Article 12.4 – States that Member States shall establish a system to monitor the incidental capture and killing of the animals species listed in Annex IV (a). In light of the information gathered Member States shall take further research or conservation measures as required to ensure that incidental capture and killing does not have a significant negative impact on the species concerned.
In relation to the situation for harbour porpoises in Sweden, research to date has revealed that:
Harbour porpoises have declined in the Skagerrak, Kattegat and Baltic Seas since the 1960s (Berggren and Arrhenius 1995a, b)
Harbour porpoise populations in the Skagerrak-Kattegat Seas and the Baltic Sea are distinct from each other and from other populations in the North Sea (Tiedemann et al. 1996; Börjesson and Berggren 1997; Wang and Berggren 1997; Berggren et al. 1999a)
Sighting surveys led to estimates of 36 046 (CV=0.34) animals in the Skagerrak, Kattegat and Great Belt, including both Swedish and Danish waters (Hammond et al. 1995) and only 599 (CV=0.57) in the southern Baltic Sea (excluding a 22 km corridor along Poland's coast) (ASCOBANS, 1999a).
Using observers in the set net fishery for cod and pollock in the Swedish Skagerrak and Kattegat Seas in 1997, bycatches were concluded to occur at levels too high to be sustained by the population, and it is known that additional bycatches, yet to be estimated, occur in ten other types of fisheries in the same areas (Harwood et al. 1999).
In the Baltic Sea, the situation is even more critical as the porpoise population there is considered to be extremely depleted and should be addressed as a matter of urgency if the population is to be saved. Based on records of animals bycaught compared to the available abundance estimate, bycatches in the Swedish waters of the Baltic Sea are considered to be unsustainable and if ongoing will likely result in further decline of this depleted population (Berggren et al. 1999b).
Yet despite this alarming information, no observer programmes have been initiated by Sweden and as such no observer based estimates of bycatch exist for Swedish fisheries in the Baltic Sea. What information there is comes from records of animals bycaught in salmon drift nets and set nets for cod reported and submitted to Swedish Natural History Museums. These are considered to be an absolute minimum estimate (Berggren 1994).
The CMS Agreement on the Conservation of Small Cetaceans in the Baltic and North Seas (ASCOBANS) as well as the International Whaling Commission (IWC) small cetaceans subcommittee have repeatedly stressed the need for monitoring and mitigation of harbour porpoise bycatch in these fisheries, stressing in particular the urgency in the Baltic Sea (ASCOBANS 1997; 2000a; 2001; IWC 1996). The most recent meeting of experts (ASCOBANS 2001) noted that “in terms of assessing the status of Baltic Sea harbour porpoises the ASCOBANS Baltic discussion Group (ABDG) agrees that as a matter of urgency every effort be made to reduce bycatches towards zero as soon as possible.” (ABDG emphasis).
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