The behavior of Pacific herring schools in response to artificial humpback whale bubbles

There have been numerous reports of humpback whales and other marine predators deploying bubbles during foraging activities. However, the effects of bubbles on schooling prey organisms remain poorly understood. We conducted a series of laboratory experiments to gain insight into the effect of bubbles on the Pacific herring, Clupea harengus pallasi, a principal prey species of the humpback whale, Megaptera novaeangliae. The fish exhibited strong avoidance of bubbles and could be contained within a circular bubble net. The herring schools were also reluctant to swim through a curtain of bubbles even when frightened. However, herring were much more willing to cross a bubble curtain or net if there was a larger aggregation of fish on the opposite side. Individuals and small groups of herring also waited for less time before crossing than did larger groups. These experiments suggest that herring have a strong fear of bubbles and can readily be manipulated or contained within bubble nets by predators.

Multivariate Description of Pacific Herring (Clupea harengus pallasi) Stocks from Size and Age Information

Fisheries management must trade off biological conciseness with institutional and practical constraints, which may preclude separate management of all genetic stock units but should ensure long-term survival of such components in each area. The technique described here, while unable to explicitly identify genetic differences, is applicable to other species and would be particularly valuable for preliminary studies where limited resources preclude the use of expensive and analytically more complex techniques such as morphometric and meristic or electrophoretic analyses which are more suitable for that task. The method developed in this study involves the application of discriminant function and canonical variates analysis to information on size and age structure of Pacific herring (Clupea harengus pallasi) from samples representing the seven major migratory populations and other spawning aggregations in six geographical regions of coastal British Columbia. Results of the analysis quantify the separation of stocks of herring between geographical regions, and at a finer spatial scale, within all regions. Generally, one or more migratory stocks occurred together with minor stocks in each geographical region.