engleski

The principles of construction of fish cages

Kaveski uzgoj je metoda uzgoja ribe u posebnim tipovim uzgojnih objekata. Svi uzgojni objekti su dizajnirani tako da drže uzgajane objekte u zatočeništvu dok im se ne poveća biomasa. Većina kaveza je jednostavne konstrukcije i mogu se sastaviti za dan ili dva, a lako se održavaju. Riblje farme na kojima se vrši uzgoj u kavezima mogu se lako povećati dodavanjem novih kaveskoh jedinica, a kavezi lako premještati s mjesta na mjesto. No isto tako kavezi su podložni oštećenjima uslijed loših vremenskih uvjeta, a zbog ograničenog volumena mogu oštetiti uzgajane organizme. Postoji ogromna razlika u veličini i vrstama četiri osnovna tipa kaveza: fiksni, plutajući, uronjeni i uronjivi. U teoriji su njihov oblik i veličina diktirani kombinacijom različitih faktora, uključujući: vrstu uzgajanih organizama, uvjete okoline, metode uzgoja, svojstva, troškove i dostupnost konstrukcijskog materijala, te lokalne socio-ekonomske prilike. Pri dizajniranju valja uzeti u obzir tip uzgoja i veličinu proizvodnje, te istražiti interferenciju sila okoliša i strukture kaveza. Sile koje djeluju na kavez i sustav njegovog sidrenjaiznimno su složene i teške za određivanje, stoga analiza njihovog djelovanja zahtjeva upotrebu sofisticiranih modela za testiranje kao i kompjuterskih modela. Potpuna ocjena objekata za uzgoj ribe zahtjeva ne samo studiju kvalitete vode, već i istraživanje ponašanja ribe i njihovog fiziološkog odgovora. Ova istraživanja su vrlo rijetka, jer je većina uzgojnih jedinica vrlo dobro dizajnirana i smještena u dobro zaklonjeno obalno područje. Danas postoji tendencija premještanja uzgoja u izloženije obalno područje, čime raste i obaveza zaštite ribe i pojačanja konstrukcije kaveza. Tako će kavezi morati dizajnirati i testirati po mnogo strožim standardima, a njhova proizvodnja morat će pojeftiniti, da bi zadovoljiline samo uzgajivače, već i osiguravajuća društva i vladine sigurnosne standarde. Isto tako, može se očekivati uvođenje sustava licenci za kaveze slični već postojećim licencama za brodove. Cage culture is a method of forming aquatic organisms in a particular type of rearing facility. All culture systems are designed to hold organisms capture whilst they increase in biomass. The majority of cages are fairly simple to construct and can be put together in a day. They are also easily managed. Cage farms can be expensed simply by adding a few more cages and cages moved around with little restriction. The cages are susceptible to storm damage. Due to small volume fish grown in cages can succumb to fin and skin damage through abrasion. There four basic types of cages: fixed, floating, submersible, submerged and an enormous variety in the size and design of cages. Cages are small and typically have a surface area between 1 and 1000 m2. In theory the shape and size of fish cages should be dictated by a combination of factors, including: species, prevailing environmental conditions, method of culture, properties, cost and availability of materials, and local skills. The design must also take cognizance of the type and size of fish culture and research into the interaction between impinging environmental forces. The forces acting on a cage and mooring system are exceptionally complex and difficult to quantify, and analyses of the responses of a cage structures to these forces requires the development and use of sophisticated test rigs and computer models. A thorough evaluation of holding facilities for fishes require not only studies into the water quality but also investigation of the fish behavioral and physiological responses. There has been little incentive to carry out this type of investigative work since most designs work reasonably well, at least in the comparative shelter afforded by most coastal and inland sites. However, the situation is changing. There is growing pressure to culture fish in more exposed, offshore locations and increasing concern over security of stock and rigidity of cage construction. Thus in future cages will have to be more stringently designed, tested and cost-effectively manufactured and they will have to satisfy not only the fish farmers but also the insurance companies and government safety standards. Plans to introduce a system of licensing for cages, similar to that already governing the shipping, have been mooted.

Fish rearing; cages; principles of construction

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