First of all you have to define what you mean. If you take the average lifespan of all fish caught for eventual sale to hobbyists then the average would be shorter due to the number which would die before reaching the hobbyist's aquarium. If you restrict it to those which are inside and acclimated to an aquarium then I would assume a shorter lifespan would be due to aquarium conditions such as tank size, water quality, food quality, and stocking density being far inferior to what is available in the wild. In addition, you have errors and accidents in our systems such as malfunctioning heaters, electricity outages, salinity misadjustments, amonia spikes and so on. The only major advantage the captive animal has is lack of direct predation. My opinion.
[ August 06, 2001: Message edited by: 2poor2reef ]