Well the good news is that I am not here to tell you to throw away all your lists because they are baloney. They are very helpful in pointing you in the right direction and for the most part they serve a great purpose. Unfortunately, I am going to bring to light that they are not the end-all-be-all to making conscientious seafood purchases. They can't be. The fact that these lists are printed prevents them from being so. You see, information changes very quickly. Scientific studies are constantly being done and analysis is continually being reviewed and reassessed. Just recently it was announced that 6 North American fish stocks were considered rebuilt in a 2011 report.
Another issue is that these cards refer to ranking species in a generalized way and do not reflect some of the smaller fisheries and locations where said 'red' species is being harvested in a way that is sustainable. Take domestic red snapper for an example. On every list of green, yellow, and red fish rankings you will always find domestic red snappers in the red. They are on the avoid list everywhere, without exception. This information is an accurate assessment of the 70's and 80's when stocks were being destroyed by recreational and commercial fishermen alike. In 2007 commercial harvest for American red snappers went to an IFQ (Individual Fishing Quota) system. This is a system where each fisherman is allotted a certain number of landed pounds a year, based on their respective historical catch.
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On the other hand if you look at Alaskan Halibut, most lists will consider it to be in the 'green' or a best choice. However, the Alaskan halibut quotas have been cut 30 million pounds (around 50%) in the last two years. This is a result of less and less large fish in the water. How can a fishery be considered a best choice while the fish stocks are continually diminishing? Well the answer is a bit complicated. It is hard managing any species where different class years of fish will raise or drop the number of fish in the water. There are natural fluctuations of all wildlife species, but it is important not to overlook the benefits that awareness and proper fishery management has contributed to worldwide fish stocks. Halibut is a best choice because it is well managed. The slashed quota is a result of proper management. There is much more concern for fish stocks now than in the past and people are paying attention to what we take out of the water and what we leave in.
I am not saying don't buy halibut and do buy snapper. What I would recommend is to mix it up. Don't eat halibut 3 times a week. Mix in some other sustainable seafood. Don't get so engulfed in the cards that you stop listening to updated information. Go to a reliable fish market or restaurant, like BlackSalt, and ask questions. Find out where they are sourcing their products. The answers might surprise you. Don't throw away your index cards by any means, they can be really helpful as a general guide. Just remember to look from them and meet the people who are serving you. They just might have some insight into their products that you won't find on a 3"X5".