3 research outputs found
Ingestion of Small-Bodied Zooplankton by Zebra Mussels (Dreissena polymorpha): Can Cannibalism on Larvae Influence Population Dynamics?
The zebra mussel Dreissena polymorpha established populations in western Lake Erie in 1986 and achieved densities exceeding 3.4âĂâ105 individualsâmâ2 during 1990. We assessed apparently incidental predation on Lake Erie and Erindale Pond zooplankton by adult mussels. Dreissena larvae and small rotifers (Polyarthra spp., Keratella spp., Trichocerca) sustained moderate to high predatory mortality whereas larger taxa (Bosmina, Scapholeberis) were invulnerable to predation. Larval Dreissena almost always sustain \u3eâ99% mortality in European lakes. While mortality has been ascribed primarily to lack of suitable settling substrate and unfavourable environmental conditions, it may be confounded by larval predation by adults. We demonstrate using STELLAâą-modelling that with a larval mortality rate of 99%, settled mussel densities observed in western Lake Erie during 1990 would not be achieved until at least 1994. A model that combines a lower rate (70%) of abiotic mortality with larval predation by adult mussels c..., Les populations de dreissena polymorphe (Dreissena polymorpha) dĂ©jĂ Ă©tablies dans la partie ouest du lac ĂriĂ© en 1986 atteignaient des densitĂ©s supĂ©rieures Ă 3,4âĂâ105 individus par mĂštre carrĂ© au cours de 1990. Nous avons Ă©valuĂ© Ta prĂ©dation du zooplancton du lac ĂriĂ© et de l\u27Ă©tang Erindale par les dreissenas adultes. Les larves des dreissenas et les petits rotifĂšres (Polyarthra spp., Keratella spp., Trichocerca) prĂ©sentaient une mortalitĂ© par prĂ©dation variant de moyenne Ă Ă©levĂ©e tandis que les plus gros taxons (Bosmima, Scapholeberis) rĂ©sistaient Ă toute prĂ©dation. Les larves de Dreissena des lacs europĂ©eens prĂ©sentent presque toujours un taux de mortalitĂ© supĂ©rieur Ă 99%. La mortalitĂ© a surtout Ă©tĂ© attribuĂ©e Ă l\u27absence d\u27un substrat de fixation adĂ©quat et Ă des conditions environnementales dĂ©favorables, mais elle peut ĂȘtre confondue avec celle dĂ©coulant de la prĂ©dation des larves par les adultes. Nous avons montrĂ©, Ă l\u27aide d\u27un modĂšle STELLAmd, que les densitĂ©s de dreissenas fixĂ©es notĂ©es en 1990 n\u27..
Acineta nitocrae: A new suctorian epizooic on nonindigenous harpacticoid copepods, Nitocra hibernica and N. incerta, in the Laurentian Great Lakes
Acineta nitocrae, a suctorian ciliate previously known from Ukraine, was discovered in western Lake Erie in October 1997 and in the Detroid in May 1999. Idividuals were found inhabiting the body surface of Nitocra hibernica and N. incerta, nonindigenous harpacticoid copepods
Possible Ballast Water Transfer of Lionfish to the Eastern Pacific Ocean
The Indo-Pacific Red Lionfish was first reported off the Florida coast in 1985, following which it has spread across much of the SE USA, Gulf of Mexico, and Caribbean Sea. Lionfish negatively impact fish and invertebrate assemblages and abundances, thus further spread is cause for concern. To date, the fish has not been reported on the Pacific coast of North or Central America. Here we examine the possibility of ballast water transfer of lionfish from colonized areas in the Atlantic Ocean to USA ports on the Pacific coast. Over an eight-year period, we documented 27 commercial vessel-trips in which ballast water was loaded in colonized sites and later discharged untreated into Pacific coast ports in the USA. California had the highest number of discharges including San Francisco Bay and Los Angeles-Long Beach. A species distribution model suggests that the probability of lionfish establishment is low for the western USA, Colombia and Panama, low to medium for Costa Rica, Nicaragua, El Salvador and Guatemala, medium to high for mainland Ecuador, and very high for western Mexico, Peru and the Galapagos Islands. Given the speciesâ intolerance of freshwater conditions, we propose that ballast water exchange be conducted in GatĂșn Lake, Panama for western-bound vessels carrying âriskyâ ballast water to prevent invasion of the eastern Pacific Ocean