Photos by Tom Lynch
How innovative techniques are expanding ocean fisheries data collection
Ocean science has come a long way since American naturalist William Beebe’s legendary 1934 descent to a depth of over 3,000 feet off Bermuda in a steel, spherical ‘diving bell’. Two decades later, more sophisticated manned submersibles came on the scene to explore the oceans with the launch of the Trieste in 1953, followed by Woods Hole’s Alvin in 1964 and Harbor Branch’s Johnson Sea Link in 1971.
By the 1990’s, the capabilities of manned subs were being combined with remotely operated vehicles (ROVs) and autonomous underwater vehicles (AUVs) allowing scientists to study areas too deep or too dangerous for manned exploration. More recently, ocean gliders have emerged as another tool for collecting ocean data.
Gliders For Monitoring
Essentially cigar or torpedo shaped cylinders, ocean gliders are unmanned underwater vehicles that scientists can equip with a variety of sensors allowing them to monitor water temperature, salinity, currents, and other ocean conditions. Gliders propel themselves by changing buoyancy and using wing-like hydrofoils to move both vertically and horizontally while profiling the water column and can be programmed to travel long distances, access remote locations, and safely operate over long periods of time without needing re-calibration or maintenance.
The Rutgers University Center for Ocean Observing Leadership (RUCOOL, rucool.marine.rutgers.edu) deployed the first glider off the New Jersey coast in 1998. Since then, Rutgers has deployed gliders over 500 times to monitor the ocean off New Jersey and around the world. RUCOOL is using gliders to monitor coastal water quality and ocean conditions to better understand factors related to coastal upwelling, oxygen depletion, ocean acidification, and tropical storm intensification.
Data from glider deployments are also being used by researchers affiliated with RUCOOL to better understand water quality and ocean conditions that affect the distribution and abundance of important marine species, including fish. Modern gliders can also be used as an acoustic monitoring platform by rigging them with sensors that enable them to be programmed to actively follow a fish carrying an acoustic tag.
Biotelemetry Fish Tracking
While it’s uncertain when fish were first marked as a method to study their movements, Isaak Walton’s 1653 The Complete Angler reported that private land owners in Scotland had tied ribbons to the tails of juvenile Atlantic salmon to determine what happened to them in the streams that they owned. In the United States, the earliest successful tagging effort is believed to have taken place in 1873 when fisheries biologist Charles Atkins tagged Atlantic salmon in the Penobscot River in Maine.
Over the years, scientists have used a variety of tags to mark, track, and monitor a diversity of recreationally and commercially important fish. Although data from early tagging efforts were often limited, more recent tagging studies have yielded information about the life histories of many species such as where they travel, how fast they grow, and how they use various habitats.
Advancement in technology in the mid-twentieth century saw the emergence of acoustic telemetry as a tagging technique. The use of acoustic telemetry was first employed in the 1950s and 1960s. Early applications included monitoring adult Pacific salmon populations at the Bonneville Dam in Oregon and Chinook salmon in the Sacramento-San Joaquin Delta in California. Since then, acoustic telemetry has continued to emerge as a powerful tool enabling a better understanding of coastal fish movements, migration patterns, and habitat use.
Basically, here’s how it works – acoustic telemetry uses sound (acoustics) to relay information across open space (telemetry). For fisheries research, an acoustic telemetry system consists of two main pieces of equipment, transmitters and receivers. Transmitters are electronic tags that are typically surgically implanted in fish. Each transmitter emits a unique series of sound pulses (pings) that is heard by underwater receivers making it possible to identify individual fish. Receivers are data-logging listening devices that detect the sound signal of tagged fish. The receiver decodes the unique signal of a transmitter and logs the transmitter number, date, and time of detection. By deploying a network or array of receivers “in the field,” scientists can compile data that allows them to track a fish’s movement as well as show the amount of time a fish spends in a particular area.
The power of acoustic telemetry studies is exemplified by research recently conducted in the Bahamas which has led to a better understanding of the movement patterns and life history of bonefish including when and where spawning activity occurs. It turns out that bonefish move from tidal creeks and coastal flats environments to aggregate at sites in close proximity to deep water drop offs, subsequently moving to deep water during certain moon phases for spawning. After spawning they return to shallow flats environments shortly after new and full moons.
As noted by Dr. Aaron Adams, Director of Science and Conservation at the Bonefish and Tarpon Trust, now that we know the conditions bonefish require to spawn, we can better focus our efforts for habitat conservation.
Striped Bass Research
Closer to home, acoustic telemetry studies have yielded new information over the past several decades about a variety of aspects of striped bass life history including new insights into their migratory behavior. For instance, telemetry studies have confirmed that in both the Hudson and Chesapeake there are stripers that remain in spawning rivers or adjacent estuarine habitats year-round, so-called resident contingents, as well as a migratory contingent that undertakes a coastal migration after spawning.
The use of biotelemetry has also led to a more complete picture of migratory behavior of stripers when they leave their spawning and overwintering areas in spring and move northward to feed off the northeastern United States and southeastern Canadian coasts in summer, then return south in fall to overwinter. For example, it turns out that some stripers stop in various estuaries briefly on the migrations north and south without staying long in any one location, while others may stay for extended time in a single estuary with favorable environmental conditions.
In addition, acoustic telemetry has yielded information on homing patterns of individual striped bass and how they use specific portions of New England estuaries in summer. As a result, we now know that stripers from multiple overwintering areas congregate in common feeding areas in the Northeast. Recent telemetry studies have also confirmed the tendency of some individuals to return to the same feeding areas across years and may remain there for extended periods of time while others wander between foraging areas. Acoustic telemetry data has also shown that individual striped bass moving south from the same summer feeding areas in fall often take different routes when returning to overwintering locations.
In 2009, we began acoustically tagging striped bass in Sandy Hook Bay and at Island Beach State Park in collaboration with the Berkeley Striper Club and other recreational fishing groups. To date, we have implanted three dozen stripers with tags thanks to their efforts and support. My colleague at Monmouth University, Dr. Keith Dunton, has recently ramped up our acoustic tagging efforts. The goal of these efforts is to yield more complete data on habitat use, movements, residency patterns, and relative abundance of a variety of commercially and recreationally valuable species including Atlantic sturgeon, striped bass, blackfish, black sea bass, summer flounder, and a variety of sharks within the New York Bight.
Dunton likes to equate acoustic tagging to an EZ Pass system for fish, allowing the precise tracking of movements of individual fish for up to 10 years and notes that the capability of this technique is made more powerful by the fact that researchers conducting telemetry tagging studies along the U.S. east coast are part of a collaborative network known as the Mid-Atlantic Acoustic Telemetry Observation System (MATOS, matos.asascience.com). The MATOS network currently consists of over 186 scientists from North Carolina to Maine as well as researchers from the Canadian Maritimes sharing data on tagged fishes.
Tracking Fish Through DNA
Historically, scientists have used visual observations and a variety of sampling techniques to catalog fish populations and document the status of fishery resources. However, the capture of fish through conventional methods can be costly, time consuming, and labor intensive. This is perhaps best illustrated in a 1999 bio of pioneering oceanographer Henry Bigelow that appeared in Harvard Magazine, where the author noted that in the two decades prior to helping establish the Woods Hole Oceanographic Institution in 1930. Bigelow sailed tens of thousands of miles and made tens of thousands of net hauls along northwestern Atlantic coastal waters to begin to document the distribution, abundance and life histories of important species.
Throughout the remainder of the 20th century, most fisheries studies continued to employ traditional sampling gear; however, over the past decade, an exciting new molecular biology approach has emerged that uses environmental DNA, or eDNA, as a tool that can detect the presence of fish species. Based on the principle that fish shed DNA-containing cells into the water from scales, skin, feces, and other tissue, scientists can collect water samples and isolate the DNA found in the sample to provide a snapshot of the fish present at the time of sampling as well as the community structure over time.
Basically, here’s how it works – after a water sample is collected and filtered, the DNA can be extracted, amplified, sequenced, and analyzed to detect individual species, enabling researchers to define fish community composition. It’s actually not incorrect to say that these scientists are doing ‘fish forensics’ by borrowing DNA approaches from crime scene investigators!
The application of this method has gone through proof of concept studies with both freshwater and marine fishes. For example, a recent study in New Jersey’s coastal waters led by Dr. Mark Stoeckle from Rockefeller University along with my colleagues at Monmouth, doctors Dunton and Jason Adolf, conducted in collaboration with the NJDEP Bureau of Marine Fisheries showed that fish diversity determined via eDNA was the same, or at times even higher, than trawl survey fish diversity.
A review of fisheries studies using eDNA published in 2021 noted that 90% of the studies evaluated by the authors demonstrated positive correlations between detectable DNA in the environment and abundance/biomass of the target species being studied. And, in June the National Science and Technology Council’s Subcommittee on Ocean Science and Technology issued the National Aquatic Environmental DNA Strategy acknowledging the power of eDNA and recommended government agencies incorporate this approach into future fisheries surveys.
Doctors Adolf, Dunton, and their colleagues are now using eDNA to better characterize fish community composition in offshore regions of the New York Bight as well as along beaches at select locations along the New Jersey coast. While the offshore work is being conducted by these researchers, the surf zone sampling is being accomplished in collaboration with members of the recreational fishing community including the Berkeley Striper Club, Manasquan River Fishing Club, and Tak Waterman.
“Characterizing ocean communities, including fish, is challenging,” Dr. Adolf said, adding “We need to be thinking of innovative and creative ways to use technologies such as eDNA to solve long-standing shortcomings of traditional sampling techniques.” Dr. Adolf added, “In the case of eDNA, we are not trying to replace traditional methods, but rather are looking to improve what we do and how we do it by introducing eDNA as an additional tool in the fisheries science toolbox.”
All of these applications greatly expand our knowledge and provide the data and information necessary to untangle the current, and potential future, impacts of increased use and development of the nearshore and shelf environment in the New York Bight region.
The author is retiring this fall as assistant dean of the School of Science at Monmouth University where he has specialized in marine ecology, coastal zone management, environmental science, marine recreational fisheries, and marine and environmental education. Since 2011, professor Tiedemann has managed a research and education campaign called Stripers for the Future in an effort to assist anglers in contributing to the conservation and long-term sustainability of the striped bass fishery. We at The Fisherman hope his retirement means more time to fish, and more time to for editorial contributions to the magazine.
