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David A. Demer
National Marine Fisheries Service
OceanographyEuphausiaKrillAntarctic krillFishery
87Publications
24H-index
1,969Citations
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Publications 85
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Large mobile predators take advantage of offshore pelagic environments that tend to be surveyed at a low temporal scale. We present results from a one-year observation of passive and active acoustics, as well as oceanographic measures, taken at a moored location 150 nmi offshore southern California in 4000 m deep pelagic waters. The passive acoustic data shows presence of delphinids and baleen, sperm, and beaked whales throughout the recording period with species-specific seasonal occurrence. Va...
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#1Timothy J. Rowell (UCSD: University of California, San Diego)H-Index: 2
#2David A. Demer (NMFS: National Marine Fisheries Service)H-Index: 24
Last. Brad Erisman (University of Texas at Austin)H-Index: 18
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Sound produced by fish spawning aggregations (FSAs) permits the use of passive acoustic methods to identify the timing and location of spawning. However, difficulties in relating sound levels to abundance have impeded the use of passive acoustics to conduct quantitative assessments of biomass. Here we show that models of measured fish sound production versus independently measured fish density can be generated to estimate abundance and biomass from sound levels at FSAs. We compared sound levels ...
5 CitationsSource
#1George R. CutterH-Index: 5
Last. David A. DemerH-Index: 24
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#1Kevin L. Stierhoff (NMFS: National Marine Fisheries Service)H-Index: 1
#2David W. Murfin (NMFS: National Marine Fisheries Service)H-Index: 2
Last. Deanna R. Pinkard-Meier (NMFS: National Marine Fisheries Service)
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4 CitationsSource
1 CitationsSource
#1Juan P. ZwolinskiH-Index: 7
#2David A. DemerH-Index: 24
Last. Beverly J. MacewiczH-Index: 4
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5 CitationsSource
#1Juan P. ZwolinskiH-Index: 7
#2David A. Demer (NMFS: National Marine Fisheries Service)H-Index: 24
The northern stock of Pacific sardine (Sardinops sagax) in the California Current Ecosystem is periodically assessed to provide harvest guidelines for the United States and Canadian fisheries. The assessment model incorporates the estimates of abundance from acoustic-trawl method (ATM) and other surveys and many parameters including a constant value for the instantaneous natural mortality coefficient (M). Here, the ATM-estimated length-structured sardine abundances for 2006–2011 are combined to ...
5 CitationsSource
#1Pingfan Meng (UCSD: University of California, San Diego)H-Index: 6
#2George R. CutterH-Index: 8
Last. David A. DemerH-Index: 24
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Multifrequency biplanar interferometric imaging (MBI) is a contemporary acoustic-data processing technology designed to remotely image the seabed or objects in the ocean. MBI requires a computationally intense data conditioning algorithm. For example, it takes a serial central processing unit (CPU) 10 seconds to process each transmission for typical survey data from of a five-beam/frequency group for split-aperture echosounders (e.g., Simrad EK60). However, because many of the computations may b...
1 Citations
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