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The Government of Yugoslavia has requested the assistance of the United Nations Development Programme and the Food and Agriculture Organization of the United Nations, in setting up a project entitled Managing the biological resources of the Adriatic Sea-Aquaculture of Salmonids (YUG/83/011).

As part of the preparatory assistance to the project FAO assigned Mr D. Edwards as consultant from 13 September to 3 October 1984 to evaluate and review the results of experiments on brackish/seawater cage culture of salmonids done to date; and to conduct a reconnaissance of potential sites for salmonid cage culture on the Yugoslav coast.

In the course of this survey, all the currently operating commercial sea bass and sea bream units were also visited.


During the past few years, several pilot, fish farms have been built on the Adriatic coast of Yugoslavia with the objective of proving the feasibility of brackish or seawater cage culture of fish. To date, most financial support from the Socialist Republics of Yugoslavia and international organizations has centred on culture of indigenous marine species, especially sea bass and sea bream. However, since 1980, experiments on salmonid culture have also been proceeding. These experiments were at first confined to rainbow trout kept in cages in brackish waters of the estuary of the River Krka. Later, trials were extended to include production of coho salmon both at brackish and seawater sites in the same estuary, and to commercial production of rainbow trout in brackishwater outside the Krka area. Application for international support for this work was first made in 1982 (UNDP project document YUG/83/003), but doubts about the feasibility of salmonid culture in the Adriatic and the scale of the proposed investment caused some postponement of a decision on funding.



All experiments and commercial trials have been carried out by scientists and technicians of the Rudjer Boskovic Institute or under their guidance. The Rudjer Boskovic Institute (Director Dr Sergije Kveder) is an independent research organization with its head office in Zagreb, where its Centre for Marine Research is also located. The Centre's director is Dr Zdenka Konrad. Two of the Centre's divisions, the Aquaculture Laboratory (Chief Dr Emin Teskeredzic) and the Physico-Chemical Laboratory (Chief Dr Marco Branica) collaborate on the salmonid culture programme, with Dr Branica designated director of the project and Dr Teskeredzic co-director. Most of the day-to-day operation of the research effort is handled by Dr Teskeredzic.

The aquaculture and physico-chemical groups at the Centre have a highly qualified staff of veterinarians and scientists specializing in water chemistry, plankton studies, chemical analyses of fish flesh and feedstuffs, etc. They provide a contract monitoring service on fish health and water quality for many freshwater carp and trout farms in Yugoslavia, visiting clients' units once a month to take and analyse samples. The Aquaculture Laboratory also maintains a field station with a resident staff of four at Martinska, opposite the town of Sibenik, on the River Krka estuary. It is from this laboratory that experiments in brackish/seawater cage culture of salmonids have been done.


NOTE: The data, graphs and tables used in this report will be formally published by scientists of the Rudjer Boskovic Institute at a later date.

2.2.1 Rainbow trout


About 1 000 fingerlings averaging 50 g were stocked in one floating cage with net size 2 × 2 × 2 m on 27 March. The cage was moored in brackish water at Skradin in the 25 km long River Krka estuary (Fig. 1). Fish were fed on imported dry pellet (Trouw Italia) four times daily by hand in amounts between 1 and 2.5 percent of body weight following feeding tables. After two months, when the average size of the fish had increased to 150 g, they were transferred to a larger 4 × 4 × 4 m cage at the same site. This cage was of home-made, timber-framed construction, with 0.5 m wide walkways on each of its four sides surmounting floats of expanded polystyrene sheathed in PVC sheet. The same cage design was subsequently used in all experiments in the Krka estuary.

All materials are available locally, and the cost of each cage complete with net is only about 100 000 dinars (approximately US$ 600, at 1984 prices).

Throughout the experiment, all fish were weighed (in bulk) and counted once a month. The experiment ended in May 1981, when all fish were slaughtered. Mean weight at slaughter was 1.5 kg, and total mortality during the experiment was 15 percent.

Throughout the experiment, measurements of water salinity and temperature were taken every week at Skradin and at two other sites in the Krka estuary (Fig. 1, Tables 1 and 2). This monitoring was continued in subsequent years, and was extended to include measurements of pH and oxygen concentration (Figs. 2, 3 and 4, Tables 1, 2, 3 and 4) and to a fourth site (St. Nikola) at the mouth of the estuary (Tables 5 and 6, Fig. 1). Phytoplankton was also sampled (Table 7).


Encouraged by both the survival and growth of fish in the initial experiment, larger trials were undertaken in 1981–82. This time the Rudjer Boskovic Institute worked in collaboration with the Emona and Sljemeriba commercial state freshwater trout farms. These farms provided rainbow trout fingerlings and dry food. At the end of the experiment they sold the fish, and the financial returns went to them.

A total of 20 000 fingerlings of 100 g average weight were stocked in ten 4 × 4 × 4 m cages at Skradin in May, and grown until May 1982. Because of the large number of fish, it was only possible to weigh and count them all at the beginning and end of the experiment. In between, three 20 kg samples were taken from each cage each month for estimation of average weight. Fish were fed at water temperatures up to 24°C, though feeding was restricted above 20°C. Mortality during the one-year experiment was about 20 percent, and at slaughter the fish averaged 1.8 kg in weight.


Having proved in the previous two years that brackishwater cage culture of rainbow trout was possible in Yugoslavia, and being very satisfied with growth rates obtained, the Rudjer Boskovic Institute extended its experiments in two directions. One was to investigate the possibility of producing coho salmon (see below), and the other to quantify some of the variable parameters associated with this type of rainbow trout culture. The variable chosen for study in 1982–83 was size of fingerling at the time of transport from fresh- to brackishwater.

Fingerlings were again obtained from the Emona hatchery, but this year experiments did not start until 6 October. Fish for the experiment were selected from two age groups, one ten months old and the other 22 months old, so that a wide spread of fish size was available. From the 10-month old fish, 500 individuals were selected averaging 84 g and 500 averaging 118 g, whilst from the 22-month old fish, 50 kg of fish averaging 197 g (254 fish) and 50 kg averaging 301 g (197 fish) were used. Each size group was divided in two and stocked into two cages at Skradin, i.e., four sets of two replicates: a total of eight cages. Additionally a further 285 contemporaries of the 10-month old fish, averaging 125 g, were stocked in a ninth cage on 6 January 1983 (Table 8). Feed was minced wet fish (sardine and bluefish) with added vitamins, minerals and binder. The food was given twice daily, 70 percent in the morning and 30 percent in the afternoon. Fish were sampled as in the 1981–82 experiments until 6 June 1983, when all fish were weighed and the majority slaughtered (Tables 9, 10, 11 and 12, Figs. 5 and 6). However, 100 fish from each group were pooled and kept in two cages for further growth (Tables 9 and 12). The survivors of these fish were still alive at October 1984 at which time they were mature and held upstream from Skradin in freshwater as brookstock. Slaughtered fish were sold by the Institute at a price of Din 250/kg, but the cash obtained did not cover the costs of the experiment because so few fish were grown.

The Institute scientists feel that this experiment was useful in quantifying growth rates in rainbow trout from different stocking sizes in brackishwater. This will in future allow them and private farmers to plan the timing and average weights of their production to suit their markets.

Growth of fish in brackishwater at Skradin is compared with that of their contemporaries held at the freshwater hatchery in Figures 7 and 8.


The variable chosen for study during the 1983–84 season was fish density at the time of stocking into cages. Fish came from the Novo Mesto hatchery. The history of the fish is shown in Tables 13 and 14. A total of 8 000 fish of average weight 32 g left the hatchery by road for Skradin on 6 October 1983, but an oxygen stoppage in one of the transport tanks resulted in 2 000 mortalities during the journey. Subsequently 2 500 fish from the same stock were grown on at Novo Mesto to compare performance in fresh- and brackishwater.

On arrival at Skradin, the surviving 6 000 transported fish were stocked into four cages and grown for two months to an average size of 133 g (Table 15). At this time, surviving fish in brackishwater totalled 5 915, weighing 787 kg. These were divided into four groups weighing a total of 50, 100, 200 and 300 kg, one group occupying each cage (Table 16). Fish remaining after this re-distribution (137 kg) were stocked in a fifth cage.

Fish were fed and sampled as in the previous year until the end of May 1984, when all fish were slaughtered. Numbers, average and total weights of fish in each cage were as follows:

The50kg group returned349fish, averaging 765 g, total267 kg(4 kg/m3).
The100kg group returned755fish, averaging 737 g, total557 kg(9 kg/m3).
The200kg group returned1 486fish, averaging 707 g, total1 051 kg(16 kg/m3).
The300kg group returned2 052fish, averaging 650 g, total1 335 kg(21 kg/m3).

Mortality in all groups was low (about 5 percent). Nets were not cleaned during the experiment, and were reported to be in a very dirty condition by the end of May. Fish in the most densely stocked cage were showing some signs of oxygen distress at the time of harvest. Conversion of the wet food was about 4.5:1 (approximately equivalent to 1.5:1 on a dry weight basis).

It was concluded that an initial stocking density of between 200 and 250 kg per 4 × 4 × 4 m cage is optimal for production of 1 t of rainbow trout per cage over a four-month period.

Mean growth of fish held at Skradin is compared with their contemporaries kept in freshwater at Novo Mesto in Figure 9. Clearly, an enormous advantage in growth is to be gained by holding fish in brackishwater over the winter months.

Chemical composition of meat from trout grown in brachishwater was also compared with that of meat from fish grown in freshwater (Table 17). With the exception of a slightly higher water content in freshwater fish, no significant differences were found.

2.2.2 Coho salmon


About 10 000 eyed coho salmon eggs were brought in from the USA (Fish Pro Inc., 3100 S.E. State Highway, Port Orchard, WA 98366). They arrived on 24 February and were accommodated in the Institute's quarantine hatchery at Gracanski, only 5 km from the centre of Zagreb. The eggs and resulting fry/parr stayed at this hatchery until 25 November 1982, when they averaged 18.6 g (Table 18). They were then split into two groups, one of which (comprising 2 500 fish) stayed at Gracanski. The other 7 500 fish were moved to a larger freshwater fish farm at Dvor pri Zuzenbergu (Table 19). Unfortunately, Dvor suffered from an outbreak of furunculosis while the coho parr were there, and approximately 70 percent were lost. Average weight of surviving fish on 29 September 1983 was 122 g. At Gracanski, however, survival was very high (circa 99 percent) and on the same date these fish averaged 126 g (Table 20). All fish had smolted.

The surviving 4 800 smolts were transferred to Skradin on 29 September 1983, where they were placed in 6 cages (Tables 21 and 22). Sampling was as above for rainbow trout, but food was a mixture of commercial dry trout pellet (Trouw Italia) and minced fish. This was given in two rations, 70 percent in the morning and 30 percent in the afternoon.

In March 1984, one cage was moved about 15 km down the Krka estuary to a site at its mouth (St. Nikola, see Fig. 1), where the hydrology is far more typical of the open Adriatic coast of Yugoslavia (Tables 5 and 6). At this time fish averaged 680 g. Staff were inexperienced in towing cages containing fish, and the operation was carried out too quickly, resulting in the fish de-scaling. Antibiotics were administered with feed, but some 35 percent of fish died within 10 days of towing. However, thereafter growth of coho salmon at the St. Nikola site was faster than at the brackish site at Skradin. Fish were slaughtered at the end of May 1984, by which time the fish held at St. Nikola averaged 1 200 g, but those at Skradin only 900 g. Altogether a crop of 4 000 coho totalling 3.5 t was harvested. Of these, 300 kg were sold to restaurants at a price of Din 1 000/kg, 300 kg to institute personnel at Din 500/kg, 300 kg were given to staff and others, and a little is still frozen. The bulk of fish was sold to a state fishery company for Din 700/kg. Profits accruing to the Institute more than covered experimental costs.


Some 15 000 eyed eggs were imported from the same source on 16 January 1983. They were first quarantined at Gracanski hatchery and later moved to Novo Mesto fish farm. Growth of these fish until 28 December 1983, when they averaged 25 g is shown in Tables 23 and 24. On 1 September 1984 they averaged 90 g, and had smolted. These fish will be transported to the sea during October 1984. New cages are being constructed to house them. They will be 10 × 10 × 8 m deep, and 5 000 fish will be stocked per cage. Fish will go first to the brackish site at Skradin for acclimatization, then after one month they will be moved to the more saline site at St. Nikola.


This year, coho eggs were imported earlier (in December 1983); 25 000 eyed eggs went first for quarantine to Gracanski. Resulting parr were transferred to a new state trout farm at Knin on 5 June 1984. At the end of September, when the consultant saw them, there were reported to be 23 456 fish remaining, averaging 40 g (though they looked bigger than this). Many of the fish were smolting, and will go to sea during October.


The Rudjer Boskovic Institute plans to extend its own activities both in scale and geographically, and to encourage further the entry of small private farmers into brackish/seawater cage culture of salmonids.

2.3.1 Rainbow trout

In October 1984, 20 of the Institute's own cages will be stocked with rainbow trout at Skradin. In addition, 20 cages will be placed at a new brackishwater site at Crikvenice, south of Rijeka (Fig. 10). Scientists from the Institute have previously measured physico-chemical characteristics of the water in this bay (Table 25), which is a little more than 1 km long, has an average width of 250 m and depth of 25 m. It receives large inputs of fresh water at about 10°C from short spring-fed streams, some of which were used until the second world war to provide power for milling corn. Road access is very good, and there is a single dwelling whose occupant, Mr Ivan Car, will assist with the work and surveillance.

It is planned to stock 250 kg of 80–100 g trout in each 4 × 4 × 4 m cage. Feeding will be with wet feed in ten cages and dry feed in the other ten, the same quantities (on a dry weight basis) being given to all cages. The wet feed will be made up freshly on site; the dry feed will come from the companies V May (Bjelovar) or Sleme (Zagreb). The first experiments will start in October and finish in February, when a new production cycle will begin. It is expected that rainbow trout production at the site will be able to continue all year round. The plan is to produce initially about 26 t of trout. Additionally, 7 t of mussels will be grown in hanging culture. The projected return is Din 15 million.

Finance for the experiment (Din 12 million) has come from the Veterinary Station, Crikvenice, several banks and industrial concerns.

If the experiment works, it is planned to produce some 100 t at Crikvenice in 1985.

Private involvement. In March 1984, two private farmers, Mr Predrag Murisic and Mr Ivo Grubic, started to produce rainbow trout in cages in the Krka estuary with guidance and young fish from the Rudjer Boskovic Institute. The Institute also guaranteed government credits.

Messrs Murisic and Grubic started in March 1984 with 6 cages each, stocked with 250 kg of 100–300 g fish per cage. By June 1984 each farmer had a crop of 5 t of fish, which they sold for Din 500/kg, a return of Din 2 500 000. Costs were Din 800 000 for fingerlings, Din 500 000 for cages, and Din 400 000 for food (imported from Italy; conversions were around 1.3:1), a total of Din 1 700 000. In October 1984, the two farmers each proposed to stock 10 cages with 250 kg of 50 g fish. This year they will try to reduce costs by using wet food and by buying smaller fish for stocking. The farmers believe they can produce either one crop per year of 1 kg fish or two crops of 500 g fish.

Now the state company owning a marina at Skradin has declared its intention of putting out 50 cages for rainbow trout this year. The cages will be moored on the marina walkways during winter, when the marina is not in use for boats.

There are also two small private farms outside the Krka area at Jurjevo (Fig. 10). One of these has only two cages, and there is doubt about its continuing operation because the owners have spent last season's income from fish and cannot afford to buy fingerlings. The other, however, is doing well, and, when the consultant visited it, still contained trout of 1 kg weight which had been held over the summer.

The farm belongs to Mr Boris Strinovic, a former employee of the Rudjer Boskovic Institute at Sibenik. His bay receives a fresh water input of 500 1/sec at 10°C throughout the year from a spring, providing salinities around his seven 10 m-diameter circular cages of from 15 at the surface to 35 at 4 m depth. Temperatures are no higher than 17°C at the surface and 19°C at the bottom during summer. Mr Strinovic started his farm in 1982–83. He has tried imported dry feed (Alma, Switzerland) but now uses mostly bluefish heads and other waste from a local processing factory. This costs him only 5 Din/kg (transport cost only in fact), i.e., Din 30/kg of fish produced at 6:1 conversion. In the first half of 1984 the farm produced 5 t of 1 kg fish, which were sold to local hotels at 500 Din/kg. Mr Strinovic expects to produce 10 t in the full year, and is also trying suspended culture of mussels and oysters. Trout growth is from 20–30 g to 300 g in 6 months.

2.3.2 Coho salmon

Expected production of coho salmon by the Rudjer Boskovic Institute in 1985 is 35 t. It is planned to import 150 000 coho eyed eggs during December 1984. This will give the prospect of producing 150 t of salmon in 1986. Some of this may be undertaken by private farmers. This year, the Institute will provide 5 000 of its smolts to the Mirna company at Limski kanal in Istria (Fig. 10, and see below) for cage trials.

The logistics of the Institute's coho production are as follows:

Eggs are imported in December to the Gracanski quarantine hatchery. This has a spring water supply at 10°C and a capacity to produce at least 1 million fry. Water is discharged into the Zagreb city sewer. Eggs take one month to hatch and fry are kept through one month's feeding, during which time viral testing is carried out. In February, parr are transferred to the Knin fish farm. This new unit is owned by the state company INEX-DINARA OOUR POLGOPRIVREDA. It has access to 2 m3/sec of good quality 10°C water from the spring source of the River Krka. Currently it produces 100 t/year of portion trout in concrete raceways, but the Institute has a contract permitting it to use as much of the capacity as it wishes for trout fingerling or coho smolt production. There are therefore sufficient smolt production facilities available to support a very large industry. In October/November smolts can either be transported to brackish acclimatization sites such as Skradin, or to land-based tanks for acclimatization before going on to the sea sites. Harvest is in May/June, before the sea temperature rises too high.


Much of the Adriatic coast of Yugoslavia receives large freshwater inputs due to surface run-off and especially to springs issuing from the mountains which rise steeply from the sea. There are also many underwater springs and, in places, power schemes discharge much cold freshwater. The result is that much of the sea between the islands and the coast is of lower salinity and summer temperature than the open waters of the Adriatic.

The chemical and physical characteristics shown in Tables 5 and 6 for the St. Nikola site at the mouth of the Krka estuary are not a typical of large areas of the open Yugoslav coast which receive substantial freshwater inputs. Salinities sometimes more than 35 make such sites unsuitable for rainbow trout, but there is no reason why coho (or other salmon species) should not survive them as they did at St. Nikola during the experiments reported above. Temperatures of up to 25°C are also to be expected, and this level would probably be lethal to coho salmon. However, temperatures above 20°C occur only during the four warmest months of the year, June-September (Table 5). Except for these hottest months, temperatures are very suitable for salmon growth. As shown by the experiments reported above, coho salmon can be grown from smolt to a mean size of about 1 kg within the 8 coolest months of the year. Had fish been moved from brackishwater into full seawater earlier, as is planned for future trials, it is probable that mean harvest weight would have been considerably higher than 1 kg.

Even excluding “open coast” sites, there are a number of very large brackishwater areas in the estuaries of rivers or in large bays receiving freshwater inputs, where water quality, temperature and salinity can be expected to be suitable for culture of salmon and especially rainbow trout. The largest of these sites are shown in Figures 10, 11 and 12. Additionally there are many smaller bays similar to that at Crikvenice (Table 25, Fig. 10) or to Mr Strinovic's site at Jurjevo (see above). These estuaries and bays alone provide potential cage sites sufficient to produce at least many hundreds, and probably some thousands, of tonnes of fish per year. The technical limitation on their productivity is likely to be water exchange. There are few figures available on this but, because of the lack of tides in the Adriatic, water exchange might be expected to be rather poor. A build-up of waste food, fish faeces, etc., with consequent danger of deoxygenation, will put a limit on the density of cages it is advisable to place in any one area. Water chemical and plankton analyses carried out so far (Tables 1–7), however, indicate that sites are currently in a fairly oligotrophic condition, so that a degree of enrichment can be tolerated without risk of ecological damage.

There are thus two types of area with potential for on-growing salmonids in cages on the Yugoslav coast:

  1. Brackish estuaries and bays with large freshwater inputs, most suitable for rainbow trout culture. Some of these have temperature regimes which will allow trout to be grown all year round, while others might be suitable for use only in the coldest 8 or 9 months. These enclosed areas contain many sites well sheltered from storms, suitable for siting floating cages. Their depth is frequently 10–50 m (e.g., Fig. 1), ideal for mooring cages.

  2. Coastal areas outside large estuaries, but nonetheless enjoying some moderation of temperature and salinity by virtue of the many freshwater inputs on the eastern shore of the Adriatic (Figs. 10, 11 and 12). The water in these areas is expected to be suitable for culture of coho (and other) salmon during the coldest 8 months of the year, though further experimental trials are required to finally confirm this in areas well outside the influence of estuaries. The large and small islands off the Yugoslav coast, together with many bays of all sizes on the mainland, provide a very large number of sheltered sites potentially suitable for sea cages in the areas Rijeka to Zadar and Trogir to Dubrovnik. The fact that the land rises steeply from the sea produces deep water close to shore (frequently 30–70 m, Figs. 10, 11 and 12), providing suitable depths for mooring cages. If, as expected, the experiments now under way prove the suitability of these coastal areas for salmon culture, then the potential area usable for this industry in Yugoslavia is so large that availability of cage sites will not be a limitation on its growth in the foreseeable future.


All the currently operating commercial sea bass/sea bream units in Yugoslavia were also visited in the course of the reconnaissance survey of potential salmonid sites. They are operated by two companies: CENMAR, which has its head office in Zadar, a hatchery at Nin and a sea cage farm at Lamljana Bay on the island of Ugljan; and R.O. MIRNA, with its head office at Rovinj and sea unit in the Limski kanal (fjord). MIRNA will shortly begin construction of a hatchery at the mouth of this fjord. For locations of all these units see Figures 10 and 11.


4.1.1 Hatchery.

Building of the Nin hatchery was completed in 1983, but technical problems delayed the start of production until February 1984. The unit was designed by the Italian consultants “Sirap”, and construction cost about Din 300 million. This was financed largely by local government sources in the Zadar area, much of the cash being in the form of loans, but there was some input from international sources. It has since been necessary to raise more loans to keep the plant operating and the high costs of debt servicing are a major threat to the future of the company.

A very, perhaps unnecessarily, high standard of building was employed at Nin. Indeed, there has been a profligate use of concrete both at CENMAR's hatchery and sea site. Water from a shallow lagoon is pumped to large concrete block-lined ponds which will double as broodstock ponds and reservoirs of water in time of shortage. From these, water enters the hatchery building where it supplies 112 2m3 conical plastic larval tanks and 70 10 m3 circular fibreglass fry tanks. The temperature of water is controlled by gas heating, and a high percentage is re-circulated after passing through large concrete biological filters and UV sterilization units. A live food unit uses batch cultures to produce the succession of phytoplankton to feed rotifers for the fish larvae, followed by Artemia nauplii and eventually adult Artemia for larger larvae, which is at present necessary to feed these very small fish before they can be weaned onto dry food. The usual problems of variable Artemia quality are experienced.

Cycles of production for sea bass begin at the end of November and continue until 1 July. During that time, the hatchery can go through three cycles of fry production, each lasting 80–110 days. The end product of each cycle is fry of about 0.5 g (4 cm). For bream, only one cycle per year is possible, starting in October. Eggs are currently bought in from Italy and from research institutes in Yugoslavia, but soon the unit will spawn its own broodstock using hormone injections. Eggs take 3 or 4 days to hatch in the larval tanks, during which time tanks are aerated but there is no water flow. Then 3 or 4 days after hatching, the larvae begin feeding on rotifers, which are their diet for 10–12 days. They gradually change to a diet of Artemia nauplii, which they receive until they are about 40 days old. During this process, water flow is gradually increased through the larval tanks until a maximum of 15 1/min of recirculated water passes each tank. The young fish are then transferred to the fry tanks. Here they are fed at first on adult Artemia, but are soon introduced to a surface floating weaner food called Larvette (sold by Trouw at a price of Lit 25 000/kg). This is succeeded by dry food from the same manufacturer, the composition of the food being the same as trout diets. Auto-feeders are fitted to fry tanks. The fry also receive minced fish. Water flow through fry tanks is gradually increased to a maximum of 80 1/min. Fish leave the hatchery for the sea unit at about 0.5 g weight, and survival to this size from the egg is 20–25 percent.

The Nin hatchery suffers from a number of problems, most associated with unit design. Minor problems are the ineffectiveness of the biological filtration units and of the automated cleaning devices fitted to larval tanks, the fact that the concrete reservoir tanks leak, and the inability of the outlet screens in the fry tanks to pass enough water (they are too small). More seriously, the quality of water arriving from the pumps is often of very poor quality and low temperature, and indeed can dry up altogether. The basic problem is the siting of the hatchery, which has been built to receive water from a shallow (1 m) lagoon. In winter, when the cold northeast Bora wind blows, this lagoon becomes stirred into a cloudy soup, the temperature of which can fall close to zero. As Yugoslavia has an abundance of clean, deepwater sites which would have been far more suitable for this type of hatchery, it is difficult to understand why the Nin site was chosen.

However, despite these problems and the late start, the hatchery produced well during 1984, and 1.2 million sea bass fry (80 percent of the planned annual production) were transported to the sea. At present almost all the production goes to the company's own sea unit, but future expansion is planned to provide fry for sale to outsiders, including small private farmers. Costs of fry produced to date have been very high at approximately Din 135 each. However, it was said that only 15 percent of this was for energy and feeds and 12 percent for labour. The bulk of costs were interest charges on loans and depreciation on the high construction costs.

4.1.2 Sea unit.

CENMAR currently operates only one sea unit at Lamljana Bay, but it plans to develop new sites as more fry become available from the Nin hatchery. At Lamljana, flotillas of square 5 × 5 m cages are constructed of a bolted, galvanized and pointed steel framework supporting timber walkways on top of polystryene floats. On land, there is a large storage shed for feeds and equipment and an office complex, all built to a very high standard.

Sea bass fry (0.5 g), stocked in sea cages in April-July 1984, are expected to be ready for market (at a size of 250–300 g) in autumn 1985. Feeding at Lamljana is with imported dry pellets mixed with minced sardine. Some auto-feeders are being installed to deliver dry pellets, but most feeding is done by hand. Workers prepare and deliver food to the cages continuously throughout the working day. There is an on-going problem with vibrio disease at the sea site. Cage nets become fouled very quickly and must be changed every few weeks.

Target production for this site is 300 t/year. It is planned to sell almost all this fish for export, especially to Italy, though a little will go for the tourist market in Yugoslavia. Sea bass/sea bream is now reported to be beyond the financial means of most Yugoslavs. CENMAR claims to receive about Lit 15 000/kg (Din 1 400) wholesale in Italy. In Yugoslavia the retail price is about the same; the wholesale price is much lower.

4.2 R.O. MIRNA

Since 1981, this company has been involved in a polyculture programme in the Lim fjord, Istria. For two years, oceanographic surveys of the biological, chemical and physical status of the 11 km long fjord were done. On the basis of this work, a phased plan to use the site for aquaculture was developed. To allow the programme to go ahead uninterrupted, the area has been closed to unauthorized boats, and fishing is prohibited. Phase 1 of the plan was the establishment of hanging culture of oysters and mussels, and the fjord currently produces annually about 1 million oysters and 120 t of mussels. These are graded and cleaned at the company's factory in Rovinj.

Trials are also being conducted with cage culture of sea bass and bream. To date, fry have been bought in from Italy, from the Department of Fisheries Marine Laboratory at Split, and from the CENMAR hatchery at Nin; but construction of R.O. MIRNA's own hatchery will shortly start.

The cages used for sea bass and sea bream production are strongly constructed of galvanized steel frames flexibly hinged together supporting timber walkways. Flotation is of expanded polystyrene encased in thick PVC containers. Imported fry averaging 1 g take approximately 18 months to reach harvest size of 300 g. The current objective is an annual production of 150 t of fish and, as at CENMAR, it is planned to export most of it.

The MIRNA company owns a fishing fleet which lands sardine into Rovinj. It has a fishmeal plant capable of producing 1 000 t/year, and the capacity to make up its own dry pelleted feeds. MIRNA also enjoys good relations with a local chicken/turkey food producer, and has the possibility of increasing local production of fish feed by making intermittent use of their facilities. MIRNA therefore has the capacity to produce annually at least 3 000 t of grower pellets.

The next phase of MIRNA's sea bass/sea bream programme is the construction of a hatchery near the mouth of the Lim fjord. Here, the water is deep, and there will be two intakes for pumped water, one at 3 m and one at 25 m to give temperature control. The hatchery has been designed so that it can be built in “modules”. The first module, scheduled for completion in 1985, will have a production capacity of 1 million fry per year. This should be sufficient to produce 200 t of harvest-size fish. Further modules can be added up to a total of five, giving a theoretical annual production potential of 1 000 t of harvest-size fish. In addition to live food production units, larval and fry tanks, the MIRNA hatchery will be equipped with larger tanks to enable fingerlings to be grown to a size of circa 15 g before transfer to the sea. This will overcome the problem of very fine net mesh sizes, which are currently necessary on floating cages when 0.5–1 g fry first go to sea. Fine-meshed nets have a small “open area” which quickly blocks with fouling organisms, and they must therefore be changed very frequently. In addition, large earth ponds will be built on flat land near the hatchery site. Here, sea bass/sea bream will be grown to harvest size in the same way as is practised in Spain, France and Italy. Comparison can then be made of the fish performance and costs of growing fish in ponds and floating cages.

The costs of the first phase of hatchery and pond building are estimated at Din 250 million. This is being financed largely by the MIRNA company itself, but loans and grants have also been obtained from Yugoslav banks, the International Credit Bank, and from the Yugoslav Tourist Board.

MIRNA is interested in any species of good potential for growth in Yugoslav waters. Accordingly, this year, trials will begin with cage culture of coho salmon at Lim. During October/November 5 000 smolts are due to be delivered from the Rudjer Boskovic Institute stock. If these fish perform well, it is planned to extend the trials to 50 000 smolts from the same source next year.

MIRNA's long-term plan for aquaculture includes development of at least two other large bays on the Istrian peninsula. The estuary of the Rasa River and Budaua Bay (see Fig. 10) have already been designated reserved areas for the purpose of aquaculture development.


Some Yugoslav workers seem to think that either sea bass/sea bream farming or marine salmonid farming will develop. This idea has probably grown from competition between proposed programmes on the two types of fish species for limited financial resources. Technically, there is absolutely no reason why sea bass/sea bream and salmonid farming should not develop in parallel. Brackish estuary sites, suitable for rainbow trout culture, are not of interest to sea bass/sea bream farmers, and there are plenty of sheltered, deep “open coast” sites to support very large numbers of cages for both salmon and indigenous sea fishes. The biological requirements of the species will dictate that salmon farmers choose sites in which salinity and temperature are moderated, largely to be found on the mainland, whereas marine fish farmers require full seawater, which is perhaps best found on the outside of the islands (e.g., see CENMAR's site, Fig. 10).

To date, most of the financial support available has gone to sea bass/sea bream culture, partly in the context of an overall plan for marine fish farming in the Mediterranean. By its nature, culture of these species requires the most support. The technology of producing fry is much more complex than that for salmonids, because of the extremely small size of newly hatched larvae, and the consequent problems of introducing young fish to artificial diets. The work currently being done (notably by Mars (UK) Ltd., Slough) in developing microencapsulated diets to replace live feeds for marine fish and prawn larvae may help to simplify the process in the near future.

However, it sometimes seems that programmes for culture of these species operate on a “no expense spared” basis. The Nin hatchery is an example, where standards of building unnecessarily high for a fish farm were adopted. More seriously, the technology of marine fish fry production is imperfect and will gradually improve. It is therefore logical to design flexible facilities which can be changed to accommodate new ideas. Building everything from reinforced concrete is not the solution. In this respect the designers of the new MIRNA hatchery at Lim seem to have a much better approach. By building in phases, problems found in the prototype module can be rectified at later stages.

In Yugoslavia, there must be doubts about the current economics of sea bass/sea bream farming. Allowing a 20 percent mortality of fish during marine grow-out, it requires 5 fry to produce each kilogramme of 250 g fish ready for market. At Nin's 1984 fry production costs, this represents more than Din 740 (over half the expected sale price) for fry alone. The social desirability of basing an industry solely on exports to gain foreign exchange can also be questioned.

On the other hand, the technology of salmonid production is well established, having been practised in freshwater since the last century and in seawater for over 20 years. Adequate facilities for production of fingerlings and smolts already exist, and young fish can be produced relatively cheaply. Growth of rainbow trout to portion size in Yugoslav freshwater ponds is slow, taking on average 18–22 months (see Fig. 5). This is about the same as in northern Europe, e.g., Denmark and Scotland, but much longer than in most other Mediterranean countries such as Spain, where 9–14 months is more usual. Local workers attribute this to the fact that most Yugoslav farms draw their water from cold (usually 10°C) springs. They do not therefore obtain the high growth rates in summer which would be expected if warmer, surface water was used. The “shoestring” experiments carried out by the Rudjer Boskovic Institute have now clearly demonstrated the feasibility of cage culture of coho salmon to at least 1 kg and rainbow trout to at least 1.5 kg in Yugoslavia. They have also shown that growth of rainbow trout is much faster in brackish than in freshwater. The groundwork having been done, there is now considerable private and state company interest in cage farming. The consultant expects to see output from marine/brackishwater salmonid farms grow to overtake sea bass/sea bream production within two years, and then to stay ahead until some of the problems associated with culture of the latter species are solved. The relatively low production costs of salmonids grown in this way will enable them to be sold at prices which Yugoslavia citizens can afford. Per caput consumption of fish in Yugoslavia is low (about 3 kg/year), but it is still necessary to import 30 000 t/year of fish. Rudjer Boskovic staff hope that a thriving salmonid cage farming industry will help on the one hand to increase the consumption of fish in Yugoslavia and on the other hand to replace part of the tonnage of imported fish by locally-produced fish, thus saving foreign exchange. However, much of the fish imported comprises species of the cod and tuna families. Farmers of caged salmonids may experience problems with the conservatism of the fish-eating public. In most countries, new types of fish introduced onto the market initially meet considerable sales resistance from consumers. It is the author's guess that this, rather than any technical setbacks, will impose the limit on rainbow trout/coho salmon production in Yugoslavia.


The proposal requests international assistance to enable the Rudjer Boskovic Institute to develop brackish/seawater cage culture of rainbow trout/coho salmon in Yugoslavia. Since the initial proposal was made, the Institute's continuing work (described above) has now proved the basic technical feasibility of this type of fish farming in Yugoslavia. Suitable sites are also plentiful. The author was impressed with the calibre and motivation of all the Institute staff engaged in this project. They have conducted their experiments in a logical and down-to-earth way, keeping costs low and extending the scope of their activities gradually year by year. There is no reason to believe that this rational approach will change adversely if financial assistance is given, but support would enable a more rapid development of a very promising new industry.

The author's overall impression was therefore very favourable, and he would not oppose most of the proposals and assertions put forward in Part II of the project document. Nevertheless, there were inevitably some elements of the proposal with which he did not fully agree, and to which he would suggest amendment. The most important are as follows:


In the initial proposal (US$ 98 000 or approximately 50 percent of the total UNDP support requested) was for laboratory equipment. Of this, around US$ 82 000 was for apparatus and chemicals for analyses of feeds, and a further US$ 14 000 for equipment to examine water chemistry, including a microcomputer. In the revised proposal this has been reduced, but laboratory equipment and the chemicals for use with it still comprise US$ 84 000, or 50 percent of the revised total requested.

Some items of laboratory equipment are certainly necessary, e.g., a microscope for Sibenik and one or more portable oxygen meters. The real point of dissention comes with the equipment for analyses of feeds. The Institute scientists argue that capacity for full chemical and bacteriological analyses of feeds is necessary primarily in order to develop wet diets, but also to monitor the quality of both home-made wet feeds and dry ones from external sources. (The Institute scientists suspect, probably correctly, that many commercially produced feeds do not measure up to the manufacturers' assertions about chemical and ingredient contents.) However, wet diets have been in use in other countries for many years. The constituents necessary and methods of manufacture are well documented and do not require extensive researching. As for quality control, companies successfully producing annually hundreds of tonnes of salmon and rainbow trout using wet feeds, e.g., in Norway, do not have such laboratory equipment or find it necessary to conduct elaborate routine tests. If fresh fish (or fish which was frozen when fresh) is used, and the wet food is made up in small batches to be used quickly, there is no reason why feed quality should be suspect.

As far as commercially-produced dry feeds are concerned, all manufacturers have a quality control department with the necessary equipment. Institute scientists should therefore try to work alongside a local manufacturer (and not in competition with him) to ensure that good quality feeds are produced in the common interest. R.O. MIRNA, with its own involvement in fish farming plus fishmeal supply and pellet-manufacturing capacity, would be an ideal partner. This company will not need all its own capacity for years to come, and meanwhile could supply good quality feeds for salmonid farmers. The nutritional requirements of salmonids and sea fishes are not thought to be very different, so that any improvement in food quality would also benefit MIRNA's sea bass/sea bream operations. The problem here is the lack of inclination to cooperate - indeed sometimes almost hostility - between different factions in the fish farming business in Yugoslavia. All factions would benefit if these differences were overcome and the staff, most of very high quality, cooperated more fully. If this is really impossible, the Institute could work with another fish feed manufacturer, of which there is at least one in Zagreb. The author is ready to provide up-to-date feed recipes, e.g., from Scandinavian manufacturers, if requested.

On the other hand, items necessary for the increased practical production of farmed salmonids are not mentioned in the proposal. Examples are one or more (depending on proposed farm locations) mincing, blending and extrusion machines for producing wet or moist pellets, freezers for storing food ingredients, chiller units to enable made-up wet feeds to be stored for a short time in insulated rooms, ice machines and packing machinery to package fish in good condition for market, transport tanks and a truck with hydraulic hoist to carry smolts/fingerlings from the hatchery to sea sites, and a boat/boats to service cages. Since all vitamin/mineral premixes, binders, antibiotics, and even much fishmeal, have to be imported with scare foreign exchange, it is also considered that the amounts requested for these items are insufficient. Additionally, the consultant recommends that commercially produced Scandinavian net antifoulants be tried (e.g., Monopol “Ren Not”, available through T. Skretting A/S, Stavanger, Norway).


The project document envisages very short-term visits (sometimes less than a week) by at least five different consultants, each a specialist in a particular field of study: disease, feeds, breeding, etc. Instead, it would be better to reduce the number of consultants recruited. Anyone who has had some years experience in management of commercial salmon/trout cage farms will have been forced to acquire sufficient knowledge on each specialist aspect of the business (and in other important aspects not mentioned, e.g., product development and marketing). The ideal solution would be to have one person who will come to know the Yugoslav project and its problems rather than many different individuals working in their own field in isolation, each expert requiring the first week of his short visit to familiarize himself with the set-up. Further, by seeing the project at intervals, a single consultant will be better equipped to make meaningful progress reports to FAO/UNDP.

Altogether, the amount of FAO back-up requested seems too small, totalling only 3 man-months over three years. However, it is so expensive (budgeted at US$ 8 000 per man-month including travel) that a project of this size cannot be asked to bear much more.


It is questionable whether “training” is really the right word. As will be seen from the list of staff engaged in this project, there is already a very high standard of competence in many specialist fields. The list includes several veterinary experts, biologists and chemists with PhD or MSc degrees, and even a full-time lawyer. The veterinary experts, for example, are currently routinely engaged in fish-health monitoring on freshwater trout and carp farms. To send one of these people on a 3-month fish diseases course, in which, for example, he would be shown how to use a microscope and recognize a gill fluke, would clearly be pointless. The same would apply to specialists in other disciplines.

However, travel overseas is valuable in establishing contacts with scientists and fish farmers in other countries, and for observing different ways of operating. In a small country with foreign exchange problems, such as Yugoslavia, it is easy for workers to feel isolated and out-of-touch with the mainstream of progress in their profession. Overseas trips should perhaps be re-titled “study tours”, with the implication that individuals will travel widely in the chosen destination countries to establish many personal contacts and see many operating salmonid farms. Norway, Japan and Scotland would be the most relevant countries for visits. As with an incoming FAO consultant, a project member travelling overseas should look at all aspects of the business, not just his own speciality as envisaged in the proposal. The aim should be to produce competent allround fish farmers.

Funding requested in this section (US$ 40 000) seems high, considering that only actual travel and subsistence costs are involved; salaries would be paid from the local contribution to the project.

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