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Spring Seining and Eel Migration Data

It has been a busy spring for us along Hudson with numerous seining programs and the DEC's American Eel Migration Study. Let's dig into some of our data from this spring.

 

Spring Seining Report

CURB’s spring seining season kicked off on April 22nd with a group from Riverdale Country School. As of June 9th, we seined with a total of 26 groups, collecting important data on the biodiversity of the Hudson River.

With the spring close to wrapping up, we wanted to take a look at this season’s data when compared to the past few years. The differences in the table below were quite notable.

 

Spring Seining Results

 

As you can clearly see, our totals for this year are much lower than the 3 previous springs. The figure to pay particular attention to is catch per group since our number of seining programs varies from year to year. If we look at this, our rate is just a little over 36% of what it was in the spring of 2017. You’ll find similar results when comparing this year’s numbers to 2015 and 2016.

 

Seining Results with Temperature

 

With these results in mind, we must take a look at what could have been responsible for the big drop in totals. The obvious place to start is with water temperatures. While the water started off on the cooler side at the beginning of the season, it eventually rebounded and ran near the mean of the previous seasons. Other parameters to investigate would be rainfall, salinity, and tides, but the data for this season is generally within close range of past years.

 

Seining Catch to Date

 

While there are no obvious environmental factors that resulted in reduced catches this spring, human impact could have played a role. Throughout the spring the waterfront just to our south was being dredged and constructed on for a pedestrian walkway. Perhaps this noise and frequent mixing up of the water could have played a role in reduced catches. The construction work is now completed so it will be interesting to see if our numbers rebound. In fact, we may be seeing some early signs of this as our average catch total for the first half of spring programs was 5.3 while this increased to 20.9 for programs after May 18th. This generally coincides with when the construction wrapped up.

 

Eel Migration Report

CURB’s sampling for the DEC’s American Eel Migration Project wrapped up on May 25th after 13 weeks of daily eel counts in our riverfront marsh. This was a very successful year for the project here at our Yonkers site with the highest seasonal count in our 5 years of sampling. In all, we counted and released 1,264 migrating glass eels. This was double last year’s total of 632 eels and well above our previous all-time high of 1,021 eels in 2015. We caught eels during all 13 weeks of our sampling, which was a first for our site. Please see the graph and table below for more statistics from this season as well as results from previous years.

 

Running Total of Eels Caught

 

Eel Data

 

We thank our dedicated team of eel volunteers who helped us throughout the season! In all, over 40 high school, college, and adult volunteers participated in the program this year. This great season of collecting eel data wouldn’t have been possible without their help.

We are looking forward to releasing a detailed report in the coming weeks analyzing our data (past and present), as well as comparing this year's results to the other project sites.