Some biological features and productive characteristics of Oithona similis (Copepoda) in the Sea of Okhotsk and western Bering Sea

The biological peculiarities of Oithona similis were described based on the materials from 29 complex surveys that were conducted by the TINRO Center in the Sea of Okhotsk and the western Bering Sea from 1986 to 2005 and the production of the species was estimated. In this area, O. similis produces four generations a year, viz., one in the spring, one in the fall, and two in the summer. The peak of spawning in May and June coincides with the maximum development of phytoplankton. Somatic production of O. similis in both seas becomes higher during the summer season. In this species, the largest increment in body weight begins with the copepodite stage CIV, when basic nutrients are accumulated. The average specific daily production of O. similis in the epipelagic zone of the Sea of Okhotsk and Bering Sea was 0.0092 and 0.01 in the spring, 0.043 and 0.031 in the summer, and 0.023 and 0.014 in the fall, respectively. The total somatic production of this species reached 28.318 million tons in the Sea of Okhotsk and 4.811 million tons in the Bering Sea. The Sea of Okhotsk is more favorable for the development of O. similis.