I have studied several different species of fish. For some years now I have studied asp. During the past week I was fishing for asp as well as studying them several hours every day.
The water I was fishing last week offered me:
High fishing pressure for 2 decades = all bigger asp knew, that they had to be picky.
Relatively clear water = asp may see the leader, or me, or any slight details mismatching their food.
No moving water (no current) = much time for checking my flies.
Large schools of baitfish = not much (if any) willing to take a lonely moving baitfish.
Fixed on eating bigger baitfish (ide) 8 - 9cm = bigger flies needed = making it easier to realize differencies in smell and movement compared to real bait.
A lot of asp refused to take my flies, but were running at them.
In order to find the cause I tested a lot and finally ended up testing the asp their reaction to a real (dead) baitfish. I covered one (dead) baitfish under a full UV coat in order to block his smell.
80 casts with a fly = no strike. 8 casts with the real baitfish = 4 takes (1 Zander, 1 Ide, 2 Asp). 25 casts with the covered baitfish = zero takes.
I am sure, that many species of fish use their sense of smell to realize the bait (our fly) not to be their bait. This easily becomes a serious problem for us, IF we want to catch the fish by imitating his bait in the way his bait behaves!
We can of course make it hard for the fish to smell.
This for example can be done by:
Highest retrieving speed.
Putting the fly very close to the fish when the fish for example is hammering into a school of bait fish and not yet have gotten one.
Fishing fast current forcing the fish to act fast.
Using the tiniest flies coming along with less intense (wrong) smell imitating something smelling less intense compared to bigger bait either.
Provoking agressivity by using flies being very big (in relation to fish size) and or full of action.
I believe we always use scent on our flies anyway. Only mostly we know nothing about how that scent turns the fish on or off!
On fly only waters flavors are usually forbidden. But of course tying flies with all natural materials all including their own scent is allowed even if the smell triggers fish perfectly!
I have no doubt, that one day we will have proper flavors in all our fly fishing shops! Since we want to be great in imitating natural bait, this will only be logic, especially when aiming for those species of fish using their sense of smell a lot.
Using flavors still means to have lots of challenges left. Finding a proper flavour for example is a very big one, because most flavours spook the fish as usually does the intense smell of glue.
I hope I could make you think a little of what really happens below the surface. There is lots to be learnt still! I made quite a good number of underwater videos comparing my flies with the real bait last week.
No need to tell, I again learnt a lot here! Imitating real bait their movements often is pretty damned difficult!
Great week to all of you!
All my best