Atlantic tuna returns to birthplace to spawn

Scientists have observed new migratory patterns for Mediterranean and western Atlantic bluefin tuna.



It is fact that the Atlantic bluefin tuna is the largest and most sought-after of all tunas, weighing as much as 1,400 pounds and capable of fetching as much as $50,000 or more in Asian markets where its meat is a prized commodity. New study revealed that how bluefin tuna are managed on both sides of the Atlantic Ocean. A team of international researchers led by Dr. Jay Rooker of Texas A&M University at Galveston provides critical insights into the population structure and mixing of North American and Mediterranean populations of bluefin tuna.

The recent study examine the chemical composition of the fish's ear bone — the otolith — to identify individuals from different nurseries. Chemical signatures in the form of stable carbon and oxygen isotope ratios served as a "birth certificate" and were used by the researchers to determine the origin of adolescent and adult bluefin tuna (2-20 years of age or more) on spawning and foraging grounds in the Atlantic Ocean.

According to the study trans-Atlantic movement and mixing of populations was high with over half of the juveniles collected in North American waters being of Mediterranean origin. Researcher Rooker told that their data coupled with archival tagging data clearly show that the migratory patterns of bluefin tuna are more complex than previously assumed and information on mixing must be included in future assessments to ensure that rebuilding efforts are successful.

According to co-author Barbara Block from Stanford University, informed that despite the high level of mixing, the team also observed that over 95 percent of adult bluefin tuna returned to their place of origin in either the Gulf of Mexico or Mediterranean Sea to spawn. It is told that commercially harvested bluefin tuna in New England and Canada were found to be nearly entirely of Gulf of Mexico origin. Results demonstrate that Northern Canadian waters may represent critical foraging habitat of the smaller, more vulnerable population that spawns in the Gulf of Mexico.



Source: sciencedaily.com"



WorldFishingToday d. 05-10-2008



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