Methods for Image-based Surveys of Benthic Macroinvertebrates and Their Habitat Exemplified by the Drop Camera Survey for the Atlantic Sea Scallop

Underwater imaging has long been used in the field of marine ecology. By decreasing costs of high resolution cameras and data storage have made the approach more practical than in the past. Image based surveys allow for initial samples to be revisited and are non-invasive compared to traditional survey methods.

But protocols are driven by target species behavior and survey objectives. This method can help answer key ecological questions for species of interest, such as their abundance, distribution, and habitat associations. Demonstrating parts of the procedure aboard the fishing vessel, Liberty, is Craig Lego, a graduate student in our lab.

To set up the equipment on the vessel deck, arrange the pyramid as described in the text protocol. The pyramid is a pressure sensitive wrench with a fiber optic cable, which is on a drum, and attached to a slip ring. Attach the junction box to the pyramid.

Next, attach the cameras and lights to the pyramid, then connect the cameras and lights to the junction box with camera and light cables. Run the fiber optic cable through the sheave and attach it to the davit. Attach the vessel hydraulic wrench cable to the pyramid.

Set up the equipment in the vessel wheelhouse. To attach the deck end of the wheelhouse, run the fiber optic cable to the optical slip ring on the pressure sensitive wrench. After setting up the computers, as described in the text protocol, connect the cameras and lights to the vessel wheelhouse.

To attach the wheelhouse end of the wheelhouse, run the fiber optic cable into the wheelhouse and attach it to the fiber optic interface on the desktop computer and the light power plug. Launch the field data collection program from the desktop computer. Ensure that all cameras mounted on the pyramid and plugged into the junction box automatically show as connected.

To capture the images and record data at each station, launch the mobile field mapping program from the laptop computer, select the mark tool and drag the target icon onto a station to provide a bearing to the station. Slowly lower the sampling pyramid to the sea floor. Use the vessels hydraulic wrench when the station has been reached and the vessel has stopped.

While the pyramid is being lowered to the sea floor, double click the area short name box and enter a name for the area. Click the launch captain's cam"button to display the camera views and other information on the monitor near the hydraulic wrench controls. After switching on power to the lights, capture quadrat data once the sampling pyramid has landed on the sea floor.

In the field data collection program, click start station"to start the video recording. Click take snapshots"when a clear view of the sea floor appears, then click save all"to capture a still image from all camera views simultaneously. Then click the write to database"button.

Enter the number of scallops seen in the digital still camera image in the scallop count box and type any comments into the comments box. Click the write to database"button to write the data about the quadrat as a row in the field database. Lift the pyramid, as detailed in the text protocol, and click end station"in the field data collection program to end the video recording and advance the program to the next station.

Click the quit program"button to close the program. Finally, click capture station"in the mobile field mapping program to mark the station as before. After retrieving the images, as described in the text protocol, navigate to the substrate section and click the boxes for the substrate types that are present.

To quantify macrobenthic animals, click the boxes for the animals that are present in the inverts presents section. Enter the number of each animal observed in the inverts count section. Click the red SC"button and dot each scallop in the image.

Click the submit"button to write the data about the image as a row into the lab database and create a copy of the image with the animals dotted. Then change the profile in the lab data collection program to image check"Review the entry for accuracy and make any changes necessary. Select the submit"button to overwrite the data about the image submitted by the digitized user, then mark the image as quality controlled in the lab database.

To measure the scallops observed in the images, select line annotation in the image annotator program, then draw a line from the umbo of the scallop to the top of the scallop's shell. Repeat this step for all measurable scallops in the image. Select file"and then save annotations"to create a spreadsheet of measurements before performing data analysis as described in the text protocol.

Representative results of a fully annotated survey image are shown here. The annotator program counts every dot of each color, quantifying the number of these animals in the image. The lines on each scallop extend from the umbo to the front of the shell and are measured by the program to provide an estimate of the scallops shell height.

In the US Atlantic Sea Scallop Fishery, the scallop area management simulator model is used to project sea scallop abundance and landings. Each zone of this model on Georgia's bank was an area of interest. Once the scallops in each image have been counted and measured, density and size estimates are made for each area of interest.

In addition, distribution maps for each area are created for all scallops, juvenile scallops, and scallops of harvestable size. Using the estimates from the survey, as well as the scallops shell height to meat weight relationship, estimates of the total and exploitable scallop biomass for each scallop area management simulator model zone are produced. Included in the table are the mean scallop meat weight in grams, the total weight of scallops in metric tons, and the standard error in metric tons.

After its development, this technique paved the way for researchers in the field of fishery science to work collaboratively with the fishing industry to explore scallop abundance and distributions on the US continental shelf. After watching this video, you should have a good understanding of how to capture images at sea, quantify the data within these images, and create data products that support fisheries management. Following this procedure, data on substrate and other animals besides scallops are collected and can be used to answer additional questions like habitat preferences and predator prey relationships.

Don't forget that working at sea can be extremely hazardous and precautions such as safety at sea training and working with experienced crew should always be taken while performing this procedure.