Atlantic Sturgeon

NOAA Fisheries conducts or supports research on the biology, behavior, and ecology of the Atlantic sturgeon. This research informs management decisions and enhances recovery efforts for endangered and threatened Atlantic sturgeon populations.

Tagging and Tracking

Scientists are using tagging techniques to learn about the migration patterns of Atlantic sturgeon and identify important juvenile habitats. Dart, passive integrated transponder (PIT), radio, satellite, pop off, and acoustic tags are commonly used types of tags. Tags, such as PIT tags and dart tags, allow for an individual fish to be identified by other researchers when it is captured. Acoustic and satellite telemetry tags provide researchers with data on where Atlantic sturgeon migrate, at what depths, and at what speeds.

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Genetics

Researchers take small fin clips from sturgeon they catch to better understand the genetic composition of the populations. Tissue samples from sturgeon spawning (releasing or depositing eggs) in a particular river can be taken and analyzed to create baselines of the unique genotypes (the genetic makeup of an individual) found in each spawning population. Those baselines allow sturgeon to be identified back to their natal river. For instance, Atlantic sturgeon that are accidentally captured or killed in non-research-related projects can be matched to the river where they were born using their genotype.

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Genetic variation (“heterogeneity”) within the population can also be used to estimate the minimum number of spawning adults that would have been required to generate that level of heterogeneity. This information helps us learn more about the approximate number of successfully spawning adults, their natal river, and their family history. NOAA Fisheries, in cooperation with the U.S. Geological Survey, has been maintaining stored tissue and DNA samples and records of Atlantic sturgeon, as well as shortnose sturgeon.

NOAA Fisheries, in partnership with numerous federal and academic researchers, estimates and monitors effective population size of the spawning populations that have been adequately sampled. While effective population sizes are not easily translated to actual abundance estimates, they can provide a rough comparison between populations to better understand relative abundance and threats of inbreeding or extirpation. The most recent estimates of effective population size, from north to south are:

• St. Lawrence River – between 28 and 44 individuals
• St. John River – between 75 and 104 individuals
• Kennebec River – between 52 and 89 individuals
• Connecticut River – between 2 and 3 individuals
• Hudson River – between 138 and 176 individuals
• Delaware River – between 34 and 46 individuals
• James River – between 29 and 36 individuals
• York River – between 6 and 12 individuals
• Albemarle Sound (likely Roanoke River population) – between 16 and 21 individuals
• Edisto River – between 52 and 69 individuals
• Savannah River – between 103 and 150 individuals
• Ogeechee River – between 23 and 29 individuals
• Altamaha River – between 128 and 175 individuals
• Satilla River – between 18 and 23 individuals
• St. Marys River – between 1 and 2 individuals

Side Scan Sonar

Side scan sonar has been used to approximate the number of sturgeon that appear on the resulting images. However, this approach is still being perfected. Most rivers are also too large to allow for sampling of the entire river. Corrections are therefore needed to account for unsampled areas as well as fish that are counted multiple times during surveys.

Reducing Bycatch

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We have funded research on new fishing gear configurations that maintain catch rates of the target species but limit bycatch of Atlantic sturgeon. For gill nets, using a raised footrope has shown promise for some fisheries. For trawls, turtle excluder devices are also effective at keeping Atlantic sturgeon out.

The likelihood of mortality of incidentally gill-netted Atlantic sturgeon appears to be related to water quality, how the net is set, and the length of time before the net is tended. Atlantic sturgeon incidentally captured in cooler waters have a greater likelihood of survival than those captured in warmer waters. Anchored gill nets (i.e., set on the bottom, as opposed to floating at the surface) tend to pose the greatest risk for mortality of Atlantic sturgeon, compared to other gill nets or types of gear. Atlantic sturgeon incidentally captured in cooler waters have a greater likelihood of survival than those captured in warmer waters.

Stock Assessment

In 2013, the Atlantic States Marine Fisheries Commission initiated a coastwide population assessment for Atlantic sturgeon to evaluate stock status, stock delineation, and bycatch. The assessment was completed in October 2017. It concluded all DPSs remain depleted, and the Gulf of Maine and Carolina DPSs are experiencing higher levels of mortality than the other DPSs. It also determined the probabilities of a DPS having increased since the coastwide moratorium on fishing for Atlantic sturgeon was implemented in 1998. Across all five DPSs, the assessment concluded there was a 95 percent probability that abundance has increased since 1998. However, the probability of increase varied widely at the individual DPS level. The probability of an abundance increase since 1998 for the Gulf of Maine DPS was estimated at only 51 percent, while the probability of increase for Chesapeake Bay DPS was even lower at just 36 percent.

Sturgeon Salvage Program

The Sturgeon Salvage Program maximizes the scientific use of shortnose and Atlantic sturgeon that are found dead in the wild and reported to us by the public. Our designated co-investigators examine the sturgeon and collect information that helps us to better understand how sturgeon are affected by threats in the environment. Maximizing the use of the opportunistically found dead sturgeon also reduces the need to capture and sample living sturgeon.

Source: https://en.congthucvatly.com
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