Did you know?
- Porpoises and dolphins communicate with each other by squeaking, growling, moaning, clicking and whistling. They also use ultrasonic sound for echolocation.
- Dolphins are often regarded as one of Earth’s most intelligent animals!
- Dolphins are social, living in pods of up to 12 individuals.
- Dolphins can establish strong bonds between each other which leads them to stay with injured or ill individuals.
- Dolphins teach their young how to use tools, such as breaking sponges off and covering their snouts with them so as to protect their snouts while foraging.
- Dolphins not only have a tendency to be playful towards humans, they have been known to protect people from sharks by swimming circles around them.
- Play is an important part of a dolphin’s life. They can often be observed playing with seaweed or play-fighting with other dolphins!
Impact of Commercial Fishing on Dolphins
Even though the U.S. does not actively hunt dolphins for food, a large amount of dolphins inadvertently get caught in U.S. commercial fishing nets. In some parts of the world, dolphins are considered food and are hunted with harpoons and nets.
Whales, like all mammals, breathe air into lungs, are warm-blooded, feed their young milk, and have some hair.
Did you know?
- Males are called bulls. Females are called cows. The young are called calves. A social group of whales is called a pod.
- Unlike fish who breathe using gills, whales breathe through blowholes, located on the top of the head.
- Some whales can stay underwater for up to two hours holding a single breath!
- The Blue Whale is the largest mammal and can boast a length of up to 105ft long and a weight of up to 150 tons! The smallest whale is the dwarf sperm whale which grows to be just 8.5 feet long.
- Whales generally live for 40-200 years, depending on their species.
- Whales are the closest living relatives of hippos!
- Many whales migrate each year, from cold water feeding grounds to warm water breeding grounds. Gray whales make the longest migration of 12,500 miles each year!
- Some whales can swim up to 30 miles per hour!
- Whales receive sound through their lower jaw. They communicate with each other, keep track of offspring and locate prey by other using lyrical sound. Due to their size and strength, some sounds are extremely loud and can be heard for many miles!
- Females give birth to a single calf each year. Nursing time can be more than one year. Most calves stay with their mother for typically 7 to 10 years thereafter. The few number of offspring coupled with the length of time the calf is weaned, provides each calf with a high probability of survival in the wild.
Impact of Commercial Fisheries on Whales
Unfortunately, whale populations are decreasing for several reasons. Not only are several species of small whales caught as bycatch in fisheries for other species, some countries actually hunt whales for food. In 1986, the International Whaling Commission introduced a six-year moratorium of all commercial whaling. The moratorium has not yet been lifted, but for various reasons Norway, Iceland, Japan, and native communities of Siberia, Alaska, and northern Canada are excepted from the moratorium.
Whale populations are also decreasing because of the use of sonar. The U.S. Defense department has been ordered by the U.S. Courts to strictly limit use of its low frequency sonar during peacetime, as some researchers feel that higher frequencies of sonar harm whales. The European Parliament has requested that EU members refrain from using the powerful sonar system until an environmental impact study has been carried out.
Also, as global warming causes the Antarctic Ocean to warm, whale food sources are reducing dramatically which will inevitably have an effect on whale survival rates.
While sea lions and seals look pretty much the same, both having long front flippers and long sleek bodies, they are different in two ways:
- Sea lions have small ear flaps on each side of the head, whereas seals just have tiny opening for their ears.
- Sea lions are able to rotate their hind flippers forward to help them move on land. Seals cannot do this, and must wriggle, roll, or slide to get out of the water and to move around on land.
Did you know?
- A group of sea lions and/or seals in the water is called a raft. Males are called bulls and females are called cows.
- Male sea lions can range from 150 lbs to the over 2200 lbs!
- Sea lions and seals live for 30-40 years.
- During the breeding season, males roar loudly and continuously to establish or defend their territories.
- Females bark loudly so that their pups can pick their mothers out from among hundreds of sea lions.
- Sea lions/seals can dive up to 600 feet and stay submerged for up to 40 minutes!
- Most sea lions eat fish, squid, crabs and clams but the largest sea lion, the steller sea lion, also eats seals.
- Sea lions and seals can swim up to 25 miles per hour.
- Sea lions and seals have long whiskers. Each whisker is loosely attached to the upper lip where it is rotated around with the underwater currents to help locate any food swimming nearby.
Impact of Commercial Fisheries on Sea Lions and Seals
Unfortunately, not only do sea lions and seals get caught in fishing nets, in some areas, sea lions and seals are shot by fishermen who blame them for damaging their nets.
Did you know?
- Manatees are slow moving, non-aggressive, and generally curious creatures.
- They can weigh up to 1200 lbs and reach up to 10 ft in length!
- The manatee’s closest land relative is the elephant.
- On average, most manatees swim about 3 to 5 miles per hour. However, they have been known to swim up to 20 miles per hour in short bursts.
- Half a manatee’s day is spent sleeping in the water.
- Manatees must surface for air regularly, but they have been known to stay submerged for up to 20 minutes at a time!
- Well known for their gentle, slow-moving nature, manatees have also been known to body surf or barrel roll when playing.
- Manatees can live up to 60 years.
- They have a large upper lip that is used to gather food, as well as for social interactions and communications of emotions such as excitement and fear.
- Manatees are believed to have the ability to see in color.
- Researches have found that manatees may use taste and smell, in addition to sight, sound, and touch to communicate.
- Manatees are capable of understanding tasks, show signs of complex learning and demonstrate long term memory.
Impact of Commercial Fishing on Manatees
Though hunting manatees was banned in 1893 and manatees have few natural predators (sharks, crocodiles, killer whales and alligators) manatees are listed by the World Conservation Union as vulnerable to extinction. The current main threat to manatees in the United States is being struck with boats or slashed by propellers.
Sea turtles are characterized by a large, streamlined shell and non-retractile head and limbs. They may be olive-green, yellow, greenish-brown, or black.
- Sea turtles do not have ears or teeth!
- Sea turtles can see well under water but are shortsighted in the air.
- Sea turtles are found in all the world’s oceans, except the Arctic.
- Sea turtles have an extraordinary sense of time and location. They are highly sensitive to the Earth’s magnetic field and use it to navigate.
- Leatherbacks have the longest migration of all sea turtles. They have been found more than 3,000 miles from their nesting beaches.
- Sea turtles range from 25 in. long and 85 lb. to 6 ft long and 2,000 lbs!
- The leatherback is the only sea turtle that does not have a hard shell, instead it has several bony plates beneath a leathery coat.
- Most researchers believe that sea turtles have an acute sense of smell in the water, allowing them to locate food even in murky water
- All eight species of sea turtles are listed as threatened or endangered on the U.S. Endangered and Threatened Wildlife and Plants List.
- Some sea turtle species enjoy floating on the ocean’s surface, napping and/or sunbathing. Sometimes, birds will perch on their shells while the turtles do this!
- Some sea turtles can live 80 years!
The Convention on International Trade in Endangered Species of Wild Fauna and Flora (CITES) protects all species of sea turtles. The U.S. and 115 other countries have banned the import or export of sea turtle products.
Sea turtles help sustain our ecosystem in two very important ways:
1) They fertilize it. Sea turtle eggs contribute nutrients to dune vegetation. As sea turtle numbers decline and fewer eggs are laid, less nutrients are deposited into the sand dunes which results in beach erosion due to lack of vegetation.
2) They maintain it. Sea turtles are one of the few creatures that eat sea grass. Sea grass must be kept short to remain healthy, and beds of healthy sea grass are essential breeding and development areas for many species of fish and other marine life.
Impact of Commercial Fishing on Sea Turtles
Thousands of sea turtles drown in shrimp nets each year because sea turtles forage in the same waters where commercial shrimpers trawl. Caught in a fisherman’s net, they are unable to go to the surface to breathe and suffocate to death in the net.
The good news is that since 1989, federal law requires that a Turtle Excluder Device (TED), a metal grid trapdoor inside a trawling net that allows turtles to escape nets, be installed on the nets of all U.S. fishing trawlers working in areas populated by sea turtles.