Abstract:
Swordtip squid (uroteuthis edulis) is an important kind of cephalopods in China. Insight into the law that governs its growth is a crucial research direction in the field of fishery biology. Because most of the cephalopods can only live for one year, researchers usually receive many difficulties during studying the age and growth of the Swordtip squids. Beaks, containing a lot of ecological information, are a kind of the most important hard tissues of the cephalopods. In this work, we first present a study on the relationships between the lengths of various parts of the beaks and the mantle length, body weight and age of the swordtip squids by regression analysis, respectively. The study is based on 32 samples collected from the March 23 in 2015 in the fishing areas of Pearl River Estuary. It was found that the lengths of various parts of the beaks showed logarithmically dependence on the mantle length. The relations between the body weights and the lengths of various parts of the beaks mainly fit a power law. The mantle length and body weight show a typical exponential growth as a function of the age; and the characteristic time
τW for the growth of body weight is about one third of that,
τL, for the growth of the mantle length. The age of the samples is ranged from 91 d to 268 d and the spawning time is between September and October. We further established the relation between the lengths of various parts of the beaks and the mantle length, body weight and age of the swordtip squids, respectively, by artificial neural networks. The precision of the prediction can be greatly improved as compared to the regression analysis.