Distribution pattern, population structure, and growth of Septifer bilocularis (Bivalvia: Mytilidae) on reefs of Southern Vietnam
The features of the spatial distribution, size and age structure of populations, and growth of the bivalve mollusk Septifer bilocularis (Linnaeus, 1758) were investigated for the first time in the waters of Vietnam. It is shown that in the subtidal area, on
reefs well protected from wave effects, S. bilocularis occupies a corallogenous substrate constructed of dead branchy colonies of Acropora and Porites and forms settlements there with a population density and biomass exceeding those in populations located along the open coast
and developing on massive coral colonies of the genera Porites, Favia, and Favites. The extensive accumulation of sediments in the inner part of Vanphong Bay (Khanh Hoa Province) correlated with a decrease
in the size and age ranges for populations of S. bilocularis. It is found that in places with regularly active hydrodynamics the mollusks grew somewhat more slowly and formed a more
convex shell than on reefs protected from surf. The longevity of S. bilocularis estimated both from the greatest observed age and from the growth equation of Bertalanffy was somewhat greater in the former
case compared with the latter one, but in general did not exceed 11 years for both cases. The results of the studies are discussed
from the position of morphophysiological adaptations of sessile bivalve mollusks to life in contrasting environmental conditions
of the upper subtidal zone.
Available from: Miguel Griffin
- "Septifer is known to occur in rocks as early as Triassic, and is nowadays widespread in tropical and subtropical seas (Soot-Ryen, 1955; Beu and Maxwell, 1990). Recent species of Septifer inhabit upper subtidal zones attached to rocks or shell debris (Selin and Latypov, 2006). "
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ABSTRACT: Fairly large Mytilus trossulus beds were found in the subtidal zone at depths to 40 m off the western coast of Kamchatka. The size and age composition of
local populations and growth rates of M. trossulus in this region and at Atlasova Island were studied. Significant variability of the shell shape of mollusks was found. In
the western Kamchatka subtidal, M. trossulus grew faster than in the northern Kuril Islands and eastern Kamchatka. Mussels attained commercial size (50 mm in shell length)
in the fourth year of life in the former case and in the fifth-sixth year in other cases. Mollusks of different ages, from
1 to 8–9 year olds, were present in western Kamchatka populations; i.e., juvenile recruitment takes place regularly, while
growth rates vary. Growth and population structure of M. trossulus are discussed in relation to the habitat conditions on the western Kamchatka shelf.
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ABSTRACT: The composition and spatial distribution of the coral communities of the barrier reefs of Jiang Bo and of Re Island were described
in detail for the first time for Vietnamese waters. Their comparability to the ribbon reefs of the Great Barrier Reef in Australia
and to the barrier reefs of the Philippines and Indian Ocean was revealed by morphological parameters, species diversity and
zonal distribution. Their geomorphological status, the presence of fore reef, epi-reef and back reef complexes with their
specific composition of flora and fauna, and an obligatory lagoon separating the reef from fringing inshore reefs, enabled
the attribution of the surveyed reefs to the barrier type of reef.
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