Atlantic Sea Scallop Dredge Survey

Two scientists wearing foul weather gear sort palm-sized sea scallops into baskets and count the total number of baskets. — Caption: A large catch of young Atlantic sea scallops collected during the 2025 survey is sorted into baskets and counted aboard the F/V Selje. Credit: NOAA Fisheries/Dana Morton

What We Survey

The first standardized scallop dredge survey in our region sailed in 1975, and it has occurred annually since 1977. Today, we conduct the Atlantic Sea Scallop Dredge Survey in the Northwest Atlantic Ocean from New England to the Mid-Atlantic. We survey Georges Bank off the coast of New England south to the Delmarva Peninsula off the Mid-Atlantic coast.

In recent years, we have focused on Georges Bank, while our Research Set-Aside Program partners conduct dredge surveys in the Mid-Atlantic.

We collect data on Atlantic sea scallop:

Abundance
Spatial distribution
Disease
Life history
Predators (sea stars, whelks, crabs)

Atlantic sea scallops are distributed from Newfoundland, Canada to Cape Hatteras, North Carolina. They live on sandy or gravelly ocean floor habitats and are most often found at depths between 100 and 300 feet. They can live up to 20 years.

A scientist holds a hand-sized sea scallop over a measuring board. — An adult Atlantic sea scallop collected during the survey. Credit: NOAA Fisheries/Charles Keith

Atlantic sea scallops support a high-value commercial fishery that is usually one of the most lucrative in the region. There is no recreational fishing allowed for this species. In 2024, commercial landings of Atlantic sea scallop totaled 21.3 million pounds and were valued at $333.2 million, according to the NOAA Fisheries commercial fishing landings database.

Why We Survey

The U.S. sea scallop fishery is important to the U.S. economy and is the largest wild scallop fishery in the world. The Magnuson–Stevens Act fosters the long-term biological and economic sustainability of marine fisheries, including the scallop fishery. Under this act, we help:

Better understand fishery patterns
Monitor and predict how ocean conditions may impact and shift fish distribution
Provide data for stock assessments to help prevent overfishing and to rebuild overfished stocks
Advise fishery management
Increase long-term economic and social benefits derived from fishing
Ensure a safe and sustainable supply of seafood
Protect habitat that fishery species need to spawn, breed, feed, and grow to maturity

How We Survey

This long-term fisheries-independent survey uses standardized sampling methods to collect critical data. In recent years, we have collaborated with the scallop industry by using a commercial fishing vessel as the survey platform.

Dredge Vessel History

Over the survey’s history, we have used a series of vessels to conduct the Atlantic Sea Scallop Dredge Survey based on survey needs and equipment:

1977 to 2007: NOAA Ship Albatross IV
2008 to 2023: R/V Hugh R. Sharp, a research vessel owned and operated by the University of Delaware
2024 to present: F/V Selje, a commercial scalloper

The F/V Selje, a 104-foot long New Bedford-style commercial scalloper, leaves the dock in Woods Hole, MA. — The F/V Selje, a New Bedford-based commercial scalloper that has been used for the Atlantic Sea Scallop Dredge Survey from 2024–present. Credit: NOAA Fisheries/Dana Morton

Dredge and HabCam Survey History

In 2012, we began using the Habitat Camera Survey (HabCam) alongside our traditional dredge survey to get more detailed information about scallop numbers and locations. Until 2023, we ran both surveys at the same time on the same vessel (the R/V Hugh R. Sharp). Starting in 2024, we separated HabCam and Dredge into two distinct surveys. This helps us better manage our operations and ensures that we can continue gathering data even if one survey platform faces mechanical issues.

Dredge Survey Design

We use a stratified random sampling design. That means the survey area is first divided into subareas called strata. Then, locations within each subarea are selected to be sampled with the dredge.

Dredge Sampling Design 1977–2024

Originally, our strata for this survey were based primarily on depth and secondarily on latitude. Locations of sampling stations were randomly selected within each stratum prior to each annual cruise.

Map of the Northwest Atlantic coast showing the shellfish strata. The strata span Georges Bank to Mid-Atlantic and largely follow bathymetry. — The NEFSC Shellfish Strata, highlighted in blue, were used as survey strata from 1977-2024. Each blue box is a stratum. Sampling stations within each stratum are randomly selected for sampling prior to each annual survey. The black line at upper right is the international boundary dividing the Gulf of Maine between the United States and Canada. Credit: NOAA Fisheries

Dredge Sampling Design 2025 to Present

Starting in 2025, we revised our method for selecting survey stations. This allowed more intensive sampling of high-priority areas and prevented randomly selected stations from being placed very close together. These changes have improved survey efficiency and make the resulting data more useful to management.

Map of the Northwest Atlantic coast showing the revised sea scallop survey area from the Mid-Atlantic to Georges Bank, which has many fewer strata. — Scallop Area Management Simulator area boundaries. Each green box is a “SAMS area”. These areas are used in scallop management, and as of 2025 are used to ensure that enough stations are sampled in areas that are high priority for management. Sampling stations are selected using a spatially balanced sampling approach known as a Generalized Random Tessellation Stratified sampling design. The black line at upper right is the international boundary dividing the Gulf of Maine between the United States and Canada. Credit: NOAA Fisheries

We use a balanced sampling method (Generalized Random Tessellation Stratified) to ensure we collect the most accurate data possible. We use the method to randomly select sampling stations. There are more stations placed in areas that likely have more scallops—based on models of scallop biomass and abundance developed at the center. This allows us to focus our efforts on areas with higher concentrations of scallops.

Dredge Sampling Operations

We use a standard 8-foot-wide dredge to collect sea scallops. The dredge includes a bag made of 2-inch metal rings and a 1.5-inch mesh liner, which helps us capture even smaller scallops. The dredge frame has roller wheels to move smoothly along the seafloor, and we add ”rock chains” when surveying rocky areas. We tow the dredge for 15 minutes at a speed of 3.8 knots, using a 3:1 ratio for the length of the tow cable relative to the depth to keep the dredge angle in the right position.

Scientists in foul weather gear begin to sort a large pile of larger sea scallops into plastic baskets. — Scientists and crew prepare to sort a dredge haul of large sea scallops on the back deck of the F/V Selje. Credit: NOAA Fisheries/Zachary Fyke

Gear Performance

Dredge performance is monitored using a StarOddi Starmon sensor, which measures depth, temperature, and tilt along three axes every second. The tilt measurements are used to determine dredge angle and bottom contact. Following each tow, scientists on board examine the sensor data to ensure good bottom contact for the duration of the tow. Problems with a tow are indicated in the database, and stations are re-towed if problems are severe, such as a dredge flip.

Data Collection

Once a dredge tow is complete, the catch is dropped on the deck. We sort all scallops (Atlantic sea scallop, Icelandic scallop, and Calico scallop), scallop clappers (recently dead scallops), American lobsters, and fish from the catch into baskets. Scallop predators (waved whelks, moon snails, rock crabs, and sea stars) are either sorted from the whole pile or from a smaller subsample.

Because we use a lined dredge, the dredge also collects substrate and non-target species. Once all target species are removed, we measure the total volume of this bycatch by shoveling it into baskets. Then we estimate the proportions of each part of the bycatch by examining a subsample. For example, bycatch might have 75 percent sand dollars and 25 percent sand. This information helps describe the habitats where scallops live and reproduce.

We then begin data collection for species abundance, biomass, growth, and disease. We use an Integrated Fisheries Scientific Computer System to record data and inform us when additional biological samples and condition assessments are needed. This system uses motion-compensated digital scales, electronic measuring boards, and touch screen displays to record and archive the data on the computer network.

Lengths and Weights

Each basket of organisms is weighed and entered into the Integrated Fisheries Scientific Computer System. Using the system, we measure and record shell height for each scallop in the catch (or subsample). We measure some fish species that are of special importance to fisheries management, including cod, haddock, skates, and monkfish. We count other fish, lobsters, and scallop predators (see above).

Three scientists at work bench measuring scallops on electronic measuring boards. — Scientific staff measure scallop shell height using electronic measuring boards. The data is automatically recorded by the Fisheries Scientific Computing System. Credit: NOAA Fisheries/Charles Keith

Scallop Growth, Condition, and Disease

For each survey station, we examine an additional sample of scallops in more detail (1 to 6 individuals, >70 mm shell height). We record more detailed size parameters, meat weight, sex, gonad weight, and disease presence. Then, we shuck the scallop, weigh the meat and gonad individually, and document any diseases with photos.

One half of a scallop shell with the adductor muscle still attached. The shell appears to have shell blisters, so a label is placed on the shell and a scallop knife indicates the diseased area. — Scallops showing signs of disease are photographed. This scallop had signs of shell blister disease, so the shell was photographed with a label and scallop knife indicating the diseased area. The label with the barcode connects the sample with the entry in the computer system. Credit: NOAA Fisheries

The sampled shells are individually labeled, cleaned, and brought back to the science center to determine growth rates.

A stack of clean scallop shells in a cloth bag. — Cleaned and labeled scallop shells are placed in cloth bags and brought to the Northeast Fisheries Science Center for growth measurements. A label with a barcode connects each shell with the scallop’s entry in the computer system. Credit: NOAA Fisheries/ Dana Morton

Scallop growth is dependent on multiple environmental factors, and each year stock assessment scientists update their models with growth rates specific to different areas and depths. Each time a scallop spawns, it creates a ring on the shell. Because scallops spawn annually once they reach maturity, these rings serve as annual growth rings for adult scallops. To determine growth rates, scientists mark these annual growth rings on the shell. We measure the length from the umbo (the oldest part of the shell) to each marked ring. The difference from one ring measurement to the next represents 1 year's growth for that scallop. Using this method, stock assessment scientists estimate average scallop growth rates by area, depth, and year.

A clean scallop shell with visible concentric growth rings, with varying distances between them. Each ring is marked in blue. — Cleaned scallop shell prepared for growth measurements. The annual growth rings are marked in blue. The distance between rings indicates how much the scallop grew in that year (a larger distance between rings means more growth that year). Credit: NOAA Fisheries/ Sandy Sutherland

Sample Requests

We often receive sample requests from collaborators, partners, and/or other research scientists, which we fulfill when possible. To submit a sample request through our online form.

How We Use the Data

The data we collect during this survey—and our optical surveys like HabCam—provide scientifically rigorous information and are used in a variety of ways. They inform:

Stock assessments
Commercial fishing catch limits
Scallop management area boundaries and rotational closures
Scallop Research Track Working Group recommendations
Scientific research and publications
Public reports

Access Our Data

Our dredge survey data are available through NOAA Fisheries InPort Library and by request. To request data, please contact Dana Morton or Jakub Kircun. We also make a resource survey report and cruise results document available after each survey is complete.

Survey Summaries

Next Generation Survey

Marine development may disrupt survey sampling, as dredging is not possible near offshore infrastructure such as buried cables or scour protection. Developing advanced technology, such as autonomous vehicles, is a key element of future survey resiliency. Learn more about ongoing development of advanced technology surveys.