Evidence of Lake Trout Reproduction at Lake Michigan's Mid-lake Reef Complex

Acoustic estimates of abundance and distribution of spawning lake trout on Sheboygan Reef in Lake Michigan

“…The MLRC was historically productive as a spawning area (Brown et al, 1981;Dawson et al, 1997) and has received paired stockings of Marquette and Seneca strains of lake trout pursuant to the Lakewide Management Plan implemented in 1985 . Bronte et al (2007) found that Sheboygan and East Reefs had the highest spawner catch-per-effort of any spawning location sampled in 1999-2001, and Janssen et al (2006 have confirmed deposition of viable eggs and production of fry at these two locations in [2001][2002][2003][2004]. Lake trout restoration research has been focused on identifying impediments to restoration, but a number of key questions remain unanswered.…”

“…To help address this concern, visual observations of fish were made during the acoustic survey using a VideoRay Pro II, remotely operated vehicle (ROV) by the R/V Neeskay operated by the University of Wisconsin-Milwaukee Great Lakes WATER Institute. The ROV was operated in an area called Edsall's Ridge where we previously observed evidence of lake trout spawning, and where fish targets were observed with a non-scientific echosounder during previous surveys (Janssen et al, 2006). The ROV was operated so that the visual axis was oriented approximately along Edsall Ridge's axis.…”

“…The ability to assess egg, fry, and spawner abundance, as well as potential survival is dependent on the ability to locate spawning habitat and aggregations of spawners. On the MLRC, Janssen et al (2006) recently observed successful spawning and lake trout fry production. Given the size and heterogeneous distribution of spawning habitat at Sheboygan Reef (Edsall and Kennedy, 1995), it is possible that higher egg densities occur but have not been detected.…”

Measures of larval lake whitefish length and abundance as early predictors of year-class strength in Lake Michigan

“…Since 1998, unclipped lake trout, which were presumed to be wild (all stocked fish received a fin clip), comprised about 2% of the population, which was within detection error. Only small numbers of fertilized eggs and fry were collected recently in northern Lake Michigan Jonas et al 2005b) and at the Southern Refuge (Janssen et al 2006). …”

An inexpensive remotely operated vehicle for underwater studies

“…These applications include exploration and sampling of specific ecosystems (i.e., Biddanda et al 2006); measurements of the distribution and abundance of zooplankton (Schulze et al 1995), gelatinous plankton (Bergstrom et al 1992), and fish (Janssen et al 2006); and monitoring water pollution (Lygouras et al 1998). Other applications could document fish reproduction or crustacean life history, use sampling devices to trace the influx of groundwater or contaminants to a lake or river, or explore the colonization of artificial substrates by invertebrates.…”