Haddock populations in the Northeast Atlantic show large genetic variations
A new study has shown that there are large genetic variations in haddock populations, and it advises that these haddock populations should be managed separately.
The study which compares several haddock populations in the North Atlantic found that the fish can belong to different biological populations and even though haddock are extensively pelagic during their juvenile stages adult haddock normally do not cross the gene flow.
For example, in the Northeast Atlantic, haddock that live south and north of Lofoten Islands in Norway belong to different biological populations.
Similarly, from a sample taken from the Shetland Islands and the Moray Firth located west of the Greenwich meridian and the Viking Bank and North Sea samples located east of the Greenwich Meridian, biological differences were found in the haddock stocks.
A distinction was previously made for haddock east and west of the Greenwich meridian but based on the FST values, the Shetland sample was significantly differentiated from all other samples in the dataset, except for the adjacent Viking Bank sample.
The Shetland and Viking Bank samples come from deeper (>100 m) and colder waters than did the Moray Firth and North Sea central samples (<100 m).
A 1989 study described Shetland haddock as a genetically stable population yet belonging to the “west of Greenwich” group (consisting of west of Scotland, east of Scotland and Shetland) but distinctly differentiated from the “east of Greenwich” group (consisting of the Viking Bank and the Fisher Bank in the central North Sea).
The global distribution area of haddock and locations of the samples used in this study, the management areas and the known spawning grounds. Grey-shaded areas indicate the distribution area, light green-shaded areas indicate known spawning grounds, and coloured dots indicate the position where the samples were collected. The borders for the ICES and NAFO management units for haddock are shown with thick black lines. The management divisions/subdivisions are shown within thin black lines where the numbering refers to the respective divisions/subdivisions. Regions described in the text are written in red colour.[/caption]
The identification of Shetland as genetically distinct is also observed in the dataset, except for the low genetic differentiation relative to the Viking Bank, implying significant connectivity between these two samples. In contrast to 1989 study, it was observed there was a separation between the Shetland and Moray Firth samples which belong to the “west of Greenwich” group. The report says that it is difficult to explain the apparent reproductive isolation of Shetland from other biological evidence, as otolith chemistry indicates that juvenile haddock from the Moray Firth can recruit north to Shetland.
The findings of this study should have implications for the future management of haddock stocks.
The report finds three main genetic clusters, consisting of a Northeast Arctic cluster, a Northeast Atlantic cluster, and a Northwest Atlantic cluster. In addition, it was also observed there is a genetically distinct fjord population and genetic structuring within the North Sea. The study adds to the growing recognition of population structuring in marine organisms in general and fishes, in particular, and is of relevance for fisheries management claims the report.
The study acknowledges that it is challenging to incorporate such information into current fisheries management regimes. However, the identification of such patterns is an argument for not treating the entire coast into one management unit for this species.
Read the full report here