Assessment of Zebra Mussel (Dreissena Polymorpha) Infestation Risk Using GIS for Water Basins in the North-West Bulgaria

2007 ◽  
Author(s):  
Teodora A. Trichkova ◽  
Alexander A. Kotsev ◽  
Anton Popov ◽  
Mladen T. Zivkov ◽  
Dimitar S. Kozuharov ◽  
...  
Keyword(s):  
Zebra Mussel ◽  
Dreissena Polymorpha ◽  
North West ◽  
The North

scholarly journals Has Dreissena polymorpha, an older immigrant in a coastal Baltic lagoon, responded to appearance of a new non-indigenous dreissenid?

2018 ◽  
Author(s):  
Brygida Wawrzyniak-Wydrowska ◽  
Anna Skrzypacz ◽  
Adam Wozniczka ◽  
Teresa Radziejewska
Keyword(s):  
Population Structure ◽  
Size Distribution ◽  
Zebra Mussel ◽  
Dreissena Polymorpha ◽  
Indigenous Species ◽  
Large Share ◽  
Szczecin Lagoon ◽  
The North ◽  
Clear Peak ◽  
Non Indigenous Species

Although a non-indigenous species, Dreissena polymorpha (zebra mussel) has constituted a constant and abundant component of the Szczecin Lagoon biota. A congeneric dreissenid, D. rostriformis bugensis (quagga), was first recorded in the north of the Lagoon in 2014, already in abundance. In summer 2015, the quagga dominated over the zebra mussel in abundance and biomass. Quagga individuals there were much larger than those of D. polymorpha, while elsewhere in the Lagoon the zebra mussel still dominated the dreissenid assemblages. In summer 2016, the population structure of D. r. bugensis was substantially modified and its abundance was greatly reduced. D. polymorpha became the dominant again. In terms of biomass, after the initial domination, D. r. bugensis biomass declined substantially. The zebra mussel, although represented mostly by small individuals, has become a biomass dominant too on account of its high abundance. As of mid-2016, there has been no clear peak (evidencing the appearance of juveniles) in the quagga size distribution. The recent dreissenid samples show a large share of empty quagga shells, an effect not observed earlier. Therefore, it is plausible that the older immigrant, so far at least, has outcompeted the newcomer.

scholarly journals Has Dreissena polymorpha, an older immigrant in a coastal Baltic lagoon, responded to appearance of a new non-indigenous dreissenid?

2018 ◽  
Author(s):  
Brygida Wawrzyniak-Wydrowska ◽  
Anna Skrzypacz ◽  
Adam Wozniczka ◽  
Teresa Radziejewska
Keyword(s):  
Population Structure ◽  
Size Distribution ◽  
Zebra Mussel ◽  
Dreissena Polymorpha ◽  
Indigenous Species ◽  
Large Share ◽  
Szczecin Lagoon ◽  
The North ◽  
Clear Peak ◽  
Non Indigenous Species

Although a non-indigenous species, Dreissena polymorpha (zebra mussel) has constituted a constant and abundant component of the Szczecin Lagoon biota. A congeneric dreissenid, D. rostriformis bugensis (quagga), was first recorded in the north of the Lagoon in 2014, already in abundance. In summer 2015, the quagga dominated over the zebra mussel in abundance and biomass. Quagga individuals there were much larger than those of D. polymorpha, while elsewhere in the Lagoon the zebra mussel still dominated the dreissenid assemblages. In summer 2016, the population structure of D. r. bugensis was substantially modified and its abundance was greatly reduced. D. polymorpha became the dominant again. In terms of biomass, after the initial domination, D. r. bugensis biomass declined substantially. The zebra mussel, although represented mostly by small individuals, has become a biomass dominant too on account of its high abundance. As of mid-2016, there has been no clear peak (evidencing the appearance of juveniles) in the quagga size distribution. The recent dreissenid samples show a large share of empty quagga shells, an effect not observed earlier. Therefore, it is plausible that the older immigrant, so far at least, has outcompeted the newcomer.

Patterns in the Distribution and Abundance of Zebra Mussel (Dreissena polymorpha) in Rivers and Lakes in Relation to Substrate and Other Physicochemical Factors

1994 ◽  
Vol 51 (5) ◽  
pp. 1024-1036 ◽  
Author(s):  
Eric Mellina ◽  
Joseph B. Rasmussen
Keyword(s):  
New York ◽  
Zebra Mussel ◽  
Dreissena Polymorpha ◽  
Secchi Depth ◽  
Maximum Width ◽  
The North ◽  
Suitable Substrate ◽  
Physicochemical Factors ◽  
South Shore ◽  
Substrate Size

Using SCUBA and an in situ method of quantifying substrate characteristics, we describe patterns of zebra mussel (Dreissena polymorpha) distribution along the St. Lawrence and Hudson rivers and in Oneida Lake, New York, and develop empirical models for their abundance. Calcium-poor waters originating from rivers draining the Canadian Shield resulted in a complete lack of zebra mussel colonization along the north shore of the St. Lawrence River east of Montreal despite an abundance of suitable substrate. Calcium concentrations of 15 mg/L or less limited the distribution of zebra mussel. The entire south shore from Cornwall, Ontario, to île d'Orléans, Quebec, was colonized by zebra mussel wherever suitable substrate was found. Among the three systems, substrate size explained between 38 and 91% of the variability in density. Other factors such as Secchi depth, calcium concentration in the water, the presence of crayfish, native unionid abundance, and the maximum width of the river at the site increased the amount of explained variance across the different systems. A model based on substrate size also successfully explained patterns of zebra mussel abundance from published sources.

scholarly journals Remnant Freshwater Mussel Diversity in Rondeau Bay, Lake Erie

2016 ◽  
Vol 130 (1) ◽  
pp. 76
Author(s):  
Scott M. Reid ◽  
Victoria Kopf ◽  
Anita LeBaron ◽  
Todd J. Morris
Keyword(s):  
Zebra Mussel ◽  
Dreissena Polymorpha ◽  
Lake Erie ◽  
Coastal Wetland ◽  
Freshwater Mussel ◽  
Species At Risk ◽  
North Shore ◽  
The North ◽  
Viable Population ◽  
Substantial Decline

In 2014 and 2015, 27 sites in Rondeau Bay, Ontario, Canada, were surveyed for freshwater mussels. Rondeau Bay is a large coastal wetland on the north shore of Lake Erie. Twenty-three species were identified from 120 live mussels, 15 fresh whole shells, 329 weathered whole shells, and 1121 weathered valves. Live individuals of the following species were collected: Eastern Pondmussel (Ligumia nasuta; endangered in Canada), Giant Floater (Pyganodon grandis), Round Pigtoe (Pleurobema sintoxia;endangered in Canada), and Three-ridge (Amblema plicata). Fresh whole shells of the Mapleleaf (Quadrula quadrula; threatenedin canada) were also found. Most species (78%), including 7 species at risk, were collected only as weathered shells. These results indicate a substantial decline in freshwater mussel diversity since the Zebra Mussel (Dreissena polymorpha) invasion of Lake Erie. Evidence shows that a viable population of only Giant Floater remains.

SEM and TEM observations of sperm development in the testis of the freshwater fish Oreochromis mossambicus

1990 ◽  
Vol 48 (3) ◽  
pp. 58-59
Author(s):  
Daryl A. Cornish ◽  
George L. Smit
Keyword(s):  
Morphological Characteristics ◽  
Oreochromis Mossambicus ◽  
Breeding Cycle ◽  
Limited Information ◽  
North West ◽  
The North ◽  
Sem And Tem ◽  
Sperm Development ◽  
Ultrastructural Characteristics ◽  
The University

Oreochromis mossambicus is currently receiving much attention as a candidater species for aquaculture programs within Southern Africa. This has stimulated interest in its breeding cycle as well as the morphological characteristics of the gonads. Limited information is available on SEM and TEM observations of the male gonads. It is known that the testis of O. mossambicus is a paired, intra-abdominal structure of the lobular type, although further details of its characteristics are not known. Current investigations have shown that spermatids reach full maturity some two months after the female becomes gravid. Throughout the year, the testes contain spermatids at various stages of development although spermiogenesis appears to be maximal during November when spawning occurs. This paper describes the morphological and ultrastructural characteristics of the testes and spermatids.Specimens of this fish were collected at Syferkuil Dam, 8 km north- west of the University of the North over a twelve month period, sacrificed and the testes excised.

The North West Passage

2014 ◽  
Author(s):  
Roald Amundsen ◽  
Godfred Hansen
Keyword(s):  
North West ◽  
The North
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