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• 9

  Dec
  Effect of population density on platy fish (Xiphophorus maculates)

  Aquaculture

  by Nitzan Hevlin

  20
  תחום או ענף דגים
  תאריך עדכון 14/3/2012

  Effect of population density on platy fish (Xiphophorus maculates)
  Nitzan Reiss Hevlin, Tal Gur, Moti Userovich and Dan Popper - Central and Northern Arava R&D
  E-mail address for correspondence: nitzanr@arava.co.il

  Abstract
  Platyfish (Xiphophorus maculates) are a popular species for home aquariums; these social animals live in schools and are pretty. They are omnivorous and give birth to live young. On farms, the faster the fish grow, the more crowded they get and the lower the costs to the grower — and the greater his profit margin. The process of ramping up production requires a significant increase in the number of fish per unit volume. There is a delicate balance between increased density, which allows for maximal use of the area, and preserving the health of the fish and their growth rate. Density is a source of chronic stress that is expressed in different ways depending on the type of fish, their age and their gender.
  In an experiment conducted at the Yair Research Station during 2010/11, we evaluated the effect of the density of fish in an aquarium on their growth rate and survival. We did not find any difference in the growth of the fish at different population densities. However, we did see a difference in the survival rate at a density of one fish per liter as compared to 2.5 fish per liter.

  שפה English
  מלות מפתח Ornamental fish, water quality
  מחבר Nitzan Reiss Hevlin, Tal Gur, Moti Userovich, Dan Popper
  שנה 2011
  שייכות yzvieli
  תאריך יצירה 14/3/2012
  תאריך עדכון 14/3/2012
• 9

  Dec
  Use of concentrated brine for raising clownfish (Amphiprion ocellaris)

  Aquaculture

  by Nitzan Hevlin

  19
  תחום או ענף דגים
  תאריך עדכון 14/3/2012

  Use of concentrated brine for raising clownfish (Amphiprion ocellaris)
  Nitzan Reiss Hevlin, Dan Popper, Tal Gur, Moti Userovitch – Central and Northern Arava R&D
  E-mail address for correspondence: nitzanr@arava.co.il

  Abstract
  The market for ornamental saltwater fish has developed greatly in recent years and the demand for fish raised in captivity has increased. Clownfish (Amphiprion) are in great demand in the European market, where they are sold as ornamental fish for reef aquariums. They are valued for their pretty form and bold color, as well as their ability to live together with invertebrates in an aquarium. In recent years at the Yair Experimental Station of the Arava R&D Authority, a protocol has been developed for breeding and raising eight species of clownfish, including the most popular species, A. ocellaris. Currently, researchers at the Arava R&D Authority are focused on improving growth and breeding, adding new species to the set of saltwater fish currently raised in the region and reducing production costs. The main cost associated with raising saltwater ornamental fish in artificial environments is the cost of the water in which the fish are kept. Seven large desalination installations are currently used in the Arava to provide drinking water for local residents. Large amounts of brine flow from each of these installations to the sewer system. This brine is a byproduct of the desalination process and contains salt concentrations that are twice that of the local pipeline water. A previous study conducted at the Yair Experimental Station in 2010 examined the growth rate and survival of young clownfish raised in brine that was supplemented with sea salt as compared with those of fish raised in desalinated water or pipeline water supplemented with sea salt. There was no difference between the health and growth rate of the fish in the different treatments.
  In the experiment on which we are currently reporting, which was conducted in 2011, we evaluated the growth rate and survival of clownfish raised in brine concentrated to a salinity level of 0.25 ppt. We did not notice any difference in the growth of the fish, but there was a significant difference in terms of survival.
  Histological examination of the gills of these fish did not reveal any significant pathology in any of the treatment groups. The only difference between the groups was the form and quantity of chlorine cells.

  Acknowledgements
  We thank the JCA Charitable Foundation for their financial support for this research. Thank you to Prof. Shanan Herpaz and Dr. Avner Canaani for their help planning the study. Thank you to Dr. Dina Zilberg, Dr. Gilat Sharon and Tamar Sini for examining the fish after the experiment. We thank the Arava staff of Mekorot, especially Yuval Plaout and Yoav Moyal for their cooperation, patience and generous assistance. We thank the staff of the Hetzva Field School for their understanding and patience.

  שפה English
  מחבר Nitzan Reiss Hevlin, Dan Popper, Tal Gur, Moti Userovitch
  שנה 2011
  שייכות yzvieli
  תאריך יצירה 14/3/2012
  תאריך עדכון 14/3/2012
• 9

  Dec
  Enriching feed for molly fish (Poecilia velifera) with pigments

  Aquaculture

  by Nitzan Hevlin

  18
  תחום או ענף דגים
  תאריך עדכון 14/3/2012

  Enriching feed for molly fish (Poecilia velifera) with pigments
  Nitzan Reiss Hevlin, Tal Gur, Moti Userovich and Dan Popper – Central and Northern Arava R&D
  E-mail address for correspondence: nitzanr@arava.co.il

  Abstract
  The color of fish has a determinative effect on their beauty and how in demand they are in the market. A diet that includes pigments affects the color of the fish. In nature, the fish acquire pigments from the algae and aquatic microorganisms that they eat, but in closed systems used for breeding ornamental fish, it is customary to add coloring agents to the feed. In a series of experiments carried out at the Yair Experimental Station during 2011, we evaluated different types of coloring agents, both natural and synthetic, to determine which should be added to the fish feed. In a previous experiment in which coloring agents were added to the feed of molly fish (Poecilia velifera), good results were obtained from three different coloring agents: Haematococcus pluvialis, Capsantal and carophyll pink. Of these, we included the latter two in a further experiment that also included three types of feed. We found that for gold and orange mollies, the coloring agent Capsantal and BioMar feed provide the best results.

  שפה English
  מחבר Nitzan Reiss Hevlin, Tal Gur, Moti Userovich, Dan Popper
  שנה 2011
  שייכות yzvieli
  תאריך יצירה 14/3/2012
  תאריך עדכון 14/3/2012
• 9

  Dec
  Feeding experiment in Corydoras aeneus fish

  Aquaculture

  by Nitzan Hevlin

  17
  תחום או ענף דגים
  תאריך עדכון 14/3/2012

  Feeding experiment in Corydoras aeneus fish
  Nitzan Reiss Hevlin, Tal Gur, Moti Userovich and Dan Popper – Central and Northern Arava R&D
  Email: nitzanr@arava.co.il

  Abstract
  Corydoras fish are members of the Family Callichthyidae that are native to South American rivers (in Argentina, Colombia and Venezuela). They are found near the bottom of these rivers, close to the ground. In nature, these fish live in streams and creeks in which the water is clear and flows slowly. Corydoras fish are omnivores and, in the wild, feed on insect larvae, worms and the remains of plants, which they find on the river bottom. They also eat the corpses of other fish. In home aquariums, Corydoras are used as cleaner fish and are responsible for removing uneaten feed and the remains of other fish. When Corydoras fish are raised in closed systems in which water is recycled, the type of feed used is very important.
  We evaluated the effects of different types of feed on the growth (weight and length) and survival of the Corydoras species Corydoras paleatus. In an experiment that was conducted at the Yair Experimental Station in 2010, we tested four types of feed. We found that MEM feed gave the best results in terms of the growth and uniformity of the fish (with an average fish weighing 0.558 g as compared to 0.446-0.434 g for the fish in the other treatments). The addition of algae to the aquarium improved the growth results in all of the feed treatments, except for the MEM treatment, in which the growth results were good even without the addition of any algae.

  שפה English
  מלות מפתח Keywords: Fish food, fish nutrition, ornamental fish, catfish
  מחבר Nitzan Reiss Hevlin, Tal Gur, Moti Userovich, Dan Popper
  שנה 2011
  שייכות yzvieli
  תאריך יצירה 14/3/2012
  תאריך עדכון 14/3/2012