Identification of beaked whales at sea can be difficult, especially of juvenile animals. Northern bottlenose whales are perhaps the most easily recognised due to their large size (adults can reach up to 9.8 m in length),robust body and prominent bulbous forehead and beak.They have a brown/olive colour and a prominent falcate dorsal fin located two-thirds of the way along the back (with adults often being mistaken for minke whales if the bulbous head is not seen).The pectoral fins are paddle shaped and sit into grooves on the flanks of the body. The data collected includes observations, relative abundance, search for and range of Beaked Whales recorded from marine mammals observations on board ships of opportunity between 2005 and 2011.

The fin whale is Irelands most common large baleen whale and grows to a maximum body length of 24 m in the north Atlantic. Body colour is grey with a white underside. The head is v-shaped with a prominent rostrum in front of the blowhole. Jaw-colour is asymmetrical with the right lower jaw being white in colour and the left being grey, this is diagnostic for the species. A pattern of light and dark grey chevrons is noticeable behind the head in good light conditions. The dorsal fin is prominent and located two-thirds of the way along the back. It is variable in shape, though typically falcate or triangular. The species produces a tall columnar blow up to 6 m high which is very noticeable. The blow can sometimes appear angled if the animal blows while surfacing from depth. This species almost never flukes or breaches in Irish waters. Lunge feeding at the surface is sometimes seen off the south coast. The data collected includes observations, relative abundance, search for and range of Fin Whale (Balaenoptera physalus) recorded from marine mammals observations on board ships of opportunity between 2005 and 2011.

Striped dolphins have a maximum body length of 2.6 m.They are a sleek dolphin species with a slender beak,similar in shape to common dolphin but slightly smaller.A falcate dorsal fin (dark grey in colour) is located half-way along the back. The body coloration consists of a dark grey cape extending from the beak to behind the dorsal fin. The flanks are a lighter grey, leading to pink-white undersides.A thin dark stripe runs from the eye to the anus (between the grey and white areas), while a broad dark band runs from the cape, just below the dorsal fin and tapers to a point on the flanks above the pectoral fins. The striped dolphin is a fast active swimmer which sometimes bow-rides, but not as frequently as the common dolphin, which it resembles in body size and shape. The data collected includes observations, relative abundance, search for and range of Striped Dolphin (Stenella coeruleoalba) recorded from marine mammals observations on board ships of opportunity between 2005 and 2011.

Blue whales are the largest whale species in the world and the largest animal which has ever existed, reaching a maximum length of 33 m. Calves are born at up to 7 m in length. Body colour is blue-grey, mottled with grey, white or silvery patches. The dorsal fin is tiny in comparison to the animal, roughly triangular in shape and is set three-quarters of the way along the back.The head has a broad, flattened, u-shaped rostrum.A single raised ridge runs from almost the tip of the rostrum to the very prominent splash-guard around the blowhole. Blue whales typically produce a very strong blow, rising in a single thick column 6-12 m high, however this is not a diagnostic feature in Irish waters where fin whales are common. Surfacing sequence is a tall columnar blow followed by a long muscular back and (after a period) the tiny dorsal fin. Approximately 20 % of blue whales fluke when deep diving and this trait is specific to individuals (COSEWIC 2002). The data collected includes observations, relative abundance, search for and range of Blue Whale (Balaenoptera physalus) recorded from marine mammals observations on board ships of opportunity between 2005 and 2011.

The common bottlenose dolphin is one of Irelands most recognisable cetacean species.They have a robust, muscular body shape with an average body length: of 1.9m – 3.8 m.The body colour is grey with a light grey (that can show variations of grey patterns) or white underside.A tall falcate dorsal fin with a broad base sits half-way along the back. Bottlenose dolphins exhibit a moderately keeled tailstock. The head has a short,rounded beak with the lower jaw protruding slightly beyond the upper. A soft mouth line curves upwards at back to give the familiar‘smile’ that is characteristic for this species. They often approach vessels to bow ride in inshore waters and in the Shannon Estuary and frequently display acrobatic activity at the surface. Conversely offshore animals often appear wary of approaching vessels. The data collected includes observations, relative abundance, search for and range of Common Bottlenose Dolphin (Tursiops truncatus) recorded from marine mammals observations on board ships of opportunity between 2005 and 2011.

Grey seals are the largest seal species in Irish waters. Male grey seals are considerably larger than females, growing up to 2.6 m in length. Females grow up to 2 m in length.The coat is dark grey on the back and flanks with a lighter underside and with irregular black mottling over the entire animal. Grey seals have a ‘Roman nose’ shaped muzzle. Newborn pups have a white coat and pups are born approximately one meter in length. The data collected includes observations, relative abundance, search for and range of Grey Seal (Halichoerus grypus) recorded from marine mammals observations on board ships of opportunity between 2005 and 2011.

White-beaked dolphins are large,robust dolphins with an average body length of 2.7 m.They have a short but distinct beak which is usually white or light grey. Some animals in the south of their geographical range are reported to have dark or even black beaks. White-beaked dolphins have a very prominent dark dorsal fin mid-way along the back, which is large and sickle shaped.The dorsal fin, flukes and pectoral fins are a uniform dark grey. A distinctive white or pale-grey saddle is present behind the dorsal fin and is characteristic of this species.Two white patches are normally found on the flanks, one either side in front of the dorsal fin and the others on the flank behind the dorsal fin.These patches may merge into the pale saddle behind the dorsal fin. They are strong swimmers, and often swim very energetically along the surface and breach on occasion.They occasionally bow ride vessels, especially larger ships. The data collected includes observations, relative abundance, search for and range of White-beaked Dolphin (Lagenorhynchus albirostris) recorded from marine mammals observations on board ships of opportunity between 2005 and 2011.

Killer whales are the largest dolphin species, with adults reaching up to 9.5 m in length.The blow is low and bushy with a sharp sound, audible from a distance. The head is rounded with an indistinct blunt beak. The triangular dorsal fin, located half-way along the back, is the largest of any cetacean species and reaches 1.8 m in height in males.The dorsal fin on females and juveniles is falcate and more dolphin-like. Body colour is jet-black above and on the flanks. They have white undersides with a white patch above and slightly behind the eye and a white patch stretching from the underside onto the flanks. A lighter coloured saddle patch varies in colour from white to grey to brownish. Identification at sea is easy if the group contains an adult male, which they almost always do, as there is no mistaking the male dorsal fin. Even females and sub-adults have a noticeably larger dorsal fin than other species. The striking body colouration is also diagnostic. The data collected includes observations, relative abundance, search for and range of Killer Whale (Orcinus orca) recorded from marine mammals observations on board ships of opportunity between 2005 and 2011.