Here's an extract from the "Dispose of Waste Properly" section of the Backcountry of Algonquin Park - Leave No Trace Outdoor Skills and Ethics booklet (page 7) ....

http://www.algonquinadventures.com/BackcountryOfAlgonquinParkLNT.pdf

"Cleaning Fish
The waste from fish cleaning should be disposed of in deep water, at a distance from campsites and trails. This practice gives creatures like seagulls and snapping turtles the opportunity to consume the remains. Fish waste should be neither buried nor disposed of on land. Its decomposition gives off considerable odour, which is a strong attractant to bears."

Extending the logic of minimizing food materials and smells away from camp. the actual cleaning process should be done well away from campsites (rocky point or very small island), where liquids can be flushed into the water. Fillets should be put in a plastic container for return to camp for cooking .. and solid waste should be similarly contained and 'deep-sixed' as described above.