P. Ghittino
Fish Disease Laboratory, Torino, Italy
ABSTRACT
Catfish farming has started in Italy using the methods used in the U.S.A. At present Italy produces about 1200 tons of black bullhead (I. melas) per year. This is expected to increase when channel catfish (I. punctatus) imported in 1975 is taken in production.
During 1978 successful artificial reproduction of black bullhead has been carried out using the pond method of spawning, egg incubation in paddle troughs and feeding of fry with paste feed and later with crumbles and pellets.
Some consideration and biological risks of catfish farming are briefly mentioned.
RESUME
La pisciculture des silures a été commencée en Italie par le recours à des méthodes développées aux Etats-Unis. A l'heure actuelle, la production annuelle d'Ictalurus melas en Italie s'élève à 1200 tonnes. L'introduction d'Ictalurus punctatus a permis de réaliser une augmentation de la production en pisciculture.
La reproduction d'I. melas en 1978 a été effectuée en étangs, suivie par incubation en bacs et alevinage avec aliments pâteux sous forme de mie ou de granulés. Quelques techniques d'élevage et leurs risques biologiques sont décrits.
Catfish farming has started in southern areas of the USA and production as well as production methods used are taken as an example in other countries, particularly in Italy.
Up till now catfish species were considered extremely harmful and predacious in Europe. Particularly in traditional extensive carp pond farming, catfish (brown bullhead, Icatalurus nebulosus) is a pest inducing a great decrease in fish production especially among useful secondary species such as e.g. tench. Therefore, it was tried to destroy catfish rather than to rear it. However, recently culture of catfish has started and Jugoslavia imported the channel catfish (Ictalurus punctatus) from USA in 1970, followed by Italy in 1973. Apart from these two species, there is the “native” species reared in Italy, imported in the past and perhaps even interbred, i.e. the black bullhead, Ictalurus melas. Moreover, also Silurus glanis, a european native species, is reared, mostly for stocking purposes. This specific subject will be illustrated by other speakers during this Meeting.
The culture of catfish in USA and in Italy represent a considerable fish husbandry operation with a production of 35 000 and 1200 tons/year respectively. The methods used are the same in both countries and have been duly illustrated (see ample references in Ghittino 1969, 1972) as well as in a previous EIPAC Meeting (Sneed, 1973). As far as Italian catfish farming is concerned, I may suggest to examine the paper by Ghittino & Vigliano, 1975. This paper intends to give a short survey of the actual situation in catfish farming in Europe, and more particularly in Italy since this country is showing a major interest in commercial culture of catfish.
The main species cultured in Italy is the black bullhead, I. melas. The brown bullhead, I. nebulosus, is the most interesting species for European carp pond farming, but its trade as live fish is forbidden in Italy.
During 1975 some more channel catfish fingerlings were imported from Alabama, USA. These should reach sexual maturity in the course of this year and allow first artificial reproductions. Black bullhead and channel catfish seem to be the only species suitable for large operations in intensive fish farming for direct consumption. In Italy minor interest is being paid to the farming of other species of catfish, i.e. Silurus glanis.
Until 1977 young black bullheads were obtained from spontaneous reproduction in fishponds and in 1978 success has been obtained with artificial reproduction; catfish eggs were spawned in nests, following the “pond-method”, i.e. in ponds with minimum vegetation to force fish pairs to spawn in the nests. Eggs were then transferred into paddle troughs, fed with water heated by solar irridation. Fry hatched regularly, as in case of channel catfish. After yolk sac absorption, the fish was fed on a paste-feed, similar to the feed used in eelfeeding. As expected, all methods given for artificial reproduction of channel catfish can be applied for black bullheads.
These artificial reproduction methods, if slightly improved and put into practice to a higher extend, will give a regular and sufficient supply of fingerlings for catfish farming.
The first feeding of catfish fry takes place both in ponds containing zooplankton (Daphnia) and through paste-feed, similar to the feed used in eelfarming. Later on, as soon as fingerlings are obtained, crumbles are fed, followed by pellets, similar to the feed used in trout farming. Crumbles are fed by hand or by automatic feeders, type Scharfling, and pellets by very simple demand feeders. Average conversion rate amounts to 2 : 1, this rate is economic, since price of catfish obtained is similar to trout prices.
Other fish farming operations (grading and fishing) are secondary to maintenance of optimum conditions in the fish ponds. Water supply originates usually from a well and this avoids presence of parasitic diseases. It is essential, however, that the water from the well passes first through a basin in order to improve its quality: loss of inert gas (which may give cause to gass disease) and increase of the dissolved oxygen content. Especially during the summer season, the water qualities should be checked regularly in order to guarantee correct pH values (approaching neutral values), low ammonia compounds contents and proper phytoplankton characteristics. In this respect, it is moreover essential that a bloom of green algae prevails and a minority of brown algae exists. The installation of water aerators will guarantee a good oxygen supply in the ponds and will avoid stagnation of the water as well. Hence, it will be possible to increase the fish stocking in the ponds.
Fish ponds must be dried and cleaned radically during the winter season, since otherwise environments will deteriorate due to accumulation of organic materials (faeces, feed rests).
It is fairly difficult to calculate the density of catfish in ponds, but is seems that we may rely upon 400 – 600 gr of fish/m2. The presence of natural food in the ponds creates the possibility to use even not perfectly balanced pellets in catfish feeding.
Management of a catfish farm is generally rather simple and involves only exceptional fishing for thinning, grading, selling etc. purposes. Moreover fishing is simplified by the use of demand feeders or fish pumps installed in the outlets of drained ponds to catch the fish crowded there.
Catfish in Italy is marketed alive; transport of live fish is effectuated by trucks equipped with containers containing oxygenated water. Programs are being studied to market also processed catfish (gutted, filleted, deepfrozen, smoked, cooked etc.) by various cooperative associations. These techniques will be developed further and will become necessary when catfish production increases and at the moment channel catfish can be marketed next to black bullhead.
The major biological risk to be considered are the environmental diseases, which can condition other diseases caused by different factors.
I am suspecting that the Ictalurus melas, also in Italy, can be affected by the diseases caused by Herpesvirus, known as Channel Catfish Virus Disease. In one case, during 1978, I noticed pathological injures characteristic for this disease and we isolated a viral agent, which produced syncytial multinucleated cells, typical of herpesviruses. The exact identification of this viral agent is yet to be performed however.
Diseases, which are considered bacterial, such as Columnaris Disease, Bacterial Septicemia by Pseudomonas or Aeromonas, appear to be linked with harmful environmental conditions, such as cold spells, handling, dirty fish ponds etc.
The parasitosis, encountered most frequently, was the one caused by Trichodina sp., but so far the most feared Ichtyophtirius multifilii has not been traced. By the way, it seems that parasitosis may have caused the severe mortality in channel catfish in Jugoslavia. Probably, this can be connected with the fact that channel catfish seems to be more susceptible towards this parasite than the black bullhead.
Ghittino, P., 1969 Piscicoltura e ittiopatologia Vol. 1o. - Pisicoltura 'Ed. Riv. Zootecnia, Milano 1969: 233 – 248.
Ghittino, P., 1972 The diet and general fish husbandry. In: Fish Nutrition by J.E. Halver, Academic Press: 609 – 618.
Ghittino, P. and E. Vigliani, 1975 Difficoltà di decollo della pescigattocoltura italiana (Riv. It. Piscic. Ittiop., A.X.N. 2:45 – 51.
Sneed, K.E., 1973 Channel catfish culture methods. EIFAC/T25, Workshop controlled reproduction cultivated fishes: 164 – 173.
