Stable δ13C and δ18O isotopes in otoliths of haddock Melanogrammus aeglefinus from the northwest Atlantic Ocean

Analyzing stable isotopes deposited in fish otoliths can provide insights into the environmental variation that individual fish experience throughout their life history which, in turn, can indicate their home range, movements, and underlying stock structure, We investigated the use of stable delta C-13 and delta O-18 isotopes in haddock Melanogrammus aeglefinus otoliths as indicators of environmental variation and stock structure in the northwest Atlantic Ocean. Samples were collected between 1995 and 1998 from individual spawning components on Georges Bank, the Gulf of Maine, and along the Scotian Shelf. Samples from 1 yr- and 4 yr-old haddock were analyzed from an integrated and chronological life history perspective, respectively. Annual, seasonal, and ontogenetic variation in otolith isotopes indicated that haddock undergo shifts in distribution throughout their life history, possibly as a means of compensating for variable environmental conditions; this underlines the difficulty of temperature reconstructions from mobile organisms with optimal temperature ranges.