Bombs and Blue Marlin
Longevity of blue marlin (Makaira nigricans) remains unresolved. Use of fin spines and sagittal otoliths for age reading has led to unconfirmed longevity estimates of close to 20 years. Age validation has been elusive because large individuals are rare and a technique that can be applied to the structures that provide estimates of age was absent. Use of otolith chemical signatures has been limited by sagittal otoliths that are very small—whole otolith mass of adult blue marlin can reach 10 mg for the largest fish. Recent advances in the detection limits of radiocarbon (14C) with accelerator mass spectrometry—coupled with recently acquired knowledge of marine bomb 14C signals spanning the tropical Pacific Ocean—have led to an opportunity to age blue marlin from small amounts of otolith material. In this study, otoliths from a recently collected 1245 lb. (565 kg) female blue marlin at 146 inches (3.71 m) lower jaw fork length were analyzed for 14C. Using a series of deductions in the bomb 14C dating method the age of this “grander” blue marlin was confirmed.