Epsilon Archive for Student Projects

Abstract

I samband med att fiskar har blivit allt vanligare inom områden som forskning, odling och miljöövervakning har behovet av att säkerställa god djuromsorg blivit mer uppmärksammat. För att minska fiskens stress och underlätta den fysiska hanteringen brukar bedövningsmedel användas i många sammanhang. Eftersom det råder stor artvariation mellan fiskars svar på bedövning är det viktigt att lägga resurser på bedövningsstudier för att säkerställa bästa möjliga djurhållning för varje enskild art. I den här studien undersöktes stressrespons samt beteende hos öring (Salmo trutta) vid bedövning med olika koncentrationer av bedövningsmedlen trikain, eugenol, bensokain samt metomidat. Ettåriga, odlade öringar PIT-tag märktes för att möjliggöra identifiering av varje fiskindivid. Knappt fyra veckor efter märkningen utfördes bedövningsexperimentet där låga och höga koncentrationer av de olika bedövningsmedlen (3 mg/L respektive 6 mg/L för metomidat och 40 mg/L respektive 80 mg/L för de övriga) användes för bedövning av fisk genom tillsats till vatten följt av upptag genom gälarna. Bedövningsprocessen filmades och induktionstid, rusningstid samt uppvisandet av ett specifikt beteende noterades. Av bedövningsmedlen var det eugenol som hade lägst induktionstid. Varken bedövningsmedel eller koncentration hade en signifikant påverkan på rusningstiden. Det specifika beteendet innebar att fiskarna efter förlorad balans lade sig på sidan men fortsatte röra mycket på stjärtfenan, ofta i cirkulära rörelser, tillsammans med mer eller mindre häftiga sidorörelser med huvudet mot ytan som för att ”kippa efter syre”. Beteendet var vanligare vid bedövning med metomidat än med de andra bedövningsmedlen, 80% av fiskarna som bedövades med den lägre koncentrationen metomidat uppvisade det. Slutligen fastställdes 40 mg/L eugenol som det rekommenderade bedövningsmedlet för ettåriga, odlade öringar inom längdintervallet 95 - 140 mm vid en vattentemperatur runt 3 - 4°C. Detta baserat på den korta induktionstiden (medianvärde 1,3 minuter) och den hämmande effekten på fiskars stressrespons eugenol har beskrivits ha. Bedövning med 3 mg/L metomidat rekommenderas inte under förhållanden som liknar studiens.

As fish has become more frequently used in areas such as research, aquaculture and environmental monitoring the need for ensuring animal welfare has gained more attention. In order to reduce the stress level of the fish and to facilitate the physical handling anesthetics are commonly used. Since there is great species variation between fish in their response to anesthetics it is important to put resources into studies of fish anesthetizing to ensure the highest possible fish wellbeing. In this study As fish has become more frequently used in areas such as research, aquaculture and environmental monitoring the need for ensuring animal welfare has gained more attention. In order to reduce the stress level of the fish and to facilitate the physical handling anesthetics are commonly used. Since there is great species variation between fish in their response to anesthetics it is important to put resources into studies of fish anesthetizing to ensure the highest possible fish wellbeing. In this study the stress response and behavior of trout (Salmo trutta) was analyzed during anesthesia with tricaine, eugenol, benzocaine and metomidate. One year old, farmed trout were PIT-tagged in order to enable identification of every fish. Around four weeks after the tagging the anesthetics experiment took place where low and high concentrations of the anesthetics (3 mg/L and 6 mg/L for metomidate and 40 mg/L and 80 mg/L for the other ones) were used to anesthetize the fish through addition to water followed by absorption through the gills. The anesthetizing process was recorded and the induction time, excitation time and the display of a specific behavior was noted. Of the tested anesthetics eugenol resulted in the shortest induction time. Neither the anesthetic nor the concentration had a significant effect on the excitation time. The specific behavior involved the fish falling to the side after having lost balance but continuing to move the tail fin, often in circular motions, together with more or less forceful side movements where the head went towards the surface as if the fish was “gasping for air”. The behavior was more common during metomidate anesthetizing than for the other anesthetics, 80% of the fish anesthetized with the lower dose of metomidate displayed it. In the end 40 mg/L eugenol was established as the recommended anesthetic for one year old, farmed trout between the length interval 95-140mm at a water temperature around 3 – 4°C. This based on the short induction time (median value 1,3 minutes) together with the inhibiting effect on the stress response of fish that eugenol is said to have. The use of 3 mg/L metomidate is not recommended under conditions similar to those in this study. the stress response and behavior of trout (Salmo trutta) was analyzed during anesthesia with tricaine, eugenol, benzocaine and metomidate. One year old, farmed trout were PIT-tagged in order to enable identification of every fish. Around four weeks after the tagging the anesthetics experiment took place where low and high concentrations of the anesthetics (3 mg/L and 6 mg/L for metomidate and 40 mg/L and 80 mg/L for the other ones) were used to anesthetize the fish through addition to water followed by absorption through the gills. The anesthetizing process was recorded and the induction time, excitation time and the display of a specific behavior was noted. Of the tested anesthetics eugenol resulted in the shortest induction time. Neither the anesthetic nor the concentration had a significant effect on the excitation time. The specific behavior involved the fish falling to the side after having lost balance but continuing to move the tail fin, often in circular motions, together with more or less forceful side movements where the head went towards the surface as if the fish was “gasping for air”. The behavior was more common during metomidate anesthetizing than for the other anesthetics, 80% of the fish anesthetized with the lower dose of metomidate displayed it. In the end 40 mg/L eugenol was established as the recommended anesthetic for one year old, farmed trout between the length interval 95-140mm at a water temperature around 3 – 4°C. This based on the short induction time (median value 1,3 minutes) together with the inhibiting effect on the stress response of fish that eugenol is said to have. The use of 3 mg/L metomidate is not recommended under conditions similar to those in this study.