High Stocking Levels Research Articles

Mirogrex terraesanctae (Cyprinidae) of Lake Kinneret: biomass changes in relation to inflow; growth rate in relation to fish/zooplankton interaction

Catch analyses indicate increases in Mirogrex standing stock (exploited phase) from 12000 tonnes in the mid-1980's and a declining abundance after 1986. Brood strength is related to concentrations of influxed organic matter which provide larval food. Estimated von Bertalanffy growth parameters (L ∞ = 164 mm TL, K = 0.25 per yr for males; L ∞ = 198 mm, K = 0.14 for females) denote a low production/biomass ratio compared to temperate cyprinid populations, and a low rate of food consumption. From estimates of zooplankton production in recent years, an average predation of < 3 % fish weight/day is calculated. The decline in zooplankton biomass since 1970 is attributed to overgrazing by Mirogrex at high stock levels. At a lower biomass, the fish population can promote ecosystem stability. Mortality estimates from Mirogrex size distribution in a period of low exploitation were ∼ 1.5 times K-values for both males and females. Similar M/K ratios were estimated for two unexploited cyprinid stocks (Phoxinus phoxinus and Acanthobrama lissneri).

Issues in Setting up JIT Supply

Case‐based research of the early days in the establishment of a Just‐in‐Time supply contract is examined. Schedule variability was shown to be more apparent than real, although it had previously been identified as causing high stock levels and poor availability of material. Improved responsiveness by the supplier, and faster provision of accurate demand data by the customer, were shown to be key issues.

Alaska Pollack population,theragra chalcogramma, of Japan and its adjacent waters, II: Reproductive ecology and problems in population studies∗

In part I, Japanese Alaska pollack fishery and the present status of population identification of Alaska pollack were discussed. In this paper, part II, the biological characteristics of this species, including spawning, development, early stage of life, age and growth, and bait are discussed. Methods of population dynamics and present estimated stock size of each population are then dealt with. Finally, the issues of conservation and maintenance of high stock levels of Alaska pollack are addressed.

Using an Expert System to Monitor an Automatic Stock Control System

The theory of the control of stock is well understood, and a large number of firms use automatic stock control and ordering techniques as a major part of their inventory control systems. However, the effectiveness of such automatic stock control systems depends on the correct selection of system parameters for each item in the inventory and on the accurate reporting of information. It is not unusual for errors to be made in both the selection of parameters and the entry of data, and regular failures of either can cause severe problems in stock control. It is generally difficult for a human stock controller to discover errors quickly because of the large number of items that is usually found in a company inventory. This paper describes the use of an expert system to examine stock records and diagnose anomalies in the data provided or parameters applied to individual items in a stock control system. The expert system ‘reasons’ from symptoms such as reports from the forecasting system or high stock levels, to defects in the stock model used or data-collection processes, and from there to possible remedial action. Results are presented for runs of the expert system on a simulated stock control system.

Leaf area – sapwood cross-sectional area relationships in repressed stands of lodgepole pine

To better understand the phenomenon of growth "stagnation" in high-density lodgepole pine (Pinuscontorta Dougl. ex Loud.), leaf area and its relationship with sapwood cross-sectional area were examined on both an individual tree and stand basis. Leaf areas of individual trees in a 22-year-old stand varied from 30.8 m2 (dominants in stands of low stocking) to 0.05 m2 (suppressed trees in stands of high stocking). Leaf area indices ranged from 13.4 to 2.3 m2 m−2 between low and high stocking levels, respectively. Over the same stocking range, the ratio of leaf area to sapwood cross-sectional area was reduced from 0.3 to 0.15 m2 cm−2. Intraring wood density profiles showed that ovendry density increased from 0.52 to 0.7 g cm−3 and the proportion of early wood decreased over a stocking level range of 6500–109 000 trees/ha. A reduction in hydraulic conductivity in the stems of stagnant trees, suggested by the greater proportion of narrow-diameter tracheids present, may lead to a greater resistance to water transport within the boles of trees from stagnant stands, leading to low leaf areas.

Confirmation of spawning groups of Japanese jack mackerel Trachurus japonicus in the low stock level period.

Spawning groups of Japanese jack mackerel Trachurus japonicus in the low stock level period were segregated. Segregation was done by the visual examination of monthly changes of the frequency distribution of fork length and/or partly the monthly changes of the mean gonad index. In the Kuroshio Current System, two spawning groups were recognized: the spring spawning group spawns in spring mainly from February to April and distributes from southern Kyushu to Kanto region; the summer spawning group spawns in summer mainly from June to August and is present only in Kanto region. In the East China Sea and Tsushima Current System, two spawning groups are recognized: the winter spawning group spawns in winter mainly December to January and is present in Wakasa Bay and Noto regions; the spring-summer spawning group spawns from spring to summer mainly April to June and is present in northwestern Kyushu region. Comparison of the population structure of both high stock level (former studies) and low level (present study) shows that basically no differences between the two periods exist.

Relationships Between Growth Form and Stand Density in Immature Douglas-fir

Stem form of the whole tree and branching characteristics at whorls 6 to 10 were examined in 27-year-old Dougias-tir (Pseudoisuga menziesii [Mirb.] Franco) trees established at each of three spacings (1.8 × 1.8 m, 3.6 × 3.6 m, and 4.6 × 4.6 m) and replicated across two blocks. A total of 30 trees from each spacing were analysed. Spacings were found to affect stem, crown, and branching characteristics. Tree height, diameter at breast height, and stem diameter at the base of the live crown all increased significantly with spacing (p &lt; 0.01), while age and height at the base of the live crown both decreased (p &lt; 0.01). Increased spacing resulted in significantly greater branch diameters at whorls 6 to 10; and, in some whorls, an increase in branch number. Swelling of the stern at branch whorls, the number of lammas whorls, knottiness ratio, and a subjective index of stem form (higher index indicates poorer form) all increased with increased spacing (p &lt; 0.01).The considerations involved with choosing high or low initial stocking levels are discussed and the study concludes that intensive management practices such as thinning and pruning will be necessary in all regimes if clear wood is to be produced over short rotations.

FODDER CONSERVATION IN GRAZING SYSTEMS

Grazing experiments at Armidale have shown variable reiponses in sheep production to fodder conservation. (1) Responses to conservation vary with stocking rate. At low stocking levels, responses are very small. At very high stocking levels, conservation practice may result in a lower production. The greatest response occurs at an intermediate stocking rate. (2) Results depend on rainfall. (3) Wool production may be increased by conservation but reproduction and growth are much less respoilsive in the Armidale environment. These findings can be explained by a simple energy flow model. The model provides additional insights on factors such as the timing of feeding, Ihe importance of hay quality and the relatively low potential of fodder conservation for increasing meat, production.

The inter-relationships of grazing method and stocking rate in the efficiency of pasture utilization by dairy cattle

1. A large-scale grazing management study comparing rotational grazing and continuous grazing with dairy cows at two stocking rates over four complete production seasons is described.2. The four treatments were: (i) controlled grazing, light stocking rate; (ii) controlled grazing, heavy stocking rate; (iii) uncontrolled grazing, light stocking rate; (iv) uncontrolled grazing, heavy stocking rate.Each treatment involved 40 cows for a first 2-year phase and 42 cows for the following 2 years. Each herd had a normal age distribution pattern and seven 2-year-old first lactation heifers (17% of total herd) were introduced each year to maintain this pattern.3. Stocking rate was the more important factor affecting the efficiency of pasture utilization as measured by per acre output of milk and butterfat. In general, high stocking was associated with higher outputs per acre despite lower yields per animal.4. Grazing method was of less importance. In general, controlled rotational grazing was superior to uncontrolled continuous grazing, both per animal and per acre, but the average influence even of these extremes of management was only half that of stocking rate.5. Significant interactions between stocking rate and grazing method existed. Under continuous grazing a point was reached where production per acre declined to the vanishing point with increased stocking rate due to excessive depression of per cow yield: this point was not reached under rotational grazing at the same high stocking levels.6. The results suggest that optimum stocking rate under rotational grazing occurs at a level some 5–10% higher than under continuous grazing. A depression of 10–12% in per cow yield, compared with more lenient grazing, corresponds with optimum stocking level irrespective of the grazing system. This estimate is suggested as a guide line in applying the principles involved.