AN EXAMINATION OF OYSTER GROWTH WITH FISH AND MACROINVERTEBRATE DIVERSITY IN TWO OYSTER AQUACULTURE GEAR TYPES
Date
2023-05
Authors
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Publisher
University of Delaware
Abstract
Eastern Oysters (Crassostrea virginica) are an important resource for
Delawareans living near the Delaware Bay and Delaware’s Inland Bays.
Unfortunately, natural oyster populations in Delaware have been greatly reduced
because of historical overharvest and disease vectors, among other factors. In response
to low wild abundance and a general interest from the public, commercial oyster
aquaculture was reinstated in the Inland Bays in 2017. In multiple studies along the
U.S. east coast and within the Inland Bays, fishes and invertebrates have been
observed around oyster cages and other types of gear used to grow oysters. However,
my project examined oyster growth in an experimental cage and evaluated habitat
provisions to juvenile fishes in that gear. My project aimed to further our scientific
understanding of the ecological services rendered by shellfish farming in a
comparative capacity by examining the habitat value of 1) traditional on-bottom
commercial aquaculture gear and 2) an experimental floating gear type actively used
by a commercial oyster farmer. From June through September 2022, the abundance
and diversity of fishes and motile macroinvertebrates found within and around each
aquaculture gear type were recorded weekly. Additionally, measurements of oyster
length and depth were collected weekly to monitor oyster growth. Traditional bottom
cages produced significantly longer and deeper oysters than the experimental floating
cages with no significant difference in mortality. Abundance and diversity of fishes
was high in bottom cages, but floating cages with nearby structure can support similar
fish assemblages. Floating cages hosted significantly higher abundance of
invertebrates, predominantly driven by grass shrimp, but trends in invertebrate
diversity mirrored fish diversity with high diversity in bottom cages and floating cages
with additional structure nearby.