Semi-Selectivity
Opportunistic feed is when fish literally eat whatever the opportunity provides. This is often the situation during periods between hatches. Selective feeding occurs whenever there is a super-abundance of one food type—such as occurs during a hatch. Then there is Semi-Selectivity. This is a type of opportunistic feeding during which fish feed preferentially on organisms that they see frequently rather than on organisms that are not as prevalent. For example, a lake is loaded with scuds and has only a marginal number of Callibaetis mayfly nymphs and caddis species. If the fish sees a scud, a nymph, and a caddis larva, it will more likely take the scud. If it sees only the nymph and/or larva, then it well eat them.
This Semi-Selectivity is to be expected because the fish is exposed to scuds more frequently than other food organisms. And while not entrained on scuds to the level of absolute selectivity (such as a trout feeding exclusively on Baetis emergers), the trout certainly recognize scuds as tasty tidbits more readily than they recognize other food items.
Our friend, Theo Bakelaar, of Holland, fishes a large, brackish lake that contains large rainbows. Often, in the part, Theo would fish hard all day for a strike or two. Then, on his last trip, he noticed an abundance of scuds, collected some and tied imitations. His success was immediate—during the day.
Toward evening, the fish moved into deeper water near the dams and hammered the baitfish. Then Theo switched to his Eelskin minnow imitations, and in turn, hammered the trout.
Pay attention to the prevalent food organisms in the waters you fish by day/month/year and by the time of day. It will greatly increase you chances of taking fish.
The scuds Theo found were olive colored–note the orange egg sack in the center of each scud.
Many scuds are rather small, sizes 10 to 18. Heavy wire hooks not only help the flies to get down a bit, but there’s far less chance they will straighten when fighting a big fish.
Trout feeding on scuds get very heavy, very quickly. Note the girth of this scud eater.
When going for these big fish, use the heaviest tippet that they will accept the fly on. You’ll need it if the fish gets in the weeds.
One of the best ways to fish scuds is with the Strip/Tease Retrieve. Strip slowly and simultaneously jiggle the rod tip back an forth a few inches., The fly fill move in a jerky manner very similar to that of the natural.
The fluorescent orange egg sack is a very important feature in the imitation.
Fish may focus on different organisms at different times of the day. Toward evening, the fish in the Lake Theo was fishing switched from scuds to minnows.
Big fish require big food organisms to sustain their calorie requirements, and will pound minnows when they are available.
Theo’s Eelskni Minnow is a great imitation when the fish are eating baitfish.