2019 RAMP assessment

In 2019, the tagging procedure was replicated to examine behavioural effects of tagging in more detail. A total of 96 adults (52 ripe, 44 spent) were captured between 19 May and 25 June 2019 from the White Rock Fish Ladder. Water temperature ranged from 9 to 11˚C in May (start of the run) to 15 to18˚C in June (end of the run). Tag burden ranged from 0.3% to 0.7%. Each fish was sexed, weighed and measured after being anesthetized with 200 mg/L of MS-222 (Table 1), and tagged as per the pilot trials. All incisions were closed with two simple, interrupted sutures.

Following surgeries, fish were recovered for 5 min in a closed, aerated 100 L tank to allow recovery from anesthesia. When the lid of the tank was removed, the behavioural condition of the fish was assessed based on RAMP methods previously described for other taxa [e.g., 29]. The reflexes tested included: ventilation, orientation, swimming vigour, light response and tactile response. Each reflex was assigned a score of 0 if non-impaired, and 1 if impaired. Ventilation was considered unimpaired if the fish exhibited regular opercular movement for 30 s. An unimpaired orientation response was noted if the fish maintained vertical equilibrium in the water, and unimpaired swimming consisted of sustained, regular movement for at least 30 s. A startle response was expected for both the light (lifting tank lid) and tactile (tail grab) stimuli, in which unimpaired fish show rapid forward motion in response to the stimuli. Total RAMP scores for individuals were calculated as a proportion of the five measured reflex scores (0 = no reflexes impaired; 1 = all reflexes impaired). Fish were visually inspected for signs of acute stress or mortality ~20 min following the final surgery, and after 24 h, however longer holding was not possible.