He's not listed in the "Tours" Section of trip advisor for Tobago, but I can't recommend Peter Cox strongly enough. My wife and I went on three tours with Mr. Cox during our week-long stay in Tobago, and overall the experience was exceptional. Mr. Cox is very knowledgable and professional. The tours are well-planned and executed. He also went well above and beyond the call of duty by helping to sort out some travel difficulties we were having.
If you are looking for expert and professional nature tours (birdwatching, night safari in the rainforest, island tour, etc.), I recommend Mr. Cox very highly. He can be found online at http://www.tobagonaturetours.com