CMTM is correct. Sea otters are much more expensive to keep because of their diet. On the bright side, one of the keepers who worked with the sea otters at the Rotterdam Zoo back when they temporarily housed them wrote: "They are wonderfully intelligent animals and I have always enjoyed working with them." He also posted a photo of him nuzzling one of the otters during a training session, though I'm not sure if I have permission to re-post it.
A well-designed pinniped exhibit could possibly be repurposed for sea otters. That's what the Detroit Zoo did.
Interestingly, I've been told that at the recent sea otter conference in Seattle (perhaps
@Northwest_FIsh_Keeping might know more?), the AZA is thinking about removing its ban on sea otter breeding because more facilities would like to have sea otters, but there aren't enough rescued pups to fulfill the demand. If the ban is lifted, I would consider it a positive development because not only would it give many more people the opportunity to appreciate this wonderful species, but it would also make more facilities ready to accommodate rescues in the event of an emergency (the recent lithium-ion battery fires at Moss Landing, not too far from where many wild sea otters live, has me alarmed, as do recent political developments).
Even with a breeding program, I would not expect the captive sea otter population to rapidly explode since they only have one pup at a time (whereas river otters tend to have a litter of pups) and the mothers invest at least six months raising it. The more likely scenario is that an increasing number of AZA facilities house two or three otters while leaving space available for potential rescues/transfers.
Perhaps some of them could be sent to Europe as well. It's remarkable that no German zoo has ever kept sea otters. Nevertheless, the trends show that the species is popular and charismatic enough to justify the prohibitive expenses of their diet.
