Published: Sat, January 21, 2017
World | By Tasha Manning

Thunnus orientalis (Pacific Bluefin Tuna)

Thunnus orientalis (Pacific Bluefin Tuna)

The International Scientific Committee for Tuna and Tuna-like Species in the North Pacific Ocean (ISC) is responsible for conducting regular stock assessments.

Summary of Stock Status For the Pacific Bluefin Tuna. The ISC created the Pacific Bluefin Tuna Working Group (PBFWG) in 1996 with the task to assemble, conduct and analyze fisheries statistics, biological studies and stock assessments for Pacific Bluefin Tuna. The West and Central Pacific Fisheries Commission (WCPFC) and the Inter-Tropical Tuna Commission (IATTC) are jointly in charge of the management of Pacific Bluefin Tuna, and use the ISC stock assessment assessment and advice to establish conservation and management measures. P>

In addition, there have been some concerns about the ISC stock assessment for Pacific Bluefin Tuna because the models do not adequately fit the data (Maunder et al , 2014). However, sensitivity analysis in the ISC models are robust to the general conclusions that the SSB is very depleted and overfishing is occurring (ISC 2014). An external analysis supported by the ISC stock assessment model for Pacific Bluefin Tuna, confirming that the species urgently needs new management action to ensure its sustainability (Maunder et al , 2014). The current high fishing mortality rates, including taking juveniles, may not allow any new cohort to enter the spawning biomass. Substantial immediate cuts in fishing mortality of juveniles are needed to ensure the viability of the Pacific Bluefin Tuna, in addition to protection of spawning adults, at least until reductions in fishing mortality of juveniles allow for incorporation of new spawners (Maunder et al . 2014, ISC 2014).

Summary of Population data and stock indicators based on the 2014 ISC Stock Assessment
Catch trends:
Tuna for several centuries in the western Pacific and at least since the beginning of the 20th century in the eastern Pacific. Data prior to 1952 is of relatively poor quality and therefore fisheries date only from 1952 to 2012 is included in the latest stock assessment (ISC 2014). Since the 1950s, catches of Pacific Bluefin Tuna have fluctuated substantially over time and by gear time. The maximum historical catch occurred in 1956 with 39,824 t and the lowest historical catch occurred in 1990 with 8,588 t. During the last 10 years, the average catch has been 21,250 t, with most of the catch (80%) occurring in the western Pacific. Since the 1950s, the catches have been predominantly composed of juveniles, and since the 1990s, the catch of age has increased significantly.

What's the right response to code-switching? | Teaching For Biliteracy
I never realized that they were speaking their home language, Nahuatl, but I knew that was part of their identity. Gabriela Puente is a bilingual resource teacher at Chavez Elementary in Madison Metropolitan School District.

Spawning stock biomass (SSB) trends: Based On the 2014 stock assessment base case model, since 1952 the SSB of Pacific Bluefin Tuna has fluctuated substantially over time. The first year of the assessment, in 1952, the SSB was ~ 90,000 t. Estimates of SSB peaked at ~ 140,000 t in 1961, declined to ~ 24,000 in 1974, climbed back to ~ 50,000 t in 1978, declined again to ~ 18,000t in 1984, climbed back to ~ 87,000 in the 1995 and have fallen to About ~ 26,000 in 2012. It is estimated that the SSB in 2012 is approximately 4% of the stock's estimated unfolded SSB levels.

Fishing mortality trends: From 1952 to 2014, the average fishing mortality for juvenile ages (0-3 ages) of Pacific Bluefin Tuna was higher than for adult ages (age 4+ fish). The most recent fishing mortality rates for ages 0-6 for the years (2009-2001) show an increase of 19% (Age 0), 4%, (Age 1), 12% (Age 2), 31% ), 60% (Age 4), 51% (Age 5) and 21% (Age 6) in relation to fishing mortality rates for ages 0-4 in the years 2002-2004. The year 2002-2004 is the reference year for the most current WCPFC conservation and management measures in place.

Stock status determination: The WCPFC and IATTC, the two RFMOs in charge of managing the Pacific Bluefin Tuna. Yet the ISC estimated several target and limit reference points commonly used by fisheries managers to determine the status of the stock. The SSB in 2014 relative to the unfolded SSB is less than 6%. Moreover, the ratio of current fishing mortality rates (2009-2011) relative to all biological reference points indicates that current fishing mortality rate exceeds all target and limit biological reference points (Fmax, F0.1, Fmed, F10%, F20%, F30 % And F40%), except for Floss.

Future projections: The large majority of projections under different harvest scenarios and low recruitment scenarios estimate the low probability Of SSB SSB benchmarks of 10% of unfished SSB (SSFf = 0) within 10 years. Given recent average recruitment levels (2009-2013) may be lower than that observed before 2009, the WGPBF highlights the importance of considering the projections with low recruitment scenarios.

Like this: