Cetacean Stock Assessment In Relation To Exploration And Production Industry Sound

Four projects were commissioned to analyse trends in various cetacean stocks that occur in marine areas of past industry operations, and to demonstrate whether industry operations could have caused any biologically significant effects to populations there. Collectively, these projects analysed cetacean population trends for the Gulf of Mexico, Southern California, Scotian Shelf, UK East Coast, Bering, Chukchi and Beaufort Seas, Eastern and Western North Pacific (Sakhalin Island and Sea of Okhotsk), Western and Eastern Australia, Africa, Argentina, east coast of the U.S., Europe, North Sea, Norwegian Sea, Southern Irish Sea, and Atlantic Margin. Environmental effects, such as the El Niño/Southern Oscillation, the North Atlantic Oscillation, and commercial whaling were included in the analyses.

In the western Atlantic, a population change in sperm whales was positively correlated with the number of seismic operations. Otherwise, no declines were found that statistically correlated with industry activities. All other population declines where industry worked were correlated with changes in the physical environment, pollution, fisheries by-catch, ship strikes and other factors. The possible role of industry operations in these declines could not be statistically separated from those of the other factors. Conversely, many population increases occurred as whales recovered from commercial whaling. Ongoing industry operations at the same time and in the same ocean areas did not prevent these increases.

Objectives and methods

The four contractors used various approaches to analyse existing population data from different oceanographic regions. Access to seismic survey data that was suitable for statistical analysis of spatial and temporal trends was limited. However, two of the studies looked at selected data from these data sets. Various linear models were tested.

Importance

No analysis to date has shown any significant risk of impact from seismic survey activity at the population level. Specific populations (sperm, fin, and humpback whales off California, humpback whales off the west coast of Australia) have increased during the period of overlapping industry activity. There is a need to continue data collection and analysis to support the limited findings to date. Contractors concluded that past methods used to survey cetacean populations were inadequate for statistically separating human effects from the other factors that possibly drove population trends.

Links to other research

Cetacean stock trends are also analysed by the International Whaling Commission.

Institutions/PIs

• Project 1: CEFAS (Frank Thomsen)
• Project 2: LGL Ltd.
• Project 3: Sea Mammal Research Unit, University of St. Andrews (Nicola Quick)
• Project 4: SeaWatch (Peter G.H. Evans)