TY - JOUR
T1 - Differences in swimbladder volume between Baltic and Norwegian spring-spawning herring
T2 - Consequences for mean target strength
AU - Fässler, Sascha M. M.
AU - Gorska, Natalia
AU - Ona, Egil
AU - Fernandes, Paul G.
N1 - Funding Information:
SMMF acknowledges the support received through an ORSAS award of the British government, a studentship of St Andrews University (Scotland) and an Ausbildungsbeitrag of the Kanton Basel-Landschaft (Switzerland).
Funding Information:
This work was partly funded by the University of Gdańsk (Grant BW 1330-5-0129-7).
PY - 2008/8
Y1 - 2008/8
N2 - Fish swimbladders, where present, contribute most to the scattering of sound by fish, as measured by the target strength (TS). The volumes of the swimbladders of two different European stocks of Atlantic herring were compared to consider the effect on estimates of TS. Swimbladder volumes of Baltic and Norwegian spring-spawning herring (Clupea harengus) were measured, together with individual herring fat content. Swimbladder volumes were found to differ significantly between the two herring stocks. Baltic herring have a larger swimbladder volume, which is suggested to be associated with the fish's low fat content, which in turn may be linked to its specific energy budget and the low salinity of the Baltic Sea. A buoyancy model that considered the different salinity conditions and fat proportions was used to evaluate the observed differences in swimbladder volume. The swimbladder volume data were subsequently used to model the mean target strength as a function of depth and growth pattern. Backscattering of the swimbladder was modelled using the modal-series-based deformed-cylinder model (MSB-DCM), describing the swimbladder as a gas-filled, elongated prolate spheroid. The fish body component was modelled as a fluid-filled ellipsoid using the distorted wave Born approximation (DWBA). Modelling results support a different TS-to-size relationship for Baltic herring, with a stronger echo, due to the larger swimbladder. Depth- and length-dependent TS relationships based on the model results are suggested.
AB - Fish swimbladders, where present, contribute most to the scattering of sound by fish, as measured by the target strength (TS). The volumes of the swimbladders of two different European stocks of Atlantic herring were compared to consider the effect on estimates of TS. Swimbladder volumes of Baltic and Norwegian spring-spawning herring (Clupea harengus) were measured, together with individual herring fat content. Swimbladder volumes were found to differ significantly between the two herring stocks. Baltic herring have a larger swimbladder volume, which is suggested to be associated with the fish's low fat content, which in turn may be linked to its specific energy budget and the low salinity of the Baltic Sea. A buoyancy model that considered the different salinity conditions and fat proportions was used to evaluate the observed differences in swimbladder volume. The swimbladder volume data were subsequently used to model the mean target strength as a function of depth and growth pattern. Backscattering of the swimbladder was modelled using the modal-series-based deformed-cylinder model (MSB-DCM), describing the swimbladder as a gas-filled, elongated prolate spheroid. The fish body component was modelled as a fluid-filled ellipsoid using the distorted wave Born approximation (DWBA). Modelling results support a different TS-to-size relationship for Baltic herring, with a stronger echo, due to the larger swimbladder. Depth- and length-dependent TS relationships based on the model results are suggested.
KW - Baltic herring
KW - Depth-dependent target strength
KW - Norwegian spring-spawning herring
KW - Swimbladder volume
KW - Target strength model
UR - http://www.scopus.com/inward/record.url?scp=44749091088&partnerID=8YFLogxK
U2 - 10.1016/j.fishres.2008.01.013
DO - 10.1016/j.fishres.2008.01.013
M3 - Article
AN - SCOPUS:44749091088
SN - 0165-7836
VL - 92
SP - 314
EP - 321
JO - Fisheries Research
JF - Fisheries Research
IS - 2-3
ER -