Over-exploitation and the collapse of the population pose significant threats to marine fish stocks around the world. While some fish populations have already collapsed, research has shown that nearly one-third of the world's fishing zones are currently affected by survivability.
The "Reporting on yields and conservation objectives through the collection of young people and adults" published in the The American naturalistNiklas L.P. Lundstrem, Nikola Loye, Xinzhu Meng, Mats Bodin and Åke Br? Nnström stressed the urgent need to improve management practices in the fisheries sector to mitigate these trends and preserve fish populations. In the article, the authors examine whether changes in harvesting practices have the potential to optimize yields while giving priority to sustainability.
The study aims to determine whether the reduction of the harvests of some of the maximum sustainable yield or MSY will lead to high yields, while at the same time supporting conservation efforts. Introduced by MacCall and Hillborn, these reduced yields are known as "pretty good yields," or PGY, and contain 20% less fish than the amount typically harvested in maximum sustainable yield.
Based on the scientific literature, the authors argue that while MSY has clear economic benefits, the concept is challenging to accurately assess and apply properly as a harvesting practice. Moreover, relying on harvesting strategies from the CSF did not do much to protect the fishery from collapse.
"Unlike the MSY harvest management objectives, PGY can be realized through a number of harvesting strategies and therefore leaves room for reporting other desired goals in addition to maximizing yields," the authors write.
Using both population age structure and population model structured at the stage, the authors conducted a stability analysis to illustrate how profitability and conservation measures change when different harvesting strategies are used. In particular, authors use models to assess whether the selective collection of larger quantities of young fish – or, conversely, larger quantities of adult fish – have affected the overall population stability.
The authors measure four different characteristics to assess the ecological stability of a given farm: biomass, size structure, basic reproduction ratio and sustainability. The authors refer to the structure of biomass and population size as "impact measures" that directly affect fish populations. The sustainability and reproduction ratio, on the other hand, serves as "risk measures" that assess the likelihood of disappearance of the population.
In order to address the inconsistencies between storage and yield, the authors consider harvesting by adults, harvesting juveniles and harvesting as three distinct functions. To determine the effectiveness of individual strategies, the authors explain an economic concept known as Pareto's effectiveness. According to this concept, the strategy reaches maximum efficiency when no further improvements can be made without changing one variable.
Pareto's front – a curve presenting the most effective harvesting strategies – was drawn against the three functions. This step was repeated for each of the four conservation measures.
The results show that the use of strategies to collect PGY instead of CSF strategies offers significant conservation benefits. In addition, the authors found that, in most cases, harvesting equal numbers of young specimens and adults effectively supports both the yield and the stability of the population.
Disclaimer: AAAS and EurekAlert! are not responsible for the accuracy of the news posted on EurekAlert! through contributing institutions or using any information through the EurekAlert system.