Page 4 - Bearzi_2002
P. 4

action is urgently needed to prevent their extirpa-  ahead, but cetacean deaths in various fishing gear
               tion in this region (Reeves et al., In press) .  Relic  occur virtually everywhere, and are often among
               common dolphin sub-populations are still report-  the main causes of human-related mortality for a
               edly involved in fishery depredations in coastal  number of cetacean species.  Incidental captures
               portions of the Mediterranean, including Tunisia  in fishing gear – the impact of which is often un-
               and Cyprus (UNEP 1998b, Reeves et al. 2001).    derestimated - certainly represent a serious threat
                  The striped dolphin - by far the most abundant  to the survival of many cetacean populations
               cetacean in the Mediterranean - has a pelagic dis-  around the world, and in some areas have brought
               tribution and largely  feeds on non-commercial  cetacean species or populations close to extinc-
               prey species (Notarbartolo di Sciara and Demma  tion (IWC  1994, Reeves  and Leatherwood  1994,
               1994).  Therefore, it rarely represents a problem  Read 1996).
               to coastal fisheries, apart from gear damage or   In the Mediterranean, the problem of inciden-
               time loss for fishermen when the animals get en-  tal mortality in fishing gear has caught the atten-
               trapped in fishing gear.                       tion of both scientists and the general public due
                                                              to high-seas driftnet fishing by vessels flying Ital-
               Impact of fisheries on cetaceans. Fisheries can   ian and other flags.  A recent European Union
               affect cetaceans both directly and indirectly. Ef-  ban of driftnetting may result in decreased by-
               fects on the animals may include:              catch rates in portions of the basin, however the
                                                              problems remains in unregulated waters and in
               1.  bycatch in fishing gear;                   areas where illegal use of driftnets is an issue.
               2.  injury or mortality from retaliatory measures   In the Italian seas alone, where an effective
                   taken by fishermen who may perceive the  cetacean stranding network exists, it has been
                   animals as competitors, or blame them for  calculated that 83% of the stranding events oc-
                   gear damage or catch reduction;            curred between 1986-90, for which the cause of
               3.  unintentional disturbance by fishery-related  death could be established, resulted from bycatch
                   operations;                                in driftnets (Cagnolaro and Notarbartolo di Sciara
               4.  reduction of food prey availability or changes  1992).  Although bycatch has been reported for
                   in food prey composition/distribution caused   most Mediterranean species, incidental captures
                   by overfishing;                            in fishing gear have mostly affected sperm
               5.  habitat loss and/or degradation (e.g., from  whales, common dolphins, bottlenose dolphins,
                   bottom trawling);                          and striped dolphins (Perrin  1988, Di Natale and
               6.  short-  to long-term modifications in cetacean   Notarbartolo di Sciara  1994,  Northridge and
                   behaviour leading to emigration, dispersion  Hofman 1999).
                   or reduced reproductive rates as a conse-
                   quence of direct or indirect interactions with  Entrapment in pelagic driftnets. Pelagic drift-
                   fisheries.                                 nets are long, non-selective nets with strong,
                                                              loose nylon mesh that can virtually entrap all
                  The part that follows specifically focuses on   kinds of large marine animals.  Worldwide, these
               the potential or known impact on Mediterranean  nets have been depleting a number of cetacean
               cetaceans of the threats listed above, with the ex-  populations, including species of all sizes (Read
               ception of item listed as n. 2 (“injury or mortality  1996). Driftnet fisheries around the world that
               from retaliatory measures …”), which was dealt  have shown to be highly detrimental to cetacean
               with elsewhere in this Report (Notarbartolo di  populations include the Japanese North Pacific
               Sciara and Bearzi 2002).                       driftnet fishery for salmon (Ohsumi  1975), the
                                                              Taiwanese driftnet fishery for shark, tuna, and
                                                              mackerel off northern Australia (Harwood and
               Fishery interactions involving unintentional  Hembree   1987), the French tuna driftnet fishery
               takes (bycatch)                                in the north-eastern Atlantic (Goujon et al. 1993),
                                                              and several others (Northridge and Hofman
                  Before the mid to late 1960s, there was no  1999).
               place in the world where the magnitude of by-     In the Mediterranean, pelagic driftnets are
               catch was considered great enough to threaten a   used by the drift gillnet fishery for small pelagic
               population of cetaceans (Reeves and Leather-   fish, and by the drift gillnet fishery for swordfish
               wood  1994).  We are now only a few decades    and albacore (IWC 1994).  The latter involves the

                                    Cetaceans of the Mediterranean and Black Seas   –   9.4
   1   2   3   4   5   6   7   8   9