Viral haemorrhagic septicaemia virus (VHSV) was isolated from muskellunge, Esox masquinongy (Mitchill), caught from the NW portion of Lake St Clair, Michigan, USA in 2003. Affected fish exhibited congestion of internal organs; the inner wall of the swim bladder was thickened and contained numerous budding, fluid-filled vesicles. A virus was isolated using fish cell lines inoculated with a homogenate of kidney and spleen tissues from affected fish. Focal areas of cell rounding and granulation appeared as early as 24 h post-inoculation and expanded rapidly to destroy the entire cell sheet by 96 h. Electron microscopy revealed virions that were 170-180 nm in length by 60-70 nm in width having a bullet-shaped morphology typical of rhabdoviruses. The virus was confirmed as VHSV by reverse transcriptase-polymerase chain reaction. Sequence analysis of the entire nucleoprotein and glycoprotein genes revealed the virus was a member of the North American genotype of VHSV; however, the isolate was sufficiently distinct to be considered a separate sublineage, suggesting its origin may have been from marine species inhabiting the eastern coastal areas of the USA or Canada.

In 2003, viral hemorrhagic septicemia virus (VHSV) emerged in the Laurentian Great Lakes causing serious losses in a number of ecologically and recreationally important fish species. Within six years, despite concerted managerial preventive measures, the virus spread into the five Great Lakes and to a number of inland waterbodies. In response to this emerging threat, cooperative efforts between the Michigan Department of Natural Resources (MI DNR), the Michigan State University Aquatic Animal Health Laboratory (MSU-AAHL), and the United States Department of Agriculture-Animal and Plant Health Inspection Services (USDA-APHIS) were focused on performing a series of general and VHSV-targeted surveillances to determine the extent of virus trafficking in the State of Michigan. Herein we describe six years (2005–2010) of testing, covering hundreds of sites throughout Michigan’s Upper and Lower Peninsulas. A total of 96,228 fish representing 73 species were checked for lesions suggestive of VHSV and their internal organs tested for the presence of VHSV using susceptible cell lines. Of the 1,823 cases tested, 30 cases from 19 fish species tested positive for VHSV by tissue culture and were confirmed by reverse transcriptase polymerase chain reaction (RT-PCR). Gene sequence analyses of all VHSV isolates retrieved in Michigan demonstrated that they belong to the emerging sublineage “b” of the North American VHSV genotype IV. These findings underscore the complexity of VHSV ecology in the Great Lakes basin and the critical need for rigorous legislation and regulatory guidelines in order to reduce the virus spread within and outside of the Laurentian Great Lakes watershed.

para proteger y mejorar los sistemas fluviales. Con el fin de satisfacer esta necesidad, en la presente contribución se desarrolla un marco jerárquico-espacial y una base de datos utilizando la Base Nacional de Datos Hidrográficos 1:100,000. El marco conceptual toma la inter-confluencia de los ríos y la red de cuencas como unidades espaciales fundamentales. Además de una serie de descriptores ecológicos y políticos como estructuras jerárquicas que permiten al usuario extraer o analizar información en las escalas espaciales de su preferencia. Esta base de daros consiste en variables que describen las características del canal, posición y conectividad de la red, clima, elevación, gradiente y tamaño. Contiene una serie de factores naturales y antropogénicos relativos a la captación cuya influencia sobre las características de los ríos es bien conocida. El marco conceptual y la base de datos ensamblan por primera vez todos los ríos de los Estados Unidos de Norteamérica, y sus descriptores. El marco y la base de datos ofrecen al usuario la posibilidad de agregar información, realizar análisis, desarrollar escenarios de manejo y regulación y dar seguimiento a los procesos del manejo en distintas escalas espaciales. Esta base de datos provee la información esencial para cumplimentar los objetivos del ENHPF así como de otros programas de manejo,.

We developed and validated a simple and accurate assignment rule, based on one quantified scale characteristic, for the identification of wild and hatchery stocks of Great Lakes steelhead Oncorhynchus mykiss (formerly Salmo gairdneri). A ratio between the first winter and spring growth rates, inferred from scale circulus patterns, met the criteria of being both distinct between wild and hatchery adults and consistent among life stages, years, and geographic locations within respective wild and hatchery groups. This rule was applied to samples of unknown‐origin adult steelhead collected in seven rivers in the northwestern Lower Peninsula of Michigan during 1983–1984, to estimate the percentage of wild fish in each river and its variance. Adults returning during these periods were representative of pre‐1983 hatchery production in Michigan, when yearling parr was the typical life stage stocked. The percentage of wild fish in the adult population was estimated to be 100% for an unstocked trout river, 93% for four stocked trout rivers, and 60% for two stocked marginal trout rivers. This method should be applicable in other regions with similar winter temperature regimes and, possibly, to other species that are reared a full year in a hatchery.

Summary Historical abundance and biomasss of lake sturgeon (Acipenser fulvescens Rafinesque, 1817) in the Great Lakes were estimated from historical commercial harvest data from 1879 to 1920 using two modeling techniques: a surplus production model with a Bayesian approach, and a depletion model. In addition, theoretical sustainable levels of exploitation and temporal recovery periods were estimated based on the surplus production model. The historical biomass of Lake Sturgeon in the Great Lakes during the period from 1879 to 1885 varied for each model and ranged from 313 900 to 6 473 000 kg (0.5–16.7 kg ha−1) using the surplus production model to 968 000 to 25 414 000 kg (2.4–31.7 kg ha−1) using the depletion model. The intrinsic population growth rate as determined from the surplus production model ranged from 0.079 to 0.123, and the theoretical sustainable exploitation rate ranged from 2.0 to 3.1%. The predicted recovery period for the overexploited populations was in excess of 60 years given recruitment assuming all other impediments to population recovery were removed.