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Geolocation query system for standardised analysis of migration paths in cod (Gadus morhua L.)

Environmental data from each ecosystem included in the CODYSSEY project were used to test initial geolocation methodologies and enable the development of an expert query system for reconstruction of cod migratory pathways. Individual migrations were reconstructed from the North Sea, the Barents Sea, the Icelandic plateau and the Baltic Sea using the new methodology with the environmental data most relevant to each ecosystem e.g. tidal and water temperature data in the North sea, water temperature and salinity in the Baltic Sea.

However developing a standardised geolocation query system for all four ecosystems within the CODYSSEY project has proved to be a difficult, if not impossible, task, for several reasons. First, environmental databases for each ecosystem were not always available in the same formats, with the same resolution, and with the same precision. Second, each ecosystem is very different in terms of the dynamic range of data, and therefore the discriminatory power of a standardised geolocation query system would vary considerably. It is therefore the case that applying a standard method was neither appropriate nor necessary, and geolocation methods for each ecosystem were refined to optimise results in those ecosystems.

Thus, we developed a number of innovative statistical techniques that were not only capable of estimating the position of cod with greater precision than before, but could also output estimates of certainty associated with these position. This is a step-change in the capabilities of geolocation of demersal fish, and the methods are also transferable to other species and locations.

Reported by

CENTRE FOR THE ENVIRONMENT, FISHERIES & AQUACULTURE SCIENCE
LOWESTOFT LABORATORY, PAKEFIELD ROAD
NR 33 0HT LOWESTOFT
United Kingdom
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