Schmidt V.,University of New Hampshire |
Weber T.C.,University of New Hampshire |
Wiley D.N.,Stellwagen Bank National Marine Sanctuary |
Johnson M.P.,Woods Hole Oceanographic Institution
IEEE Journal of Oceanic Engineering | Year: 2010
A long-baseline (LBL) acoustic system has been developed for the tracking of humpback whales (Megaptera novaeangliae) that have been tagged with digital acoustic recording devices (DTAGs), providing quantitative observations of submerged whale behavior during bubble net feeding. The system includes three high-frequency acoustic sources deployed from small boats that follow the whale after the animal has been tagged. Integrated global positioning systems (GPSs) provide positioning and synchronized operation of the sources. Time-encoded acoustic signals from the sources are recorded along with whale vocalizations and ambient noise on the whale tag. Time-of-flight measurements, as measured by the tag acoustic data, are converted to range from the whale to each source with a measured sound-speed profile. A nonlinear least squares solution is then solved for the whale's position with a nominal positional fix rate of once per second. The system is demonstrated with data collected from a tagged animal in summer 2007. Dead-reckoned track generation methods commonly used in previous studies are shown to capture the qualitative nature of the whale track, albeit with poor absolute positional accuracy, and to distort the track when the whale's movement is predominantly vertical. In contrast, the LBL data can provide quantitative measures of whale behavior. Transit speeds between bubble net feeding events for this case study are found to range from 0.7 to 1.9 ṁ s-1(n=8). The mean diameter of bubble net curtains are measured to range from 9.6 to 10.9 m. Whale speeds during bubble net rotations vary from 1.0 to 1.9 ṁ s-1 (n=6). © 2005 IEEE.
Hatch J.M.,Integrated Statistics Inc. |
Wiley D.,Stellwagen Bank National Marine Sanctuary |
Murray K.T.,National Oceanic and Atmospheric Administration |
Welch L.,U.S. Fish and Wildlife Service
Conservation Letters | Year: 2016
Identifying the overlap of commercial fishing grounds and seabird habitat can suggest areas of high bycatch risk and inform management and mitigation measures. We used Bayesian state space modeling to describe the movements of 10 satellite-tagged Great Shearwaters and a bivariate kernel density technique to investigate spatial overlap with commercial fishing effort to predict areas of high bycatch in the Gulf of Maine. We then used contemporaneous fishery observer data to test the validity of our predictions, highlighting an area constituting 1% of the Gulf of Maine as having the highest bycatch risk that accounted for 50% of observed takes. Fishery observer data also provided insights into characteristics of the seabird-fishery interactions. Our results indicate that a relatively small number of satellite-tagged seabirds, when combined with fishery-dependent data, can lead to identifying high-bycatch areas, particular fishing practices that might increase risk, and fishing communities that could be targeted for education/mitigation. © 2016 Wiley Periodicals, Inc.
Mussoline S.E.,Northeast Fisheries Science Center |
Mussoline S.E.,Woods Hole Oceanographic Institution |
Risch D.,Northeast Fisheries Science Center |
Hatch L.T.,Stellwagen Bank National Marine Sanctuary |
And 4 more authors.
Endangered Species Research | Year: 2012
Ship strikes are a major cause of anthropogenic mortality for the endangered North Atlantic right whale Eubalaena glacialis. Year-round data on animal presence are critical to managing ship strike mortality. Marine autonomous recording units were deployed throughout the Stellwagen Bank National Marine Sanctuary (SBNMS, Massachusetts Bay, USA) for 13 mo from January 2006 to February 2007 and on Jeffreys Ledge (JL, Gulf of Maine, USA) for 7 mo from November 2004 to May 2005 to determine whether passive acoustic monitoring (PAM) can improve information on right whale occurrence. Automated detection and manual review were used to determine presence and absence of right whale up-calls. In SBNMS, up-calls were detected year round, except during July and August, and calling rates were highest from January through May, peaking in April. In JL, up-calls occurred throughout all recording months, with the highest numbers from November through February. Up-calls were heard extensively in the wintertime throughout SBNMS and JL, suggesting that these areas are important overwintering grounds for right whales. Additionally, up-calls showed a strong diel trend in both areas, with significantly more calls occurring during twilight than dark and light periods. These data indicate that right whales are present more often and over longer time periods in the western Gulf of Maine than previously thought using conventional visual techniques. Finally, this study demonstrates the utility of PAM in providing a detailed and long-term picture of right whale presence in an area that poses a significant risk of anthropogenic mortality. © Inter-Research 2012.