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Methods for  Use of a Remotely Operated Vehicle to Study Lake Trout Spawning on a Deep Reef in Lake Michigan (John Janssen and Rob Paddock)
 

Recruitment failure of lake trout in Lake Michigan, and most other Great Lakes, is a decades long mystery. Lake trout went extinct in Lake Michigan during the 1950's due to the combined effects of sea lamprey predation and overfishing. Efforts to re-establish lake trout began in the mid-1960's following successful sea lamprey control, but natural reproduction has been negligible. One of the major spawning areas for the indigenous lake trout was deep-water reefs located at the Mid-Lake Reef complex, an area of 2859 km2, and much recent stocking effort has been focused on this area. For a map that includes the Mid-Lake Reef Complex (plateau) see www.ngdc.noaa.gov/mgg/greatlakes/ lakemich_cdrom/html/geomorph.htm .

 

The best stringer of naturally reproduced lake trout from Lake Michigan in half a century. From left to right, Chris Malinowski, John Janssen, and Rob Paddock; ROV partially in view behind them.

 

The following images illustrate the use of ROV's to study lake trout reproduction on deep reefs.  The ROV (Remotely Operated Vehicle) used for most of the video clips is a Benthos MiniRover MK-II owned by the National Underseas Reasearch Program-North Atlantic and Great Lakes.  The essential components (electronics, thrusters) have been transferred to an aluminum frame that allows easy addition and removal of "plumbing" for different suction sample configurations, modifications to the electroshocker, and addition of extra cameras and diverse sensors.

This site focuses on technology rather than results.  Please return to the main page for various reports and papers on lake trout research.  Collaborators include Dave Jude (University of Michigan), Ellen Marsden (University of Vermont), Chuck Bronte (USFWS-Green Bay) and tough technicians and grad students such as Chris Houghton and Chris Malinowski.

Funding for modifications have come from the Great Lakes Fishery Trust, U.S. Fish and Wildlife Service, Wisconsin Sea Grant, and the National Underseas Research Program.  

 

Left.  Side view of the Benthos MiniRober MK-II ROV featured in many of the videos below.  The suction sampler and adjacent electrodes are visibly seen along with the main camera in its dome-shaped housing positioned forward on the main frame, just behind the suction sampler.  Right.  ROV control room on the R/V Neeskay equipped with monitors, GPS tracking devices, recording equipment, and an out of view shocker.    

Video Clips
Video from Sheboygan Reef and East Reef, two of the several reefs that compose the Mid-Lake Reef Complex which separate the northern and southern basins of Lake Michigan.  In days of yore, according to commercial fisherfolk, the area was a major spawning area for indigenous lake trout.  It is now a major site for attempting to restore lake trout to Lake Michigan.

Lake trout swimming past the ROV (Sheboygan Reef-Edsall Redge). Several lake trout were seen in a few minutes of aiming the camera at the underwater horizon. The lighting on the fish is ambient.  Edsall Ridge, composed of cobble and boulders, is about 1.5 km long and 2-3 meters above the Sheboygan Reef plateau. It attracts lake trout during the fall spawning period and we have collected fertilized eggs and and lake trout sac-fry from the site. 

At the end of the video the nozzle for suction sampling eggs is in view.

 
Slimy sculpin collection via electroshocking and suction sampling. The flutter is due to crosstalk between the suction sampler and the video. Do not adjust your set! The electroshocker draws a slimy sculpin from between the rocks where it was either hiding or searching for lake trout eggs. Something of a "lucky shot" because the sculpin swam into the suction field and rotated so you could see its plump, lake trout egg filled, belly.  This ROV is owned and operated by Dave Lovalvo.  The electrode configuration was two steel rods, one being the anode and the other being the cathode
 
Burbot chased down, stunned, and in the collection chamber.  Burbot can be very abundant at the reefs during the lake trout spawning reef.  They are easily stunned, but we usually do not collect them. These fish eat lake trout eggs and sculpins.   The electrode configuration has been changed so that the nozzle is the anode and is flanked by two cathodes.  the unexpected abundance of burbot adds a complicating factor because abundant burbot may consume many lake trout eggs, but may also be able to control the other egg predator, the sculpins. Burbot and sculpins are mostly unstudied factors in the Great Lakes ecosystem.
 
The viewable collection chamber with lake trout eggs collected from East Reef. A sample is sucked from between the reef cobble and captured on a screen (to the right but out of view.  To see the suction sampling nozzle: go to the end of the first video, the one showing adult lake trout.  Back-flushing allows for counting the eggs. Opaque eggs are dead; most of the live eggs can be incubated and hatched. Further back-flushing pushes the eggs into a downstream composite chamber that is emptied when the ROV returns to the surface.
 

Capture of an electroshocked lake trout sac-fry. This can be tough to follow and it is useful to start where the sac-fry is about to enter the nozzle (anode here), about 18:40:30 on the clock (upper right of video display screen), then back the video up. The sac-fry is first visible about 18:40:28 to the left of the nozzle. Do not be distracted by the Mysis after the sac-fry has been collected.
 

Additional Notes:

An abundance of Mysis shrimp can be observed on the reef and they are a major prey for very young lake trout.  They are patchy in abundance.  In the video we are chasing them from crevices into the water column with the electroshocker.

 

 

 

 

 

 

 

 


Lake bottom in Nov. 2001
Between the initiation of our work in 2001 and the present the Mid-Lake Reef Comple has beeninvaded by quagga mussels, a non-native, more cold-water active relative of zebra mussels. When we first visited Sheboygan Reef in 2001 we saw and collected only sparse zebra mussels.

Lake bottom in Nov. 2002
By spring 2002 we were seeing and collecting quaggas, which were noticeable and dominant by fall 2002. With little understanding of the original biological dynamics of the Mid-Lake Reef Complex it will be difficult to discern the impact of quaggas.

In submersible research one goes down with old ideas and comes up with new ones.
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