Notes for identifying the three macrourid species, M. holotrachys, M. whitsoni and M. carinatus in CCAMLR Subarea 48.3

Digital pictures and morphological measures are presented to aid CCAMLR observers with the identification of three macrourid species caught as bycatch in the fishery for Patagonian toothfish, Dissostichus eleginoides, in Sub-Area 48.3. Scaling under the snout was used to separate Macrourus holotrachys (no scales) from both Macrourus whitsoni and Macrourus carinatus (which are both scaled). The relative positioning of the second dorsal fin and the anal fin can also be used to distinguish M.holotrachys from M.whitsoni and M.carinatus. To distinguish M.whitsoni from M.carinatus two scale counts were used. M.whitsoni has a head ratio (head length/inter orbital distance) of less than 5.2 whilst M.carinatus has a head ratio of greater than 5.2. There was some overlap in the ranges of most of these measures and so a single character will not always successfully I.D. a species. However, combinations of 2 or more characters should be successful. Genetic analysis of liver samples will confirm species identification