Return to the Northern Channel Islands to Monitor Change Over Time, Inside and Outside of Marine Protected Areas
- Dirk Rosen
Marine Applied Research and Exploration
- Andy Lauermann
Marine Applied Research and Exploration
End Date: December 01, 2016
The Channel Islands network of Marine Protected Areas (MPAs) provides a unique opportunity to understand how California’s nearshore marine ecosystems respond when areas are protected from human take. Established in 2003, this network offers not only the longest span of protection, but also has the state’s largest running time series of deep water data collected specific to MPA monitoring. Marine Applied Research and Exploration (MARE) returned to survey the northern Channel Islands MPAs 5 years after creating its deepwater baseline. MARE has performed over 600 kilometers of ROV video transects (approximately 1.8 million square meters of ocean floor) in the northern Channel Islands since 2003. The same 10 historical sites, both inside and outside of select MPAs, have been filmed and post-processed annually 2005-2009, with return surveys completed in 2014 and 2015. This information will be used to determine the change over time from MPA inception, and assess current condition and effectiveness at the state’s oldest network of MPAs. This immense baseline data set provides the foundation from which the state’s first MPA network can be evaluated.
Summary to DateFish abundance, for species of commercial and recreational take remained surprisingly consistent for survey years 2005-2009 at 10 sites inside and outside MPAs. 2014 ROV survey data will be compared with the 2003-2009 baseline data in March 2016. 2015 ROV field data will be statistically compared in late 2016/early 2017 with baseline and 2015 data. Results will be available shortly after that time.
Historical Survey Sites: State Marine Reserves and State Marine Conservation Areas of the Northern Channel Islands ranging from San Miguel Island to Anacapa Island – Area. Study sites include the following MPAs and adjacent outside reference areas: Harris Point SMR and Castle Rock, South Point SMR and Cluster Point, Carrington Point SMR and Rodes Reef, Gull Island SMR and East Point, and Anacapa Island SMR and SMCA.
- Habitat association
- Substrate characterization
Study MethodsData collection Protocols:
Two ROVs were used over the time period, both of which employed the same cameras. The Deep Ocean Engineering Phantom HD2+2 “ROV Bob” was used 2003-2009. The Deep Ocean Engineering M4 “ROV Beagle” was calibrated with ROV Bob in 2009 and deployed in 2014 and 2015. The ROV that will be used during this survey is the Deep Ocean Engineering M4 named “ROV Beagle”. The Beagle is a newer more sophisticated model, rated to a depth of 1,000 meters and equipped with additional cameras: high definition forward camera, stereo sizing cameras (2) and a digital still camera and strobe, and a BlueView 900kMz multibeam sonar. Beagle has a three-axis autopilot: heading, depth or altitude and constant speed to assist the pilot in maintaining a consistent forward velocity. A pair of Tritech® 500 kHz ranging sonars, which measure distance across a range of 0.1–10 m using a 6° conical transducer, are used as the primary method for measuring transect width.
The Beagle ROV is equipped with two color cameras, one facing forward and set at the desired angle below the horizon (as determined by the CDFW lead biologist) and the other pointing downwards. Video for both cameras was captured on SONY® DSR 45 digital video tape recorders and Pioneer DVR510 digital video disc recorders. In addition to capturing biological and habitat observations, the forward video is overlaid with an on screen display of text characters representing real time sensor data (time, depth, heading, temperature, range, altitude, forward camera angle, ROV pitch and roll). In addition to the primary cameras described, a locally recorded set of stereo cameras was used for highly accurate measurements of organism size.
ROV Beagle employs an ORE Offshore Trackpoint III® ultra-short baseline acoustic positioning system with ORE Offshore Motion Reference Unit (MRU) pitch and roll to reference the ROV position relative to the ship’s Wide Area Augmentation System Global Positioning System (WAAS GPS). The ship’s heading is determined using a KVH magnetic compass. A Trackpoint III® positioning system calculates the XY position of the ROV relative to the ship at approximately a two-second interval. The ship-relative position is corrected to real world position and recorded in meters as X and Y position using the World Geodetic System (WGS) 1984 Universal Transverse Mercator (UTM) coordinate system using HYPACK® 2014 hydrographic survey and navigation software. Measurements of ROV heading, depth, water temperature, camera tilt and sonar distance, both forward and downward to the substrate, are averaged over a one-second period and recorded along with the position data. GPS was used to provide a basis for relating position, field data and video observations. A Horita® GPS3 and WG-50 was used to generate on screen displays of GPS time, as well as output Society of Motion Picture and Television Engineers (SMPTE) linear time-code (LTC) for capture on SONY® DSR audio tracks at an interval of 1/30th of a second. ROV tracked position and sensor data were recorded directly by HYPACK® as a time-linked text file. A redundant one-second time code file of sensor data was also collected in the field using an onscreen display and operating system software with time code extracted from the system’s internal clock, which will be synced to GPS time.
All data collected by the ROV, along with subsequent observations extracted during post-processing of the video, are linked in a Microsoft Access® database using GPS time. Data management software is used to expand all data records to one second of Greenwich Mean Time (GMT) time code. During video post-processing, a Horita® Time Code Wedge (model number TCW50) was used in conjunction with a computer to record the audio time code in a Microsoft Access® database.
ROV Sampling Operations: ROV operations were conducted off the R/V Shearwater between the hours of 0700 and 1800 PST to avoid the low light conditions of dawn and dusk that might affect species abundance measurements and underwater visibility. The ROV was flown off the vessel’s stern side using a “live boat” technique that employs a 227 kg (600 lb) clump weight. Using this method, all but 45 m of the ROV umbilical will be secured from current-induced drag by coupling it with the clump weight cable and suspending the clump weight at least 10 m off the seafloor. The 45 m tether provides the ROV pilot sufficient maneuverability to maintain a constant speed (0.5 to 0.75 m/sec) and a straight course down the planned survey line. In addition, the ROV pilot and ship’s helm used real-time video displays of the location of the ship and the ROV relative to the planned survey line, to navigate along the line without deviating from the planned path by more than 10 meters. The ship’s captain used the displays to follow and maintain the position of the ship within 35 m of the ROV.
At each site, the ROV was flown along pre-planned survey lines. The ROV pilot maintained a forward direction within ± 10 m of the planned line. The ranging sonars were fixed below and parallel to the primary forward camera between two forward-facing red lasers spaced 100 mm apart. The ROV pilot used the sonar readings to sustain a consistent transect width by maintaining the distance from the camera to the substrate (at the screen horizontal mid-point) between 1.5 and 3 m.
Site and Survey Line Selection:
The boundaries of the ten sites (five site pairs) sampled were made permanent in 2005 (Figure 1) and were selected based on exploratory surveys conducted during the 2003 through 2005 survey years. Site pairs consist of a site within an SMR along with a site in a nearby fished reference area. Four of the five reference sites are unrestricted areas that are open to all types of fishing. The fifth reference site (AI-1) is located within the boundaries of Anacapa Island State Marine Conservation Area, which only allows recreational take of lobster and pelagic finfish and commercial take of lobster. The study sites were selected as 500-m wide rectangles that varied in length from 1.2 km to 3.5 km moving offshore, with depths ranging from 20 m to 80 m. Prior to field sampling, 500-m long track lines were chosen within each site (Table 1; Figures 2-11). Areas determined to be mostly sand, based on multibeam or sidescan sonar, were excluded from the line selection process. To ensure that the sampling was distributed across the entire depth range each site was divided into one to four zones. The total number of track lines selected within each zone was dependent on the zone’s area and the anticipated proportion of hard habitat. An additional 10% buffer was added to the target goal to allow for sampling errors, such as the ROV missing part of a planned track line or being pulled off the planned line by the topside vessel.