Appraisal beaver land — water and coastal zone — was held in 1975 (890 units.) In 1976. (321 u). The results are reflected in the summary view the article numbered 3.21.
The table shows that the second site class received the vast majority (83%) of all bonitirovainyh sites, and if you select a particular type of "streams", ie, to exclude section 103, the ratio of yield classes becomes 4:87:9. On a scale V. Dyakova second site class has the largest range of scores — 8 (15 to 22), while the range of the third site class — 6 points (9 to 14), and the first — only 3 (23 25) points.
However, sections of the second group and site class is not distributed evenly on points count, and has a deviation in the "best" way, the weighted average of 20.2 points (see article at No. 3.22) instead of the average of 18.5 points, which reduces the risk of overstating the overall biotic capacity of the territory, if you apply the average index — 4 individuals in one section of the watercourse (reservoir).
Among probonitirovannyh sites unusable, ie, received at least 8 points, was not there. Since the group of streams and 10-km section of the upper reaches of the larger rivers together form 19.04 — (5014-2094-50) -0,0126,6 (thousand km), ie 76% of all streams of Latvia (see see article under the number 3.1), there are 10 900 km of waterways (without 10-km section of the upper reaches). To establish the biotic capacity of Beaver land — Key factors of the driving force that determines the increase in livestock, multiply the length of the watercourse by the appropriate factor (3 beavers to streams and 4 for other reservoirs). But in Latvia activism beavers, as we have said, does not always approved by the land users, and sometimes even the beavers into categories of pests. Therefore it is necessary to allocate another indicator — "economic optimum".
By this term we understand a number of game animals in the area, which by traditional criteria should not cause damage to other sectors of the economy. In our example, this is — the number of beavers in the lands suitable for them, which, in fact, can only be established by means of economic calculation, with the obligatory account edificator Beaver contribution to the economy of nature.
While, as stated the conflict analysis, approaches to the identification and assessment of damages are different. Objective resolution of conflicts requires further research by the three "E" ("the economy, energy, the environment"), in the specific conditions of the Latvian SSR. But the practical work can not be delayed, so you need to spend at least a preliminary analysis of the determinants and conditional to the economic optimum, ie economically acceptable number of these animals (see article at No. 3.23).
Table 4 shows the approximate number of beavers option assuming the categories of land can be considered suitable for the conduct of beaver management. One of them (125,000 beaver) reflects the capacity of the biotic area, but the latter probably is much too low, and the rate should be close to 150,000 sea otters. The fact that we did not take into account the open artificial drainage systems (a factor that increases the capacity of the biotic areas and the possibility of settlement.)
In an article to look at number 3.23, calculated as three different types of alleged economic optimum, the first of which — 30 thousand beavers — rejected by the current experience, because beavers inhabit the upper reaches of rivers and streams, and the damage is often very problematic. The second option — 54-50 thousand beavers — though not provide settlement beaver streams and drainage systems is the most realistic for a conditional economic optimum — the appropriate density will then be 78 beavers per 100 km2, or 8 Beavers on 1,000 hectares. 4th grade circles on our schematic map — is 16-20 (average — 18) settlements in 10,000 hectares.
The third option — 70000 Beaver — is less likely, because the country provides for further draining of swamps and forests, as well as the elimination of shrubs, ie, will be reduced territory beaver (extensive) farm. In this form of farming has to keep beavers from settling streams, where their habitat needs of the dam, which should catch the annual increase and immigrants.
Our goal is to organize intensive beaver management, maximizing every kind of energy flows in beaver populations. This is possible in the population beaver streams shorter 25 km, streams and even suitable drainage ditches and drainage canals. Such intensification of farming will require additional investments of labor. Materials retrospective study of population dynamics and analysis of biotic capacity of the territory confirms the need for just such a farm. They create the necessary theoretical background prediction of population dynamics and outlines the principles of just intense beaver management. The initial data for the analysis of intensive fishing for predicting population dynamics and determine the plan's receipt of products in the future will use the following: 150 000 beavers — biotic capacity of the Latvian SSR and 50,000 beavers — ce economic
optimum. Must take account of, the existing conditions and the possibility of raising this preliminary economic optimum. However, even for long-term planning of the organization beaver farm specific timber industry, a more detailed analysis of the streams, and the drainage systems are generally excluded.