Publisher :
Place of publication :
Publication year : 0
Thematic : Coral Reef
Language : English
Note
We conducted a large-scale
field experiment to test whether clam
and oyster harvesting applied alone and
in combination on intertidal oyster reefs
have impacts on resident shellfish populations.
This experiment was conducted
to resolve a long-standing conflict between
oyster (Crassostrea virginica
(Gmelin, 1791)) and clam (Mercenaria
mercenaria (Linneaus, 1758)) fishermen
who contend that the other fishery causes
high rates of mortality to their respective
species. Intertidal oyster reefs located in
two estuarine creeks near Wilmington,
North Carolina, were harvested for clams
only, oysters only, both clams and oysters,
or were left undisturbed as controls.
Experimental harvesting was conducted
over a one-year period by a professional
shellfisherman who used realistic fishing
techniques (clam rakes and oyster
tongs), intensity, and frequency. Harvesting
impact on hard clam and oyster
populations was assessed by sampling
naturally occurring oysters before and
after harvesting, and sampling both naturally
occurring clams (all size classes)
and transplanted, hatchery-raised clams
(20–37 mm in length) after harvesting.
Clam and oyster harvesting had obvious
negative effects on populations of oysters.
There was a substantial decrease in
the number of live oysters on clam-harvested
and oyster-harvested reefs compared
with unharvested, control reefs.
Clam and oyster harvesting, applied
together, reduced oyster densities and
killed unharvested oysters at a level similar
to that caused by each type of harvesting
applied separately. The effects of
the shellfish harvesting on populations of
hard clams varied between the two sites
(i.e. creeks). In both creeks, clam harvesting,
alone and combined with oyster
harvesting, significantly decreased the
number of live, naturally occurring
clams. Oyster harvesting alone decreased
the number of live, naturally occurring
clams only at one site. Clam harvesting
also decreased the number of live, transplanted
clams on reefs, but there was
no effect of oyster harvesting, because
the transplanted clams were juveniles
too small to be harvested with oyster
tongs. Overall, the combined effect of
both types of harvesting applied together
did not have a negative synergistic effect
on clam and oyster populations. Consequently,
both clamming and oyster harvesting
should be permitted on some
reefs, but maintaining large populations
of oysters and clams on intertidal oyster
reefs will require protection of some reefs
from both types of harvesting.
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Keywords : Nesolagus netscheri
Encoded by : Pauline Carmel Joy Eje
