Response of a juvenile cyprinid, lake minnow

Eupallasella perenurus (Pallas), to different diets

RAFAŁ KAMINSKI1,*, MICHAŁ KORWIN-KOSSAKOWSKI1,JAN KUSZNIERZ2, LESZEK MYSZKOWSKI1,L. ANDRZEJ STANNY3 and JACEK WOLNICKI11Pond Fishery Department, The Stanisław Sakowicz Inland Fisheries Institute in Olsztyn, _Zabieniec,05–500 Piaseczno, Poland; 2Zoological Institute, University of Wrocław, Sienkiewicza 21, 50–335

Wrocław, Poland; 3Institute of Ichthyobiology and Aquaculture, Polish Academy of Sciences, 43–520

Chybie, Poland; *Author for correspondence (e-mail: erka@infish.com.pl; phone:+48-22-756-74-86)

Received 4 August 2004; accepted in revised form 19 May 2005

Key words: Deformities, Eupallasella perenurus, Feeding, Juvenile, Starter

Abstract. Three commercial starters (Carp Starter, Uni Starter and Perla Plus) and one non-

commercial, with frozen Chironomidae larvae as a reference diet, were evaluated for the intensive

rearing of juvenile lake minnow Eupallasella perenurus, a cyprinid fish that is critically endangered

in Poland. The growth, condition, survival, body deformities, and chemical body composition were

studied. The 90-day laboratory experiment was performed at 22 �C with fish that were initially

24.6 mm (mean total lenth (TL)) and 0.11 g (mean body weight (BW)). Satisfactory fish growth was

attained with all of the diets; however, the largest (p £ 0.05) final size (48.5 mm TL, 1.55 g BW)

and the lowest condition coefficient (K = 1.34) were noted in fish fed the non-commercial starter.

The final survival rates were very high (97.5–100%). Skeletal deformities (in 74 to 92% fish) were

recorded exclusively in fish fed commercial starters. All commercial starters resulted in considerably

higher lipid content and lower ash content than did the non-commercial starter and the reference

diet. This suggests that both these factors might be responsible for body deformities. The present

results proved that only the non-commercial starter is suitable for juvenile E. perenurus rearing

under controlled condition, and that none of the commercial starters can be recommended.

Introduction

The lake minnow Eupallasella perenurus (Pallas), previously known as Phoxi-nus percnurus (see Kottelat 1997) is a tiny cyprinid fish. Small populations of itinhabit small water bodies. In Poland, this species is critically endangered andclose to becoming extinct (Kusznierz 2001). In order to actively protect it,efficient methods must be developed to produce high quality stocking material,e.g., juvenile stages that are advanced in development (Kusznierz et al. 2002;Kaminski et al. 2003).

For many years the larval and juvenile stages of many predatory fish species,including salmonids (e.g. Heinen et al. 1993) esocids (Westers 1979; Wolnickiand Gorny 1997) or silurids (Hamackova et al. 1997) have been fed successfully

Aquaculture International (2005) 13:479–486 � Springer 2005

DOI 10.1007/s10499-005-7899-3

with commercial starters only. However, numerous studies have indicated thatstarters are not particularly useful in feeding cyprinid larvae (Kamler 1992),and starters alone are usually insufficient during the long rearing of the juvenilestages of these fish (Wolnicki et al. 2003). Their application can result in lowgrowth rates (Wolnicki and Myszkowski 1999) poor survival rates (Quiros andAlvarino 1998) and low biological quality, including skeletal deformities(Wolnicki and Myszkowski 1999; Myszkowski et al. 2002).

The aim of the current experiment was to study the usefulness of fourstarters in the intensive feeding of juvenile stages of E. perenurus reared undercontrolled conditions. The starters were evaluated based on comparisons ofgrowth, condition, survival, skeletal deformity, and the analyses of changes inthe chemical body composition of the fish.

Materials and methods

Fish

The study material included juvenile lake minnow specimens aged 2 monthspost hatch. The total length and fresh body weight at the beginning of theexperiment were 24.6±1.2 mm and 0.11±0.02 g, respectively (mean ± SD;n = 50).

These specimens were the offspring of wild fish caught in their maternal pool.Twenty-four hours after capture, they underwent the standard procedure forartificial reproduction with hormonal stimulation (Kaminski et al. 2004). Theeggs were incubated without removing the stickiness in flow-through aquaria ata temperature of 18 �C. The larvae were reared in flow-through aquaria atconcentrations of 40 specimens per dm3 at 22 �C and were fed with live naupliiArtemia sp. (INVE Aquaculture, Belgium).

Experiment procedures

The 90-day long experiment was conducted in nine flow-through aquaria(V = 20 dm3). Each aquarium was stocked with 120 fish. The aquaria weresupplied continuously (0.2 dm3 min�1) with aerated and heated water from arecirculation system with a biological filter. The aquaria were illuminated from08:00 to 21:00 with fluorescent lamps at an intensity of approximately 750 lx atthe water surface. The aquaria were cleaned of excrements and leftover food inthe mornings and evenings.

The water temperature in the aquaria during the experiment was22 �C ±0.5 �C, and the average dissolved oxygen content in the water was66% saturation (range 50–92%). The content of total ammonia, nitrites, andpH were below 0.1 mg dm�3, below 0.02 mg dm�3 and 7.3–7.7, respectively.

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Food and feeding procedures

Three commercial (Carp Starter, Uni Starter, Perla Plus) and one non-com-mercial starter (ASTA) were used during the experiment (Table 1). Eachexperimental group consisted of two replicates. The fish were fed intensively.The initial daily starter ration was 1 g per aquarium; this constitutedapproximately 7.5% of the stock biomass on the first day (feed and fish – freshweight). The daily feed rations were increased to 1.5, 2.5, and 3.0 g peraquarium after 20, 35, and 50 days of the experiment, respectively. Feedingwas performed manually in equal portions at 08:00, 11:00, 14:00, 17:00, and20:00.

In the additional experimental group (without repetitions) the fish were fedwith commercial natural food comprised of frozen Chironomidae larvae(Table 1). Since this group served only as a control group for comparisons ofthe chemical body composition of the fish, it was not fed very intensively. Theinitial daily ration of natural food was 2 g, which constituted about 15% of thestock biomass (feed and fish – fresh weight). The daily ration of this food wasincreased to 3.0, 5.0, and 7.5 g per aquarium after 10, 20, and 35 days,respectively. The fish were fed with Chironomidae larvae at 08:00 and 14:00(days 1–35) or at 08:00, 14:00 and 20:00 (days 36–90).

Chemical composition

The chemical composition of all the diets and the fish bodies in the initial andfinal samples was determined. Homogenized weighed amounts of approxi-mately 50 g were used. The content of dry weight, ash, and total protein weredetermined in accordance with AOAC (1997). The lipid content, after trans-formation into triglycerides, was determined using gas chromatography. Thecarbohydrate content was determined by subtracting the content of totalproteins, lipids, and ash from the dry weight.

Table 1. Diet composition.

Component Carp Startera Uni Startera Perla Plusb ASTAc Chironomidae larvae

Protein (%) 42.23 51.57 54.15 50.48 9.34

Lipid (%) 8.93 7.55 18.12 9.57 1.57

Carbohydrate (%) 32.18 24.92 11.68 25.41 1.05

Ash (%) 9.15 10.32 9.90 9.76 1.35

Moisture (%) 7.45 5.64 6.15 4.78 86.69

Gross energy (kJ g�1) 19.04 19.44 21.96 20.07 3.01

aStarter for cyprinid fish, Aller Aqua, Denmark.bStarter for marine fish, Trouw, France.cNon-commercial starter for cyprinid fish, Polish Academy of Sciences, Gołysz, Poland.

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Fish measurements and the statistical analysis

In order to determine the final total length and fresh body weight as well as thefish condition coefficient, 30 specimens were collected from each aquarium.These were measured and weighed to the nearest 0.1 mm and 0.01 g, respec-tively. All the remaining specimens in the aquaria were counted. The per-centage of specimens with visible spinal deformities was determined for eachaquarium.

The condition coefficient (K) was derived using the following equation:K = 105 � BW � TL�3, where BW is fresh body weight (g) and TL is the totallength (mm).

Since results in duplicates within groups did not differ significantly(p £ 0.05, t-test), it was decided to pool results from the duplicate aquaria.The mean values of the TL and BW as well as the condition coefficient werecompared using Duncan’s multiple range test. The fish survival rate and thepercentage of specimens with deformities were normalized using arcsinetransformation (Sokal and Rohlf 1969). The differences were considered sig-nificant at p £ 0.05.

Results

Growth, condition coefficient, survival, deformities

The fastest fish growth was observed in the group fed with the ASTA diet;these specimens reached a mean of 48.5 mm TL and 1.55 g BW on the final dayof the experiment (Table 2). The fish with the smallest length were noted in thegroup fed Perla Plus starter (41.0 mm TL). The mean body weights in thegroups fed with Carp Starter, Uni Starter and Perla Plus (range 1.21–1.23 g)did not vary significantly.

The values of condition coefficient K in all groups fed with starters differedsignificantly (Table 2). The highest value of the K coefficient was observed inthe group fed Perla Plus (1.73), while the lowest was in the group fed ASTA(1.34).

Table 2. Final characteristics of E. perenurus fed different diets for 90 days at 22 �C.

Diet Carp Starter Uni Starter Perla Plus ASTA

Mean total length (mm ± SD) 43.0 ±2.8b 43.0 ±2.3b 41.0 ±2.9c 48.5 ±4.1a

Mean fresh body weight (g ± SD) 1.23±0.29b 1.28±0.22b 1.21±0.28b 1.55±0.43a

Mean condition coefficient (K ± SD) 1.53±0.10c 1.60±0.10b 1.73±0.12a 1.34±0.09d

Survival rate (%) 99.5a 99.5a 97.5b 100.0a

Deformed specimens (%) 74.0b 89.1a 92.2a 0.0c

In rows, data with different superscripts are significantly different (p £ 0.05).

In the reference group fed Chironomidae larvae, the respective values were 43.6 mm TL, 1.08 g

fresh BW, K = 1.27, 100% survival and 0% deformed specimens.

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The fish survival rate was very high in all groups (Table 2). Only in the groupfed with Perla Plus it was significantly lower (97.5%).

Spinal deformities were not observed in any of the specimens from thegroups fed with ASTA or natural feed, while in the other groups fish withdeformities (mainly in the posterior spinal segment and at the base of thecaudal fin) constituted from 74 to 92% of all the specimens (Table 2).

Chemical body composition

The greatest changes in the chemical body composition of the fish in relation tothe initial values were observed for lipid and ash contents (Table 3).

The final content of lipids in the bodies of fish in the groups fed commercialstarters was greater than it was initially, while in the groups fed ASTA starterand Chironomidae larvae it was lower. The highest lipid content (8.22%) wasobserved in the group fed Perla Plus, which had the highest lipid content. Thelowest content of lipids was noted in fish fed Chironomidae larvae (4.71%) andASTA starter (5.45%).

During the experiment, a greater drop in ash content in fish bodies wasobserved in the groups fed with commercial starters in comparison with theother groups (Table 3).

Water and the total protein contents in bodies of fish from all the groupswere very similar and did not change considerably over the experimentalperiod.

Discussion

In order to achieve high stocking effectiveness, which is especially importantwith endangered species, it is necessary to deliver stocking material of theappropriate sizes and of high quality at the right time (Cowx 1994; Philippart1995). The lack of commercial starters that meet the feeding requirements ofcyprinids has been a serious obstacle in the production, under controlled

Table 3. Initial and final chemical body composition of E. perenurus fed different diets for 90 days

at 22 �C.

Component Initial Final

Carp Starter Uni Starter Perla Plus ASTA Chironomidae

larvae

Moisture (%) 76.41 75.99 74.57 74.27 74.94 76.34

Protein (%) 13.05 12.43 13.48 12.37 13.17 13.26

Lipid (%) 5.53 7.13 6.56 8.22 5.45 4.71

Ash (%) 2.63 1.62 1.66 1.46 2.44 2.47

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conditions, of stocking material of this fish group (Myszkowski et al. 2002;Wolnicki et al. 2003). For the youngest stages of E. perenurus, which are theexceptionally demanding in terms of feed quality (Kaminski et al. 2003;Kaminski unpublished data), the lack of such feed has necessitated feedingthem expensive natural feed that is not always available.

The commercial starters used in the present study for cyprinids (CarpStarter, Uni Starter) and marine fish (Perla Plus) ensured very high survivalrates and sufficient growth rates of E. perenurus juvenile stages. The dailyincrement of total fish length ranged from 0.18 to 0.20 mm, which is consid-erably more than that observed (0.13–0.14 mm) in slightly older E. perenurusjuveniles fed at the same temperature with commercial trout starter (Kaminskiunpublished data). In terms of the total length growth rate among otherjuvenile stages of cyprinids, E. perenurus does not differ from the very slowlygrowing tench Tinca tinca (0.17–0.19 mm day�1, Wolnicki and Myszkowski1998).

In the present experiment, commercial starters caused spinal deformities in amajority of specimens (Table 2). When used to rear juvenile tench T. tinca, thesame feeds caused deformities in nearly all specimens (Wolnicki et al. unpub-lished data). In another study, Carp Starter caused deformities in 37% ofjuvenile crucian carp Carassius carassius specimens (Myszkowski et al. 2002).On the other hand, the current experiment confirmed what previous studies onjuvenile stages of various cyprinid species had indicated that ASTA starter didnot cause body deformities (Myszkowski et al. 2002; Wolnicki et al. 2003).

One of the causes of skeletal deformities might be inappropriately balancedfood components in the feed, including an excess of lipids (Hasan et al. 1997;Rennert et al. 2003). Myszkowski et al. (2002) suggested that skeletal defor-mities in fish might occur when feed contains too little protein in relation to fat.The fact is that in the present experiment, deformities occurred in fish fed UniStarter, which had lower fat and higher protein contents than the ASTA starterthat did not cause deformities, does not appear to confirm this assumption.

Inappropriate proportions of nutritive components in the diet, includingexcess lipids, can lead to excessive concentrations of fat in fish muscles andinternal organs (Garcia-Gallego et al. 1993; Koskela et al. 1998; De Pedro et al.2001). Increased lipid contents and significant, simultaneous decreases inmineral component (ash content) in the fish bodies in relation to initial valueswere confirmed in all groups in which deformities were observed (Table 3). Allof these changes can result from phosphorus deficiency in the fish bodies, whichcan, among other things, lead to excessive fat accumulation and poor skeletalmineralization and deformity (Lall 2002). Since cyprinids do not have acid-secreting stomachs, their absorption of minerals from organic compounds(especially phosphorus) is poor (Roberts 2002). It has been shown that some ofthese compounds, for example phosphatidylinositol, play a key role in pre-venting skeletal deformities (Cahu et al. 2001). However, it cannot be fullyruled out that the fish body deformities noted in the current experiment werecaused by other factors or the synergic impact of many factors. It is known that

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skeletal deformities can also be caused by an excess of fat-soluble vitamin A(Estevez and Kanazawa 1995; Roberts 2002) or vitamin C deficiency (Halver2002; Roberts 2002).

In the current experiment, a high condition coefficient value was noted for allof the groups in which deformities, excessive fat accumulation, and deminer-alization occurred (Table 2). The greater the percentage of specimens withskeletal deformities and the higher the fish body lipid content, the higher themean value of the condition coefficient was in these groups. This indicates thatthe high condition coefficient might be a valuable indicator of the loweredbiological quality of juvenile fish used as stocking material, especially the de-gree of fatness, as, for example, Myszkowski et al. (2002) suggested.

The results of the current experiment indicate that only the non-commercialASTA starter can be used under controlled conditions in the intensive pro-duction of E. perenurus stocking material.

Acknowledgements

This study was supported by a Grant from the State Committee for ScientificResearch No. 6 P04G 055 21.

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