Investigations on euphausiids in some fjords on the West Coast of Norway in 1966-1969

• Main Author: Wiborg, Kristian Fredrik
• Format: Report
• Language: English
• Published: [Fiskeridirektoratets havforskningsinstitutt] 1971
• Subjects: Norway; Meganyctiphanes norvegica; Thysanoessa inermis
• Online Access: http://hdl.handle.net/11250/114384

In 1966-1969 euphausiids (krill) were sampled in some fjords in Western Norway. Drained volumes of krill constituted 13-82 ml, exceptionally 100-167 ml per 1 000 m3. Meganyctiphanes norvegica, Thysanoessa inermis and T. raschii dominated in the order mentioned. During the day, Thysanoessa spp. kept at higher levels than M. norvegica; during the night T. raschii and part of the stock of M. norvegica accumulated close to the surface. M. norvegica had densities of 0.1-1 specimens per m3, but higher concentrations were induced in spring with electric light. Vertical layering was observed with large specimens at deeper levels. M. norvegica spawned in March-June one year old. Part of the stock survived a second spawning, a few lived for nearly three years. One year olds measured 22-31 mm (average 27 mm), two year olds 32-41 mm (average 37 mm) and three year olds 43-47 mm. In T. inermis a maximum of 1-4 specimens per m3 occurred in the upper 10-50 m during the night in January-February and October-November, at other times only 0.05-0.3 specimens per m3. T. inermis is annual in the area, spawning in March- June, with maximum in April. Length of one year olds was 17-20 mm, single second year survivors 26 mm. The two-spined form was observed in 1-3 % of the stock. T. raschii had maximum densities of 3.5 and 5.0 specimens per m3 in the upper 10 m in February and November respectively, at other times figures were very low. T. raschii is annual; spawning occurs in April-June, starting somewhat later than in T. inermis. Growth and length distributions are as a rule similar to those of T. inermis.