Questionnaire Report for Bluefin tuna

(MERA version 4.1.6)

Brett van Poorten ()


1 About this document

This is a prototype of an automatic report that documents how the user specified the operating model and their various justifications.

2 Introduction

  1. Describe the history and current status of the fishery, including fleets, sectors, vessel types and practices/gear by vessel type, landing ports, economics/markets, whether targeted/bycatch, other stocks caught in the fishery. The bluefin tuna fishery is managed as two stocks; separated roughly by the 45th meridian, however genetic analysis and various tagging technologies indicate mixing. The population is targeted and incidentally caught primarily by multiple nations: Canada, Japan, Mexico, USA and Cuba. Vessel types include longline, other surf., purse seine, the sport fishery and traps. The population in the Western Atlantic seems much smaller than the east and was not generally commercially targeted until the early 1960s. Rapid increase in fishing caused catches to rapidly increase and then decline by the 1970s. Stricter regulations were put in place in the 1980s and a rebuilding plan was put in place in 1998. MSY for this population is relatively uncertain, so F0.1 is used as a proxy for FMSY. “The total catch for the West Atlantic peaked at 18,608 t in 1964, mostly due to the Japanese longline fishery for large fish off Brazil (that started in 1962) and the U.S. purse seine fishery for juvenile fish (BFTW- Figure 1). Catches dropped sharply thereafter to slightly above 3,000 t in 1969 with the collapse of the bluefin tuna by-catch longline fishery off Brazil in 1967 and declines in purse seine catches. Catches increased again to average over 5,000 t in the 1970s due to the expansion of the Japanese longline fleet into the northwest Atlantic and Gulf of Mexico and an increase in purse seine effort targeting larger fish for the sashimi market. Catches declined abruptly in 1982 from close to 6,000 t in the late 1970s early 1980s with the imposition of a quota. The total catch for the West Atlantic, including discards, fluctuated without trend after 1982 reaching 3,319 t in 2002 (the highest since 1981, with all three major fishing nations indicating higher catches). Total catch in the West Atlantic subsequently declined steadily to 1,638 t in 2007 and then fluctuated without pronounced trend (BFT-Table 1). The catch in 2015 was 1,842 t, 1,901 in 2016 and 1,851 t in 2017 (BFTW-Figure 1).” (bluefin summary report)

  2. Describe the stock’s ecosystem functions, dependencies, and habitat types. “Atlantic bluefin tuna (BFT) have a wide geographical distribution but mainly live in the temperate pelagic ecosystem of the entire North Atlantic and its adjacent waters, for example the Gulf of Mexico, Gulf of St. Lawrence and the Mediterranean Sea. Historical catch information documented the presence in the south Atlantic however recent information is incomplete (BFT-Figure 1), Archival tagging information confirmed that bluefin tuna can tolerate cold as well as warm water temperatures while maintaining a stable internal body temperature. Bluefin tuna preferentially occupy the surface and subsurface waters of the coastal and open-sea areas, but archival tagging and ultrasonic telemetry data indicate that they frequently dive to depths of more than 1,000 m. Bluefin tuna are a highly migratory species that seems to display a homing behavior and spawning site fidelity to primary spawning areas in both the Mediterranean Sea and Gulf of Mexico. Evidence indicates that spawning has been observed in other areas for example the vicinity of the Slope Sea off the Northeast USA, though their persistence and importance remain to be determined. Electronic tagging is also resolving the movements to the foraging areas within the Mediterranean and the North Atlantic and indicate that bluefin tuna movement patterns vary by tagging site, by month of tagging and according to the age of the fish. The reappearance of bluefin tuna in historical fishing areas (e.g. northern waters and in the Black Sea) suggest that important changes in the spatial dynamics of bluefin tuna may also have resulted from interactions between biological factors, environmental variations and the reduction in fishing effort.” (Stock Assessment summary report.pdf) Bluefin are a top predator and therefore distribute themselves according to the distribution of their prey - in Canada that is primarily herring and mackerel. Recent shifts in prey distribution has pushed Bluefin further north.

  3. Provide all relevant reference materials, such as assessments, research, and other analysis. Bluefin Tuna Detailed Stock Assessment Report.pdf Bluefin Tuna Summary Stock Assessment Report.pdf

3 Fishery Characteristics

3.1 Longevity

Very short-lived (5 < maximum age < 7)
Short-lived (7 < maximum age < 10)
Moderate life span (10 < maximum age < 20)
Moderately long-lived (20 < maximum age < 40)
Long-lived (40 < maximum age < 80)
Very long-lived (80 < maximum age < 160)
“Bluefin tuna is a long-lived species, with a lifespan of about 40 years, as indicated by radiocarbon deposition and can reach 330 cm (SFL) and weigh up to 725 kg.” (summary report.pdf)

3.2 Stock depletion

Crashed (D < 0.05)
Very depleted (0.05 < D < 0.1)
Depleted (0.1 < D < 0.15)
Moderately depleted (0.15 < D < 0.3)
Healthy (0.3 < D < 0.5)
Underexploited (0.5 < D)
Biomass estimates from SS3 indicate biomass is approximately 20% of unfished (Figure 4 of summary report: Biomass estimate.png)

3.3 Resilence

Not resilient (steepness < 0.3)
Low resilience (0.3 < steepness < 0.5)
Moderate resilence (0.5 < steepness < 0.7)
Resilient (0.7 < steepness < 0.9)
Very Resilient (0.9 < steepness)
Stock recruit data are not particularly informative, but steepness was estimated (in SS3) to be ~0.55 to 0.6 depending on whether bluefin spawn at age 5 or age 15 (Figure 40 of detailed stock assessment; Bluefin recruitment.png)