Identification and estimation of size from the beaks of 18 species of cephalopods from the Pacific Ocean

Abstract

A method of identifying the beaks and estimating body weight and mantle length of 18 species of cephalopodsfrom the Pacific Ocean is presented. Twenty specimens were selected from each of the following cephalopod species: Symplectoteuthis oualaniensis, Dosidicus gigas, Ommastrephes bartramii, S. luminosa, Todarodes pacificus, Nototodarus hawaiiensis, Ornithoteuthis volalilis, Hyaloteuthis pelagica, Onychoteuthis banksii, Pterygioteuthis giardi, Abraliopsis affinis, A. felis, Liocranchia reinhardti, Leachia danae, Histioteuthisheteropsis, H. dofleini, Gonalus onyx, and Loligo opalescens. Dimensions measured on the upper and lower beakare converted to ratios and compared individually among the species using an analysis of variance procedure with Tukey's omega and Duncan's multiple range tests. Significant differences (P =0.05) observed among thespecies' beak ratio means and structural characteristics are used to construct artificial keys for the upper andlower beaks of the 18 species. Upper and lower beak dimensions are used as independent variables in a linearregression model with mantle length and body weight (log transformed). (PDF file contains 56 pages.)