5 Responses to “Aquaculture Predator Control”

1. Innocent
   October 16th, 2008 at 2:50 pm

   Other methods that may be adopted toward predator control include the use of anti-predator nets and acoustic scarers. Killing of predators is another measure which is regarded as the last resort when attacks by predators are too aggresive and persistent.

2. g.reutens
   October 17th, 2008 at 10:32 am

   An alternative method to control predators could include chemical repellents. Researchers at the Oak Ridge Shark Laboratory have been investigating effective chemicals to be used in repellents since 2001. In doing so, the identification and employment of semiochemicals in shark repellents became evident.

   Semiochemicals are chemical compounds that carry or facilitate communication between members or non-members of particular species. Functionally, semiochemicals serve a wide range of activities including acting as attractants or repellents (i.e. pheromones), stimulating or inhibiting feeding activities, and provoking or inhibiting the fight or flight response, to name a few. Semiochemicals are emitted by a range of animals or plants, and the manipulation of this technology is currently employed as a range of animal or insect controls (such as insect repellents).

   Currently, field research has demonstrated effective repellant abilities with six shark species. Upon repellant delivery to feeding sharks at Gruber’s Bimini Biological Field Station, feeding ceased and a behavioural change was induced which resulted in sharks leaving the feeding area or submerging deeper within the waters. Furthermore, the semiochemicals have demonstrated nontoxic effects to the shark hosts.

   At this stage the results look promising however further studies are needed to prove the efficacy and efficiency of the technology.

   Please refer to the following link for further information.
   http://news.nationalgeographic.co.in/news/2004/07/0729_040729_sharkrepellent.html

3. Maadhu
   October 26th, 2008 at 8:49 pm

   Aquaculture Predatory control can also mean protecting against sharks, as well as birds, as many a times farmed fish and cultured fish are hamred excessively through birds acting as predators. Birds, fish and mammals are known predators of cultured fish. Bird predation is the major source of fish loss at aquaculture facilities. Predatory fish can also be a major concern to fish stocks, followed by mammal predation to a much lesser extent.
   Bird predation at aquaculture facilities can have a significant economic impact on operations. Besides consuming fish, birds can injure fish, disrupt their feeding activity, disturb broodstock and contribute to the spread of diseases and parasites in aquaculture ponds. Open water and high fish stocking densities at aquaculture facilities are natural attractants to many bird species.

   When controlling bird predators, take action in early spring, before feeding habits or nearby nesting sites have been established. Prompt action will encourage the birds to seek nesting habitat elsewhere. Cultured fish can be more or less susceptible to bird predation depending on the physical location, design and construction of an aquaculture facility. Facility location, design and construction
   • locating aquaculture sites near known bird migratory routes or flyways will mean more visits and/or predation
   • when aquaculture facilities are located in isolated areas, heavy losses of fish can result when birds have easy access to fry and fingerlings
   • man-made and natural objects, such as fences, telephone and light poles or vegetation, provide attractive perching, hiding, nesting and hunting structures for bird predators. Try to reduce the number of these structures around the aquaculture facility
   • increasing the pond’s shore water depth to a minimum of 1 m and steepening embankments will decrease predatory birds’ ability to feed
   Stocking
   • stock ponds or raceways with larger fingerlings. This approach will decrease predation levels because larger fish are usually less vulnerable to predation
   • reducing the number of fish in a structure may reduce its attractiveness to bird predation, as birds prefer densely stocked ponds.
   • when stocking ponds, release fingerlings at several locations in open water, which will decrease the chance of fingerling mortality due to weed entanglement and/or bird predation
   • the use of stocking cages for up to two weeks can help prevent fish mortality caused by weeds, predatory birds and toxic bottom water
   • fish that feed at the water’s surface are more susceptible to predation; avoid floating feed if possible
   • stocking at dusk provides a greater opportunity for fish to adapt to new surroundings.

4. Maadhu
   October 26th, 2008 at 8:51 pm

   More information on my last comment could be found at http://www1.agric.gov.ab.ca/department/deptdocs.nsf/all/agdex821

5. budijus
   October 28th, 2008 at 1:04 pm

   Sharks are known to have a very sensitive electrical receptor to sense their preys [1]. There is a network of nerves called ‘Ampullae of Lorenzini’ in the head of a shark, which detect the very weak electromagnetic fields given off by all living things [2].

   Therefore, by generating electomagentic field, we could confused sharks by creating disturbances in the ampullae of lorenzini.

   There is one company that offer electrical shark repellent called SharkPOD (Protective Oceanic Device).

   http://www.shark.co.za/repel.htm

   Some patents on electric shark repellent:

   a. http://www.freepatentsonline.com/7233829.html
   b. http://www.wipo.org/pctdb/en/wo.jsp?wo=2005085064
   c. http://www.freepatentsonline.com/7302905.html
   d. http://www.freepatentsonline.com/7412944.html

   reference:
   [1] http://www.sciam.com/article.cfm?id=the-sharks-electric-sense

   [2] http://en.wikipedia.org/wiki/Ampullae_of_Lorenzini

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