Fig. (1) (a) Dorsal extraction of sagittal otoliths of a Glaucosoma herbraicum through an incision that opens the top of the head at the base of the nape above the eyes. (b) Ventral extraction of sagittal otoliths of a Glaucosoma herbraicum at the base of the cranium (anterior to left) through the otic capsule (comprised of the exoccipital (Exo.), basioccipital (Bas.) and parasphenoid (Par.) bones) by cutting the suture between the basioccipital and exoccipital bones at about a 45° angle using bone cutters and levering open. SL - subopercular ligament.