I've always felt that the existence of the "Reefers supporting fishing vessels" is kind of a silly category, as in the modern era, a significant portion of the vessels with that job description are just standard reefer vessels with no designed connection to fishing, only a contract to support the industry for a short or long term.
Instead, it seems to me that the category would be better served by relocating any "typical" reefers to the normal reefer categories, and re-establishing it as a "Fish Factory Vessels and Tenders" or "Fishing Tenders and Motherships" category, which would encompass two relatively prevalent varieties of vessel:
1. Fish Factories: Specially-designed or modified vessels intended to serve as a "mothership," receiving fish from catcher vessels, processing it for long-term storage, and either transferring the processed fish to reefer vessels, or keeping it in a dedicated hold until returning to port. (Not to be confused with "catcher-processers," vessels that process the fish they catch, which are best left in the standard catcher categories.)
Example: OCEAN PHOENIX (http://www.shipspotting.com/gallery/photo.php?lid=2139124
2. Fishing Tenders: Vessels with no catch gear of their own, but working solely in support of fishery operations through a combination of delivering supplies to catcher vessels and factory ships, and ferrying fish between any combination of catcher vessels, factory ships, and shore-based processing plants. In some cases, these vessels may also carry their own small-scale processing gear.
Example: DOROTHEA (http://www.shipspotting.com/gallery/photo.php?lid=2657173
I feel that such a rearrangement would easily cover at least 95% of the non-catcher vessels currently found within the site's fishing categories in a much more straightforward and clear organization. Relocating any remaining fisheries research or patrol vessels to the respective Survey and Law Enforcement categories, and any small utility boats to the Workboat category would likely account for a significant portion of the remainder.