As you heave it up from the bottom, you see a large fish thrashing about in the net. With one hand holding a scale and the other a tape measure, you’re standing on river bank wondering if it will be your personal best or just another average day.
Banks are still slippery places, scales is cumbersome and batteries can fail. That’s why every angler worth their salt learns to estimate long before relying on that digital readout. Half of what makes a salmon special is length but the remaining half are weight. Weight to length ratio vary by species. A forty-inch Chinook may seem muscle-bound making for a heavier package then a forty-inch Atlantic which may be more elegant. Knowing that distinction make you a person who respects the fish you have caught.
How to Guess Salmon Weight Without a Scale
Here’s how those differences play out on a chart comparing six predominant types of salmon (see chart above). As you can see, the King, or Chinook, salmon is the heavyweights of the Pacific coast. When a Chinook reaches a length of fifty inches, they’re packing some serious girth; they’ll typically hit the scales at forty pounds. In contrast, Sockeye are streamlined and slender. If you hook one that measure twenty-four inches, you’d mentally compare it to a Coho of equal length, expecting it to be twice as heavy, which it won’t be.
And therein lies the rub: Most folks’ estimates aren’t very accurate. The visual scale here points up the difference between how evolution designed different species. A Pink salmon take up far less volume than an equally long Atlantic salmon, which isn’t surprising if you think about it. Inches aren’t everything; it’s also about body shape. That’s where knowing the species marks the difference in trying to make a speedy weight guess.
Coho have spots only on the top lobe of their tail and white gums; Chinook have spots on both tail lobes and black gums. Sockeye has no large spots whatsoever. So once you know what it is, you can tweak your mental calculator, because a lean Coho doesn’t weigh as much as a fat one. Likewise, a trophy (5-year) Chinook is much larger then a jack (1-year return) that spent less time in the ocean. The infographic details those size comparisons with the jacks and grilse too. The weight difference between a juvenile Atlantic salmon and a multi-sea-winter adult isn’t a straight line; it grow exponentially. This is why it helps to look at them side-by-side.
You’re fighting an animal that has increased its growth over many feeding cycles, so it take patience and different tackle to target older fish. No scale? No problem. A basic formula used by anglers for decades will help get an approximation of weight. To figure it out, multiply the length (in inches) times the girth (in inches squared), and divide by 800. Sounds like math class, I know. But after a few attempts, it becomes second nature.
The kicker: measure the girth at the fattest point on the fish, typically right behind the head, and it’ll provide a weight estimate accurate within fifteen percent. If you’re more comfortabley in metric, simply use different divisors and follow the same reasoning. Knowing how big your fish is doesn’t require expensive equipment, only knowledge of the fishs shape.
Now that you know all this about length and weight, you can help conserve fish and manage your expectations. Knowing a 30 inch sockeye would weigh roughly seven pounds, you won’t be upset that it didn’t hit twenty inches. And as far as conserving goes, by releasing a good sized adult chinook, you’re actualy doing more for the system than keeping each and every fish you catch. By seeing how large they can become, you’ll be thankful for those who do come back to spawn.
Remember that number on the tape doesn’t even begin to tell the tale. But the weight shows how much effort went into creating this creature. So go ahead and keep that tape measure handy for the next trophy. Trust your eyes and respect their size.