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Cannibalism and its importance in Aquaculture: A review
43-54Views:628Intracohort cannibalism may lead to significant losses during the early life stages of farmed fish. The mechanisms driving cannibalism dynamics are common across many fish species and are closely linked to the factors that influence growth variation within a population. This genetically encoded behaviour allows the individual to eliminate competitors in the competition for resources and increases the chances of survival and reproduction. Many fish species display aggression towards individuals of the same species, which can often lead to cannibalistic behavior. This foraging strategy is also present in intensive aquaculture systems, and its economical, ecological and phylogenetic implications have been debated by many researchers. Many fish species can be produced economically in recirculation aquaculture (RAS) systems, but the efficiency of larval and juvenile rearing remains a bottleneck for most species. The success of initial rearing depends on many factors. In addition to genetic factors, the level of cannibalism is mainly influenced by the applied production and feeding technology. Literature suggests that mortality during larval rearing can be as high as 50%, largely due to aggression. In the case of predatory fish species, the presence or absence of certain husbandry conditions can lead to even higher levels of cannibalism, which significantly reduces production yields by causing mortality and secondary injuries, thus further decreasing the survival rate. This review therefore aims to identify and quantify the effects of biotic and abiotic factors that influence cannibalism.
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Strategic Steps in the Sheep and Goat Branches
61-68Views:422The balance of the sheep and goat branches can be summarised as follows:
If the increase in stock size, specific yields, genetic improvement and modernisation are not realised, several thousand shepherds will lose their jobs and possibilities to work, and their families will lose their only source of livelihood.
Several hundred hectares of grassland will become weedy and the costs of crop protection will increase in these regions. Pollen pollution, the number of allergic ailments and medical costs will increase, mentioning only the main disadvantages. Its financial requirement is nearly equal to the one required for development without any essential compensation or production.
In order to develop a competitive branch, a subsidisation of 10-20 billion HUF is needed until the accession of Hungary to the EU, depending on the scale and progressivity of development. The subsidisation and realisation of the strategic steps would result in:
– the establishment of a registered livestock with 1.5 million ewes, which would ensure better market position for the branch in the EU (5%),
– the establishment of a competitive and marketable branch with a production value of 15-25 billion HUF, calculated using the present price level (after accession, the branch would be self-operating and profitable, with the 6-8 billion HUF/year normative subsidisation by the EU),
– the establishment of a genetic potential which would ensure our participation in profitable international breeding animal market, which provides extra profit,
– the establishment of a sheep husbandry with better genetic potential and phenotypic performance, producing a quality of international level,
– the maintenance of the workplace of more than 10.000 people (saving 3-5 billion HUF/year of the budget),
– the maintenance of the condition of growing areas of grasslands with their advantages (crop protection and public health) whose financial effect is considerable. -
Utilization of live feeds in fish larviculture: A review
103-116Views:18This review examines the significance of live feeds in commercial aquaculture industry for production of fish and shrimp larvae, along with various challenges and prospects. Live feeds are an essential food source in larviculture, especially for marine fish, which depend on them for nutrition during the initial days of exogenous feeding. They are palatable, highly digestible, and their movement stimulates natural hunting and foraging instincts, promoting better development, lowering captivity stress, and increasing survival rates. Artemia is the most commonly used live feed in larviculture; however, it has low levels of omega-3 HUFA. Copepods are the most nutritionally rich live feed, containing high levels of DHA and EPA. Despite these benefits, they are less frequently used in larviculture due to technical challenges associated with large-scale cultivation at high densities. The use of live feed is labour-intensive and costly. The feeding period for fish larvae can be shortened using a co-feeding strategy. Microalgae rich in DHA have been utilized to enrich live feeds. Further research is needed to determine the most effective approach to significantly reduce the weaning time of fish larvae from live feed. This will lead to gradual and eventual complete replacement of life feed in the near future.