| The primary goals of the survey are to characterize the winter distribution of hake,
the hake aggregations, and the fish within those aggregations in order to support
an evaluation of the feasibility of a future winter hake biomass survey. The project
will use data from an integrated acoustic and trawl survey off the west coast of the
U.S. from approximately south of San Diego, CA (latitude 31.6°N along the U.S. EEZ)
to approximately Newport, OR (latitude 44.6°N). Our objectives are to: - Conduct 24-hour
acoustic, trawl, oceanographic, and zooplankton operations. - Continuously sample
multi-frequency acoustic backscatter data using the ship?s Simrad EK60 scientific
echosounders (18, 38, and 120 kHz) system. Simrad EK80 broadband echosounders will
operate at 70 and 200 kHz. Collectively, the acoustic data will be used to characterize
the distribution of hake and describe hake aggregations. -- Collect acoustic data
along pre-planned diagonal transects along the coast (hereafter ?transects?). -- Collect
acoustic data over hake aggregations, where the design will be determined based on
the observed aggregation (hereafter ?adaptive transects?). - Collect stationary acoustic
data 1 hour before sunrise/sunset to 1 hour after sunrise/sunset to evaluate migration
(vertical and/or horizontal) of hake aggregations. - Conduct daytime and nighttime
trawling (Appendices 3 and 4) to verify hake aggregations and obtain specimens for
biological data (length, sex, maturity, age, ovaries, diet, genetics, etc.). -- Multiple
trawl samples may be taken on a single hake aggregation to evaluate heterogeneity
in sex, maturity, etc. -- Record data from shipboard net mensuration gear to evaluate
trawl performance - Use a portable x-ray system (Appendices 5 and 6) to take radiographic
images of fish swimbladders - Optically verify the presence of non-hake scatterers
during trawling using a video camera and light(s) attached to the upper panel of the
midwater trawl approximately 20-30 meters forward of the codend. - Conduct vertical
casts with the ship?s CTD rosette, outfitted with a dissolved oxygen sensor and Niskin
bottles, at pre-planned stations along transects and/or at trawl locations (Appendix
2, Table 2, Table 4, and Table 5). These data will be used to describe the vertical
and horizontal distributions of hake relative to oceanographic conditions. Niskin
water collections will be filtered for evaluation of environmental DNA (eDNA). - Conduct
underway CTD (uCTD) casts at pre-planned stations along transects (Appendix 2, Table
6). These data will be used to supplement oceanographic information obtained from
the CTD rosettes and will be used to describe the distribution of hake relative to
ocean conditions - Continuously collect Acoustic Doppler Current Profiler (ADCP) data
along transects. These data will be used to describe the distribution of spawning
hake relative to currents. - Conduct vertical ring net zooplankton tows at pre-planned
stations along transects (Appendix 1, Figure 1; stations are listed in Appendix 2,
Table 2) and bongo net tows (Appendix 1, Figure 1; stations are listed in Appendix
2, Table 3). These data will be used to describe the winter distribution of zooplankton
species. - Continuously sample sea-surface temperature, salinity, and chlorophyll-a
using the ship?s thermosalinograph and fluorometer. These data will be used to estimate
the physical oceanographic habitats for spawning hake. - Continuously sample air temperature,
barometric pressure, and wind speed and direction using the ship?s integrated weather
station. - Collect broadband acoustic data with EK80 echosounders operating at central
frequencies of 70 and 200 kHz. The use of the EK80s will require temporary modification
to the ship?s EK60 set-up. |