You don’t have to travel far abroad to watch small whales. After decades of absence, harbor porpoises, the only whales resident in German waters, have come back to the coasts of Lower Saxony. Increasingly often they also enter large rivers.
Especially in the spring time chances are good that you can spot a harbor porpoise, even from land, for example in the ports of Bremerhaven and Wilhelmshaven.
Harbor porpoises in the North and Baltic Seas
Harbor porpoises are the only cetacean species living in German waters, where they also give birth to their young ones. The calving season usually lasts from May to early July. An important calving ground near Sylt in the North Sea has already been declared a protected area. It is the only cetacean sanctuary in Germany.
While harbor porpoises are still quite abundant in the North Sea, they are endangered in the Baltic Sea, where they form several subpopulations. The one in the eastern part counting only some several hundred individuals is at risk of extinction due to bottom-set gillnets and drift nets.
GRD’s harbor porpoise sighting scheme
Since 2007 we have obtained harbor porpoise reports from the Weser and Elbe rivers each year. These harbor porpoises do not represent vagrant individuals entering the rivers, but they are following a target: prey.
Based on our data analysis harbor porpoises must be considered as part of the biocenosis of these rivers. They enter the rivers each year during a certain period of time. The observed behavior -the harbor porpoises’ upstream migrations- belongs to the natural behavioral pattern.
To protect the small cetaceans in the large rivers like Elbe or Weser and enable them to reproduce in this area, we started cooperating with the local conservation authorities in 2006, setting up a sighting and reporting program to identify the precise harbor porpoise range in the Rivers.
The results of my data collection on the distribution of harbor porpoises in the rivers has now became the basis that shows that harbor porpoises enter the estuaries and lower river sections regularly in the spring and have again become part of the ecological community.
The period from approximately mid-February through mid-June must be considered as particularly sensitive because this is the time their upstream migrations take place and because there is evidence that the porpoises start to reproduce in Mai/June.
It is my assessment that harbor porpoises will occur regularly in the Jade, Weser, and Elbe rivers in the years to come. However, human interference in this habitat, such as ramming or excavating work, may prevent them from coming to these areas or may disturb them in other ways.
According to the EU Habitats Directive, the harbor porpoise is a protected species and any projects interfering with its habitat must be subject to environmentally feasibility studies; harbor porpoises must be taken into account in any environmental impact assessment.
We are already seeing our work bear some fruit in the Weser. Our data have been incorporated in several plan approval procedures; three projects had to shift their intended ramming work to less sensitive months owing to the occurrence of harbor porpoises and twaite shads.
Just recently, we have been able to provide the German environmental organization NABU Schleswig-Holstein with our Elbe river data which NABU will use to prepare an assessment on the occurrence of harbor porpoises in the Elbe river with respect to the planned Elbe river deepening and to sue over the contested river deepening together with other environmental groups.
Legal protection of harbor porpoises
In earlier centuries harbor porpoises were widespread along the coasts of northern Europe and Germany, but direct hunting until the 1950ies has greatly reduced their numbers. Pollutants and accidental by-catch in fishing nets are additional factors that have significantly reduced their populations. At the coast of Lower Saxony a decrease in important prey fish like herring and mackerel is probably the cause for the dwindling numbers of harbor porpoises in the 1960ies.
In 1984, harbor porpoises came under the protection of the Convention on the Conservation of Migratory Species (CMS); in 1993, the Agreement on the Conservation of Small Cetaceans of the North and Baltic Seas (ASCOBANS) came into force.
In 1992, the EU’s Habitats Directive was adopted to conserve wild fauna and flora and their natural habitats and to create an ecological network of protected areas in order to improve the ecological situation and to enable the return of species (Natura 2000). According to Annexes II and IV of the EU Habitats Directive, the harbor porpoise is among the species that enjoy particularly strong protection.
Protected areas must be designated for such species and, especially in the case of harbor porpoises, threats such as by-catch in the fisheries, marine pollution, and noise pollution must be avoided. Moreover, being a species listed under the Habitats Directive, the harbor porpoise should be taken into account in environmental impact studies for projects affecting its habitat. The "no deterioration requirement" applies.
These nicely formulated measures on paper must now finally be implemented. To improve the protection of harbor porpoises we need precise and ecologically reasonable specifications. Germany should take an exemplary function in granting its only resident cetacean species calving in German waters strict protection. GRD is intensely lobbying for the protection of harbor porpoises.
According to the literature of the early 20th century, harbor porpoises were regularly seen in large rivers. Then they disappeared due to the impacts of human activities. For three years now we have received an increasing number of reports of harbor porpoise sightings in the Weser, Elbe and Ems rivers. We can only guess why they come back because our knowledge about their stays in rivers is still too scarce. This is why the collection of data is so vital.
It is obvious that the high-traffic waterways of Weser and Elbe do not constitute particularly good habitats for harbor porpoises. Especially fast watercraft pose a threat in the partly very narrow rivers. There are several indications that some of the porpoises’ injuries resulting from ship propeller strikes were a cause of death, rather than having occurred post-mortem.
Pollutants such as heavy metals or pesticides which are still present in our river sediments also pose a threat. Ship traffic and excavations swirl up sediments and may release contaminants as well as pathogenic, anaerobe bacteria into the water which the porpoises may then ingest with the ethereal particles together with the food.
In the long term it is therefore necessary further to improve the water quality and ecology within the framework of the EU Water Framework Directive and to introduce speed limits for speed boats.
The main threats these small cetaceans are facing today are the frequent by-catch in fisheries, a decrease in food due to industrial over-fishing, and the increasing noise pollution in our oceans due to shipping, oil exploration, blasting of underwater unexploded ordnance, and pile-driving, for example for the construction of off-shore wind farms.
Noise can temporarily drive the acoustically oriented marine mammals from certain areas. The noise produced in detonations or by airguns used in resource exploration may also cause severe injury to organs and even be fatal to marine mammals.
As top predators, toothed whales accumulate industrial and agricultural pollutants, which reach the sea via the rivers and have negative impacts on the cetaceans’ fecundity and health.
"Harbour porpoise (Phocoena phocoena Linnaeus, 1758) entering the Weser river after decades of absence":
⇒ Marine Biology Research, Volume 8, Issue 8, 2012
Further articles in English on our project "Conservation of harbor porpoises in Germany" can be found in our member magazine Delphinpost (English concise versions).