Reverse Diel Vertical Migration: An Escape from Invertebrate Predators

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Science  24 Jun 1983:
Vol. 220, Issue 4604, pp. 1404-1407
DOI: 10.1126/science.220.4604.1404


The marine copepod Pseudocalanus sp. exhibits an unusual reverse diel vertical migration in Dabob Bay, Washington, concurrently with a normal vertical migration by nocturnal invertebrate predators. Reduced spatial overlap with predators appears to decrease mortality rate of adult female Pseudocalanus. A life table analysis suggests that the demographic disadvantage associated with daily migration across a thermal gradient can be overcome if mortality is reduced by as little as 16 percent.