Cum sa previi imbolnavirea pestilor din iaz

Causes of disease in pond fish

Exista patru cauze majore care duc la imbolnavirea pestilor, in orice habitat s-ar afla acestia; cauze care au legatura cu mediu, cauze infectioase, cele legate de malnutritie sau hranire incorecta si cele care au fost mostenite sau transmise genetic.

Ultimele doua cauze sunt insemnate si nu trebuie ignorate. In acelasi timp, exista si afectiuni aparute in urma unor influente din partea mediului sau care au cauze patogenice. Ele duc catre cele mai des intalnite boli ale pestilor din iazuri. In randurile urmatoare, ne vom concentra pe aceste tipuri  principale de afectiuni.

Mai inainte, sa stabilim ce inseamna afectiune provocata de mediu. Pe scurt, mediul creat de ingrijitorul iazului nu respecta cerintele din mediul natural al pestilor si ii impinge pe acestia din urma sa se adapteze oarecum fortat la un ambient nepropice. In consecinta, pestii vor fi, in primul rand, stresati.

Asadar, ce tip de mediu prefera cei mai intalniti locuitori ai iazurilor, cum ar fi crapii koi, goldfish, vaduvita (Orfe) sau rosioara (rudd)? Pestii din iaz au nevoie de o apa cu o valoare a pH-ului cuprinsa intre 6 si 9. Valoarea/scala pH-uluinu este liniara, fiecare schimbare a unitatii inseamna o modificare de 10 ori a aciditatii apei, astfel ca ceea ce pare o usoara modificare a pH-ului apei este, de fapt, o schimbare serioasa a aciditatii din intregul iaz.

Mineralele de bicarbonat si carbonat din apa functioneaza pentru a proteja ca un scut pH impotriva schimbarilor masurate ca “duritata carbonatului” sau KH. Prin urmare, cand verificam daca pH-ul este la o valoare  in limitele tolerantelor pestilor din iaz, trebuie sa verificam daca valoarea KH este peste 4⁰dH, astfel incat sa existe  o capacitate de tamponare suficienta pentru a mentine stabila respectiva valoare. Daca pestii sunt tinuti intr-o apa al carei pH este prea mare sau, din conta, prea mic, sau intampina fluctuatii regulate, asa cum se observa in iazurile in care prezenta algelor este exagerata – atunci trebuie sa ne asteptam ca acesti vor fi letargici, acoperiti de mucus in exces, cu piele si inotatoare din ce in ce mai rosiatice.  De asemenea, pestii afectati vor refuza sa manance si vor sta in zona gurilor de filtrare si a cascadelor. Acest ultim comportament se datoreaza unei concentratii ceva mai mare de oxigen dizolvat (DO), in aceasta parte a iazului.

Oriunde exista turbulente la suprafata apei, oxigenul din aer ar trebui sa se dizolve in apa. Cerinta unui peste in ceea ce priveste cantitatea de oxigen dizolvat depinde de temperatura si, pentru fiecare crestere cu 10 grade, cerinta de oxigen se poate dubla. Este trist, dar apa prea calda nu este bogata in oxigen dizolvat cum este cea mai rece. Aceasta problema se regaseste la nivelul iazului mai ales in anotimpul foarte cald. Din nou, pestii vor fi letargici si vor cauta sa stea in zonele care le favorizeaza oxigenul dorit.

Trebuie stabilita, mai ales vara, o concentratie de oxigen dizolvat care este echivalenta cu aproximativ 70 procente din punctul de saturatie al DO la temperatura curenta a apei.

Daca nivelul de oxigen saturat din iaz scade, si alti locuitori din iaz pot fi destul de afectati, in special  bacteriile nitrificante care au rolul de a transforma murdaria care contine amoniac (dejectiile pestilor) in nitrit si apoi in nitrat. Acest proces depinde foarte mult de oxigen, asadar bacteriile nitrificante au in permanenta nevoie de apa curata  bogata in oxigen dizolvat, altfel toxinele si nitritii se pot acumula la nivelul apei, ceea ce nu va fi bine pentru pesti.

Considering the environmental preferences of the pond fish, an undetectable level of ammonia and nitrite is required, if either are detected in the water than a thorough investigation into why the nitrifying bacteria are not able to perform properly is essential. New, overstocked, and overfed ponds, as well as ponds with unmaintained filter systems and those following long power cuts are all susceptible to rises in the concentration of troublesome ammonia and nitrite. Fishes poisoned by these toxins show the same non-specific symptoms described above, making diagnosis of the problem by symptoms alone impossible. Water testing kits must be used but this doesn’t have to be a time consuming task. Tetra has made water testing and interpretation easier than ever by using 6in1 water test strips in conjunction with its free digital water test app which is available on both iPhones and Android. Not only does this provide quick results but also recommendations for next steps if needed.

If the environmental requirements of the pond fishes are not met then the fish will mount a stress response; a series of physiological processes coordinated primarily by stress hormones such as the corticosteroids. Long-term release of these hormones can have harmful effects on many facets of the immune system – the fish’s innate and acquired protection against pathogenic organisms.

There are many opportunistic pathogens that live in the pond with the fish, such as the ‘white spot’ parasite are obligate pathogens which can only survive by infecting host fishes. However, even in a population of healthy fishes, a minority of individuals will have a small burden of the parasite. Other pathogens such as the sessile peritrichs, and certain bacterial or fungal organisms usually live in the organic matter of the pond but can also live parasitically on weakened and wounded fishes.

Very often, when a pathogenic disease strikes there is usually some predisposing factor. Inappropriate water quality is often the root of the problem, though in the pond, seasonal changes in water temperature can also be to blame. In winter, when the water temperatures are below 10⁰C the fish’s immune system is mostly inactive, however most pathogens are inactive also. As the temperature rises in spring, pathogen activity increases though the immune system takes longer to catch up. This leaves a window of infection when the fish are vulnerable and so a preventative dosing of the pond with a broad spectrum antiparasitic such as Tetra MediFin can be very beneficial for the fish at this sensitive time of year.

Additionally ensuring the fish diet is optimal at this time is also vital. Tetra pond fish foods are supplemented with ingredients to enhance elements of the immune response better protecting the fish against infectious disease year-round.

Through monitoring and maintenance of good water quality, we can ensure the fish’s environmental requirements are met consistently. This prevents the fish becoming stressed which could make them more susceptible to opportunistic diseases. Though there are other causes of ill health, the majority of pond fish diseases can be kept at bay by following these simple rules.