Genetic Diversity and Population Structure of Deep-Sea Fish in the North Atlantic.
The Problem & the Fish
Global fish catches have increased for the last fifty years but this has been at the expense of overexploitation of many stocks, especially those in easily accessible shallow waters.
Among the consequences has been increased competition amongst fishermen as well as an increase in the regulation of fisheries. Since the 1960s, this has stimulated a move to exploit deep-sea fisheries resources (defined as below 500m depth) in many parts of the world, but often these fisheries have proven unsustainable.
The new fisheries are directed towards two main classes of species. The first group includes those species that inhabit banks and seamounts, which tend to be robust deep-bodied animals capable of swimming against the strong currents. They tend to have a high quality flesh, making them highly desirable as a commercial product. They also aggregate, allowing fishing vessels to locate shoals and catch very high yields of fish in a relatively short time.In the North Atlantic, such species include: orange roughy, scorpion fish, bluemouth and alfonsino.
The second class of exploited species are slope- or open seafloor-associated fish. These species are often relatively slender and are generally adapted to drift, or swim slowly across large areas of the seabed. They are generally predators and scavengers, often feeding both in the water column and on or near the bottom. These species include the black scabbard fish, the roundnose grenadier and hake.
Overexploitation in these fisheries has probably been the result of many factors, including high intensity trawling of spawning aggregations, underestimation of time to maturity and fecundity along with an overestimation of species growth rates, and a lack of appreciation of spatial structure and dispersal of populations.
This lack of appreciation is critical for effective management, and this will be a primary focus of our genetic studies. For example, different fish populations or reproductively isolated stocks may have different population parameters (growth, reproduction, mortality) and show very different responses to exploitation. Because of the sedentary nature of many deep-sea fish species, populations may also be at severe risk of local depletion if fisheries quotas are set for larger geographic areas.
It is clear, therefore, that there is an urgent requirement for estimation of population structure and dispersal in commercial deep-water species for effective management.
Genetics & the Solution
The only means of accurately estimating these parameters is through the use of genetic methods. As well as the identification of stock structure in deep-sea fish populations, genetic analyses can be used to examine the distribution of genetic diversity (a basic unit of biodiversity), and the evolution of deep-sea species in general.
Beyond facilitating effective management, genetic studies will tell us a great deal about the evolution and behavior of these species, including the way new species form, the dynamics of populations over time, and the possible impact of climate change.
How are scientists going to carry out their genetic studies? Read about an innovative portable genetics kit project