According to Blank:
The International Seafood Sustainability Foundation’s (ISSF) new Status of the Stocks rating report downgraded Pacific bigeye tuna stocks from a “green” rating — signifying the stock is healthy — to “orange,” meaning the stocks are overfished.
“This year, the stock assessments for both Pacific stocks of bigeye tuna (eastern Pacific and western and central Pacific) showed that the abundance has fallen below the level that would correspond to maximum sustainable yield (MSY),” Victor Restrepo (pictured), VP of science for ISSF, told SeafoodSource. The Pacific bigeye stocks became overfished in 2012 or 2013, he added.
“The reason they became overfished is simply because the exploitation rate is too high. Depending on their natural rates of mortality, growth and reproduction, fish stocks have turnover rates that allow them to replace the biomass lost to fishing, up to a point,” he said.
As a result, catches of Pacific bigeye tuna need to be reduced “to a level commensurate with their turnover capability,” Restrepo said. “This may be hard to do politically, but in concept it is pretty simple. Fishing needs to be managed.”
In addition to Pacific bigeye tuna, 39 percent of all global tuna stocks are overfished, ISSF found, while 52 percent of the all tuna stocks are at a healthy level of abundance, and 9 percent are at an “intermediate level.”
In addition, 17.4 percent of global tuna stocks are being overfished, while 43.5 percent of the stocks are experiencing a low fishing mortality rate, and 39 percent have a high fishing mortality that is being managed adequately, according to ISSF.
“The high rate of overfishing ultimately has to do with too much fishing capacity in the ocean. There are more vessels than are needed to exploit these stocks at the MSY level,” Restrepo said. “On top of that, the decision-making mechanisms at the regional fisheries management organizations (RFMOs) that manage the stocks tend to be consensus-driven. They are slow, and tend to build in many exemptions and loopholes that make them less effective than they could be.”
Meanwhile, the percentage of the global tuna catch that comes from healthy stocks declined from 91 percent to 86 percent since ISSF’s last report in April 2014.
“When viewed from the point of view of total catch, 86 percent of the catch comes from healthy stocks. This is due to the fact that skipjack stocks contribute more than one half of the global catch of tunas, and they are all in a healthy situation,” according to an ISSF statement.
“In contrast, most bluefin stocks and two out of six albacore stocks are overfished, but combined they make a relatively small fraction of the total catch.”