domingo, 12 de julio de 2015

Killer whales... The fight for tuna

Tuna fishing is a struggle for survival, between men, killer whales and of course tuna themselves…

The competition between the fishermen and the killer whales heats up in the Strait of Gibraltar, as the Red Tuna (or bluefin tuna) migrates from the Mediterranean sea to the Atlantic ocean, every summer, after spawning…

Each year, the fishermen are waiting, and so are the killer whales…

Bluefin are the largest tuna and can live up to 40 years. They migrate across oceans and can dive more than 4,000 feet. Bluefin tuna are made for speed: built like torpedoes, have retractable fins and their eyes are set flush to their body. They are tremendous predators from the moment they hatch, seeking out schools of fish like herring, mackerel and even eels. They hunt by sight and have the sharpest vision of any bony fish.

Tuna swim very deep, as well as fast, and Moroccan fishermen use the fishing line method to catch the tuna, from under two hundred meters deep… 

(Spanish fishermen use the traditional Almadraba on the tuna entering the Mediterranean in the spring and the concrete block fishing when tuna are leaving in the summer).

With the line paid out, the crew can only wait and hope… and watch the whales. The sound of the winch is the signal for the waiting whale… a fish has been hooked…

In fact, a direct symbiosis between whales and fishermen goes on, such that fishermen use the whales to guide themselves to areas where the tuna are scrolling through deep water. 

Once fishermen throw their fishing lines, killer whales start swimming, circling among fishing boats, hoping that tuna bites the bait. Patiently, they wait for fishermen to rise tuna to the surface, and that is when the cetaceans attack the capture, taking the commission from their previous collaboration.

The fishermen will have to work as fast as possible to bring the line on board. By the time the fish nears the boat, all the fight has gone out of it. This is as easy a meal as a killer whale would hope for. The whales can steak the tuna in minutes. 

Estimated losses due to the groups of whales that prey tuna caught by artisanal fleets operating in the Strait of Gibraltar are in reality believed to be under 15% of catches.

This eating habit wouldn’t do much for whales popularity, but only a mere 5% of fishermen in the Spanish Tarifa fishing port are reported to be against the killer whales. On the other hand, recent whale watching economical activities are fast increasing. 

No wonder, it is too good an opportunity for killer whales to miss.

The Mediterranean Red Tuna fishery as a whole is far from being sustainable, mainly because this species is currently overexploited and endangered. 

Natural tuna catch alone cannot maintain anymore the killer whales population growth rate, but they need from traditional fisheries to which they "steal" the fish caught in the lines. In this way, whales began eating tuna from the fishermen only around thirty years ago and now, the culture has spread among all the members of the locals groups. 

The population of killer whales of the Strait of Gibraltar is classified as " critically endangered " according to their numbers, 30 individuals, divided into 3 more or less stable social groups. 

They are located mainly in shallow waters west of the Strait, both in spring and summer. From March to May, these groups are located in areas of the Gulf of Barbate and Conil, while in June they are near the port of Tarifa. In July to October they move to areas of both Moroccan and Spanish fisheries. 

It is quite uncertain where do they travel from November to March... Sights have been reported in the portuguese Algarve coast, and they also might swim onto the Açores islands or mid-way to Canarias... maybe even further... but that is mostly unknown.

Orcas, or killer whales, are the largest of the dolphins and one of the world's most powerful predators lacking natural ennemies. They are found in all oceans, from the frigid Arctic and Antarctic regions to tropical seas. Killer whales as a species have a diverse diet and some feed exclusively on fish, while others hunt marine mammals. Killer whales are highly social, some populations being composed of matrilineal  family groups which are the most stable of any animal species. Their sophisticated hunting techniques and vocal behaviors, which are often specific to a particular group and passed across generations, have been described as manifestations of culture.

The fishing day is over and the fishermen disembark the product of their strenuous effort in their traditional ports, on the southern shore of the strait.

The expectation on the docks is remarkable... children and adults contemplate the fishery product. 

Despite the tribute given to the whales , the day has been good and still ensures the livelihood of families...

Actividad más comercial que científica, a pesar de palabras como "fundación, investigación, estudio", es encomiable la labor de las empresas de avistamiento de cetáceos de Tarifa, que han puesto en valor la presencia de estos bellos animales en el Estrecho, constituyendo una alternativa de turismo sostenible que hace rentable la conservación del patrimonio natural. Entre ellas yo tengo palabras de agradecimiento al entusiasmo de los biólogos de Turmares de quienes soy asiduo cliente.

Nada es perfecto y las molestias inevitables a los animales siempre son mejores que darles la espalda, cuando no directamente alterar su hábitat o perseguirlos. No hace tanto, las últimas industrias balleneras en España se radicaban en el estrecho... 

3 comentarios:

  1. Artículo muy interesante.

  2. Impresionante. No sabía que teníamos horcas en el Mediterráneo. Son bien guapas!

  3. Espectacular lucha por la vida en el estrecho!!!!


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