Modeling the effect of boat traffic on the fluctuation of humpback whale singing activity in the Abrolhos National Marine Park, Brazil

Renata S. Sousa-Lima, Christopher W. Clark

Abstract


Since the moratorium on whaling, the Brazilian government and local Non-Govermental Organizations (NGOs) have adopted and encouraged a more sustainable use of whales as tourist attractions. Nevertheless, concerns about boat traffic impacts on whale population health have arisen, especially in protected areas such as marine parks. The Abrolhos Marine National Park is the seasonal habitat for the breeding population of humpback whales in the Western South Atlantic. We acoustically monitored 7% of the park area during 26 days using marine autonomous recording units and evaluated the responses of whales to boat traffic by measuring changes in male singing activity. The recorded humpback whale songs were analyzed to locate and count individual singers. We modeled the fluctuation in the number of singers over time in response to: number of acoustic boat events, tide height, lunar phase, hour of the day, the quadratic function of hour of day, day of the season, and presence of light. Generalized linear models were used to fit the singer count data into a Poisson distribution and log link. We found an important negative effect of boat traffic on singing activity. There is evidence that the interaction between phases of the moon and the quadratic function of hour of day also affect singing behavior. Adaptive management should aim at reducing the number of noise events per boat, which can improve the whale watching experience and reduce the impact on male singing behavior.

Keywords


Aquaculture; Computer networks; Environmental protection; Fisheries; Mathematical models; Parks; Poisson distribution; Quadratic programming; Societies and institutions; Marine parks; National parks; Quadratic functions

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