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Case Study:<br> Cetaceans
Case Study:
Cetaceans

Context

Cetaceans (dolphins, porpoises, and baleen whales) were a focus for this study because offshore wind energy facilities present significant increases in underwater noise during construction, which may affect all marine mammals. Our current lack of understanding of the hazards posed to baleen whales by offshore wind energy development make these species a particular concern for regulators in the U.S.

Download Mid-Atlantic Wildlife Studies: Distribution and Abundance of Wildlife along the Eastern Seaboard 2012-2014. This 32-page summary publication explores aspects of the mid-Atlantic ecosystem; describes our survey and analytical approaches; and presents a range of results, featuring several case studies on specific species or phenomena.

The Executive Summary for the technical report is also available here.

 

Take Home Messages

  • Relatively little is known about the migratory routes for many rare whale species in the mid-Atlantic, although data from this study, as well as other survey efforts, are beginning to fill this gap.
  • Bottlenose Dolphins may be most likely to be exposed to development activities during summer and in the northern end of the study area, as well as in western areas of the mid-Atlantic WEAs in spring and fall. Common Dolphins have a more offshore distribution, and may be particularly abundant in WEAs during winter and spring.
 

Background

Cetaceans include two major types of aquatic mammals. Toothed whales, such as dolphins and porpoises, have rows of teeth and eat fish and other large prey. They are capable of echolocation, using sound to sense objects around them. Baleen whales, including many of the large endangered whale species, eat krill, copepods, and small fish by filtering them through bristles or plates on their jaws. While baleen whales do not echolocate, they use sound for communication, particularly during the breeding season. Cetacean migratory routes are poorly defined for many species, although several are known to migrate through the mid-Atlantic. All cetaceans that occur in the U.S. are protected under the Marine Mammal Protection Act.

Acoustic disturbance from construction and operation of offshore wind facilities may affect all marine mammals. European studies have shown displacement of Harbor Porpoises during construction, though displacement during operations has been variable. There is evidence for disturbance of large whales by other anthropogenic activities, but no information is available about their interactions with offshore wind facilities, as large whales are not common in European waters where development has occurred to date. 

 

Distribution and Abundance: Baleen Whales

<p>This map shows large whale observations (Mysticeti) from boat and video aerial surveys (March 2012-May 2014).</p>
<p>Data from boat and aerial surveys included 51 baleen whales from at least five species. We observed nine North Atlantic Right Whales, which is notable for this species in the mid-Atlantic region. Among the rarest of all marine mammals, the North Atlantic Right Whale is of particular interest to regulators, and very little information exists on their movements and habitat use in the mid-Atlantic. We also observed endangered Humpback Whales and Fin Whales. Baleen whales were most frequently observed in winter, although present in small numbers year round, and were observed throughout the study area.</p>

This map shows large whale observations (Mysticeti) from boat and video aerial surveys (March 2012-May 2014).

Data from boat and aerial surveys included 51 baleen whales from at least five species. We observed nine North Atlantic Right Whales, which is notable for this species in the mid-Atlantic region. Among the rarest of all marine mammals, the North Atlantic Right Whale is of particular interest to regulators, and very little information exists on their movements and habitat use in the mid-Atlantic. We also observed endangered Humpback Whales and Fin Whales. Baleen whales were most frequently observed in winter, although present in small numbers year round, and were observed throughout the study area.

 

Distribution and Abundance: Toothed Whales

<p>These maps show the predicted numbers of Bottlenose Dolphin pods by season, based on two years of boat survey data (2012-2014); winter is not included as few Bottlenose Dolphins were present in the study area. Models used observation data from boat-based surveys and remotely sensed environmental covariate data to predict numbers of pods across the study area. Strong nearshore distributions were predicted in fall and spring, likely driven by the species' resident coastal ecotype. Dolphins were predicted to be more evenly distributed longitudinally in summer.</p>
<p>The majority of the marine mammals observed in boat and aerial surveys were dolphins and porpoises from at least five species. Bottlenose Dolphins, the most abundant delphinid in surveys, were observed primarily in spring, summer, and fall. Cold-tolerant Common Dolphins were most frequently observed in offshore areas in winter and early spring.</p>
<p>Distance from shore, primary productivity, and sea surface temperature were important predictors of Bottlenose Dolphin distributions. This is possibly because of their use of areas of high productivity for feeding, particularly in and around the mouths of the Chesapeake and Delaware Bays, and their temperature-related migratory behaviors. A more robust density gradient from west to east was observed in summer, possibly due to an influx of transient populations during the warmer period. Models suggest minimal presence of Bottlenose Dolphins within mid-Atlantic WEAs during cooler months.</p>

These maps show the predicted numbers of Bottlenose Dolphin pods by season, based on two years of boat survey data (2012-2014); winter is not included as few Bottlenose Dolphins were present in the study area. Models used observation data from boat-based surveys and remotely sensed environmental covariate data to predict numbers of pods across the study area. Strong nearshore distributions were predicted in fall and spring, likely driven by the species' resident coastal ecotype. Dolphins were predicted to be more evenly distributed longitudinally in summer.

The majority of the marine mammals observed in boat and aerial surveys were dolphins and porpoises from at least five species. Bottlenose Dolphins, the most abundant delphinid in surveys, were observed primarily in spring, summer, and fall. Cold-tolerant Common Dolphins were most frequently observed in offshore areas in winter and early spring.

Distance from shore, primary productivity, and sea surface temperature were important predictors of Bottlenose Dolphin distributions. This is possibly because of their use of areas of high productivity for feeding, particularly in and around the mouths of the Chesapeake and Delaware Bays, and their temperature-related migratory behaviors. A more robust density gradient from west to east was observed in summer, possibly due to an influx of transient populations during the warmer period. Models suggest minimal presence of Bottlenose Dolphins within mid-Atlantic WEAs during cooler months.

 

For More Information

For more information, see Chapters 15 and 17 in the technical report.
 

References

  • Bergström L, Kautsky L, Malm T, Rosenberg R, Wahlberg M, Capetillo NA, Wilhelmsson D (2014) Effects of offshore wind farms on marine wildlife—a generalized impact assessment. Environmental Research Letters 9:034012. doi: 10.1088/1748-9326/9/3/034012
  • McCauley RD, Fewtrell J, Duncan AJ, Jenner C, Jenner MN, Penrose JD, Prince RIT et al (2000) Marine Seismic Surveys - A study of environmental implications. APPEA Journal 40:692–708
  • Teilmann J, Carstensen J (2012) Negative long term effects on harbour​ ​porpoises from a large scale offshore wind farm in the Baltic—​​evidence of slow recovery. Environmental Research Letters 7:045101.​ ​doi:10.1088/1748-9326/7/4/045101
  • Teilmann J, Tougaard J, Carstensen J (2006) Summary on harbour​ ​porpoise monitoring 1999-2006 around Nysted and Horns Rev​ ​Offshore Wind Farms: Report to Energi E2 A/S and Vattenfall A/S.​ ​Ministry of the Environment, Denmark
  • Tyack PL, Zimmer WMX, Moretti D, Southall BL, Claridge DE, Durban JW, Clark CW et al (2011) Beaked whales respond to simulated and actual navy sonar. PLoS One 6:e17009. doi:10.1371/journal.pone.0017009
  • Waring GT, Josephson E, Maze-Foley K, Rosel, PE (eds) (2014) U.S. Atlantic and Gulf of Mexico Marine Mammal Stock Assessments–2013. NOAA Tech Memo NMFS NE 228. 464 p.
 
Photo Credits: Header image © kenglye; Maps © BRI
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