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The loss of multiyear sea ice (MYI) in the Arctic Ocean is a significant change that affects all facets of the Arctic environment. Using a Lagrangian ice age product, we examine MYI loss and quantify the annual MYI area budget from 1980 to 2021 as the balance of export, melt, and replenishment. Overall, MYI area declined at 72,500 km2/yr; however, a majority of the loss occurred during two stepwise reductions that interrupt an otherwise balanced budget and resulted in the northward contraction of the MYI pack. First, in 1989, a change in atmospheric forcing led to a +56% anomaly in MYI export through Fram Strait. The second occurred from 2006 to 2008 with anomalously high melt (+25%) and export (+23%) coupled with low replenishment (−8%). In terms of trends, melt has increased since 1989, particularly in the Beaufort Sea, export has decreased since 2008 due to reduced MYI coverage north of Fram Strait, and replenishment has increased over the full time series due to a negative feedback that promotes seasonal ice survival at higher latitudes exposed by MYI loss. However, retention of older MYI has significantly declined, transitioning the MYI pack toward younger MYI that is less resilient than previously anticipated and could soon elicit another stepwise reduction. We speculate that future MYI loss will be driven by increased melt and reduced replenishment, both of which are enhanced with continued warming and will one day render the Arctic Ocean free of MYI, a change that will coincide with a seasonally ice‐free Arctic Ocean. Plain Language Summary: Sea ice that has survived through at least one melt season is referred to as multiyear sea ice. It is inherently thicker, has a higher albedo and is overall more resilient to melt than seasonal sea ice. Historically, multiyear ice covered a vast majority of the Arctic Ocean, however its areal extent has declined and transitioned the Arctic ice pack to a younger state that is more susceptible to melt. To this point, the loss of multiyear ice is known, but it remains unclear whether it was a change in multiyear ice loss through export or melt or the source of multiyear through replenishment that has driven this change. By quantifying these three terms for each of the past 42 years, we find that multiyear ice loss primarily occurred through two stepwise reductions, with the budget otherwise generally being in balance. The first loss occurred in 1989 due to anomalously high export, while the second loss occurred between 2006 and 2008 through a confluence of anomalously high export and melt and low replenishment. Trends of reduced export, increased melt and increased replenishment, and overall negative multiyear ice balance, suggest the eventual disappearance of multiyear ice from the Arctic Ocean. Key Points: Multiyear sea ice (MYI) loss from the Arctic Ocean has primarily occurred through two stepwise reductions: 1989 and 2006–20081989 was the result of high MYI export, while 2006–2008 was the result of high MYI export and melt, and limited MYI replenishmentThough presently stable, reduced retention to older MYI has created a younger thinner MYI pack that may be conditioned for another reduction [ABSTRACT FROM AUTHOR]

Two outbreaks of viral haemorrhagic septicaemia (VHS) have been detected in grayling, Thymallus thymallus L., in Switzerland. The affected fry showed a septicaemic haemorrhage. Due to their similar biotopes, the susceptibility of grayling and rainbow trout to the VHS virus has been compared. The mortality rates varied between 56 and 100% depending on the age of the fish and the infection dose, but no distinct loss-associated difference occurred between grayling and rainbow trout when comparing the same age group and infection dose. Anaemia, scattered subcutaneous and intermuscular haemorrhages and enteritis were frequent macroscopic findings. The major histopathological changes included necrotic foci in the liver, spleen, intestinal mucosa and haematopoietic part of the kidney, whereas a severe tubulonephrosis was detectable in the urinary part of the kidney. [ABSTRACT FROM AUTHOR]

Mycoplasma conjunctivae was isolated four times from the eyes of nine Alpine ibex ( Capra ibex ibex) suffering from keratoconjunctivitis. The animals examined were affected in two different outbreaks in the Swiss Alps. Parasitological and bacteriological studies, including investigations for chlamydia and mycoplasmas, were performed. The results indicate that M. conjunctivae is the primary pathogenic agent causing infectious keratoconjunctivitis in this species. [ABSTRACT FROM AUTHOR]

The aim of the present study was to compare the effect of high and low doses of different vitamin C formulations on the course of ichthyophthiriosis (chthyophthirius multifiliis infection) in rainbow trout. After a depletion period, trout fingerlings were fed diets deficient in vitamin C(AA 0), or containing different levels of silicone coated ascorbic acid (AA; 50/200 mg kg feed') or ascorbyl phosphate (AP; 50/2000 mg AA equivalent kg feed"'). Fish infected with /. multifiliis demonstrated a significant reduction in mortality when fed high levels of AA or AP. A correlation between the parasite burden and the vitamin C content in the diet was not found. Specific immunity-measured as immobilization titre of sera-was not influenced by the level or the formulation of vitamin C in the diet. The most probable mechanism of high level doses of vitamin C is an increase of the general health status expressed as an improved nonspecific resistance and ability to cope with different stressors. In rainbow trout infected with /. multifiliis, the beneficial effect of ascorbyl phosphate is equal to that of silicone coated ascorbic acid, and therefore, the more stable AP may be a valuable alternative for use in fish diets. [ABSTRACT FROM AUTHOR]

Young rainbow trout were fed diets containing different combinations of ascorbyl-monophosphate (vitamin C) and all-rac-alpha-tocopheryl acetate (vitamin E) for 31 weeks. The fish fed a diet deficient in both vitamins exhibited a high mortality and were anaemic after 8–12 weeks. Histopathological examination revealed a severe muscular dystrophy and splenic haemosiderosis. Fish fed a diet deficient in vitamin C but high in vitamin E developed the typical sights of vitamin C deficiency after 16–20 weeks, including reduced growth rate, haemorrhages and gill alterations as well as severe deformations and fractures of the vertebral column. A diet deficient in vitamin E but high in vitamin C led to splenic haemosiderosis after 20 weeks. At the end of the experiment, this group showed significantly decreased haematocrit, haemoglobin content and red blood cell numbers and increased spontaneous erythrocyte haemolysis. In a second experiment, older fish of the same origin were fed diets containing high or low levels of ascorbyl-monophosphate and all-rac-alphatocopheryl acetate, respectively, for 23 weeks. The results were qualitatively the same as in the first experiment, but the onset of mortality in fish fed the diet deficient in both vitamins occurred later (weeks 18–23) and deformations of the vertebral column were absent. Haematocrit, haemoglobin content and red blood cell numbers were significantly decreased in the group fed the diet deficient in both vitamins and erythrocyte haemolysis was increased in both groups receiving a vitamin E free diet, the diet deficient in both vitamins having a more pronounced effect. The results of these two experiments indicate that there is an interrelation between vitamins C and E in rainbow trout. Possible mechanisms are discussed. [ABSTRACT FROM AUTHOR]

Several optimization procedures have been proposed for the analysis of complex water resource planning problems. One of these techniques, dynamic programming, has been limited in its applicability to river basin systems, because these systems are nonserial and dynamic programming is by nature a serial procedure. Recently developed methods are discussed and illustrated with example problems for decomposing the nonserial river basin system into equivalent serial systems amenable to analysis by the dynamic programming method. [ABSTRACT FROM AUTHOR]

BSTRACT. This paper will present a total water quality-quantity management approach which has incorporated the costs of water pollution control and water treatment, the benefits of water-based activities, and the trade-off between low flow augmentation and water quality improvement in its consideration. The analytical framework is based on the decomposition procedures provided by dynamic programming within which the optimal management plans are developed. [ABSTRACT FROM AUTHOR]

BSTRACT In water planning activities, major emphasis has been placed on the development of procedures for devising 'optimum plans.' These plans are defined as those which meet prespecified demands for water at 'minimum cost.' However, all plans are developed subject to postulated conditions regarding the state of the physical system and of nature. Because planning takes place in a dynamic and uncertain environment in which postulated conditions are known to change, it is imperative that the planner be apprised in the planning phase of the effect of changes which can occur. Using 'this information, a planner can temper his judgment with a knowledge of the effect of the uncertainty resulting from changes in the system state variables. This paper presents results of the use of a computer simulation and optimization model to quantify possible variations in system response which could occur as a result of uncertainty in the postulated physical and economic conditions under which the proposed water development system was to perform. The possible effects of these variable responses on planning decision-making is discussed. [ABSTRACT FROM AUTHOR]

We appreciate the interest shown in our paper [Meier and Beightler, 1967] by Brater in his comment. Brater raises two significant and valid points concerning the paper. First and foremost, there is a numerical error in the authors' paper, as indicated in a previous reply [Meier and Beightler, 1968]. The correct values of d1 and d2 in Equation 16 of the authors' paper should be 7.11 and 2.11, respectively. Furthermore, the total maximum return is slightly greater than 355. These are typographical errors and were not occasioned through the use of the particular optimization method employed. [ABSTRACT FROM AUTHOR]

The authors wish to express their appreciation to Loucks [1968] for his constructive criticism of their recent paper [Meier and Beightler, 1967]. Loucks' comment correctly interprets the authors' enthusiasm for dynamic programming and its usefulness in water resource analysis. The authors believe that dynamic programming has an important role to play in the analysis of the large-scale system planning problems occurring in the water resources area. [ABSTRACT FROM AUTHOR]

Water pollution induces pathological changes in fish. As an indicator of exposure to contaminants, histology represents a useful tool to assess the degree of pollution, particularly for sub-lethal and chronic effects. However, a standardized method for the description and assessment of histological changes, mainly for use in freshwater fish, is still lacking. In this paper, the present authors propose a standardized tool for the assessment of histological findings which can be applied to different organs. The methodology is based on two factors: (1) the extension of a pathological change is rated with a ‘score value’; and (2) the pathological importance of this alteration is defined as an ‘importance factor’. The sum of the multiplied score values and importance factors of all diagnosed changes results in different indices. With these indices, statistical analysis can be carried out. Assessment methods for the gills, liver, kidney and skin are described. [ABSTRACT FROM AUTHOR]