Fish Sampling Frequently Asked Questions (FAQs) - Oceana USA

Fish Sampling Frequently Asked Questions (FAQs)

Q. What are the desiccant beads and what do they do?

A. The desiccant beads are a drying agent. These beads will draw moisture out of your fish sample so that the tissue dries rather than rots. You may use a desiccant right in your own kitchen, such as rice in a salt shaker. The grains of rice absorb moisture and prevent the salt crystals from sticking together. In this case we used silica gel beads (SiO2). Please don’t eat the desiccant. If you do get some on your skin, it may be mildly irritating, so make sure to wash the area with soap and plenty of water.

Q. Why is it important to wash my hands and utensils before handling my fish?

A. We want to make sure that all other fish DNA is removed from the fish sample you submit to us. So the cleaner the materials and hands that touch and prepare the sample are, the better. This is especially important if you prepare another type of fish sample right after you prepare Fish Sample #1. We don’t want any DNA from Fish #1 to get mixed up with the DNA from Fish #2. Otherwise we may not get good DNA results.

Q. Why do you want me to take my fish sample from the middle of my fish serving or fillet?

A. The fish fillet or serving is probably thickest there and is usually less “well done,” if cooked. The DNA in cooked fish is best preserved when exposed to as little heat as possible.

Q. How much fish should I put in the vial?

A. We suggest the size of a small marble. This is the optimal size for getting good DNA for sequencing. This sample size should fit into the vial easily or the desiccant beads will not work.

Q. Why are there 2 vials per fish sample?

A. For each type of fish, or sample, there should be 2 “sub-samples.” Sub-samples are the small marble-sized pieces you cut from the same fish and put into the two vials. One of the vials will be sent from our headquarters to a DNA testing lab so that the DNA can be extracted and sequenced. This sample will tell us what type of fish you actually bought. The second vial will be archived at Oceana as a backup, and may be sequenced later on if needed.

Q. Why is it important to leave my sample at room temperature after I put it in the vials?

A. Cool temperatures slow down the action of drying and preserving the samples. Samples that are frozen after being placed in desiccant may rot during transport through the mail at room temperature. We want the desiccant beads to completely dry the sample at room temperature first.

Q. Why are the barcode number and “sell by” date important?

A. These are used as tracking information within the seafood and retail industries.

Q. What types of observations should I put in the “additional notes” section of the data sheet?

A. You may write any additional observations or anything that doesn’t fit into a specific section. For example, if you left your fish out for 5 hours after purchasing it, you would mention that here. This helps us interpret results when we get them. Also note here if the information on your receipt is different from what you saw at the fish counter or on the menu.

Q. What does Oceana plan on doing with this information?

A. Oceana will analyze your results as part of our efforts to fight seafood fraud. Oceana is also trying to determine where fraud occurs and whether it is more common for particular fish or particular regions.

Q. Why did you choose to target certain species?

A. The species listed in your Welcome letter in the fish testing kit are those that Oceana has identified as prevalent in your area and that are susceptible to fraud.

Q. Can I submit other types of fish to be tested that are not listed in the Welcome letter?

A. Yes. We are most interested in the fish listed in your Welcome letter, but some other fish that might be interesting to collect for seafood fraud include mahi mahi; swordfish; Chilean sea bass; Atlantic or Pacific cod; Dover, lemon or grey sole; and Atlantic halibut. We do ask that at least one of your samples be from the fish listed in the Welcome letter.

Q. Why should I avoid sampling certain types of fish?

A. We are testing for seafood mislabeling. Fish labeled simply “salmon” or “tuna” are hard to substitute with other types of fish due to their color and flavor. Atlantic salmon is nearly always farmed, as are trout, tilapia, basa, tra and swai. These less expensive farmed fish may be substituted for the more expensive wild fish listed in your Welcome letter. We ask you to avoid sampling any fish labeled simply “tuna” or “salmon;” any tilapia, trout, pangasius (basa, tra, swai), Atlantic salmon or farmed salmon.

Q. What if I want to sample more than two fish?

A. Please contact us at with your name and address and we will be happy to send you another kit.

Q. I’ve lost or ruined my data sheet and instructions. Where can I get more?

A. You can download extra copies of the instructions or data sheet.

Q. What is a government inspection label?

A. There are a number of inspection labels that may be on the seafood label, including “Grade A,” “HACCP,” or some other label. You can see examples of some labels here. Whatever label is on the package, please describe it on the data sheet.

Q. Why can’t I sample canned seafood or ceviche?

A. The additives and high temperatures used in processing canned seafood and the acid in ceviche (from the lemon or lime juice) can deform the DNA so that it cannot be sequenced.

Q. I got both of my fish samples from the same place. Do I have to write out all the same purchasing information on both data sheets?

A. No, you do not. Please fill in your vial number and date prepared on the reverse side of the data sheet. For any information that is the same as that recorded on the first side for sample 1, you can write “same.”