2.4 Fish fins move in a complex three dimensional manner
Fish fins not only are flexible, but are moved in a
three-dimensional manner during locomotion, as is evident from Figs. 3 and 4. This complexity of motion
extends to the caudal fin or tail, which is often treated
as a flat plate in theoretical models of fish propulsion
or simply included in models as an undulating portion of the body. But the caudal fin, as well as other
fins, moves in a complex manner even during steady
swimming behaviors[10,3739]. The tail of sharks is particularly noteworthy in this regard, and experimental
three-dimensional studies of shark pectoral and caudal
fin motion demonstrate that two-dimensional analyses
are not adequate to understand fin function[4042].