Jul 03 2012

Lionfish, Pterois sp. (Characteristics, distribution and habitats, feeding habits and predation style, venom) – Video

This video was taken at Aquarium de la Mer, Sea World, California (USA) in June, 2012

Review: Abdel Rahman El Gamal (Founder of the website and video channel)

Characteristics: Lionfish have distinctive brown or maroon color, and white stripes or bands covering the head and body. Their colorful exterior helps them to blend in well with the coral reefs where they are mostly found. An adult lionfish can grow to about 0.3 – 0.4 meter in length with a weight that may reach 1.2 kg.  The life span of lionfish may range from 10-18 years in the wild with an average of about 15 years.

Distribution and habitats: Lionfish are native to the coral reefs, mangroves, seagrass and rocky crevices in marine habitats in the warm, tropical waters of the South Pacific and Indian Oceans. Through its introductions especially for aquaria trade, lionfish established itself along the southeast coast of the U.S., the Caribbean, and in parts of the Gulf of Mexico. The dumping of unwanted lionfish from home aquaria provided an access for the species to natural waters in many parts of the world. Lionfish have been found in very shallow waters and also found in waters with about 300 meter depth.

Feeding habits and predation style: Lionfish are carnivores that prey on a wide variety of crabs, shrimp and fish. They catch their prey by hiding in crevices in the rocks or corals waiting for their prey to pass by. Lionfish may corner its prey using its large fins before swallowing it.

Venom: Lionfish fins have sharp spines in their dorsal fins which they use to inject potent venom whenever necessary. It is believed that the fish uses its venom as a purely defensive mechanism, when it feels threatened by its main predators such as large fish and eels. It may worth mentioning that the lionfish is considered as one of the most poisonous fish in the world. A sting caused by the lionfish is very painful to humans and can result nausea, breathing difficulties, and nausea, but is rarely fatal.

Information sources: NOAA, National Ocean Service, National Geographic, http://a-z-animals.com, Buzzle.com

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Permanent link to this article: https://fishconsult.org/?p=4082

Jun 30 2012

Cage farming of gilthead sea bream (Sparus aurata) in Rayaan Depressions, Egypt (Video)

Credit: Course participants in EICA/JICA training course (2011)

Cage farming of gilthead sea bream (Sparus aurata) has been tried recently in Rayaan Depressions in Egypt. The water salinity of the depressions is steadily increasing due to evaporation making the system suitable to marine cages. The stocked fingerlings are produced in private marine hatcheries while the feed is produced in commercial feed mills. Based on the economics of this pilot initiatives, the development of marine cages in the depressions could be determined.

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Permanent link to this article: https://fishconsult.org/?p=3816

Jun 27 2012

Green sea turtle, Chelonia mydas (Description & key biological parameters, distribution range & habitats, and feeding habits) Video

This photo was taken in Monterey Bay Aquarium, USA.

The green sea turtle, Chelonia mydas is the largest species of the Cheloniidae family.

Green sea turtles are named after the green color of their body fat which is green from the plants they eat.

Description and key biological parameters: Green sea turtles are one of the very and few species that watched the evolving and extinction of the dinosaurs many of millions of years ago. Green sea turtles are cold-blooded animals, have scaled skin, and they breathe air.

Like all species of turtles, green sea turtles have a highly developed protective bony outer shell which protects them from predators. While most species of land turtles are able to retract their heads into their shells for extra protection, sea turtles are not able to do so, and their heads remain out at all times.

They are easily distinguished from other sea turtles because they have a single pair of prefrontal scales rather than two pairs as found on other sea turtles.

Size: Adults may measure 80-120 cm in carapace length and weigh between 100-200 kg.

Distribution range and habitats: the green sea turtles are found in all temperate, subtropical and tropical waters of the world’s oceans. They stay mainly near the coastline and around islands and live in bays and protected shores, especially in areas such as coral reefs and rocky shorelines whereas sea grasses and algae are abundant. They are rarely observed in the open ocean.

Feeding habits: feeding habits of green sea turtles change significantly as the green turtle grows. Juvenile green sea turtles are carnivorous as their diet consists of jellyfish, worms, young crustaceans, aquatic insects, grasses and algae. Unlike other sea turtles, adult green sea turtles become strictly herbivores, feeding on sea grass that grows in shallow lagoons. Their finely serrated jaws help them in tearing vegetation. Also, the bacteria that are found in their guts will act on the digestion on plant material. Because of this feeding habit of the adult green sea turtle, they do not pose a threat to other marine animals.

Sources: Earth Justice and variety of records and publications

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Permanent link to this article: https://fishconsult.org/?p=3933

Jun 27 2012

Green sea turtle, Chelonia mydas (Life span & reproduction, respiration, salinity management, and survival threats)

Review: Abdel Rahman El Gamal (Founder of the website and video channel)

Life span and reproduction: green sea turtles seem to grow very slowly and usually reach sexual maturity at the age of 10 – 50 years with an average of about 25 years. Although green sea turtles live most of their lives in the ocean, adult females must migrate from feeding areas accompanied by males to the nesting grounds whereas nest making, mating and egg laying take place. The nests are between 3 to 5 times per season whereas a female lays her egg clutch which consists of about 100 leathery-skinned eggs in each nest before carefully cover the burrow with sand. The incubation period of green turtle eggs is about 60 days. Biologists believe that nesting female turtles return to the same beach where they were born. They may migrate hundreds of miles to the nesting beaches (grounds).

Respiration: during their active time, sea turtles swim to the surface every few minutes in order to breathe. However, adult turtles can remain underwater for more than 2 hours without breathing in resting time. This is attributed to the ability of turtles to withstand higher concentrations of carbon dioxide in their blood than most other air-breathing animals which able them to use their oxygen very efficiently. Similarly, muscles and blood of adult turkey are able to store oxygen in large quantities, allowing them to remain underwater for long periods of time. However, juvenile sea turtles do not enjoy this ability and hence they must sleep afloat at the water’s surface.

Salinity management: there are salt glands located behind each of the turtle’s eyes through which, tears of excess salt are shed from their bodies. Doing so, turtles get rid of accumulated salts from sea waters and hence maintain a healthy water and salt balance in their bodies.

Threats to green sea turtle’s survival: According to the IUCN Red List, the green sea turtle is classified as “Endangered”. The major factors that may contribute to survival of sea turtles could be summarized in:

Illegal harvest and hunting of turtle eggs for food, shells for jewelry making, skin for leather goods, meat for food, and fat for oil

Incidental catch of turtles in commercial shrimp trawlers (the use of turtle excluder devices (TEDs) could save trapped turtles

Marine debris when ingested by turtles by mistake. Plastics are common threat to sea turtles.

Habitat loss or degradation especially in coastal zones which may lead to the loss of nesting places or disturbed by noise, pollution, lights and other symptoms that may accompany human activities.

Predation especially by tiger sharks

Sources: Earth Justice and variety of records and publications

 

 

Permanent link to this article: https://fishconsult.org/?p=3923

Jun 26 2012

Moon Jellyfish, Aurelia labiate (distribution, description & behavior, life cycle, feeding behavior)- Video

This video was taken at Monterey Bay Aquarium

Source: www.fishconsult.org

Moon jellyfish, Aurelia labiata belongs to the genus Aurelia and is a cnidarian of the Ulmaridae family.

Distribution: moon jellyfish are found in most seas in Europe, Japan, and Gulf of Mexico as well as in the Pacific Coast of North America. They live in pelagic habitats and they are often washed up on beaches. It is believed that the species migrates toward the surface during the day and downward at night. They are also in the Atlantic and Indian oceans. The optimum temperature for moon jellyfish is 9-19 °C. Although they are more found in warm and tropical waters, they can withstand much colder waters. In regard to salinity, moon jellyfish can also live in brackish waters with as low salt content as 6 g/l.

Description and behavior: their size ranges from 5-40 cm in diameter. They are characterized by their delicate coloration that is usually an opaque whitish, though sometimes with other colors.  Moon jellyfishes swim by pulsations of the bell-shaped upper part of the animal. Horizontal swimming is essential to keep the animal near water surface.  This way of swimming allows the tentacles to be spread over the largest possible area, in order to better catch food. Moon jellyfish can adapt to the declining of dissolved oxygen in the water through lowering their respiratory rate.

Life cycle: Males and females of moon jellies are sexually distinguished whereas reproduction is sexual.  Eggs develop in the female’s recognizable gonads that lie near the bottom of the stomach. Moon jellyfish females carry young larvae on the inner edges of the oral arms. Most jellyfish of this species die after reproducing while some may live a second year.

Feeding behavior: Moon jellyfish is carnivorous and feeds through capturing small organisms. Their foods include small plankton organisms such as mollusks, crustaceans, tunicate larvae, copepods, rotifers, nematodes, young polychaetes, protozoans, diatoms and eggs. These foods collect chiefly on the surface of the animal, where they become entangled in mucus which is then moved to the mouth by cilia. Food is then moved, again by flagellar currents, along eight separate canals that branch off and run into the stomach. When moon jellyfish gets starved, they can shrink dramatically in size while retaining its functionality.

 Sources: Wikipedia, Walla Walla University and MarineBio

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Permanent link to this article: https://fishconsult.org/?p=3890

Jun 26 2012

Sun-drying of fish in South Sudan

Credit: Juma Frezar (South Sudan)

The two photos show the process of sun drying of fish in South Sudan. The drying is done on wooden structures, wire or robes. During summer, fish drying may require 3-4 days while a longer period (a week or more) may be required in the fall. Nothing is added to fish during the drying process. The second photo which is taken in the fisherman camp at Bentio shows fish on the ground for refreshing only and not drying. The common dried fish species is Nauk (local name); Heterotis niloticus.

Note: We decided not to watermark the photos in order not to upset its clarity. However, we trust you will notify us if you wish to use a picture or more. This is expected and will be appreciated.

 

 

Permanent link to this article: https://fishconsult.org/?p=3900

Jun 25 2012

Marketing of dried fish in South Sudan

Credit: Juma Frezar (South Sudan)

This photo has been taken in the marketing location of dried fish in Bonito City, South Sudan. Dried fish species are usually abundant and available all-year round. Because of the low consumer preference to dried fish compared to fresh fish, its market price is lower than fresh fish. By the end of the day, unsold dried fish is stored in a designated area inside the market in Bantio city.

Note: We decided not to watermark the photos in order not to upset its clarity. However, we trust you will notify us if you wish to use a picture or more. This is expected and will be appreciated.

Permanent link to this article: https://fishconsult.org/?p=3879

Jun 25 2012

Pacific sea nettle (Chrysaora fuscescens) – Video

This video was taken in Monterey Bay Aquarium, USA

The Pacific sea nettle, Chrysaora fuscescens which lives in the Pacific Ocean is a free-floating, large jellyfish with a bell of up to about 30-50 cm across in diameter. It has four long oral arms surrounding its mouth. Sea nettles have bright distinctive colors which make them a popular organism in public aquaria especially they are relatively easy establishment and maintenance. Even though sea nettle spends most of their time passively floating on water surface, they are capable to swim against currents.

Distribution: The Pacific Sea Nettle, Chrysaora fuscescens is commonly found along the coasts of Oregon and northern California, flourishing in late summer and fall. The significant abundance of the sea nettle in the recent years has been claimed to be due to climate changes and/or human activities in the coastal regions.

Feeding behavior: Sea nettle feeds on a wide variety of zooplankton, crustaceans, pelagic snails, other jellyfish, small fish as well as their eggs and larvae. Case studies show that when sea nettles are found in high densities, they may negatively affect fish populations and they may also become nuisances to fisherman by clogging up fishing nets.

Sea nettles are carnivore organisms. As their prey passes by and brushes up against their tentacles, thousands of nematocysts are released, launching pointed stingers which release a paralyzing toxin into the prey which are transported by the oral arms into the sea nettle’s mouth for digestion.

Reproduction: Sea nettle is capable of both sexual and asexual reproduction. Its life cycle begins by the fertilization of female’s eggs through catching the sperm released by the males. Afterwards, fertilized eggs are hold in female’s mouth attached to her oral arms. As fertilized eggs grow into flat bean-shaped planula and then after they grow into flower-shaped polyps whereas they are released into the ocean where they attach themselves to a solid surface and undergo metamorphosis as they grow, developing a bell, arms, and tentacles until it is a fully formed medusa.

Risks: As sea nettles use their stingers in capturing and paralyzing their prey, they may also sting human who comes in contact with them. Such stings may cause considerable pain, irritation and discomfort. However, these stings rarely require medical attention.

References: Wikipedia and Encyclopedia of life

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Permanent link to this article: https://fishconsult.org/?p=3864

Jun 15 2012

Giant Pacific Octopus Enteroctopus dofleini (feeding behavior and predation)

This photo was taken on 9 June, 2012 at: Monterey Bay Aquarium, California, USA

Feeding behavior: This octopus hides in its den under rocks or in a cave. By night, an octopus leaves its den to hunt after its favorite prey such as crustaceans, small crabs, scallops, abalone, snails, clams and fish. Octopuses in general when feed on hard-shelled prey may crack shells and pull it apart, bite it open with their beak or drill through the shell. Octopuses may create a tiny hole in the prey shell. Through this hole, octopus secretes and injects a toxin (venom) that paralyzes their prey to be ready for consumption.

Predation: The predation on octopus is always done by marine mammals such as Harbor Seals, Sea Otters, and Sperm whales which depend upon the Giant Pacific Octopus as a source of food. When octopuses got threatened, they often try to escape by releasing an ink cloud and change their own color. The ink is toxic and so if the octopus cannot escape their own ink (or water is not changed quickly when held in an aquarium), they will become ill or perhaps die. Changing skin color is activated by contracting or expanding pigment cells (chromatophores) in the skin in an attempt to match the background color through the adjustment of the three colors which exist in three bags located in pigment cells.

References: Giant Octopus: Fact Sheet; Aquaria poster; Wikipedia; Marinbio

Note 1: We decided not to watermark the photos in order not to upset its clarity. However, we trust you will notify us if you wish to use a picture or more. This is expected and will be appreciated.

Note 2: More information on this species is available in two posts in the video library on this site

 

Permanent link to this article: https://fishconsult.org/?p=3852

Jun 15 2012

The Giant Pacific Octopus, Enteroctopus dofleini (Life history and conservation status) – Video

This short video was taken on 09 June, 2012 at Monterey Bay Aquarium, California, USA

Life history: The Giant Pacific Octopus is a short-lived animal, with life spans of 3-5 years. When sexually mature, females may lay 20,000 – 100,000 eggs over a period of several days. Eggs are intensively cared for by the females until they hatch after an incubation period of 150 days to seven or more months, depending on the temperature. Newly hatched young have the size of a rice grain. Females do not feed while tending eggs and die when the eggs hatch or shortly thereafter. The mature male of giant octopus deposits a long spermatophore of more than 1 meter which is a characteristic of the octopuses in this genus.

The newly hatched young of the giant octopus swim toward the surface and spend 4-12 weeks drifting in the plankton until their mantle length is >14 mm whereas the young then settle to the bottom while their average weight is still under 5 grams.

Conservation Status: The Giant Pacific Octopus is not currently under the protection of CITES or evaluated in the IUCN Red List

References: Giant Octopus: Fact Sheet; Aquaria poster; Marinebio; Wikipedia

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Permanent link to this article: https://fishconsult.org/?p=3828

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