Shape, size and density of daytime surface swarms of the euphausiid Meganyctiphanes norvegica in the Bay of Fundy

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Abstract
Daytime surface swarms of Meganyctiphanes norvegica in the Bay of Fundy were examined using a variety of techniques to provide measurements of their shapes, sizes and densities. Shapes and sizes were determined from two aerial photographs: swarms were spherical, ribbon-like or amorphous. were up to 28 6 m long and ranged in area from 0.4–111 7 m 2 . Densities were measured by a bag-sampling device which gave figures of up to 41 000 animals m −3 by photographic methods which gave figures of up to 770 000 animals m −3 and by a plankton net which gave maximum values of six animals m −3 Using the photographic method the maximum euphausud biomass was estimated to be 154 kg m −3 within swarms and the largest swarm measured was estimated to contain up to 2 1 tonnes of M. norvegica . Mean patch biomass estimates for the two aerial photographs ranged from 77.8–778 g m −3 and 15 6–155.6 g m −3 which are similar to figures obtained by other authors using integrating sampling techniques at depth.

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