Since its inception, the management of the fishing industry has not been designed in a sustainable way and today most commercial marine species are overexploited. Faced with this well-known reality, European authorities have been adopting different measures to guarantee the responsible exploitation of marine resources and put an end to the problems of overfishing in European waters. The path began a few years ago and the results of the different measures adopted are beginning to be felt. The Atlantic hake population is recovering from the effects of overfishing and, after reaching a minimum index in 2004 with 300 spawners in the Northwest Fishing Area of the Iberian Peninsula, this figure has multiplied to currently reach 5,000 effective spawners, “that is, 5,000 individuals that really contribute their genes to the next generation”, explains José Cuéllar, researcher at the Marine Genetic Resources Laboratory, author of a doctoral thesis in which he applied genetic markers to delve into the study of the fish stock and the evaluation of the effects of overfishing on the structure and effective size of the different populations.
In the case of European hake, different measures have been implemented over the last decade to halt the deterioration and promote its recovery. In order to evaluate the evolution of molecular diversity in the face of overexploitation processes of this species, the team of researchers from this Vigo laboratory analyzed several molecular markers in different time series (1976, 2000-2005 and 2007) and compared these data with the current situation. The results leave no room for doubt, the population is recovering and the main measures that contributed to this improvement were “the increase in mesh size in fishing gear and the reduction in fishing quotas”, explains the author of the thesis, who emphasizes that the genetic data from the southern fishery also agree with the model of demographic connectivity throughout the Atlantic proposed by this laboratory and whose focus of radiation places the main spawning areas in the Porcupine Bank (about 200 kilometers northwest of Ireland) and in the Gran Sol, an area that stands out for its fishing wealth, especially as far as hake is concerned.
All this genetic information collected in Cuéllar’s doctoral thesis on the population genetic structure of European hake allows us to better understand the limitations of demographic models and, in turn, is key to assessing the risks of extinction due to genetic factors, allowing us to incorporate structuring and genetic diversity criteria into management and, in this way, “prevent the deterioration of the physical characteristics of this species and therefore guarantee its sustainability and that of dependent species”, emphasizes Cuéllar, who gives as examples of these dependent species the anchovy and squid “which are the main species on which hake feeds”, emphasizes the researcher.
Cod and plaice, among the most exploited species
One of the main observations of the work, led by researchers Pablo Presa and Alfonso Pita, is that, regardless of the variation in genetic diversity, the attrition of physical characteristics such as age and average size at maturity in intensively exploited species, such as cod and American flounder, is very high. “Hypothetically, the deterioration of physical characteristics could be a by-product of overfishing without consequences for genetic diversity. However, another plausible scenario would be one in which the genetic and physical characteristics of the population have been eroded to such an extent that it is not possible to recover the diversity they had before exploitation began,” explains the author of the thesis, who highlights the fact that, for the moment, with the volume of information available on the temporal evolution of the genetic diversity of overexploited species still very low, no genetic erosion parallel to demographic has been observed, a fact that they attribute to the fact that the effective genetic size of the fisheries has not decreased below the lower precautionary limit.
The research also allows us to measure how much and when the greatest loss of physical characteristics of exploited species occurred and how much potential has been lost in these characteristics in the last hundred years, both in natural populations and potentially for their future exploitation in aquaculture. “For example, between 1985 and 1997, 15% of the length and 25% of the age of maturity of cod in the Baltic Sea were eroded,” Cuéllar emphasizes, while explaining that the most important changes occurred between 1970 and 1980, when industrial fishing began to significantly impact the fish stocks, “with the increase in engine power, the increase in fishing effort and large factory ships.”
From Colombia to Vigo to specialize in Marine Biology
Colombian by birth, José Andrés Cuéllar (1983) moved to Galicia at the beginning of 2011 to study the Master’s degree in Marine Biology at the University of Vigo. “I chose this University and this master’s degree in particular for different reasons, but one of the most important ones was the opportunities given to students and the opportunities to do internships in companies and research centers,” explains the researcher, who, after defending his thesis, hopes to be able to do a postdoctoral stay in Canada or Norway.
Source: Duvi
