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Marine Fisheries Research - Fisheries independent estimates of fish populations

 

Fisheries independent data

Data collected by researchers is known as fisheries independent data because it was collected independent of a fishery. Fisheries independent data can be used on its own to help us better understand a species or can be combined with other types of data to conduct a population assessment or a fish stock assessment. Combining data from different sources is important and helps us increase the certainty we have in the population assessment and the management decisions that result from the assessment. Currently, few fish stocks on the West Coast have sufficient data to conduct a full assessment. One of the duties tasked to ODFW's Marine Fisheries Research Team is to create fishery independent data to improve the stock assessment process for species of concern and promote sustainable management. Learn more about stock assessments at NOAA Fisheries.

 

Using video and hydroacoustic tools to provide fisheries independent estimates of fish populations

Pilot research of combined video and hydroacoustic tools

Our team has developed a nearshore fishery-independent survey specifically for semi-pelagic rockfish species that live above the seafloor, such as black rockfish, deacon rockfish, and blue rockfish. Four years of pilot studies provided detailed data that lead to the selection of the optimal combination of visual survey tools and hydroacoustic data collection for quantifying fish abundance and biomass for rockfish species that are critical to Oregon's coastal communities.

video analysis
Image of video analysis where fish seen in the drop camera are counted and measured using a specialized video analysis tool, and an acoustic readout in Echoview program. Colored lines represent strength of signal feedback. The seafloor can be seen in red and green, while fish schools typically appear as blue blobs just above the bottom. - Click images to enlarge-

 

There were two specific objectives during our pilot project

Objective 1: Assess the effectiveness of paired acoustic and pelagic drop-camera surveys for documenting semi-pelagic rockfish density and biomass.

Species identification of fish from acoustics is currently not possible for mixed schools of morphologically-similar rockfish species (species with the same body shape). Therefore, our primary challenge for an acoustic-based rocky reef survey was identifying the species composition and size distribution within schools. Using a suspended pelagic stereo drop-camera to help identify fish to species was a high priority goal. Acquiring drop-camera footage from as many different schools as possible, containing a diversity of species compositions and size distributions, provided information on the range of school structures, and allowed us to determine the amount of sampling effort needed for future large-scale surveys.

In 2018, several single day cruises were conducted at different reefs to assess the validity of combining our suspended camera system with the acoustic data to generate population estimates. Analyses determined this combination of tools is ideally suited for this project. Read more about the results of this study in the Combined video-hydroacoutsic survey of nearshore semi-pelagic rockfish in untrawlable habitats publication.

ROV on left with the pelagic drop camera system (i.e. BASSCAM) on right.

Objective 2: Assess the impact of the near-bottom non-target species on the acoustic-based abundance estimates of target species, and assess the abundance estimate impacts from fish occurring in the acoustic blind-spot a.k.a "dead zone" (the area directly above the seafloor where the acoustic tool cannot see fish).

Because our goal for this toolset is to create a fishery independent dataset for stock assessments, there were two remaining unknowns we needed to address:

  • The extent that the acoustic tool picks up non-target species that are not in view of the camera.
  • The proportion of the population that exists in the acoustics blind-spot.

ODFW Marine Resources Program has a Remotely Operated Vehicle (ROV) that is capable of capturing species composition and length distributions of benthic fish, including those within, or near, the acoustic dead zone. Evaluating ROV data in concert with the acoustic and pelagic drop-camera combination provided a more complete picture of all species present and allowed us to quantify the importance of the area directly above the seafloor to the overall abundance estimate. We surveyed multiple reefs (Bandon, Redfish Rocks, Arago, and Orford reefs) with all three sampling tools and compared densities of near-bottom fish between the ROV and drop-camera/acoustic combination. We found that non-target species did not significantly contaminate the acoustic data and the proportion of target species within the blind-spot was significant but correctable. Read more about the results of this study in the Influence of near bottom fish distribution on the efficacy of a combined hydroacoustic video survey publication.

Applying above research to the first statewide survey of black rockfish using video and hydroacoustic tools

In 2021 we set out from the Oregon/Washington border on August 1, collecting acoustic data, video drops, and hook-and-line fishing samples as we zig-zagged along transects, gradually making our way south. By October 9, we had completed data collection along the entire Oregon coast, which consisted of 4570 km (2840 miles) of acoustic transects, 55 fishing stations, 578 underwater video camera drops, and 281 CTD casts!

Read more about how we did this survey and see photos, videos, results, and more on our Story Map.

In 2022, the data collected on this survey was reviewed by the Scientific and Statistical Committee of the Pacific Fishery Management Council and determined to be an important contribution to the 2024 stock assessment for black rockfish.

An example of a map used on the statewide survey. Data was collected on the transects running east to west (shown in black and pink). Transects were spaced every 15 km over hard substrate. - Click image to enlarge-

 

Using Landers to collect fisheries independent data

There is also a need for fisheries independent data of demersal fish (fish that live on or near the seafloor). Remote underwater vehicles (i.e., landers) have are a common tool and have provided stock assessment data to several regional fisheries management councils across the U.S.

ODFW's video lander platform is equipped with two stereo video cameras that allow us to observe, count, and measure fish in the ocean. Our team has designed and worked with stereo video landers with the goal of using them to conduct fisheries independent surveys of Oregon's demersal rockfish communities.

ODFW has experimented with many modifications to the lander systems over the years. Visit our publications page and type "Lander" into the search bar or read a summary of the first 9 years of lander data collection at ODFW in the Nine Years of Video Landers at the Oregon Department of Fish and Wildlife's Marine Resources Program, Information Report 2020-01 publication.

Video lander leaving Depoe Bay Video lander being deployed to collect video
Video landers leaving Depoe Bay, OR and being deployed to collect video

 

Baited Lander Video

 

Using Jigging Machines to collect fisheries independent data

Jigging machines are a fishing tool used in many fisheries around the world. Our team is interested in utilizing this tool as a cost-effective way to increase the number of hooks in the water while we conduct fishery independent hook-and-line sampling. Testing is currently under way to see how these machines do in the shallow and rocky reefs of the Oregon coast, and if they can compare to a human angler.

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