EXPERIMENTS ON FIRST-FEEDING OF CARP FRY WITH ALEVON AND FREEZE-DRIED FISH

M. von Lukowicz

Bavarian State Institute for Fishery, Starnberg, Federal Republic of Germany

ABSTRACT

The mass production of advanced carp fry (C_A) under hatchery conditions would be much easier and more economical if artificial feed could be applied in the first-feeding period of fry (C_O), instead of living food animals. In 1975 and 1976 experiments were carried out to replace Artemia with Alevon and minced freeze-dried carp meat.

The exclusive application of the artificial feeds from the first day onwards resulted in higher losses and a higher percentage of body deformations in the experimental carp as compared to the Artemia fed control fish. A successful change from living food to artificial feed was only possible for those carp which had received Artemia for at least four days.

RESUME

La substitution d'aliments artificiels aux aliments vivants permettrait la production en masse d'alevins de carpes, tout en la rendant plus économique. En 1975 et 1976, des efforts ont été faits pour remplacer les nauplies d'Artémia par “Alevon” ou par chair de carpe séchée en évaporateurcongélateur.

L'alimentation consistant, dès le début, exclusivement d'aliments artificiels a donné des pertes plus importantes et des déformations plus considérables par rapport aux carpes nourries d'Artémia. Après avoir utilisé Artémia pendant quatre jours au minimum, la substitution d'aliments artificiels aux aliments vivants donne des résultats acceptables.

1. INTRODUCTION

Under the climatic conditions of Central Europe three years is the usual period for the production of marketable carp in ponds. It would be advantageous for economic reasons and for the reduction of risks, to shorten this period to two years. This is only possible if the growing season of the second year can start with C₁ (carp after the first summer) of a minimum size between 100 and 150 g. This size is normally not available, because under natural conditions the spawning of carp takes place well into the growing season.

In the hatchery the reproduction of carp can be advanced to the beginning of spring. However, the just hatched fry (C_O) cannot be released into ponds immediately. There is usually a shortage of natural food and sudden changes in temperature can cause total losses. Thus the fry must be kept and fed in tanks or aquaria with warm water.

For artificial breeding and rearing useful methods have been developed. When rearing carp in a hatchery the main problem is the feeding of the fry the first few days after yolk sac resorption. C_O in contrast to trout fry, cannot be started successfully with pelleted feed. Until now the earliest stages of the fry have to be fed with plankton or Artemia nauplii.

Although C_O can be reared successfully using plankton, the question of when to supply animals for feeding and in what quantities remains problematic. It is not always easy to obtain plankton in a suitable size, particularly if the carp are to be reproduced in early spring or winter - long before their natural spawning season. Furthermore there is a risk that viruses and parasites are introduced into the hatchery with the plankton.

Thus it seemed at first more promising to feed with Artemia larvae which can be bred in containers and are not subject to seasonal availability. However, recently there has been a scarceness of Artemia eggs, and they also were of poor quality. The hatch ratio is often barely above 20%. This means increased labour expenditure and costs, and it seems doubtful whether the feeding of C_O with Artemia larvae can remain an economic proposition in the future. The supply of good Artemia egg material is anticipated to remain in a bottle neck situation and this represents a considerable factor of uncertainty for the controlled rearing of carp on a large scale.

These factors form the background for the efforts that are made to replace living food for fry by other feeds (artificial feeds), or to change over as early as possible to these feeds after the first feeding with live animals.

2. EXPERIMENT ON FIRST FEEDING WITH ALEVON IN 1975

In an experiment performed in 1975, C_O received the freeze-dried, moist feed Alevon made by the Herta KG company with 51% crude protein (Table 1) besides Artemia. It was not possible to rear the fish using Alevon exclusively. Very high losses occurred in the 30 days of the experiment and individual growth was minimal (39 mg). The longer the first feeding with Artemia lasted, the smaller were the losses. It was justifiable to change over to Alevon after four days (losses: 9.1 %). Amongst the fish fed exclusively with Artemia the losses were below 5% and the fish grew more quickly and evenly than those in the other test groups.

Some of the advanced carp (C_A = small fingerlings) were kept a further six weeks and fed amongst other things, with Alevon (freeze-dried and fresh). The growth of those fish which had been fed for a short period (4 days) with Artemia and later with Alevon, was not inferior to that of the fish which had been fed with Artemia on all 30 days of the rearing period.

Losses were between 0 en 4%. The feed conversion ratio (FCR) of freeze-dried Alevon was 1.73 – 1.77. Only the carp fed exclusively with Alevon fell behind. In this group, in particular, those fish survived which had provided themselves with “natural food” through cannibalism.

Feeding with Alevon is very simple technically. If it is freeze-dried, the feed can be spread easily onto the water surface, where it floats briefly and then slowly sinks. If it is fed as moist feed it can be stuck to the aquarium walls at water level, in clumps. Both forms of Alevon were readily eaten by C_O and C_A. However, the feed dissolved quickly and clouded the water, Fungi developed on the remains on the aquarium bottom and attacked the fish. The walls became covered with a slimy layer of bacteria. Feeding with Alevon required considerably more cleaning work than feeding with Artemia.

3. EXPERIMENT ON FIRST-FEEDING IN 1976

3.1 Feeds

Since Alevon had proved unsuitable for first-feeding of carp, an experiment was performed in 1976 whereby C_O were fed with minced carp meat. The intention was to adapt, as far as possible, the proportion of amino acids and other substances in the starter feed to the body composition of the experimental fish. Three different kinds of feed were available: total body of carp (CT), inner organs of carp (CI), and carp musculature (CM). The feeds were freeze-dried, this being a method through which the feed ingredients are preserved. At the beginning of the experiment the pellets were 0.2 mm in diameter. From the 7th day onwards coarser feed (0.3 mm) was used. Artemia larvae were used as a control and the subsequent feed was Alevon.

3.2 Experimental methods

The fish for the experiment hatched on June 13, 1976 in incubator glasses and were put into plastic aquaria on June 15 in batches of 500, each aquarium containing 4 litres of water. The fish were 6–7 mm long. The aquaria were constantly supplied with water at a temperature between 21 and 23°C. The water supply was only turned off during feeding. In spite of being diminished by the feed remains, the oxygen level did not sink below 5 mg O₂/1, with the exception of an accident (see below). The water flowed out through specially attached teasieves and overflow tubes.

For first feeding the experiment was divided into the following groups:

Group A : 9 days Artemia control

Group B : 3 days Artemia, 6 days freeze-dried carp

Group C : 1 day Artemia, 8 days freeze-dried carp

Group D : 9 days freeze-dried carp

The groups B, C and D were further divided according to the type of freeze-dried feed into the variants CT, CI and CM. The group A and each variant of groups B, C and D included two experimental aquaria respectively. From the 10 the day onwards all fish received Alevon.

The first feeding experiment started on June 16 and lasted 30 days until July 15. The C_O were fed seven to eight times daily. Only towards the end of the experiment the number of feeding times were occasionally reduced to four or five. It was necessary to provide generous quantities of feed as C_O are only able to perform short swimming movements to snatch bits of feed. The feed remains caused the aquaria to become dirty quickly and had to be siphoned from the aquarium bottom daily. The aquaria were changed twice a week and thouroughly cleaned. This avoided the growth of fungi, as occurred in 1975.

3.3 Results

The fish were counted for the first time on the 9th day (June 24). The losses up to this point can be seen in Table II. Although the losses were slightly higher in group D, the differences between the groups are not remarkable. Heavier fish losses started on the 10th day in group D and the 12th day in group C, whilst groups A and B had no losses at all. The origin of the freeze-dried carp feed did not have a proved effect on the losses.

The differences in growth were more striking. Already a few days after the start of the experiment it could be seen with the naked eye that the more Artemia the C_O were fed, the larger their size. All fish in the experiment readily accepted the feed offered, right from the start. Only in groups A and B, however, constant and even growth could be observed. Consuming their yolk sacs the C_O in groups C and D at first grew and then stopped growing.

On June 30 a technical fault interrupted the supply of water for several hours during the night. In several aquaria carp died from lack of oxygen. The remaining fish were counted again and left in their aquaria. This resulted in varying stocking numbers from July 1 onwards which were then used as a basis (see Table 3). However, the stocking density could not have much influenced the further course of the experiment, as the C_O were not crowded together anyway and neither oxygen nor food quantities were limiting factors for the purposes of rearing. Furthermore as has already been mentioned, in group C and in particular in group D, many fish had already died before the accident.

In the second half of the experiment the losses of those carp which had received none or very little living food in the first few days continued. Table 3 shows a clear gradation. The losses in group B were between 8.5% and 20.7%, in group C between 57.4% and 60.5%, and in group D between 69.6% and 81.1%. In group A only 1.5% of the fish died. There were differences between the variants within a group but these cannot be attributed to the influence of the respective freeze-dried feed since they did not show accordance in the comparison. A consistent positive or negative result in all the experimental groups was not obtained for any of the three freeze-dried carp feeds.

The same applies to the final weights shown in Table 4. For simplification and a clearer overview, the replicates are combined here. As can be expected, the best growth was found in the carp of group A fed for 9 days with Artemia. Group B was already far behind as far as length and individual weight were concerned. But it was clearly contrasted with groups C and D in which the fish had on average grown almost equally. Furthermore it can be seen from Table 4 that there was a large range in growth within each group, whereby the fish in group A grew most evenly.

After finishing the actual first-feeding experiment the greater part of the C_A from groups A, B and C were kept for another three and a half months for further observation. The distinctions made between the variants of a group (CT, CI, CM) were no longer applied. The fish in group D were no longer fit to be kept for further rearing as a result of their high losses and poor physical condition. The C_A received dry feed compounds four to five times daily to satiation.

With regard to the development of the fish, the following can be seen in Table V:

After approximately two months (Sept. 10, 1976) the C_A in group A (9 days Artemia for their first-feeding) had the best growth with the lowest losses. The fish in group C (1 day Artemia) were heavier on average than the fish in group B (3 days Artemia). However, there had been heave losses in group C which had struck the smallest fish in particular., causing the average individual weight to rise.

This trend increased further in the next one and a half months. The C_A in group C were almost twice as heavy as those in the other groups at the end of the experiment. Even group B had overtaken group A in individual weight. Yet whilst there were no losses in group A during the last period of the experiment, in groups B and C total losses were 81.6% and 92.8% respectively. The reason for this was amongst other things cannibalism, which had developed earlier in the groups with less adequate first-feeding and continued to a considerable extent later in spite of repeated daily feeding ad libitum. Large differences in growth also encouraged cannibalism. At the end of the experiment the individual weight of all fish varied between 1 g and 80.5 g, the largest C_A belonging to groups B and C. The loss rate and the average weights show that given the inadequate first-feeding, only those fish in groups C and B with the strongest constitution survived and, partly as a result of cannibalism, grew correspondingly well.

After the 30 day advancing period, gill cover atrophia which was mostly combined with skull deformation and deformation of the backbone could be observed to an increasing extent. The deformations were clearly related to the feed quality during the first-feeding period. As can be seen from the percentages in groups A and B in Table 6, this relation became progressively clearer. The decline in the proportion of deformations in group C towards the end of the experiment is again a result of the high loss rate of the small fish which were almost all deformed.

4. DISCUSSION

In the reported first-feeding experiments it was not possible, to replace Artemia larvae with another food as first food for C_O. Although it can be assumed that the freeze-dried carp feed eliminated an imbalance of amino acids in the nutrition, the fish in the experiment showed heavy losses and unsatisfactory growth. In general the lack of digestive enzymes, which are normally obtained through living food animals, is made responsible for the failure of artificial feeds in the first-feeding of carp fry.

In the experimental groups without or with little living food (C,D), the differences in individual growth were very noticeable. Some of the fish did not increase in length after consuming the yolk sac, and it is amazing that these fish survived the experiment. On the other hand, the length and weight of other C_O approached the average values of carp which had been fed Artemia for several days during the first-feeding (A, B), or even greatly exceeded them.

As the experimental methods did not include the rearing of individual fish separately, it is hardly possible to decide if cannibalism can be the sole explanation for this, or if perhaps some fish did in fact manage without enzymes obtained from food animals. In any case, cannibalism occurred principally in the carp which received less Artemia. Even with adequate feeding it still continued in as much as it was made possible by individual growth differences and carp being crowded together in a narrow space.

At first, in spite of wrong nutrition, the C_O of groups C and D suffered few losses. The critical phase occurred ten to twelve days after the yolk sac had been completely consumed. The quality of the first feed had an effect over a long period of time, even long after the fish had become used to artificial moist or dry food. Lack of natural food in the first stages caused losses for a long time. In the long run, only those fish which were strong and well fed, whether with Artemia or other carp, were able to survive. Abnormalities were more frequent and stronger the less Artemia had been fed during the first-feeding period.

If one compares the results in 1975 and 1976 - both experiments lasted 30 days - first-feeding with Alevon and first-feeding with freeze-dried carp feed produced equally poor results with losses up to 80% or more. The immediate change to Alevon after previous first-feeding with Artemia for three days, brought better results than the transitional feeding with freeze-dried carp organs. The losses of those fish which had been fed exclusively on Alevon were less and the final weights on average twice as high (115 mg/per fish as opposed to 40–67 mg/per fish). The control carp in 1976 (9 days Artemia, 21 days Alevon) attained an average weight of 265 mg which was higher than the control carp in 1975 with 134 mg (30 days Artemia). In both cases the loss rate was low. The difference in growth occurred because the supply of Artemia was inadequate at the end of the experiment in 1975 and Alevon being freely available could be given to the point of satiation.

According to the experiences of both these experiments, it is quite safe to change the nutrition of C_O fed for approximately one week on living food to Alevon.

Although not referenced in the text a list of references is attached.

5. REFERENCES

Albrecht, M.L., 1973 Zum Entwicklungsstand der Trockenmischfuttermittel für die industriemässige Karpfenproduktion in der DDR. Z. Binnenfischerei DDR, 20: 352 – 356.

Appelbaum, S., 1977 Geeigneter Ersatz für Lebendnahrung von Karpfenbrut? Arch. FischWiss., 28: 31 – 34.

Hillenbrand, M. and H. Liebenau, 1976 Ergebnisse der Entwicklung und Erprobung von Trockenmischfuttermitteln für die industriemässige Aufzucht von Karpfenbrut in Warmwasseranlagen. Z. Binnenfischerei DDR, 23: 194 – 215.

Kainz, E., 1974 Fütterungsversuch mit Karpfenbrut (Cyprinus carpio L.). Oesterr. Fischerei 27: 21 – 34.

Kainz, E., 1976 Weitere Versuche zur Aufzucht der Brut des Karpfens (Cyprinus carpio L.) mit Trockenfuttermitteln. Oesterr. Fisherei, 29: 58 – 62.

Lukowicz, M. von, 1976 Anfütterung von Karpfenbrut. Fischer und Teichwirt, 27: 68 – 69.

Mires, D., 1976 Primary Nursing of Carp Fingerlings in Tanks. Bamidgeh, 28: 18 – 24.

6. TABLES

Table 1. Feeding, losses and final weight of C_O-A after 30 days in feeding experiment 1975.

Table 4. Lengths and weights after 30 day first-feeding in feeding experiment 1976 Explanations see Table 2 and text

Table 2. Losses from the start to the 9^th experimental day in feeding experiment 1976.

Group A : 9 days Artemia - Control

Group B : 3 days Artemia, 6 days freeze-dried carp

Group C : 1 day Artemia, 8 days freeze-dried carp

Group D : 9 days freeze-dried carp

Variants: CT = Total body of carp

CI = Inner organs of carp

CM = Musculature of carp

Table 3. Losses from the 16th to the 30th experimental day in feeding experiment 1976 Explanations see Table 2 and text

Table 5. Growth and losses of C_A after the advancing period in experiment 1976

Table 6. Abnormal carps as % of survived specimen in experiment 1976