Todd-Pearson, S., 2004.  Growth rate of the gastropod mollusk Hexaplex nigritus: implications for fishery management in the Gulf of California.  Gulf of California Conference, Tucson, AZ, June, 2004.

Hexaplex nigritus, commonly known as the black murex, is a commercially important species of gastropod in the northern Gulf of California. Effective management of this fishery requires that the species’ growth rate is known. I analyzed the δ¹⁸O content of samples of H. nigritus shell taken at varying distances from the shell’s growing edge in an approximately 16 cm long specimen from Bahia la Choya, Sonora, Mexico. δ¹⁸O values vary from 1.69 to –1.73 per mil and showed two cycles in the final 45.91 mm of the shell. Because δ¹⁸O varies inversely with the water temperature these δ¹⁸O cycles probably represent two years of growth. The average rate of growth in the final two years of life of this specimen is 21.30 mm/yr. This compares with an average growth rate of 35.43 mm/yr in Strombus gigas, a commercially harvested species in the Caribbean. The preliminary results from this research suggest that H. nigritus has a slower growth rate. This growth rate of H. nigritus indicates that the murex fishery is likely to be sustainable at levels somewhat lower than the fishery of Strombus gigas.