The existence of fishbone fluctuations at frequencies comparable to those of geodesic acoustic modes (GAM) and beta induced Alfvén eigenmodes (BAE) has been demonstrated theoretically in a recent work (Zonca et al2007 Nucl. Fusion47 1588). Here, we show that observation of fishbones at unexpectedly high frequencies in JET (Nabais et al 2005 Phys. Plasmas12 102509) is well interpreted as experimental evidence of high (GAM/BAE range) frequency fishbones and discuss the insights concerning both supra-thermal particles as well as thermal plasma properties that can be obtained from experimental observations.