Table of Contents

• Coverage
• Dataset Description
  • Methods & Sampling
  • Data Processing Description
• Data Files
• Parameters
• Instruments
• Deployments
• Project Information
• Funding

Integrated, area scattering values, or Natuical Area Scattering Coefficients (NASC) are provided from two cruises in the Guaymas Basin that occurred in June 2010 and June 2011. Also included are the time (UTC) and location at the start and end of each integration bin, mean depth of the exclusion line for each bin, and the average thickness of the integrated cell.

Raw acoustic scattering data (.raw files) are extremely large. These are archived at Oregon State University and will be shared using physical media upon request.

Acoustic data were collected nearly continuously using Simrad EK60s at 4 frequencies (38, 70, 120, and 200 kHz). Split beam transducers (Simrad model numbers: 38-12, 70-7c, 120-7c, 200-7c) were mounted 1.5 m below the surface on a rigid pole. Each transmitted a 512 us pulse as frequently as possible for the water depth. Raw data were stored using Simrad ER60 software.

Noise from splash down, electrical interference, and CTD casts were flagged as ‘bad data’ using Echoview software before integration. Acoustic backscattering values at 38 kHz that were greater than -75 dB were integrated in 1 km horizontal bins from depths of 5m to 500m or 1 m above the bottom, whichever was shallower. These integrated, area scattering values or Nautical Area Scattering Coefficients (NASC: m2 nmi-2) are provided.

BCO-DMO Processing Notes:
- Modified parameter names to conform with BCO-DMO naming conventions.
- Replaced values of '999' in the lat and lon columns with 'nd' to indicate 'no data'.
- Reformatted display of time from HH:MM:SS to HHMM.mmmm

This project concerns the ecological physiology of Dosidicus gigas, a large squid endemic to the eastern Pacific where it inhabits both open ocean and continental shelf environments. Questions to be addressed include:
1) How does utilization of the OML by D. gigas vary on both a daily and seasonal basis, and how do the vertical distributions of the OML and its associated fauna vary?
2) What behaviors of squid are impaired by conditions found in the OML, and how are impairments compensated to minimize costs of utilizing this environment? and
3) What are the physiological and biochemical processes by which squid maintain swimming activity at such remarkable levels under low oxygen conditions?

The investigators will use an integrated approach involving oceanographic, acoustic, electronic tagging, physiological and biochemical methods. D. gigas provides a trophic connection between small, midwater organisms and top vertebrate predators, and daily vertical migrations between near-surface waters and a deep, low-oxygen environment (OML) characterize normal behavior of adult squid. Electronic tagging has shown that this squid can remain active for extended periods in the cold, hypoxic conditions of the upper OML. Laboratory studies have demonstrated suppression of aerobic metabolism during a cold, hypoxic challenge, but anaerobic metabolism does not appear to account for the level of activity maintained. Utilization of the OML in the wild may permit daytime foraging on midwater organisms. Foraging also occurs near the surface at night, and Dosidicus may thus be able to feed continuously. D. gigas is present in different regions of the Guaymas Basin on a predicable year-round basis, allowing changes in squid distribution to be related to changing oceanographic features on a variety time scales.

This research is of broad interest because Dosidicus gigas has substantially extended its range over the last decade, and foraging on commercially important finfish in invaded areas off California and Chile has been reported. In addition, the OML has expanded during the last several decades, mostly vertically by shoaling, including in the Gulf of Alaska, the Southern California Bight and several productive regions of tropical oceans, and a variety of ecological impacts will almost certainly accompany changes in the OML. Moreover, D. gigas currently supports the world's largest squid fishery, and this study will provide acoustic methods for reliable biomass estimates, with implications for fisheries management in Mexico and elsewhere.

This award is funded under the American Recovery and Reinvestment Act of 2009 (Public Law 111-5). This is a Collaborative Research project encompassing three NSF-OCE awards.

Background Publications:
Stewart, J.S., Field, J.C., Markaida, U., and Gilly, W.F. 2013. Behavioral ecology of jumbo squid (Dosidicus gigas) in relation to oxygen minimum zones. Deep Sea Research Part II: Topical Studies in Oceanography, 95, 197-208. doi:10.1016/j.dsr2.2012.06.005.
Gilly, W.F., Zeidberg, L.D., Booth, J.A.T, Stewart, J.S., Marshall, G., Abernathy, K., and Bell, L.E. 2012. Locomotion and behavior of Humboldt squid, Dosidicus gigas, in relation to natural hypoxia in the Gulf of California, Mexico. The Journal of Experimental Biology, 215, 3175-3190. doi: 10.1242/jeb.072538.

Related Project: Physiological limits to vertical migrations of the pelagic, jumbo squid, Dosidicus gigas in the Gulf of California