Accelerometry of Seabream in a Sea-Cage: Is Acceleration a Good Proxy for Activity?

Abstract

Activity assessment of individual fish in a sea-cage could provide valuable insights into the behavior, but also physiological well-being and resilience, of the fish population in the cage. Acceleration can be monitored continuously with internal acoustic transmitter tags and is generally applied as a real-time proxy for activity. The objective of this study was to investigate the activity patterns of Gilthead seabream (Sparus aurata) by transmitter tags in a sea-cage and analyze correlations with water temperature, fish size and tissue weights. Experimental fish (N = 300) were transferred to an experimental sea-cage of which thirty fish (Standard Length SL = 18.3 ± 1.7 cm; Body Weight BW = 174 ± 39 g) were implanted with accelerometer tags. Accelerations were monitored for a period of 6 weeks (Nov.–Dec.) and were analyzed over the 6 weeks and 24 h of the day. At the end of the experimental period, tagged fish were again measured, weighed and dissected for tissue and filet weights, and correlations with accelerations were analyzed. Daily rhythms in accelerations under the experimental conditions were characterized by more active periods from 6 to 14 h and 18 to 0 h and less active periods from 0 to 6 h and 14 to 18 h. This W-shaped pattern remained over the experimental weeks, even with diurnal accelerations decreasing which was correlated to the dropping temperature. The increase in activity was not during, but just before feeding indicating food-anticipatory activity. Activity patterning can be useful for timing feeding events at the start of active periods, in this study between 6 and 11 h, and between 18 and 22 h. Acceleration was negatively correlated to heart and mesenteric fat mass, which was the exact contrary of our expectations for sustainedly swimming seabream. These results suggest that acceleration is a proxy for unsteady swimming activity only and research is required into the accelerations occurring during sustained swimming of seabream at various speeds.

Cardiac and behavioural responses to hypoxia and warming in free-swimming gilthead seabream, Sparus aurata

“…The low VAR m during progressive hypoxia, and absence of differences between fish in the tank and respirometers, presumably indicates that movements in the tank did not involve changes in speed, which are necessary to engender variation in acceleration (Hinch et al, 2002;Kawabe et al, 2003;Palstra et al, 2021;Tanaka et al, 2001). Thus, the gentle movements observed during hypoxia in the tank were clearly below the sensitivity of the accelerometer in the tag.…”

“…The metabolic costs of such movements are paid during recovery, rather than during the activity itself (Webb, 1978;Kieffer, 2000), so changes in f H may have been out of phase with changes in VAR m . Palstra et al (2021) concluded that acceleration was most reliable as an index of unsteady burst swimming activity in the seabream; for example, when fish are feeding. Although measures of body acceleration have also been used to predict metabolic rate in fish (Bouyoucos et al, 2017;Gleiss et al, 2010;Metcalfe et al, 2016;Wilson et al, 2013;Wright et al, 2014), it seems unlikely this will ever have the same predictive power as f H , not least because movement is only one component of metabolic activity in fish.…”

Revising the Impact and Prospects of Activity and Ventilation Rate Bio-Loggers for Tracking Welfare and Fish-Environment Interactions in Salmonids and Mediterranean Farmed Fish

“…The above findings reinforce the need of further research addressing the type of body movements that are recorded from the externally or internally implanted fish sensors. Certainly, Palstra et al (2021) pointed out that gilthead sea bream accelerations from acoustic transmitter tags (ventrally implanted) are a good proxy of unsteady swimming activity (e.g., escape reactions and aggressive or foraging behavior) in experimental sea cages, but not of sustained swimming exercise. This assumption is based on the correlations between accelerations and the weight of heart and mesenteric fat weight, which were the opposite to that found and expected in exercised training fish (Blasco et al, 2015;Rodnick and Planas, 2016;Palstra et al, 2020).…”

Determining the Effects of Environmental Events on Cultured Atlantic Salmon Behaviour Using 3-Dimensional Acoustic Telemetry

“…Acoustic telemetry techniques have been used in aquaculture for chinook salmon (e.g., Cubitt et al, 2003), Atlantic salmon (e.g., Føre et al, 2011Føre et al, , 2017, Atlantic cod (e.g., Rillahan et al, 2011;Ward et al, 2012), and gilthead seabream (e.g., Muñoz et al, 2020;Palstra et al, 2021). These studies have focused on monitoring fish positioning and behaviour in commercial sea pen settings.…”

“…The accuracy and reliability of a three-dimensional system was tested on chinook salmon (Cubitt et al, 2003). Further, acoustic telemetry has been used to infer behaviour, including vertical positioning and diel swimming patterns in farmed fish (e.g., Føre et al, 2011Føre et al, , 2017Rillahan et al, 2011;Ward et al, 2012;Muñoz et al, 2020;Palstra et al, 2021). Individual fish tags do not capture the entire pen population, but they provide access to data on individual fish (e.g., swimming speed) that is not available when using population-level echosounding.…”