Jul 28 2012

Tilapia research facilities at Kigembe research station, Rwanda

Credit:  Emmanuel Hahirwabasenga and Rwigiriza Augustin Kanimba (Rwanda)

The two photos show the tilapia research facilities at Kigembe aquaculture research station. The station is located in the Southern part of the Country found at least 25km from the 2nd largest city called Huye. One of the photos shows the tanks used to supply water to nursery ponds. The second photo shows nursing hapas located in nursery ponds for the production of tilapia fingerlings.

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=5056

Jul 26 2012

Hornet tilapia, Tilapia buttikoferi (Description – distribution – feeding – reproduction) – Video

This video was taken at the Sea World, California, USA (June, 2012)

Introduction: Hornet tilapia, Tilapia buttikoferi, which belongs to the family Cichlidae is known by more common names such as Zebra tilapia and tiger tilapia.

Description Hornet tilapia has typical tilapia shape with vertical black color and several yellow stripping extending from the region to their eyes to the base of their tale. Zebra and tiger names have been given based on this pattern of stripping.  The vertical markings tend to fade as the fish grows older. These fish are long-lived cichlids as they can live up to 10-15 years. The hornet tilapia is considered a larger species of cichlids as they commonly grow up to 30-40 cm long. These fish are mid-level swimmers. In general, hornet tilapia is sorted as an aggressive fish species and this characteristic has to be considered when raising this species in aquaria; the species is best suited to mono-species tank. Despite their aggressive behavior they are still reasonably popular with aquarium owners who believe in the high intelligence of this fish.

Native distribution: Hornet tilapia are naturally found in the lower reaches of coastal West African rivers from Guinea-Bissau (Geba and Corubal Rivers) to west Liberia (St. John River) especially  in vegetation-choked rivers which have salinities that range from zero to almost sea salinity at their mouths. Because of aquarium trade, the species has been introduced outside its native range.

Feed habits: Hornet tilapias are similar to other cichlids in regard to their feeding habits. They are omnivores even though they prefer and benefit more from plant-based foods especially blanched vegetables such as lettuce or zucchini. In aquaria, they can be fed on variety of food depending on their age.

Reproduction: Hornet tilapia is a substrate spawner. Broodstock usually dig a hole in the substrate in which eggs are deposited. Both parents generally tend to take care about their eggs. Fry typically hatch in 4-5 days and will become free swimming in about 5 or 6 days.

References: Water Monsters, Total Fish Keeping, Fishbase, Exotic aquariums, Aqua-fish-net

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Permanent link to this article: https://fishconsult.org/?p=5039

Jul 25 2012

California spiny lobster, Panulirus interruptus (Characteristics, distribution, feeding, reproduction, predators)

These two photos were taken at the Sea World, USA in June 2012

Characteristics: The California spiny lobster is one of the largest spiny lobster species, and typically grows to a length of 30 centimeters. Males can weigh up to 12 kilograms and Adults can grow to be more than 2 feet long. Spiny lobsters may live to be about 25 to 50 years old.

Like all spiny lobsters, the California spiny lobster has two large, spiny antennae, but no large claws on its legs. It is characterized by a reddish-brown color with stripes along the legs. The interrupted grooves across the tail are characteristic for the species. California spiny lobsters are nocturnal, hiding in crevices during the day, with only the tips of their long antennae showing, as a means of avoiding predators.

Distribution and habitats: The California spiny lobster, Panulirus interruptus, is found in the eastern Pacific Ocean from Monterey Bay, California to the Gulf of Tehuantepec, Mexico. The majority of the population is found between Point Conception, California and Magdalena Bay, Baja California. The California spiny lobster is found in parts of the Gulf of California, and along the Pacific coast of the length of the Baja California peninsula, extending as far north as San Luis Obispo Bay, California. Although adult lobsters can be found in shallow water, they usually live on rocky substrates from the intertidal zone at depths of 65 meters or more. The juveniles generally inhabit rocky habitats at a depth of 0–4 m with dense plant cover, especially the surf grass.

As stimulated by changes in water temperature, spiny lobsters may carry out an annual offshore-onshore migration, in which they enter shallower water in spring and summer whereas plentiful supply of food exist, while head out to deeper water in fall and winter probably to avoid the effects of winter storms.

Food habits: Because the California spiny lobsters are nocturnal, their feeding activity begins at night when the animals leave their dens to search for their food. Adult lobsters are omnivorous and sometimes carnivorous. They consume algae and a wide variety of marine invertebrates such as sea urchins, snails, mussels, worms, and clams as well as fishes, and injured or newly molted lobsters. Their feeding upon sea urchins is important for maintaining healthy seabed communities.

Reproduction and life history: Females of California spiny lobsters reach sexual maturity at an age of 5–9 years while males are sexually mature after 3–6 years. The spawning takes place from May to August. After mating, the fertilized eggs are carried on the female’s pleopods until they hatch, with between 120,000 and 680,000 eggs carried by a single female. The eggs begin coral red, but darken as they develop to a deep maroon. The eggs become ready to hatch after 10 weeks.

The fertilized eggs hatch into tiny, transparent larvae “Phyllosoma”  which are drifted in the ocean and have to undergo 12 molts that take about 7 months ending by the juvenile stage “Puerulus” that settle to the sea floor. The settled “puerulus” which looks like a miniature adult starts to grow if the habitat is suitable till reaching the adult size.

Lobster’s predators: Lobsters are vulnerable to predation. The natural predators of the California spiny lobster include bony fish such as the California sheep head, giant sea bass, California moray eels, cabezon, horn shark, leopard shark, rock fishes, octopuses and sea otters. California spiny lobster can defend itself against its natural predators through producing a loud noise using its antennae. Also, if a predator is very close, the lobsters will flex their muscular tail in order to escape the predator.

References: Wikipedia, Freebase, Blue Ocean Institute, California Seafood Council, PBS Foundation, All Kayal Fishing.com

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=5027

Jul 23 2012

Preparation of a new site and pond construction by cooperative members at Nyagasambu, Rwanda

Credit:  Emmanuel Hahirwabasenga and Rwigiriza Augustin Kanimba (Rwanda)

This photo shows the site preparation and fish pond construction in a new site at Nyagasambu, Eastern part of Rwanda, about 35km away from the Capital city Kigali. The cooperative members are participating in pond construction and they get paid to be encouraged by the project.

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=5015

Jul 23 2012

Cage farming of Nile tilapia, Oreochromis niloticus in Lake Burera, Rwanda

Credit:  Emmanuel Hahirwabasenga and Rwigiriza Augustin Kanimba (Rwanda)

The two photos show the cage farming of Nile tilapia, Oreochromis niloticus in Lake Burera, Rwanda. The lake is found in the Northern part of Rwanda, near the volcanic mountains. Farmed fish in the cages are regularly sampled and inspected. Fish are fed with commercial feed that meets the nutritional requirements of fish in this intensive system.

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=5007

Jul 23 2012

White whale, Delphinapterus leucas (Reproduction, threat and conservation status) – Video

This video was taken at the Sea World, California, USA

Life history and reproduction

Males reach sexual maturity between four and seven years, while females mature at between six and nine years. The white whales can live more than 50 years.

Female belugas typically give birth to one calf every three years. Gestation lasts 12 to 14.5 months. Calves are born over an extended period of time that varies by location throughout the period from March and September. Newborns calves are uniformly dark grey in color and measures about 1.5 meters long, weigh about 80 kilograms.  The calves remain dependent on their mothers and nurse for about 2 years. As calves grow, the grey color lightens reaching their distinctive pure white color by the age of seven years for females and nine years for males.

It may worth mentioning that almost all white whales found in aquaria are caught in the wild, as captive breeding programs was not that successful.

Threat and conservation status

There are various threats that negatively affect white whale populations. The predation, hunting & human activities and pollution are the key threating factors.

Predation: Polar bears take particular advantage of situations when whales become trapped by ice and cannot reach the ocean. The orca is its other significant natural predator.

Pollution: Because the white whale is a long-lived animal, it is considered an excellent indicator species for environment health and changes. As the white whale congregates in river estuaries, pollution has proved to be a significant health danger.

Hunting and human activities: the data show that the white whale global population is much smaller compared to pre-hunting populations whether hunting was done by indigenous people or through previous commercial whaling.  Also, the disturbance caused by small boats, ships and whale-watching are threatening the whale populations.

Conservation status: As of 2008, the beluga is listed according to IUCN standards as “near threatened”. This classification has taken in consideration the uncertainty about the number of white whales over parts of its range, in addition to the possible qualification of whale population to “threatened” status if the conservation efforts cease, especially hunting management. The white whales are protected under the International Moratorium on Commercial Whaling. It may worth mentioning that sub-populations of while whale may have different conservation listing.

References: Natural history notebook, Wikipedia, Scientific papers

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Permanent link to this article: https://fishconsult.org/?p=4997

Jul 22 2012

White whale, Delphinapterus leucas (Introduction, description, distribution, feeding) – Video

This video was filmed at the Sea World, California, USA (June 2012)

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

Introduction: The beluga whale and white whale are the common names for the Arctic and sub-Arctic cetacean species, Delphinapterus leucas, which belongs to family “monodontidae”.  We preferred to use white whale to avoid confusion with the beluga sturgeon.

Description: The adult white whales are distinguished by their pure white skin while calves are usually gray when born and gradually turn towards white coloration as they grow. Like most toothed whales it has an oily, fatty tissue lump (distinctive protuberance) on the center of the forehead. Male whales are larger than females whereas the average male length is about 4 m compared to about 3.6 m in females. The same trend is true for weight whereas the weight range for males runs between 1100 and 1600 kg while the weight range for females is between 700 and 1200 kg. Unlike most whales, the white whale is capable of swimming backwards.

In order to get adapted to ice condition, belugas have a dorsal ridge and not a dorsal fin. It is believed that the dorsal ridge suits under-ice conditions. Also, as in other cetaceans, the thyroid gland is relatively large compared to terrestrial mammals and this and may help to sustain higher metabolism during the summer estuarine occupations.

Distribution and habitats: Globally, white whales are found mostly in Arctic and sub-arctic waters, particularly along the coasts of Alaska, Canada, Greenland, and Russia.

There are key factors influencing the distribution of white whales especially during the ice-free months. These factors include the accessibility to food, water quality, and predator avoidance.

As expected, factors that may affect the prey populations, will ultimately affect the distribution of the whales. Such factors may include water quality, water pollution, coastal vessels, vessel traffic and others.

When the whales move away for winter, they may either stay close the edge of icepack during the winter months or they may stay under the icepack while they find patches of open water in the ice through which, the whales can surface and breathe.

Feeding habits: The white whale is a slow swimmer that feeds mainly on fish, cephalopods (squid and octopus) and crustaceans (crab and shrimp). Whales forage for food on the seabed which typically takes place at depths of up to 300 m. A typical feeding dive lasts 3–5 minutes. The primary fish prey for Belugas are eulachon and salmon especially during the seasonal salmon runs. Other fish prey includes herring, halibut, whitefish, arctic cod and several other bottom fish species. Feeding on fatty prey allows whales to build enough fat reserves to meet metabolic demands and persist through the winter when their food becomes scarce.

The nutritional status, prey abundance and fat reserves is reflected in the skin thickness of the animals whereas blubber thickness over the winter is reduced to 2-3 cm compared to about 30-cm thickness by the fall after the active feeding of whales on the abundant fish stocks throughout the spring and summer.

It worth mentioning that pregnant and/or nursing whale female would consume more prey in order to meet the increased energetic demands as required by pregnancy or lactation especially calves do not feed on fish until about 12 months of age.

References: Natural history notebook, Wikipedia, Scientific papers

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Permanent link to this article: https://fishconsult.org/?p=4992

Jul 12 2012

Rural aquaculture in Malawi (Establishment, management and impacts)

Credit: Gaves Mulaleya (Malawi)

It is estimated that there are about 4,000 small-scale fish farmers in Malawi. A typical farmer has one or two small pond and harvests about 13 kg of fish per annum. Ponds are normally constructed by family members and sometimes with help of hired labour.

The majority of farmers use maize bran as feed and green compost for pond manuring. Partial harvesting is the norm and many farmers do not harvest their ponds on an annual basis. Only 3 % of fish farmers owned a seine net.

Nevertheless, the current outputs from fish farming form an important part of household livelihoods and provide an additional option for increasing the overall value of the farming system.

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=4374

Jul 12 2012

Tilapia marketing and pricing trend in Malawi

Credit: Gaves Mulaleya (Malawi)

Tilapias are the most valuable fish species in Malawi and its price is sharply increasing with more than 30% growing rate. Fresh tilapia currently fetches up to MK 200/kg (USD 2/kg) in the city market. While, small dried fishes, such as Matemba are most popular in the villages and its prices is about one-ten of tilapia.

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=4365

Jul 12 2012

Marketing of fish landed by small-scale fishermen in Malawi

Credit: Gaves Mulaleya (Malawi)

The processing of fish by small-scale fishers in Malawi is rudimentary. The distribution and marketing of fish is complex but appears to be efficient. The bulk of the fish landed by small-scale fishermen is smoked or sun-dried as shown in the photos while the remainder of fish landed is sold in fresh style.

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=4360

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