The Clarkia lagerstätte (Latah Formation) of Idaho is well known for its beautifully preserved plant fossils as well as a fauna of insects and fish. Here we present the first known tetrapod fossil from these deposits. This specimen, recovered from the lower anoxic zone of the beds, is preserved as a carbonaceous film of a partial skeleton associated with a partial lower incisor and some tooth fragments. The morphology of the teeth indicates that the first tetrapod reported from Clarkia is a rodent. Its skeletal morphology as well as its bunodont and brachydont dentition suggests that it is a member of the squirrel family (Sciuridae). It is a large specimen that cannot be assigned to a known genus. 18 from these deposits. This specimen, recovered from the lower anoxic zone of the beds, is 19 preserved as a carbonaceous film of a partial skeleton associated with a partial lower incisor and 20 some tooth fragments. The morphology of the teeth indicates that the first tetrapod reported from 21 Clarkia is a rodent. Its skeletal morphology as well as its bunodont and brachydont dentition 22 suggests that it is a member of the squirrel family (Sciuridae). It is a large specimen that cannot 23 be assigned to a known genus. Instead, it appears to represent the first occurrence of a new taxon 24 with particularly gracile postcranial morphology likely indicative of an arboreal ecology. This 25 new specimen is a rare glimpse into the poorly known arboreal mammal fossil record of the 26 Neogene. It supports a greater taxonomic and ecological diversity of Miocene Sciuridae than 27 previously recognized and offers new lines of inquiry in the paleoecological research enabled by 28 the unique preservation conditions of the Clarkia biota.
Acoustic surveys were conducted in late summer/early fall during the years 1992-1996 and 2001-2013 to estimate pelagic prey fish biomass in Lake Michigan. Midwater trawling during the surveys as well as target strength provided a measure of species and size composition of the fish community for use in scaling acoustic data and providing species-specific abundance estimates. The 2013 survey consisted of 27 acoustic transects (546 km total) and 31 midwater trawl tows. Mean prey fish biomass was 6.1 kg/ha (relative standard error, RSE = 11%) or 29.6 kilotonnes (kt = 1,000 metric tons), which was similar to the estimate in 2012 (31.1 kt) and 23.5% of the long-term (18 years) mean. The numeric density of the 2013 alewife year class was 6% of the time series average and this year-class contributed 4% of total alewife biomass (5.2 kg/ha, RSE = 12%). Alewife ≥age-1 comprised 96% of alewife biomass. In 2013, alewife comprised 86% of total prey fish biomass, while rainbow smelt and bloater were 4 and 10% of total biomass, respectively. Rainbow smelt biomass in 2013 (0.24 kg/ha, RSE = 17%) was essentially identical to the rainbow smelt biomass in 2012 and was 6% of the long term mean. Bloater biomass in 2013 was 0.6 kg/ha, only half the 2012 biomass, and 6% of the long term mean. Mean density of small bloater in 2013 (29 fish/ha, RSE = 29%) was lower than peak values observed in 2007-2009 and was 23% of the time series mean. In 2013, pelagic prey fish biomass in Lake Michigan was similar to Lake Huron, but pelagic community composition differs in the two lakes, with Lake Huron dominated by bloater. 1Presented at:Great Lakes Fishery Commission Lake Michigan Committee Meeting Windsor, ON, March 25-26, 2014 2 INTRODUCTIONAnnual evaluation of long-term data on prey fish dynamics is critical in light of changes to the Lake Michigan food web during the last 40 years (Madenjian et al. 2002) and continued restructuring due to exotic species, pollution, fishing, and fish stocking. Alewives are the primary prey in Lake Michigan and of especial importance to introduced salmonines in the Great Lakes (Elliott 1993;Rybicki and Clapp 1996;Warner et al. 2008;Jacobs et al. 2013), and, as such, constitute an important food web component. The traditional Great Lakes Science Center (GLSC) prey fish monitoring method (bottom trawl) is inadequate for fish located off bottom (Fabrizio et al. 1997). In particular, bottom trawls provide particularly biased estimates for age-0 alewives (Alosa pseudoharengus) based on catchability estimates from stock assessment modeling (Tsehaye et al. 2014). Much of the alewife biomass will not be recruited to bottom trawls until age-3 (Madenjian et al. 2005), but significant predation by salmonines may occur on alewives ≤ age-2 . Alewife abundance patterns tend to be highly variable because recruitment of alewife is variable and total alewife density is highly correlated with the density of alewife ≤ age-2 . Because of the ability of acoustic equipment to count organisms far above bottom, this type ...
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