Influence of Water Depth on the Rate of Expansion of Giant Cutgrass Populations and Management Implications

Giant cutgrass ( Zizaniopsis miliacea (Michx.) Doell. & Asch.), a tall emergent grass native to the southeastern United States, was studied in Lake Seminole where it formed large expanding stands, and Lake Alice where it was confined to a stable narrow fringe.

Changes in a benthic megafaunal community due to disturbance from bottom fishing and the establishment of a fishery closure

Trawling and dredging on Georges Bank (northwest Atlantic Ocean) have altered the cover of colonial epifauna, as surveyed through in situ photography. A total of 454 photographs were analyzed from areas with gravel substrate between 1994 and 2000 at depths of 40–50 m and 80–90 m. The cover of hydroids, bushy bryozoans, sponges, and tubeworms was generally higher at sites undisturbed by fishing than at sites classified as disturbed. The magnitude and significance of this effect depended on depth and year. Encrusting bryozoans were the only type of colonial epifauna positively affected by bottom fishing. Species richness of noncolonial epifauna declined with increased bottom fishing, but Simpson’s index of diversity typically peaked at intermediate levels of habitat disturbance. Species that were more abundant at undisturbed sites possessed characteristics that made them vulnerable to bottom fishing. These characteristics include emergent growth forms, soft body parts, low motility, use of complex microhabitats, long life spans, slow growth, and larval dispersal over short distances. After the prohibition of bottom fishing at one site, both colonial and noncolonial species increased in abundance. Populations of most taxa took two years or more to increase after the fishing closure. This finding indicates that bottom fishing needs to be reduced to infrequent intervals to sustain the benthic species composition of Georges Bank at a high level of biodiversity and abundance.

Sur la présence de l'Enhalus acoroide (L.f.) Roem. et Schultes au littoral du Viêtnam

In the "Flore Générale de l'Indochine" three species of phanerogams have been described: Halophila ovalis (R. Br.) Hook. f., Diplanthera uninervis (Forsk.) Aschers. and Ruppia rostella Koch in Rchb. In 1954, Dawson added to this list Halophila Beccari Aschers. and Thalassia hemprichii (Ehrenb.) Aschers. Even Mr. Feldmann found in the herbarium of the Oceanographic Institute of Nha-Trang, the Cymodocea rotundata (Ehrenb. & Hernpr.) Asch. & Schweinf., that the authors found in Cua-Be (Nha trang), Qui-Nhon and Da-Nang (Tourane).