Yellowfin :: Atlantic Ocean
| Ratings for AO Yellowfin tuna | ||
|---|---|---|
| Stock abundance |  |
B < BMSY in 2010. Recent trends in spawning biomass are uncertain because the two assessment models used give conflicting results (one increasing and one declining). |
| Fishing mortality |  |
F < FMSY. Although the point estimate of current F is below FMSY (and thus it could be rated Green), it is highly unlikely that increased fishing effort will result in significantly increased sustained catches, but it will significantly reduce spawning biomass. |
| Environment (Bycatch) |  |
50% of the catch is made with purse seining on free schools, with little impact on non-target species |
|
20% of the catch is made by longlining. Several mitigation measures are in place (sharks, turtles, sea birds). Monitoring is deficient. | |
|
11% of the catch is made by pole-and-line fishing, with unknown impacts on baitfish stocks. Some of the baitboats in the Gulf of Guinea fish together with the purse seiners, thus becoming like a single fleet. | |
|
13% of the catch is made by purse seining on floating objects (including FADs). Several bycatch mitigation measures are in place (turtles, sharks). | |
Note of changes with respect to the May 2011 ISSF Stock Status Report: The stock abundance rating changed from Yellow to Orange. The Yellow rating had been given on the basis that spawning biomass was below BMSY but was estimated to be increasing. The 2011 assessment indicates that biomass, still below BMSY, could be either increasing or decreasing, depending on the model used. While F is below FMSY and at the current level of catch the stock biomass would be expected to increase, the Orange rating is given precautionarily due to the conflicting results.
For detailed information behind the rankings, click here.
Yellowfin catches in 2010 were about 107,900 tonnes, an 8% decrease from 2009. The main fishing gear is purse seining (about 63% of the catch). Purse seine catches have shown a general decrease since the early 1990s, with a slight increase during the past three years.
Stock assessment
The most recent full assessment of yellowfin tuna was carried out by SCRS in 2011. The SCRS advice is based on averaging the results from two types of models. These results are somewhat more pessimistic than those of the previous (2007) assessment and indicate that:
- The (2010) ratio of Fcurrent/FMSY is estimated at 0.87 (range 0.68-1.40), indicating that overfishing is not occurring.
- The (2010) ratio of spawning biomass Bcurrent/BMSY is estimated at 0.85 (range 0.61-1.12). This indicates that that the stock in 2006 is in an overfished state. However, the SCRS notes that the two types of models used show conflicting trends in the last few years: An increasing trend in biomass with one model, and a decreasing one with the other.
- The estimate of MSY is 144,600 tonnes (range 114,200-155,100). MSY is lower than in previous decades because the overall fishery selectivity has shifted towards smaller yellowfin, mainly through fishing on FADs.
Management measures
Recommendation 93-04 requires ICCAT members to not allow the effective fishing effort exerted by their fleets to exceed the 1992 level. “Effective fishing effort” is a variable that may be difficult to manage through time, because fishing technology and fishing know-how change all of the time. However, as inferred from fishing mortality estimates from the most recent assessment, effective effort in 2010 appeared to be about the same as the 1992 levels. There is concern that fishing pressure on the stock could increase in the near future with the recent movement of purse seine and longline vessels from the IO into the AO due to piracy. This situation should be monitored closely.
The time-area closure established for bigeye through Recommendation 10-01 also affects yellowfin.
In 2011, the SCRS made projections that suggest that if the current catch level of about 110,000 tonnes continues, the stock will rebuild to BMSY by 2016. SCRS also recommended that effective measures be found to reduce FAD-related and other fishing mortality of small yellowfin.
Summary
| QUANTITY | ESTIMATE | YEARS | Notes |
|---|---|---|---|
| Most recent catch (t) | 108 | 2010 | |
| Five-year average catch (t) | 108 | 2006-2010 | |
| MSY (t) | 131-147 | 2006 | |
| F/FMSY | 0.86 | 2006 | |
| B/BMSY | 0.96 | 2006 | |
| Catch at FMSY (t) | N/A | ||
| TAC (t) | None |
Catches and MSY are in thousand tonnes.
