Museum chief executive Shimrath Paul has long predicted an end to the "honeymoon period" success of the highly popular Tropical Forest, which opened in late 2007 and is home to about 1000 brightly coloured butterflies.
Mr Paul has also predicted a likely eventual return to annual visitor numbers of about 350,000.
Museum attendance figures for the first five months of the 2009-10 financial year, until last November, show an overall attendance of 132,649, down 51% on the 270,732 attracted in the previous, record attendance year.
An estimate partly based on these figures suggests the attendance for the financial year ending on June 30 this year of about 350,000.
Clare Wilson, the museum director, exhibitions, development and planning, emphasises that the museum remains highly popular, offering a series of attractive exhibitions, including the paid-entry "Dinosaur Eggs and Babies" show.
Current figures suggest that annual attendance, until June 30 this year, will remain well above the levels of the 1990s and and also ahead of much of last decade.
Ms Wilson said a likely reduction in the number of repeat visitors to the Otago Museum's Tropical Forest and to the museum and some adverse effects from the world economic downturn had contributed to reduced visitor numbers.
Although the museum offered free general entry, family entry packages for paid shows and generally good value for money, some people who were nervous about their economic circumstances were likely to reduce their activity level generally, she said.
The Otago Museum plans to further investigate its overall attendance figures, generated by its automatic door counter system, because some other museum statistics suggest a lower rate of visitor decline.
For example, visitors to the museum's Discovery World, which includes the Tropical Forest, are down by only 21% from 51,503 to 40,528, and museum shop sales are down 23% over the comparable entry periods.
Attendance at the Dunedin City Council-owned Otago Settlers Museum also fell recently, by about 27%, to 12,818 in the first four months of the latest financial year, from 17,628 in the previous year, according to council figures.
That reduction also came after a year of unusually high attendance, involving more than 66,000 visitors, in the 2008-09 year.
For many years, about 30,000 people visited the museum each year, but numbers have risen since general entry charges were scrapped in 2006.
Settlers museum director Linda Wigley has said the economic downturn may have contributed to the reduced attendance.
The Dunedin Public Art Gallery has also experienced a modest drop in attendance, down about 9% from 108,114 in the first five months of the previous financial year to 98,541, between July 1 last year and January 3 this year.
Gallery director Elizabeth Caldwell emphasised this had come after a record annual attendance, 208,058, in the financial year to June 30 last year.
The small reduction had largely resulted from the success of the earlier Rita Angus and Frances Hodgkins shows in 2008.
Ms Caldwell was pleased with the gallery's "great" attendance figures, which, although below record levels, were still running well ahead of the levels needed to meet this year's 180,000 visitor target.
