Human Threats

The different potential threats identified for cetaceans are numerous but this project will focus on maritime traffic, including whale watching, ambient noise level, and marine litter. Those threats will be studied spatially and temporally, categorising them by intensity, type or quantity.

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Marine traffic

Two sources of data will be used to estimate maritime traffic:

  • Automatic Identification System (AIS; in Madeira and Azores)
  • GPS units installed on WW boats (in Madeira).

Traffic intensity will be calculated using statistical models according to boat categories, including cruise and cargo ships, tankers, fishing vessels, leisure and WW boats. The distribution of fishing boats will also help to identify fishing grounds.

Ambient noise

Ambient noise will be measured using either portable (Madeira) or bottom-mounted (Azores) calibrated hydrophones. Recordings will enable characterizing the spatial and temporal variations in background noise and ship noise as sound pressure levels in the frequency bands used by cetaceans to emit and receive sounds. Additionally, in Madeira, the sound of different WW boats will also be recorded with the same purpose.

Marine litter

Marine litter has increased in many areas around the world and can be found regularly in stranded animals. Ingestion of marine litter may occur either because of misidentification of litter items as natural prey, or accidentally during feeding and normal behaviour. Serious effects of ingested litter are the blockage of the digestive tract and internal injuries by sharp objects, which can be the cause of mortality. Entanglement in marine litter has been reported for numerous species and can cause limited mobility and restricted movement (leading to starvation), suffocation, laceration, subsequent infection, and possible mortality in marine life.

Marine litter data has been collected during the distance sampling surveys made by the MWM around Madeira. Their characteristics, i.e. plastic bags, plastic bottles, other type of plastics, fishing gear, buoy, wood or glass bottle are available to model their distribution. The temporal evolution of their density will also be investigated.