Vertical distribution and mortality of overwintering Calanus

• DOI: 10.4319/lo.2001.46.6.1494
• Publication Date: 2010-06-30T20:22:59Z
• Authors: Espen Bag×ien; Stein Kaartvedt; Dag L. Aksnes; Ketil Eiane
• Keywords: Mesopelagic zone; Calanus finmarchicus; Overwintering; Fjord; Calanus

Overwintering Calanus spp. were studied in four Norwegian fjords with different predator regimes and ranging depth from 380 to 1300 m. Three held both the planktivorous mesopelagic fish Maurolicus muelleri Benthosema glaciale invertebrate predators, whereas one lacked but had especially high abundance of several predators. Co‐occurrence C. finmarchicus , helgolandicus glacialis rendered distinction between effects environmental conditions inherent species properties choice difficult. The highest daily per capita mortality rate for was estimated at 0.024–0.027 d ‐1 (95% CI) a fjord clearest water. Predation by M. B. alone could explain winter mortality. devoid particularly rich predators gave lowest rate; 0.008–0.009 CI). Our results indicate that pose stronger predatory threat than invertebrates overwintering . This concurs selection oceanic habitats below depths where can forage efficiently sight.