Tuesday, February 17, 2015

Catch that Spat!

This year's spat catcher program has supplied the Lynnhaven River with 1,876 new oysters to continue growing, filtering, and reproducing in the river! 
Every year, volunteers around the watershed hang small wire cages (10"x 10" x 6") from their docks. One cage is filled with oyster shells while the other cage is filled with crushed concrete. The cages remain hanging from the docks for about 6 months from June through January. Volunteers pull their cages out of the water every month or so, give them a few shakes to keep them from becoming too muddy, and then put them back in the water to continue growing.
From about mid-June through October or November, oysters reproduce in the river and spat (larvae) floating through the water during this time discover the cages and settle on this substrate.
In January, once oysters stop actively growing for the winter, volunteers pull their cages out of the water and bring them to us. We then sift through lots of marsh critters and mud to count the number of spat from each cage. The point of counting the spat is to help us better understand the distribution of spat throughout the river, based on the location of each volunteer's cage.
"Marsh critters"

During the very successful 2014 spat catching season we discovered all kinds of interesting creatures scattered among the cages, including feather blennies, oyster toadfish, striped killifish, a black-fingered mud crab, and much more. Thanks to all of the hard work put forth by our volunteers, we are thrilled to announce that the total number of oyster spat collected by all fifteen volunteers was 1,876 spat! 951 of those were found in the shell cages while the other 925 spat were in the cages with crushed concrete. After the spat was counted, they were then placed on a sanctuary reef near First Landing State Park. 

Using the data collected we have found an increase in the amount of oyster spat in the river. In 2013, the total number of spat collected by all 25 volunteers was 1,319, including 520 from the Elizabeth River. These numbers give us a good indication that spat settlement in the Lynnhaven River during the summer of 2014 was better than during the summer of the previous year, which is great news! This also means that our 2014 oyster restoration projects probably fared well with natural spat settlement!

This data also helped confirm that crushed concrete can perform very well as a substitute for shell in future oyster reef restoration projects. Crushed concrete is a great alternative to limited and expensive oyster shell. 

Number of Spat Collected in 2013 & 2014:

# Spat Shell Cage
# Spat Concrete Cage
Total # Spat
(520 from Elizabeth River)

You can read more about the spat catcher program in the Virginian Pilot Beacon article written by Mary Reid Barrow here

We couldn't make this program happen without our volunteers! If you would like to become a volunteer for the Spat Catcher Program please contact our Restoration Project Coordinator, Meredith Malone.

Written by: Emily Bodsford
Edited by: Meredith Malone and Trista Imrich

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