Harbour porpoise (Phocoena phocoena (Linnæus, 1758))

The harbour porpoise throughout time has been recognized as the only native species in the German Bight.

For the NE (SH) coast Mohr (Reference Mohr1962) reported on the species providing qualitative data whilst Goethe (Reference Goethe1983) and Meyer (Reference Meyer1994) compiled similar records for the period 1840–1989 for the NI (SW) coastline.

The species, now supported by quantitative data, is regarded as an indigenous inhabitant of the entire North Sea. Quantitatively, this status within the German part of the North Sea only became well-established by the late 1980s when annual stranding numbers became available in conjunction with the set-up of dedicated stranding networks in the various federal states.

The total number of stranding records for the years 1990–2017 was 3764. While the numbers for SW (NI) exhibit an increase over time, indicative of a shift in distribution to the south, the NE (SH) figures fluctuate. Figure 2 provides an overview of the annual number of harbour porpoise strandings for NI and SH, respectively, for the period 1990–2017.

Fig. 2. Number of harbour porpoise strandings 1990–2017. NI (SW) = federal state of Niedersachsen (south-western component), SH (NE) = federal state of Schleswig-Holstein (north-eastern component).

The harbour porpoise used to be seasonally abundant in the lower reaches of all major rivers discharging into the German Bight, but due to increased pollution occurrences probably ceased totally in the mid-1990s.

For German rivers historical records are known from the River Elbe at least since 30 December 1651 (newspaper report in Extra Ordinari Mittwochs Postzeitungen CCCIV, 8 January 1652) and the River Weser as early as 2 April 1670 (Poppe, Reference Poppe1882). Subsequent occurrences also include the River Rhine (1885, city of Emmerich (le Roi & von Schweppenburg, Reference le Roi and von Schweppenburg1909), River Ems (de Fries & Focken, Reference de Vries and Focken1881), and the River Eider (August 1863, city of Tönning; newspaper report Vestslesvigsk Tidende, 10 August 1863).

A recolonization of the Elbe and the Weser rivers by the species has occurred, most likely caused by the significant habitat improvements of recent decades (Wenger & Koschinski, Reference Wenger and Koschinski2012), while re-entrances to the lower River Eider may have been hampered though not entirely blocked by the construction of the Eider Barrage in 1973.

White-beaked dolphin (Lagenorhynchus albirostris Gray 1846)

The white-beaked dolphin is the second most frequent cetacean species encountered along the German North Sea coastline with altogether 64 strandings since 1920 (Appendix 1). While peaking in the 1990s, fewer strandings have been recorded during the last two decades (Figure 3).

Fig. 3. Records of white-beaked dolphins.

Occurrences prior to 1980 only account for six records exhibiting several decadal gaps and therefore may be under-represented due to confusion with the bottlenose dolphin. There are specimens of Lagenorhynchus albirostris most likely originating from the German North Sea coastline in the collections of several European museums (e.g. the Vienna Natural History Museum) purchased as ‘Tursiops tursio’. The first definite German North Sea record of this species is from Büsum (NE (SH)) and in the year 1921 but was, however, not recognized as such until 1970 when van Bree (Reference Van Bree1970) corrected Mohr's (Reference Mohr1935) original species assignment ‘Tursiops tursio’ i.e. bottlenose dolphin. For the NE segment, Dahl (Reference Dahl1894, Reference Dahl1906) listed both the common dolphin (Island of Amrum without year specified) and the bottlenose dolphin (without details). Since for both these species quotations no diagnostic details were provided, it cannot be ruled out that they may have been finds of white-beaked dolphins instead. Tursiops tursio in sensu Mohr (Reference Mohr1935) hence is to be regarded synonymous with the white-beaked dolphin. Therefore, doubt must be cast on several other records of Tursiops tursio listed in her work. Pohle (Reference Pohle1941) considered Tursiops tursio (i.e in sensu Mohr = Lagenorhynchus albirostris) as ‘the other native species’ in German North Sea waters (see Appendix 1).

Bottlenose dolphin (Tursiops truncatus (Montagu, 1821))

Altogether there are 31 records of T. truncatus documented between 1836 and 1998 (Figure 4). Until the 1920s, river occurrences predominated while the most recent occurrences solely have originated from the south-western component of the German North Sea coast (SW (NI)).

Fig. 4. Records of bottlenose dolphins.

The occurrence of the bottlenose dolphin, as pointed out above, may have been blurred due to the confusion with both the white-beaked dolphin (van Bree, Reference Van Bree1970) and the harbour porpoise (Wiepken & Greve, Reference Wiepken and Greve1876).

The bottlenose dolphin possesses the highest riverine affinity second only to the harbour porpoise and has been documented for all major German riverine systems.

River Eider: In early March 1843, a school of 10–12 dolphins was sighted at Friedrichstadt at the confluence of the River Treene with the River Eider (NE (SH)). The estimated lengths (8–10 Danish feet; 2.5–3.1 m), the general behaviour and the school size fit both the white-beaked and the bottlenose dolphins, while the riverine and in-land locality only makes the latter species plausible (Danish newspaper Berlingske Tidende, 14 March 1843).

River Elbe: During the 19th century the species was documented for the year 1852 near Winsen (NI) (Poppe, Reference Poppe1882), 1860 near Glückstadt (SH) (Mohr, Reference Mohr1935), 1867 from an unspecified Lower Elbe locality (based on a specimen in the Copenhagen Zoological Museum), between 1875 and 1876 near Wittenberge (federal state of Brandenburg) (Erhardt, Reference Erhardt1937), in May 1879 at the confluence of the River Stör with the Elbe (SH) (Häpke, Reference Häpke1880; concerning a female and her newborn calf) and in 1924 from almost the same locality yet another animal (Wegener, Reference Wegener1924).

River Weser: In December 1836, an individual was caught at Drielake, Oldenburg (NI) (Wiepken & Greve Reference Wiepken and Greve1876, Reference Wiepken and Greve1897) while a ‘large dolphin’ was reported by Häpke from the town of Celle (NI) in the River Aller tributary to the Weser. Poppe (Reference Poppe1882) reported on an animal taken in 1852 in the Hunte, a tributary of the Weser.

Coastal records include a stranding near Wilhelmshaven (NI (SW)) in 1872 (Möbius, Reference Möbius1888). Schultz (Reference Schultz1970) listed two records of Tursiops from the NE (SH) Wadden Sea area (erroneously with reference to Mohr (Reference Mohr1935) but apparently based on photographic evidence in the Hamburg Mohr archive). Both records are from September 1935 and the Islands of Hooge (SH) and Nordstrand (SH), respectively. Mohr (Reference Mohr1961) under ‘false cover’ provided evidence on yet another specimen stranded on the island of Trischen (SH) without specified date.

Kompanje (Reference Kompanje2001) gave a comprehensive summary of Dutch strandings and found a marked decline in occurrence. By about 1975, the species here was reduced to the status of straggler. To the north, along the adjacent Danish coastline there has been an absence of the species since 1968 (Kinze, Reference Kinze1995). Our findings agree well with the general riverine and southern warmer-water distribution known for the species and possibly the bottlenose dolphins formerly occurring along the German North Sea coast thence formed part of the Dutch Zuiderzee population (Kompanje, Reference Kompanje2001).

Atlantic white-sided dolphin (Lagenorhynchus acutus (Gray, 1828))

The Atlantic white-sided dolphin was recorded seven times from the German North Sea, the first time in 1968, a single find from the island of Schillig, SW(NI) (Goethe, Reference Goethe1983), while of the remaining six records five originate from the south-western (NI) coastline (all but one from the month of April) and a single from the north-eastern (SH) coastline from the month of September (Figure 5).

Fig. 5. Records of white-sided, common and striped dolphins.

Common dolphin (Delphinus delphis Linnæus, 1758)

The application of the name ‘Delphinus delphis’ also in the German literature has been a matter of great confusion. A species under this heading was ubiquitously listed for German waters, but with no specific records ever provided. Without certainty, whether the present-day species was meant, these records must remain dubious. Dahl (Reference Dahl1894, Reference Dahl1906) reported ‘Delphinus delphis’ from the island of Amrum, a record doubted by Mohr (Reference Mohr1935) who believed most German records of ‘Delphinus delphis’ instead to be bottlenose dolphins. However, as van Bree (Reference Van Bree1970) established, she confused bottlenose dolphins with yet another species: the white-beaked dolphin. Poppe (Reference Poppe1882) listed ‘Delphinus delphis’ from the SW coast with reference to Heineken (Reference Heineken1837) who, however, also listed the species without any supportive evidence.

The first genuine record of the common dolphin originates from the SW coast and the year 1958 (Goethe, Reference Goethe1983) with 12 subsequent records (Figure 5).

The common dolphin during certain periods enters the southern North Sea, presumed to be indicative of an influx of warmer water. Fraser (Reference Fraser1937) reported such an earlier occurrence during the 1930s while Kompanje (Reference Kompanje2005) and recently Smeenk & Camphuysen (Reference Smeenk, Camphuysen, Broekhuizen, Spoelstra, Thissen, Canters and Buys2016a) reviewed the trends in occurrence along the Dutch coast.

Striped dolphin (Stenella coeruleoalba (Meyen, 1833))

The striped dolphin was documented for the first time in 2006 near Büsum (NE (SH)), a single record adding a new species to the list of cetaceans recorded from German North Sea waters (Figure 5). The natural distribution area of the striped dolphin is both further south and further offshore than German coastal waters. Two Danish North Sea records were presented by Kinze et al. (Reference Kinze, Schmidt and Tougaard2000) and Kinze et al. (Reference Kinze, Thøstesen and Olsen2018), respectively, while adjacent Dutch records were reviewed by Kompanje (Reference Kompanje2005) and Smeenk & Camphuysen (Reference Smeenk, Camphuysen, Broekhuizen, Spoelstra, Thissen, Canters and Buys2016b).

Already in 1910, however, Trouessart (Reference Trouessart1910) had reported ‘Prodelphinus euphrosyne’ from near the mouth of the River Elbe. The source of his record is unfortunately unknown. Mohr (Reference Mohr1931) doubted this occurrence, quoting Brohmer (Reference Brohmer1914), as did Schultz (Reference Schultz1970) although citing Tomelin (Reference Tomelin1967) for this information. A misinterpretation of Möbius (Reference Möbius1873) so-called ‘Gestreifter Delphin’ (literally = striped dolphin), referring to two finds of Risso's dolphin near Büsum in 1873, seems evident.

Risso's dolphin (Grampus griseus (Cuvier, 1812))

The first and hitherto only record from the German North Sea coast originates from the year 1873 (Figure 6).

Fig. 6. Records of Risso's dolphins, long-finned pilot whales and killer whales.

Two individuals of this species were found in February within two days of each other near the town of Büsum NE (SH) (Möbius, Reference Möbius1873). The literal translation of the German vernacular name ‘Gestreifter Delphin’ is striped dolphin and may have caused a confusion with Stenella coeruleoalba.

Long-finned pilot whale (Globicephala melas (Traill, 1809))

The long-finned pilot whale was documented eight times (Figure 6). The first reported record of the species originates from the year 1965 and the island of Sylt (Gewalt, Reference Gewalt1971). Three finds were registered for the SW coast (1976, 1988 and 2017) and five for the NE coast (1965, 1974, 1995, 1999, 2001), respectively.

The long-finned pilot whale is an oceanic teuthophageous species and therefore probably poorly adapted to the coastal habitat and in particular to the Wadden Sea coast – alike sperm whales. Unlike these, they are much smaller and therefore may have escaped detection in earlier decades.

Killer whale (Orcinus orca (Linnæus, 1758))

Between 1841 and 2016 nine strandings of killer whale have been documented (Figure 6). Dahl (Reference Dahl1894, Reference Dahl1906) and Mohr (Reference Mohr1931, Reference Mohr1935) listed the earliest documented find (1841) from the island of Sylt (NE (SH)). Other older records of the species include an individual stranded on the shores of the island of Juist NI around World War I (Schultz, Reference Schultz1970) and another killed upstream in the Elbe at Fliegenberg (NI) in 1921 (Hentschel, Reference Hentschel1921).

The species was further encountered both for the SW coast (Juist 1943; Wangerooge 1956; Borkum 1967) and the NE coast (Sylt 1965, 2016; Föhr 1988), respectively. It is noteworthy that the 1943 killer whale was reported as a ‘Nordkaper’, a German vernacular name confusingly also in use for the fin whale and the North Atlantic right whale

Beluga whale (Delphinapterus leucas (Pallas, 1770))

Records of stranded dead belugas are rare due to the pronounced coastal adaptability of the species. Individuals often enter rivers and migrate upstream. Accordingly, the only German North Sea stranding hitherto reported was of a beluga whale found dead on the Island Rhinplatte in the vicinity of the town of Glückstadt (SH), i.e. some 100 km upstream in the River Elbe in 1993. Here, we include another record recovered from an unequivocal newspaper report: a 5 m individual found on the island of Föhr (SH) in 1905 (Neue Hamburger Nachrichten, 17 August 1905) (Figure 7).

Fig. 7. Records of beluga whales, narwhals, Sowerby's beaked whales and northern bottlenose whales.

Although the beluga whale is an arctic coastal species, during certain periods invasions seem to take place into more southern coastal waters, namely also the North Sea. In 1984 an individual swam up the River Elbe near Hamburg, and subsequently appeared in the Jadebusen and Dollart at the mouth of the River Ems (Jensen et al., Reference Jensen, Kinze and Sørensen1987; Goethe, Reference Goethe1996). Already in 1967, another beluga had swum 400 km up the Rhine to Bad Honef (Gewalt, Reference Gewalt1976).

There is a very doubtful old record of the species from the River Elbe near Hamburg for the year 1736. The only source here seems to be Mohr (Reference Mohr1935) who quoted Japha (1919 sic!; a reference not contained in her reference list) to have quoted Klein (Reference Klein1741) for this record, but Klein reported on a 1736 narwhal only. Schultz (Reference Schultz1970) as well lists a beluga for this year with reference to another Mohr paper (Reference Mohr1962) which, however, again only refers to a narwhal. This record therefore has been deleted from the list.

Narwhal (Monodon monoceros Linnæus. 1758)

There are two historical records of the narwhal, one from the Dollart in 1669 (SW, NI; Hartmann 1930) and another from 1736 and the mouth of the River Oste, a tributary to the Elbe (R Elbe, NI; Klein, Reference Klein1741. Mohr, Reference Mohr1931, Reference Mohr1962) (Figure 7).

Mohr (Reference Mohr1931) at first believed that two individuals had been taken during 1736, but in 1935 she considered only a single occurrence of a male in early February of this year. Donndorff (Reference Donndorff1792) on the other hand provided a different month (December) and Tomelin (Reference Tomelin1967) reported the specimen to be female. Recently, Haelters et al. (Reference Haelters, Kerckhof, Doom, Evans, Van den Neucker and Jauniaux2018) reviewed extralimital occurrences of the species in the North Sea.

Sowerby's beaked whale (Mesoplodon bidens (Sowerby, 1800))

Records of this species have been extremely rare with only four finds from the German North Sea coast (Figure 7). The two earliest finds are both from the island of Sylt: 1962 Rantum and 1970 Morsum (Schultz, Reference Schultz1970; Kühlemann, Reference Kühlemann1983). In 2009, there were two reports of the species from two adjacent localities, but in different federal states. Careful analysis of photographs documents them as two independent records. Also, during 2009 there were two North Sea live strandings: first 13 August on the English coast near Blakeney Point on the northern shores of Norfolk (which subsequently was found dead), then later 4 October 2009 on the Dutch coast near Masvlaake. The latter specimen was not re-encountered and may be identical with one of the German North Sea strandings.

Northern bottlenose whale (Hyperoodon ampullatus Forster, 1770)

This large beaked whale was recorded seven times (Figure 7) comprising nine individuals in total. For the year 1659, Mohr (Reference Mohr1935) reported on the earliest bottlenose whale find from Blankenese on the banks of the River Elbe to the west of Hamburg. To this we add from the island of Föhr (SH) a catch of two individuals during the summer of 1780 (Danish newspaper report Kiøbenhavns Kongelig alene priviligerede Adresse-Contoirs Efterretninger, 9 August 1780). The species identity of the latter record rests on the vernacular Danish, German and Dutch names applied, the size of the two individuals, the season of the catch and the obvious reference to the bottlenose whale account delivered by Chemnitz (Reference Chemni(t)z1779).

Marshall (Reference Marshall1896) listed it as one of the more commonly occurring species and mentioned several contemporaneous finds (i.e. the 1890s) exhibited in public, but unfortunately without providing any details. Recently, an additional find from the early 20th century has been identified from a photograph and newspaper reports of an individual stranded on Langeoog (NI) in 1902 (Schmidt, Reference Schmidt2014, Neue Hamburgsche Zeitung, 28 August 1902).

For the year 1913 a well-known find from Freiburg (upon Elbe, NI) hitherto erroneously was considered a stranding of a single male. Correctly the incident, however, instead involved a mother-calf pair (Neue Hamburger Zeitung 13 September 1913). A single record is known from Memmert (NI) in 1938 (Goethe, Reference Goethe1983). In 1976 there was a stranding near Büsum (SH) and another in 1981 from Süderoogsand (SH) (Borkenhagen, Reference Borkenhagen2011).

Sperm whale (Physeter macrocephalus L. 1758)

Due to the immense size of this toothed whale, sperm whale strandings can be traced back in time further than any other large cetacean. The earliest known German North Sea sperm whale stranding dates back to 1604. In total, 21 strandings of at least 59 individuals have been documented (Figure 8). Here we include a hitherto overlooked sperm whale stranding from the Eider estuary from early 1695. Subsequent strandings have occurred in the 18th century in 1721, 1723 (18 animals), 1738 (3 animals), 1751 (3 animals, scattered), 1759 (2 animals) and 1762 (≥2 animals). From the 19th century there are no safe records. A presumed sperm whale stranding from 1848 on the island of Borkum (Vanselow & Ricklefs, Reference Vanselow and Ricklefs2005) did not meet the criteria for an unequivocal species identification and was not included in the list compiled by Smeenk & Evans (Reference Smeenk and Evans2018).

Fig. 8. Records of sperm whales.

The gap in records between 1762 and 1969 for the German North Sea strandings is in accordance with findings from the entire North coastline. Smeenk & Evans (Reference Smeenk and Evans2018) reviewed sperm whale stranding for the entire North Sea area while Pierce et al. (Reference Pierce, Santos, Smeenk, Saveliev and Zuur2007) proposed a relationship between strandings and fluctuations in sea temperature.

Minke whale (Balaenoptera acutorostrata Lacepede, 1804)

The minke whale was documented 16 times in total between 1669 and 2017 (Figure 9). For the period 1990–2017 it ranked the most commonly encountered baleen whale with an overwhelming preponderance for the NE (SH) coastline. Records from the SW (NI) coastline include Beichle et al. (Reference Beichle, Stede and Pasenau2005).

Fig. 9. Records of minke and sei whales.

The species was originally known as the Balaena rostrata of Fabricius, 1780, but has frequently been confused with its homonym Balaena rostrata, Müller, 1776, a junior synonym of the northern bottlenose whale. Therefore, Poppe (Reference Poppe1882) erroneously listed an undisputable minke whale of 1669 (a life-size oil painting in the town hall of Bremen; Goethe, Reference Goethe1983) as a bottlenose whale.

Prior to 1971, the only German record known for this species originated from Leesum, the River Weser and the year 1669 (Goethe, Reference Goethe1983). Here, a record from Hooksiel and the 1830s originally considered a fin whale (Wiepken & Greve Reference Wiepken and Greve1876), we re-assign to minke whale. Mohr (Reference Mohr1935) reported a ‘fin whale suckling’ on exhibit in Hamburg in early 1932. This animal stranded near Cuxhaven at the mouth of the River Elbe and was reported to be 7–8 m in length. Based on newspaper photographs (e.g. in Der gerade Weg, 3 April 1932) we re-identify it as a minke whale.

Sei whale (Balaenoptera borealis Lesson, 1828)

Only two records of this species were documented from the German North Sea coastline: in 1955 on the island of Norderney (NI) (Goethe, Reference Goethe1983) and recently in 2016 near Blexen (NI) at the mouth of the River Weser (Figure 9).

Due to its pelagic habitat the sei whale is a very rare visitor to the shallow parts of the North Sea. However, further sei whale specimens may be found among collected rorqual specimens 7–10 m in length that were entered to scientific collections under an incorrect species heading. The 2016 Blexen specimen was identified morphologically (baleen colour) and molecularly (DNA analysis) to sei whale (Ralph Tiedemann, pers. com.).

Fin whale (Balaenoptera physalus (Linnæus, 1758))

Twenty-one fin whale records have been documented, spanning from 1827–2012 (Figure 10) indicating a preponderance in occurrence on the Sylt coasts (SH) (N = 8) and among these finds for the List Deep between the islands of Sylt and Rømø (Denmark).

Fig. 10. Records of fin, blue and humpback whales.

Unfortunately, the fin whale was known by both the German vernacular names ‘Nordkaper’ and ‘Grönländischer Wal’, also being in use for the North Atlantic right whale (Eubalaena glacialis) and the Greenland right whale or bowhead whale (Balaena mysticetus), and even the killer whale (Orcinus orca) thereby causing a lot of confusion (see above). In the 18th century fin whales were listed under the species heading Balaenoptera musculus (Companyo Reference Companyo1830) therefore in later reviews (e.g. Schultz, Reference Schultz1970) erroneously were considered records of blue whale.

Here, we establish the correct species assignment of a 75-feet female ‘Walfisch’ from the island of Helgoland found in November 1849 to be a fin whale (archival evidence: Claudius in lit., 28 August 1857 to J. H. Blasius; Appendix 1). This stranding was erroneously considered a record of Balaena mysticetus, the Greenland right whale by von Dalla Tore (Reference von Dalla Torre1889) based on Oetker (Reference Oetker1855). Mohr (Reference Mohr1931) after Dahl (Reference Dahl1894, Reference Dahl1906) gave the year as 1805 (an obvious printing error for 1850) for the same incident.

Of Wiepken & Greve's (Reference Wiepken and Greve1876) two records of fin whale (Hooksiel 1830s, Wilhelmshaven 1870), only the latter record could be validated as belonging to the species while the Hooksiel record has been re-identified as minke whale. Newspaper reports revealed a further two fin whale strandings near Cuxhaven for the year 1882, and the species has also been documented from the island of Sylt in 1911 by Mohr (Reference Mohr1931).

Both World War I and II unfortunately produced fin whale casualties due to collisions with sea mines. During August 1915, another two large baleen whales, possibly fin whales, washed ashore on the west coast of Amrum (SH) and the island of Pellworm (SH), respectively. A possible third fin whale stranding occurred in July 1943 as a ‘headless’ rorqual was found on the Juister Riff (NI).

Blue whale (Balaenoptera musculus (Linnæus, 1758))

For the German North Sea coastline, the blue whale still only has been encountered once in 1881 on the island of Sylt (SH) (Möbius, Reference Möbius1885) (Figure 10).

While the fin whale during the latter half of the 19th century unfortunately was known as Balaenoptera musculus (Companyo Reference Companyo1830) a homonym of the present day scientific name of the blue whale (Balaenoptera musculus (Linnæus, 1758), the blue whale during the same period carried a variety of scientific names including Sibbaldius borealis Gray 1864 and Pterobalaena gigas Van Beneden 1861. Some 19th century records of ‘Balaenoptera musculus’ in literature therefore refer to fin whales instead and sometimes even are listed twice, both correctly as fin whales and incorrectly as blue whales (e.g. Schultz, Reference Schultz1970).

Further, Meyer (Reference Meyer1994) erroneously reported a minke whale as ‘blue whale’. This stranding supposedly occurred on the island of Neuwerk on12 December 1984, but indeed it is identical with a find the previous day on exactly the same location of a minke whale.

From the adjacent North Sea there are just three additional validated records: a Belgian (1827) and a Dutch (1840) one (Smeenk & Camphuysen, Reference Smeenk, Camphuysen, Broekhuizen, Spoelstra, Thissen, Canters and Buys2016c) and a single 1907 record from the Danish North Sea coast (Kinze, Reference Kinze, Baagøe and Jensen2007).

Humpback whale (Megaptera novaeangliae (Borowskii, 1791))

The humpback whale was reported thrice only, in 1824 at the mouth of River Elbe (Mohr, Reference Mohr1935) and a single specimen, 1991 in the Jade inlet, and in 1994 an individual floating in the German Bight (Stede et al., Reference Stede, Lick and Benke1996) (Figure 10).