New Yellowtail Flounder Survey Questions Official Estimates

WASHINGTON (Saving Seafood) – November 19, 2013 – The initial results of a new, independent survey of Georges Bank yellowtail flounder raises questions over whether federal assessments of yellowtail abundance have been systematically underestimating the size of the population. Administered by researchers at the School for Marine Science and Technology (SMAST) at the University of Massachusetts Dartmouth, the two surveys were conducted over several days in April and November. While the results are preliminary, they suggest there may be more yellowtail flounder in Georges Bank than currently assumed by federal stock assessments. A brief summary of the survey’s methods and results is listed below:

The survey was conducted with a video monitor attached to the net to monitor the catch, and utilized two different tow methods. The first was a traditional, half-hour long tow using a closed net, in which the fish were monitored over video and counted after the completion of the tow. The second method was a tow lasting several hours, deploying an open net and using only the video monitor, allowing for the fish to be counted as they passed through the net.

Utilizing the open net video survey method allowed the researchers to tow for longer periods of time and cover a larger area than a traditional tow, while not harming any of the fish sampled. Conducting a longer tow produces a larger set of data to compare with the shorter tows.

The tows took place in Closed Area II of Georges Bank, the same area covered by National Marine Fisheries Service (NMFS) surveys. However, the SMAST survey found more yellowtail flounder in Closed Area II than the NMFS survey. Yellowtail were the most abundant flatfish found in the SMAST survey, with the average short tow pulling in around 250 yellowtail. The average NMFS tow, in contrast, is estimated to have caught around 10-20 yellowtail, based on approximations derived from the total weight of the fish they landed. Even though the surveys use different-sized nets, this is a large discrepancy.

The survey encountered yellowtail at a consistent rate throughout its duration, with the yellowtail relatively evenly distributed over the course of the survey area. The fish caught ranged in size from 20-47 cm.

While the results of the survey are preliminary, they raise questions about the accuracy of the NMFS survey. If discrepancies between the two surveys persist, further questions are likely to arise regarding the validity of previous federal surveys of the Georges Bank yellowtail flounder population.