I'm not convinced that any man-made bait can specifically target one species and one species only.
You are probably right there Peter, I think its more a matter of the flavour profile (and correct presentation) preferred by a particular species that catches them on a given day/venue, irrespective of being HNV or not.
I think its also true that most will and do eat anything at some point or other given the "correct/preferred flavour" (factoring in all the many variables). But there is little doubt these days that a bait consisting of higher quality ingredients will out-perform others in the long run and least likely to blow.
Specimen fish (big old ones especially), are definitely old enough and wise enough for example to avoid artificial flavours and additives and will actively and selectively seek out, (given the choice), those baits with a higher amino acid profile.
Thanks guys.
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There are plenty of folks using HNV baits for barbel and catching their fair share of chub and bream. There are also plenty of carpers catching more than their share of "nuisance" tench and bream.
Last season I was targeting 1 of 3 known catfish in a lake using raw liver in stocking mesh on a size 4 hook while my colleague was targeting carp using a HNV boilie on a hair.
Result was that he caught a cat of some 32lb using the boilie and I caught a decent but disappointing 16lb common!