What It's All About

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What do scientists know?

Striped bass are anadromous fish, meaning that they feed and live in salt water but move into fresh water to spawn. They are able to swim long distances along the coast, but may swim back to reproduce in good spawning grounds. During these migrations, striped bass are sometimes caught by fishermen in any one of a wide range of US states and Canadian provinces along the Atlantic Coast. There may be no rules for the migration patterns of striped bass in a river system. Some striped bass may migrate regularly while others from the same river never do. Scientific studies conducted since the 1930’s showed that adult striped bass migrate separately from juvenile striped bass. They take different routes and migrate at different times of the year. In those previous studies, scientists tagged fish with numbered markers to learn about their behavior and movement.

Some surprising findings from previous tracking projects:

1. Fish from the Hudson River were shown to move north in summer months and back to New York in fall months

2. One striped bass tagged in North Carolina was caught in Rhode Island, and another in Maine!

3. Fish from far north (Maine and Nova Scotia) or far south (Florida) may remain in rivers their whole lives, even though no dams block their access to the ocean. Staying in rivers may protect these fish from the ocean's cold winter temperatures in the north or hot summer temperatures in the south

4. Striped bass spawning populations in the Delaware Bay and Hudson River have recovered in part due to pollution clean-up. Pollution caused dissolved oxygen levels to fall so low between feeding and spawning areas that striped bass could not swim through them.

What do scientists want to find out?

When a striped bass is tagged with an acoustic   transmitter, it is possible for scientists to track the fish's movement in great detail. This technology can help scientists to better understand striped bass' population structure by determining how groups are separated by their movements. Questions scientists are looking to answer include: Have migration patterns changed over the years? How far do individual striped bass regularly travel? To where do they travel? Do they always return to the same estuary, or do they spawn in different estuaries in different years? It is now possible to answer these questions and more with acoustic tagging telemetry, and to better test some patterns discovered from the marker tagging.

Rutgers Scientists are interested in answering the last of these questions first. There is reason to believe that not all striped bass have the same migration patterns. It is possible that different contingents (groups) of striped bass migrate in different patterns, or maybe even not at all. This is important because, if so, it means that different groups of striped bass in a given area do not all spend the same amount of time in that area, and therefore do not provide equal contributions to the future generations in that area. It also means that the total number of fish must be calculated differently. Further, combining information about migration differences with information about the environment in a habitat can help answer questions as to what is important to a striped bass in coming to a “decision” regarding its particular migration. The old way of tagging cannot answer all of these questions, because, without the acoustic telemetry, there is no way of knowing where the fish spent the time between marking and recapture. Before, when a scientist caught a tagged fish in the same river where he or she had released it, it might have been assumed that that fish had traveled away during the year and then returned to that river to spawn. In fact, it's possible that the striped bass had never actually gone anywhere at all! The only way to know for sure is to track the fish's movement over an extended period of time with the acoustic telemetry. Hopefully, scientists will be able to extend their monitoring into the ocean in coming years to address the more complicated questions of routes and destinations for fish that do migrate. What they learn in the estuary now will help make these future studies possible.

By keeping track of striped bass' migration patterns, scientists can gain a much deeper understanding of the striped bass as a species, and fisheries managers can use the scientists' findings to help keep all striped bass populations at healthy levels.

The goals of this project are:

1. To provide a better understanding of striped bass population size and structure

2. To test acoustic tagging and listening methods for use on a bigger scale (along the whole US East Coast, and for more species)

3. To identify essential fish habitat for striped bass

4. To learn more about the use of coastal migration routes by striped bass from various populations

What are the future plans for this project?

Scientists plan to eventually expand the tagging program to include other coastal migrants such as bluefish (Pomatomus saltatrix), Atlantic sturgeon (Acipenser oxyrhyncus), and summer flounder (Paralichthys dentatus). Bluefish are abundant in recreational fisheries and, like striped bass, they vary greatly in number. Atlantic sturgeon are large anadromous fish that are being re-introduced to the Chesapeake Bay in Maryland and Virginia, where they used to live naturally. Acoustic tagging could help scientists know if introduced sturgeon stay and survive. Summer flounder (also called fluke) are another fishery mainstay especially because they are easily caught near the shore and in bays in the summer. They move to the continental shelf to spawn in winter, but more specific details about their migration are not well known.

As the telemetry methods improve, scientists involved in this project plan to include more hydrophones, to cover longer stretches of the coast and entrances to other bays. They also hope that other research groups will start their own tagging projects; then scientists all over will be able to share data about fish leaving one study area and entering another. This type of sharing would lead to coast-wide coverage of a species range, which is one of the goals of the Sloan Foundation, a group dedicated to accurately counting all of the world's marine life through the Census of Marine Life Project (CoML).