By CAPosts 22 February, 2021 - 05:30pm 50 views
"The common dolphin has become the least common of the dolphins in the Mediterranean." Its population plummeted at the beginning of the 20th century and in 40 years, its presence has dropped by 50%. Although its world conservation status is of “least concern”, in Spain it is considered “vulnerable” ( National Catalog of Threatened Species ) and, in Andalusia, it is in critical danger of extinction. "In the bay of Algeciras we have a fundamental enclave for its survival." This is what José Carlos García Gómez, professor of Marine Biology at the University of Seville and co-author - along with Liliana Olaya-Ponzone, Rocío Espada, Estefanía Martín and Isabel Cárdenas - warns of an investigation published by Cambridge University Press in the specialized journal Journal of the Marine Biological Association of the United Kingdom . The scientific article details blows, mutilations, deformations, amputations and tears suffered by dozens of cetaceans who are victims of certain sport fishing practices, sailing pleasure boats, uncontrolled sightings (people who come to see them on their own or carried by companies not regulated), as well as due to the proliferation of jet skis
This carnage (wound, injury, etc., with effusion of blood, according to the third meaning of the RAE) adds to the threats that dolphins already face due to the destruction of their habitats and competition with industrial fishing. But the same investigation warns that injuries - "sometimes very serious", according to García Gómez - caused by propellers and boat hulls, as well as lines, are avoidable and can be acted upon immediately by creating a small sanctuary in the area. Bay of Algeciras, where their concentration and presence is more frequent, are protected (at least partially) and the wounded can be cured, promoting, without direct threats, the normal development of the resident population of common dolphins. In this way, the threat of collision with fast boats or by interactions with other sport fishing boats would be mitigated
In the Strait of Gibraltar and the Bay of Algeciras, seven species of cetaceans are commonly observed (other species are sporadic), some of them with documented resident populations. Among them are the striped dolphin ( Stenella coeruleoalba ), the bottlenose ( Tursiops truncatus ) and the common ( Delphinus delphis ). The last two are covered by the EU Habitats directive , which requires the adoption of management and conservation measures
But that same area suffers from intense traffic of ships of all kinds (the Strait is considered the second busiest channel in the world) , It has one of the 25 largest ports in the world (Algeciras) and has 4,000 registered recreational vessels.
Sport fishermen take advantage of dolphins as “surface signals” to locate tunas
“Fisheries management has been a success with bluefin tuna, which has recovered. And where there are tunas, there may be dolphins because they compete for the same trophic resource ”, explains García Gómez. The sport fishermen know this and the dolphins become "surface signals" to locate the tunas.
Although the sport and recreational fishing of bluefin tuna is prohibited in a resolution of May 20, 2019 , many of the boats in the They are caught by trolling (dragging a lure) or by surface popping or spinning , an artificial bait that floats and is pulled so that it splashes the water and attracts the tuna, with a sturdy rod and braided line. the dolphins point out the tuna shoals, the boats place the artificial baits in the groups of cetaceans. “Tuna are capable of traveling between 10 and 14 times their body length in a second. If you drag a line at such an explosive speed, it can cause serious cuts to the dolphins that are in the area ”, explains the researcher from the Marine Biology Laboratory of the University of Seville.
To this activity we must add the lacerations caused by the propellers and collisions or noise from maritime traffic and jet skis. All these circumstances generate a stress that makes dolphins more vulnerable and cause changes in distribution and abundance, a decrease in the reproduction rate or death, according to another study signed by the authors cited in Almoraima. Journal of Campogibraltareños Studies .
In the observation campaign that served as the basis for the latest investigation, 182 sightings were counted, during which 605 interactions were recorded by commercial vessels dedicated to whale watching (43%), recreational (29%), associated sport fishing bluefin tuna (22%), unregulated charters for whale watching (3%), jet skis (2%) and sailing schools (1%)
But this hellish environment for dolphins can be reversed. "It had to be demonstrated and this is what we have done in the last investigation," says García Gómez. From 90,391 photographs taken over four years, in which 1,402 sightings were recorded by the Dolphin Adventure tourism company team, the scientists managed to specifically track five of them with external injuries of different origins and severity. The work showed that dolphins can be cured between three and 21 weeks after the injuries suffered, although the work suggests that one of the monitored specimens died. The article emphasizes the need to safeguard this protected species that, according to the biologist from the University of Seville, is the “jewel in the crown in the bay of Algeciras, even from an economic point of view due to its possibilities of sustainable exploitation through activities ecotourism as well as citizen science. ”
“ Each time an individual with recent injuries was detected, photographs were taken with two digital reflex cameras to identify individual dolphins using standard imaging methods. The lesions were characterized to assess the progression of healing during the study period and to identify their causes. Depending on the shape, depth, area of the body, deformities, mutilations and other factors, it was determined what caused the wound ”, explains García Gómez.
The importance of the study is not only the analysis of the causes and consequences of the attacks on the dolphins. Its main objective is to demonstrate that once identified, contingency measures can be established in one of the most ecologically and environmentally important enclaves for the common dolphin, especially as it is a breeding and development area for juveniles of the species that, in the early stages of their life, find it difficult to go out to the Strait area with their given mothers the strong prevailing currents.
The research proposal is to create a “visible, localized and respected sanctuary”, according to García Gómez, where there is a higher concentration of dolphins and where the causes of injuries are avoided and reproduction is favored , new births and calf care
In an article published in Science Direct , scientists Jean Jacques Maguire, Serge Garcia and Ray Hilborn admit the role of marine reserves as a good tool for the management and conservation of biodiversity, but warn that are not the panacea to problems.
The sanctuary can be an effective solution in the bay of Algeciras that it is difficult to imagine that anyone could oppose. We have to get involved with these animals José Carlos García Gómez, Professor of Marine Biology at the University of Seville
García Gómez shares that conclusion, but clarifies that, in this case, it can be an effective solution in the bay of Algeciras to which "it is difficult to imagine that anyone can oppose". "We have to get involved with these animals," he concludes in defense of his proposal, which includes protocols for approaching regulated vessels to avoid stress to dolphins as much as possible.
The problem does not only affect the Strait area, although it may be of special global importance. A study by Ali Ross and Stephen Isaac for Greenpeace estimated that more than 10,000 cetaceans are accidentally caught off Europe's Atlantic coasts. Another one, published in Plos One , on the accidental capture of dolphins, concluded that this cause of mortality will mean, if it is maintained at current levels, the population reduction of the common dolphin by 20% in 30 years and the probable extinction in 100 years
Sharks and rays
Nor is it an exclusive problem of this species. A recent study in Nature estimates that the population of sharks and rays in the oceans has decreased by 71% since 1970, mainly due to overfishing. "The Window to save these iconic creatures is too small," lead study author Nick Dulvy, a marine biologist at the Canadian University Simon Fraser, told The New York Times . More than three-quarters of the shark and ray population are threatened with extinction
Scientists highlight how conservation measures work when applied correctly and call on governments to adopt them and set catch limits accordingly of scientific criteria.
The same work warns of the importance of avoiding accidental catches. "Even if they stop commercial fishing of sharks, their numbers continue to fall for this involuntary fishing" advierten.
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