Hobbies And Interests
Hunting
In the 1900s, whales meant huge profits to deep sea fishermen. From one whale, 120 barrels of oil could be produced. Fishermen improved the numbers of catches by perfecting whale catching techniques and they used harpoons for spearing the giant beast. Their population was cut down to 1 percent of its original size. The thick layer of blubber on a blue whale is to keep it warm, but humans have found multiple other uses for the tissue. It is used for the production of fuel, oil, soap and candles. Their baleen was used to make brushes and corsets rather than filter krill for the animal's food. Hunting has been the biggest downfall of the population of this species due to the financial gains humans can make from their bodies. It is no longer considered a problem due to the ongoing efforts of worldwide conservation efforts.
Noise Pollution
Rather than sight, blue whales use echolocation to determine their location and direction. This ultrasonic noise helps guide them along and avoid objects and swimming in shallow waters. When the navy tests equipment underwater, the sound and vibration can create interference that confuses the whale, sometimes causing them to beach themselves or get hit by ships. Being struck by ships is now the biggest threat to the blue whale population. In 2007, three blue whale fatalities were confirmed to be caused by collisions with ships. The problem has gotten so serious that the National Oceanic and Atmospheric Association (NOAA) is attempting to lower boat speed limits and consolidate shipping routes to reduce a ship's chance of encountering a whale.
Environmental Pollution and Degradation
Chemicals such as pesticides and oil are a serious problem for blue whales. These toxins collect in the fat stores of adult whales and contaminate a nursing cow's milk. Environmental pollution leading to an increase of ocean water temperature has several negative effects on the well-being of blue whales. The warmer water harbors the growth of viruses, parasites, and toxic algae, and it also accelerates the melting of the glacial ice that provides krill with their diet, phytoplankton. Because krill make up a large portion of the blue whale diet, the melting ice has an effect on this life cycle.
Fisheries
Fishing nets and other gear pose a problem to the blue whale due to the risk of entanglement and injury. Whales caught in nets can break free with the net still attached and later become strangled or unable to swim properly, mate or eat. The harvesting of krill reduces the blue whale's food supply. Krill is used as a food for humans and their pets and livestock, as well as an ingredient in dietary supplements. When they are overfished in an area, the whales nearby are left with a depleted food source.
Natural Causes
Because it takes so long for blue whales to naturally replenish their own numbers, they have problems keeping their population established when so many of them are killed by unnatural and human causes. It takes a year for a pregnant blue whale to give birth and a decade or more for a new blue whale to reach sexual maturity. Once a whale is able to, it is still hard-pressed to find a mate, since the populations are so sparse and widespread. Blue whales in the northern hemisphere never come into contact with those in the southern hemisphere, meaning they have to mate separately in a small, limited gene pool.