58. Fresh waters have suffered the most intense intervention of all ecosystems over the past 100 years. Many fish species are now extinct, rare or endangered and many species are now protected by active management of the environment, as well as more traditional conservation methods of management, including regulation of exploitation, nature reserves, captive breeding programmes. A management plan for the conservation of Anaecypris hispanica in Portugal illustrates this approach.
59. The survival of rare sturgeons and conservation of their genetic diversity is of great economic and biological significance. Because the possibilities for management and protection of wild populations are limited, it is important to develop and implement measures for the conservation of a wide diversity of world sturgeon populations under artificial conditions.
60. Long-term ecological and physiological monitoring of sturgeon populations showed the positive role of artificial propagation, and suggests a simplified strategy aimed only at increasing the number of released juveniles. The imperfections of traditional biotechnologies considerably transform species, as well as the population structure of sturgeons.
61. Research in the Sea of Azov on seasonal regime dynamics, food sources in brackish lagoons and rearing ponds of sturgeon hatcheries, index of survival and rates of growth of various age-graded Russian sturgeon (Acipenser gueldenstaedtii) and stellate sturgeon (A. stellatus) juveniles produced by natural and artificial reproduction in different conditions resulted in a proposal for a new scheme to release juveniles to natural water bodies.
62. In the United Kingdom the bittern (Botaurus stellaris), a red data listed species with currently only around 30 booming males, is restricted to a few wet reedbeds. The favourite prey species of the bittern are eel (Anguilla anguilla) and rudd (Scardinius erythrophthalmus). The importance of fish in the bitterns diet make it imperative that the ecology of fish in wetlands is understood in order to enable habitat and fish population management to benefit the conservation of bitterns in wetlands.
63. Fish stock assessment surveys at Minsmere reedbed reserve (Suffolk, United Kingdom) revealed the dynamic nature of cyprinid fish distribution in wetlands. After reedbed rehabilitation roach (Rutilus rutilus) sometimes became the dominant species although the species has not yet been described as a food item of the bittern. Replacement of rudd by roach may reduce food availability to bitterns.
64. Implementation of the management plan for the conservation of Anaecypris hispanica in Portugal might have benefits both to fisheries and to ecosystems that include:
raising the profile of conservation issues through education and public awareness campaigns;
protection and improvement benefits to other endangered fish species;
improved ecosystem health;
reduced pressure on the ecosystem, and
improved social and economic benefits.
65. One of the most urgently needed measures for conservation of sturgeon biodiversity is the establishment and maintenance of collections of live sturgeon as gene banks. Conservation of complicated population systems requires an assessment of total genetic variability, including intraspecies variability. The adequate conservation of genetic resources according to the population structure of different species must be ensured.
66. Different release locations of sturgeon juveniles of various sizes and ages in various conditions would help maintain populations and minimize the selective consequences of artificial propagation. Migration of juvenile sturgeon to the sea in natural conditions at different ages has a deep adaptive significance and confirms the biological importance of intrapopulation differentiation. The conservation of a variety of Russian sturgeon, stellate sturgeon and giant sturgeon (Huso huso), released at different dates, permits a gradual and more rational use of food resources of brackish lagoons and marine coastal areas, compared with traditional large-scale and simultaneous standard release of juveniles into rivers.
67. Research work carried out in Minsmere reedbed reserve (United Kingdom) have identified the potential application of fish population management as a key component to the suite of tools available to enhance the conservation status of bitterns and probably that of other fish-eating birds.