Abstract
Essential oil derivatives are widely used for anaesthetising aquatic animals. However, the effectiveness of anaesthesia often varies according to the anaesthetic agent, species, temperature, dosage, and interactions among these factors. This study evaluated the effects of eugenol on three sizes of the shrimp Palaemonetes sinensis at different concentrations and temperatures. Eugenol dose, water temperature, and shrimp size were found to significantly influence anaesthesia in P. sinensis. Induction time decreased linearly with increasing water temperature and eugenol concentration, while it increased with body weight. However, recovery times lengthened with increasing concentration and temperature, and shortened with lower body size. At 100 and 200 μL/L eugenol concentrations, the survival rates of medium and large shrimps were maintained at over 80% at all temperatures studied over 72 h recovery. However, the survival rates of small shrimps were below 60% at 24 °C and 28 °C over 5 days of recovery. These results suggest that eugenol is an effective and rapid anaesthetic for P. sinensis, but it might have disadvantages such as slow recovery and possible mortality in small shrimps and at higher temperatures and dosages.
Highlights
Anaesthetics are widely used to reduce physiological stress and mechanical damage in aquaculture and fisheries during netting, handling, sampling, and transportation[1,2,3]
At eugenol concentrations over 400 μL/L, the highest survival rates were achieved at 20 °C, 20 °C, and 24 °C for small, medium, and large shrimps, respectively. Anaesthetics such as MS-222 and Aqui-SM are approved for food-safe use in aquaculture animals in most countries, including the USA, Australia, New Zealand, and countries of the European Union
Eugenol is obtained and is generally considered safe by most national authorities. It has proved effective in many crustaceans, including Homarus americanus[12], Fenneropenaeus indicus[20], Macrobrachium rosenbergii[1], and Nephrops norvegicus[21]
Summary
Anaesthetics are widely used to reduce physiological stress and mechanical damage in aquaculture and fisheries during netting, handling, sampling, and transportation[1,2,3]. MS-222 is not effective for most cultured crustacean species[11]. The effectiveness of anaesthetics often varies according to species, age, weight, temperature, dose, and interactions among these factors. Our previous study demonstrated that menthol dose, water temperature and shrimp size significantly influence anaesthesia and survival rate in P. sinensis[15]. The Chinese grass shrimp (Palaemonetes sinensis; Sollaud, 1911) is a 2–5 cm species belonging to the Palaemonidae family of decapod crustaceans, and it is widely distributed in China and adjacent areas[16]. P. sinensis has a long history of human consumption in China and often draws higher market prices than those of penaeid species. The effects of water temperature and body weight on the efficacy of anaesthetics were tested
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