Data/hora: 01/06/2024 01:19:48

Provedor de dados: 	Institutional Archive of Ifreme (ArchiMer)	
País: 	France	
Título: 	Back to the future: investigating historical data of bluefin tuna fisheries	
Autores: 	Fromentin, Jean-marc.	
Data: 	2009	
Ano: 	2009	
Resumo: 	The exploitation of Atlantic bluefin tuna in the Mediterranean Sea goes back to the first millennium before Christ and the Romans already took benefits of the bluefin tuna reproductive migration to catch them. Bluefin tuna catch did not remain stable along its millennium exploitation history but displayed conspicuous long-term fluctuations that could result from environmentally-driven changes in the bluefin tuna migration routes. The Nordic fisheries that took place in the Norwegian and North Sea in the early 1920s were the most spectacular example of Atlantic bluefin tuna fisheries collapse. During the 1950s, the Nordic fisheries were the most productive ones, catching up to 18,000 tons/year, but they suddenly crashed down without any warning in 1963. Little is known about this collapse and several hypotheses can be put forward, such as changes in migratory routes, recruitment failure or eradication of a subpopulation (all of these hypotheses could result from natural causes and/or from overfishing). To help explain this mysterious event, an original dataset of the main bluefin tuna fisheries of the 20th century, including total catch and size composition of the catch, has been compiled and analysed. All the analyses performed on the time series of the catch or the size composition of the catch indicated a strong and unambiguous link between the Nordic purse seine and Spanish trap fisheries during the 1950s and 1960s. It can be thus postulated (with a rather high level of confidence) that the largest part of fish caught in the North Sea and Norwegian Sea between July and October came out from the Gibraltar strait and most probably from the western Mediterranean where they were spawning in June. However, this link vanished during the 1970s. In addition, the northwest Atlantic and Mediterranean trap fisheries appeared to also be partially connected to the Nordic fisheries. During the 1950s and 1960s, the main migration routes of bluefin tuna were probably from the Mediterranean spawning grounds and from the West Atlantic coasts to the Norwegian coast and North Sea, which were probably a key feeding ground at that time. Additional analyses on the time series of sea temperature and northeast Atlantic herring populations (which were the main preys of bluefin tuna) lead to conclude that the causes of the Nordic fisheries collapse are likely to result from interactions between environmental, trophic and fishing processes which may have finally modified bluefin tuna migration patterns (and possibly recruitment during a decade). This retrospective analysis further leads to an original -albeit more speculative- hypothesis on Atlantic bluefin tuna population structure, therein conjectured as an assemblage of at least three sub-populations, i.e., (1) a highly migratory one over all the North Atlantic (which would spawn in the western and central Mediterranean), (2) a more resident one in the Mediterranean (spawning in the central and eastern Mediterranean) and (3) a more resident one in the West Atlantic (spawning in the Gulf of Mexico).	
Tipo: 	Text	
Idioma: 	Inglês	
Identificador: 	http://archimer.ifremer.fr/doc/00193/30467/28872.pdf	
Editor: 	ICCAT	
Relação: 	http://archimer.ifremer.fr/doc/00193/30467/	
Formato: 	application/pdf	
Fonte: 	Collective Volume of Scientific Papers (1021-5212) (ICCAT), 2009 , Vol. 63 , N. 1 , P. 235-237	
Fonte: 	ICCAT