black sea red data book - Department of Biology

Distribution, Habitat type, Critical habitats, Limiting factors. Upogebia pusilla
inhabits burrows in sandy-clay and muddy bottoms. Sometimes, after a heavy storm,
specimens are cast ashore. A specific feature of its behaviour is that it leaves its hole
during the night to search for food. This causes mass mortality in conditions of
oxygen shortage, which is strongest in the night and is a result of the intense summer
phytoplankton blooms of the last ten years.
Biology. This species lives in holes in the ground that it leaves only to seek food. It
feeds on dead organic matter. It is monosexual, with summer reproduction. Many
benthic fish (flounder, gobies etc.) feed on it.
Population trends. In the 1960s the species had a high coefficient of occurrence on
the Bulgarian shelf (18.3%). At the beginning of the 1980s U. littoralis had the
highest mean biomass of all crustaceans in Burgas bay. At the same period it was
common in Varna bay, in the biocoenoses called by its name. In the 1990s a strong
decline was recorded, due to mass mortality of benthos in the post-bloom hypoxia
periods that began in 1986. Four dead individuals per square meter were recorded in
Varna bay on 29.06.1989. In 1991, the species did not occur in benthic samples at all.
Single individuals were recorded in 1996 around Cape Kaliakra and in front of Burgas
bay.
Threats. Hypoxia of bottom waters during summer due to blooms of phytoplankton.
Conservation measures taken. No measures up to now.
Conservation measures proposed. Reduction of pollution and eutrophication to
restrict algal blooms.
380