of feeding on natural food (WOLNICKI 1996, 2000, WOLNICKI et al. 2000, KUJAWA 2004). Knowledge of the minimum period of feeding on natural food and automation of feeding operation by applying feeder (CHARON and BERGOT 1984, 1986) can highly increase vimba stocking material production potential under controlled conditions. Conclusion 1. Early substitution of natural food with tested starter type feeds offered significantly worse results (lower bodyweight increase and low survival rate) than feeding the larvae on naupliuses of artemia. 2. The longer the period of natural food availability, the better the raring effects. 3. Application of commercial starter formulated diets by Aller Aqua, after 10 days of earlier feeding on natural food is useful and justified for raring and practical reasons. 4. Better raring results are achieved when natural food is substituted by carp starter formulated diet by Aller Aqua than by trout starter formulated diet by the same manufacturer. Translated by JERZY GOZDEK Accepted for print References ABI-AYAD A., KESTEMONT P Comparison of the nutritional status of goldfish (Carassius auratus) larvae fed with live, mixed or dry diet. Aquacult., 128: BACKIEL T Fall of migratory fish populations and changes in commercial fisheries impoundment rivers in Poland. In: Habitat modification and freshwater fisheries. Ed. J. S. ALABASTER. Bytterworths. London, BACKIEL T., BONTEMPS S Estimation by three methods of Vimba vimba population in the Vistula River system. Arch. Ryb. Pol., 3: BALON E. K Reproductive guilds of fishes: a proposal and definition. J. Fish. Res. Board. Can., 32: BALON E. K Additions and amendments to the classification of reproductive styles in fishes. Env. Biol. Fish., 6:

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