How many Salmon and Trout are in Lake Michigan?
The world-class recreational fishery of Lake Michigan has had a history of boom and bust, but the total number of salmon and trout in the lake has remained relatively stable.
On a tough day of fishing, you might swear there are no fish left in the lake, but with 1,180 cubic miles of water in Lake Michigan there is plenty of room for fish to roam. Fishing for salmon and trout in Lake Michigan has a history of ups and downs from one year to the next, and you might guess that salmon and trout numbers change wildly from one year to the next. It could come as a surprise to find out that the abundance of these predatory fish has been fairly consistent over the past twenty years.
Dr. Michael Jones and Dr. Iyob Tsehaye of the Quantitative Fisheries Center at Michigan State University have been using biological data from the U. S. Geological Survey, state management agencies, and others to model past abundance of salmon, trout, and forage fish. One of their conclusions is that the number of trout and salmon present in Lake Michigan has remained between 23 and 27 million since the mid-1980s. This works out to 1.7 fish per surface acre in an average year.
Chinook salmon and lake trout have fluctuated in abundance more than steelhead, brown trout, or coho salmon. The number of Chinook salmon has varied between 10 and 14 million fish since the mid 1980s, which may seem strange to those who remember the fantastic fishing of the mid-1980s and the crash of Chinook salmon fishing that followed when bacterial kidney disease (BKD) hit in the late 1980s. It was not the number of all salmon that crashed, though. It was only the number of older salmon that decreased because most young fish did not survive to maturity. Age-3 Chinook abundance dropped from over 1.3 million in 1986 to under 200,000 by 1993. Since then, the number of age-3 Chinooks has been increasing gradually with wide fluctuations from year to year.
One of the strengths of the Lake Michigan sport fishery is the diversity of salmon and trout species present. During years when older Chinook salmon are not abundant, anglers have been able to target other species. This diversity is important to the health and resilience of the Lake Michigan ecosystem, as well. Maintaining an appropriate balance between predators and non-native prey fish is crucial to minimize the risk of major problems including disease outbreaks, massive die-offs of prey fish, and negative impacts to native species.
With so many mouths to feed, it also may come as a surprise that the total amount of prey fish consumed has been fairly consistent from year to year. Model estimates put annual consumption by all trout and salmon predators between 155 and 226 million pounds since the mid-1980s. Alewife have been the most important source of food, with smelt and other prey fish accounting for less than 30% of food consumed annually by salmon and trout since 1986. One of the questions that remain is whether prey fish can continue to meet this demand as exotic quagga mussels continue to impact the lowest links of the food chain.
For videos with additional information on salmon and trout fisheries in Lake Michigan, visit the Michigan Sea Grant website.