A marine mammals expert has urged against culling New Zealand fur seals on South Australia's Kangaroo Island despite concerns their rising numbers are causing problems for the local fishing industry.

Peter Shaughnessy from the South Australian museum is about to head to the island to conduct the annual survey of the seal population.

After being heavily hunted in the 19th century, seal numbers have been growing steadily in recent years.

There are now several thousand in two main colonies, prompting tuna operators to seek permission to kill some.

Dr Shaughnessy said a cull was unnecessary with natural factors likely to limit future growth in the seal population.

"There will be limiting factors," he said.

"Either they'll run out of space or they'll get to the limit of their food."

Dr Shaughnessy said a cull would also impact adversely on the local tourism industry.