Spatial heterogeneity and long-term changes in bivalveAnadara broughtoni population: influence of river run-off and fishery |
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Authors: | Alla V Silina |
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Institution: | (1) Institute of Marine Biology, Far East Branch, Russian Academy of Science, 690041 Vladivostok, Russia |
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Abstract: | A comparison was made of population of the economically important cockleAnadara (=Scapharca)broughtoni (Bivalvia, Arcidae) inhabiting different areas of the Razdolnaya River estuary at the head of Amurskii Bay (Peter the Great
Gulf, East Sea). Also, changes in cockle population density and structure, as well as in cockle growth rates during the last
20 years were studied. In all years of investigation, the morphometrical parameters and growth rates of cockles were smaller
at the sites located close to the River mouth than farther down-estuary. The differences can be attributed to higher concentration
of suspended particulate matter, decreased salinity and water temperature, as well as a longer exposure to these unfavorable
environmental factors at sites located close to the River mouth, compared to farther sites. For two decades, cockle population
density had decreased by almost 30 times at some sites in the River estuary. The main reason for this population decline is
commercial over-fishing of the cockle. Besides, for the last 20 years, linear parameters of the cockles in the population
decreased approximately by 30% and weight parameters, almost two times. Cockle growth rates also decreased for this period.
Evidently, these facts are due to the damaging effect of dredging. |
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Keywords: | benthos trawling mollusk estuary spatial distribution age growth |
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