Adult humpbacks range from 11-16 m in length, with females being slightly larger than males. The head is broad with a series of fleshy knobs on rostrum (and sometimes on the lower jaw), called tubercles. Body colour is black with white on the throat and belly. The pectoral fins are extremely long (one-third of the body length) with scalloped leading edges. They are typically white in colour but may have a dark upper surface, with white beneath.The tail fluke typically has a dark upper surface with white beneath, however the under-surface can be dark in some individuals. The scarring, colour pattern and shape of each tail fluke is unique and provides for identification and tracking of individuals. The dorsal fin is small with a broad base, raised hump in front and "knuckles" behind. The blow is typically low and bushy and has a distinct V-shape when viewed from directly behind or in front of the animal. The data collected includes observations, relative abundance, search for and range of Humpback Whale (Megaptera novaeangliae) recorded from marine mammals observations on board ships of opportunity between 2005 and 2011.

Long-finned pilot whales are very large and robust dolphins with an average body length of 6.7 m for males and 5.7 m for females. A low bushy blow is often visible and quite audible when in close proximity to the animals.The head is bulbous, with a very short and poorly defined beak.The bulbous melon is quite prominent in males and may overhang the beak. The dorsal fin is located slightly before the half-way point along the animal’s back and is large, with a very broad base and rounded at the tip. The pectoral fins are long,sickle-shaped and pointed at the tip. Long-finned pilot whales are black in colour with a white anchor-shaped throat patch and white belly patch. Some animals display a paler grey saddle patch behind the dorsal fin. Calves are lighter in colour and often appear to have a brown tinge. Long-finned pilot whales can be very active at the surface and commonly breach, tail slap and spy-hop. The data collected includes observations, relative abundance, search for and range of Pilot Whale (Globicephala melas) recorded from marine mammals observations on board ships of opportunity between 2005 and 2011.

Sperm whales are Irelands most widespread and abundant deep water whale species and indeed may be the most abundant large whale species within the Irish EEZ. They have a maximum body length of 15-18 m.The body profile is characteristic, with a large square head with and under slung jaw.The head forms one-third of the overall body length. There is no true dorsal fin, but two-thirds of the way down the back is a raised dorsal hump and beyond this are a series of 4 or 5 knuckles.The pectoral fins are short and stubby, but the tail flukes are broad and powerful.The scarring and shape of each tail fluke is unique and provides for identification of individuals. Body colour is typically dark grey to brown. There are often white blotches on other parts of the head or body.The skin on the head is frequently patterned with circular scars formed by the suckers of giant squid on which the whales feed. They have a short bushy blow which is angled forward and slightly to the left (caution: the blows of other species may appear similar when surfacing at an angle).The blow sequence is characteristic with logging animals blowing every 20-30 seconds. The breathing rate increases as the animal prepares to dive. The data collected includes observations, relative abundance, search for and range of Sperm Whale (Physeter macrocephalus) 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.

Minke whales grow to an average body length of 8.5 m. Body colour is dark grey with a white underside and lighter patches of grey extending up the flanks in a variety of patterns. Brilliant white bands are evident on the upper surface of both pectoral fins and are often visible even when the animal is below the surface. The head is sharply pointed and v-shaped with a noticeable rostrum in front of the blowhole.A prominent, falcate dorsal fin is located two-thirds of the way along the back.The blow is diffuse and usually not visible, though it may be seen and/or heard in very calm conditions. The dorsal fin usually appears simultaneously with the blowhole.This species almost never flukes and rarely breaches, however some spectacular displays of breaching have been observed in Irish waters and animals may breach continuously for prolonged periods. The data collected includes observations, relative abundance, search for and range of Minke Whale (Balaenoptera acutorostrata) 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.

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.

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.