The use of different anaesthetics as welfare promoters during short-term human manipulation of European cuttlefish (Sepia officinalis) juveniles

Anaesthetics are frequently used to prevent injuries, stress and to promote welfare while handling animals. The efficiency of five anaesthetics for short-term handling of the European cuttlefish (Sepia officinalis) was tested in order to determine the best agent and its concentration. Ethanol (10.0, 20.0 and 30.0 mL.L− 1), clove oil (0.05, 0.15 mL.L− 1), hypothermia (8 °C), magnesium chloride (hexahydrated; 20.0, 27.0 g.L− 1) and AQUI-S® (10.9 μl.L− 1) were the selected anaesthetics. This choice was preceded by a preliminary trial, with additional agents, where 2-phenoxyethanol (10, 15, 20, 30 mL.L− 1) and MS-222® (30, 40 mg.L− 1) were used. Due to the lack of reliable results from these two agents, they were discarded. Anaesthetic procedure was performed in 85 cuttlefish juveniles with a mean wet weight of 45.69 ± 12.01 g, on a 5 L container, under hyper-oxygenated seawater (~ 200%), plus the dose of a given anaesthetic agent. After achieving induction, cuttlefish were handled for 180 s, which consisted in a weighing procedure according to a developed CCMAR protocol. Recovery from anaesthesia was performed in a tank with flow-through hyper-oxygenated water. All these procedures were video recorded and used to, a posteriori, obtain the time frames of induction, handling and recovery, as well as for the behaviour analysis during each stage.For the analysis of results and taking into account the best welfare practice, we established the following time period criteria to determine the optimum anaesthetic dose: induction < 600 s; and recovery < 900 s. Data gathered was used to build a descriptive table of behaviour related stages based on all the anaesthetic agents, which was then also used to analyse the individual data.Despite the multitude of new anaesthetics developed for marine vertebrates, with this work we verified that MgCl2, at 27 g.L− 1, is still the anaesthetic agent to be used in short-term handling of cuttlefish. Relative to other agents used, MgCl2 proved superior in ease of application, price, availability, and its minimal distressing effect on individuals. However, it's of utmost importance to increase the knowledge regarding this species physiology related to the field of animal welfare. The development of tools for the identification of possible biomolecular indicators of stress in cuttlefish and the confirmation of similar physiology to vertebrates will allow a correct verification of stress induction and reduction, when using an anaesthetic agent and during the handling process.

► We tested different anaesthetic agents in short-term handling in cuttlefish.
► We develop a behavioural table for induction, sedation and recovery.
► MgCl2 was the best in application, price, availability, and minimal distress.
► Other indicators of stress are needed.