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Living Creatures on the Giant

As many individual minke whales in the St. Lawrence are very regularly seen within a season as well as over years, types, occurrence patterns, and changes of parasites can be well documented. While some parasites might actually feed on the whale, others might only attach in order to be carried through nutrient rich waters.

There are two species of parasites, the sea lamprey and pennella sp., which are quite regularly seen on the St. Lawrence minke whales. They intrude the whales body surface to feed on its blood, body liquid and body tissue. Attachments are mostly on the flanks, especially between the dorsal fin and the tailstock, and at the head.

Sea Lamprey (Petromyzon marinus)

It is quite common to find parasitic living sea lampreys attached to minke whales in the study area. Based on body shape, size (> 0.5 m), two distinct dorsal fins and the bluish-brown colouration our study suggests that all attachments documented on minke whales involved Petrymyzon marinus, the only lamprey species known to occur in Canadian Atlantic waters and the St. Lawrence.

Although documented on other cetaceans such as finback, blue, humpback and right whales as well as harbour porpoises, researchers only hypothesized that the attachments actually indicated active feeding. Photographic evidence of lampreys attached on our minke whales however has proven that the parasite actually opens the body surface of the host.

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Copepod (Pennella sp.)

Although photographically well documented among our minke whales, we have not yet quantified and analysed our data in respect to the occurrence of what’s thought to be pennella sp, most likely pennella balaenopterae. However, such parasites seem to appear to attach quite regularly and to stay on for long periods.

Hosts are infected by free-living larval stages intruding the whale’s skin to embed the head in the blubber layer. The rest of the growing body and the egg case hang loose outside the body. These parasites, which might grow up to 32 cm in length, might remain attached for weeks or even months until reproduction and release of eggs is completed.

Cookie-cutter shark (Isistius brasiliensis)

These small sharks of about 50 cm in length are recorded from various areas around the world where they occur in the deep water of tropical oceans believed to live as deep as 3500 m. Countercoloured like many marine creatures, it can additionally illuminate part of its ventral body surface to lure or ambush potential prey.

Attacking its prey this carnivore first creates a strong vacuum to attach itself to the prey’s skin. It then swivels its large saw-like teeth to cut deep into the body. Then it twists and turns itself vigorously to rip out a cookie-shaped piece of flesh, leaving a wound often twice as deep as wide. During their diel vertical movement they might at night raise to water depths of several hundred meters only which are also frequented by its prey; large fish, whales and dolphins.

Although we have not seen any fresh wounds on our minke whales, white and oval marks at various stages of healing are regularly visible and are believed to be caused by cookie-cutter sharks. As no cookie-cutter sharks live in the cold waters of the St. Lawrence we believe that minke whales might be attacked in their breeding grounds.

Xenobalanus globicipitis

Quite commonly these planton-filtering barnacles can be seen on the trailing edges of pectoral fins, dorsal fins and tail flukes of cetaceans. They use their star-shaped footplates to attach on their hosts, which carry them into nutrient rich waters.

Although described to occur on minke whales in other areas, we have so far never seen such barnacle attachments in the St. Lawrence Estuary.