DOI: 10.24431/rw1k5bd
title: Remote sensing razor clam abundance data from western Cook Inlet, Alaska, June 22 to June 27, 2017

description: These datasets are part of the development of remote sensing methods for estimating razor clam abundance in western Cook Inlet. The data are broken down into three objectives. Objective 1: Hydraulic sampling. We sampled with hydraulic pumps at 9 sites on the south side of the Crescent river bar during minus-tide series June 22-27, 2017. At each site, a hydraulic pump was used to extract razor calms from the substrate at 25-136 quadrats (0.5m-square) spaced 1-2 m apart. These data are in two space delimited files. Lengths.prn has date (mdd), time (am or pm) loct (location) FSLM (razor calm length in mm) and age. Counts.prn has date (mdd), Time (am, pm), Tide (in feet) LOCT (location and quadrant), LTDG (latitude degrees), LTMN (latitude minutes and seconds), LGDG (longitude degrees), LGMN (longitude minutes and seconds), RCNT (razor clam count), BCNT (butter clam count), LCNT (littleneck clam count) and NCNT (neptunia clam count). Objective 2: Multi-beam sonar data was collected along equidistant parallel transects in tow survey area on the Crescent river bar on June 24 (1620-1730 hours), June 26 (1930-2100 hours) and June 27 (0540-0710). Transducers for both systems were pole mounted on an 10-m aluminum vessel and transcets surveyed at 2 m/sec. The MBES was mounted on the port side and the SBES was mounted on the starboard. The two systems were not operated at the same time due to "cross talk" between them. The MBES system consisted of a Kongsberg GeoSwath Plus Compact Shallow Water Multi-beam sonar (250 kHz) which collected sediment data over a 20-m swathe of seafloor on each side of vessel. The MBES was equipped with a sound velocity sensor (mini-SVS) and a Kongsberg MRU-H motion reference unit for system calibration. A patch test was conducted approximately 2 km southwest of the survey area that provided distinct bathymetric features for calibration of any navigation latency and angular offsets. To provide for accurate estimation of bathymetry, local water level changes were mesausred using a HOBO (Model U20) pressure sensor (accuracy +- 1.5 cm). Post-processing of MBES was conducted using Kongsberg GeoAcoustics GS4 software. Objective 3: Sub-bottom profiling sonar. SBES acoustic date were also collected along equidistant (40-50m) parallel transectsin two survey areas on the south side of the Crescent River Bar on June 24 (1620-1730 hrs), June 26 (1930-2100 hrs) and June 27 (0540-0710 hrs). The SBES system consisted of an Innomar SES-2000 Compact Sub-bottom Profiler with a low frequency echosounder (15kHz) to collect acoustic data below the seafloor and a high frequency echosounder (100kHz) to measure depth of seafloor. The system had no side lobes on acoustic beam reducing spurious signals. It provided high spacial resolution (1-5 cm) for detection of small objects buried in the sediments due to narrow (4 degree) acoustic beam, short pulse width (0.07-1 ms), high ping rate (up to 40/sec) and high bandwidth (2-22 kHz). The SBES was also equipped with a sound velocity sensor and heading pitch and roll sensors. Both acoustic systems received precision position data from Hemishpere Vecto VS330 GNSS Compass differential global positioning system.