The fisheries exploitation in the estuary of the Río de la Plata , on the atlantic coast of South America, has reduced the average size of fish in this ecosystem, which has facilitated the capture of prey of the marine mammals with the lower palate and opening the mouth. The dolphin franciscana , a small cetacean endemic to the Rio de la Plata and in serious danger of extinction, is the marine mammal most benefited for this side-effect of the fisheries austral. This according to an article led by experts of the Research Group on Large Marine Vertebrates, Faculty of Biology and Institute of Biodiversity Research (IRBio) of the University of Barcelona.
The study, published in the journal Scientific Reports, examines the impact caused by industrial fishing in Uruguay and Argentina on the food habits of the dolphin franciscana (Pontoporia blainvillei), the wolf fine south american (fur seal australis) and the sea lion, south american (Otaria flavescens).
The findings indicate that the consequences of the industrial fisheries for marine mammals go beyond the simple reduction in the abundance of the biomass of the fish dam , that also depend on the morphological characteristics —body size and amplitude of the mouth— of each species.
The new job is signed by the researchers Massimiliano Drago, Alex Aguilar, and Luis Cardona, of the Research Group on Large Marine Vertebrates (UB-IRBio); Valentina Franco Trecu (University of the Republic of Uruguay), and Angel M. Segura, Meica Valdivia and Enrique M. González (Museo Nacional de Historia Natural, Uruguay).Refuge for animals in danger
The estuary of the Río de la Plata, on the west coast of the south Atlantic, is one of the richest ecosystems and most productive of the entire planet. The coincidence of the current cold Malvinas and the warm current of Brazil, which add to the mass of fresh water of the River of the Silver, it generates a high productivity of great commercial interest for the fisheries of the region.
since 1970, Argentina and Uruguay began the practice of industrial fishing in this area. Since then, this activity has reduced the availability of prey species and has hindered the recovery of the population of these marine mammals, which have been exploited commercially since the EIGHTEENTH century until the second half of the TWENTIETH century .
currently, the dolphin franciscana is considered the cetacean most threatened of the Atlantic ocean southwest . With a limited territorial extension, is the only species of river dolphin that inhabits coastal marine waters and is listed as a vulnerable species by the International Union for Conservation of Nature (IUCN).
The sea lion south american , another marine predator apical with a wide geographic spread, concentrated to 6% of your world's population in the area of the Rio de la Plata and is listed in the red list of threatened species of the IUCN with a range of minor concern. In the case of the lobo fino sudamericano , 75% of the world's population is in the region of the Rio de la Plata, an area of great ecological value for the conservation of the species and the maintenance of gene flow between different populations.oral Cavity
"The marine mammal populations of the area of influence of the Río de la Plata are an excellent model to study to understand the changes produced in the trophic relationships between species before and after the development of the fishing industry", explains Massimiliano Drago.
through the analysis of stable isotopes of carbon and nitrogen in the skeletal remains, the experts have compared the diet current of these marine species with the food resources they consumed in the past. According to the study, the dolphins franciscan are those who have most transformed the pattern of exploitation of resources in comparison with other marine mammals. At present, demersal fish juveniles —those who live near the bottom of the sea— are its main prey.
"In the dolphins franciscan, the breadth of the palate is intermediate between that of the sea lions (constitution and robust palate wider) and the sea lions (of smaller size and with a palate more narrow). As the intensive fishing has reduced the average size of the dams, this effect has benefited the marine mammals with the lower opening mouth, that is to say, the dolphins franciscan, and, to a lesser extent, the sea wolves," notes Drago.
So, the dolphins franciscan occupy today the same trophic level that the sea lions despite the large differences in the dimensions of the oral cavity. In the case of the dolphin, franciscana, these drastic changes in the patterns of trophic can also be influenced by factors such as, for example, the reduction of the populations of prey species —the catfish toad (Porichthys porosissimus)— that were abundant in the past and have declined now because of the catch .sea Lion south american - Massimiliano Drago
The sea lions are the species less favored by the intensification of fishing in this region, reveals the study. However, this does not mean that this is the species more vulnerable. "The vulnerability depends on a set of factors (resource reduction, plasticity, trophic, commercial exploitation, habitat degradation, etc). Definitely, the dolphin franciscana is the species more vulnerable in this ecosystem due to the high-mortality that cause the incidental capture and degradation of the natural habitat ", concludes Drago.Updated Date: 25 September 2019, 04:03