Haddock is a saltwater fish that can live for up to 20 years and reach a size of 110 cm and 20 kg. Haddock belong to the Gadidae family, the true cods, together with other commercially important fish species such as e.g. Atlantic cod, whiting, and pollock. Haddock is easy to distinguish from other cod fishes as they have a prominent dark spot over their pectoral fin, sometimes called the "Devil's thumbprint” or "St. Peter's mark". They are found
in coastal areas and on offshore banks throughout the North Atlantic, Arctic, and Barents Sea. After their planktonic egg and larval stages, haddock then live near the seabed as juveniles and adults, feeding on small invertebrates and fish.
Haddock support productive and sustainable fisheries on both sides of the North Atlantic. Along with Atlantic cod, it is served as "fish and chips", as well as being sold frozen, fresh, dried or smoked. Hence, the fishery for haddock is large and economically important. According to FAO, more than 315 000 tons of haddock were caught in 2018, which was about one quarter of the Atlantic cod catches (1.2 million tons) for the same year. Considerable attention has therefore focused on maintaining healthy haddock stocks in the North Atlantic along the coasts of Canada and the USA, and along the shores of northern Europe, especially the British Isles and Scandinavia.
An essential component of managing sustainable harvests is the definition of population boundaries, as inconsistency between management units and population boundaries may result in overexploitation of the weaker stocks within a fishery. In addition to tagging experiments, several molecular methods, including the analyses of DNA, have been used to define the geographic extents of haddock populations in the past. By incorporation population structure into management advice, fisheries can potentially be better administrated so that harvests do not inadvertently overfish some populations.
The
latest Editor's Choice study is from a collaboration of researchers in several fishing nations across the North Atlantic who sampled more than 1000 haddock and examined 138 novel genetic markers called single nucleotide polymorphisms (SNPs) to measure genetic variability among fishing grounds across the North Atlantic and into the Arctic and Barents Sea.
By using high-definition SNPs, the study uncovered not only a major genetic divide among North American, European, and Arctic haddock, but also differences among coastal and fjord populations in Europe. In some regions, it was found that current haddock management areas encompass more than one genetic population, which indicates the need to redefine some management units.
Editor's Choice are always free to read in ICES Journal of Marine Science.
