| Long-term changes of economical- and ecologically important fish species for the NEP were reconstructed based on fish scale preserved in laminated sediments from Effingham Inlet, a small fjord on the southwest coast of Vancouver Island, British Columbia. Several Box and Kasten cores covering the last 750 years of sedimentary record were analyzed for depositional history, chronostratigraphy and fish scale flux to the sediments. A high-resolution chronology derived from X-rays analysis and radiometric techniques (210Pb and 14C) was developed in order to reconstruct reliable rates of scale deposition into the sediments. Varve layering is the predominant type of sedimentation, making fjords excellent recorders of ancient history (both terrestrial and marine) at a very high resolution. However, in highly seismic regions a continuous reconstruction seems unreachable given the massive earthquake-triggered turbidites that usually erase several decades of record.; Comparisons of the scale deposition rate in the sediments with data on biomass trends show that the signal of Pacific hake in the sediments represents well the presence and local abundance of the offshore stock in British Columbia and, to some degree, the changes in total biomass of this stock. In contrast, the reconstructions for Pacific herring and Pacific sardine were not as successful. P. sardine scales were relatively rare in the sediments, whereas the P. herring signal is very local, failing to mirror the dynamics of the stock from the West Coast Vancouver Island.; All species experienced major changes in abundance with a strong pattern of variability for P. herring (50–60 years), a spiky one for P. hake and multi-scale pattern for Northern anchovy (15–20, 30–50, and 110 years). N. anchovy showed a negative relationship with upwelling, and possibly a non-linear one. A comparison with the record from Santa Barbara Basin suggests that fluctuations in the northern and central stock of N. anchovy are not in phase, in response probably to different wind-induced oceanographic conditions. N. anchovy and P. hake did better during high frequency Pacific Decadal Oscillation (PDO) states (before late 1800's), compared to P. sardine and P. herring, which seem to be favored by a slow beating PDO. |
