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Tuesday, January 26 • 1:20pm - 1:40pm
Large-Scale Spatial and Temporal Variability In Lake Huron Bloater Growth and Population Structure, 1976-2014

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AUTHORS: Carson G. Prichard*, USGS Great Lakes Science Center; Edward F. Roseman, USGS Great Lakes Science Center; Timothy P. O’Brien, USGS Great Lakes Science Center; Kevin Keeler, USGS Great Lakes Science Center and Michigan State University

ABSTRACT: In Lake Huron, bloater Coregonus hoyi are the sole extant species of a diverse clade of deepwater ciscoes that supported commercial fisheries and native piscivore diets before populations collapsed in the late 1960s. Following the crashes of rainbow smelt and alewife, bloater are again the primary offshore constituent of the Lake Huron prey fish community. Despite recent recoveries in bloater abundance and biomass, the contemporary fishery catches few marketable-size bloater. Using USGS annual fall bottom trawl survey data, we assessed variability in bloater body condition, age-length relations, and size- and age-structure in the main basin of Lake Huron from 1976-2014. To examine trends in body condition, we estimated bloater body mass at selected lengths by fitting weight-length relations to a standard power function that allowed growth parameters to vary over time and among regions. We compared models whose temporal effects followed either white noise or random walk processes. Trends in bloater weight-at-length differed significantly between northern and southern Lake Huron, as well as among several selected lengths. Basin-wide, mean weight decreased significantly across the time series at larger lengths. Estimated weight of 225 mm bloaters decreased 0.39 g/year from 89.9 g in 1976 to 75.2 g in 2014. In contrast, mean weight at 150 mm showed no significant changes across the time series. Based upon von Bertalanffy growth models fitted to selected year groupings, basin-wide bloater length-at-age declined consistently and drastically across the time series. Asymptotic length decreased >50% between 1977-79 (416 mm) and 2012 (199 mm). Combined with periods of near-zero recruitment (1976-80 and 1990-2004), size structure skewed from >66% of bloater exceeding 220 mm (1994-97) to

Tuesday January 26, 2016 1:20pm - 1:40pm
Emerald A

Attendees (14)