What Kind of Fish Is That?
Lake Michigan Fish Identification 101 

Harbor Angler Report, September 20th Photo

"What the heck is that?" " "I am not sure. I thought it was a Chinook?" Paul and I were scrutinizing a silvery mass of fish flesh flopping in the net at our feet. "Sure ain't no steelhead" "Could be a Coho, I guess, or maybe an Atlantic. I've heard they planted some of them." You would think that fish identification would not be so difficult for two fairly experienced anglers.  After all, between Paul and me we have caught well over 40,000 fish. That's not bragging, just the facts. I myself have a record of twenty thousand fish I’ve caught including when, where and on what lure. Add to that the fish I have not recorded and it's well over that number. Paul, I am confident, has caught at least that many. Add to this the fish we have witnessed caught and fish we have seen in the water while staring hours at the game fish aquaria at Bass Pro or Cabelas, and I think it is safe to say that between us we have observed several hundred thousand live fish of perhaps a hundred or more different species.  So we know our fish. Yet, here was a fish caught in our home waters and we were not sure what it was.

Differentiating between the various salmonoids species found in the Great Lakes can be tricky.  So much so that the Wisconsin DNR does not even expect anglers to do it. For the purposes of bag limit, you don't even need to know whether the fish you caught was a Rainbow or Brown trout, Chinook or Coho salmon. You just need to know it's not a carp or something. You can keep five "Salmon or Trout" in aggregate which means five total no matter what species. The exception is Lake Trout, which are in need of special regulations and are pretty easy to identify anyway with their wormy markings all over the back. This seems pretty insulting to the intelligence and ability of state anglers. After all, duck hunters are not only expected to differentiate between the myriad of waterfowl species they often have to determine the sex. Tough to tell the difference between a male and female rainbow trout without cutting it open. And duck hunters have to make their identifications beforethey harvest their quarry with the bird cruising by at dizzying speeds in low light conditions. The penalties for making an error are pretty severe. You'd think anglers could be expected to know what kind of fish they caught when it is lying in the net six inches from their nose. Apparently not. One of the higher sources of mortality of young muskies is due to anglers keeping them thinking they are northern pike. I have never seen a muskie that looked much like a northern, except for the basic shape. Get a clue guys.

Now some Great Lakes species are pretty easy to identify and differentiate. It's simple to distinguish between a goby and a yellow perch. One tastes better. Even similar species, like the largemouth bass and the smallmouth bass are straightforward to segregate. (Hint: One of them has a smaller mouth than the other.) Some decisions are harder to make, like between a walleye and the closely related and more rare sauger. (Look for the white tip on the bottom of the caudal fin of the walleye and the spots on the dorsal fin of the sauger.) Even Great Lakes salmonoids can be easily identified at some times of the year. Spawning hormones often cause physical changes in fish. A dark colored male 4-year old Chinook salmon with its protruding hooked jaw is hard to confuse with anything else. Brown trout take on bright orange and tan colors during the Spring runs. The characteristic rose colors of Rainbow trout are most prominent when they are on the reds in Hines or Reibolts Creek. However, you put these same fish into the homogenous waters of Lake Michigan with the same light conditions, same water chemistry, similar forage and they all start to look pretty much alike.

That's the problem Paul and I faced now. Sometimes you can get a clue of the species of trout or salmon before it ever gets to the boat. If you see a fish repeatedly performing acrobatic leaps at the end of a long line several hundred feet behind a planer board, take it to the bank, you've hook a steelhead. If a fish hits a fly behind a downrigger ball and rips off a hundred feet of line before you get the rod out of the holder, you can bet you've tied into a big King. A fish that feels like a log and wants to stay on the bottom, lake trout. But fish are individuals and sometimes they act out of the box. I have had rainbows head to the bottom and salmon do aerials.

So how do you differentiate between Chinook, Coho or Atlantic salmon? Between a Rainbow and Brown trout? If you really need to know for sure, you can pull out your Becker's Fishes of Wisconsin, turn to the taxonomic key section at the front of the book and start counting the rays on the anal fins. Chinook have 15-17; Coho 13-15. So what if you count 15? If you were enmeshed in a legal issue, as has happened in some big fishing tournaments, the only way to know for sure would be with a DNA analysis. This can be pretty expensive unless you can find some university grad student willing to do it as part of their research. But seriously, we are talking field identification here. I don't want rocket science; I just want to know what kind of fish we have in the net. The Wisconsin DNR has a site to help anglers make this determination. I like the Michigan DNR site a little better. It is a good idea to take a look at these sites before you head out for a day trolling on Lake Michigan. So, bottom line, how do I make my identifications? First let's take the trout. As I mentioned before, Lake trout are pretty easy, they have wormy markings on a steel blue body and a white belly. Brown trout have a distinctive and pronounced square tail. The spots on their sides will be surrounded by light colored circles. In the lake Browns often do not have much color, but sometimes the spots will be orange or red. Rainbow trout or steelhead caught in the lake usually have no rainbow colors. They have a steel colored back with dark spots and light sides and belly. Most importantly, the inside of a rainbow’s mouth is all white. I won't even talk Brook Trout. It has been several decades since I caught one of those in Baileys Harbor.

As for the salmon species, the biggest call is between the Chinook and the Coho. Both are silvery with black spots. The Chinook will have black spots over the entire caudal fin (aka tail) while Coho have smaller spots on only the upper half of the tail. Again, the inside of the mouth is key. The inside of a Chinook salmon's mouth is all black. A Coho's mouth will have a lighter colored (gray or white) region between the darker jaw and the black interior of the mouth. Sometimes this can be subtle, but usually you can see the difference. Atlantic Salmon are a fairly rare catch, but if you have a fish that you think might to an Atlantic look for a pronounced forked tail with no spots. An Atlantic salmon also has a much smaller anal fin than a Chinook or Coho with only 9 rays. I'd love to catch one some day.

So what do we have in the net today? Below you can see pictures of the inside of the mouth of the fish in question along with another fish we caught earlier. This fish had distinctive light colored gums and spots only on the top half of the tail. We had boated a Coho salmon. Catching a Coho this far north is unusual. They are much more common in the shallower and warmer basin of southern Lake Michigan. They are the target species for trollers around Chicago and Milwaukee. However, later in the summer, Cohos migrate northward looking for cooler water and baitfish to eat. Since there are not as many anglers out on the lake this time of year (Ours was the only boat in sight this night.), not many Coho are reported out of Baileys Harbor.

In fact we have boated a couple of Coho's this month along with a few Chinook and rainbows. There is still forage in the lake and if there is food the predators will be around. The surface temperatures have remained warm in the low 70°Fs and high 60°Fs. Temperatures 60 to100 feet down have ranged form 55°F to 45°F. We have caught most of our fish in 300-350 FOW. Of course, this will change as the sun gets lower in the sky and the temperatures cool and, but there are still fish out there to be caught and will be into the Fall. Get off your butt and get out there.


Tight Lines, Bruce

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