Population Consequences of Acoustic Disturbance – Marine environment

This project set out to identify whether right whales make any short-term behavioural responses to the presence of low-frequency vessel noise, which is important for two reasons. Firstly, after research showed that right whale populations are not recovering despite the termination of whaling in the North Atlantic Ocean. And secondly, because these whales are experiencing considerable disturbance and harm from a number of sources, including pollution, disease, entanglement and collisions with vessels. Identifying which factor(s) are having the most significant effect on right whales’ reproduction is seen as a key step in their conservation.

Right Whale fluke

Right Whale fluke

Methodology

Small acoustic recorders coupled with three-dimensional orientation sensors were temporarily attached to free-ranging right whales to record both the sounds they produced and those they heard. Low-frequency vessel noise recorded by these devices was quantified in one-third octave bands, and the behavioural responses of whales, including stroke rate and amplitude, during the highest levels of vessel noise were quantified and compared.

Challenges

Separating the flow noise produced by increases in the whale’s own movement from the vessel noise from external sources required detailed analysis and filtering. Additionally, no complimentary visual data was available on the sources of recorded noises (i.e. what type of vessel was most frequently recorded). However, Baker Consultants’ previous experience relating to working with low-frequency ambient noise from different types of sources was used to identify critical thresholds related to vessel and biological noise.
Finally, changes in behaviour occurred in response to other stimuli, such as other whales nearby or decisions related to foraging (exhausted or improved opportunities), which could not be documented on the remotely recorded data. Detailed analyses of behavioural data and knowledge of overall behavioural patterns in this species were necessary to classify behaviours based on their three-dimensional orientations and broader context.

Outcomes

Few differences in stroke rate and amplitude between high and low noise levels were detected and the whales recorded did not seem to be responding to vessel noise at low or even medium levels. This could indicate why collisions with vessels occur.
One potential explanation for this is that, in areas where foraging opportunities are good, whales may endure stresses to maximise their energy gain. Therefore, determining the long-term effects of this trade-off are crucial before any permanent developments are made. In the meantime, the best way to reduce the likelihood of a significant negative effect on right whale behaviour is to avoid areas of such importance to a population’s survival and success. Such sites include high quality foraging and breeding sites.

Why Baker Consultants Marine team?

Baker Consultants Marine are experienced in the biology of marine mammals and knowledgeable about their unaltered behaviour in specific habitats. This is extremely important when determining the effects of noise exposure. For instance, linking the presence of noise with population-level effects is difficult and requires both specialist analysis and thorough planning at the data collection stage. We are also experienced in identifying multiple low-level effects as well as a single higher-level effect, which must both be taken into account for mitigation planning.
At Baker Consultants, we acknowledge that collaboration with other research partners and commercial organisations for data sharing is vital for project success.