Toyota sales slipped 2.4% on a daily basis in April, with almost all hybrid models posting declines, victims of low inventories or aging designs.

“Certainly, we’re feeling it with (the) Prius, where the interruption in (Japan) production and increase in demand (due to high gas prices) leaves us with about 10 days’ supply,” Bob Carter, group vice president and general manager-Toyota Div. for Toyota Motor Sales U.S.A., tells media in a conference call.

However, Carter notes Prius inventory levels have been even tighter at times and says dealers should be able to deliver cars to buyers within two weeks after orders are placed.

Prius production resumed in Japan in late March, albeit at 50% of capacity, after being down for two weeks following the March 11 earthquake and tsunami.

April was the first month Prius recorded a sales decline from year-ago since October 2010, when deliveries slipped 9.9%, Ward’s data shows. Prius volume totaled 12,477 units in April, down 4.3% on a daily basis.

Also dropping below like-2010 levels were Toyota’s small cars, the Yaris subcompact (-50.5%) and Corolla (-13.4%) compact, bucking the industry-wide growth trend in both segments during the month.

Carter and other Toyota officials blame production problems in Japan for the Corolla’s downturn. Some 40% of Corollas sold in the U.S. are imported from Japan.

Despite the dip in Toyota-brand small-car sales, all Scion models registered April upticks, placing the brand 53.7% ahead of like-2010.

Other bright spots included the Camry, posting a 7.6% increase; the Sienna minivan, up 27.0%; and the non-hybrid Highlander, gaining 29.4%. These models will see low financing or lease rates in May, as Toyota continues its “No.1 for a Reason” marketing campaign.

Taking the biggest tumble of any hybrid, or any Toyota or Lexus model, was the typically low-selling Lexus HS 250h. Deliveries fell 75%, with just 279 units sold.

Despite starting the month with less than three days’ supply, Lexus’ new dedicated hybrid, the CT 200h hatchback, managed to triple that volume, racking up 875 deliveries in April.

The HS, CT and RX 450h cross/utility vehicle, now have less than 10 days’ supply, combined, says Mark Templin, Lexus group vice president and general manager.

Because Lexus imports all of its models except the RX 350 from Japan, Templin expects volume for the brand to fall below year-ago levels in May and June.

Carter says age is playing a role when it comes to declining demand for other Toyota hybrids, including the Toyota Camry (down 35.4%) and Highlander (off 47.1%), both late in their lifecycles. The Camry Hybrid debuted in early 2006, while the Highlander was released in 2007.

Toyota had forecast a double-digit percentage gain in overall light-vehicle sales this year, but so far volume is up just 9.3%.

Carter won’t go out on a limb and project sales for 2011, but he calls the Toyota-brand’s 47-day supply “surprisingly good,” albeit down from 55 days’ in early April. Many model lines have greater availability than they did at this time last year, he notes.