Changes of the Northern Shrimp's States in the Northern Part Sea of Okhotsk during Reproductive Cycle and Molting Cycle

Abstract

Changes of stages of redroductive cycle, molting cycle and some other features of biology of the northern shrimp (Pandalus borealis eous) were studied based on data of daily biological analysis, grouped to five days during 10 months (from March to December) of the calendar year. Materials were collected in Pritaujskiy area in northern part Sea of Okhotsk. Reproductive cycle of females lasts for two years: during first year gonads developed up to the spawning and in the second one females carried eggs on pleopods up to hatching of larvae and beginning a new cycle. Changes can be traced by the share of the relevant stages in the total number of individuals in three groups: males, females of first year reproductive cycle and females of second one. The males have two molts for the year and females, according to the spawning cycle have three molts during two years. All molts lasts 2-3 months and diverge in terms. By changes of share of females of first and second year of reproductive cycle hypothesis about vertical migrations was made. The share of females with sternal spines, that take part in process of reproduction first time, is about 45%, which means that females are able take part to three spawning cycles.