Is there a general rule for hook size to fish size/weight?
I like the question…
but…
wait for the midge fisherman to weigh in :roll:
the biggest range of which I know is a small bluegill taking a #6 fly and a ten pound steelhead taking a #18 nymph. I guess the “rules” fall in there somewhere. 
YES!
There is a definitive rule, provided what you are after is a better chance of solidly hooking and landing the fish.
ALWAYS use the largest hook/fly that you can and still catch the requisite number of fish you want.
Same with tippet strength. Always use the heaviest tippet you can and still catch the amount of fish you want.
(Of course, fly size has a direct relationship to the tippet size.)
This goes out the window, though, if you bring ‘preference’ into it. Some folks ‘prefer’ to fish with smaller flies and lighter lines.
Good Luck!
Buddy
TyroneFlyfish
Yup, here’s the rule:
length in inches/67.3571= shank length
Sorry, couldn’t resist… As you know, a bigger hook allows for a wider hook gap for better hooking, stronger wire for holding and a bigger eye to allow heavier tippet, increasing your chances of landing a bigger fish (provided the hook will fit in its mouth).
But in most cases the challenge is to get a fish to strike in the first place, so it’s more about matching hook size to the size of the “bait” you’re trying to imitate to get a fish to strike.
Same stream, fishing over the same fish, you might throw every thing from a small midge on a 24 hook to a size 2 streamer depending on what they are feeding on or other conditions, not fish size.
You can also increase you chances by switching hook STYLE too. Some examples I use:
Short shank hook in a larger size instead of the standard pattern for streamers to get a wider gap and heavier wire.
TUE midge hooks to improve the hook set in anything below size 20
Using a Griffths Gnat in size 14 or 16 (which imitates a cluster of midges) instead of a single size 24 or 26 midge pattern for heavier wire, bigger gap and better visibility.
Using a 4xl size 12 dry fly hook for Eastern Green Drakes instead of the “standard” size 8 to narrow the gap and have a lighter wire (to float it better).
Hope this helps. If you have a specific situation in mind and describe it, I’m sure you’ll get a lot of suggestions.
Best regards,
Peregrines
Common sense prevails but no matter how hard I try; those dang 20" trout keep goin’ after my size 24 midge pupas.
I guess they don’t know the rule either.
I’ve had a 3" rainbow take my #12 caddis. That’s like going to a restaurant in TX and having a 60oz porterhouse-signing your name on the honor board then asking why you didn’t get a baked potatoes and rolls.
Its easy, Quote “Fish em small catch them all.” (linemender)
I start out with a #10, and go smaller and smaller till I find out the size thats working best.
Smaller almost always works better. IMO
Hook size and type not only effect fly size but how it swims too. The same size fly can be tied on different size hooks to change its swimming characteristics. I fish a lot of streamers and vary the hook sizes with similar size flies to change how the streamers sink and swim.
Hook size has to be thought of while setting hooks and fighting fish. When I hook a fish on a size six or ten (which is small for my quarry) compared to a 3/0 or 4/0 I need to remember that chances are the small hook isn’t set into the cartilage of the fish’s mouth like a 3/0 would be. I tend to horse fish a bit less with the smaller hooks because I have had more pull out that I initially hooked than with the larger hooks.
Any fish can be caught any any hook as long as the anglers knows what he is doing, bit of luck helps too.
Just to get this straight… all I have to do is accurately predict the size of the fish I am going to catch, and then pick a hook size accordingly. Hmmmmmmm… now there’s a new wrinkle on matching the hatch…
It does make for a more challenging time on the water.
I guess this is a chance to try my general hook size rule based on the cold water/warm water differentiation of fly fishing by quarry. The simple rule is Warm Water (panfish bass, pike…)= size 10 or larger; Cold Water (trout, trout, trout…)= size 10 or smaller. This is a practical rule for me because I figure if I go out for trout I will take everything I have that is 10 or smaller and a few larger flies to fish evenings and nights for the canibals. For Bass and Panfish, I will take all the bigger flies and throw in a few teenies in case the gills get fussy.
This is also a sweetwater rule. Sea run and saltwater fish or their transplanted descendants fall outside the scope.