Could whales have maintained a high abundance of krill?

Authored by Jay Willis

Date Published: 2007

Sponsors: No sponsors listed

Platforms: No platforms listed

Model Documentation: Other Narrative Mathematical description

Model Code URLs: Model code not found

Abstract

Question: Several million large whales were killed between 1900 and 1970. All these whales preyed on krill (Euphausia superba). Why has krill population abundance declined after the elimination of their primary predator? Hypothesis: Krill have changed their behaviour due to the absence of whales and this change in behaviour has resulted in a decrease in krill abundance. Methods: I reproduced a computer model of krill life history. I then extended the model as an individual-based model to show the effects of habitat choice on individual lifetime reproductive success and abundance. Conclusions: In the context of our current understanding of krill physiology, predator-invoked behaviour may lead to increased population abundance and, without the predator, natural selection may favour behaviour that would lead to lower abundance. This reverses the predictions of mass balance ecosystem models.

Tags

behavior Ecosystem zooplankton growth Recruitment Antarctic krill Euphausia-superba Predators Southern-ocean Blue whale