“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 decreased by 50%. Although its global 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 journalJournal 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, the navigation of 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 research 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 immediately with the creation of a small sanctuary in the Bay of Algeciras, where their concentration and presence are most 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,
Seven species of cetaceans are commonly observed in the Strait of Gibraltar and the Bay of Algeciras (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 included in 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), has one of the 25 largest ports in the world (Algeciras) and has 4,000 registered recreational boats.
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 area catch them by trolling (dragging a lure) or by popping or surface spinning , an artificial bait that It floats and the one that is pulled so that it splashes the water and attracts the tuna, with a robust rod and braided line.
As the dolphins point out the tuna banks, the boats place the artificial baits in the groups of cetaceans. “The tuna is capable of traveling in a second between 10 and 14 times the length of its body. 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 must be added the lacerations caused by propellers and collisions or noise from maritime traffic and jet skis. All these circumstances generate a stress that makes the 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 recorded, during which 605 interactions were recorded by commercial vessels engaged in 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. Of 90,391 photographs taken over four years, in which 1,402 sightings were recorded by the team from the Dolphin Adventure tourism company, the scientists managed to specifically monitor 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,
“Each time an individual with fresh injuries was detected, photographs were taken with two digital reflex cameras to identify individual dolphins with 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 attacks on 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 since it is a breeding and development area for juveniles of the species that, In the early stages of their life, it is difficult for them to go out to the Strait area with their mothers given the strong prevailing currents.
The research proposal is to create a “visible, localized and respected sanctuary”, according to García Gómez, where there is a greater concentration of dolphins and where the causes of injuries are avoided and reproduction, new births and care of the young.
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 they are not a panacea for problems.
The sanctuary can be an effective solution in the bay of Algeciras that it is difficult to imagine that anyone could object. We have to turn to these animals
García Gómez shares this 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 could oppose”. “We have to turn to 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 is 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 the European Atlantic coasts.
Another one, published in Plos One , on the accidental capture of dolphins, concluded that this cause of mortality will mean, if it remains at current levels, the population reduction of the common dolphin by 20% in 30 years and the probable extinction in 100 years.
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 very 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 based on scientific criteria.
The same work warns of the importance of avoiding accidental catches. “Even if commercial shark fishing were to stop, their numbers would continue to fall due to this involuntary fishing,” they warn.