habitat_narrative
Marine
Fin Whales are only known to form large aggregations within feeding grounds or while migrating, but are usually present within schools of up to five individuals. Females with calves usually separate themselves from the rest of the group, and pregnant females are known to arrive at feeding grounds earlier than the rest of the group, and leave earlier towards the end of the season (Skinner and Chimimba 2005). They are the fastest of all baleen whales, and have been recorded swimming at speeds of approximately 20 knots over substantial distances. While feeding, Fin Whales engulf up to 70 tonnes of seawater into an elastic throat pouch, and filter food, in what has been declared the greatest biomechanical action exhibited by any animal (Brodie 1993). Southern hemisphere Fin Whales consume mostly euphausiid prey, but may fortuitously engulf fish simultaneously during feeding.During migrations through waters off Durban to wintering grounds, whales caught had mostly empty stomachs. Only 12.7% contained food, which mostly consisted of euphasid remains (Euphausia recurva and Thysanoessa gregaria), but also amphipods, copepods, needlefish and megalopa larvae (Bannister and Baker 1967). On South Africaâs West Coast (at Donkergat), the stomachs of 35.8% of caught whales held food. Again, the majority were euphasiids (E. recurva, E. lucens, E. spinifera and T. gregaria), and to a lesser degree copepods and amphipods (Best 1967). It is uncertain whether they rely predominantly on blubber for energy during winter, or whether they actively locate food. Results have confirmed that Fin Whales are thinner at the beginning of summer when they return to their Antarctic feeding grounds.
On the contrary, in the northwest Atlantic, Overholz and Nicolas (1979) described Fin Whales feeding on American Sand Lance/Sand Eel (Ammodytes americanus); additionally in waters off Newfoundland, 80â90% of the diet of Fin Whales was thought to consist of Capelin (Mallotus villosus). The inter-annual variability associated with Capelin abundance suggests that Fin Whales probably feed opportunistically on this species when its availability increases.
Following a gestation period of 11 to 12 months, Fin Whale calves are born within temperate and subtropical waters in winter (typically between April and June). Newly born calves are usually around 6.4 m in length, and are generally dependent on their motherâs milk for the first seven months of life, before reaching a length of approximately 11.5 m. Females in the southern hemisphere become sexually mature after reaching a length of 20.0 m, and usually produce a calf every two years, while Northern Hemisphere individuals reach sexual maturity at shorter body lengths (Ohsumi et al. 1958).
Ecosystem and cultural services: Marine mammals integrate and reflect ecological variation across large spatial and long temporal scales, and therefore they are prime sentinels of marine ecosystem change; migratory mysticete whales may be used to investigate broadscale shifts in ecosystems (Moore 2008).
