Using statolith shape analysis to identify five commercial Loliginidae squid species in Chinese waters

Abstract

Identification of squids in the family Loliginidae is a time-consuming exercise because of the highly overlapping distributions of species and their overall similarity (fin shape and size, sucker ring dentition, and color). Identifying squid based on statolith morphology is considered more accurate than identifying species based on beaks or gladius morphology. We report and compare the statolith shape of five commercially Loliginidae squid (Uroteuthis (Photololigo) duvaucelii, U. edulis, U. chinensis, Loliolus beka, L. japonica) to determine how well these structures discriminate species. Based on statolith morphology, variation in the lateral and dorsal domes enables an 84.8% success rate at classifying species. Environmental factors correlate with statolith shape, and for vertically migrating squid, statolith relative size decreases with increased depth of habitation. Statolith morphology can be used to effectively and accurately identify species of Loliginidae squid occurring in Chinese waters, and may prove valuable for identifying and managing squid resources.