Buoyancy adjustment after swimbladder puncture in cod Gadus morhua: An experimental study on the effect of rapid decompression in capture-based aquaculture

Abstract

Swimbladder puncture occurs frequently during fishing operations employed in capture-based aquaculture (CBA). The function, survival and welfare of cod Gadus morhua following controlled swimbladder puncture in the laboratory was investigated. Anaesthetised cod (n=30) were exposed to reduced pressure using a vacuum chamber and their swimbladders were punctured. The pressure reduction before puncture (~70%), location of the swimbladder puncture sites near the pin bones, intraperitoneal gas evacuation path leading to the anal area and rapid repair mechanism, among other puncture characteristics, were consistent with previous findings. The mortality was low (~6%) during the procedure and did not differ from that of the control group. The experimentally punctured cod were challenged by swimbladder reinflation in a flow-through pressure chamber supplied with a surveillance camera and remote pressure regulation. The punctured fish were capable of swimbladder inflation shortly after puncture and their buoyancy acclimation rates were similar to those of the control fish, with a mean filling rate of 0.22 m h⁻¹. These experiments indicate that swimbladder puncture has minor short-lived and reversible effects on the welfare of the fish.

Keywords:

• Fish capture
• live storage
• pressure reduction
• fish welfare

Published in collaboration with the University of Bergen and the Institute of Marine Research, Norway, and the Marine Biological Laboratory, University of Copenhagen, Denmark

Published in collaboration with the University of Bergen and the Institute of Marine Research, Norway, and the Marine Biological Laboratory, University of Copenhagen, Denmark

Acknowledgements

The authors thank A.-B. Skar Tysseland for drawing Figures 1a and 2, G. Bøthun for statistical guidance, S. Blænes for technical help in construction of the pressure chamber and K.Ø. Midling for discussions. This study was financed by the Research Council of Norway; project 173538 PHYSBEWEL (Physiological and behavioural indicators of fish welfare assessment in aquaculture and fish capture). The study complies with the Norwegian regulations on animal experimentation, approval number 446 and 456, IMR, Austevoll 2008.

Notes

Published in collaboration with the University of Bergen and the Institute of Marine Research, Norway, and the Marine Biological Laboratory, University of Copenhagen, Denmark