The goal of this survey is to collect abundance and biological data of spawning lake trout at index stations at two mid-lake reef complexes. The Service has stocked hundreds of thousands of lake trout yearlings on these two off-shore reefs in recent years. Two 400’ long, large-mesh gill nets were set on Yankee Reef for one night. All lake trout collected were measured for length, weighed, checked for lamprey wounds, sexed, assessed for maturity and visceral fat content, and sampled for ageing structures. Non-target fish species were worked up in a similar manner as well. The Alpena FRO has conducted the annual mid-lake lake trout spawning surveys on these reefs since 1993 with the M/V Togue.

In 2005, catch rates declined to an all time low at Yankee Reef.  Total catch rates were down 67 percent, and catch rates at the north and south Yankee Reef sites were down 85 percent and 54 percent, respectively, compared to 2004 data.  In 2004 catch rates were above 100 spawners/1,000 feet of net at both Yankee Reef sites, but in 2005 catch rates were 15 spawners/1,000 at the north site and 65 spawners/1,000 feet at the south site.  50 spawners/1000 feet of net is the mean abundance of spawners needed to support a viable, naturally reproducing lake trout population at other sites in the Great Lakes.  Also, no unclipped, presumably wild adult lake trout were captured at Yankee Reef in 2005.  This is a departure from 2004 when unclipped fish were sampled at each of the five mid-lake sites and 13 percent of Yankee Reef fish sampled were unclipped.

Low 2005 catch rates at Yankee Reef may indicate decreases in spawner abundance on this important off shore complex; however, low 2005 catch rates may also be due to warmer than normal air and water temperatures that delayed arrival of spawning fish.  Also due to poor weather, we fished the 2005 Yankee Reef survey 17 days earlier than in 2004.  This difference in timing may account for some of the difference between 2004 and 2005.