2008-2010 Chukchi Offshore Monitoring in Drilling Area Distribution and Relative Abundance of Marine Mammals Aerial Surveys
March 07, 2008
The Chukchi Offshore Monitoring in Drilling Area (COMIDA) aerial survey component was initiated in 2008, via an Interagency Agreement (No. M08PG20023) between the Minerals Management Service (MMS) [Department of the Interior; currently the Bureau of Ocean Energy Management, Regulation and Enforcement] and the National Marine Mammal Laboratory (NMML) [Alaska Fisheries Science Center, National Marine Fisheries Service, National Oceanic and Atmospheric Administration, Department of Commerce]. These surveys are a continuation of aerial surveys that were conducted by MMS-sponsored contractors from 1982-1991 (Ljungblad et al., 1987; Moore and Clarke, 1992) and use similar methodology. Aerial surveys remain the only practical means of assessing marine mammal distribution, population density, and habitat use in large study areas. The goal of this study is to investigate the distribution and relative abundance of marine mammals in the Chukchi Sea Planning Area (CSPA) during the open water (ice-free) months of June-October, when various species are undertaking seasonal migrations through the area. The COMIDA study area encompasses the northeastern Chukchi Sea from shore seaward, latitude 68°N to 72°N and longitude 157°W to 169°W, and overlays Lease Sale 193 (offered in February 2008). Species of interest include the bowhead whale (Balaena mysticetus), gray whale (Eschrichtius robustus), beluga (Delphinapterus leucas), polar bear (Ursus maritimus), walrus (Odobenus rosmarus), and ice seals. Increasing the understanding of marine mammal distribution, abundance and migration timing in this region will assist in decision-making to minimize impacts from petroleum exploration, development and production activities and other anthropogenic impacts.
Aerial surveys were conducted over the COMIDA study area during summer and autumn 2008-2010. This area comprises 10 survey blocks (Figure 1), which were established in the 1980s when broad-scale surveys were previously conducted (Moore and Clarke, 1992). During the first year of COMIDA (2008), spatial and temporal parameters of the surveys differed from subsequent years. Surveys in 2008 were conducted during three discrete time periods, 16 June–7 July, 3-26 August, and 21 October–10 November (Appendix 1), and transects were situated north-south, which replicated the survey design used in 1982-1991. In 2009, the timing of the surveys was expanded to nearly continuous coverage from 16 June-31 October (Appendix 2). In 2010, surveys were conducted from 1 July-31 October (Appendix 3). A major change between 2008 and 2009-2010 surveys was the revision of the survey design so that offshore transects were oriented perpendicular to the coastline (Figure 1). Under the revised survey design, a set of transect lines is generated from a single random point, designated as the “anchor.” Transects are spaced approximately 19 km (10 nm) apart and perpendicular to the coastline. In consecutive years, transects are generated from a new randomly selected anchor and placed in the same relative configuration. In this way, multi-year transect coverage will be uniform throughout the study area. The revised survey design also included a coastal transect between Pt. Barrow and Pt. Hope, Alaska.