Fennel and Anise Oils as Sedatives in Common Carp

Jim Crocker
19th April, 2024

Fennel and Anise Oils as Sedatives in Common Carp

Image Source: Natural Science News, 2024

Key Findings

  • In a study from Isparta University of Applied Sciences, fennel oil safely anesthetized common carp
  • Fennel oil induced anesthesia in 308 seconds and allowed recovery in 472 seconds, with no fish mortality
  • Anise oil, while effective at lower concentrations, caused a 10% mortality rate and tissue damage
In the realm of aquatic research, ensuring the well-being of fish during experimental procedures is paramount. Anesthesia plays a critical role in this process, allowing for the immobilization of fish with minimal stress and pain. However, finding the right anesthetic that is both effective and safe for different fish species can be a challenge. A recent study from Isparta University of Applied Sciences has made significant strides in this area by examining the use of fennel and anise essential oils as potential anesthetics for common carp[1]. The common carp, a species often used in scientific studies, requires careful handling to maintain its health and the integrity of research results[2]. The new study sought to determine not only the anesthetic capabilities of fennel and anise oils but also their impact on the fish's body at a cellular level. Researchers exposed the fish to varying concentrations of these oils, observing the induction and recovery times from anesthesia, as well as any side effects on the fish's tissues and blood chemistry. Fennel oil emerged as a promising anesthetic at a concentration of 500 mg Lāˆ’1, inducing anesthesia in an average of 308 seconds and allowing for recovery in 472 seconds. This is particularly noteworthy when considering the rapid induction times and the safer recovery profiles of essential oils like eugenol and Lippia alba oil, as previously reported in Amazonian freshwater stingrays[3] and koi carp using different basil species oils[4]. The induction times for fennel oil are longer than those for eugenol or basil oils, but it offers a safer profile for common carp, with no observed mortality at effective concentrations. Anise oil, on the other hand, induced deep anesthesia at a lower concentration of 100 mg Lāˆ’1 but required a considerably longer induction time of 20 minutes. Moreover, at concentrations above 100 mg Lāˆ’1, anise oil resulted in a 10% mortality rate among the fish, raising concerns about its safety as an anesthetic. The study also meticulously evaluated the physiological and histopathological effects of the essential oils. Unlike previous studies that found moderate to severe histological changes in the gills of stingrays[3] or the cytotoxic effects on fish peripheral blood nuclear cells[4], fennel oil did not cause any noticeable pathological changes in the gills, skin, or hepatopancreas of the common carp. Anise oil, however, did lead to severe hyperemia (an excess of blood in the vessels), inflammatory cell infiltrations in the gills, and erosive skin lesions, indicating that it could be harmful to fish tissue. Blood parameters such as sodium, potassium, calcium, and chloride levels remained stable during deep anesthesia with both oils, suggesting that the essential functions of the fish were not compromised. Interestingly, plasma glucose levels were lower in fish anesthetized with anise oil compared to the control group and those treated with fennel oil, hinting at a possible metabolic effect of anise oil. The findings from Isparta University of Applied Sciences indicate that fennel essential oil, at the right concentration, is a viable and safe anesthetic for use in common carp. It provides a balance between efficacy and safety, without the adverse tissue reactions seen with anise oil or the longer recovery times associated with other anesthetics like eugenol[3]. This study expands on previous research by offering an alternative anesthetic that could be tailored to the needs of common carp, potentially improving welfare standards in fish research. As the search for optimal anesthetics continues, studies like this one are essential in developing protocols that protect fish health and contribute to the reliability of scientific data.

HerbsMedicineAnimal Science


Main Study

1) Efficacy of fennel (Foeniculum vulgare) and anise (Pimpinella anisum) essential oils as anaesthesics in common carp (Cyprinus carpio L. 1758)

Published 17th April, 2024


Related Studies

2) Anaesthetics and analgesics used in adult fish for research: A review.


3) Eugenol and Lippia alba essential oils as effective anesthetics for the Amazonian freshwater stingray Potamotrygon wallacei (Chondrichthyes, Potamotrygonidae).


4) Anesthetic activity of plant essential oils on Cyprinus carpio (koi carp).


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