Extreme roll angles in Argentine sea bass: could refuge ease posture and buoyancy control of marine coastal fishes?

JAVIER CIANCIO; LEONARDO VENERUS; GASTON TROBBIANI; LUCAS BELTRAMIN; ADRIAN GLEISS; SERENA WRIGTH; BRAD NORMAN; MARK HOLTON; RORY WILSON

MARINE BIOLOGY

SPRINGER

Lugar: Berlin; Año: 2016 vol. 163 p. 90 - 101

0025-3162

The swim bladder provides a mechanism for buoyancyregulation in teleosts. However, in certain species, its location can result inan unstable body position, with associated energetic costs assumed formaintaining posture in addition to the energetic demands from swimbladdervolume regulation. Direct observations show that some body-compressed, cave-refugingteleosts that nominally operate near neutral buoyancy may adopt unusual bodyattitudes within crevices. We hypothesize that these fishes may relax theirbuoyancy and posture control mechanisms during periods of rest. A predictionderived from this is that resting fish may adopt a wide range of roll angles(i.e., rotation about their longitudinal axis) inside caves. To quantify thisbehaviour and for testing this hypothesis, tri-axial accelerometers weredeployed on free-living, cave-refuging Argentine sea bass Acanthistius patachonicus, and the relationship between roll angleand a proxy for activity (defined as the vectorial dynamic body acceleration, VeDBA),was analyzed. The results were compared with data available for three other speciesof fishes with disparate body forms and life styles: the pelagic whale shark Rhincodon typus, the dorso-ventrallycompressed benthic great sculpin Myoxocephaluspolyacanthocephalus, and the fusiform and demersal Atlantic cod Gadus morhua. Inactive Argentine seabass adopted a wide variety of roll angles, including extreme ones exceeding 80˚,but had lower roll angles closer to an upright posture primarily associatedwith higher activity levels. In contrast, the great sculpin and Atlantic codboth rested at a close to upright roll angle but had higher activity levelsassociated with larger roll angles. Whale shark did not rest for the durationof the recorded period and also showed higher activity levels associated withlarger roll angles. We propose that relaxation of buoyancy and posture control mayhelp to reduce the metabolic rate in laterally-compressed, cave-refuging fishesduring periods of rest within crevices.