Time to fish sac fry on the Lower Sac!
While still a little off-color from the previous winter storms, the Lower Sacramento River is a solid fly fishing option. I was able to get on the water for the better part of this past sunny and warm Sunday afternoon. We launched the driftboat from the Posse Grounds boat launch around 12:30 and after rigging up with some sac fry/alevin patterns were immediately into a few trout after dropping into the riffle water above the Sundial Bridge. While the action wasn’t fast the fishing was fairly consistent with most of the fish landed coming to net with the alevin tucked neatly in the corner of its mouth.
The yolk-sac fry, or alevin is so named due to the egg sac the freshly hatched juvenile salmon still has attached to its body (not the fact that these particular examples coincidentally reside in the upper-cased “Sac”). The tiny fish will absorb the yolk for nutrients while remaining hidden in the gravel it was previously deposited in by its Fall-spawning parents. While these fish don’t yet explore the open water outside their gravelly haven, they do occasionally get washed loose and provide a very tasty morsel for the Sac’s fat rainbows. After several weeks hidden in the gravel the alevin will venture to the surface, gulp some air to fill their swim bladders, and become fully fledged salmon fry. But for now, these defenseless little yolk-laden fish provide an important and easily imitated food source (As the alevin approach hatching-time the eyes develop, creating the dark spots of the “eyed egg” stage, regular egg imitations are still a good bet during this time).
Other than the alevin, the best bets for this time of year are small #16-18 olive colored baetis nymphs, light orange/pink egg patterns to imitate the eggs yet to hatch, and I’d also have a few #14 olive/tan caddis nymphs to imitate the few caddis coming off on warmer days. The baetis nymphs (use a pheasant tail or something similar like the Hogans S&M) particularly like to hatch on overcast days, and in the right conditions can even produce some dry fly fishing. In the few sunny hours we were on the river most our action came on the alevin, with several other hook-ups due to the baetis or caddis dropper we had rigged 16-24″ behind it. Based upon the ready-to-hatch egg we came across it looks like the alevin should provide several more weeks of trout food before they lose the sac. However, towards the end of this time frame keep in mind that after absorbing the yolk these little fish apparently take some time to develop their predator-evasion stamina and skills, as in years past we have had success nymphing little one-inch salmon fry patterns shortly after having success on the alevin.
Click here for some video of hatching salmon