Can we use fish morphology to reliably differentiate between resident Kennebec spawning striped bass and the migratory population?

Why this matters

Although the majority of stripers along the Maine coast are seasonal migrants from the Chesapeake Bay, there is a small population that spawns in the Kennebec River and stays in the Gulf of Maine. Learning more about each population of striped bass in Maine is essential to informed management of this fishery.

  • Gulf of Maine Research Institute



Managing striped bass, like any fish species, requires a good understanding of how many fish there are in an area and how those fish move around, reproduce, grow, and eat. Most, but not all striped bass in the Gulf of Maine are seasonal visitors, arriving with the start of summer weather. This migratory population spawns in the Mid Atlantic, swims 600 or more miles north to feed in the summer, and returns south in the fall. A second, much smaller population spawns in the Kennebec River and, we assume, undertakes shorter migrations throughout the year. There is some evidence that the stripers that migrate from the Mid Atlantic are more torpedo-shaped (longer and leaner) than the resident Kennebec fish. Right now, the only reliable way for scientists to tell whether an individual fish spawned in the Kennebec or Mid Atlantic is to perform chemical analysis of its otoliths, the tiny inner ear bones that grow as a fish ages, sort of like tree rings. The chemical signature of the center of this bone reflects the unique chemistry of the water where that fish began its life.

This project is designed to determine if careful measurements of striped bass morphology (shape) can be used in place of otolith analysis to distinguish between migratory and resident populations. To make this determination, scientists need lots of data. In particular, scientists need both the otoliths from harvested fish and pictures of those fish’s body shape. With information from both the otoliths and 27 measurements made to characterize the shape of the individual fish, scientists can determine if the shape of fish from the Mid Atlantic are reliably and significantly different from than their Kennebec cousins. If striper morphology proves as reliable as otolith analysis, we will have a powerful, non-lethal method to help monitor and steward the different populations of this important and popular fish.

More information on life cycle and populations

Striped bass, Morone saxatilis, are one of at least six species belonging to a family of ray-finned fish that include both freshwater and marine species. Striped bass are anadromous, meaning they spawn in freshwater but live most of their adult lives in the ocean. They can be found in a wide variety of habitats, from salt marshes and rivers to open beach and rocky shores. Generalist predators, their diet varies with their habitat and includes almost any other sea creature that can fit in their mouths, from small fish (especially mackerel, herring, silversides, and alewives in Maine) and squid to worms, invasive European green crabs, and even lobsters. As a testament to its popularity, striped bass is the state fish of seven east coast states between South Carolina to New Hampshire. The latest stock assessment in 2019 found that striped bass were overfished with overfishing occurring--this means that there are not as many breeding fish as their should be and we are also harvesting more of those that are left than we should be.

Striped bass have been intensely fished. Current populations have seen boom and bust cycles on a coast-wide scale, with some local populations wiped out entirely. Since an all-time low in the 1980s, striper numbers have grown but not stabilized (Atlantic States Marine Fishery Commission, 2017). Poor fishing in the early 2010s in the Northeast and Maine in particular inspired the Coastal Conservation Association of Maine to suggest a collaboration with the Gulf of Maine Research Institute to learn more about the striped bass in Maine in order to improve management of the species.

Please see our project Data Management Plan to learn more about our approach to helping participants provide useful data, ensuring data quality, and the methods we will use to analyze those data.

Project Owners


Zach Whitener

Gulf of Maine Research Institute

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Project Partners

Gulf of Maine Research Institute