Dr. Stefan Harzen Archives | Taras Oceanographic Foundation

Common Dolphins – Basic Knowledge

2021-04-11 tarasfoundation Dolphins, Oceans, Science, Threats

PHYSICAL DESCRIPTION: Common dolphins are colorful, with a complex crisscross or hourglass color pattern on the side; the long-beaked common dolphin being more muted in color. When looking at the profile of the two common dolphin species, the short-beaked common dolphin has a more rounded melon that meets the beak at a sharp angle, as compared to the long-beaked common dolphin that has a flatter melon that meets the beak at a more gradual angle.

COLOR: Color patterns on the common dolphin are the most elaborate of any cetacean. The back is dark gray-to-black from the top of the head to the tail dipping to a V on the sides below the dorsal fin. The flanks are light gray behind the dorsal fin and yellowish-tan forward of the dorsal fin, forming an hourglass pattern. Its belly is white. There are large dark circles around the eyes connected by a dark line that runs across the head behind the beak and a black stripe runs from the jaw to the flippers.

FINS AND FLUKES: The dorsal fin is triangular-to-falcate (curved). It is pointed and located near the middle of the back and is black-to-light gray in color with a black border. The flippers are long and thin and slightly curved or pointed depending on geographical location. Flukes are thin and pointed at the tips with a slight notch in the center.

LENGTH AND WEIGHT: Common dolphins can reach lengths of 7.5 to 8.5 feet (2.3-2.6 m) and weigh as much as 297 lb. (135 kg). The short-beaked common dolphin is relatively heavier, and has a larger dorsal fin and flippers than the long-beaked one.

FEEDING: Delphinus delphis feeds on squid and small schooling fish. In some parts of the world, they feed at night on the deep scattering layer, which moves towards the water’s surface during that time. Common dolphins have been seen working together to herd fish into tight balls. Like many other dolphin species, the common dolphin will sometimes take advantage of human fishing activities (such as trawling), feeding on fish escaping from the nets or discarded by the fishermen.

MATING AND BREEDING: Sexual maturity is reached at 3 to 4 years of age or when they reach 6 to 7 feet in length (1.8 to 2.1 m). Calves are 30 to 34 inches at birth (76 to 86 cm ); gestation period is 10 to 11 months.

DISTRIBUTION AND MIGRATION: The common dolphin may be one of the most widely distributed species of cetaceans, as it is found world-wide in temperate, tropical, and subtropical seas. The long-beaked common dolphin is found more in coastal waters; the short-beaked common dolphin is found in offshore waters, including the Eastern Atlantic Ocean as far south as Florida. The common dolphin throughout history has often been recorded in art and literature. It was recently proposed that two forms of this species, the short- beaked (delphis) and long-beaked (capensis) common dolphin, represent two distinct species.

NATURAL HISTORY: Like all mammals, dolphins are warm blooded, breathe air, give birth to live babies, feed their new born milk, and are born with hair. Being warm, blooded, or homeothermic, dolphins maintain a constant body temperature regardless of the surrounding water temperature. Unlike terrestrial mammals, including humans, dolphins are conscious breathers, meaning they must be aware of their breathing to avoid involuntarily taking a breath while underwater. Common dolphins can dive for as long as 15-20 minutes but typically hold their breath for only a few minutes. Common dolphins may live for 35 years or more, with females generally living longer than males. Common dolphins are often found in large herds of hundreds or even thousands. They are extremely active, fast moving, and engage in spectacular aerial behavior. They are noted for stampeding in these extremely large groups across the ocean, riding bow and stern waves of boats, often changing course to bow ride the pressure waves of fast-moving vessels and even large whales. Common dolphins can be frequently seen in association with other marine mammal species.

THREATS: Traditionally, hundreds of thousands of common dolphins have been taken incidentally, along with spinner and pan-tropical spotted dolphins, in purse seine nets used during tuna fishing operations in the eastern tropical Pacific although these numbers have improved. Common dolphins also may be caught accidentally in other fishing gear, such as midwater trawls. Turkish and Russian fishermen used to catch large numbers of common dolphins in the Black Sea for meat (to be used for fish meal) and oil. The fishery stopped after the common dolphin numbers became and remain severely depleted; there are several reports suggesting that the Turkish fishery may have recently resumed. Many common dolphins are taken in a Japanese small cetacean fishery and directly caught in the Mediterranean. Some common dolphins have been taken in Peru for human consumption. Studies suggest that the immune system of these animals can be severely affected by heavy metals, PCBs and other pollutants. The status of common dolphins, relative to OSP, in the U.S. Atlantic Eastern Economic Zone (EEZ) is unknown. The species is not listed as threatened or endangered under the Endangered Species Act. There are insufficient data to determine the population trends for this species.

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We all depend on a healthy ocean; a healthy ocean depends on us. Let us be the change we would like to see in the world. Our new Ocean Sentinels Club is proof that conservation can be fun, rewarding and effective. The Club unites and empowers citizens to advocate for the conservation of dolphins and the marine environment across Palm Beach County, and beyond. Join us. The time is now. It begins with you.

Archaeocetes

2021-02-26 tarasfoundation Dolphins, Ocean Sentinels Club, Science, Whales

Well, we can’t exactly tell you what archaeocetes were, but we can tell you what they were not. They were not filter-feeders like the baleen whales (mysticetes), and they had no form of echolocation, as the toothed whales (odontocetes) do. There are very few clues, but we believe they are not categorized by any unique characteristic.

We know they lived from 50 to 35 million years ago (the eocene period) after which they somewhat abruptly disappeared (geologically speaking, that is). Evidence of their existence has been found in all parts of the world. Archaeocetes probably spent some time on land, and some time in shallow coastal waters, feeding in the tidal zone. There is some debate about whether or not the archaeocetes were the evolutionary predecessor to the odontocetes and mysticetes, but either way there is no doubt that the odontocetes and the mysticetes flourished once the archaeocetes disappeared.

Research has shown that two separate families of cetaceans existed then: the Protocetidae were small-bodied animals, less than 3meters long (9 feet), with their nostrils just behind the tip of their long, slender snout and their teeth not unlike those of a wolf. The Basilosauridae was a medium-sized cetacean, ranging in length from 15-20 meters (45 to 60 feet) in length. This was a rather serpentine animal with un-fused vertebrae, allowing for great mobility in all directions. They had a defined rostrum, but no melon (bulge on the front of their head), and small hind, somewhat useless, legs. They were foragers and lived of fish. It is believed that they hauled themselves out of the water onto beaches to breed, in a way similar to that of seals. The first of these two families disappeared nearly 50 million years ago, and the second family disappeared about 40 million years ago.

Among the archaeocetes were also distinct types of dolphins. Although they were very easily recognized as dolphin in appearance and lifestyle, we would say they both had a very primitive air about them. Both animals were about average in size and used a limited form of echolocation. The Kentriodontids were foragers, similar to the modern-day bottlenose dolphins. The Squalidontids had very long rostrums (beaks) and triangular, serrated teeth (similar to shark teeth). It is believed that they had a very active carnivorous lifestyle, not unlike that of the killer whale. What an interesting appearance they must have had, with their blowhole situated at an odd, forward angle, atop but near the front of their heads. Five or six million years ago both these families disappeared, after sharing the planet for about 25 million years. The reason for their disappearance remains a mystery.

Today, we recognize 14 species of baleen whale including the blue, bowhead, right, humpback, minke and grey whale. Baleen whales are generally larger than toothed whales except for the sperm whale which is very big and has teeth. Depending on the source, tooth whales comprise 69 – 76 species and 6 – 10 families.

The two dolphins most frequently encountered in our study area (off Palm Beach County) are the bottlenose dolphin. And the Atlantic spotted dolphin, both members of the family Delphinidae.

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We all depend on a healthy ocean; a healthy ocean depends on us. Let us be the change we would like to see in the world. Our new Ocean Sentinels Club is proof that conservation can be fun, rewarding and effective. The Club unites and empowers citizens to advocate for the conservation of dolphins and the marine environment across Palm Beach County, and beyond. Join us. The time is now. It begins with you.

Atlantic Spotted Dolphins -Basic Knowledge

2021-02-21 tarasfoundation Dolphins, Ocean Sentinels Club, Oceans, Science

The Atlantic spotted dolphin is considered playful and acrobatic. They love to ride the bow wave of boats and surf the wake of ships they encounter. They are also more likely to approach humans than other dolphin species and become easily habituated to human activity in the wild, but do not survive in captivity.

PHYSICAL DESCRIPTION
Spotted dolphins are difficult to describe because their size and coloring vary according to their geographic location. Found only in tropical waters, and subtropical waters, there are two recognized species: the Atlantic spe¬cies, Stenella frontalis, and the worldwide species, the pan-tropical spotted dolphin, Stella attenuata. Their long slim beak con¬tains 35 to 48 small conical teeth in each side of the upper jaw and 34 to 47 small, conical teeth in each side of the lower jaw.

COLOR
Spotted dolphins change their coloration as they mature. Newborn calves are dark gray with a white belly (two-tones). As the animal grows older, dark spots begin to appear. First dark spots appear on the lower part of the body (speckled). When sexually mature, light spots begin to appear on the dark upper portion of the body (mottled). Eventually, the spots merge into almost solid color patterns (fused). This color pattern process is a visual indicator of the age of the dolphin.

FINS AND FLUKES
The dorsal (top) fin is tall and curved; the flippers are small and pointed. The flukes are small and pointed at the tips with a small median notch.

LENGTH AND WEIGHT
Length averages about 7 feet (2.1 m); weight averages 220 pounds (100 kg). Calves are 32 to 36 inches (80 to 90 cm) at birth.

FEEDING
Spotted dolphins feed on many varieties of fish and squid found in various water depths. They also feed on small fish and eels found buried in the sand in shallow waters.

MATING AND BREEDING
This species reaches maturity between 6 and 8 years of age or when the animal is about 6.5 feet (2 m) in length. Mating and calving take place throughout the year; the calving interval is believed to be about every 2 – 3 years, but in stressed populations mating takes place at an earlier age and calving at shorter intervals, a response to the enormous mor¬talities suffered from being entangled in nets by the tuna fishery. Gestation is 11 1/2 months and calves are nursed for 11 months. This interval is also longer for male infants, as mothers tend to spend more time caring for the boys. Female calves separate from their mothers earlier and spend a year babysitting the calves of other mothers before becoming mothers themselves.

DISTRIBUTION AND MIGRATION: Atlantic Spotted dolphins are generally found in groups of fewer than 50 individuals but have populations comprising hundreds of animals. These animals are highly social. Schools may contain both sexes and all ages. Some populations are found exclusively in deeper water, some populations prefer to frequent shallow waters, especially for behaviors associated with child care and pregnancy. Atlantic Spotted dolphins are sometimes seen together with bottlenose dolphins.

NATURAL HISTORY
Like all mammals, dolphins are warm blooded, breathe air, give birth to live babies, feed their new born milk, and are born with hair. Being warm, blooded, or homeothermic, dolphins maintain a constant body temperature regardless of the surrounding water temperature. Unlike terrestrial mammals, including humans, dolphins are conscious breathers, mean¬ing they must be aware of their breathing to avoid involuntarily taking a breath while underwater. Atlantic spotted dolphins are capable of diving to up to 60 meters, remaining underwater for up to 6 minutes. They are known to be preyed upon by sharks, but killer whales and other small-toothed whales may also be a threat.
The Atlantic spotted dolphin can often be seen traveling in small pods consisting of up to 15 dolphins. These dolphins enjoy maintaining a high level of social interaction with one another and can often be seen performing leaps and various acrobatic stunts. The Atlantic spotted dolphin communicates using vocal sounds and body language. When it comes to sound these dol¬phins use high-pitched clicks and whistles to communicate about nearby threats, food, a desire to play, and a number of other things. Each dolphin has its own unique frequency which helps them understand who is communicating, and also provides them with a geographic reference (location). This can be extremely useful when a mother for instances needs to keep track of one of her kids or when two friends are communicating with one another in a large pod. Body language is also important for commu¬nication. Dolphins may bump into one another or visualize their body language by spy hopping or leaping out of the water to alert other dolphins of various interests or threats or to display their physical abilities.

THREATS
Spotted dolphins are protected in U.S. waters by the Marine Mammal Protection Act. While the species is not considered endangered, they are, like all marine mammals, exposed to pollutants and biotoxins, and viral outbreaks. Studies of large, high mortality event over the last few decades suggest that the immune system of these animals can be severely affected by heavy metals, PCBs and other pollutants. Atlantic spotted dolphins are not listed as threatened or endangered under the En¬dangered Species Act, and the Western North Atlantic stock is not considered strategic under the Marine Mammal Protection Act. No fishery- related mortality or serious injury has been observed during recent years; therefore, total fishery-related mor¬tality and serious injury can be considered insignificant and approaching the zero mortality and serious injury rate. There are insufficient data to determine the population trends for this species.

We all depend on a healthy ocean; a healthy ocean depends on us. Let us be the change we would like to see in the world. Our new Ocean Sentinels Club is proof that conservation can be fun, rewarding and effective. The Club unites and empowers citizens to advocate for the conservation of dolphins and the marine environment across Palm Beach County, and beyond. Join us. The time is now. It begins with you.

Florida’s Wild Dolphins Reveal Unique Social Feeding Behavior

2021-01-09 tarasfoundation Dolphins, Health & Well-Being, Man's Future, Ocean Sentinels Club, Oceans, Science, Threats

For the last decade, the Taras Oceanographic Foundation, under a general authority of the National Marine Fisheries Service, has been conducting dolphin surveys in Palm Beach County. We position or boat within three miles from shore, and travel at slow speed, until we see dolphins. We will then follow the dolphins long enough to photograph each dolphin and document their behavior. And although we have studied wild dolphins for decades, we still find new and different behaviors that are remarkable.

There are days when bait fish seem to fall fro m the sky. On those special days, when the seas are flat, we watch all kin ds of fish jumping out of the water; some high in the air in a single arc, others low and repeatedly as they travel some distance. Flying fish routinely glide, with ease, for several meters. Ballyhoo and Bonita will jump to avoid being eaten. Every once in a while, a clever dolphin will take advantage of these jumping fish; a clever dolphin like Odyssey, and her offspring.
Odyssey was conducting a master class in the art of catching fish. And when I say ‘catching fish’ I mean CATCHING fish. She was throwing a fish into the air, and artfully catching with in her mouth. She demonstrated the process a few times for her calf, and then did something remarkable.

She bit off the head of the fish, before throwing the body in the air, for her calf to catch. We could not help but make the comparison of a mother cutting the crust off a sandwich, before serving it to her child. But it is more than that; she was keeping her calf safe.
For the significance of this simple act, we need to first ex amine the basic anatomy of a fish. Fish use gills to acquire oxygen from the water. These gills are located just at the base of the head. When a fish breathes, it draws in a mouthful of water and pulls the sides of its throat together, forcing the water through the gill openings, which expand away from the body.

Dolphins do not chew their food. It is imperative, therefore, for a dolphin to swallow their prey, head first. If a fish were eaten tail first, it might expand its gills while passing through the throat of the dolphin and become wedged. In all the necropsies I performed, I once found one dolphin with a fish caught in its throat. The fish was swallow ed tail first, and the res ult was deadly. Back to Odyssey and her calf.
She was biting the heads off the fish, so her calf would not catch the fish backwards and choke to death. She threw the fish body high in the air, and her calf made repeated attempts to make the catch. More likely motivated by the game than the food, the small dolphin was still nursing and probably not too hungry. Over the next few months, as this calf grows, Odyssey will insist it hunt down its own food. The catching strategies learned now, will be all the more important in the future.

But even the best strategies and the most prepared youngster will not grow to be an adult unless there continues to be the abundance and variety of fish to eat. We are currently living through the sixth mass extinction event this planet has experienced. ln the past, these epic occurrences were the result of volcanic eruptions or asteroids striking the earth, but this time they are our own doing.

Why is it important to study dolphins? Sure they are cute and all, but why should anyone support such endeavors? Because in many ways, we are alike. Dolphins eat the fish we eat. They raise their kids to be better citizens and work every day to make a living and support their families. They are the masters of the ocean environment; a subject about which we are remarkably naive. And the ocean is vital to the survival of us both.

Although we continue to harvest the resources the oceans provide, at unsustainable rates, we could learn from the marine mammals how to find areas of highest productivity and hunt selectively. As we increase the noise in the ocean with our recreational watercraft, commercial ships and military exercises, we learn from the dolphins that in the deep ocean, it is by listening and hearing we can have the best vision. Marine mammals are the ocean canaries, warning us about the disastrous effects of pollution and habitat destruction, and they can be our guides to find answers, to questions we have not yet thought to ask about the ocean realm.

It is through the long- term studies like the one we have been carrying out in Palm Beach waters, that dolphins teach us about the ocean, the world and ourselves. We just have to keep going to school.

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We all depend on a healthy ocean; a healthy ocean depends on us. Let us be the change we would like to see in the world. Our new Ocean Sentinels Club is proof that conservation can be fun, rewarding and effective. The Club unites and empowers citizens to advocate for the conservation of dolphins and the marine environment across Palm Beach County, and beyond. Join us. The time is now. It begins with you.

The Objectives of Marine Mammal Research

2020-12-27 tarasfoundation Dolphins, Oceans, Science, Threats, Whales

The aim of marine mammal research is to develop progressive knowledge and understanding of their biology, adaptations, behavior and ecology, which will lead to better protection of species and their habitats, contributing to biodiversity in such a way that a sustainable use of the sea becomes possible. Furthermore, such research strives to understand how we affect their lives and how we can gain from them, e.g. through tourism.

If you understand dolphin echolocation and how it works, then you have the tools to apply that knowledge. If you are a conservationist and are concerned about dolphin entanglement in nets, the knowledge allows you to build better fishing nets that will not harm them. The application of the knowledge depends on what you value: for an academic, to further knowledge and understanding; for an applied researcher, to be able to provide information to managers on the implications of a range of management options, for a conservation biologist: to find ways of ensuring the health of populations.

In the end, all this will contribute to a better understanding of the impact we have on our planet. You can’t have seven billion people growing and running around on a planet without having some major impacts. Right now we are making choices we don’t even understand; better to make an informed choice don’t you think?

There are various tools that can be used to achieve this goal, including expanding the knowledge base through biological inventories, research, monitoring, training of professionals, planning (environmental impact assessment), action plans and integrated area management, regulating threats to marine species and ecosystems, establishing protected areas, and ensuring active involvement of citizens in government decision making. Public education is very important in all conservation efforts.

Most of science consists of answering very small questions. Each one may not have much value in and of itself, but when the whole picture is to be seen, each of the many small pixels of knowledge will be required. So in the long term, we can expect to truly understand some of the things that are affecting cetaceans and their behavior. In the short term, however, one cannot expect too much. Important results in this field are usually gained through long-term research, which will then constitute the wisdom and the power to make the best possible decisions about the future. Research aimed only at solving a specific, well-understood short-term problem is not going to provide us with the answers we need ten or twenty years from now. We need to commit some fraction of our resources, our dollars, to basic science, understanding that it is a risk-taking investment; not all science hunches pay off, but when they pay off, they pay off big. And this investment of resources should not be done because it is `en vogue’ to be concerned about the animals, the oceans and the planet, but because it is intellectually and morally the correct thing to do. By better understanding one group of marine creatures, with which we compete for resources – prey and habitat -, we may be able to better manage our affairs on this planet.

In sum, excellent research provides several results: Firstly, it leads to a deeper understanding of the world and its basic mechanisms of function, or in other words, an increased appreciation of the world in which we live. Secondly, it provides a baseline of data against which we can measure changes and information that can be put to practical use, thus reducing our impact on these animals and their environment. And third, the advancement of knowledge usually entrains an increase in public awareness and then support from the general public, which is a crucial determinant for maintaining biodiversity, the survival of the variety of species and their habitats and a wise resource use by man.

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We all depend on a healthy ocean; a healthy ocean depends on us. Let us be the change we would like to see in the world. Our new Ocean Sentinels Club is proof that conservation can be fun, rewarding and effective. The Club unites and empowers citizens to advocate for the conservation of dolphins and the marine environment across Palm Beach County, and beyond. Join us. The time is now. It begins with you.

Sustainable Development and Biodiversity

2020-12-13 tarasfoundation Biodiversity, Science, Sustainability

Today, the internationally acknowledged basis for agreements on environmental protection, resource management, and conservation, consists of the principles of sustainable development and the maintenance of biodiversity. The concept of sustainable development is based on the realization that the conditions for economic activities will continue to deteriorate in the future, if the natural resources underlying these activities continue to be destroyed at the present rate.

By exploiting non-renewable raw materials, we consume resources as if making withdrawals from a limited saving account, without making deposits. At the same time, our species is using renewable resources above and beyond their regeneration capacity. The earth’s limited absorption capacity is overtaxed by emissions and waste volumes, leading to consequential ecological costs, which can no longer be ignored. A discussion about the fundamental rules involved in our economies is tantamount to a renaissance of nature as a factor in the production-function concept.

The supplies of resources, and the absorption of residuals, both prerequisites for economic activities, are to be seen as irreplaceable functions of nature. The preservation of the capital stock (= natural resources) is a key element of sustainable development. Unlike current approaches, this capital stock should at least be kept at a constant level to prevent future generations from suffering from shortages of natural resources or a deterioration of environmental quality. First and foremost, sustainable development means preserving the vital functions of the environment, including the potential for change, evolution and self-regulation.

Biodiversity is meant to be all-inclusive; it is the genetic-based variation of living organisms at all levels. It includes the world’s millions of species and the ecological systems they live in, ranging from Polar Regions with relatively few species, to the tropics with their great abundance of different life forms. Conserving biodiversity provides us with at least three domains of benefit:

Maintenance of our ecosystems in healthy condition
Source of new pharmaceuticals, crops, fibers etc., all holding economic value
‘Biophilia’, which is a term used by E.O. Wilson to describe the natural affiliation humans have for the natural environment

In the words of paleontologist Niles Eldredge, it is our failure to recognize our connection with the global ecosystem that lies behind the biodiversity crisis facing our planet. We have to recognize that biological diversity is part of our heritage and is incomparably older and more complex than anything else.

Our own single species, out of the 5-30 million species that exist today, consumes nearly half of the total produce from land-based ecosystems, and 25% of all plant energy from the land and sea combined. Today there are less than 1 million elephants, but 100 million cattle on earth. These numbers do not reflect intrinsic worthiness, but rather developed usefulness. And yet, we must confront the demographic realities honestly, if we hope to preserve biodiversity, achieve a sustainable development, and to prevent a massive Sixth Extinction.

Although it may be impossible to determine the exact rate of extinction, estimates are that about 27,000 species are lost each year, which means that three species are lost forever every hour. It is also commonly accepted that there is a relationship between habitat loss and species numbers. Reducing a habitat’s original size by 10% is expected to eventually lead to the numbers of species inhabiting that area dropping by half. Every species that disappears is a loss of evolutionary potential. Human-caused extinction is up between a thousand and ten thousand times over what it was before humans came to Earth. This is far in excess of the rate at which new species are being created. So again, we are quickly running out of the capital that took many millions of years to create.

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We all depend on a healthy ocean; a healthy ocean depends on us. Let us be the change we would like to see in the world. Our new Ocean Sentinels Club is proof that conservation can be fun, rewarding and effective. The Club unites and empowers citizens to advocate for the conservation of dolphins and the marine environment across Palm Beach County, and beyond. Join us. The time is now. It begins with you.

Dr. Stefan Harzen

Common Dolphins – Basic Knowledge

Archaeocetes

Atlantic Spotted Dolphins -Basic Knowledge

Florida’s Wild Dolphins Reveal Unique Social Feeding Behavior

The Objectives of Marine Mammal Research

Sustainable Development and Biodiversity

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