A review on broodstock nutrition of marine pelagic spawners: the curious case of the freshwater eels (Anguilla spp.)

To sustain eel aquaculture, development of reproduction in captivity is vital. The aim of this review is to assess our current knowledge on the nutrition of broodstock eels in order to improve the quality of broodstock under farming conditions, drawing information from wild adult eels and other marine pelagic spawners. Freshwater eels spawn marine pelagic eggs with an oil droplet (type II), and with a large perivitelline space. Compared with other marine fish eggs, eel eggs are at the extreme end of the spectrum in terms of egg composition, even within this type II group. Eel eggs contain a large amount of total lipids, and a shortage of neutral lipids has been implied a cause for reduced survival of larvae. Eel eggs have higher ARA but lower EPA and DHA levels than in other fish. Too high levels of ARA negatively affected reproduction in the Japanese eel, although high levels of 18:2n-6 in the eggs of farmed eels were not detrimental. The total free amino acid amount and profile of eel eggs appears much different from other marine pelagic spawners. Nutritional intervention to influence egg composition seems feasible, but responsiveness of farmed eels to induced maturation might also require environmental manipulation. The challenge remains to succeed in raising European eel broodstock with formulated feeds and to enable the procurement of viable eggs and larvae, once adequate protocols for induced maturation have been developed

Assessment methodology of an optimal plan for forest felling

This article discusses the method of estimating the optimal plan for felling. The paper deals with the following objectives: to study the nature of influence of the productivity of pine tree stands on the felling age (according to the ripeness of economic forests), the calculation of the average increase in the value of wood in accordance with the current forest fees as well as the defi ning the age at which most cost-effective cutting of stands is achieved. When optimizing the size of the main use it is necessary to distin-guish two problems which, because of their relationship and influence on each other, must be addressed comprehensively: the establishment of the optimum cutting age, based on the theory of ripeness of the forest, and the determination of the annual allowable cut, taking into account the age structure of forests. Methods of assessing the losses from the delays in the felling may be used in the calculation of the objective functions based on this value, and to compare different options for the design of the main forest use. The indicators of growth of the pine stands: Bagi nsky normal stands, Baginsky modal stands, Zagreyev, Miroshnikov, Yurkevich and the tables of growth of economic forests have been taken as the test data