Morphometric differences between sub-populations of northern shrimp (Pandalus borealis). A case study from two adjacent fjords in Iceland

Northern shrimp (Pandalus borealis) are considered to represent localized populations in inshore and offshore Icelandic areas, with limited connectivity during adult stages. Due to potentially high larval drift it is unlikely that genetic differences are observed between nearby locations. Hence other methods, like phenotypic characters, are commonly used to distinguish between populations. In this study, the population structure of 1 and 2 year old northern shrimps was studied in two adjacent fjords in northwest Iceland. Samples were collected from three different areas within one fjord and a single sample was collected in an adjacent fjord and used as an outgroup. By using morphometric analysis, with ten different body measurements, it was possible to discriminate between northern shrimp from all the four areas within the two fjords. Discriminant function analysis correctly classified 42%-79% and 41%-57% of 1 and 2 year old shrimps, respectively. Even though this does not confirm the existence of genetically distinct populations, it does reflects life history and phenotypic difference among the areas. Body morphometrics therefore proved to be a promising method to discriminate between 1 and 2 year old northern shrimps.