Phocoena phocoena (Baltic Sea subpopulation)

Several genetic and morphometric studies have concluded that the Baltic porpoises are a separate subpopulation distinct from those living in Kattegat, Skagerrak and North Sea (e.g., Tiedeman et al. 1996, Huggenberger et al. 2002).  A recent genetic study found no differences that would justify a separate Baltic subspecies (Palme et al. 2004).

Synonyms:  Phocoena communis Lesson, 1827; Phocoena vomerina Gill, 1865; Phocoena relicta Abel, 1905; Phocoena phocoena relicta Abel, 1905.

In the Baltic Sea area the historic range apparently included all of the Kattegat/Skagerrak area, the Gulfs of Riga, Finland, and Bothnia, and much of the Baltic Sea proper.   However, in the latter half of the 1900s, the range was reduced considerably, and currently porpoises are considered to be virtually absent in the north-eastern Baltic (Koschinski 2002). 

The abundance of the Baltic Sea stock has been estimated at 599 (CV=57%; 95% confidence interval = 200-3,300) (Hiby and Lovell 1996), of which about 50% or 300 would likely be mature (Taylor et al. 2007). Using a precautionary approach (Wade 1998), a minimum abundance estimate of mature animals would be the lower 20^th percentile of the abundance estimate of mature individuals, equal to 192. Scheidat et al. (2004) reported that on the Oderbank east of Rügen, Baltic harbour porpoise densities between May and August 2002 were high relative to nearby Mecklenburg and Kiel Bights. There is evidence that porpoises in the Kattegat –Skagerrak area migrate to the North Sea (Teilmann et al. 2004).     

Although there are no reliable estimates of pre-exploitation subpopulation size, harbour porpoises were once numerous in the Baltic proper (Kinze 1995).

The Baltic Sea is a semi-enclosed, relatively shallow shelf sea with some deeper basins of more than 200 m depth. There is a gradient in salinity with declining salinity towards east and north. Winter sea-ice normally covers the northern and eastern parts of the Baltic Sea.

In the Baltic Sea and vicinity, herring, sprat, and cod are the main prey items, and many prey species are benthic or demersal (Read 1999, Boerjesson et al. 2003).

Historically, large commercial catches occurred when porpoises migrated through the Danish Straits, mainly during winter and spring months. Annual catch levels averaged about 1,000 porpoises during most of the nineteenth century, increasing to 2,000 at the end of the century with a subsequent declining trend during the twentieth century until catches increased again in the 1940s.  According to Kinze (1995), historical directed catches in the Baltic proper might have been higher than the catches in the Danish Straits.

Today, the most significant threat is incidental catches in fishing nets, primarily various types of gillnets (including both set gillnets and driftnets; Berggren 1994, Koschinski 2002). In addition to gillnets, harbor porpoises are also taken in smaller numbers in trawls (Berggren 1994). The current bycatch, known to be at least seven porpoises per year, is thought to be unsustainable, and Baltic porpoises may become extinct in the near future unless actions are taken to prevent future anthropogenic mortality (ASCOBANS 2000).  Skóra and Kuklik (2003) recorded information on 62 observations of harbour porpoises in Polish waters during 1990-1999. Of these, 45 (75.6%) were reported bycaught in fishing gear, 10 observed at sea and 7 found dead on the shore. The bycatches occurred mostly in driftnets set for salmonids and bottom-set gillnets set for cod. 

The annual bycatch in German Baltic fisheries is assumed to be between 3-5 porpoises (ICES 2005). Eight porpoises in Poland and two in Latvia were reported bycaught in 2003-2004 (ICES 2005). In Finland two porpoises were reported bycaught in the period 1986-1999. No bycatches were reported from Finland after 1999 (ICES 2003).

The species is listed in Appendix II of CITES.

The European Union adopted a Council Regulation 812/2004 entering into force in July 2004. This regulation is aimed at reducing the incidental catch of small cetaceans in fisheries in European Union waters. The regulation includes measures restricting Baltic Sea drift net fisheries, providing for mandatory use of acoustic deterrent devices (pingers) in some EU gillnet fisheries in the Baltic Seas, and the use of onboard observers on vessels of over 15 m in length. Immediate actions to reduce the magnitude of bycatches are necessary. A review of the progress of implementing the regulation was scheduled for 2007.