Phocoena phocoena (LINNAEUS 1758), Harbour porpoise (Phocoenidae)

Compiled by: Dieter Boedeker, Stefan Bräger & Wolfgang Dinter, Germany

1. Description of the habitat/autecology of the species

The harbour porpoise is the smallest cetacean species inhabiting temperate and cold waters throughout the northern hemisphere, mainly in coastal or shelf waters. They grow to an average length of 1.55 meters (males up to 1.43 m and females up to 1.58 m) and a mass of 55 kg (males up to 50 kg and females up to 65 kg), and they can reach a maximum age of 24 years (10-17 normally). Females become sexually mature between 3 and 5 years and they then can generate up to one calf every year. They feed mostly on fish, in the Baltic Sea mainly on herring and sprat[1]. It is known that echolocation is used in the detection and capture of prey[2].

2. Distribution (past and present)

It is believed that there are two distinct populations of harbour porpoises in the Baltic Sea area: one in the Baltic Sea transition area encompassing Skagerrak, Kattegat, the Belt Sea, the Sounds and the Fehmarn Belt (ca. 40,000 individuals); and, a second one in the central Baltic Sea (Huggenberger et al., 2002). Today, specimens of the latter population are extremely seldom observed as they have become very rare (only a few hundred individuals), whereas in the 19^th and early 20^th centuries they were widespread throughout the entire Baltic Proper as far northeast as to the Aaland Islands and the entrance of the Gulf of Finland[3]. The population inhabiting the Baltic marine area differs significantly in genetic composition from that in the North Sea.

3. Importance (sub-regional, Baltic-wide, global)

The Baltic Sea populations of the harbour porpoise are considered to be of Baltic-wide importance in the HELCOM area. In the EU marine area harbour porpoises enjoy strict protection, because they are not only listed in Annex II, but also in Annex IV of the EU Habitats Directive. The species is also part of the “Agreement on the Conservation of Small Cetaceans of the Baltic and North Seas under the Bonn Convention (ASCOBANS)”. Further, the Baltic Sea States have agreed in HELCOM Recommendation 17/2 to protect the harbour porpoise in the Baltic marine Area.

4. Status of threat/decline

The harbour porpoise population in the Baltic Marine Area has declined markedly over the past 100 years and there are indications that the subspecies is facing extinction (classified as Vulnerable (Vu A1cd) under the IUCN Red List 2002).

5. Threat/decline factors

Porpoises are threatened by a variety of anthropogenic activities and impacts. Among these, by-catch in fisheries is of greatest concern (Vinther 1999, ASCOBANS 2000). Other threats in the Baltic Marine Area include pollution, acoustic disturbances, shipping, prey depletion due to over-fishing, and possibly also electric and magnetic fields created by marine cables. Another potential threat is the future construction and operation of offshore wind farms  through direct noise impact, habitat destruction, or prey disturbance (Boedeker et al. 2002).

6. Options for improvement

ASCOBANS obliges its Contracting Parties to engage in habitat conservation and management, surveys and research, pollution mitigation and public information. With the Jastarnia Plan (ASCOBANS 2002), ASCOBANS has set an interim goal of restoring the population of harbour porpoises in the Baltic Sea to at least 80% of its carrying-capacity. In order to fulfil this aim, by-catch reduction is the highest priority, and measures to achieve such reduction should begin immediately. Further, the EU asks for the deployment of observers in certain fisheries to validate the use of pingers, and to record by-catch as well[4]. A control mechanism for the termination of drift-netting in the Baltic Sea is still needed.

7. References

ASCOBANS 2002. Recovery Plan for Baltic Harbour Porpoises (Jastarnia Plan). Bonn, Germany, 2002: 26 pp.

ASCOBANS 2000. Agreement on the Conservation of Small Cetaceans of the Baltic and North Seas. Proceedings of the third meeting of parties to ASCOBANS. Bristol, UK, 26–28 July 2000.

Boedeker D., Benke H., Norden Andersen O., Strempel R. 2002. Marine Mammals. Environment of the Baltic Sea Area 1994-98). BSEP 82b: 171-173.

Huggenberger S., Benke H., Kinze C.C. 2002. Geographical variation in harbour porpoise (Phocoena phocoena) skulls: support for a separate non-migratory population in the Baltic Proper. Ophelia 56 (1):1–12.

Koschinski S. 2002. Current knowledge on harbour porpoises (Phocoena phocoena) in the Baltic Sea. Ophelia 55 (3): 167-197.

Read A.J. 1999. Harbour Porpoise – Phocoena phocoena (Linnaeus, 1758): 323-355 in: Ridgway SH, Harrison R (eds.) Handbook of Marine Mammals, Vol. 6. Academic Press, San Diego & London.

Vinther M. 1999. Bycatches of harbour porpoises (Phocoena phocoena L.) in Danish set-net fisheries. Journal of Cetacean Research and Management 1 (2):123–135.

[1] http://www.imma.org/porpoise.html

[2] http://www.arkive.org/species/ARK/mammals/Phocoena_phocoena/

[3] http://www.ascobans.org/index0201.html

[4] EU:regulation 812/2004 states: "Member States shall design and implement monitoring schemes for incidental catches of cetaceans using observers on board the vessels flying their flag and with an overall length of15 m or over, for the fisheries and under the conditions defined in Annex III."